Planning To Upgrade 89' C4 Wheels and Suspension
 

I'm planning on upgrading the wheels and suspension of my 89' C4 which I track about 10 days a year but still want to be reasonably comfortable in when driving around town.

Any opinions on wheel diameter? Can (should?) I go with 18" over 17"? Can the rears safely accommodate 10" wide wheels with the help of spacers?

I've read 'Wringing Out I-III'. Does anyone have any recommendations on shock and spring combinations for my particular application?

Will a lowered 89' C4 be able to accommodate 18" diameter wheels, 8" wide in the front, 10" in the rear (with spacers)?

Please forgive my naivety, this is my first Porsche of which I've only owned for a few years, completely stock.

Thanks for your help.

Can O worms . Go as fast as you can on the stock rims and suspension . When you are faster than the stock rims / tires and suspension , then upgrade .

My personal opinion is to stick with 17" wheels, makes the ride tolerable and tire replacement relatively inexpensive. For suspension I would go Bilstein HDs (make sure the rears are correct for your model year) and H&R springs. Get an alignment and corner balance and you should be in good shape. You can also get larger sway bars, Porsche used 22 mm front/20 mm rear for the C2/C4 M030 sport suspension. Stock for the 89-90 C4 are 20/18

Upgrade to a different 911 or upgrade rims/tires? Been running in the White run group now for a couple of seasons, definitely faster than the stock set-up is allowing me...

17 with ra1s

There are plenty of opinions on wheel diameter... I have 18's and love them. Previously had 17's and noticed only a slight increase in ride harshness until...

I installed KW Variant 3 suspension and lowered it between RS and Cup height. Replaced the rear roll bar with a C2 bar. Now quite stiff and a little harsh for the average street driver but blindingly quick through corners and very neutral. I can squeeze 10' in the rear with the current ride height but i'm running a bit more negative camber on the rear approx 1.7 deg

In my opinion just the wheels themselves will not adversely affect your ride comfort but will give you a lot more predictable breakaway when the the rears start to slide.

Regards,

Neil

Whatever wheels/tires you choose, make sure you buy them, first, and have them mounted on the car when you install the new suspension and car lowered.

kgorman's suggestion sounds like a good one: 17's with RA-1's.

Tyre sidewall does make a diff in ride harshness as you're losing a bit of "give" in the flexible rubber wall by going up 1".

But, from personal experience, if you lose weight in the tyres (i.e. the Conti CSC3s are one of the lightest in the class) and the rims (such as the OZ Allegeritas, which lose abt 8 lbs in weight each compared to Cup 1s), you can get a better ride despite going up 1". TireRack has a very good online tool to compare tyre weights.

My A6 went from heavy OEM Avus 17" rims to light MTM Forged 19" Bi-motos, and my ride improved. Really.

Incidentally, I've been in contact with OZ abt the Allegeritas in 18", and with DPE abt forged monoblocks in 17".