Rear brake callipers

[Jerry]

Hi

Has anyone changed or seen anyone change the set up of the rear brake calliper, i was at Mallory on a very wet Sunday and trying to change the rear tyre quickly on your own is a pain. I have heard that some guys change the position of the calliper but i have not seen a bike with this done...it would be great to have the set up the Endurance bikes have now that is a quick tyre change.

Cheers.

[cargo]

The quick change set up that many race bikes have now involve little cups for the wheel to sit into these are normally on the swingarm and support the wheel via the spacers in position while the spindle goes through.

I have seen one ZXR400 with the caliper moved to the top on the disc it was on the RMKD ZXR400 can't remember how it was done I think you need a different bracket to mount it and some means of replacing the torque arm

[jake]

i here you on this..
speaking to someone about it today at aintree, and he told me you can buy captive spacers that fit in behind the seals. he told me where to buy them, but i fell off and banged my head.....so i havent got a clue

alot of people take the caliper bracket off, then you can just push it up once the wheel is in. if you dont want to do that, make sure you aint got that plastic cover thing on the bottom of the caliper. throw that in the bin, and it makes it easier to hold the pads apart from underneith

[jake]

this chaps bike, think he might come on here? dunno.
anyhow, i think he welded a plate to the standard rear caliper bracket, fixed it to the top side of the swingarm.
so i presume that would stay still when you drop the wheel, which would be brill, and you lose the arm thing too.

[zimm]

thats fucking lovely !

[rene]

This might be worth a read

http://homepage.ntlworld.com/webzxr/zxr ... brake.html

the 750 uses the same caliper bracket as the 400 i belive so it should work.

[zimm]

the hanger looks a bit different, but is similar enough that it would work

isnt the whole point of the torque arm arrangement that it goes some way to preventing the rear of the bike squatting though ?

[cargo]

the hanger looks a bit different, but is similar enough that it would work

isnt the whole point of the torque arm arrangement that it goes some way to preventing the rear of the bike squatting though ?

I've wondered about that very thing and never came up with a good answer

Certainly the main function of the torque arm is to hold the caliper and stop it from moving round with the disc when you brake.............but as to a benifit in reducing rear suspension squating...............?????????????

[rene]

how would it help stop squating? Never taken a ZXR swingarm off but dosnt it attach to the same point as the swingarm meaning it will move with it?

[zimm]

it attaches to the frame about 2 inches below and an inch back from the swingarm pivot, the rotational forces pulling the caliper round with the wheel exert a tensile force on the torque arm, which would counter (to a degree) any forces attempting to make the suspension compress.. (if the arm was disconnected from the frame and the caliper clamped to the disc, and you pulled on the arm, the suspension would extend)

as to how much effect it has i dont know, i've never bothered to do the maths as it gets complicated trying to take into account the weight shift to the front of the bike under braking, and everything else thats involved..

it cant have much of an effect as the angle over which any effect the arrangement has is quite acute ?

its something thats always intrigued me though, as some bikes obviously dont have this arrangement, yet others do..

[Davw]

Zimm - I am certianly no expert on this but using the situation in which the torque arm was disconnected at the swinging arm and the pads clamped to the disc if a tensile force was applied to the torque arm there would be two components to that force - the major component would be horizontal and the minor component would be vertical. The vertical component would be working in an upwards direction (because the torque arm angle must be slightly upwards) and would therefore tend to make the suspension compress and not extend.

I cant see how the torque arm can assist in stopping the bike from "squating" under braking. Is it not the case that the torque arm tends to be designed the way it is to minimise the tendency for twisting at the connection between the arm and the caliper. A really short torque arm (or plate) will have much larger torsional forces applied to it under braking.

Then again I might be totally wrong!!!!

[zimm]

yep, basic co-planar physics .. except the tensile force is being applied to a pivot, and becomes an anti-clockwise rotational force (looking at right hand side of bike, clockwise being the rotation of the wheel when bike is moving forwards), which would make the suspension extend, both the horizontal and vertical components of the total force applied through the arm to the brake hanger would come into play

fries my head ..

[Davw]

Thats it - I am off to lie down in a darkened room - my head hurts. :smt013

Getting back to more basic matters any input on rear shock improvements for the track. maxton, ohlins etc etc. Any experience or recommendations??

[zimm]

lol

i'd go with ohlins unless you are really fat or really small, and then nothing off the shelf will be right anyway, in which case maxton, in which case get them to re-valve and re-spring your stock shock.. costs far less and will work great

[Davw]

lol --

Sounds like Ohlins then as I like to think of myself as perfectly sized. Neither fat or small but 82kg of pure muscle - ok - surrounded by a bit of insluating fat