Tire size for 18x10 C. lightweight - 986 Forum - The Community for Porsche Boxster & Cayman Owners

timothy · 08-01-2007, 06:32 AM

About to buy Carrera Lightweights from Wheel Dynamics, size 18x8 & 18x10, and need some advice on the best tire size with Goodyear F1 G3-D3. I'm still a newbie when it comes to tires.

Is the best choice 225/40/18 and 265/35/18, or do I go with something wider on a 10" wheel? Tire Rack shows other available sizes 275/35(or 40)/18 and 285/35/18. 03 and my daily driver. At this point no auto-x but I do like a spirited drive after a long day at the office. Thanks!

insite · 08-01-2007, 08:11 AM

i'd go with a 245/35 up front and 265/35 in back. the 285's get expensive and add to the understeer. the 245 / 265 combination is really neutral.

RandallNeighbour · 08-01-2007, 08:54 AM

Adding some 5mm or 7mm spacers in the back will heighten the aggressive stance of your boxster. I did it when I bought the same rims.

http://www.iwantaporsche.net/TOD/PICT0278.JPG

Adam · 08-01-2007, 09:02 AM

265's are pretty skinny for a 10" wide wheel. 265's are meant for a 9" wide wheel. Might look kind of funny or provide funky wear/handling issues....I would go to at least 275's, but 285's is usually the width you want with a 10 in wheel. You might get some more understeer though as Insite mentioned, but are you tracking the car? If not that would be a non-issue.

timothy · 08-01-2007, 09:36 AM

Seems when it comes to tire fitment everyone has a different opinion. I am not tracking the car but might try sometime.

So far nobody disagreed with 245/35 up front. Maybe 275 is a compromise on the rear. Is that a 275/35 or 275/40? Still open to other opinions. Thanks.

Adam · 08-01-2007, 09:59 AM

Quote:

Originally Posted by timothy

Seems when it comes to tire fitment everyone has a different opinion. I am not tracking the car but might try sometime.

So far nobody disagreed with 245/35 up front. Maybe 275 is a compromise on the rear. Is that a 275/35 or 275/40? Still open to other opinions. Thanks.

The stock 18's on the boxster had 40 up front and 35's out back. I would stick with that tire side wall height. You could go 245 up front.

insite · 08-01-2007, 11:09 AM

Quote:

Originally Posted by Adam

265's are pretty skinny for a 10" wide wheel. 265's are meant for a 9" wide wheel. Might look kind of funny or provide funky wear/handling issues....I would go to at least 275's, but 285's is usually the width you want with a 10 in wheel. You might get some more understeer though as Insite mentioned, but are you tracking the car? If not that would be a non-issue.

a 265 is fine on a 10". looks ok, too (that's what i run).

easyc · 08-01-2007, 11:31 AM

On my 9.5" OEM carrera lightweights, my 265 Toyos were pretty stretched... My new 275's protect the rim much better... you have to be careful with 285's as some may not fit. I also run 245's in the front, but they do rub under full lock... but im on PSS9's. Go with the 235 or 245 in the front and 275 in the rear you will be happy...

porsche986spyder · 08-01-2007, 12:08 PM

I have the 285/35 in the rear with no issues. I did have the 265 in the rear on my 10" wide rims and it did cause the outer lip to hang off by 1-2mm. Looks stupid this way and does seem to catch more rock chips and debri this way. If I were you I would go with a 275 or 285 in the rear. The stock tires of 265 are just NOT wide enough. For the first 9 months I had the 265 tires on my 18x10 and every time I went to a car show someone would point out that the tire really doesn't cover the width because you can clearly see the lip hanging out futher from the tire. Like I said it looks bad and even discount tire told me a wider tire would be better. The 265 tires will also were down on tread allot faster on the outsides.

timothy · 08-01-2007, 12:53 PM

Thanks everyone for the advice. "Gary" from Tire Rack practically fell out of his chair when I told him the recommended sizes.

