Is the most common length for a wheel stud for fuchs rims 45mm? Are the rear lugs supposed to be longer at 52mm, or are they also 45mm?

Also, why are wheel studs 7 dollars a stud? Have to buy 20 studs, 140 for studs is a little crazy

They are any length you want them, or better yet, you need them.

I tried several different lengths and finally just got tired of running out of thread so i got a set of 100mm wheel studs all around.
Now i can run any spacer combination i need (different offset for street and track wheels) and not have to worry about thread engagement.

The 100mm studs are ~$10 a piece ...
Andy

Are you running GT flares? If you are you may need longer ones because you will want to space the wheels to match the flares.

I will be drilling my hubs for 5 lugs as well so any info added to this thread will apreciated by me also .

Sir Andy, do you use the open ended lug nut for the 100mm stud? I have a set of, i guess, closed end lug nuts for the fuchs already and plan on using those. I really don't want to spend 200 on studs, but if thats what has to happen then i guess ill have to deal with it, kind of shocking when a stud for my pontiac is 1.49

PET/ETKA says front and rear are the same part number, which is also the same part number for contemporary LWB 911 front & rear.

They are good-quality steel, with several machining operations, and they are heat-treated. It would be bad if more than one broke without you noticing it...

Like Andy, I just bought a batch of 100mm studs, but as I bought them from a guy with a lathe and a toolpost grinder, had the 'NASCAR' ends ground on. This accomplishes not much from a practical standpoint but they do look cool...

If you want stock-length studs they should be available in abundance in the used market. They come 20 to a car no matter the condition of the car. Lots of people press out the stockers and go to longer studs. Check the used-parts purveyors if you need a bargain, but understand you'll be paying for the cost of removal, packaging, and shipping (they're heavy) and you wind up with a used part of unknown provenance.

Upgrades like 5-lug conversions do not respond well to corner-cutting. An unplanned repair is one thing - something you budget and schedule for on purpose is not a place to be scrimping on essential parts. (MHO)

Yes ...

Crappy pic, but you can see them:

Longer studs don't work well with some spacers. If you have a thicker spacer 1" or more, the spacers come with studs pressed in for the wheel. The studs you purchase in this case should not stick out more than one inch past the rotor flange.

I wouldn't buy bargain studs from anyone. I installed my long ones 15 years ago and have never had to replace one. GT flares and big spacers up front for different wheel offsets forced me to install very long ones. Good return on investment, maybe $7 ea. back then for 100mm studs and getting cheaper by the year.

If it's a track car it doesn't matter, but if it's a street car and you want to use BBS wheels, or any with center caps, the cap won't go on if your studs are too long.

I think the spacer referred to with studs installed into them are usually adapters from 4 to 5 stud... not allowed on the track.

No, they are spacers. Seems safer to me to use shorter studs with spacers that have the 5 lug offset ( 5 bolt through to hub, the other 5 hold your wheel on). The ones I bought are hubcentric for the front anyway, but are made out of 6061 aluminum. Not cast. These will be stronger than most aftermarket wheel centers.

Interesting. I wonder if those are legal for the track. From an engineering standpoint I don't see much of a difference.

Every opening in a piece introduces a potential stressor. These holes are round so it's as good as it can get, but there are 10 instead of 5 with the offset, maybe several landings for the nuts, and maybe more weight as well. On the street it may not matter for sure.

None of this helps with your original question though.

I just went through my studs and don't have any stock ones to measure, so I'll not hijack the thread any further. Cheers

Good luck!

The car is definitely for street use and maybe cruise nights around town. the whole reason i want to get the 5 lug conversion, besides being able to use my fuchs is to remove the wheel adapters that are on the car. Ive read that most tracks that have track days don't allow the use of wheel adapters. Sooner or later my car will be at a track day, just for fun.

I would see the spacer with the studs installed similar to a wheel adapter.

