newsboy

I've purchased a set of 17" (55 offset) 7" & 9" wheels for my C4. I'm getting 255/40/R17's for the rear. I was thinking of getting 205/50/R17"s for the front.
To decrease understeer, would it be better to go with 215" in the front. If so, would these be 215/40's to maintain the aspect ratio?
Thanks

ilko

225/45/17 would be the correct tire size for the front.

newsboy

Sorry,meant 215/50/R17's for the front.

DAVISRILEY

That's what I went to for summer tires. Seemed to help a bit.

Seight

Although increasing the width of the front tyre will make a small improvement to your understeer in the dry, it will make your understeer increase in the wet. The wider spread of weight will allow the tyre to aquaplane sooner than a narrower tyre would. I prefer the 205/50/17 on the front for this reason, with a touch of extra negative camber. Just my opinion....

Best
Alex

tbennett017

Newsboy,

Though I am only partially informed, I have a few comments...

Tires will only go so far in changing the understeer condition, as it is engineered into the car to behave that way... the diffs do all the work and the rear axle will lock together forcing this to happen. It is a powerful force. I also recall reading here about some driveline elements failing (planetary gear in the differential) and the repairs being really expensive. I wonder about going to a different tire size...since it might (and only my opinion here) cause unnecessary planetary gear stress - fronts having a different diameter (if only even slightly) though I might be all wet, as the wheel sensors/PDAS are likely to freak out if they are rolling at too much of a difference anyway... Just random thoughts to ponder.

I recently upgraded my suspension, going to Bilstein HDs HR Greens, and the cool part, the RS adjustable swaybars. This combination (with a careful and skillful setup by Steve Wiener of Rennsport) has brought my C4 under control. Handling is neutral, with a beautiful live feel closer to the limits, where before there was the heavy understeer going on: Fighting the PDAS all the way around tight turns. Now the car can be pointed with the throttle, yet I haven't lost the confidence of AWD in bad weather. Neato...

I know its a lot more of an investment, but I really wonder what tires will do, versus a possible risk to your driveline.

There is also a "Wringing out the C4" article (search...) that was a contemporary serialized article (1990 vintage) about how to dial out that understeer, with lots of good recommendations. They do mention a larger front tire... so I might be wrong about my concerns...

I recommend you touch base with Steve W at Rennsport too. He really knows how to do this. 503 244 0990

dfinnegan

Wringing Out the C4

tbennett017

Exactly, Thanks!

MorganB1

Several years ago, I followed the 'Wringing" article to the letter on my first C4 for street & track use and I would say that the 225's up front and then upgrading to a stiffer 21mm stabilizer in the rear (stock C2 is 21 or 22mm & stock C4 is 18mm) will remove over 50% of the understeer handling woes. I didn't even lower it from std suspension and still the improvement was noteworthy. Add a front strut brace, lower it and you'll really bring the C4 a long way towards the handling you desire.

Also, Tom's right: Steve W. is fantastic and will get you there in a hurry...

my 2¢

sleder

Dave Thanks for the article!

Livefreeandrive

Awesome!!! Thanks so much for all that info!
Steve

newsboy

Thanks for all the feedback, and what a great article about understeer.

kgorman

+1