Trailer Tire Load Range and Axle Capacity

US & Canada

Load range is a strength grade, not a weight. The weight is the max load on the sidewall, and the tires on each axle must add up to at least that axle's GAWR. A 7,000 lb tandem trailer puts about 1,575 lb on each tire.

Your trailer and its tires

1. The trailer

Trailer weight (GVWR, or weighed loaded)

GVWR is on the trailer's certification label. A scale ticket for the loaded trailer is better still.

Tongue weight

% of trailer

The share riding on the hitch, not the tires. 10 to 15% is manufacturer guidance for a ball hitch. The low end is the cautious choice here, because it leaves more on the tires.

Tires on the axles

Do not count the spare.

2. From the tire sidewall

Max load (single)

Printed as "Max load ... at ... psi cold". If it gives single and dual, use single.

Tire type

The letters in front of the size, as in ST205/75R15.

The max load only applies at the pressure printed beside it. A tire run below that pressure carries less.

Result

How the load reaches each tire

An even split across the tires. Real trailers rarely load evenly side to side or axle to axle, so size the tires for the heaviest wheel position and weigh the trailer if the margin is thin. The 20% reserve is Carlisle's guidance, not law.

How to calculate trailer tire load capacity

Weight on the tires = trailer weight − tongue weight. The tongue rides on the hitch.
Load per tire = weight on the tires ÷ number of tires (spare not counted).
Compare with the "max load" on the sidewall. A passenger tire counts at that figure ÷ 1.10.
Reserve: all the tires together ≥ trailer weight × 1.2. That last step is Carlisle's guidance, not law.

Subtracting the tongue is the same accounting the regulation uses for RV trailers. 49 CFR 571.110, S9.2: "On RV trailers, the sum of the GAWRs of all axles on the vehicle plus the vehicle manufacturer's recommended tongue weight must not be less than the GVWR." Use the trailer's GVWR unless you have weighed it loaded. For the tongue, Chevrolet, 2026 Trailering Guide, p. 8 gives 10 to 15% of trailer weight for a ball hitch, which is manufacturer guidance. The low end is the cautious choice for a tire check, because it leaves more weight on the tires.

Worked example

A 7,000 lb (3,175 kg) tandem axle trailer, 10% on the tongue, on four ST205/75R15 load range D tires rated 2,150 lb at 65 psi (CarlStar):

Tire load check for a 7,000 lb tandem trailer, computed by the calculator above
Tongue at 10%	700 lb (318 kg)
On the four tires	6,300 lb (2,858 kg)
Per tire	1,575 lb (714 kg)
Margin per tire	575 lb (261 kg) (27%)
All four tires	8,600 lb (3,901 kg)
Trailer plus 20% (guidance)	8,400 lb (3,810 kg)

It passes both. The same trailer on load range C (1,820 lb) is still under the rating at 1,575 lb a tire, but four of them make 7,280 lb, short of the 8,400 lb reserve. On a single axle the same trailer puts 3,150 lb on each tire, 320 lb over even a ST225/75R15 load range E at 2,830 lb.

The split is never perfectly even. Dexter: "If the load is not equal on all tires due to trailer weight distribution, use the tire rated for the heaviest wheel position." Side to side and axle to axle loads differ, so if the margin is thin, weigh each axle at a public scale. And Titan Specialty Division (Carlisle and CarlStar trailer tires) puts the ceiling plainly: "Never exceed the maximum load rating stamped on the tire sidewall or the maximum vehicle load rating, whichever is less."

What is trailer tire load range?

The load range is a letter that grades the tire's construction strength. It replaced the old ply count, so it is still read as a ply rating: a "10 ply" tire is load range E, whether or not it has ten plies inside. 49 CFR 571.119, S6.5(d), (e) and (j) requires the letter on the sidewall of an ST tire, beside the max load and its cold pressure. The letter does not give a weight on its own: an E on a 15 inch tire and an E on a 16 inch tire carry different loads.

Trailer tire load range chart: letter, ply rating and the pressure for that range in one ST radial line
Load range	Ply rating	Max load, CarlStar Radial Trail HD sizes	Pressure in that line
B	4 ply	not in this line	n/a
C	6 ply	1,360 to 1,870 lb	50 psi
D	8 ply	1,220 to 2,540 lb	65 psi
E	10 ply	1,520 to 4,080 lb	80 psi
F	12 ply	3,740 to 3,960 lb	95 psi
G	14 ply	not in this line	n/a
H	16 ply	not in this line	n/a

Ply ratings from General Tire, 2019 Truck Tire Data Guide, p. 29, load range designation and ply rating equivalency table, which continues past H to J (18), L (20), M (22) and N (24); I and K are not used. Titan Specialty Division (Carlisle and CarlStar trailer tires) gives the same B to E equivalents for its trailer tires. The load and pressure columns are one maker's current line, CarlStar, Radial Trail HD specialty trailer tire, size table, so they show the spread by size, not a rule: CarlStar's small bias sizes need different pressures for the same letter, for example 50 psi for a 20.5x8.0-10 C and 90 psi for an E.

