Clearance on 3.5" Prostars?

I'm trying to install some 15 x 3.5 Prostars on the front of my '95. I found that they hit the small metal tabs on the back of the outboard brake pad. I tried putting in some spacers and it clears, but doesn't leave enough stud to have good thread engagement on the lug nut.

Has anyone broken these tabs off, or bent them down?

Mike

no dont break them off u are going to have to get longer wheel studs....

Its all covered in the FAQ.

I read the FAQ thoroughly before asking the question. I don't want to run spacers because you need extra-long studs. 90% of the time, I have the 17" SS wheels installed with closed-end lug nuts. It would look stupid with extra-long studs and the 17's. The 3.5's are for track use only. If I could grind off the metal tabs without causing any brake problems, then it would clear - at least in the current state of brake pad wear.

Mike

You have to remember that the caliper position moves laterally as the pads wear. What fits now might not fit later, with thicker pads. A buddy of mine measured carefully, fit it all together, and one day the wheel caught the spring and ripped the pad out. Didn't do much good for the wheel, either.

There's also potential for contact with the large horizontal bar on the steering knuckle that the calipers rest on. That can be ground slightly, but take off too much and you run the risk of the caliper sliding off the bar when the pads are replaced.

Yes, the longer studs can look bad, but simply by cutting the unthreaded extension off the 2.67" studs can minimize the problem. I use a "duplex" acorn for the rear, and that completely covers the longer stud, but my rear studs are 1/2". I haven't been able to find a duplex acorn for the 12mm studs in the front.

http://www.injuneer.com/images/photos/WheelsTires/Backlugs.jpg

cant you just use a open end acorn style lug nut?

Sure, but the stud sticks out about an inch past the end of the nut in the front.

i think that looks bad ass in my opinion.... makes another driver think y does this fool have harden studs.....:confused: maybe it is a fast ride!!!:bow:

I drilled and tapped the closed acorn studs that came with my ZR1's, and when I bolt 'em on it really doesn't bother me that the studs are sticking out. I think when people see a car with a roll bar, a 5" tach, and hear the clatter of the solid roller cam and the (almost) straight pipe dual exhaust, they understand why the studs stick out.

I think when people see a car with a roll bar, a 5" tach, and hear the clatter of the solid roller cam and the (almost) straight pipe dual exhaust, they understand why the studs stick out.

True, but my roll bar is hidden, all the gauges are stock, it has a baby hydraulic cam, and the exhaust is quiet (turbo and Magnaflow). My car looks and sounds nearly stock and I like running 14X mph in the quarter like that.

I took some more measurements today.

When using a ProStar and no spacer with the long shank-style lug nuts, you get .700"+ of thread engagement with the stock studs.

With steel studs and nuts, you really only need 1 stud diameter of engagement for strength, regardless of how the NHRA rule book is written. Any more is pointless because the stud will break before the threads pull out.

Anyway, when using a .250" spacer, I get over .450" thread engagement which corresponds to the .470" stud diameter. Since my clips are just barely scraping the rim and the bar doesn't hit at all, the .250" spacer will give me plenty of clearance and adequate thread engagement. I'll just have to be carefull and recheck things when I install new brake pads.

NOTE: I am doing this at my own risk based on my knowledge of bolting. Do not try this at home.

Problem is I was not allowed to race with the stock studs.... tech insisted that the rule book be followed, and thats one diameter in the hex portion of the nut.

I'll bet the rule book was written in the most conservative fashion, where it assumes that all lug nuts are conventional nuts. In that case, you do need 1 stud diameter in the hex portion of the nut. However, acorn nuts have extra thread engagement in the tapered portion and shank-style nuts have lots of extra threads in the straight section below the hex. It would be nice if the rule book just said you must have 1 diameter of thread engagement...

The problem is in the way NHRA defines the requirements in the book.... they show a shank type lug, with the one diameter clearly starting at the outside face of the washer (Sect 16 5:2). Conservative or not, when "tech" can point to that diagram, they have all the cards.