How important is tire load rating on a B8.5 Allroad?

[eljay]

Is it OK to use 19" tires with a load rating of 96 on an Allroad?
The manual says:
245/45R18 100H (all season)
245/45R18 96Y (high performance)
245/40R19 98Y XL (high performance)

So, if I want to put 255/35R19 summer performance tires on my Allroad, are 96 load rating tires OK? I was looking at Firestone Indy 500 255/35R19 96W XL, but came across a deal on Toyo Proxes T1 Sport 255/35R19 96Y XL.

I see a few folks running 255/35R19 tires and I cannot imagine they are all 98+ rated.

[MacFady]

I see a few folks running 255/35R19 tires and I cannot imagine they are all 98+ rated.

Likely true. I ran tires a few numbers lower than the recommended on my Avant and ended up eventually with a sidewall bubble and then a blow out. Not saying that is why, but having said that I personally would just gauge the cost savings with what the road conditions are like that you're driving on and then use your best judgement. They do have quite a bit less sidewall than the 245/45's though.

[87vr6]

You need to fully understand what you're looking at and asking for. Your tires load ratings are for GVWR. This is the total COMBINED weight of your vehicle+passengers+any cargo.

If you have 100 on there now, you could have a GVWR of 7056
98= 6612
96=6260

That's a substantial drop in capacity. This is what you need to take into consideration. Seeing as your car weighs 3891 (give or take), will you ever exceed 2369lbs of load in the car? If not, then 96 rated tires are fine.

https://www.tirerack.com/tires/tiret....jsp?techid=35

[eljay]

You need to fully understand what you're looking at and asking for. Your tires load ratings are for GVWR. This is the total COMBINED weight of your vehicle+passengers+any cargo.

If you have 100 on there now, you could have a GVWR of 7056
98= 6612
96=6260

That's a substantial drop in capacity. This is what you need to take into consideration. Seeing as your car weighs 3891 (give or take), will you ever exceed 2369lbs of load in the car? If not, then 96 rated tires are fine.

https://www.tirerack.com/tires/tiret....jsp?techid=35

Good point!
This car will rarely, if ever, be fully loaded with 5 people and their luggage and roof box.

That said, I just realize that 255/40R19 is a better tire size than 255/35R19. The 35 profile seems more popular from the posts I've read. Don't know why. I guess people prefer the lower profile sidewall look despite the smaller overall look of the tire. On top of that, I easily can find 255/40R19 with 100 load rating. The Indy 500 is available in 255/40ZR19 XL - 100W and Toyo Proxes Sport are 255/40ZR19XL 100Y.
So, sticking with OE spec tire size also means that the load rating corresponds better.
Again, I may not need the weight capacity, but the stiffer sidewall may provide for a crisper turn-in, which I prefer and the sidewall is 4mm higher on the 255/40R19 rather than being 9mm smaller on the 255/35R19 vs OE spec.

At the end of the day, I may just stick with 245 wide tires and not worry about any of the above.

[eljay]

Likely true. I ran tires a few numbers lower than the recommended on my Avant and ended up eventually with a sidewall bubble and then a blow out. Not saying that is why, but having said that I personally would just gauge the cost savings with what the road conditions are like that you're driving on and then use your best judgement. They do have quite a bit less sidewall than the 245/45's though.

Yes, around the Maritimes, some potholes would take out a tire easily, so perhaps I'll stick with 245/40R19 or go with taller sidewall and 255/40R19.

[Smac770]

Lot of material involved in that subject. So load index. First thing you must note is are you talking about a P-metric or ISO-metric rated tire. The load capacity table is different for P-metric vs ISO-metric tires. P-metric tires have the P at the start of the sizing; ISO-metric do not. Additionally, the weight value for a given load index varies with tire size in P-metric; not so for ISO-metric. Here we're dealing with ISO-metric tires.

