Andy Roe

My tires are getting near the time to be replaced. I'm currently running 205/50/17 & 255/40/17, and I'm thinking about going for 215/45/17 on the fronts in an attempt to decrease a bit of understeer.

The overall diameter of the 205's is 636mm & the 215's are 626mm. Will this cause me problems with the traction control in my C4?

The tires I'm planning on getting are Toyo Proxes TS-1's. Anyone out there that's unhappy with these??

Claude

Andy: Greetings from across the pond. I've got a C2 so I'm not sure if the set-up is different for C4's. I have the same rims you do--7 inch in the front and 9 inch in the rear. I run on Kumho's 215/45/17 & 255/45/17. The fronts rubbed on full locked turns and the rears rubbed a little less. I put on 1/4 inch spacers and solved the problem. Some of the tire purest will say this "set up" is wrong but I'm not a good enough driver to tell the difference (neither are they!). Hope this helps.

Adrian

Dear Andy,
215s suck on the front of a C4. Get 225s. 215s are too wide for a C2 and too narrow for a C4. I can assure you Claude I and many others could easily tell the difference. By installing wider tyres on the front of your C2 you have increased the possibility of oversteer which is not good seeing as the understeer of a C2 is not that great.
Ciao,
Adrian
964C4

PS: Andy you will need 5 mm spacers on the front running the Toyo T1S. I have these tyres on my C4. When I switch to winter tyres I really have to be careful until I get used to the understeer again.

Andy Roe

Thanks Adrian! Will 225's be OK on 7" rims? I've already got 3mm spacers on the rear - I assume that with 5mm spacers I'll need to get ones with studs included? Would they be 225/45's or 225/40's?

In your opinion, which do you think would be more effective in reducing the oversteer - wider front tires, or fitting a 21mm rear sway bar?

Thanks,

Andy

horst

Andy, I have exactly the set-up you propose: 215-45 front, 255-40 rear. I love them, no rub, and the handling is wonderful. I would worry about rubs with the 225s without mods/ stops. I do not need spacers or stops.

horst

Almost forgot my car is a 90 C4. The comparative diameter is within the allowable 6%

Adrian

Dear Andy,
I run the 225s on 7 inch rims as approved by Toyo. 5mm spacers do not need longer studs but do not go any thicker. You can try 3 mm. You can run without them but they may and I say may rub at full lock reducing full lock. You use the spacers especially if you do not have the 10 mm steering stops installed (factory 1992). I would advise the spacers.
The wider tyres and a 21 mm rear sway bar. If you drive your C4 as against transit in it you will find when hard cornering at speed that the front tyres tend to lose grip and the rear pushes the front into an understeer condition. The 215s do not help this situation at all but the 225s do. The greater grip (non of this is linear by the way) provided by the 225s massively reduces the understeer and resulting pushing.
Obviously it is up to you but I sincerely do not recommend 215s they are the worst tyre width ever made. They also gave me great problems on a 944.
Ciao,
Adrian
964C4

horst

Andy: My experience is different from Adrian's, obviously> I highly recommend the 215' front ,255's rear. The handling is outstanding. Note: I DID take Adrian's advice and put 21mm bar in the rear. Even before I went to the 17"s & lowered, that bar alone made an exceptional improvement.

Andy Roe

Well, thought I'd let you know that I've just had the Toyo's fitted & went with 225/45's on the front with 5mm spacers. I'm suprised at just how much tread depth these puppies have! Looking forward to seeing how they handle after a few hundred miles!

Andy

BrokeAss

I upgraded the rear sway bar in my 90 C4 Cabriolet and it made a distinct difference in the cars handling. Go with the wider 225 tires AND fit a bigger sway in the rear. You'll be a happy camper!

....I love the "bite" of the 225's up front, but mine rub at full lock or at the limits of suspension travel like hitting a pothole or driving like a goon full throttle up an off-camber on-ramp. (but none of the responsible citizens of this forum would ever do such a thing )

Andy Roe

Well it's been a couple of weeks since I fitted the 225's up front & I'm very happy with them. The turn in feels much sharper than before. Still thinking about the larger rear sway bay though!

Andy

puma1824

So the proper 225 size for a C4 would be 225-45-17 ?

If so does the sidewall look taller or shorter than the stock config of 205-50-17 ? I know traditionally the 50 is taller sidewall BUT with a wider tire does is get pushed up a little on the same width rim?

Anyone have a pic of the 225 installed up front? So 3mm or 5mm needed?

Thanks,
Puma

Rick964

The 45 or 50 sidewall size measurment is a percentage of the tire width, so a 205-50 and a 245-45 end up with (essentially) the same sidewall height and the same overall diameter or revolutions per mile. To the naked eye you will not notice a difference.

puma1824

Thanks!

So just to confirm I could/should run on my C4:

Front: 225/45/17

Rear: 255/40/17

-Puma

mckinn911

I am getting ready to do something very similar. I have a 1990 C4 (daily driver) - and love to autocross with the local club. After a few seasons on stock everything (learning about myself as a driver and the car) I am ready to reduce the understeer characteristics. I am now ready to make a few small adjustments... baby steps.

I am going to put on a factory 21mm rear sway bar thanks to Adrian.

I am still researching tires...
I have a set of 17 wheels for autocross use. I am leaning toward 225/40 front and 255/40 rear on Kuhmo VictoRacer rubber. From what I have read these sizes will produce good results.

Next step is the suspension - which i am leaning toward the factory euro turbo style setup.
Any thoughts / advice? After making the changes I will post my impressions.