Ultegra 6800 Brake Wonky

delete_my_account

I'm in the process of replacing the brake pads and cables on my Planet X RT57.

It's been a nightmare setting up the rear brake so it works nicely. It's feeling spongy and crap.

I noticed the reason there is no definitive on/off feeling is because the brake pads are not parallel with the wheel rim. Both pads are very, very close to the wheel rim at the back while there is at least a 3mm gap at the front of each of the pads.

The pads are brand new so they're not worn weirdly like the old ones were, so it's not that. The only thing I can think of is that the caliper is somehow twisted but it's odd that it's on both sides and the same amount.

Any ideas?

dgunthor

you don't normally have the pads parallel to the rim as the brake will be on/off. when the pads are toed in you get some modulation - 3mm sounds a little excessive though

delete_my_account

I've just discovered that you can adjust the toe angle of the pads!!!!
I did not know that.

Is that a new thing for these brakes or have I been able to do that with all my previous brakes as well?

sungod

it's normal to be able to adjust toe-in

adjust them so that the leading edge is about 0.5-1mm nearer the rim than the trailing edge

then adjust cable tension so that the pads are about 2-3mm from the rim

they shouldn't be on/off, there should be a progression, if pads are too close the leverage tends to suffer plus you may get rub if the wheel/frame flex

if you've changed cables it'll take a while for the outers/ferules to fully seat in the stops, especially for the rear, so be prepared to do some adjusting until everything snugs down tight

btw make sure the pads are centered on the rim, otherwise you'll lose braking force and/or risk damage to tyre/rim

Rightarmbad

Toeing pads is just a mythical fix that only sometimes works for brakes that have issues that are not present 99.9% of the time.
Set them flat.
You will get better clearance, better modulation and they will wear better.
Toe disappears by the end of a good long decent anyways as the pad wears.
Toeing also applies a twisting force to modern stiff calipers that is simply not required.
Older calipers were much more flexy and had slop in the pivots, that is where toe is required.

If you have brake squeal check that the brake fixing nut is long enough to give the brake axle full support in the frame.
If it only engages a few threads, the axle can rock and set up resonance, sometimes the bandaid approach of toe will help this, but the real answer is to stop the bending flex of the unsupported axle.
Amazing how many bikes come like this.

Squealy brakes on light pressure is contamination or not bedded, or simply really bad setup. Squeal under prolonged hard braking is undamped flex or pads too hot.

sungod

if it makes you happy to believe this feel free, but you're wrong

you also missed out another benefit of doing it, but not my job to fix every error on the internet

trailflow

Toeing pads is just a mythical fix that only sometimes works for brakes that have issues that are not present 99.9% of the time.
Set them flat.
You will get better clearance, better modulation and they will wear better.

Shimano says to toe them in the setup PDF ? are they wrong ?

matt-h

Toe in pads on 6800.
Mine squeeld until toe in was set.
I put a penny under the rear of the pad then tighten.

Matt

indyjones

Toe in using a couple of folded over business cards, easy peasy. As usual there are guides on youtube that makes life easier.