Second, understand SL (standard load) vs XL (extended load). When you don't see any term, it implies SL. SL tires are rated for load capacity at 36 psi. You can inflate beyond that, such as for driving faster than 99mph (up to V) or faster than 118mph (W, Y, Z). Or if you just want to max some fuel economy and don't mind the hardness. XL tires are rated for load capacity at 42 psi. At up to 36 psi, an XL tire has the same load capacity as an SL tire of four less load index. Example:

245/45R18 96V -> 1565 lbs @ 36 psi
245/45R18 XL 100Y -> 1565 lbs @ 36 psi, 1764 lbs @ 42 psi
245/45R18 100H -> 1764 lbs @ 36 psi

(the speed rating has no relevance to this; just using examples so the spec is complete)

If I chart the values, it's a lot more clear visually:
psi vs load capacity lbs.png

So if why do we have XL 100 and SL 100 then? What's the value of a tire that needs 6 more psi to get the same job done?
https://www.prioritytire.com/blog/st...load-xl-tires/

The A4 allroad uses a higher profile tire than the A4 sedan and avant. This goes in line with the soft road intention of the product market. As such, using a staple A4 sedan/avant tire size, 255/35R19, will result in some speedometer and odometer error. Both 255/40R19 and 255/35R19 will have some error compared to 245/40R19, which is the same diameter as 245/45R18.

Also, the specs listed in the manual are simply the actual tires Audi sells on a new A4 allroad. They are hardly the exact requirement. So 245/40R19 98Y XL is simply what the actual spec of the tire they ship is. https://nemigaparts.com/cat_spares/e...r/673u/601950/. You've already seen that 96 load index is just fine for the vehicle, as noted by the 18" summer tire. Remember, ISO metric load capacity does not vary with tire size.


Looking at the point of load index, how much can the tire carry, consider your car. 3900 lbs curb, I suspect 1100 lbs payload (what's your door sticker say?). So that's 5000 GVWR. The only weight distribution reference I find for a B8 A4 allroad is 53/47 (not as bad as I was expecting). But that's only at curb weight, so that's 1034 lbs on each front and 916 lbs on each rear. Audi's 1100 lbs payload is based on five 150 lbs people and 350 lbs cargo (though it does not elaborate between 350 in the cargo area vs 250 in the cargo area and 100 on the roof rails). So at 5000 lbs gross, you're looking at a lot more weight on the rear tires than the front.

Taking my '09 avant, 3800 curb, 1100 payload, 4900 gross. I don't know if the later owner manuals still have the break out chart of normal load (450 lbs) vs full load (1100 lbs), but looking at my A4 avant, with the tire spec, recommended pressures, and converted to weight capacity (normal: 3800+450=4250, full: 3800+1100=4900):

18 XL 93H all-season - normal is 33/32, full is 36/39 - normal 1190/1146 -> 4672 total, full 1268/1356 -> 5248 total
18 SL 93Y summer - normal is 32/30, full is 33/36 - normal 1290/1246 -> 5072, full 1345/1433 -> 5556 total
17 XL 94H all-season - normal is 33/32, full is 35/38 - normal 1224/1192 -> 4832 total, full 1268/1356 -> 5248 total
17 SL 95H all-season - normal is 32/30, full is 33/36 - normal 1378/1323 -> 5402 total, full 1422/1521 -> 5886 total
16 SL 95H all-season - normal is 32/30, full is 33/36 - normal 1378/1323 -> 5402 total, full 1422/1521 -> 5886 total

So why the extra load index for the smaller wheels? It's probably nothing more than that's what they could find in the necessary tire sizing to supply for production. But so why not run a lower tire pressure? You could, purely from a weight rating perspective. But then how does that impact handling and fuel economy and durability? There's also the question of Audi's ability to accurately and correctly document such levels of detail. They very much could have the XL and unspecified incorrectly applied or just outright missing. But the XL is also a stronger tire for the same weight capacity, maybe they felt it didn't need to be as overspec'd? Lot's of puzzle pieces to juggle.


You'll have no problem running an XL 96. The necessary action would be the translation of the tire pressure from your stock tire (you list the manual contents, but don't say what's actually on the door jamb sticker of your specific car; you also don't list any of the tire pressure numbers, I have no idea what's in a '16 allroad manual) to the new tire.

[LionKing]

Lot of material involved in that subject. So load index. First thing you must note is are you talking about a P-metric or ISO-metric rated tire. The load capacity table is different for P-metric vs ISO-metric tires. P-metric tires have the P at the start of the sizing; ISO-metric do not. Additionally, the weight value for a given load index varies with tire size in P-metric; not so for ISO-metric. Here we're dealing with ISO-metric tires.

