Anybody run P235/55R15 Rear Tires?

BARHOPPER · 06-28-2006, 07:11 AM

I have a 1985.5 944 n/a and am looking to put some wider rear tires on it with some 1.25" or 1.5" wheel spacers. According to the specs, running 235/55R15's will keep the speedometer virtually the same as using the stock 215/60R15's. It's obviously a rare tire size, but I have found that Goodyear has this size. Also, my rear wheels are 15x8". Anybody use this setup or have any advice on this?

ronniebaldino · 06-28-2006, 12:25 PM

What are you planning on using for the front. These cars tend to be balanced well with equal width tires on the front and back. With a huge diff like I think you are planning it will probably under-steer really bad.

235 is no problem though as far as space goes. Don't know about w/ the spacers, depends on the offset of the rim. I have 225 and lots of room to spare.

BARHOPPER · 06-28-2006, 05:12 PM

I was planning on keeping the 215/60R15's on the front, without spacers, as they are new tires, but thought that it would look a little better with wider tires on the rears to fill out the wheel wells. With the 235/55's keeping the speedo correct I thought that others may have tried out this combination as well.

ronniebaldino · 06-28-2006, 07:08 PM

Honestly try the 215s with the spacers. I have a set of 16" wheels with 225 rear and a set of 15" with 205 and even the 205 with the spacer look like they fill out the fender. The spacer makes a huge difference.

BARHOPPER · 06-29-2006, 05:08 AM

Thanks for the suggestion. I think I'll go ahead and order the spacers first, try them on with the tires that are on the car now, and then go from there. Gonna need back tires anyway, but at least I can get a feel for how it will handle and look.

ronniebaldino · 06-29-2006, 06:18 AM

Keep in mind you may need longer wheel studs if your spacers are the slide on the studs kind. As far as PCA track events goes I think there is a minimum # of full turns while tightening the nuts. Good safety rule of thumb. It depends how thick the spacers are though.

Harpman2 · 07-01-2006, 05:26 AM

I bought a set of 16 inchers that came off a turbo I think. 7 inch wide in front and 8 inch in back. I think they originally had 245s on back and on front had 225s or maybe 215. So would that have caused understeer on that turbo as received from factory, and if yes why would Porsche do that?

924Sman · 06:08 AM

You should not need spacers at all. If the offset is correct. 235 is fine . A 16" wheel running a reduced profile will not change the speedo, in other words the outside diameter is the same 15 to 16". Gain an inch on the outside diameter then you may see a speedo difference.

But you should be able to go 245's on 8" w/no spacers, provided the wheels are 52mm OS. But for 235's more than enough roon to fit.

You have wider quarters than mine and I have a set of 245 rears on a 924S in 16". You have plenty of room!

Spacers are to correct the offset not to widen the track per say although some use them to widen but a wider track is better accomplished by widening the rubber not how far the wheel is placed outbound. Some would argue this but when spacers are used you may have a need for longer studs. Racers will keep the wheels as close the hub as possible vs. having more metal in between the wheel and hub. Added weight is also a factor. Spacers can change the track width outward where a wider tire on OE o/s wheels will keep the track stock but move the width inward. So in real there is more rubber vs wider tracking.

Dal

BARHOPPER · 07-01-2006, 09:35 PM

Well, I decided to play it safe and stick with the 215/60R15's all the way around. I did however order 1.5" wheel spacers for the rear and 6.5mm spacers for the front. This will hold me for a while until I go with the 17" Turbo Twists.

Dantilla · 07-02-2006, 12:31 PM

Quote:

Originally posted by Harpman2
So would that have caused understeer on that turbo as received from factory, and if yes why would Porsche do that?

The auto industry thinks it's much safer for your "average" driver that cars naturally understeer, so that's what is engineered into just about every car sold. Maybe a car like the Lotus Elise is different, but I doubt it.

944s handle best with equal sized tires both front and rear. The early turbos came with a 205/225 setup, bumping up to 225/245 on the later cars.

The top 944 autocrossers here are running 245s all the way around. Bumping the fronts up to the same size as the rear gets rid of the factory-induced understeer.

BARHOPPER · 07-02-2006, 12:42 PM

I assume that you're referring to 245/50's and would these be O. K. mounted on 7 inch rims or only for 8 inchers all the way around?

Dantilla · 07-02-2006, 09:26 PM

My race class (SCCA's ITS) limits wheel width to 7". We all run 225s, and they are pinched on a 7" wheel. I would definately not put a 245 on anything less than an 8".

One of my 944 autocross buddies runs 8" all the way around, and the other one (they are both top contenders in their class) has 8&9x17 Fikses, also with 245s both front and rear.

My 911 has 245s on 9" rears.

You may find a tire shop willing to mount 245s on your 7's, but the tire will not perform properly. Poor handling and increased tire wear will result.

BARHOPPER · 07-03-2006, 07:42 AM

Yeah, I thought 245's would be a little wide for 7 inch rims. My car, now that i've finished it, is going to be a daily driver so I think the stock 215/60's will perform and last the best for my needs. Along with less wear and tear on wheel bearings, etc. Thanks for all the input!

924Sman · 07-03-2006, 09:02 AM

[I have a 1985.5 944 n/a and am looking to put some wider rear tires on it with some 1.25" or 1.5" wheel spacers. According to the specs, running 235/55R15's will keep the speedometer virtually the same as using the stock 215/60R15's. It's obviously a rare tire size, but I have found that Goodyear has this size. Also, my rear wheels are 15x8". Anybody use this setup or have any advice on this?]

Your first post said on 8" rims, now if it is 7" then 245 is too wide.
What size is it going to be?
Dal

BARHOPPER · 07-03-2006, 09:53 AM

The front's are 7 inch and after thinking about it a little more I thought that I should try to stick with the same size tire on all four corners. This way, with being able to rotate them once, I can buy some time before moving up to the 17 inch wheels. I originally was thinking of going wider on the rears simply for the looks of them, but I think that the 1.5 inch wheel spacers back there will satisfy me as far as that goes.

924Sman · 07-03-2006, 10:19 AM

Spacers are a waste of money in your case. All you are doing is pushing the entire wheel outward which has little room to start with in stock form. By going a wider tire/wheel the width is placed inward towards the hub. The space to the outward or fender remains the same or little change.

Your wheel offset is 52.3mm as is, put spacers on and turn that 52.3mm into 70 something offset. Wont happen.

Dal

BARHOPPER · 07-03-2006, 12:53 PM

What I'm wanting to do is to fill out the wheel well some more and to give it a wider stance. By doing this with the wheel spacers I thought that I'd give myself a little more room on the inside in order to try some wider tires, which seems to make sense from what you are saying. After reading up throughout the forum though, I decided to play it safe and stick with the same size tires all the way around, but still accomplish filling out those extra wide wheel wells.