I am leaning 245/35 and 275/35 since a 285/35 side wall sounds kind of tall. RUF will be doing the tires / wheels, alignment (hey where did that concrete median come from!), and 60k service, so I also emailed Hans for advice. I'll add his response to the thread for future readers.

porsche986spyder · 08-01-2007, 01:06 PM

Quote:

Originally Posted by timothy

285/35 side wall sounds kind of tall.

It does sound tall, but if you think abou it, the width of the rim being wider than the stock rims compensates for the side wall hieght. In other words, once it's on the rim, you can not visually see it as being tall because the widder rims stretches the tire out a little making it come back down in overall hieght.

timothy · 08-01-2007, 01:18 PM

Reply from Hans (RUF Auto Center - Dallas). As an aside, I love going to RUF. It's like being a kid in a very expensive candy store.

I am glad you emailed me, there is pretty much no way you are going to fit these tires properly, even if they did fit somehow, they are to tall and ABS/PSM could be affected,

Stick with the 225 and 265, those will work best

TriGem2k · 08-01-2007, 01:20 PM

It actually should be a 285/30 not 285/35. You WILL RUB 285/35 with PSS9 setup.

TriGem2k · 08-01-2007, 01:23 PM

Porsche Recommended tire size for 18X10 is 285/30/18.

Porsche Recommended tire size for 18X8 is 225/40/18.

With a 225/40 and 285/30 you will have no issues with PSM or ABS

porsche986spyder · 08-01-2007, 02:23 PM

Quote:

Originally Posted by TriGem2k

Porsche Recommended tire size for 18X10 is 285/30/18.

Porsche Recommended tire size for 18X8 is 225/40/18.

With a 225/40 and 285/30 you will have no issues with PSM or ABS

Yes, I think this is right. I'm at work and can't get to my car, but the 285/30 sounds right and I believe this is what I'm using also. RUF doesn't know everything. They are just telling you what is the norm, not what will ALSO look best. Go ahead and get what you want, but I bet you will regret it once you see it on those rear tires.

easyc · 08-01-2007, 02:41 PM

the problem is that you have to be careful with what brand 285 you get... a pair of 285's from two different manufacturers can vary 3-4 mm in overall width...

timothy · 08-01-2007, 03:12 PM

Quote:

Originally Posted by easyc

the problem is that you have to be careful with what brand 285 you get... a pair of 285's from two different manufacturers can vary 3-4 mm in overall width...

Good to note. I'll keep an eye on the width-ometer and bias toward the narrower end of the tire spectrum.

TriGem2k · 08-01-2007, 04:32 PM

@ Timothy,

There is absolutely nothing wrong with going with a 265/35 on the 10" wheel. I always go back between the two (285/30 and 265/35). It all depends on what tire I want to run. I know for a fact that the width of a Bridgestone R050A Pole Position in 265/35/18 is just SLIGHTLY narrower than the Michelin Pilot Sport PS2 that is a 295/30/18. It all depends on the tire you want to run. If you post the brand and model of the tires you are looking at we might be able to help you out a little more.

In the 6.5years I've owned my car I have used various wheels and tires. I've pretty much used every "high end" tire out there in a 265/35 and 285/30. Let me know what your looking at exactly and maybe I can help you make that final decision.

FYI, I have also run the PSS9 on my car. Fitting certain wheels and tires on that suspension is a pain in the butt.

~James

Cloudsurfer · 08-02-2007, 08:49 PM

I also recommend the 265/35, I run this size, along with a 225/40 up front on 18x8 and 18x10 hollow spokes. If you do want a 285, it is a 285/30, and yes, it will increase understeer.

Patrick

eVoMotion · 08-03-2007, 01:37 PM

FYI - I am running Pirelli Pzero 225/40/18 & 285/30/18s.

First day at the track was yesterday...it did understeer some at times, but I put it down to me being on the throttle too soon. When I got it right - brake, turn...then throttle...it went right where I wanted with the PSM flashing all the way.