Second, understand SL (standard load) vs XL (extended load). When you don't see any term, it implies SL. SL tires are rated for load capacity at 36 psi. You can inflate beyond that, such as for driving faster than 99mph (up to V) or faster than 118mph (W, Y, Z). Or if you just want to max some fuel economy and don't mind the hardness. XL tires are rated for load capacity at 42 psi. At up to 36 psi, an XL tire has the same load capacity as an SL tire of four less load index. Example:

245/45R18 96V -> 1565 lbs @ 36 psi
245/45R18 XL 100Y -> 1565 lbs @ 36 psi, 1764 lbs @ 42 psi
245/45R18 100H -> 1764 lbs @ 36 psi

(the speed rating has no relevance to this; just using examples so the spec is complete)

If I chart the values, it's a lot more clear visually:
psi vs load capacity lbs.png

So if why do we have XL 100 and SL 100 then? What's the value of a tire that needs 6 more psi to get the same job done?
https://www.prioritytire.com/blog/st...load-xl-tires/

The A4 allroad uses a higher profile tire than the A4 sedan and avant. This goes in line with the soft road intention of the product market. As such, using a staple A4 sedan/avant tire size, 255/35R19, will result in some speedometer and odometer error. Both 255/40R19 and 255/35R19 will have some error compared to 245/40R19, which is the same diameter as 245/45R18.

Also, the specs listed in the manual are simply the actual tires Audi sells on a new A4 allroad. They are hardly the exact requirement. So 245/40R19 98Y XL is simply what the actual spec of the tire they ship is. https://nemigaparts.com/cat_spares/e...r/673u/601950/. You've already seen that 96 load index is just fine for the vehicle, as noted by the 18" summer tire. Remember, ISO metric load capacity does not vary with tire size.


Looking at the point of load index, how much can the tire carry, consider your car. 3900 lbs curb, I suspect 1100 lbs payload (what's your door sticker say?). So that's 5000 GVWR. The only weight distribution reference I find for a B8 A4 allroad is 53/47 (not as bad as I was expecting). But that's only at curb weight, so that's 1034 lbs on each front and 916 lbs on each rear. Audi's 1100 lbs payload is based on five 150 lbs people and 350 lbs cargo (though it does not elaborate between 350 in the cargo area vs 250 in the cargo area and 100 on the roof rails). So at 5000 lbs gross, you're looking at a lot more weight on the rear tires than the front.

Taking my '09 avant, 3800 curb, 1100 payload, 4900 gross. I don't know if the later owner manuals still have the break out chart of normal load (450 lbs) vs full load (1100 lbs), but looking at my A4 avant, with the tire spec, recommended pressures, and converted to weight capacity (normal: 3800+450=4250, full: 3800+1100=4900):

18 XL 93H all-season - normal is 33/32, full is 36/39 - normal 1190/1146 -> 4672 total, full 1268/1356 -> 5248 total
18 SL 93Y summer - normal is 32/30, full is 33/36 - normal 1290/1246 -> 5072, full 1345/1433 -> 5556 total
17 XL 94H all-season - normal is 33/32, full is 35/38 - normal 1224/1192 -> 4832 total, full 1268/1356 -> 5248 total
17 SL 95H all-season - normal is 32/30, full is 33/36 - normal 1378/1323 -> 5402 total, full 1422/1521 -> 5886 total
16 SL 95H all-season - normal is 32/30, full is 33/36 - normal 1378/1323 -> 5402 total, full 1422/1521 -> 5886 total

So why the extra load index for the smaller wheels? It's probably nothing more than that's what they could find in the necessary tire sizing to supply for production. But so why not run a lower tire pressure? You could, purely from a weight rating perspective. But then how does that impact handling and fuel economy and durability? There's also the question of Audi's ability to accurately and correctly document such levels of detail. They very much could have the XL and unspecified incorrectly applied or just outright missing. But the XL is also a stronger tire for the same weight capacity, maybe they felt it didn't need to be as overspec'd? Lot's of puzzle pieces to juggle.


You'll have no problem running an XL 96. The necessary action would be the translation of the tire pressure from your stock tire (you list the manual contents, but don't say what's actually on the door jamb sticker of your specific car; you also don't list any of the tire pressure numbers, I have no idea what's in a '16 allroad manual) to the new tire.

I'm saving this. That's insanely good info. Thanks!

Sent from my LM-V450 using Tapatalk