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FB wheel studs

Old 10-07-09, 10:58 AM
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FB wheel studs

I run a Pro-7 car (82 FB) and found wrestling with the factory lugstuds to be painful, considering how often we pull wheels.
I bought a set of Gorilla 77737XL 12mmx1.5 - 2.25 inches in length studs and also use 12x1.5 bulge, open, 17mm nuts (I specified these in case other are looking for the specs). The car must run stock rotors (4x110) in either small or large bearing. We are not allowed any updating to -SE or later years.

I have compared my studs with others in my group and they are all identical. Frankly, the studs and their engagement in the rotor would cause Carroll Smith to roll over in his grave.
After seeing one of my friend's cars lose a wheel at the track it's evident that while these things might work on a street car (a big if) they are not properly designed for a race car.
The stud has only about 13mm of thread before the shoulder. The rotor has approximately 20mm of threads. This is unacceptable.

Most of us (not me as I abhor the spacers available) run spacers which moves the wheel far enough away from hub for it to lose hub centricity.
I think the issue with my friends car was that he had no hub centricity and because 0.5" spacers are hard to find, he runs 2 spacers. The clamp up loads may not be high enough on all surfaces for the wheel to stay put, the stud moves off perpendicular and simply pulls out of thread engagement.

I think a proper stud (for spacers) would be 20mm thread, have a 13mm shoulder for the spacer and then have threads for lug nut engagement.. I looked, but no one makes this size.
A really proper solution would be an adapter, but I don't think one could be made strong enough in the 0.5" allowed by the rules.
I don't think you can get a hubcentric spacer as there is not enough room to play with in the 0.5" unless you machined the rotor snout down. I change rotors much too often for that to work and then what about the rear?

What do you guys run (in Pro-7 or SRX7 or similar)? What's your experience?

Last edited by BossBill; 10-07-09 at 11:00 AM. Reason: spell
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Old 10-07-09, 11:59 PM
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My IT7/ITA Rx7 has always run after market wheel studs and I have never had an issue. In fact all of the IT RX7's I am familar with in this area use some from of a stud and I have not seen a failure on the track.

For quite awhile I used studs from Mazdatrix/Racing Beat and they are okay, just a little short. Since I wanted to use spacers to play with track settings I switched to longer studs. I went to Bildon - www.bildon.com - and bought these hardened racing studs in 75mm length:

http://www.bildon.com/catalog/Detail...10&SubNav=none

Very nice - the hex is well machined and there is plenty so thread in the rotor. The tappered nose makes wheel service a breeze and help avoid cross threading when you are in a hurry. They also have a shoulder for spacer/wheel alignment

I have also used these racing studs in 60mm length:

http://www.bildon.com/catalog/Detail...10&SubNav=none

They work fine but the material is not as hard and the hexes were not as well machined.

Regarding the thread depth of 13mm. Since this is slightly greater than the diameter of the fastner there is enough thread engagement. Keep in mind that the studs Bildon sells are primarily for IT VW's and BMW's that are heavier than our RX7's. Bildon races what they sell too.

I install my studs with red loctite and check them periodically for tightness. I change rotors often - the Hawk Blue pads kill them - so the studs are serviced often as well.

I have seen ARP studs pressed into FB rotors - ISC was selling a pair of them last year. But that seems like allot of work for a part that has a short life span.

On the rear I have used screw in studs - again with no issues. I did have make a "repair" on one axle that had a striped lug hole so I used ARP 12mm 1.5 press in studs. I will eventually apply the same repair to the other axle.
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Old 10-08-09, 02:31 PM
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Good feedback, Scott.

I'd feel better with press-in studs too, but with rotor life so short it makes no sense.

It's good to know that there is such a high success rate with these.
It's one of those things that just looks wrong.

I may have to try the Bildon's as I really like the snout.
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Old 10-09-09, 08:26 AM
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I have been using Mazda Comp screw in studs for 14 years with only one failure, and that was stripping out the thread in a front rotor.

I loctite them in place with red loctite.

I used to use spacers, but now I buy wheels with the correct back spacing and the correct centers.

When I used spacers, I designed my own, and they have a snout that keeps the wheel hubcentric (I am a mechanical engineer.) I designed the snout to fit the wheels exactly. I made different designs to match with different wheels, because most aftermarket wheels do not fit the 1st gen 7 hubs perfectly to keep things hubcentric. Yes, it is very expensive to custom design & machine parts to make things perfect, but I did the designing myself, and a guy on my crew is a machinist.
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Old 10-11-09, 10:16 PM
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I have 10 yrs of usng studs without a problem; I think red loctite is the key.
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Old 10-12-09, 04:48 PM
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Order my studs from Mazdatrix and used red loctite.
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Old 11-05-09, 08:42 PM
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Turns out one issue is with the Brembo rotors some of us use:
http://www.improvedtouring.com/forum...ad.php?t=26839
The guy in our run group who lost a wheel was using a Brembo.

I believe Mustanghammer posted this elsewhere in the racing section.

I'm not a real believer in the "this is slightly greater than the diameter of the fastner there is enough thread engagement" since the materials in the rear axle (steel) is not the same strength as the front rotor (cast).

