Making XT discs work when they're not meant to

[Rik]

This is a silly idea, but if it could work it'd be great:
My brother wants/needs a disc on the front of his bike, and since he runs left-front levers, and I run right-front levers, the idea was put forward that he could take my rear XT disc.
Now it's come to my attention that the rear caliper isn't meant to work on the front (gee, that's suprising :roll but after having a muck around, it almost lined up with a 170mm rotor.
Now, is there a way to run the rear caliper on the front, using an odd size rotor (180mm would be perfect I think), space it out and run a 205mm rotor (where on earth could I get the spacers from?) or any other solution to get the rear caliper to work on the front...

I know I should just run them front and rear, but if we can split this disc set in half, we can also go halves in a set of Magura HS33's, so both of us have XT disc front, HS33 rear (which is a combo I really want to run in the first place). And splitting up the brakes would be the perfect solution.

All help/ideas/input welcome!

 

[lupine128]

with a little work you can make a spacer to let you run an 8" rotor with a rear caliper, no problem. just use 5-8mm plate and cut and file one for yourself.
you'll need to get the plate thicness right to let you space it out for the rotor, or just counersink the bolt holes to fit.

 

[Rik]

That's on my mind, and probably the best solution (as I intended on going 8" for my bike anyway).
The spacing is an issue, as is alignment (keeping it all parallel with the rotor), so I'll probably just buy a premade 8" adapter, drill some new holes and bodgy it up!

 

[wombat]

If you're after a well priced adaptor, get one of the imperial ones from Bill, you were right, that price list is handy!

 

[Rik]

That pricelist sits next to my bed, so trust me, I know all about it
At the same time, might as well order a front hub... and my brother wants a rigid fork... and I could do with a chain device... and the list goes on :lol: Damn his affordable merchanside!

 

[lupine128]

when i was looking at the calipers on my grimeca's the fitting of front and back is the same, so i thinkit should be thesame for Xt.
jsut remember that some calipers are designed to run 170 front and 160 rear (aireal) and as such you have to run the right size disc.
but probably makeing your own is the best bet for a perfect fit.
it's not hard, i've made spacer/adapters for a couple of brakes now and you'll be fie if you make a card or ply mockup first.

 

[Rik]

Well the rear caliper fits on a 170mm rotor, but there's bugger all contact area between pad and rotor (hence a 180mm would be perfect).

Rear IS is spaced differently in relation to the axle compared to front IS, so it seems, hence the Liquid and similar discs just use the same caliper body front and rear, and just use a bigger rotor on the front to make up the difference in spacing.
This is all what I assume after farting about with discs this arvo.

Oh and yeh, you'd assume the Grimeca's are the same as the XT's, but alas, my rear XT has different dimensions, it sits out further from the mount than the front caliper, I wish I had a camera handy to show the difference.

So anyway, this bike is off the road awaiting a bottom bracket, so I have a week or so to bodge together my own adapter... 8" front with a DIY adapter sounds like the way to go, unless there is a commercially available solution.

 

[lupine128]

nah, you don't want to buy something.
bodge it up and stick pics on here. we all want to see what you made for the job

 

[Grip]

Rear IS is spaced differently in relation to the axle compared to front IS, so it seems, hence the Liquid and similar discs just use the same caliper body front and rear, and just use a bigger rotor on the front to make up the difference in spacing.
This is all what I assume after farting about with discs this arvo.

Ah yes... you assume correctly, donkey-dick. Yeah the new Armor mech discs are exactly the same calipers front and rear too only they run 160/180 rotors to get 'em on. Clever!

Sounds like you've got this sorted Rik, but I'm not sure if you need a 180 rotor or not. If so give a call as I happen to have a spare one brand new 6 bolt.

Cheers

 

[Rik]

donkey-dick

I'll take that as a complement 8)

So you have a 180mm rotor spare hey... hmmm, something to think about, I don't want to jump in at this disc swapover yet (other priorities right now) but if my brother coughs up some cash for the rotor I'll shoot you an email. Thanks!

 

[Grip]

donkey-dick

I'll take that as a complement 8)

Oh... wasn't it you I was talking to about our liking of the old Fast Forward sketches with Peter Moon and.... (damn, forgotten his name!) ripping into the Kung Fu show? "ahhh... when you can take the pebble from my hand, donkey dick..." etc

Well if it wasn't you Rik then yeah... obviously I mean it as a compliment... shit I say that to everyone, mate... trust me :wink: