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Old 07-20-2011, 08:29 AM   #51
ontic OP
Joined: Jul 2008
Location: Melbourne
Oddometer: 1,070
Originally Posted by jake28 View Post
Note: I am not an engineer
neither am I

A second look at your photos has me more convinced. If the lower mounting point has the bolt running through both brackets and the fork leg, it should take a good bit of the flexibility out of the system.
Yes, the lower mounting point has the bolt running through both brackets and the fork leg. I just happened to have a wide selection of allen head bolts (bmw parts) that perfectly fit the thread on the brackets and the holes in the fork legs.
In the outer bracket holes I have drilled out the threaded holes and the new middle hole so that the bolts are a perfect snug fit.
The lower bolt threads into the inner bracket. The middle bolt threads into a beefy nylock nut on the back of the upper mounting point on the fork leg, that I will also threadlock (and that sticks out no further towards the rotor than the inner bracket does). The upper bolt again threads into the inner bracket. There is no, absolutly NO, flex in the system (at leas at 'human induced' loads).

I hope that makes sense.

As a precaution, I would get/make a sleeve for the upper bolt that with an ID that matches the bolt and an OD like that of the fork lug. This sleeve should then have enough clamping surface area between the brackets to reduce the amount of lateral force that the bolt is subjected to.
Excellent. That was pretty much my plan and I think what Sibbo was intending as well. The current two piece sleeve (shimmed with an extra couple of washers) I have on the moment is actually a perfect ID fit for the bolt, but is a little narrow OD for my liking (and is just there for mocking up anyway so I could acurately position the whole thing and drill the middle hole). The upper threaded holes in the brackets that this bolt goes through has a slightly raised area (as you can see) kind of like a cast in washer... what I was intending to do is turn up a sleeve that matches this OD. I could actually take it a bit wider to match the fork lug OD but I would then want to shim it or recess the face of the sleeve so that it also made contact and fitted perfectly over/around this raised area - otherwise there would be less point in making it wider than this area.
Does that makes sense?

About the straight and narrow path.
Yeah, This solution simply arose from working with parts and materials I had at hand. I didn't actually plan on doing it this way, I just realised that I with what I had I could get it done.

Out of my spare brembo caliper and bracket parts I also got a little magnetic sender thing thing that threads into that spare hole above the lower bracket hole. I believe this must have been for a speedo? So, if my stock speedo ever packs it in again, I shouldn't be too hard at all to get a digital speedo set up.

1974 R90/6
1981 R80G/S
1994 XLR250R
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