Tire Size Questions

Hey all, In anticipation of getting Apex wheels in the group buy I have some tire size questions. The guys over at apex were very helpful in answering most of my questions but I had a couple of more. My stock 18'' turbo twists have 225/40 front and 265/35 rear tires. The apex wheels will be 18X8.5 front and 18X11 rear. They said that the 225/40 front tires are fine but rears need 285/30 rears. When looking at tire rack my current pilot sport A/S 3+ tires only have rear tires with 285/35. The only suggested tires that have the sizes they recommend are summer tires. I prefer to run all seasons so I can drive the car in colder weather... They said I could use 285/35 rears but the rolling diameter different would be 3%. as opposed to -1.4% with the 225/40 and 285/30 or .08% with 245/35 and 285/30.... so my question is if I use the 285/35 so I can get an all season with a 3% difference in rolling diameter what sort of issues will I encounter?

i'm getting a brand new set of Sport Techno Wheels direct from Porsche. Coming from Germany in a week or two. The rear wheels are 18x11. You really need 295/30/18 for an 11 inch wide rear wheel. 285s will work but they are not the optimum tire size for the 11 inch wide wheel. The selection of this size has dwindled over the years but Pirelli, Michelin and others still make this size in the tires we need.

I agree with soverystout that you should run 295's on 11" wheels. You did not mention if your car was a C2 or C4, I am assuming its a C4 since your wanting all season tires.

It is a C2. I drive my car during the winter as long as theres no snow despite cold temps. Summer compound tires are no good in cold temps from my understanding. I wish to run all seasons and while I see your point that 295s are more ideal there is no all season I could find with that size configuration. I wish to run 225/40 and 285/35 which would have a rolling diameter difference of 3%. What issues would I run into with that 3% difference?

I guess I could keep winters on one set and summers on the other but that is not ideal for me as I'm lacking storage right now

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Oof that's tough man, going to be hard pressed to find all seasons. For reference, I do know multiple people on Instagram 996 accounts that run the A/S 3s because they were sick of replacing the rears every 5-7k miles. They love 'em. Another option that may end up costing you not much more is to get Pirelli winter storizzos (spelling?) in your stock size, and then buy sumitomo HRT IIIs for your new wheels, verrrrrrrry good tire in the dollar per performance sense, rears in 295 are only $150 each!! But of course you have your space/storage considerations.

I only asked about it being a C2 or C4 because I was in same situation. I read many threads on this site where it seemed that the tire dia difference is more critical for a C4 and many don't think that a difference like what you have stated does not harm a C2. I am no expert and take what many say with a grain of salt so do some searching and you too may come to the same conclusion as I did.

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Yes, I have the A/S3 now and they are great. Again, I want to use them on my new wheels when I get them. Apex says, "at the end of the day you can run the 285/35-18 tire, however we recommend choosing a tire compound that is available in the ideal sizes mentioned." They mention 224/40 and 285/30 but again the A/S3 come in only 285/35 so there would be a 3% difference in height. What issues can this 3% difference cause??????

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Wait, I am a bit confused about what you are meaning to say... you meant to write "don't think that a difference like what you have states does harm a C2"?? you wrote "does not harm"... meaning that many people think a 3% difference is ok... right?

On my GT3 wheels (11") for C2 I run 295/30 with a 5 mm spacer....I would not run 35s

On a C2, my understanding is it should be fine to run 35s. 3% difference isn't much and for sure much less than the difference in sizing between manufacturers. For instance I just switched to Michelin PSS from Falken FK453. Exact same size spec, however Michelins are visibly smaller. I"m guessing more than 3% as I don't think you could see 3% without measuring. If I was prepping to race Lemans, 3% would keep me up at night, but to drive 65 mph on a freeway, not so much.

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Thanks for the response. What about for DE events which I do maybe 2X a year... could the 3% issue be a problem? It's looking like the best solution would be to keep my turbo twists for AS tires and use the new wheels for summer tires... when I finally get the wheels I'll see what my shop has to say on the issue as well.

I have been considering the same issue. I'm running Hankook v12's on my car now but I'm due for a replacement. I won't be buying Hankooks again. I'd really (really) like to get the new Michelin PS 4S tires but the closest size for the rear is 285/35. I was thinking of switching the fronts to 235/40 (from 225/40) which would reduce the difference to 2%. The AS3+ would be my second choice. Their performance in the summer is surprisingly close to the old PSS, but they are still usable when the temperature drops near freezing. I wouldn't use them as a winter tire, but they would allow me to keep enjoying my car in the shoulder seasons. My understanding is that the only possible problem on the C2 would be that PSM might incorrectly conclude that the wheels are locking up due to the different rotational speeds. I thought a 2% difference was safe, but I'm not sure what the maximum difference is.

When considering wheels and tires, there is a handy little thing at the top of the forum page under Tools

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thanks for the info my car doesn�t have PSM so that�s good to know

I have AS/3 on a bmw, but I have not run the AS/3+. I can't imagine they're THAT much better, but the as3 is a joke compared to even the cheapest summer tire the sumitomo htrz3. The as3 is a fantastic all season, but you'll get a lot better performance out of a 265 or 275 summer tire than a 285 all season. Unless you just want a bigger tire number for bragging rights, then just LOL. The as3 is terrible on track- overheat, greasy, chunks at even a moderate pace. The z3 will chunk too on track at a pretty good pace, or it you like a fun amount of slip angle. Also the sidewalls are very stiff so they're a little uncomfortable but fantastic for the price. That being said, a 3% difference? You won't notice. Nice thing about the 2wd cars is they're not hypersensitive to OD like the AWD ones. ETA if you want the performance of a sports car on summer tires, 5k is a VERY reasonable life span for summer tires. If you want to be competitive, 200TW tires will last less. You can take some rear toe and camber out and get a little more life, but it'll be a lot more unstable.

Thanks for a response that address the rolling diameter issue. I�m not upsizing tire sizes for bragging rights. I�ve just ordered new wheels via the group buy and the slight change in wheel size necessitates a change in tire sizes. I understand what you�re saying regarding the AS3 on track. I�ve only used them on track for 2 DE events and they did get a bit greasy but the day it was cooler out and raining they did an excellent job... either way I will eventually run winters on my old turbo twits and summer on my new wheels but in the meantime I may go through a cycle or putting on AS tires to my new wheels as I drive the car periodically year round up in the north east and our winters temps vary from the negatives to those odd days when we hit 50+ middle of winter (climate change in real y�all)

Don't want this to be another "what's the best tire thread" but just wanted to put out my experience with tires. I live up in the sierra foothills of CA and get snow now and then. I am now running Bridgestone's Potenza S-04 Pole Position tires and feel they have great traction in the rain and cold. These tires do come in the size your looking for "285/30", you may want to read some of the reviews. Relating to tire size differences, I am running 235/35/19 and 295/30/19 which have a 2% difference in dia on my C2 without PSM and feel no difference or have had any complications, not sure if 1% more (3%) would make any difference. Also seem to be getting good mileage out of these tires, Already have 10K miles on them and still look new.

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thanks for the response. I�ll check out the potenza s-04