DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/22/24 12:33 p.m.

I bought my ND-RF with a front big brake kit already installed. It's a Wilwood kit with 6-piston calipers and the 12.88" rotors. I think (not 100% sure) the kit is the same from Flyin' Miata, Good-Win and Sakebomb Garage. Good-Win says I need 3mm spacers to use it with the stock wheels. FM says stock wheels will fit without spacers. Sakebomb doesn't say anything. This morning I took off one aftermarket wheel and tried a stock one to see how much thread engagement I have with the spacers on. To me, it looked like it should work without the spacer, so I removed it and everything rotated fine. I measured the caliper to spoke gap at over 4mm, so I think the wheels would be fine without spacers. Am I missing something? Or, am I just letting Good-Win's comment spook me?

Edit: I used open ended nuts to see the thread engagement and the studs don't come out to the end of the nuts. Should that be a concern? Longer studs would fix it ,as long as I don't bottom out the closed aluminum nuts.

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/23/24 6:49 p.m.

I suppose I could/should have checked the stock wheel on the stock rear brakes to see how much thread engagement is normal. A chore for tomorrow.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
6/23/24 7:04 p.m.

I ran into this on a 4th gen Z28 and was informed (possibly here) that as long as you have 4 threads of engagement, you're okay.

 

4 threads in a 12x1.5 nut is 6mm.  That didn't please me too much, being only half the stud diameter, so we installed longer studs.

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/23/24 7:40 p.m.

In reply to Pete. (l33t FS) :

I sort of expected the stud to come out to the end of the nut, and was a bit surprised when it was almost 3/8" short.

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/24/24 9:10 a.m.

Just to keep track of my thoughts on this, I'll add stuff until Keith chimes in. This morning I removed a rear Konig and fitted the stock wheel.

As you can see, the studs don't come out to the end of the nut. I measured the depth at 4mm on a nut that is 21mm long, so 17mm engagement. Then I put the Konig back on and used an open nut again.....

It was apparent that the nut had less thread engagement and it measured 7mm depth. The Konigs are 3mm thicker at the nut seat, so using the 3mm spacers with the stock wheels amounts to the same engagement . Now, I just want to see if Keith concurs that the spacers aren't necessary to clear the Wilwood calipers.

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/24/24 9:26 a.m.

I'll add that the OEM nuts must have about 17mm of engagement on a 12mm stud. I have heard a rule-of-thumb that says you should have at least as much engagement as stud diameter.

Keith Tanner
Keith Tanner MegaDork
6/24/24 10:19 a.m.

IIRC the general rule of thumb that we use is 1.5x the stud diameter for thread engagement. So for a 12mm stud, you want about 18mm of engagement. Some use 1x the diameter.

I believe that Goodwin offers a different 12.88" kit than the one we sell, that may be part of why there's some confusion. I don't know what Sakebomb sells.

iansane
iansane SuperDork
6/24/24 10:20 a.m.
DeadSkunk (Warren) said:

I have heard a rule-of-thumb that says you should have at least as much engagement as stud diameter.

This is what I've always heard/abide by.

That little engagement sketches me out. And I do some sketchy stuff.

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/24/24 10:50 a.m.

In reply to Keith Tanner :

At 1.5X the Konig won't be enough and how many sets of wheels are out there like that. Now I'm second guessing that again. Do those wheels FM sells have thinner seats?

Keith Tanner
Keith Tanner MegaDork
6/24/24 11:01 a.m.

I need to confirm that 1.5x measurement to make sure I remember it correctly. The FM wheels do not have unusual mounting pads.

I did check the nut and bolt that sits on my desk (car guy fidget spinner). The depth of the nut is 1x the bolt diameter.

 

Keith Tanner
Keith Tanner MegaDork
6/24/24 11:53 a.m.

I have confirmed that we use 1.5x the diameter for our internal requirements. McGard says 1x. That may be due to aluminum vs steel lug nuts. My fidget spinner is stainless :)

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/24/24 1:16 p.m.

In reply to Keith Tanner :

Maybe I'll just switch to steel nuts....I've got dozens of them...

You'll need to log in to post.

Our Preferred Partners
z0NeppfntSYnnE0WEEp2EwsaPuL5aJ2UnKjHYjnMO5YGGp46jiMGbvFmsd646CvD