America's Tire (Discount Tire) will not sell 235/40/19 tires to me

[derotam]

How is it more complicated? The allowed cargo/occupant amount comes out of the GVWR/GAWR right? So everything is based on the GVRW/GAWR right? So what is the technical calculation to look at a vehicle's GAWR and determine the minimum required tire load index to match the GAWR? The more I read this thread the more I am curious on the technicalities on these ratings. I have tried to do a bunch of googling but I am not finding anything that really speaks to my question.

So yes I agree that it seems that the tire place has a problem because the occupant and cargo number would then be wrong, but that doesn't make the vehicle unsafe or create a legal violation as long as the GVWR and GAWR's aren't violated. I do understand there could be a possible liability issue but there are ways to deal with that other than telling the customer no we aren't going to do that even though it doesn't make the vehicle unsafe.

 

[P-Lo801]

Indeed, if the OP has Tesla change out the door jamb label, then America's Tire can sell and mount the 96W wheels. Pure procedural and liability issue, not an engineering or design issue.

Is this even possible without having to buy new wheels and/or tires from them?

 

[SomeJoe7777]

Is this even possible without having to buy new wheels and/or tires from them?

I don't know, you'll have to ask Tesla.

So yes I agree that it seems that the tire place has a problem because the occupant and cargo number would then be wrong, but that doesn't make the vehicle unsafe or create a legal violation as long as the GVWR and GAWR's aren't violated.

Yes, that's true, but without a correct label, the vehicle owner no longer knows how much cargo and passenger weight he can load.

 

[P-Lo801]

Yes, that's true, but without a correct label, the vehicle owner no longer knows how much cargo and passenger weight he can load.

Isn't that what the owner's manual is for?

 

[SammichLover]

I did. i'm waiting on someone to respond. But I checked my own door jamb, and there are no load ratings listed on there, only the size of the tires that came equipped with the car, 235/45/18.

GVWR is the number that's needed. The "load rating" just points to a look-up table for lb limits on a tire. For each axel, divide the total by 2 and that gives you the minimum lb the tires on that axel must support.

<edit> D'oh, should have read further, since this has already been mentioned.

 

[P-Lo801]

GVWR is the number that's needed. The "load rating" just points to a look-up table for lb limits on a tire. For each axel, divide the total by 2 and that gives you the minimum lb the tires on that axel must support.

<edit> D'oh, should have read further, since this has already been mentioned.

Thanks. So help me understand. Here are the ratings listed on my door jamb label for my stock aeros and tires (posted previously in this thread):

GVWR: 4,806 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

Here's the label from someone who posted their label with the 19" sport wheels:

GVWR: 4993 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

What do these numbers mean if the one with 19s has a higher GVWR overall, but the GAWR for each axel is the same?

 

[SomeJoe7777]

How is it more complicated? The allowed cargo/occupant amount comes out of the GVWR/GAWR right? So everything is based on the GVRW/GAWR right? So what is the technical calculation to look at a vehicle's GAWR and determine the minimum required tire load index to match the GAWR? The more I read this thread the more I am curious on the technicalities on these ratings. I have tried to do a bunch of googling but I am not finding anything that really speaks to my question.

That is a long and drawn out discussion, probably warrants its own thread. In short, yes you're correct that the allowable cargo+passengers maximum load weight comes out of a calculation involving the GVWR, GAWR, vehicle empty curb weight, tire load index, tire speed rating, tire load range, front/rear weight distribution of the vehicle, maximum vehicle speed, and tire inflation pressure.

Take a look at the following articles for an introduction:

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=55

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

 

[SomeJoe7777]

Thanks. So help me understand. Here are the ratings listed on my door jamb label for my stock aeros and tires (posted previously in this thread):

GVWR: 4,806 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

Here's the label from someone who posted their label with the 19" sport wheels:

GVWR: 4993 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

What do these numbers mean if the one with 19s has a higher GVWR overall, but the GAWR for each axel is the same?

That 2nd label might be an AWD vehicle, whereas yours is RWD. If this is the case, the additional GVWR just accounts for the additional motor. Basically, the curb weight is higher, but the allowable passenger+cargo weight is probably less.

 

[SammichLover]

That 2nd label might be an AWD vehicle, whereas yours is RWD. If this is the case, the additional GVWR just accounts for the additional motor. Basically, the curb weight is higher, but the allowable passenger+cargo weight is probably less.

Almost certainly correct. I have an AWD with 18" Aeros and its label says 4993lb for the whole vehicle (GVWR).

 

[Gordon87]

That 2nd label might be an AWD vehicle, whereas yours is RWD. If this is the case, the additional GVWR just accounts for the additional motor. Basically, the curb weight is higher, but the allowable passenger+cargo weight is probably less.

Yes, mine is a LR AWD.

 

[SammichLover]

Thanks. So help me understand. Here are the ratings listed on my door jamb label for my stock aeros and tires (posted previously in this thread):

GVWR: 4,806 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

Here's the label from someone who posted their label with the 19" sport wheels:

GVWR: 4993 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

What do these numbers mean if the one with 19s has a higher GVWR overall, but the GAWR for each axel is the same?

The overall number isn't functionally a limit, here, for the tires. That's actually indirectly telling you what your official cargo capacity is, assuming you know your curb weight. For example my AWD is 4072lb curb weight (sitting empty at the curb, no driver). 4993-4072 = 921lb. Not a lot more than 2 adults and 3 hefty kids.

The axel ones are the key ones for the tires, because Tesla is saying you have to be ready for more pressure in the rear.

 

[derotam]

What is really fun, is that the GVWR is to some extent doesn't even relate to the weight rating of components but more relates to matching the performance specifications. How does a Performance version have a higher GVWR than a non performance version? And how does a dual motor have a higher GVWR than a single motor vehicle?

 

[brianman]

GVWR: 4,806 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

GVWR: 4993 lb
GAWR FRT: 2447 lb
GAWR RR: 2771 lb

max(GVWR)/4 = 4993 lb. / 4 = 1248.25 lb.
max(GAWR*)/2 = 2771 lb. / 2 = 1385.5 lb.

https://www.discounttire.com/learn/load-range-load-index

• 96 -- 1565 lb.
• 98 -- 1653 lb.

Perhaps my calculation is naïve but 1565 lb > 1385.5 lb (by a significant margin). So why isn't 96+ rating acceptable for both vehicle configurations?

 

[P-Lo801]

max(GVWR)/4 = 4993 lb. / 4 = 1248.25 lb.
max(GAWR*)/2 = 2771 lb. / 2 = 1385.5 lb.

https://www.discounttire.com/learn/load-range-load-index

• 96 -- 1565 lb.
• 98 -- 1653 lb.

Perhaps my calculation is naïve but 1565 lb > 1385.5 lb (by a significant margin). So why isn't 96+ rating acceptable for both vehicle configurations?

These were the exact calculations I couldn't wrap my head around. Thank you for providing examples!