[Closed] Pad wear and lever throw.

This is also my experience of various Shimano brakes over the years. Not that it's an issue, I just wind them out a touch once I notice they're getting too close to the bar. Then wind them back in when I fit new pads.

But I've mostly used deore, not sure if the fancier ones are self adjusting.

As I understand it for at least "most" systems:

Pushing the piston out takes the lip of the seal with it. When you release the brake, the seal drags the piston back in, but there's a tiny bit less pad and so the travel is a tiny bit further.

Once the pad is sufficiently worn, though, the seal lip can't deform far enough and so the piston slips through a bit and you return to something like a "new" feeling brake and the cycle begins again

Perhaps it's more binary than I realize. It's so gradual I"m not aware of it happening, I'm just always surprised at the change in feel when replacing worn pads wit6 new.

I tend to find with my SRAM codes that every month or so I can clean the pistons, lube the pistons and reset the positions and they feel like brand new again. Doesn't take me long and it's a great feeling to have them back to crispness again.

@pjay

what brakes are they? In theory they should feel the same, but the that isn't always the reality.

Hope E4's I can pretty much run until it's metal on metal without change. SRAM need a bit of fiddling of bite point (on RSC levers). Shimano road brakes seem not to change (and theres no adjustment anyway)

I've yet to work out how to fix this on my Sram Code RSC brakes...lever pull increases over time and I've yet to work out how best to bleed the system so I can compensate for pad wear...currently if I screw the adjuster in the lever gets more pull and more 'sponge'...so it is adjusted as far out as it can go but still too much lever throw...I think I'll need to give the system a full reset and bleed again but have to work out which way to screw all the adjusters...lever position should be screwed all the way out so it is as far from the bar as possible...it is the bite point adjuster that I'm unsure which way to adjust...ideally as the pad wears, I should have to adjust it to move the pads in to reduce lever throw (as pad wear increases lever throw), but just now, it seems to be the opposite that is happening for me.

So yeah, I experience this and it really annoys me and I'm yet to work out how to fix it.

What scardypants says is how all hydro discs work or should do. If they are not self adjusting the pistons are sticking in the seals.

the answer is to lubricate the seals not to adjust the lever of bleed them

Your brakes definitely are self adjusting, otherwise you'd have levers pulling to the bars long before your pads were worn. That said, I have noticed that lever travel does seem to increase a bit with pad wear, but not to the point of being problematic.

An imperfect bleed can lead to this, as any air in the reservoir is more likely to make its way into the brake lines as the reservoir level drops with pad wear, but this is likely to lead to inconsistent movement of the bite point.

My only other guess for why this happens is that the bladder in the reservoir exerts a bit more pressure on the fluid when the reservoir is full, causing the pads to sit slightly closer to the disc at rest, meaning less lever travel to get to the bite point.

Once the pad is sufficiently worn, though, the seal lip can’t deform far enough and so the piston slips through a bit and you return to something like a “new” feeling brake and the cycle begins again

Yes, but this cycle is happening all the time, so the changes shouldn't be noticeable.

what brakes are they

They're current SLX paired to previous generation levers but I've had earlier SLX, LX & Deore do the same.

Perhaps I've been letting them get too worn.

Golfchick, what do you use to lube the pistons as I think I’ve got a couple of sticky ones.

@dickbarton

currently if I screw the adjuster in the lever gets more pull and more ‘sponge’…so it is adjusted as far out as it can go but still too much lever throw

is this for newly bled brakes and new pads or as the pads wear?

I run my bite point as close to the bars as possible (and use a combination of reach and bit point adjust to get that). Are you saying that adds 'sponginess'?

They might be working correctly all the time except when you add new pads.

If you imagine the seals are neutral at rest (they're not a lip seal, it's usually a square o-ring) and deforms under load, then when pushing them back to change pads there's a limit to how far they can go because they'll ways spring out slightly.

So with fresh pads the clearance between the pads and rotor will be slightly less untill they bed in.

Or the pistons may be worn, they typically wear in the middle of the travel. So you get the perfect function when new, but in the middle of the pistons travel they get a bit wobbly.

Wierdly SRAM road brakes get harder as they wear out untill they lock on when almost worn. If anyone can explain that I'm all ears 🤣.

One thing I've found with shimano brakes is that sometimes pushing the lever away from the bars does a bit of a reset. My theory is that the servo wave gubbins gets a bit claggy and stops the lever from returning fully, so the next time you pull the lever you're effectively pushing the same bit of oil through the system rather than drawing from the reservoir. Happy for someone who knows better to shoot that down, but whatever the reason a quick push of the levers sometimes works wonders.

Wierdly SRAM road brakes get harder as they wear out untill they lock on when almost worn. If anyone can explain that I’m all ears

I've had the locking on problem with my SRAM road brakes, but hadn't associated it with worn pads. My theory is the caliper seals hardening up over time, causing the pistons to advance through the seals more than they should. Replacing the caliper seals has fixed it for me both times its happened.

@b33k34 doesn't seem to matter for me...if I screw the adjuster all the way in (according to arrow) then there is massive amounts of lever pull that I can't get rid of...I like little lever pull.

@cogglepin I use a silicone grease similar to the Hunters stuff that Hope reccomends. That Hunters stuff is actualy for plumbers to lube push fittings with.

