R1S 22” Tire Load Index??

[SANZC02]

Yes, all you have to do is use 94% of max load which is 48 psi (2590#) which gives you an axle load of 5180#. For an SL tire need to de-rate 10% first, so 115 SL drops to 2411, 94% is 2266, axle max load of 4532, which is 418# too low…

All this to say if not using the vehicle to tow/extreme high load traveling at high speed/temps…then 115 should be fine and not need to be derated…

Where are you seeing information about de-rating the load rating? My understanding was SL tires all have lower max air pressures and anything that can go past 36 PSI is not an SL tire. I’m always interested in learning new stuff so if you can provide a link for what you are referring to so I can read up on it it would be appreciated.

TIRE LOAD RANGE CHART (PLY RATING)

Load Range	Ply Rating	Max Load Carrying Air Pressure
SL	4	36 PSI
XL	4	42 PSI
C1	6	50 PSI
C2	6	35 PSI
D1	8	65 PSI
D2	8	50 PSI
E1	10	80 PSI
E2	10	65 PSI
F1	12	95 PSI
G	14	110 PSI

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[ksurfier]

Where are you seeing information about de-rating the load rating? My understanding was SL tires all have lower max air pressures and anything that can go past 36 PSI is not an SL tire. I’m always interested in learning new stuff so if you can provide a link for what you are referring to so I can read up on it it would be appreciated.

TIRE LOAD RANGE CHART (PLY RATING)

Load Range	Ply Rating	Max Load Carrying Air Pressure
SL	4	36 PSI
XL	4	42 PSI
C1	6	50 PSI
C2	6	35 PSI
D1	8	65 PSI
D2	8	50 PSI
E1	10	80 PSI
E2	10	65 PSI
F1	12	95 PSI
G	14	110 PSI

49 CFR § 571.110

https://www.law.cornell.edu/cfr/text/49/571.110

“S4.2.2.3 (a) For vehicles, except trailerswith no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire”

 

[SANZC02]

49 CFR § 571.110

https://www.law.cornell.edu/cfr/text/49/571.110

“S4.2.2.3 (a) For vehicles, except trailerswith no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire”

Thanks, appreciate the link, it was a good read.

Looks like where Rivian bumped it up to 116 from 115 is S4.2.2.2, the rear GAWR on the R1S is 4960, if you divide the 2679 pounds by 1.1 and multiply by 2 it is 4870 pounds so 90 pounds short of the max rear axle rating.

Under S4.2.2.3 94% of the load is still over 10k pounds (10,073) so for me and my use I would have no concerns using 115 rated tires.

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.

S4.2.2.3 (a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

 

[Riviot]

Just a couple weeks ago tried to get a set of Mickey Thompson baja Boss A/T 115's purchased/installed at Discount Tire at Beaverton Oregon 185th store. They said no it required the much heavier LT version.. Called Micky Thompson tech line. They said no problem at all, 115's are well within spec for the R1S. So went through private installer 503 Tires, mobile install. Remy got the tires, they all come out of the same warehouse, and did an excellent job mounting and the balance is absolutely perfect.

Hopefully Discount Tire gets their act together; loosing business. I've purchased many, many sets of tires from them over the last 5 years.

In addition bought new rims, Atomic Wheels AW01's. Now have rugged looking set up and saved 11 lbs per corner, coming from 22's.

@Discount Tire FYI here, I had same experience last summer at Bremerton, WA, location. I was told 115 SL is insufficient on the ordered 20" tire, despite the location selling 115 SL on a different 22" tire. It's either 115 on all or on none, I respect the none but the partial is frustrating.

49 CFR § 571.110

I love me a good 49 CFR check in the morning!

 

[ksurfier]

@Discount Tire FYI here, I had same experience last summer at Bremerton, WA, location. I was told 115 SL is insufficient on the ordered 20" tire, despite the location selling 115 SL on a different 22" tire. It's either 115 on all or on none, I respect the none but the partial is frustrating.



I love me a good 49 CFR check in the morning!

Found this: “If you apply a passenger type tire to something other than a passenger car (this means an SUV, Light Truck, Multi-purpose vehicle or trailer) you MUST de-rate the load capacity by dividing by 1.10”.

4.2.1.1 - Max load - 58% (rear wt) X 8532 = 4949/2 = 2475 (113 LI or higher).

4.2.1.2 - Normal load (68 kilo X 7 plus curb wt) = 2.21x68x7 + 6900 = 7952 X 58% (rear wt) = 4612/2= 2306…
A 115 tire at 48 psi has a load of 2679, 94% of that is 2518, so 212 # higher than needed.

4.2.2.2 - Max derated load - 115 (2679/1.1=2435) - 40# below. 116 (2756/1.1=2505) - 30# above.

4.2.2.3 - Derated normal load (need >2305). 116 derated -2505 x 94% = 2355 (49 # above). 115 derated -2435 X 94% = 2289 (17 # below).

so remove 80# from your max payload and all is good…or just run a D or E rated LT tire…

 

[Riviot]

so remove 80# from your max payload and all is good…or just run a D or E rated LT tire…

 

[usofrob]

Thanks, appreciate the link, it was a good read.

Looks like where Rivian bumped it up to 116 from 115 is S4.2.2.2, the rear GAWR on the R1S is 4960, if you divide the 2679 pounds by 1.1 and multiply by 2 it is 4870 pounds so 90 pounds short of the max rear axle rating.

Under S4.2.2.3 94% of the load is still over 10k pounds (10,073) so for me and my use I would have no concerns using 115 rated tires.

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.

S4.2.2.3 (a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

I'm very confused by this. Is it saying you divide by 1.1, then multiply by .94 to get the approved rating? Wouldn't that mean that the 116 load index is too low?