Letters past G are not exotic. 49 CFR 571.119, Table II grades strength from A through N, and the J to N ranges are commercial truck tires. The C1, D1 and E1 suffixes some retailers list are not in the federal standard or the ply table we read, so this page does not define them; read the max load on the sidewall instead.

Trailer tire weight capacity by size and load range

Rated load per tire, single, from CarlStar, Radial Trail HD specialty trailer tire, size table. Kilograms are converted from CarlStar's pounds. Another brand's tire of the same size and load range is close to these but not always identical; your own sidewall is the number that counts.

ST radial trailer tire capacity by size and load range, CarlStar Radial Trail HD
Size	Load range	Max load per tire	Four tires	At	Rated speed
ST145/R12	D (8 ply)	1,220 lb 553 kg	4,880 lb	65 psi	75 mph
ST145/R12	E (10 ply)	1,520 lb 689 kg	6,080 lb	80 psi	75 mph
ST175/80R13	C (6 ply)	1,360 lb 617 kg	5,440 lb	50 psi	81 mph
ST175/80R13	D (8 ply)	1,570 lb 712 kg	6,280 lb	65 psi	81 mph
ST185/80R13	C (6 ply)	1,480 lb 671 kg	5,920 lb	50 psi	81 mph
ST185/80R13	D (8 ply)	1,710 lb 776 kg	6,840 lb	65 psi	81 mph
ST205/75R14	C (6 ply)	1,760 lb 798 kg	7,040 lb	50 psi	81 mph
ST205/75R14	D (8 ply)	2,040 lb 925 kg	8,160 lb	65 psi	81 mph
ST215/75R14	C (6 ply)	1,870 lb 848 kg	7,480 lb	50 psi	81 mph
ST205/75R15	C (6 ply)	1,820 lb 826 kg	7,280 lb	50 psi	81 mph
ST205/75R15	D (8 ply)	2,150 lb 975 kg	8,600 lb	65 psi	81 mph
ST225/75R15	D (8 ply)	2,540 lb 1,152 kg	10,160 lb	65 psi	81 mph
ST225/75R15	E (10 ply)	2,830 lb 1,284 kg	11,320 lb	80 psi	81 mph
ST235/80R16	E (10 ply)	3,520 lb 1,597 kg	14,080 lb	80 psi	75 mph
ST235/80R16	F (12 ply)	3,740 lb 1,696 kg	14,960 lb	95 psi	81 mph
ST235/85R16	E (10 ply)	3,640 lb 1,651 kg	14,560 lb	80 psi	75 mph
ST235/85R16	F (12 ply)	3,960 lb 1,796 kg	15,840 lb	95 psi	75 mph
ST255/85R16	E (10 ply)	4,080 lb 1,851 kg	16,320 lb	80 psi	87 mph

Same size, same load range, another maker

Two tires with the same size and letter are not always rated the same. An ST205/75R14 load range C is 1,760 lb at 50 psi from CarlStar and 1,925 lb at 60 psi from Kenda; an ST225/75R15 E is 2,830 lb from CarlStar and 2,860 lb from Kenda. That is why the calculator asks for the number on your sidewall, not the letter. From Kenda, Karrier KR03 ST radial trailer tire, technical specifications, which prints the ply rating rather than the letter and gives a dual rating as well:

Kenda Karrier KR03 ST radial: single and dual max load by size and ply rating
Size	Ply rating (load range)	Max load, single	Max load, dual	At
ST175/80R13	6 ply (C)	1,375 lb (624 kg)	1,230 lb (558 kg)	50 psi
ST175/80R13	8 ply (D)	1,650 lb (748 kg)	1,430 lb (649 kg)	70 psi
ST185/80R13	6 ply (C)	1,480 lb (671 kg)	1,280 lb (581 kg)	50 psi
ST185/80R13	8 ply (D)	1,710 lb (776 kg)	1,520 lb (689 kg)	65 psi
ST205/75R14	6 ply (C)	1,925 lb (873 kg)	1,710 lb (776 kg)	60 psi
ST205/75R14	8 ply (D)	2,200 lb (998 kg)	1,930 lb (875 kg)	75 psi
ST215/75R14	6 ply (C)	1,870 lb (848 kg)	1,650 lb (748 kg)	50 psi
ST205/75R15	6 ply (C)	1,820 lb (826 kg)	1,610 lb (730 kg)	50 psi
ST205/75R15	8 ply (D)	2,200 lb (998 kg)	1,930 lb (875 kg)	65 psi
ST225/75R15	6 ply (C)	2,150 lb (975 kg)	1,870 lb (848 kg)	50 psi
ST225/75R15	8 ply (D)	2,540 lb (1,152 kg)	2,200 lb (998 kg)	65 psi
ST225/75R15	10 ply (E)	2,860 lb (1,297 kg)	2,470 lb (1,120 kg)	80 psi
ST235/80R16	8 ply (D)	3,000 lb (1,361 kg)	2,600 lb (1,179 kg)	65 psi
ST235/80R16	10 ply (E)	3,500 lb (1,588 kg)	3,197 lb (1,450 kg)	90 psi

Small bias trailer tires, 8 and 10 inch (CarlStar Sport Trail)

