1/2" Wheel Studs for Racing

Why and How to upgrade to 1/2" Wheel Studs for Racing Purposes

Date: Wed, 06 May 1998 10:27:42 -0400 (EDT)
From: Bob Lang
Subject: Re: Long Studs and Sticky Tires

> On Fri, 01 May 1998 06:02:10 -0600
> "Janssen, Lee K" wrote:
> To: "'Lang, Robert M. (TR6)'"
>
> I was reviewing a TR6 e-mail and I wondered if you had started the
> following thread:

Frankly, I don't recall if I did start this one, but chances are that I did.

>> Somebody else wrote:
>>Robert,
>>Why go through all that trouble? 7/16 studs are plenty strong.

> I disagree. 7/16" studs are not strong enough for racing purposes
> on sticky tires which is what Bob does with his TR-6.

I agree with your disagreement.

The tires nowadays are way stickier than they were not too long ago. In fact what passes as a DOT approved tire for SCCA autocross now is probably stickier than the compounds that were used for slicks ten years ago. Tires have come a long way.

Now, take 7/16 studs, super sticky tires, old narrow wheels, metal twist, tiny wheel bearings (especially the outer front wheel bearing), various "end float" compontents (as in wheel bearing "pre-load") and even the torsional strength of the hubs and front spindles... there's a lot of room for twist.

A lot of these components cannot be changed if you run street prepared, but from what I can figure - you can change the lugs (because the wheel specs are "free"). Besides, I can always argue that this mod is a safety issue. They cannot disagree with that.

I take my tires on/off at every event, this in and of itself can fatigue the metal of the studs... especially if the studs are "dry". You do use anti-sieze on your studs and lug nuts, don't you???

So, after playing at maybe 50 or more autocrosses, I've seen some pretty bizarre stuff happen. The last autox I was at, a guy in a Scirocco had a brake rotor fail - ever try to stop a car in a straight line with only one front brake working??? My goal here is to be ahead of the curve as being behind the curve can be way more expensive. Last year, I saw three dramatic suspension failures - wouldn't you know it that one was because the studs sheared off under braking.

I'm going with fatter studs.

Also, the wheels that I picked up for this purpose have really fat center sections - more than an inch! This also means that I have to go to longer studs. I figure that if I'm going to longer studs, it makes sense to upgrade to fatter studs. I like to say longer and fatter is more betterer. Yes, I know its a triple comparative.

> If so what does it take to upgrade to 1/2 inch studs?

It takes a lot of work.

The fronts are easy. Pull 'em off, clean 'em up. Find someone with a vertical milling machine (I prefer Bridgeport), and ream the holes out to the new diameter studs. I bought Moroso 1/2-20 studs that are three inches long (roughly an inch and a half longer than stock). The trick here is that the knurl diameter is .615 inches. So, in my case, I had to obtain a .615 reamer - the shop where I got the work done did not have one. I can't complain though - the labor was free! I did have to use a hydraulic press to get the studs seated, around 2000 pounds of pressure was required.

The rears are a freakin' pain. First, you have to yank the hubs apart. This is not a job that should be taken lightly. I happened to have access to the "churchill tool", and it took roughly one hour per hub to separate them. The upside is that this job was somewhat similar to an hour "pumping iron" at the local gym. So, I got to work on the car and workout at the same time!

You might ask - why separate the hub. The short answer is: you can't get the long/fat lugs past the part of the hub assembly that is the "outer race" for the wheel bearings. There just is not enough room to maneuver the stud into place so that you can press them in.

So, I've not actually finished this job as of this writing - I said the labor was free, but a possible drawback to free labor is that it gets done when time is available... the guy doing the work is very busy right now.

At any rate, when I get the drilled out hubs back with the new studs installed, I then get to reassemble the hubs and check the end float and all that.

It's pretty complicated is the short answer.

rml

------

Date: Tue, 12 May 1998 16:35:14 -0400
From: "Robert M. Lang"
Subject: Re: TR6 Rear Hub Studs

Hi,

As for driving with only three studs - it'll work, just don't Autocross with it! ;-).

For installing the lugs, you need to understand that the lug holds due to the knurl pattern on the replacement lug. If you could just tap them in, they would not "hold" very well when you torque them down. In machinist lingo, the hole for the stud is reamed to an interference fit for the "shank" of the stud. The knurls actually stand proud of the shank and are pressed in to the hub with a substantial amount of force.

By way of example, I recently installed some bigger studs on my TR6 and we needed to use around 3000 pounds of force to get the studs seated. Granted the studs I'm installing are considerably bigger than the stock ones, but the bottom line is: you don't tap them in.

One thing to keep in mind when you follow the prescribed method: the shank is a bit wider than the threaded portion of the stud. Make sure that your washers allow for that little extra diameter of the stud when you tighten down. The reason is that the shank will stand proud of the hub by a little bit, and if your washers are too small, the stud will bottom on the washer before it is fully seated. You'll notice this the first time you mount the wheels to the recommended torque and 5 miles later all the lugs are loose! really!

the other thing with the rears is that the flange for the hub that bolts to the trailing arm really interferes with getting a clean blow to the head of the stud. And if you miss, you'll wreck your hub... guaranteed.

And make sure that you pull straight when using the washer method. If you do not, you can bend the hub flange. I've been down that street, and it ain't pretty!

later,

rml
TR6 - with mondo studs!