xp8 rear dsic brake adapter - bearing size query

[02gf74]

I am looking to make a disc brake adapter to fit to a proflex xp-8 rear swingarm.

There are a number of designs, a lot of them utilising the axle drop out but my two points of attachment will be the M6 stay pivot bolt and the  M5 tapped hole that is already in the drop out.

The complication (?) is that the stay moves relative to the swingarm/adapter so my solution is to fit a bearing.

I have acquired two sizes:
6 x 12 x 4  (i.d. x o.d. x width)
6 x 13 x 5 

So similar in size but one is a bit wider.

I do not know the kind of forces the bearing will be subjected to so do not know if the smaller of the two will be strong enough - I suspect it will be.

Only "info" I have is that the bearings on specialized epic frame are 5 mm wide.

The bearing will be pressed into a 6 mm plate and goes where the swing arm bolt is - just above the "Warning" label.  Hopefully photo will explain it better than I (note: this is mock up using thin strips).

[02gf74]

re: spech bearings: these are for swingarm and linkage so some part of the riders weight will be taken up by the bearing - with my adapter it will be just rear braking force.

[Colin]

That's a unique solution, isn't it? Well done on coming up with a new idea!

Someone with a better understanding than me may need to explain why Hammerheads transmit the braking force into the axle........

I've fitted one on my XP-X with Avid BB7's and it's all great!
see my piccies of a trial fitting on a spare 856 swingarm and thoughts on variations.............
http://idriders.com/proflex/coppermine/displayimage.php?album=53&pos=2
In the end I filed down the buttress on the dropout to make the adaptor parallel to the rotor.




Col.

[02gf74]

This is a little project that has been bubbling away for some time - there are quite a few variants of adapter, most are like the one you posted that utilise the axle (which I wish to avoid), some like mine using the stay pivot and a few using a bar going to the brake boss.

[fyrstormer]

Honestly, I don't think any adaptor can beat shovelon's welding for strength and appearance.





(just go ahead and ignore my crappy paint job.)

[02gf74]

ofcourse in an ideal world I'd weld it on but would need to farm the work out - not a biggie and then need to repaint the swing arm, again not a biggie and finally source the sticker, again not a biggie if I don't have it as per original.

nevertheless, I will give my adatper a go and see what happens, it will be reversible would I ever (not likley!!) go back to V-brakes.