Porsche Enthusiasts Club Forum

Hi - Have just fitted 17" cup alloys to the S2, But they are fitted with 255 rears, that foul on the rear arch on the near side only when I have a passenger in the car (Are Porsches meant to have 5mm offset on this side only??).

Now I intially thought it was hitting the top of the arch, but no.. It's hitting the front of the arch under hard gearchanges???

I have been told that I will have to bend the wheel arch to clear. Has anyone else had this issue?? How did you solve it!! Your Help will be appreciated!! Need to solve before Gaydon!!!!

I had 265's on mine but the offset was 60 and had a 6mm shim to fill it out back to the standard 52.

You've got the wrong size offsets, other than pulling the arch out will a 245 tyre fit on your rim?

255 is 10" as near as make no odds, that'll be marginal even on the best maintained suspension.
What size rim & offset is it? Do you have any spacers on?

Something strange going on as nearly every late offset 944 running 17" wheels will have 255's on the rears. Sean your wheels were 18's?

Rich

I'm going to guess that your Cup wheels are aftermarket versions with an offset of around 23 to suit an early 944. Look on the back of the wheel for a stamp reading ET23

An S2 needs a rear wheel with an offset between 50 and 60 to space it into the correct position. My 17" track wheels have 285 rear tyres and they have plenty clearance even on the side where the bodywork is always a bit narrower (Early 80's sliderule designers )

Thanks all for the input. The wheels are ET47, and were bought from Design 911 as a straight fit. I have shredded one tyre . If you look at the picture you can see where it has hit the body. I am not sure if it is due to the offset or a problem with my particular car?? Strasse advise's I will have to roll the arch, but this seems extreme for a straight fit.

Things like this can be very difficult to sort, as dodgy suspension bushes mean the wheels can move into areas that is impossible to do statically when checked.
ET 47 vs ET 52-55 could be quite a difference when things are this tight, I think I'd go back to Design 911 & ask their advice.

Ouch, that does look nasty

ET47 is not one of the more common offsets but it puts the outside edge an extra few mm further out which is obviously making all the difference in your case. Maybe you have a few factors causing problems:

Is your rear lowered at all?
Are the shocks very old and worn?
Are the tyres the correct 255/40 or could they have a taller profile (like 255/45 or 255/50)

I did forget that Turbos all have rolled arches anyway which is obviously helping me with clearance and hindering your S2. Rolling maybe your easiest option but quite often the paint will crack meaning a rear quarter respray, but then you will already need this because of the rust in that crack (unless its a poor photo/ trick of the light)

The rear is standard, though the shocks were on the car when I bought it so no idea about the age of them, but seem OK. Your right I already need the re-spray so may as well go the whole hog and roll the arches. Think I will also get Strasses to do a check on the rear bushes! Need to sort for May 31st!!

Also read an article on your 3.2 Turbo a while back.... Was jealous when I read it, what BHP you pushing? Think I saw your car on the track at Gaydon last year?

It depends which rolling road you get it tested on Best figure has been 393bhp and 480lbft which is plenty enough for me at the moment. Yes, Gaydon was great fun last year and I'll be doing it again this year. I urge everyone to have a go as it is excellent value. Did you take your car round?

Yeah, took it round twice. Hit 140 on the speedo on the first stint. The second stint was in the heavy rain, but still hit 128 on the GPS. Have now spent a fourtune on the car, so looking to better that this year, assuming I can solve sreading tyres!!! Hopefully see you there!

The reason for the rear wheel contacting the arch is because you have fitted replica wheels. The reps are the only wheel with an ET of 47...
If you get a pair of genuine cup 1 or 2,s with an ET of 55 then itl be all ok..
Some, in fact a lot of S2,s were somehow out of line at the back end, especially on the passenger side.
My old S2 was exactly the same, it was "out of tolerence" + the rear pass side wheel rubbed on the arch, BUT only if i fitted replica wheels...
The other option is to get the rear arches rolled, as the S2 didnt have them as standard..
Im guessing the drivers side has plenty of clearance.???
I suspect the bushes will be ok , or maybee a little worn , considering the age of the car....

pardon me if im a numpty missing something obvious but couldnt you just put narrower tyres on the rear? 9J rims should go down to 225/40s according to the calc here:

http://www.carbibles.com/tyre_bible_pg2.html

I know fat tyres are perceived as superior but its worth reading further down the page past 'Fat or thin? The question of contact patches and grip.'

Bad luck, that is not nice at all I think I would be going back to whoever sold you those to complain, not fit for purpose.
I have Cup 2s fitted to my S2 17" with 255 tyres but the rim size is 9" not 10" I believe mine are replicas as I can not see any Porsche type numbering on them but I am sure from memory the offsets are ET55. Mine do not catch on the rims so as said previously it must be the offset on yours that is giving you problems.

I have exactly the same problem on a new to me 944 S2.1991. ( tyres are 9J X 17 H2. wheel rim is stamped ET47 )
I have only had it a couple of weeks and wondered what was causing damage to the tyre. I would be interested to hear how you resolve the problem.