Bias trailer tire capacity by size and load range, CarlStar, Sport Trail specialty trailer tire, size table
Size	Load range	Max load per tire	At	Rated speed
4.80-8	B	585 lb (265 kg)	60 psi	62 mph
4.80-8	C	760 lb (345 kg)	90 psi	62 mph
5.70-8	B	715 lb (324 kg)	50 psi	62 mph
5.70-8	C	910 lb (413 kg)	75 psi	62 mph
5.70-8	D	1,070 lb (485 kg)	100 psi	62 mph
16.5x6.5-8	D	910 lb (413 kg)	90 psi	62 mph
18.5x8.5-8	B	760 lb (345 kg)	35 psi	62 mph
18.5x8.5-8	C	935 lb (424 kg)	50 psi	75 mph
20.5x8.0-10	C	1,100 lb (499 kg)	50 psi	62 mph
20.5x8.0-10	D	1,320 lb (599 kg)	70 psi	62 mph
20.5x8.0-10	E	1,520 lb (689 kg)	90 psi	81 mph
20.5x8.0-10	F	1,650 lb (748 kg)	105 psi	62 mph

Sizes such as 4.80-12, 5.30-12 and ST145/R12 bias are common on small utility trailers but are not in the CarlStar tables we read, so they are not listed. Their max load is printed on the sidewall.

Trailer tire load index chart

Many trailer tires print a load index after the size, and when there are two, such as 120/116, they are single then dual. The index stands for a maximum load. Kilograms are the defining unit, from Goodyear Commercial (Central America and Caribbean), Load Index Chart; the pounds are our conversion, rounded to the pound, so they can differ by a few pounds from a chart that rounds to 5.

Load index 80 to 100
Index	kg	lb
80	450	992
81	462	1,019
82	475	1,047
83	487	1,074
84	500	1,102
85	515	1,135
86	530	1,168
87	545	1,202
88	560	1,235
89	580	1,279
90	600	1,323
91	615	1,356
92	630	1,389
93	650	1,433
94	670	1,477
95	690	1,521
96	710	1,565
97	730	1,609
98	750	1,653
99	775	1,709
100	800	1,764

Load index 101 to 120
Index	kg	lb
101	825	1,819
102	850	1,874
103	875	1,929
104	900	1,984
105	925	2,039
106	950	2,094
107	975	2,150
108	1,000	2,205
109	1,030	2,271
110	1,060	2,337
111	1,090	2,403
112	1,120	2,469
113	1,150	2,535
114	1,180	2,601
115	1,215	2,679
116	1,250	2,756
117	1,285	2,833
118	1,320	2,910
119	1,360	2,998
120	1,400	3,086

Load index 121 to 140
Index	kg	lb
121	1,450	3,197
122	1,500	3,307
123	1,550	3,417
124	1,600	3,527
125	1,650	3,638
126	1,700	3,748
127	1,750	3,858
128	1,800	3,968
129	1,850	4,079
130	1,900	4,189
131	1,950	4,299
132	2,000	4,409
133	2,060	4,542
134	2,120	4,674
135	2,180	4,806
136	2,240	4,938
137	2,300	5,071
138	2,360	5,203
139	2,430	5,357
140	2,500	5,512

Single vs dual load rating

49 CFR 571.119, S6.5(d), (e) and (j) sets the sidewall wording: "Max load single ____kg (____lb) at ____kPa (____psi) cold. Max load dual ____kg (____lb) at ____kPa (____psi) cold." The dual rating applies when two tires share one hub, side by side, and it is lower per tire. Goodyear, Tire Load Index & Chart (light truck load index): "For example, a light truck tire with a load index of 120/116 means a load capacity for a single tire of 3,086 pounds and a load capacity of 2,756 pounds for two tires." A tandem axle trailer is not "dual": each tire runs single, on its own hub, so use the single figure.

What the law says: tires against the axle rating

This is the legal floor, and it is per axle, not per trailer:

US, trailers at 10,000 lb GVWR or less. 49 CFR 571.110, S4.2.2.1: "Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label required by 49 CFR part 567."
Passenger tires on a trailer. 49 CFR 571.110, S4.2.2.2: "When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle."
US, trailers over 10,000 lb GVWR. 49 CFR 571.120, S5.1.2 sets the same rule: "Except in the case of a vehicle which has a speed attainable in 2 miles of 50 mph or less, the sum of the maximum load ratings of the tires fitted to an axle shall be not less than the gross axle weight rating (GAWR) of the axle system as specified on the vehicle's certification label required by 49 CFR part 567."
Canada. Transport Canada, Technical Standards Document No. 110, Revision 2, S4.2.2.1 (CMVSS 110): "Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle’s compliance label required by section 6 of the Motor Vehicle Safety Regulations (MVSR)" Canada applies the same per-axle tire rule to trailers at 4,536 kg GVWR or less, including the divide-by-1.10 for passenger car tires (S4.2.2.2). Revision 2 took effect May 1, 2026, with compliance mandatory from November 1, 2026. The quote leaves out the struck-out FMVSS wording ("certification", "49 CFR part 567") that the TSD prints but says is not to be read as part of it.

