[Closed] Brakes with consistent bite through pad life (do they exist?)

I’ve run guide R’s on previous bikes and haven’t noticed that after a few rides. Towards the end of the pads you do tend to get a longer lever throw though - if you pop the back wheel out and pump the brakes a couple of times (make sure you can still get the wheel back in though) that resets the pads and makes it a shorter throw again.

I’ve since moved onto Code R’s and Guide RE’s. I would say the Codes are better at resisting the throw lengthening - I think it’s because they have a bigger brake master cylinder reservoir.

I changed the Guide T on my G170S to Guide2 RSC as the T were frankly rubbish at least partly for the reason you describe.

Brake pad wear was so comparatively unnoticeable that after my last ride before the lockdown I found pads front and back were both back to the backing plates 😮 , to be honest I'm now not sure if the absence of warning signs for pad wear is a good thing.

I hadn't touched the bite adjustment either other than during initial install.

As soon as the lever is pulled, braking begins. Fast forward a few rides, and the lever will be squeezing against my fingers on the bar when braking hard.

It sounds like the pistons are sticking.

I noticed this slightly with my guide R and Guide RS, before I went Morzine last year I picked up some Code RSC and have had no issues with wandering bite point or any issues really! Even changing the pads and bleeding post Morzine was easy!

As the pads wear the bite point comes closer to the bar.

You can address this by winding the levers out a bit. They'll look too far out from bar, but it makes no difference when you covering them as you ride.

Just wind back in when you fit new pads.

The bite point adjustment is to adjust lever throw not account for wear. The brakes should self adjust to account for pad wear. If the pistons are sticking take the pads out, clean the pistons and seals with IPA and apply some brake fluid (mineral or dot, whichever yours use) around the piston seals with a cotton bud making sure to really massage the interface between seal and piston, then pump the lever a few times. Apply some more fluid to the interface. Push the pistons back in with something plastic like a tyre lever. Repeat a few times then wipe off excess fluid. Put the pads and wheel back in. Pump the lever until the pads bite firmly and tie the levers to the bars. Leave for a few hours before releasing. Hopefully this will sort them for now.

My experience with Guides is that they don't self-adjust too well and it's super-quick and easy to do what I said up there.

Its sticky pistons - as the brakes are used the pistons do NOT move thru the seals - the seals deform which means as you release the lever the deformation returning to normal means the pistons are pulled back. As the brake pads wear it will reach a point where the movement available is so great that they will slip thru the seals a little to take up the wear thus keeping lever movement consistent thru the entire wear range of the pads. If the pistons are sticking in the seals then this movement to take up wear does not happen or does not happen easily enough so you get the increasing travel. A common issue on bicycle discs as the amount of movement is so small

Several ways to deal with it. tie the levers back to the bars overnight - this can encourage the pistons to slip thru the seals. Take the calliper off and work the pistons in and out a bit having put the appropriate lube on them or simply take the caliper off and pull the lever a bit and then refit - but you might go too far and have to push them back

All my brakes have completely consistent bite points no matter the wear.

@tjagain I recently changed frame on my bike. While brakes where off, I went through pushing the pistons out one at a time and "floss" them with a shoe lace dipped in isoprop-alcohol. Some where definitely happier to move than others, but there was no noticable buildup on any of them. I will try you suggestion of keeping the lever pulled.

If you have some old, very worn pads, you could try fitting those then pumping the lever. This should free the pistons from the seals. Once the pistons are extended, clean them with warm water and dish soap on a toothbrush, then rinse with hot water. When they are dry, drip a bit of fluid on the pistons, refit the old pads and use a screwdriver to lever the pads apart and push the pistons right back into the calipers. This should free them up. Rinse them again with hot water to wash off any remaining fluid and refit your good pads, then pump the brakes to reset the pistons.

@hols2 is this a process required to be followed with all brakes, or just the Guides? 😛
I understand some maintenance is required, but the brakes are not old, they had these issues from new more or less ( I notice it more on front brake, but that be because I pay more attention to it) and I have 2 pairs of them all showing the same symptoms, which is why I was wondering if these are simply not great brakes when it comes to bite point.

Is this an issue present on all brakes ?