A number of us here in the NW are looking at other metric suppliers or having some longer studs made to our specs.
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Old 11-05-09, 10:15 PM
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Originally Posted by BossBill View Post
Turns out one issue is with the Brembo rotors some of us use:
http://www.improvedtouring.com/forum...ad.php?t=26839
The guy in our run group who lost a wheel was using a Brembo.

I believe Mustanghammer posted this elsewhere in the racing section.

I'm not a real believer in the "this is slightly greater than the diameter of the fastner there is enough thread engagement" since the materials in the rear axle (steel) is not the same strength as the front rotor (cast).

A number of us here in the NW are looking at other metric suppliers or having some longer studs made to our specs.
Let us know what you find.

Couple of questions....how old were the rotors that failed and what kind of wheels/tires?

I used Brembos one time 5-6 years ago. I had no issues with them, but decided they were not worth the extra money because they wore out as fast as the cheap autoparts store rotors. I have since heard that the Brembos are light but I still can't justify the cost. I have been using Blackdragon, Autozone, O'Rielly's etc rotors....again, no issues with studs. I pitch them after the second set of pads has been run on them.

As far as wheels, I have Panasports and run Kumhos. Are you running steel wheels and Toyos?
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Old 11-08-09, 11:59 AM
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Scott -- I have no data on the age of the rotor. I believe it was from this year. Although the Carbotechs the guy runs make the rotors last much longer than with Hawks, they were certainly from this race season.
I like the way the Brembos look as the machining and castings all look first rate. Not like the Chinese crap (I had one rotor last an entire weekend). I used the Brembos early this year and they cracked just like all the other rotors. I'm currently running Aimco 3171 small bearing rotors from Canada. I ran the hell out of them in my last race of the season in ITA and ended up going metal-to-metal. No time for a proper break-in.
Other than Aimco I'm considering Centric rotors (at about $25 ea!).

Everyone in the Pro-7 group here in the NorthWest runs stock aluminum wheels with 185/70x13 RA1s or R888. I run the later and really like them. We could run steel wheels but are limited rules to the stock rim size, so we don't bother with finding alternate wheels.
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Old 11-09-09, 11:05 PM
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Wow, you guys really use your brakes! In 7 years of racing I have never experienced any of these issues and certainly none of the "one weekend and done" stuff. Must be a track issue....as in the tracks you are on go from really fast to really slow....allot. I can't even remember a time when I experieced brake fade at one of the track in the mid-west. I guess a big difference could be the 13x7 wheels I get to run.

About the only thing I get concerned about is bearing and spindle failure. I spend allot of time inspecting and repacking bearings. I always use National or Timkin bearings and swiched from the small spindle to the 84-85 spindle several years ago.

Any-who, always interesting to hear what others are experiencing. Keep us posted on your progress.
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Old 11-13-09, 06:06 PM
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I edited out the part about having to throw on some 50% pads without proper bedding.
Must have gone down the byte hole...

At Pacific Raceways (its old name was SIR) you enter T2 at about 115, then brake down to about 50. After T2 you go downhill at about a 12% grade and drop about 75 feet in elevation going from 100 to about 30 into a series of S turns. Brutal on brakes. I make up for my lack of racecraft by using the binders -- too hard according to some.

Since I change rotors like some change shorts I don't have bearing issues as they get packed during changeovers. I'm planning on having 3 sets of rotors next year with one set of bearings installed, packed and ready to install. I'm unhappy with my present lube and will switch to some Redline high temp red grease as my inner bearing tends to get toasty. The outer never seems to get hot and I wonder why everyone switches to big bearings as I've never had issues with the outers.

The only reason I can see going to big bearing spindles is if early rotors get any harder to find. I;ve heard about any spindle issues.

In the "damn this is weird" category, the post you referenced in the ITA forum was from my race buddy who lost the wheel!
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Old 11-15-09, 12:09 AM
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Day-Um! those are some extreme speed reductions. Yeah, nothing like that in the Midwest. The fastest track (the highest speed I have ever seen anyway) is Gateway in St L. I get to around 110 before brushing the brakes for turn one. However, since turns 1 and 2 are fast allot of braking isn't necessary. Even with a heavy car (heavy by IT standards) at 2470 I have never had a braking issue.

I actually buy new bearing and seals everytime I change rotors. I do keep a couple used sets packed and ready for use just in case. The fact that the inner bearings get so hot is why I change the bearings with the rotors. I have had good luck with Lucas and Amsoil greases. I think I am using Amsoil EP extreme moly grease at present.

Failures have been reported with the small spindle on the IT.com site in the past. Less so with the big spindle. So I switched for that reason. Also, it makes the migration to Production or STU easier. I never had an issue getting small bearing brakes, in fact they are cheaper!

I have also seen first hand a big spindle failure on an EP car. We believe that the spindle was cracked and had been that way for awhile before it finally let go. There were several clues with the alignment on that side of the car and the fact that there had been premature bearing wear on the spindle as well. Fortunately the spindle broke on of the slowest corners in the division. What we are going to do is have spindles magna fluxed and keep an eye on included angle measurements when we align our cars.
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