The GAWR is on the trailer's certification label (in Canada also marked PNBE), and 49 CFR 571.110, S4.3.3 puts the tire size, rim and cold pressure right after it. 49 CFR 571.3, Definitions defines GAWR as "Gross axle weight rating or GAWR means the value specified by the vehicle manufacturer as the load-carrying capacity of a single axle system, as measured at the tire-ground interfaces." A tire with more capacity than the label calls for is allowed, but it does not raise the GAWR or the GVWR.

Trailer axle capacity and the tires it needs

An axle's capacity is a rating, the GAWR, set by the trailer maker for the whole axle system: axle beam, springs, hubs, wheels and tires. The tires are only one part. What the law fixes is that the tires on an axle add up to at least its GAWR, so each of two tires must carry at least half of it. The capacities below are the light trailer axle ratings in Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Bearing Replacement Chart.

Trailer axle capacity chart: minimum tire rating and load index for a single axle with two tires
Axle GAWR	Each of 2 tires, at least	Lowest load index
2,000 lb (907 kg)	1,000 lb (454 kg)	81 (462 kg)
2,800 lb (1,270 kg)	1,400 lb (635 kg)	93 (650 kg)
3,000 lb (1,361 kg)	1,500 lb (680 kg)	95 (690 kg)
3,500 lb (1,588 kg)	1,750 lb (794 kg)	100 (800 kg)
4,400 lb (1,996 kg)	2,200 lb (998 kg)	108 (1,000 kg)
5,200 lb (2,359 kg)	2,600 lb (1,179 kg)	114 (1,180 kg)
6,000 lb (2,722 kg)	3,000 lb (1,361 kg)	120 (1,400 kg)
7,000 lb (3,175 kg)	3,500 lb (1,588 kg)	124 (1,600 kg)
7,200 lb (3,266 kg)	3,600 lb (1,633 kg)	125 (1,650 kg)
8,000 lb (3,629 kg)	4,000 lb (1,814 kg)	129 (1,850 kg)

Arithmetic from 49 CFR 571.110, S4.2.2.1 and the load index table above. It is the legal minimum, not a recommendation: Carlisle's 20% reserve guidance is measured against the loaded trailer, and the calculator applies it.

Trailer axle weight distribution. On a tandem the two axles do not always share the load equally: how the trailer sits on the hitch and where the load is placed change the split. The tongue weight is the part that never reaches the trailer axles at all. To know what each axle actually carries, weigh the trailer at a public scale, one axle per platform.

ST vs LT vs passenger tires on a trailer

ST (special trailer). 49 CFR 571.110, S4.1(b)(2): "Trailers may be equipped with ST tires, FI tires, or tires with a rim diameter code of 12 or below that meet the requirements of § 571.119." Counted at the rating molded into the tire.
LT (light truck). Also counted at the molded rating. Dexter says so for LT and ST alike.
P (passenger), SL or XL. Allowed, but counted at the rating ÷ 1.10 by law (49 CFR 571.110, S4.2.2.2), and Dexter applies the same: "Passenger Car Tires. Use the capacity rating molded into the tire sidewall divided by 1.10 for trailer use."

Guidance, not law. The tire maker's view, from Carlisle, Trailer Tires: Tips & Best Practices (the ST difference): "ST tires generally offer approximately 10% percent more load capacity than a similar LT tire and nearly 40% more than a P passenger tire." And from Titan Specialty Division (Carlisle and CarlStar trailer tires): "Passenger or truck tires, with their more flexible sidewalls, can result in trailer sway problems." That is why ST is the usual choice on a trailer, and why an ST tire should not go on the truck.

Trailer tire speed rating

The speed symbol after the load index is the tire's rated speed at its rated load. Toyo Tires, Speed Symbol and Load Index: "The Speed Symbol indicates the speed at which the tire can carry a load corresponding to its Load Index under service conditions specified by the tire manufacturer." A load range letter has no speed rating of its own. 49 CFR 571.119 requires a "Max speed" marking on tires restricted to 55 mph or less.

Tire speed rating chart for the symbols trailer tires carry
Symbol	km/h	mph
F	80	50
G	90	55
J	100	62
K	110	68
L	120	75
M	130	81
N	140	87
P	150	93
Q	160	99
R	170	106

Guidance, not law. Titan Specialty Division (Carlisle and CarlStar trailer tires): "If the tire is not marked with a speed symbol, the default speed rating for trailer tires is 62 mph." Carlisle adds: "Best practice. Do not exceed 60 mph while towing a trailer." The rating is the tire's limit, not a towing speed, and posted limits apply either way.

Trailer tire pressure

A tire's max load and its pressure are one pair. 49 CFR 571.139, S3, Definitions: "Maximum load rating means the load rating for a tire at the maximum permissible inflation pressure for that tire." Below that pressure the tire carries less, and an underinflated trailer tire runs hot. Three places give a pressure:

The sidewall: the cold pressure that goes with the max load, for example 80 psi for 2,830 lb on an ST225/75R15 E.
The trailer's label: the pressure the trailer maker chose for its GAWR (49 CFR 571.110, S4.3.3). Trailers at 10,000 lb GVWR or less also carry a tire placard (49 CFR 571.110, S4.3.5).
The wheel: Dexter: "DO NOT EXCEED MAXIMUM INFLATION PRESSURES FOR RIMS OR WHEELS." Moving up a load range can need more pressure than an old wheel is rated for.

