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View Full Version : Verify my Rear brake fab setup. Or break my balls.



Thearmymademedumb
04-20-2014, 8:04 AM
Gentlemen, this is my first build and I'm learning a lot along the way. 1999 sportster 1200c with a Road 6 Customs hardtail with 200 tire. I need advice on my rear brake idea.

I want to drill two holes in the rear supports. Behind this (between plate and caliper bracket) I would weld on a piece of bar stock to act as a spacer as well as to reinforce.
http://i.imgur.com/PdYYkV2.jpg

For the bracket, I would cut two parallel channels to allow adjustment/ease of tire removal. I plan on using an un-welded weld nut or have a t-nut designed.
http://i.imgur.com/EJZoo08.jpg


Please advise on this idea. I have not found anything like it in my research so I just want verification from the resident geniuses. Thanks.

spidr
04-20-2014, 10:25 AM
You only need one bolt, since it only stops it from rotating, but you want it as far out as possible. The reason you dont really see it done is because where you have it drawn it sees 2-3 times as much load as it would out near the caliper bolts.

Thearmymademedumb
04-20-2014, 7:24 PM
I understand the applied torque issue, which is why I designed for two bolts and plan to use grade 8. I really don't want to weld tabs to the rear tubes for the cleanliness factor....

70schop
04-20-2014, 7:33 PM
Don't weld a tab. Drill the inside of the frame tube and weld in a bung into the tube then have your mount bolt up there. Hidden, clean mount and much stronger out toward the caliper bolts.

Thearmymademedumb
04-20-2014, 8:45 PM
What's the minimum bolt diameter I could get away with?

RetroRob
04-21-2014, 5:04 PM
Don't forget chain adjustment. Two bolts Is a pain it the ass to get right. I'd use at least 5/16 grade 8 bolts . 3/8 is better

Choppasaki
04-25-2014, 7:26 PM
listen to 70's chop. Those bolts will snap right the fuck off the first time some dumb bitch driving on her cell phone cuts you off. If you absolutely have to do it, use grade 10. But don't do it

residentdud
04-28-2014, 5:21 AM
Just buy quality hardware, you will be fine. I'm running a heim set-up. 1 Gr8 bolt to the frame, 2 heim joints with high strength steel threaded rod to the caliper bolt. I only run the rear brake so it was important to make sure she wouldn't snap at speeds. The values we came up with (me and machine shop) was roughly 2 tonnes before she would be close to catastrophic failure. It takes a lot less to lock up your rear tire. Grade 8 bolts don't just shear off. They can...but think about your tire, and what it takes to lock it up...that's the values you need to look at. Trust me, I was pretty paranoid myself until I seen what it takes to destroy quality hardware.

SethBMX
04-30-2014, 7:37 PM
What about I think it's the Bird style mount? Anyone have any experience? Looks like it's just a tab welded on the chain stay an more or less keeps the stock location. Is that one tab enough?

Thearmymademedumb
05-01-2014, 5:36 PM
Thanks for all the info guys. This is what I went with. I just decided to weld a bracket to the frame. It's not as clean as I want but doesn't look bad. The bracket sits on top of the frame and uses a 3/8 grade 8. I'm not worried about the bolt failing, but if it does, the caliper will only drop about 1/8 inch to the mount. It doesn't look like it, but there is about an inch of adjustment, much more than I should need. Thanks for all the help.
http://i.imgur.com/YHVQRlT.jpg