How hard is it to add bigger studs on the car?

[DarkoNova]

How hard is it to drill out the axles for bigger studs?

My ATS spindles have 12mm x 1.5 studs, but my rear axles are only 7/16x20. I was going to order some 12mm x 1.5 studs from Summit. The knurl diameter is 13.25mm, which is about .052 inches. Could I just use a 1/2" bit so that there's a nice tight fit? Also, when they say "underhead length" what is that referring to? The amount of threads under the lug when the wheels are on?

[astroracer]

Under head length is the length of the knurled area. Pay attention to that. If the knurl is to long you will end up with a section of unthreaded shank hanging out past the rotor mounting face of the axle.
Pull one of the rear studs and do some measuring. If a front stud will work just get the same studs as what's in the front.
When I up-sized the front studs for the van, from 7/16 to 1/2", I ordered the same size knurl as the 7/16 stud. We did end up with a bit longer "under head length" which interfered with the rotor, but the right size drill bit made short work of that problem.

[NOT A TA]

The recommendations for the interference fit of aftermarket studs I've installed has been between .002 and .010 depending on the knurled diameter. I did a set of ARP 7/16" on some 12 bolt axles about a week ago and their recommendation was .002-.009 if I remember correctly. If your bit isn't perfectly straight .002 will not leave you with a tight fit.

As Mark mentioned watch the underhead length and taper for interference with the rotor or drum. Note the register marks on the taper of the stud in the pic below indicating it's necessary to chamfer the stud holes in the rotor a bit so the rotor will sit flush.

Installing bigger studs info here https://www.pro-touring.com/showthread.php?83259-The-14-Car-Performance-Therapy-Project-Baers-Rushforths-Yokohamas-and-more/page3&highlight=

https://static1.pt-content.com/images/pt/2012/08/0096-1.jpg

[DarkoNova]

Ah, k that makes more sense then.

I guess I'll just measure the underhead length of the old studs and try to find M12 studs with the same length, or as close as possible.

Thanks guys!

[craigs73]

heres a question.....since im wanting to upgrade mine in the near future....most of the 1/2" studs are 3" long.....what do i do with all the extra stud that sticks out to far????? any pics?

[kawaden]

heres a question.....since im wanting to upgrade mine in the near future....most of the 1/2" studs are 3" long.....what do i do with all the extra stud that sticks out to far????? any pics?
I just cut mine to the length I wanted.

[cmac06]

If the is a Currie rear axle, you can get the studs from them with the same knurl diameter as your current 7/16 studs.

[shep]

I used a 29/64 drill bit on when I did mine. It made for a nice press fit.

[TheJDMan]

Another option is to tap the axle flange for the 12m bolts then simply screw in a grade 8 bolt with all thread up to the head. I ordered my Moser 9" with 1/2" studs and my front AFX spindles were equipped with Corvette hubs with 12m studs. I did not want different sizes front to rear. I tapped the front hubs for 1/2 20 and just screwed in ARP full threaded stud bolts.

[NOT A TA]

The pic in my post above has studs I cut for capped nuts. Anyone who might be racing should check the rules for their class as some classes require open lugs so tech inspectors can see the studs.

[DarkoNova]

Another option is to tap the axle flange for the 12m bolts then simply screw in a grade 8 bolt with all thread up to the head. I ordered my Moser 9" with 1/2" studs and my front AFX spindles were equipped with Corvette hubs with 12m studs. I did not want different sizes front to rear. I tapped the front hubs for 1/2 20 and just screwed in ARP full threaded stud bolts.

That's exactly why I was asking.

I snapped the studs on the driver's side axle, and they're 7/16's whereas the ATX spindles have M12. I figure if I have to get new studs, I may as well make them match the front.