astock165

93 Coupe, dedicated a/x & TT car. Put in Z51 springs and lowered the car approx 1", added adj swaybar endlinks and hiem jointed rear suspension links over the winter. Also went to a square 315 Kumho V700 tire setup.

With the ZR1 11" wheels the tires stick out 1" on each side and there is approx 1" of clearance before the tire rubs the fender.





Question 1: would I better off raising the front ride height and continue running a 315 square setup or keep the ride height where it is and running a 275 tire up front (assuming that going to a 275 alone will solve the problem)?

Question 2: with the 315s up front I notice that maneuvering at slow speeds and during very quick direction changes (i.e. tight a/x turns, Chicago box, etc) it almost feels like the power steering gives up for a second and then comes back ... is this common? Due to the wide relatively soft tire up front or is my PS not able to keep up? I'm running RedLine PS fluid but it is a couple years old.

TIA

urtoslo

I don't run 315's up front, but if I'm low on fluid, it acts like that. Is the fluid in the reservoir up to the full mark? Is your belt tensioner working?

gkmccready

How much camber are you running? I had to go to about -2deg up front to pull in my 295mm on 18x11 CCWs on my C6.

John Shiels

your tires will hit the fenders

astock165

The fluid is up to the FULL COLD mark. I'd have to check on the tensioner, I didn't think of that.

About - 1 3/4 (approx). That's all I could get and keep the two sides even.

Thoughts on the 275 vs 325 front size question?

Kanmer

Do you hear a whine from the power sterring pump? At speed? If you run oversized tires on C4's its hard on the pump. Call Turn One and tell them you need a pump set for your setup. I did (thanks Ralph) and it was about $300 and it solved the P/S issues.

It appears your tires will rub in current setup.

Bob

BrianCunningham

Does your car have a PS cooler?

If you do, the way the stock cooler is mounted is stupid. It really doesn't get enough air flow.

You have an aftermarket spoiler on your car. Is it deeper? If so, this could be impeeding airflow even more.

I'm running 335's up front, my reservior overflows, but that's more from the G-forces kicking it out. The steering does actually kick out at all.

My tires don't hit, except for when I'm on the locks, but my car is at the stock ride hieght.

Diesel68

I ran 315's on a lowered C4 and it did not rub. I did have a 32mm front bar and a 1366 VBP spring. I had a problem with the rear tires bottoming out inside the wheel well, but it never rubbed the fender lip. I installed a heavier rear spring and that solved the problem. The car also handled beautifully.

Change the fluid to Lucas Power steering fluid. It solved most of my steering problems. I was surprised at how well it works. A change of the pump though is probably the best fix.

astock165

All good points, looks like I have some more work to do.

Does anyone have an opinion on the raise w/ 315 vs. keep w/ 275 question?

Solofast

On our BSP car we were running 315 Hoosiers, lowered, but Larry put in more negative camber (like 2.5 deg). Still, we kissed the inner fender lips on occasion, but it wasn't a big deal.

Put in a set of offset lower bushings to kick out the bottom of the tires and that will pull the top in some, or get a set of offset top bushing made up...

Zpeedstr

using VBP extreme spring lowered so that lower a arm is level
filed the fender some to clear tire

get lower volume (60%) geroter in ps pump to lower high rev overheating
(note vette ps reverse rotation)