Guidance, not law. Titan Specialty Division (Carlisle and CarlStar trailer tires): "Always maintain air pressure at the maximum PSI recommended on the tire sidewall." Check cold, before you drive and out of the sun. Dexter: "Pressure should be checked cold before operation. Do not bleed air from tires when they are hot." A tire pressure monitoring system that reads the trailer's tires is a useful warning on the road, not a replacement for a cold check with a gauge. Whether your truck can read trailer sensors, Ford, GMC and Ram included, depends on the model and package; the owner's manual says.

How to read a trailer tire size

In the tire maker's own example, ST175/80D13C: ST special trailer, 175 mm wide, 80 the sidewall height as a percentage of the width, D bias (R is radial), 13 inch rim, C load range. The sidewall also carries the max load and pressure, the ply composition and the DOT code, whose last four digits are the date. Titan Specialty Division (Carlisle and CarlStar trailer tires): "The first two numbers indicate the week (out of 52) and the last two digits indicate the year."

Why trailer tires cup and wear unevenly

Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Tire Wear Diagnostic Chart:

Trailer tire wear patterns and causes, Dexter
Wear	Cause	Action
Cupping	Out of balance	Check bearing adjustment and balance the tires
Center wear	Over inflation	Set pressure for the load
Edge wear	Under inflation	Set pressure for the load
Side wear	Loss of camber or overloading	Keep the load within the axle rating; alignment shop
Toe wear	Incorrect toe-in	Alignment shop
Flat spots	Wheel lockup and skidding	Avoid sudden stops; adjust the brakes

Trailer wheel lug nut torque

From Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Wheel Torque Requirements, in ft-lb, tightened in three stages in a star pattern. "Check and re-torque after the first 10 miles, 25 miles, and again at 50 miles." Your wheel maker's figure takes precedence; aluminum and steel wheels can differ.

Trailer wheel torque by wheel and stud size, Dexter
Wheel	Stud	1st stage	2nd stage	Final
12" (440 or 545 BC)	1/2"-20	20 to 25	35 to 40	60 to 75
13" (440 or 545 BC)	1/2"-20	20 to 25	35 to 40	60 to 75
14" (545 BC)	1/2"-20	20 to 25	50 to 60	100 to 120
15" (545 or 655 BC)	1/2"-20	20 to 25	50 to 60	100 to 120
16" (655 BC)	1/2"-20	20 to 25	50 to 60	100 to 120
16" (865 BC)	9/16"-18	20 to 25	50 to 60	140 to 170
16.5" (655 BC)	1/2"-20	20 to 25	50 to 60	100 to 120
16.5" (865 BC)	9/16"-18	20 to 25	50 to 60	140 to 170

How long trailer tires last

Guidance, not law. Carlisle, Trailer Tires: Tips & Best Practices: "3 to 5 years is the average life expectancy of a trailer tire, regardless of mileage." A trailer tire often ages out before it wears out, because it sits loaded between trips. Titan Specialty Division (Carlisle and CarlStar trailer tires) adds that remaining tread is not an indicator of tire life. If one tire fails on a tandem, Carlisle says to replace both on that side.