 

[SANZC02]

I'm very confused by this. Is it saying you divide by 1.1, then multiply by .94 to get the approved rating? Wouldn't that mean that the 116 load index is too low?

I read it as 2 different formulas. One to calculate for max load, the other to calculate for standard load.

 

[usofrob]

I read it as 2 different formulas. One to calculate for max load, the other to calculate for standard load.

So, the 94% is only for SL tires?
And the /1.1 is for both SL and XL?

 

[ksurfier]

So, the 94% is only for SL tires?
And the /1.1 is for both SL and XL?

My understanding is passenger tires include both SL and XL, so both get derated 9%.
LT (light truck) tires do not get derated 9% but still must carry a normal load no greater than 94% (2,306# for R1S and 2,075# for R1T) .

Maximum load (if SL or XL)
So for the R1S with 58% weight on rear axle, the following SL/XL tire load needs to be met:
4,949#/2 = 2,475#
Additional reduction of 9% = 2723#
116 Load rated to 2,756#; derated 9%: 2,508# is sufficient for Max load

Normal load
The normal load is 7 x 150# occupants plus curb weight of 6900#:
7,950# (7x150 + 6900); 58% = 4611#/2 = 2,306#
Additional reduction of 9% = 2537#; then 94% of derated load is a tire needs to be rated at least 2,699# (116 and above).

The R1T on the other hand has no problem with 115 rating...likely the cause of all the confusion to begin with....

If the max load for a R1S is reduced from 8532# to 8450# then a 115 tire is fine...
If the normal load for a R1S is also reduced to 8490#, then a 115 tire is also fine....

 

[usofrob]

My understanding is passenger tires include both SL and XL, so both get derated 9%.
LT (light truck) tires do not get derated 9% but still must carry a normal load no greater than 94% (2,306# for R1S and 2,075# for R1T) .

Maximum load (if SL or XL)
So for the R1S with 58% weight on rear axle, the following SL/XL tire load needs to be met:
4,949#/2 = 2,475#
Additional reduction of 9% = 2723#
116 Load rated to 2,756#; derated 9%: 2,508# is sufficient for Max load

Normal load
The normal load is 7 x 150# occupants plus curb weight of 6900#:
7,950# (7x150 + 6900); 58% = 4611#/2 = 2,306#
Additional reduction of 9% = 2537#; then 94% of derated load is a tire needs to be rated at least 2,699# (116 and above).

The R1T on the other hand has no problem with 115 rating...likely the cause of all the confusion to begin with....

If the max load for a R1S is reduced from 8532# to 8450# then a 115 tire is fine...
If the normal load for a R1S is also reduced to 8490#, then a 115 tire is also fine....

Thanks for the detailed reply. It took a while to mostly understand your numbers.

I'm not sure what standard this is for, but to calculate the normal load, you use Table 1 that says 3 passengers for a 7 passenger vehicle:

Designated seating capacity, number of occupants	Vehicle normal load, number of occupants	Occupant distribution in a normally loaded vehicle
2 through 4	2	2 in front.
5 through 10	3	2 in front, 1 in second seat.

Also, I'm not sure the weight distribution is 58% rear. That's the max weight on the rear if the vehicle is loaded to the max. If the front axle is maxed out, the rear can only take 4398#. 51.5% on the rear. I don't see anything about passengers weighing 150# either.

In fact, the R1T "truck is well-balanced with a 51/49 front-rear weight distribution" : https://www.motortrend.com/reviews/2022-rivian-r1t-electric-pickup-truck-second-drive-review/
R1S looks like "

CURB WEIGHT (F/R DIST)

7,068 lb (48/52%), 7,091 lb (48/52%)

" : https://www.motortrend.com/reviews/2022-rivian-r1s-first-test-review/

I had never heard of the normal load before. I wonder if that's because it's never high enough to become more limiting than the load index for max load.

 

[Mtnrivian]

Update….even though discount tire would not install the Michelin Ice X 115’s I brought them last fall due to load rating. They took them off and installed Continental Contacts 115’s just yesterday that I bought from them, no questions asked.

 

[ksurfier]

This is an older discussion on the great 115/116 debate. I would not run 115 load tires since there are so many other 116+ options, but it’s certainly possible if you find a shop that doesn’t check.

 

[Whale Blubber]

Thanks for that read. I found a shop that was fine installing a set of Michelin Defender LTX M/S2 in 275/50 R22 XL 115 today. All I know thus far is they look good, and the ride feels appreciably better than the old scorpions. Will be observing the efficiency closely but expect it should be the same.

 

[dmc94]

My understanding is passenger tires include both SL and XL, so both get derated 9%.
LT (light truck) tires do not get derated 9% but still must carry a normal load no greater than 94% (2,306# for R1S and 2,075# for R1T) .

Maximum load (if SL or XL)
So for the R1S with 58% weight on rear axle, the following SL/XL tire load needs to be met:
4,949#/2 = 2,475#
Additional reduction of 9% = 2723#
116 Load rated to 2,756#; derated 9%: 2,508# is sufficient for Max load

Normal load
The normal load is 7 x 150# occupants plus curb weight of 6900#:
7,950# (7x150 + 6900); 58% = 4611#/2 = 2,306#
Additional reduction of 9% = 2537#; then 94% of derated load is a tire needs to be rated at least 2,699# (116 and above).

The R1T on the other hand has no problem with 115 rating...likely the cause of all the confusion to begin with....

If the max load for a R1S is reduced from 8532# to 8450# then a 115 tire is fine...
If the normal load for a R1S is also reduced to 8490#, then a 115 tire is also fine....

Where did you read the derating by 9% requirement? Rivian shipped with 115s so this would imply they need to issue a recall and replace with 116s.

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