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I've just fitted a new ashima rotor (ARO-01, 203mm) to replace the avid g2 160mm on the front of my reba sl forks. Brakes are avid juicy 5's. Got the 203mm adapter (post to post) to bring the caliper out to the right position.
I've put in a couple of washers to space the caliper correctly, so that the disc doesn't quite touch the body of the caliper, but is as close as possible. Everything is as tight as I dare to do it up, no play anywhere. Done a couple of brakes up and down the street and I am feeling mahoosive vibrations coming from the front. The bottom of the fork is flexing at a guess about 10mm front and rear when wobbling under braking, and the tyre it is moving by a similar amount.
I realise the disc isn't bedded in yet, so I expected poor performance to start with but didn't fancy going down a mahoosive hill to bed everything in with severe brake wobbles. Could I have installed anything incorrectly, or is it just a bedding in issue which will resolve itself? Do I need to MTFU and point downhill and bed them in? Thanks for the STW wisdom in advance.
Sounds to me like too much flex in the system and possible grease spots on the disc.
Washers should not be needed with post mount and have you centralised the pads as well as the caliper using the hope method?
Do you really need a 203 disc? Have you sanded the pads to get a fresh surface to bed in?
All above good advice only thing I can think to add is have you got the disc round the right way, fitted flush to the hub and is the disc true and not warped?
as above - sounds to me like there's some oil or grease on the pads or disc. IPA the disc and sand paper the pads down a bit or replace them
203 is quite big for a Reba SL. it is a lightweight fork so you might be making it bend a bit!
are those forks warrantied for 200mm disks? thats a lot of torque going through a pretty flexy fork.
My deore 555s on xt rotors do this. The pads are deeper than the braking surface so it pulses as the rotor arms pass through.
ok thanks for the feedback. I'm a 15.5 stone heffer, and found the brake power of the front lacking, so after exploring other options (pads, bedding in, bleeding, disc treatment) etc, I decided to go for the larger rotor option, although it sounds like I may have overdone it. Was worried when I looked down and saw the forks flexing so much, so it makes sense they are fairly lightweight units. Don't want this to continue really, as it's my first nice bike, and I don't want to wreck the forks by putting too much force on them.
Disc is new so not expecting there to be any oil on them, straight out of the packet and straight onto the wheel. Will give the IPA/acetone route a try. Will also have a check over the system for any flexing. Do you think a 180 disc would be overkill? If not then there may be a 203mm disc and adapter on the classifieds shortly!
same on my rebas with hayes 9+ hope 185mm floater...will it break eventuallY?
are those forks warrantied for 200mm disks? thats a lot of torque going through a pretty flexy fork.
No, it's fine, and yes that is covered.