Sources

49 CFR 571.110, S4.2.2.1: On a trailer at 10,000 lb GVWR or less, the tires on each axle must add up to at least that axle's GAWR. This is the legal floor for tire capacity, and it is per axle. Checked 2026-10-24.
49 CFR 571.110, S4.2.2.2: A passenger (P-metric) tire on a trailer counts at its sidewall rating divided by 1.10. ST and LT tires are not derated by this rule. Checked 2026-10-24.
49 CFR 571.110, S4.1(b)(2): ST (special trailer) tires are a trailer-only allowance: the light vehicle standard lets trailers, and only trailers, run them. Checked 2026-10-24.
49 CFR 571.120, S5.1.2: The same per-axle rule for trailers over 10,000 lb GVWR, with the same divide-by-1.10 for passenger car tires. Checked 2026-10-24.
Transport Canada, Technical Standards Document No. 110, Revision 2, S4.2.2.1 (CMVSS 110): Canada applies the same per-axle tire rule to trailers at 4,536 kg GVWR or less, including the divide-by-1.10 for passenger car tires (S4.2.2.2). Revision 2 took effect May 1, 2026, with compliance mandatory from November 1, 2026. The quote leaves out the struck-out FMVSS wording ("certification", "49 CFR part 567") that the TSD prints but says is not to be read as part of it. Checked 2026-10-24.
49 CFR 571.119, S6.5(d), (e) and (j): An ST tire's sidewall must state its maximum load and the cold pressure that goes with it (single and dual where it is rated for both), the letter designating its load range, and a maximum speed if the tire is restricted to 90 km/h (55 mph) or less. Standard 119 covers tires for special-use trailers (ST, FI and 12 inch rim or smaller). Checked 2026-10-24.
49 CFR 571.119, Table II: The strength table in the federal tire standard runs through load ranges A to H for light truck sizes and on to J, L, M and N for larger truck tires, so letters past G are real ranges, mostly on commercial truck tires. Checked 2026-10-24.
49 CFR 571.139, S3, Definitions: A tire's printed max load only holds at its maximum pressure. The same section defines load rating as the load a tire is rated to carry "for a given inflation pressure", so less air means less capacity. Checked 2026-10-24.
49 CFR 571.139, S3, Definitions: SL (standard load) and XL (extra load) are passenger tire designations, not trailer load ranges. Checked 2026-10-24.
49 CFR 571.110, S9.2: On an RV trailer the axles and the recommended tongue weight together must cover the GVWR. If tongue weight is given as a range, the minimum is used. Checked 2026-10-24.
49 CFR 571.110, S4.3.3: On trucks, SUVs, vans and trailers the tire size, rim size and cold pressure are printed after each GAWR on the certification label, so each axle rating is tied to a tire. Checked 2026-10-24.
49 CFR 571.110, S4.3.5: A trailer at 10,000 lb GVWR or less carries a tire placard next to its certification label, with a cargo capacity statement in place of the occupants and cargo statement. On an RV trailer full propane tanks count in the unloaded weight and on-board water counts as cargo. Checked 2026-10-24.
49 CFR 571.3, Definitions: GAWR is per axle, measured at the tires, so it can be exceeded even when GVWR is not. Checked 2026-10-23.
General Tire, 2019 Truck Tire Data Guide, p. 29, load range designation and ply rating equivalency table: Load range A is 2 ply rating, B 4, C 6, D 8, E 10, F 12, G 14, H 16, J 18, L 20, M 22 and N 24. The letters I and K are not used. Checked 2026-10-24.
Titan Specialty Division (Carlisle and CarlStar trailer tires), FAQ: trailer tire sidewall specifications: A trailer tire maker's own statement of the B to E ply equivalents, read off an example sidewall, ST175/80D13C, where D means bias construction and the final C is the load range. Checked 2026-10-24.
CarlStar, Radial Trail HD specialty trailer tire, size table: Rated load, pressure and rated speed for one current line of ST radial tires from ST145/R12 to ST255/85R16, in load ranges C to F. Imperial columns used; kilograms on this site are converted from them. Checked 2026-10-24.
Kenda, Karrier KR03 ST radial trailer tire, technical specifications: Ply rating, single and dual max load and pressure for Kenda's Karrier ST radial from ST175/80R13 to ST235/80R16. The same size and ply rating can carry a different load at a different pressure than another maker's tire. Checked 2026-10-24.
CarlStar, Sport Trail specialty trailer tire, size table: Rated load, pressure and rated speed for small bias trailer sizes, 4.80-8 to 20.5x8.0-10, in load ranges B to F. Imperial columns used. Checked 2026-10-24.
Goodyear Commercial (Central America and Caribbean), Load Index Chart: Load index to maximum load in kilograms, indexes 80 to 199. This site uses indexes 80 to 140 and converts to pounds itself, because kilograms are the defining unit and a published pound table we checked had transcription errors. Checked 2026-10-24.
Goodyear, Tire Load Index & Chart (light truck load index): Two load indexes on a sidewall are single and dual. The dual figure is lower per tire, and it is the one that applies to tires mounted in pairs on one hub. Checked 2026-10-24.
Toyo Tires, Speed Symbol and Load Index: Speed symbol letters with their speeds in km/h and mph, for example J 100 km/h (62 mph), L 120 (75), M 130 (81) and N 140 (87). Checked 2026-10-24.
Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Tires: The axle maker's rule for which rating to use on a trailer: LT and ST tires at the capacity molded into the tire, passenger tires at that figure divided by 1.10. Checked 2026-10-24.
Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Tires: An even split is a starting point. Size the tires for the most heavily loaded wheel, not the average. Checked 2026-10-24.
Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Wheels and Tires: Wheels have their own load and pressure ratings, and they must match the tire's maximum load. A higher load range tire can need more pressure than the wheel allows. Checked 2026-10-24.
Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Tire Wear Diagnostic Chart: Wear pattern to cause: center wear is over inflation, edge wear under inflation, side wear loss of camber or overloading, toe wear incorrect toe-in, cupping out of balance (check bearing adjustment and balance the tires), flat spots wheel lockup and skidding. Checked 2026-10-24.
Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Wheel Torque Requirements: Wheel nut torque in three stages by wheel size and stud size, for example 60 to 75 ft-lb final on 12 and 13 inch wheels with 1/2 inch studs and 100 to 120 ft-lb on 14 to 16 inch wheels with 1/2 inch studs. Checked 2026-10-24.
Dexter, Operation Maintenance Service Manual, 600 to 8,000 lb axles, Bearing Replacement Chart: Light trailer axle capacities Dexter lists in that chart: 2,000, 2,800, 3,000, 3,500, 4,400, 5,200, 6,000, 7,000, 7,200 and 8,000 lb. Checked 2026-10-24.
Titan Specialty Division (Carlisle and CarlStar trailer tires), FAQ: what is the proper tire inflation? (guidance, not law): The tire maker's advice is to run ST tires at the maximum pressure on the sidewall, checked cold and in the shade. Checked 2026-10-24.
Titan Specialty Division (Carlisle and CarlStar trailer tires), FAQ: how fast can I travel? (guidance, not law): With no speed symbol on the sidewall, this maker treats a trailer tire as rated for 62 mph. Checked 2026-10-24.
Titan Specialty Division (Carlisle and CarlStar trailer tires), FAQ: what does "ST" mean? (guidance, not law): ST stands for Special Trailer. The maker's case for ST over P and LT on a trailer is the stiffer sidewall and the trailer duty cycle. Checked 2026-10-24.
Titan Specialty Division (Carlisle and CarlStar trailer tires), FAQ: should I choose 8 ply over 6 ply tires?: The binding limit is the lower of the tire rating and the trailer's own rating, so bigger tires do not raise the trailer's GVWR. Checked 2026-10-24.
Titan Specialty Division (Carlisle and CarlStar trailer tires), FAQ: how do I determine the age of my trailer tires?: The four-digit date code at the end of the DOT number is week then year, and the maker adds that remaining tread is not an indicator of tire life. Checked 2026-10-24.
Carlisle, Trailer Tires: Tips & Best Practices (load limits) (guidance, not law): A 20 percent reserve over the whole loaded trailer weight is the tire maker's recommendation. It is guidance, not law; the legal floor is the per-axle rule. Checked 2026-10-24.
Carlisle, Trailer Tires: Tips & Best Practices (inflation and replacement) (guidance, not law): The same document's best-practice list says to replace trailer tires every three to five years. Checked 2026-10-24.
Carlisle, Trailer Tires: Tips & Best Practices (best practices) (guidance, not law): 60 mph is the tire maker's towing advice, separate from any tire's speed rating and from posted limits. Checked 2026-10-24.
Carlisle, Trailer Tires: Tips & Best Practices (the ST difference) (guidance, not law): The maker's comparison of ST, LT and P tires of similar size. The same document says to replace both tires on a side after a blowout on a tandem axle, and that a larger diameter tire may change tongue height. Checked 2026-10-24.
Chevrolet, 2026 Trailering Guide, p. 8 (guidance, not law): 10 to 15 percent of loaded trailer weight for a conventional ball hitch, and 15 to 25 percent for gooseneck and fifth wheel. The same page adds that when towing the maximum trailer weight, the maximum tongue weight is 10% for conventional trailers. Checked 2026-10-24.

