333pg333

I'm pretty sure Thingo is trying to fit 265's on his car soon?

thingo

Yes I am pretty sure I can get them to fit, but I am changing my front springs first, which willl give me a lot more space over stock.

anders44

how is turn radius affected? what size rims will you try with?
even 997 GT3 only has 235 up front.. but with 265/285 it would keep the 20mm difference in with, although % will probably be a bit off

RolexNJ

As per my conversation with Karl from Racers Edge:

"As far as tires, I have had issues with 295's on the back, they will go on but I have had "thumping" issues with them hitting the chassis pretty hard. You can definitely run 285's in back. 265 or even 275's will go on up front with the right offset." And here is a man who knows his stuff. He didn't tell me the year of his car, the model of the rims, or the off-sets too. But to me his word is as good as gold. He is a proven racer, designer, and successful business man, and for him to say this he had to have exact measurements. I mean after all, he uses a set-up like this on his own personal race car. I am still researching now as we speak. Just talked to Fiske, again, today too. Anyway....

anders44: You seem new here, so welcome. I don't know what year car you have, the mods, projected BHP, your usage for the car, let alone what it looks like? So we don't (I don't) know a thing about your background or who you are, no offense just very curious as you are a new user. If you do mount these tires sizes, and have the "exact" off sets, I wish the best for you. After you do all of your testing, I think we all would appreciate you sharing your findings. Just don't forget to do extensive testing, including severe lateral cornering, threshold braking, squatting under acceleration, and other testings too. Just make sure you cover all the testing variables, and hopefully you won't have any clearance nor rubbing issues. Let me know.

anders44

some info
car, 86 turbo, with turbo S engine, getting full standalone engine mgmt from VEMS, bosch044, 890cc injectors, GT30R+++, new suspension, rims, brakes. everything that's not metal is thrown out.

It's pretty easy with offset as I just machine everything to exact spec I have a friend working as a cnc operator.

hubs for rotors, caliper adapters, spacers. everything will be made from scratch. this IS going to be a "racecar" meaning it has plates and has the legal stuff intact, but apart from that it will only be used for track. I will class it into the GT class of the porscheclub norway series

tire witdth is a problem Ive seen it before on other cars I've had "this will fit" but thats from people who never took it to a track. I drive 80% of the time on the nürburgring norschleife which is a very bumpy track requiring a lot of suspension travel and softer setup than regular tracks. going 130mph into the fuchsröhr and having tires hit fenders and changeing friction is not fun. you have a few G's there.

as far as testing goes we have a local track thats pretty flat and nice to test on and have a few different dataloggers. like ax22, driftbox etc.

Geneqco

Okay, fitted the 305s tonight. They are 660 diameter so about 23mm greater than the stock tyres. 305mm is actually the section width.

The tyres are on 18" TechnoSport Hollow Spoke with 63 offset - they look pretty awesome on the car. They do fit, however the concern is, being slicks, the flex resulting from the greater adhesion and weaker side walls compared to road or R spec tyres would probably result in some rubbing. However, my mechanic thinks they would be okay if they were road or R Spec tyres in that size. They do really fill out the guards though. I tyre closer to the stock diameter would be a better fit.

anders44

could you put up pics? which brand of slicks are they? is the car lowerd? etc. pretty cool though that you can fit 305's without modding fenders!

Geneqco

Car is 1989 model with M030 but otherwise stock suspension. The slicks are Pirelli 305 x 660 x 18. The car is still in the workshop but I'll see if i can tgake some photos in the next few days. Not much scope for lowering with these but they are an inch bigger in diameter than they should be.

RolexNJ

Lowered at all? And let's see some nice pics! And "after" you do a full test drive, under various conditions, please re-post how they fit and/or any fitment/rubbing issues too.

Geneqco

The car is not lowered. It will be a while before I can take it for a test drive. In any case, I would expect there to be rubbing issues with this setup without any mods given that the tyres are slicks... the cornering forces generated and the sidewall flex expected.

333pg333

That's promising but I would think that any advantage of a smaller rolling radius R-spec tyre would be lost with any lowering, but it sounds close.

anders44

I belive you get the pirellis with 20mm less circumference as well, should probably be a better fit?

anyway, pretty amazing that this works without major body mods!

Geneqco

Actually 15mm less diameter - 645s instead of 660s. they were supposed to supply me the 645s. i got them really cheap so I can't really complain. I planned to do some mods anyway.

Geneqco

pretty true in terms of static clearance... however, the R Specs, being street legal are of quite different construction with stiffer sidewalls and not as much traction - they would also be a lower profile and hence stiffer again. The mechanic who helped me fit them said he believed they would be okay if they were R Spec or road tyres but the slicks can move and twist a couple of inches.

Geneqco

Please find some images attached. Ufortunately black car and tyres and night time don't help so hopefully they are clear enought to be helpful.

Bear in mind these tyres are not only wide but are also an inch taller than the standard Turbo S size.