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I promise I've read all wheel stud related posts and threads I could find in the C7 forum. There is great information regarding these and thank you folks for that! The common consensus is to either use ARP 100-7725 studs or ARP 100-7726 studs. Their specifications are identical except for the overall length of 2.5" vs. 2.0". I bought 100-7726, which are supposed to be a direct replacement for the stock ones.
I had to take my hubs and knuckles out for unrelated reasons. So, maneuvering the new stud into position due to tight clearance is not the issue. To me, seems like the knurl diameter on the ARP studs is a little too big for the holes in my hubs. When I insert the stock studs, the knurled part at least initially seats into the groves on the hub. They might not fully seat, but at least don't spin. However, when I use the APR stud, the knurled part doesn't even go into the groves on the hub causing them to just spin. Measuring their knurl diameters, the APR ones are 0.3mm larger than the stock ones on average.
Also, the length of the knurled part on the ARP studs is longer than that on the stock ones. By the looks of it, the grooves on the hub aren't long enough for the ARP studs to be fully inserted. The below video and photos should help explain my problem better. What am I missing?
I've never dealt with these, but with others it's typical for the replacements to "seem" a little large. That's because they are a force-fit requiring a press to install properly. That's how it's assured they do not turn in the hub. All the best.
The 7725,7726 and 7708 are all .509 knurl and you want .007-.010 of press fit So these need a .500-.502 hole Your stock hub is probably around .490.-.496 You will need to drill with a .500 drill bit then they will go in. I have tried a reamer and the steel will just eat it, the only luck I have ever had is drilling the hubs with a 1/2 drill bit, then they press in fine. ARP studs do vary in knurl diameter I have seen ..505 to .509 but never larger than .509 I install at least a hundred wheel studs a week in my line of work, most all of them aftermarket ARP, Strange, Moser and Moroso fyi
Our OEM replacement wheel studs are designed to press-fit into the original hole in the OEM hub (preferably with a hydraulic press, as using a nut can create problems).
If you are using one of our kits in another application, the hole should be checked to ensure it falls within the correct tolerance to allow for the proper amount of interference, so that the stud won’t spin in the hole. For steel and cast iron hubs, the hole should be 0.006-0.016˝ smaller than the Knurl Diameter. For aluminum hubs, the hole should be 0.010-0.016˝ smaller than the Knurl Diameter. As a courtesy, we have provided the closest standard drill size that will provide a hole in that range.
If the hole is larger than the tolerance listed for the material, then the studs should not be used with that hub. The interfernce fit will not be tight enough and the stud could spin in the hole.
If you need to drill out the holes in your hub, the holes must be kept perpendicular to the face of the hub. If you do not have a fixture that clamps to the hub to guide the drill straight, use a setup similar to the one in the image at below. (A hand drill will not produce satisfactory results.)
All ARP wheel studs have an underhead radius. Each hole must be chamfered 0.025˝ to clear the underhead radius and prevent stud failure.
I would message/call ARP. While you could enlarge the holes, their own documentation says they can be press fit into the hub as is.
When I did ARP studs to my last track car I tossed them into the freezer, then used a hydraulic press. No reaming out holes was required.
Anything over .010 of press completely flattens all the knurling - to the point which if you remove that stud it will never have press again, at .010 of press a arp stud into a steel flange hub, the pressure on our 10 ton arbor press hits 4,000 psi - I`d love to see what .016 does to one of them lol...
Anything over .010 of press completely flattens all the knurling - to the point which if you remove that stud it will never have press again, at .010 of press a arp stud into a steel flange hub, the pressure on our 10 ton arbor press hits 4,000 psi - I`d love to see what .016 does to one of them lol...
I'm more curious why they are so far off. Maybe ARP doesn't consider these "drop-in."
Thank you all for the information. When I first made this post, I was not fully informed on what type of fitment to expect as this was my first time doing this. I was under the incorrect impression that the grooves in the hub holes are made to spec and the knurls on the studs will slide into them 'tightly'. I've since realized that grooves in the hub holes are formed when the stud was pushed through and now things make more sense.
I will resume my efforts this weekend when I'll have access to a hydraulic press. I'll first measure to make sure the difference isn't much more than 0.010", I'll throw the studs in the freezer, lightly warm up the hub and use a 6 ton hydraulic press to try and fit them. Will update how that goes.
I installed the ARP 100-7726 studs while the hub was on the car using a stud installation tool and a lug nut. An impact wrench pulled the stud through until the head hit the back side of the hub plate. Those studs have been on the car for 5 years and have had plenty of pressure put on them during track events with the car on slicks.
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ARP wheel studs knurl diameter too big?
