Load Rating Questions...

[BadSeed]

I drive a e28, with 16x8s all the way around and now I'm kinda sketched out.

So I currently have Kuhmo 215/55s and 225/55s on my car with a load rating of 95...
And I just got my Falken 512s in today, sized 205/40 all the way around. But these are only rated at an 83, which seems way too low.

Has anyone else ran into this? And what happens/happened? Or should I be worried?
I can't believe I didn't catch this til I had the Falkens sitting next to my wheels and tires now...

[wheelfetish]

Not sure how much your E28 weights, but a load rating of 95 means 1521lb per tire. Multiply that by 4 and you get 6084lbs total. Thats how many pounds your stock tires support.

For Falken 512s a load rating of 83 would be 1074lbs per tire, 4296lbs total. So if your car weights under that, your fine. (from what I understand).

Keep in mind that load ratings are determined using an applied vertical force against a tire under laboratory conditions (usually 65 ambient degrees). The heat rating for the tire can affect the maximum load the tire can handle at a given temperature. The load index is how much weight you can put on top of your tires.

Ive done business, or tried to, with tire shops locally and tried to buy a bigger tire with a lower load rating and they refused to sell them to me for my E36. Its against the law for a ASE certified mechanic to sell tires that are not the manufactures recommended load rating. (so I was told)

I had 85 on my 18x8 beyern rims for 2 years and never had a problem with the tires being under too much load, even with 5 people in the car and 2 12in subs.

[Rally]

Not sure how much your E28 weights, but a load rating of 95 means 1521lb per tire. Multiply that by 4 and you get 6084lbs total. Thats how many pounds your stock tires support.

For Falken 512s a load rating of 83 would be 1074lbs per tire, 4296lbs total. So if your car weights under that, your fine. (from what I understand).

It's not exactly that simple because weight distribution isn't always 50/50 front to rear, and isn't 50/50 side to side, especially when going into a corner.

Let's say you have a 2000lb car. Sitting still, the front tires might have 600 lb's on each corner. The rear tires each have 400 pounds.Throw it into a corner, and that weight is gonna shift to the outside tires. Front outside tire might get up to 750 or something (not accurate, just using it as an example)

How much does an e28 weight? The 205/40's 512's don't hold much weight.

[BadSeed]

Ok, thanks guys.
The stock weight of an e28 is 3,020lbs... So from reading what all this up above says, I may be pushin it.
The 205/45s have a load rating of 87, so that's at least a little better. I may have to try and get those instead. Man, I feel so stupid.

[Hotrun_bb]

cody, if the car weighs 3,020 pounds you may be ok. If a 83 load rating holds 1074lbs per tire then it is 4296lbs. Even with weight being thrown around in corners Its still not maxing out the load rating. I think if you run a little higher PSI on the tires you should be fine.

[wheelfetish]

cody, if the car weighs 3,020 pounds you may be ok. If a 83 load rating holds 1074lbs per tire then it is 4296lbs. Even with weight being thrown around in corners Its still not maxing out the load rating. I think if you run a little higher PSI on the tires you should be fine.

This.

a 205/40 will have more stretch then a 205/45, so if your looking for stretch, 205/45 might not be the best tire. Even with a load rating of 83, you should be fine. If you decide to sell your 512's let me know

[BadSeed]

Yeah, I talked to Falken and they said they strongly suggest getting a different size... Thanks for the help guys, and since they are on my daily (actually, my "only" car. Ha), I think I may take their advice as I need these to last as long as I can.
I'll PM you wheelfetish

[Revhard05]

cody, if the car weighs 3,020 pounds you may be ok. If a 83 load rating holds 1074lbs per tire then it is 4296lbs. Even with weight being thrown around in corners Its still not maxing out the load rating. I think if you run a little higher PSI on the tires you should be fine.

let me ask a question. Does the load of the car on the inflated tire effect the pressure. In the tire to go up or down?


everyone knows this right? the pressure stays the same?, ok then


Fluid power 101 : to have pressure you have to have resistance to that. You cant meassure the pressure of flowing water a creek? you can measure the force of the flowing water but no the actual pressure in the water. You can calculate head by the depth.

Resistance, This comes from the tires not letting that built up air pressure explode them,i.e side wall design and steel belt design

The Corner weight of the car is exerted on the ground through the air pressure in the tire.

So the 1000lbs is directly related to the surface area on the tire, so this means if their is 40 psi tire pressure, (1000lbs)/(40 lb/in^2) = 25in^2 of surface area on the tire.

So you are saying to cause more internal resistance.

I dont see where Pumping more air into a weaker tire will solve the problem.

Bad Seed Dont so it!

[M.Burroughs]

Sorry man but as I said before, you have nothing to worry about. I've run 205/40s witha load rating of 84 on my car for years. I've driven them HARD, upwards of 100mph, I've done drift events on them, I've abused the hell out of them. There is not an issue here. There are people who have put these tires on WAY heavier cars. Hell, I've piled 5 people AND probably 300lbs worth of shit in my trunk on these tires.

I'm assuming you ordered from Tire Rack and they said the tires weren't load rated for your car when you tried to order them... right? They do that shit for everything. As I said in the message you sent me, get the tires you want.

To be frank, I didn't know anyone actually gave a damn about load ratings.

[Hotrun_bb]

Since your gettin new rubber... sell the 205/40's to ben.

[BadSeed]

Thanks Mike, and yeah that's exactly what they said, plus a bunch of "you'll wear right through them in no time at all..." But I think the 45s will look better and fill the fender gap I have right now better. Plus, 8s aren't that wide, so 40s would make them look super narrow, especially from the rear.

Paolo, shoot I would've, but I already sent em back to DTD to get my others... UPS picked em up on Tuesday.