I used to find that occasionally leaving the bike overnight with elastic bands holding the brakes on fixed a 'long' lever.

Cheers Jordan, will have a look for some.

doesn’t seem to matter for me…if I screw the adjuster all the way in (according to arrow) then there is massive amounts of lever pull that I can’t get rid of…I like little lever pull.

Seems to be a freature of most brakes that the free stroke increaces as you wind the reach in.

Doesn't really make any difference in use as setup ose to the bar the lever is easily reachable then you get the bite point about a knuckle from the bar.

Whereas if you wanted the bite point Futher out you'd be stuffed if it had any free play at all as the lever would be miles away.

Other than to bleed them does anyone run the levers anything other than right to the bar? I suppose they have to keep the adjuster so you can get the two levers bite points to match.

@cogglepin. Plumbers merchants and car spares places will have silicon grease, sometimes in diddy little tubes which is all you would need for years of tinkering. I've also used silicone oil which was originally intended for RC car diffs, it's very thick and doesn't migrate. They all worked equally well.

Other than to bleed them does anyone run the levers anything other than right to the bar?

Me - I run them very far away because that way when braking hard my finger is in the strongest and best controlled part of its movement. Usually wound out pretty much as far as they can go. I find it much more comfortable and controllable that way. I am only bending the top two joints on my fingers not all three.

I know i am an outlier however

Had it on a pair of Zee too. Felt spongy as well. Rubbed a small patch of skin off my finger before I bothered to investigate. On a trials bike so the rear brake is on most of the time. Wound the reach out until it felt like it should - not too far away, but with really hard pressure they're not coming close to rubbing my fingers again.

I’ve yet to work out how best to bleed the system so I can compensate for pad wear

It's nothing to do with bleeding, that won't make any difference. It's a matter of resetting the pistons, as scaredypants and GolfChick explained.

I run my brakes so they start working as soon as I pull the lever. Having them come back to the bar seems the wrong way. I used to over-fill to achieve this but they now come with enough adjustment that I don't have to.

New bikes certainly aren't shipped with a long lever throw either.

As for lubing pistons, I've never done this and, going by the explanation for how the o-ring is responsible for "pulling the pistons back" believe it would be counter-productive.

I've just re-learnt (I don't change pads that often) how I get mine set up. If I swap the pads, push the pistons back and replace the wheels and pump the brakes, the levers are always rock hard. If I do the same but loosen off the caliper bolts before pumping the brakes I end up with a similar amount of lever throw with the new pads in place and everything's fine and dandy. I've no idea why but it works.

As for lubing pistons, I’ve never done this and, going by the explanation for how the o-ring is responsible for “pulling the pistons back” believe it would be counter-productive.

You're misunderstanding what it does. Pistons often tend to stick to the seals. This badly affects the self-adjustment. Cleaning and lubing them allows the self-adjustment to work as it's supposed to. It has no effect on the seals retracting the pistons. It's a very good idea to do it every time you change the pads.

I'm just going to poke the bear by mentioning that in Sram's webinar on brake servicing a while back, they specifically said not to lube the pistons, but just advance them and clean them with Iso. They said this a couple of times. I'm not saying that this is right or wrong but it's a fair proposition. I think most people when replacing pads just stuff the pistons back into the caliper bores with caked on contaminants which add friction and can cause pistons to stick. Two smooth surfaces shouldn't stick together.

Personally I've probably lubed thousands of pistons so I'm not going to loose sleep over this either way 😀 But I think cleaning is more important.

I’m just going to poke the bear

I bet you are, maple syrup for bait and lube?

@tjagain no you're not an outlier. I do the same. Have my levers so the tip of my finger just after the joint, just hangs over the lever. AS you say, when you start to pull you're finger gets into it's strongest position.

I'm the same...lever sits on crease of last knuckle and I want it to start biting almost immediately. I don't want or like a lot of lever throw...I don't see the need for it.
I can get it with new pads and a fresh bleed but after a month it starts to increase the lever pull.

It's like Canada's version of WD40 but tastier Scruff.

I think most people when replacing pads just stuff the pistons back into the caliper bores with caked on contaminants which add friction and can cause pistons to stick.

I agree that cleaning them is the key part. However, when you think about it, once they are pushed back in to fit new pads, the part inside the caliper is lubed. As the pads wear and the pistons advance, the lubed section moves through the seal. In other words, the pistons are actually self-lubing anyway. I think the reason for lubing them after cleaning is more to protect against damaging the seal when you push them back in. The most of the lube will just be scraped off by the seal anyway, only a microscopically think layer will pass through the seal. Most likely, SRAM are worried about excess lube getting onto the pads and ruining them rather than anything to do with the seals.

^^^couple of posts mention how seals are supposed to sort this issue...but my experience is seals don't always do their stuff With shimano brakes and sticky pistons I use a cotton bud and sone mineral oil on the seal ...cleaning off any surplus...another wild card issue is that bit of bent metal spring thing not quite precision and is supposed to help the seals do their bit by pushing pads back...reckon a fair few times found it just randomly jammed

I think it was a GMBN video that said you should use an earbud to put a tiny bit of mineral oil on the seals once clean. I've been doing that for a few years now and I'm not dead yet.