Loads per tire, margins, four-tire totals, the axle table and every pound figure converted from kilograms (and kilogram figure converted from pounds) are calculated on this page from the sources above. Tire makers revise their tables; the sidewall of the tire on your trailer is the final word.

Common questions

What is trailer tire load range?

A letter on the sidewall that grades how strong the tire is built and how much air it can take. It is the old ply count in letter form: General Tire, 2019 Truck Tire Data Guide, p. 29, load range designation and ply rating equivalency table lists B as 4 ply rating, C as 6, D as 8, E as 10, F as 12 and G as 14. The letter alone does not give a weight: the max load printed beside it does, and it depends on the size too.

What is load range C on a trailer tire?

A 6 ply rating. In CarlStar's Radial Trail HD line, load range C runs 1,360 to 1,870 lb depending on size, at 50 psi, for example 1,760 lb for an ST205/75R14 C.

What is load range D on a trailer tire?

An 8 ply rating. In the same CarlStar line, load range D runs 1,220 to 2,540 lb by size, at 65 psi: 2,150 lb for an ST205/75R15 D and 2,540 lb for an ST225/75R15 D.

What is load range E on a trailer tire?

A 10 ply rating. Load range E in the CarlStar line runs 1,520 to 4,080 lb, at 80 psi: 2,830 lb for an ST225/75R15 E and 3,520 lb for an ST235/80R16 E.

What is load range B on a trailer tire?

A 4 ply rating, mostly on small bias tires. CarlStar's Sport Trail lists load range B on its 8 inch sizes at 585 to 760 lb. In CarlStar's Radial Trail HD line, the radial sizes start at C.

Trailer tire load range C vs D: what is the difference?

On the same size, D is built for more pressure and carries more. An ST205/75R14 goes from 1,760 lb at 50 psi as a C to 2,040 lb at 65 psi as a D, 280 lb more per tire, in CarlStar's table. The extra capacity is only there if you run the extra pressure, and the wheel has to be rated for it.

Trailer tire load range D vs E: what is the difference?

An ST225/75R15 goes from 2,540 lb at 65 psi as a D to 2,830 lb at 80 psi as an E in CarlStar's table: 290 lb more per tire, 1,160 lb more across four tires. It does not raise the trailer's GVWR or GAWR.

Load range E vs F?

F is a 12 ply rating against E's 10. On an ST235/85R16 CarlStar lists 3,640 lb at 80 psi for the E and 3,960 lb at 95 psi for the F. On an ST235/80R16, 3,520 lb against 3,740 lb.

How do I calculate trailer tire load capacity?

Take the trailer weight, subtract the tongue weight (it rides on the hitch), and divide by the number of tires. Compare that with the max load on the sidewall. A 7,000 lb (3,175 kg) trailer with 10% on the tongue puts 6,300 lb on the tires, 1,575 lb each on a tandem axle. Carlisle also recommends that all the tires together exceed the loaded trailer weight by 20%.