All disk brakes 'self adjust' by having flexible seals on the caliper pistons.
When the pads are new, the seals flex enough to allow the pads to contact the disk without the outside edge of the seal actually moving in the caliper. Once sufficient wear has occurs, the pistons need to move more, past the limit of the seal flexibility, and the seal slides into a new, closer position.

I suspect the issue with the Guide R and T is that the caliper is designed for use with the RS /RSC lever (they all use the same caliper), which has a variable ratio and therefore moves the pads more than the T/R levers. The cheaper levers don't push enough fluid to move the pistons past the end of the seal flex and slide.

A quick 'fix' is to remove the wheel and give the lever a squeeze all the way to the bar once or twice - this will shift the pistons closer together. It's not a great solution though, as it is easy to over do it.

p.s. it's definitely not an issue with most brakes.
p.p.s. What I said up there -^ is slightly wrong - the seal is usually fixed in the caliper, rather than the piston, and the piston slides through it. The gist is the same though.

is this a process required to be followed with all brakes, or just the Guides?

Yes, pistons tend to stick to the seals after a while. It's good to free them up and lube them each time you change pads.

Anyone managed to buy new seals / pistons for guides?
Mine are tired and not retracting, have had the callipers completely apart cleaned, lubed and bled but still the same.

Had same issue with new hope brakes but opposite of the pads dragging and not going back.

Advice from Hope was to clean and lube up the pistons and reset it all properly and align. They recommend working a silicone lube into the piston seal as the piston's can bind when new and not lubed. Did beg the question, why isn't that done at the factory, but, all ok now. And the might explain why many people moan about Hope brakes, as since doing that service they feel lovely and linear and consistent.

My Old M675 SLX are still my favourites for reliability as you just fit them and forget all about them Same pads in my most used bike for 4 years and did everything on that bike. Only issue was the Shimano feel is a tad snatchy and got a wandering bite point which needs the odd pump.

I have got the even older SLX brakes with hole in the corner pads. They are easily the best brakes I have ever had and don't even have a wandering bite point!
When one caliper seized irrevocabley I had to buy a later Shimano brake with hole in the middle pads. I ended up bleeding it every other ride until I read about the bite point thing and gave up and pumped it a few times every ride.
It seems Shimano have gone backwards in design in the later models which after being on sale for quite a few years still haven't had the bugs ironed out

I have the same problem with my guide RS's. Stripped them completely and rebuilt and still the same behaviour. No matter what I do the bite point wonders as the pads wear down. Real pain in the bum!

I have now ordered a Magura MT7 for my front. If anything I am curious to try a different brake just for the experience. If happy I'll get the rear one as well. Those have bite-point-adjustment, as the SRAM RSC version levers, so even if they don't address the pad-wear issue I can always adjsut them manually..

A couple of posters above understand how hydraulic brakes work, most do not.

The pistons DO NOT slide through the seals; the seals deform under hydraulic pressure allowing the pistons to move a little. When you release the brake the seals return to their shape and pull the pistons back. There is no spring strong enough to push the pistons back. As the pads wear the pistons do creep microscopically through the seals and sometimes grabbing a big handful of brake can cause the pistons to jump through, even locking onto the pad, which means you've got to try to push them back.

The suggestion to try tying the levers back overnight is quite a good one but I can't understnd why people say "clean the pistons" when pad wear will be slowly exposing clean piston. Anybody who thinks cleaning the pistons will help them slide in and out hasn't quite thought it through.

I can’t understnd why people say “clean the pistons”

Because, when you fit new pads, you have to push the pistons back into the calipers to make room for the thicker pads. If you don't clean them and lube them, you are driving a dirty piston into the seals. This will not be good for the seals. Cleaning them and lubing them with some brake fluid should prevent the seals from sticking to the pistons. The pistons have to be able to slide through the seals in order to self-adjust after the pads wear.

Yes that is true; the pistons need to be clean. But most people seem to think the pistons slip in and out every time you brake.

I can’t understnd why people say “clean the pistons”

Yes that is true; the pistons need to be clean.

You sound confused. Best not to give advice if you don't understand why dirt and hydraulics aren't a good mix.