I'm getting ready to order my 1st set of Hoosiers for autocrossing my new Z06 in SCCA stock class. It's a 2004.
What are the advantages & disadvantages to the wider tires. It looks like the front will fit either a 275 or 295 wide. The rear wheel should fit a 295 or 315.
On my old '94 Z28 I ran wheel spaces for the extra track width and saw some bennefit. The Z06 is much wider. Is there still bennefit to adding the allowed 1/4" spacer?
I am running the combination you are talking about but only at the end of last season with two races on them. I felt that the 295's over the 275's allowed me to run more air pres with more grip. The car felt more precise, hopefully I will get more runs out of the wider tires.
I am using the 1/4 spacers with the stock studs, is this really going to be a problem? I hand tightened the lugs nuts on the first time and felt like I had plenty of thread. But I would rather pull them off than risk a problem.
I would verify very, very carefully how many threads you have engaged on the lugs. The end of the stock lug has about 1/4 inch of non thread for ease of placing the lug on. The lug I believe is full threaded on the contact side & not on the side facing away.
My car is still unreachable in the car hauler, but before the first race I will pull them off and check them and I have 1/8" spacers (or none) and will replace them if ness until I can get the studs replaced if ness, THANKS
My car is still unreachable in the car hauler, but before the first race I will pull them off and check them and I have 1/8" spacers (or none) and will replace them if ness until I can get the studs replaced if ness, THANKS
1/8 is probably ok, but still verify. 1/4 I would not do w/out longer lugs. Be safe.
Four turns of the nut is the minimum safe "rule-of-thumb".
I used a 1/4 inch spacer in my old car with stock lugs and had to constantly be replacing nuts because the threads were being pulled out. Before every event I'd loosen and torque the nuts and one or two of them would be gone. It was worse on the fronts than the rears.
Are the bennefits of the spacers noticeable? Has anyone compared times with & without or tried to compare with data acquisition?
Depends, in a word I would say yes there are benefits, but so slight that you would have a hard time doing back to back runs & telling the difference. Do the national guys all use them (or more likely a custom wheel built with the allowed offset), yes.
I figured on my car that 1/8 was probably not worth the hassle & 1/4 would require replacement of 20 lugs, also not worth the hassle. I had other things (not the least of which is DRIVER DEVELOPMENT) to do first.
Check your torque on the nuts EVERY EVENT as they can get loose.
Are the bennefits of the spacers noticeable? Has anyone compared times with & without or tried to compare with data acquisition?
When you can drive at the limits of the car, it'll make a difference. But being wider also has it's dissadvantages too...you'll hit more cones unless you take that "extra" wide line.
It also gives you something else to do to balance the car.
Widening the track by the allowed 1/2" (1/4" each wheel) has 3 benefits.
1. It will make the car more stable at lower speeds. (AutoX)
2. Helps reduce roll rate.
3. It helps correct the scrub radius back to Zero on a lowered car.
#3 is probably the most important, overlooked and understood reason if the car is lowered. A Zero Scrub radius is when a line drawn through the ball joints intersects the pavement AT the centerline of the tire.
Lowering the car, which IS recommended except for T1 suspensions, benefits the handling by lowering the CG and lowering the roll center.
However, lowering has 2 drawbacks:
1. It raises the ball joint intersection line on the tire centerline and moves the pavement insection point outboard. Thus the scrub radius is now +, not Zero.
2. Increases bump steer.
On a minimally lowered stock class car (SS) in which the lowering is ONLY made to the extent of using stock hardware:
- The correction of the scrub radius back to Zero can be made by using the allowed 1/2" (1/4" each wheel) allowance. This moves the tire centerline outboard to meet the ball joint intersection line AT the pavement and returns the scrub radius to Zero.
- The effects of bump steer are negligible on a car lowered in this manner.
- It is preferrable to use race wheels with the 1/4" wider offset built in, which are also stronger and lighter and thus avoid the use of spacer plates.
On a maximally lowered car, such as in ASP, using longer rear spring bolts and shorter front spring bolts and flatter recurve and higher rate springs, OR in SM2 with possibly a coilover suspension; the insecting line is moved even further outboard:
- You need to keep that 1/2" wider track
AND
- Use a wider tire/wheel to move the tire centerline out further to meet the intersecting ball joint line at the pavement which equals a Zero scrub radius.
- Bump steer may still be negligable at low speeds BUT will increase at higher speeds, rate of bump and rate of turn....so you may need to add Baer Tracker adjustable rod ends for hig speed track and even interstate driiving in a dual use car. These enable the tie rods to be brought back to parallel (level) with the pavement and reduces bump steer.
So the solutions of the lowering drawbacks (wider track, wider tire and adjustable rod ends) are simple and in effect, benefit handling and stability as well.
To determine IF you have excessive bump steer you will notice a "jerk" of the steering wheel when you encounter a hard bump. The "jerk" will increase if you experience the same bump at a higher speed. The "jerk" will also increase if the rate of turn is increased (try to hit the bump while turning sharper but at a constant rate).
You can actually measure and tune bump steer with a bump steer guage, adjusting other suspension parameters. BUT the first and easiest solution is to first get the tie rods back to parallel using the pin adjustable tie rod ends. That is usually all you need to do.
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My tire man says he can order extended lug nuts that will provide the thread bearing that is needed without doing extended studs. He also says that I need the nut threaded on the stud to be equivalent to the dia of the stud. In other words 3/8in bearing on 3/8 dia studs, 1/2 on 1/2 studs. Has anyone went this route? Pros and cons?
Thanks
Don
My tire man says he can order extended lug nuts that will provide the thread bearing that is needed without doing extended studs. He also says that I need the nut threaded on the stud to be equivalent to the dia of the stud. In other words 3/8in bearing on 3/8 dia studs, 1/2 on 1/2 studs. Has anyone went this route? Pros and cons?
Thanks
Don
I would switch to open nuts, so you can see how many threads you have engaged.
Found a solution that didn't require replacing studs. Used extended thread lug nuts that fit inside of the wheel and ad .3 in of thread which makes up the .25 in of thread lost. They require a 5/8 in. dia hole in the rim that the accs wheels already had. The stock rims were 19/32, which required me to drill out the hole a 1/32 of an in. The wheels don't center off of the stud through the hole but from the 60 deg conical edge of the lug nut so centering was no problem. This proceedure cost me $60.00, which has to be alot cheaper than replacing all the studs.
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