What Length for Wheel Studs?

[1stgear]

I want to change my front wheel studs to match the extended length on the rears. This is a M491 turbo-look car that has the spacers removed on the back wheels. I want to get that long stud length look on the front to match the back. I don't know what stock length is and what I need to order. Any help would be appreciated. THANKS!

Front:


Rear:

[Joe Bob]

Knock one out, measure and get some that are 10-15 mm longer. You on the right path using open headed nuts.

[Jesse16]

Maybe you can pick-up the stock length off our hosts new parts list of the PET Katalog. Then just order studs at least 15 or 20mm longer. Your rear studs look easily 30 mm beyond stock length, little too long for me unless you have some wheels that use it. Or just look at whats available for your year and go 30mm plus the shortest length (which is likely stock). That's how the 87's lengths are in pelican.

[tdw28210]

FWIW, I think I read each nut needs at least 8 full turns before it is seated to be considered safe.

[Jesse16]

The head of the bolt should reach to be even with the nut when open at minimum, some groups would not let you on the track at a DE like that in front if noticed. For all nuts and bolts the rule of thumb back when was 1.5 times the bolt diameter is the length of threads on the nut engaged in the pull. Stud is 14mm dia. so nut should be minimum 21 mm and have threads engaged the full distance. You're wheel nuts are longer than that by a bit most likely. A 14 mm bolts thread pitch measures 1.5mm (metric fine) so 7 or 8 threads would only be 12mm threaded, doesn't sound like enough.

[KTL]

The original front axle studs on a 930 and M491 are 65mm length. So it looks like you need the next available length, which is 72mm, to get your studs to have enough threads engaging the nuts. But even with 72mm, you won't have the studs sticking out as much as you'd like for the appearance.

In the rear, you removed the 28mm thick spacer. So you've got ~28mm of stud sticking out back there. I say it's 28mm of stickout because I the old Porsches typically have the studs flush with open lug nuts. So if you want 28mm of stickout in the front to match how the rear looks, you need 65 + 28mm = 93mm. Get the 100mm studs.

100mm are really long. I have them on the rear of my SC widebody racecar. Does your front wheel installation have a spacer? I'm curious because on the M491, the front axle hubs are the later 930 extended style which then eliminated the wheel spacer used on the earlier 930 front axle.

[1stgear]

Thanks for all the quick replies and knowledge shared, guys!

Does your front wheel installation have a spacer? I'm curious because on the M491, the front axle hubs are the later 930 extended style which then eliminated the wheel spacer used on the earlier 930 front axle.

Kevin, you are correct - no front spacer. I wish there would have been so I could have gone deeper on my outer offsets.

[KTL]

OK thanks for clarifying. I'm surprised your studs in front look that short without there being a spacer behind the wheel. Maybe the number I pulled from the PET diagrams is incorrect about the stud length for M491 and 930 with the later extended hubs.

Can you take the front wheel off and shoot a picture of the studs? Then we'll know right away how long those studs are, approximately. My point is, I feel like those Fifteen52 wheels on the 930 extended hubs should have a good bit of stud sticking out of the lug nuts, if the studs are in fact 65mm like I assumed.

[Busta Rib]

Nothing to add here other than...awesome wheels, Chad! Nice work. Post up full body shots once you get the new studs installed. The fronts are easy to replace.

[1stgear]

Can you take the front wheel off and shoot a picture of the studs?

Hey, Kevin. If the weather holds off, I'll do that this weekend.

ost up full body shots once you get the new studs installed.

I'll do it, Jim! Thanks for the compliment on the wheels. I've been watching your build thread. Your car looks GREAT!

[RichardNew]

Here's an article I wrote a few years back about wheel studs and nuts.

"Over-torquing the wheel stud is common because so many people insist on using impact wrenches. Using an impact wrench to install wheels can cause the wheels to have three to five times the specified lug nut torque. The use of lubricants and anti-seize compounds on the threads can cause an even higher degree of over-torquing."



Richard Newton

[1stgear]

Thanks, Richard!

[911pcars]

Probably been discussed before, but I would suggest applying some anti-seize between the dissimilar materials, both to ensure accurate torque and to minimize any galvanic reaction between steel and aluminum which, in some cases, makes removal of the al. lug nut difficult. Adjust tightening torque accordingly due to the reduced friction.

Sherwood

[hangar21]

I have these wheel studs that I'm not using, don't know length? I can measure & advise if your interested. Let me know ,
Terry

[panzerfaust]

Originally Posted by KTL

OK thanks for clarifying. I'm surprised your studs in front look that short without there being a spacer behind the wheel. Maybe the number I pulled from the PET diagrams is incorrect about the stud length for M491 and 930 with the later extended hubs.

Can you take the front wheel off and shoot a picture of the studs? Then we'll know right away how long those studs are, approximately. My point is, I feel like those Fifteen52 wheels on the 930 extended hubs should have a good bit of stud sticking out of the lug nuts, if the studs are in fact 65mm like I assumed.

m491 front studs are sometimes too short because the lug seats on the fuchs are really thin. some aftermarket wheels are thicker in this area hence less tread area for the nut.

my E50s are the same way. m491 like late 930s had built in spacers so you cant remove. are they 65mm studs on the late non 930 hubs?

[KTL]

Yep I hear what you're saying panzer about the thin hub area of the fuchs. I know exactly what you're referring to because I ran into a similar situation on the front of my '87 Carrera when I test-fitted some BBS motorsport wheel centers. The short 45mm studs barely stuck out enough to get a nut on the stud.

But with the apparent longer 65mm studs on the M491 front hubs, I thought there'd be extra stud. That's what makes me think the spacer-less front hubs on the later 930 front axle have studs shorter than 65mm. The built-in spacer that you refer to is actually the axle hub itself being pushed further out.

Here's the standard type of front axle hub



Here's the 930 hub with the "built in spacer" which is accomplished by the casting having the portion which carries the brake rotor and the studs pushed further out. You can see the studs are short on this set of hubs and I believe the studs are original




Late 930 Front Hubs

[1stgear]

Shop is putting new studs in. We went with 80mm from Elephant Racing. Here's a comparison of original vs. new. I'll get an exact measurement when I get the car and old parts back.

[KTL]

Yeah those original studs are definitely not 66mm. Thanks for following up with a confirmation of what size the originals are.

[1stgear]

Sure thing, Kevin. Here's a shot of the final product. Sorry for the dark shot. Took it in my garage while I was home for lunch.

[KTL]

Good choice on the length. Stick out enough to look purposeful and also make hanging the wheel on the hub easier.