89 Iroc Z

I need longer wheel studs for my front LS1 brake upgrade. I went to the auto parts store today to find out the stock knurl diameter of the front studs so I can order some ARP’s. But the auto parts store computer said the front and rear studs are the same but they are not. The one’s they listed will only fit in a 10-bolt rear axel. My front studs have a larger knurl diameter. Can someone tell me the knurl diameter on stock front wheel studs?

alloy

iTrader: (16)

Order ARP 100-7708. They are .509 knurl diameter. The stock ones on my hubs measure around .489. The ARP's are a little larger, but will fit. Jeg's has them in stock, but as usual summit is back ordered on them.

89 Iroc Z

My concern with them is that they are to long. I have aftermarket lugs that will probably bottom out on those studs. I know I could go with an open back stud but I personally don’t like that look.

91Z28-350

From toddlsf's C5 page http://82lt1.cz28.com/brakes/page5.html

Motormite 98501
Dorman 610-323

http://www.motormite.com

They are 54mm long (about 2-1/8"), .509 knurl with an 8mm shoulder.

slowTA

iTrader: (1)

I asked almost the same question a few weeks ago and only got the ARP numbers.... At least we have another option. I have to say that my front and rear studs are the same, but I have a 9 bolt rear.

slowTA

iTrader: (1)

This is what the Doorman/Motormite studs look like when they are installed. I just happend to find a local NAPA that had them in stock. You can tell that they are MUCH longer than stock, but the plastic caps still fit.

ebmiller88

iTrader: (7)

Slow TA, did you redrill the stud holes at all when you installed the Dormans? I did on a kit I did and now we are having trouble with the studs turning. I just drilled the hole too big (.500"), but I'm curious if you drilled or not.

The Dormans you listed (610-323), which I used and will use again, have a 12.80 knurl diameter which equates to .5039" => .504" knurl diameter and the ARP studs I installed on my kit have a .509 which is where my problem lies...not enough meat in the hole to hold them still on the other hubs.


Ed

slowTA

iTrader: (1)

Nope, no drilling at all! I just used a vice and a long socket to remove and install them. They actually went in pretty easy without drilling. I just assumed that they were the correct size based on the info that 91Z28-350 gave, both at .509. FYI, those are the rears that I did.

I have to say that I have removed the front studs with a hammer, they didn't seem to be as tight as the rears were. I haven't installed the fronts yet, I'll do that when I get to the C4 conversion.

91Z28-350

Sorry, it's .504 like ebmiller88 calculated. I copied off the .509 from somewhere, I should have done the conversion.

alloy

iTrader: (16)

Well I just made a set of hubs for a C4 upgrade for a local guy, and he pressed in the .509 ARP #100-7708 studs without drilling and cracked one of the hubs. I told him to drill them, but he didn't listen. I've got the hub here if you want a pic of it. Cost him $50 for a new hub from me.

So my advise if you are using the ARP studs is to drill the hubs out to at least .484 (31/64ths). And unless you are using a milling machine or drill press with the parts clamped securely, you will end up with a hole around .495 or so. This is perfect for the ARP .509 knurl studs. I've done several sets of hubs like this and haven't cracked a hub yet.

If you are not using a machined down hub for a big brake upgrade and pressing these into a stock rotor or axle, you might get away with it. But a modified rotor will crack when pressing in the .509 stud.

Anyway, just my $.02 worth.

slowTA

iTrader: (1)

Hmm... I just measured a stock stud and it came up .496" to .499". The hole in the rotor is just about .486". So that's about .010" interference.

So if this holds true for most interference holes should I look for a bit around .494” for use with the Doormans?

ebmiller88

iTrader: (7)

That's what I thought..I shouldn't have drilled any larger for those Dorman studs. I think you'd be good with the .494"

Ed

slowTA

iTrader: (1)

So are you saying that I still have to drill for the doormans, just not as big for the ARPs? I wonder why my rears went in with no trouble, just a bit crooked. They straightened out with a lugnut and a washer.

Ed, think you can throw in a set of ARPs and maybe they wont spin or is extra material worn away already?

ebmiller88

iTrader: (7)

Yep, that's what I'm saying. I drilled the hubs my kit to .500" and installed ARPs and they fit great, no problems. I used the Dorman studs on a kit I just made, also drilled to .500" (like an idiot...didn't note the knurl difference), and they were loose. The Dormans should be frilled smaller, IE .494 or so, and like Dan recommended. The ARPs need to be the larger.

Yes. I got 2 sets of ARPs to replace the Dormans and it should be fine.

Long story short, both Jegs and Summit are backordered on ARP studs. I contacted Dan (alloy) and he drove 20 miles to and from his supplier on the west coast to get me 2 sets and send them to me over here in SC.

KUDOS TO ALLOY!!

Ed