fabric

Ok, a little behind the 8 ball, but I'm going to get some snow tires. For an 87, Porsche's current recommendation is 205/55r16 94 V XL (for front and rear) and 225/50r16 96 V XL (for rear). I'm probably going to go with the different sizes, I'm not going to rotate if they need to be remounted.

I called discount tires about the Hankook W300. Hankook's web site has the exact tires above listed on their website, by discount only had 91 load ratings, and that they wouldn't be able to get the higher load ratings.. How important is load rating? Is this tied in to the speed rating, or is it all about vehicle weight?

Am I playing with fire if I can't locate the exact load ratings Porsche recommends? I don't need V rated tires, I'm not going to that fast, if that makes a difference.

Vilhuer

Speed and load ratings are totally different things. 91 should be more than enough for 928. There probably is not any factory minimum other than tire load rating must be higher than weight it is subjected to. If actual weight gets really close to the limit, depending on tire manufacturer ride quality might suffer too much. But 91 on 928 should have 200 pounds extra capasity on each corner even with four heavy people on board.

fabric

Thanks. I figured they were unrelated, but wasn't positive. Should have done a little more research, cause this is intereting: 928 manual specifies minimum of 88 load rating, 1235 lbs. 91 load rating is 1356 lbs, and front axle weight max is 2028 lbs. Not sure why the Porsche document on snow tires specifies 94 and 96 load ratings. On the back I can see having a high load rating, but rear axls is still only 2456, which is still less than the 91's could do.

marton

What Porsche document is that? I just have a couple of lines in my handbook about snow tires sizes. Is there a mores substantial document, maybe on the web somewhere?

Marton

Vilhuer

Don't know what document has such info but one thing came to mind what could be cause for larger rating for snow tires. They usually have more flexible sidewalls and this makes direction changes etc. less sharp. Maybe Porsche want to keep drivability above certain standards and thus ask for higher weight carrying capasity which will most likely result more rigid sidewalls as by-product.

fabric

Sorry, another poster, I can't remember who, put it in a post. I've put it up on my rennlist site:

http://members.rennlist.com/fabric/p...re%20specs.pdf

Vilhuer

Ok, that list. Those load and speed ratings come from what tires are available from different manufacturers. Very likely they are not minimum what factory allows for 928. Listed tires just happen to have those ratings.

fabric

That makes a bit more sense, thanks for the clarification.