What load range trailer tire do I need?

The one whose max load covers your heaviest wheel, on the size your trailer's label calls for. Use the calculator: it gives the load per tire, the per-tire rating that meets the 20% reserve, and the lowest load index that covers it. There is no single right letter for a boat, horse, utility or travel trailer; it follows from the weight.

What size trailer tires do I need?

The size printed on the trailer itself. 49 CFR 571.110, S4.3.3 requires the tire size, rim size and cold pressure after each GAWR on the certification label, and trailers at 10,000 lb GVWR or less also carry a tire placard. Going to a different size means checking the wheel, the fender clearance and the tongue height, which Carlisle notes can change with a larger diameter.

What size trailer tires for highway use?

The size on the label, in a radial ST tire whose speed symbol covers the speeds you tow at. The CarlStar radials on this page are rated 75 to 87 mph by size, while the small bias sizes are mostly 62 mph. Carlisle's own advice is not to exceed 60 mph when towing, whatever the rating.

Can I put LT tires on a trailer?

Yes. Dexter says to use the capacity molded into the tire for LT and ST tires alike. Carlisle says ST tires generally carry about 10 percent more than a similar LT tire. Passenger tires are the ones the law derates: 49 CFR 571.110, S4.2.2.2 divides their rating by 1.10 on a trailer.

ST vs LT tires: what is the difference?

ST means Special Trailer. 49 CFR 571.110, S4.1(b)(2) allows ST tires on trailers only. Makers build them with stiffer sidewalls for trailer loads; Carlisle says an ST tire generally carries about 10 percent more than a similar LT tire and nearly 40 percent more than a passenger tire. LT tires are designated by their makers for light trucks and multipurpose vehicles.

What is the difference between LT and passenger tires?

LT tires carry a load range letter and are built for heavier loads and higher pressure. Passenger tires are SL (standard load) or XL (extra load), and 49 CFR 571.139, S3, Definitions defines extra load as built to "operate at higher loads and higher inflation pressure than the corresponding standard tire". On a trailer a passenger tire counts at its rating divided by 1.10.

What is tire load range SL on trailer tires?

SL is standard load, a passenger tire designation, not a trailer load range. If a trailer is on SL tires, 49 CFR 571.110, S4.2.2.2 counts each one at its sidewall rating divided by 1.10. Pick "P" in the calculator to apply that.

What speed are trailer tires rated for?

Whatever the speed symbol on the sidewall says. J is 62 mph, L 75 mph, M 81 mph and N 87 mph (Toyo Tires, Speed Symbol and Load Index). With no symbol, the maker of Carlisle trailer tires treats one as rated for 62 mph. A load range letter carries no speed rating of its own: in CarlStar's table, load range D tires are rated 75 or 81 mph depending on size.

What pressure should trailer tires be?

The tire's max load only applies at the pressure printed beside it: 49 CFR 571.139, S3, Definitions: "Maximum load rating means the load rating for a tire at the maximum permissible inflation pressure for that tire." The trailer's label gives the pressure its maker chose. The tire maker Carlisle's advice is to run ST tires at the maximum sidewall pressure, checked cold. Never exceed the wheel's own pressure rating.

What does single and dual mean on a trailer tire?

Two ratings for the same tire: one when it runs alone on a hub, one when it is paired with another. The dual figure is lower per tire. Goodyear's example: "For example, a light truck tire with a load index of 120/116 means a load capacity for a single tire of 3,086 pounds and a load capacity of 2,756 pounds for two tires." A trailer with one tire at each wheel position runs them single.

What causes trailer tires to cup?

Dexter's tire wear chart puts cupping down to an out of balance assembly, and says to check bearing adjustment and balance the tires. The same chart lists center wear as over inflation, edge wear as under inflation, side wear as loss of camber or overloading, and flat spots as wheel lockup.

What is the lug nut torque for trailer wheels?

It depends on wheel and stud size. Dexter lists 60 to 75 ft-lb final for 12 and 13 inch wheels on 1/2 inch studs, 100 to 120 ft-lb for 14 to 16 inch wheels on 1/2 inch studs, and 140 to 170 ft-lb for 9/16 inch studs, tightened in three stages, then rechecked at 10, 25 and 50 miles. Your wheel maker's figure comes first.

How long do trailer tires last?

Carlisle puts the average at 3 to 5 years regardless of mileage, and recommends replacing them in that window. Read the age from the last four digits of the DOT code: week, then year, so 3409 is the 34th week of 2009.

What is the highest load range for a trailer tire?

The letters run from A to N, 2 to 24 ply rating (General Tire, 2019 Truck Tire Data Guide, p. 29, load range designation and ply rating equivalency table), and the federal tire standard's strength table goes to N on large truck tires. On the ST sizes in this page's table the top is F, 12 ply rating, and the standard grades light truck sizes up to H. Higher is not automatically better: it needs more pressure and a wheel rated for it.

What does the tire load index mean on a trailer tire?

A number that stands for the tire's maximum load: index 117 is 1,285 kg (2,833 lb), for example. A tire can print both a load range letter and a load index; two indexes, like the 120/116 in Goodyear's example, are single and dual. The full table is on this page.