You would have more leverage on the stud the further out you go with spacers. I would think anything under 1/2 inch wouldn't produce much more side load. I have not run the numbers yet to determine dynamic stress differences. The same question was brought up with grade 5 studs vs. grade 8 studs. We found if the nuts were torqued to grade 8 specs and kept there, they were stronger. If the nuts came loose, grade 8 didn't allow for flexure as well as the grade 5 did without braking.

SO....keep your nuts tight !!

That's how the factory did it.

In fact, most consider the bolt on spacers you describe as unsafe ...
Andy

I'm pretty sure a short 2.0 inch stud into a billet adapter or spacer with another short 2.0 inch stud into a forged wheel is as strong as a 4.0 long stud through both, the thing I don't like is the inability to check the torque of the inner nut without taking the wheel off.

My recollection is that there were some factory parts made just that way, although I can't find them in the PET/ETKA just now. Might have been from something like a Turbo-look or somewhere around the transition to the ultra-negative offset wheels of the 964 series.

But - there are good ones. (There is also junk, which will never be safe...) But the H&R stuff available from the usual suspects comes with a TüV rating and is quite good. I've used them on my SCCA AX car and once I finally got the right combination of width and lug bolt (this was a lug-bolt car...) length had zero issues even with BIG slicks.

In that setting, inner bolt torque wasn't an issue because they were never on the car more than a day at a time - changed back to street tires for the drive home and yes, that did get old in a hurry... But I never had any issues with the inner bolts loosening and yes, I did check them before dismounting.

AX cars pull as many G's as track cars although of course for much less duration.

I think I would trust an H&R (or Porsche factory) 5-lug bolt-on spacer, especially in a street setting, and especially if one were careful to re-torque the inners until they quit moving. AX too. (This does not constitute a specific recommendation, of course...) I would *not* trust a 4-->5 adapter because of the spacing and geometry, but a like-->like spacer with high-quality fasteners could be OK IMHO.

If they're specifically prohibited by the rules, then it doesn't really matter how safe they may theoretically be. I understood I was operating in a grey area and had zero issues, but my experience may not be universally transferrable...

Actually I am not sure I understand the physics of that statement. I think it's the change (if any) of the location of the contact patch with respect to the hub that maters more than anything.

I think you generally have two forces on the studs. Shear (i.e. the wheel trying to rotate against the hub) and tension (the wheel trying to pull away from the hub). The loads are created via the tire contact patch. Take the example of two different wheels with the same width, but different offsets. By using a spacer on one wheel to create an equal offset for both wheels (both will have the same track) the loads when measured at the hub (tension and shear) should be the same between the two wheels regardless of stud length.

Now if you are moving your contact patch out and creating a wider track then the loads on the studs at the hub should increase. But I don’t see the load on the stud at the hub being any different with bolt on spacers vs. spacers that use longer studs. My fear about bolt on spacers is that they hide something that can come loose. I think it would be easier to check torque on long studs than having to deal with removing wheels to periodically check the torque on the bolted on spacer.

What I am curious about is issues such as hub centric spacers vs. lug centric spacers and the differences with respect to shear loads on studs. Particularly on wide spacers. In general bolts (in this case wheel studs) should not be used as a centering device. But there is the reality of the lug centric design that uses studs to center wheels. I don’t know if they exist, but I would think the most flexible solution would be hub centric spacers that work with long studs.

Yep, the 930 did that for years. You'll get an arguement about it on the bolt on spacers from users who have never had a problem.... but most AX, DE and TT rules prohibit them while allowing long studs and slip on spacers.

On closed headed bolts....they not only don't allow race scrutineers to count threads but tend to crack and leave a collar on the stud. There are more than a few threads on the subject.

Swear words and the use of a hole saw are the primary comments.

is that 45mm the thread length (T)?

L

The rear bolt flange is steel while the front hubs are thicker cuz aluminum. That could explain the difference (but 7mm? hmm)

Here's the rear hub of my '86 930. Not sure how long these studs are.

Had to pull the hub since the inside bearing blew out. I listened to the whining a little too long.

Click to view attachment