Wrong tyre size set up

[swright]

My car has cup 3 wheels on. The rear tyres are 255/40r17 but the fronts are only 205/40 r17 and they sit quite far under the front wings. It makes for interesting handling!!

Here's a pic to show you what i mean.

What's the correct size i should have on the fronts, 225/40 17? And what size spacer would i need to do the job? Oddly, the rears do have spacers but not the front!!??!

Am i right in thinking these wheels come from a 996?


Thanks,

Stuart

 

[mik_ok]

225/45/17

What offset are your fronts?
(and what offset are the rears, and what size spacers are fitted there?)

 

[swright]

I embaresed to say i realy dont have a clue about either. The offset will be on the rear of the wheels will it not?


Now i think about it the rear spacers looked about 10mm but thats just going by eye.

 

[Fen]

If they are genuine Porsche wheels they will have the width and offset cast in either side of the valve stem.

 

[random hero]

Im pretty sure the wheels are replica's as the genuine ones are 18" not 17". Ive run 205/50 and 225/45 both were fine but i seem to recall that 205/50 was the offical size from porsche (for the 968).At a guess i would say your car is a pre-abs early offset car with later offset wheels ??

 

[appletonn]

Stuart, it does look as though the fronts are the wrong offset for your car - need some spacers to push them out into the arches.

RH has hit the nail on the head!

 

[random hero]

The car in my avatar picture is on 7" front rims with 205/50/17 tyres and to be honest they could of done with being about 1" or so further out !!

 

[TTM]

As said above, definitely the wrong offset.
I guess there is very little clearance between the wheel and the shock assembly[&:]

 

[mik_ok]

ORIGINAL: random hero
Ive run 205/50 and 225/45 both were fine but i seem to recall that 205/50 was the offical size from porsche (for the 968).

I'm certain the correct front tyre size for a 968CS was 225/45/17. 205 on the front with 255 on the rear is far too big a difference for a car with 50/50 weight distribution. (edit: unless you love persistant understeer of course)

If you do have the wrong offsets on the front your steering will feel mighty weird too. I'd pull a wheel off and check - if the ET is around 50 you have correct offsets - around 20 and the suspicions of the other honourable posters are correct - in which case you'll need spacers approx 30mm to correct - or - better still - get new wheels with the correct offsets.

 

[rcsalmons]

They'll be boxster wheels 7" front 8" rear. I believe the 996 used 7.5" with 225 tyres.

Spacers will sort you, I guess 10mm ish.

Rich

 

[RHT45]

ORIGINAL: mik_ok

ORIGINAL: random hero
Ive run 205/50 and 225/45 both were fine but i seem to recall that 205/50 was the offical size from porsche (for the 968).

I'm certain the correct front tyre size for a 968CS was 225/45/17. 205 on the front with 255 on the rear is far too big a difference for a car with 50/50 weight distribution. (edit: unless you love persistant understeer of course)

If you do have the wrong offsets on the front your steering will feel mighty weird too. I'd pull a wheel off and check - if the ET is around 50 you have correct offsets - around 20 and the suspicions of the other honourable posters are correct - in which case you'll need spacers approx 30mm to correct - or - better still - get new wheels with the correct offsets.

mik_ok is correct about the 968CS (and the Sport). They run 225/45/17 front on 7.5ET65 and 255/40/17 rear on 9ET55. Perhaps the person who fitted these wheels wanted to avoid the excitement of kicking the rear wheels out on full boost! Is that possible with a 944 Turbo? Must find someone to let me try one day..........

 

[random hero]

Regarding the 205/50 and 225/45 i didnt mean i ran them front and rear ,i meant that ive had both sizes on the front at different times.Ithink you are right about 225 being the standard for the 968 as i was forgetting my wheels are off a boxster which is standard on the 205/50 tyre.

 

[Fen]

ORIGINAL: RHT45

mik_ok is correct about the 968CS (and the Sport). They run 225/45/17 front on 7.5ET65 and 255/40/17 rear on 9ET55. Perhaps the person who fitted these wheels wanted to avoid the excitement of kicking the rear wheels out on full boost! Is that possible with a 944 Turbo? Must find someone to let me try one day..........

Pretty much all Turbo owners have at least one "stepping out" story. Fortunately most are a learning experience, but occasionally it ends the ownership quite abruptly. You have to force the issue or be on a slippery surface though; they can't break traction at speed on a good, dry surface just by opening the throttle.

I agree on Mik's point except, being a pedant, I think his offsets are the wrong way round; if the car is a pre-ABS model then it needs an offset in the 20s and if the wheels have one inthe 50s then that is the problem (and it needs a 30mm spacer. On the other hand if it's an ABS car then the wheel must have an offset in the 50s or even 60s or it would be sticking out Carlos Fandango stylee rather than hiding like a nervous teenager under the arch.

 

[mik_ok]

ORIGINAL: Fen

I agree on Mik's point except, being a pedant, I think his offsets are the wrong way round

Gaah! Fen is of course quite correct.

I have the same problem when I see my bank statement every month as I punch the air and (homer) woo-hoo ( / homer), only to realise.... []

 

[swright]

Thanks for the info[]

My car is indeed pre ABS and also has the alloy front arms if that makes any difference. I didn't get a chance to check the width and offsets as its dark when i go to work and dark when i finish.

The steering does feel way to light and floaty, infact its terrible. And has got worse since i put new tyres on the back so i badly need to sort these fronts out so i can get all four tyres matching with nice new rubber and get the car handling like it should [8D]

So depending on the width of the rim and obviously some spacers, i should be able to fit 225/45 17" without a problem? Also do i need to get longer studs to match the spacers, so say, 30mm spacers would mean 30mm longer studs?

Ta,
Stu

 

[James_G]

You'll hate me for saying this, but you can't beat a nice set of D90s. You'll no doubt get plenty of ££ for your current wheels on the 'Bay once you've sourced a pair. Saves all this problem with spacers and the like.

 

[mik_ok]

James - D90's were only ever made for late-offset cars, so no use to solve Stu's issue.

I always did like D90's but the S2's sit too far inside the arches for my eyes - particularly at the rear. 15mm rear spacers and 7mm front shims made a huge visual improvement without affecting the handling.

Stu - proper spacers bold onto your hubs, and the wheel then bolts onto them, so no need for longer studs.

 

[James_G]

Ooops.

Must read all the posts before replying, must read all the posts before replying.[]

ORIGINAL: mik_ok

James - D90's were only ever made for late-offset cars, so no use to solve Stu's issue.

I always did like D90's but the S2's sit too far inside the arches for my eyes - particularly at the rear. 15mm rear spacers and 7mm front shims made a huge visual improvement without affecting the handling.

Stu - proper spacers bold onto your hubs, and the wheel then bolts onto them, so no need for longer studs.

 

[944 man]

Going on the picture, as many have already suggested, you have late offset wheels on an early offset car. A cheap solution would be to contact a breaker and buy a set of early rear long studs and spacers. Many 'Porsche breakers' now are chancers so beware: I wouldnt pay more than a few pounds for the lot. Even when the cars were valuable these parts were worthless...

 

[Fen]

If you resubmit your post replacing D90 with Fuchs, and technically I guess removing any suggestion that it's a cost-saving option, then you would be 100% correct, James.