Ask the experts

[BigHerm]

I really enjoyed my RSD MiddleChild Steel hardtail that I owned for 6 months or so. 64ish HTA, ran it with 140 Z2 fork, 180 OneUp dropper, 29" wheels. Frame got recalled due to a heat treatment issue and I swapped everything over to a RSD Wildcat. Super fun 120mm trailbike with shitty dropper insertion that I sold within a year. Steep seat tubes with short droppers feels so sketchy on steep descents.

[climberevan]

I especially want the short stroke on road/gravel brakes. The only thing I've had success with is forcing fluid into the caliper end with the MC port closed. But, as noted, it's a temporary solution. It's pretty quick to do though, so I just end up doing it every 10 rides or so. Yes, the bite adjustment screw is a joke.

I think the manufacturers are trying to maximize pad retraction so slightly warped rotors won't rub, but it comes at the cost of a lot of free play. Eventually someone will develop a dual-diameter MC piston that quickly takes up the slop but then offers good modulation. (Did i just invent that?)

[Boissal]

At the caliper, what affects lever stroke is how far back the pistons retract after each braking event. That retraction is due to the design of the piston seals. Can’t be changed. Try to overextend the pistons, overfill, etc. they’re going to gradually work their way back to normal after a while.

At the lever, if there is a free stroke adjustment, it is adjusting the point at which fluid stops being pushed to the fluid reservoir in the lever and starts being pushed to the caliper when you squeeze the lever:

Shimano: Free stroke is defined as stroke of the lever before the pads start touching the rotor. The free stroke screw simply changes the starting point of the master cylinder piston. If the screw is all the way in, the master cylinder piston will be all the way in, and the free stroke will be the shortest. Turn the screw out a bit and the master cylinder will start further out. Because it has to travel further before it closes off the reservoir port, the free stroke is longer. In the picture of the clear brake posted above, the free stroke screw is turned all the way in.

I think the issue with the Shimano adjustment here is that even at fully open the master cylinder piston is very close to blocking the transfer port, so there’s a limited range of useable adjustment (speculating here).

Thanks, that makes sense. Looks like there really are no options to achieve what I'm trying to do, at least with the Shimano brakes. Maybe I can find a way to 3D print a "shallower" lever blade. Won't fix the stroke issue but at least it would allow for more reach and I think I get less fatigue in my hand when my index stays more extended in general.

Any Hayes gurus out there? DTM, your latest hose swap story hasn't completely made me lose confidence in your advice! Of note, the 2mm dead stroke adjustment on my levers is all the way in already...

[HAB]

Isn't the retraction distance a function of master cylinder size and piston size? When you let go of the lever, X amount of fluid flows "backwards." The pistons will retract whatever distance is allowed by that volume of fluid flow. A bigger master cylinder means more fluid flow. Bigger pistons (and more of them) take up more volume, which means less movement for a given amount of fluid flow.

Which is to say, a pad advance should work. It's just removing the space between the retracted pistons and the point at which the pad contacts the rotor. Of course, this means that when the brakes are open there's minimal clearance between the pads and the rotors so there'll likely be some rubbing.

But advancing the pads means there's more fluid in the system - the space behind the pistons in the calipers is now larger. Usually there's enough fluid in the reservoir to accommodate that, but now there might not be enough fluid in the reservoir (which is why the pads reset after a little while - fluid has flowed back into the reservoir). So after advancing the pads, you might need to add a little fluid to the system to bring the reservoir level up to "normal" and make the whole system run correctly with the pistons advanced.

No, Sir DeJong has it right. Piston rollback is determined by caliper seal geometry. Basically, under normal braking, the pistons don't actually slide in the seal when you squeeze the brake. Instead, the seal flexes to move with the piston. However, when the pads wear enough that the seals can't flex enough to get the pads to the rotor the piston then slides in them, which is how the brake automatically adjusts for pad wear.

The master cylinder doesn't matter because when you let off the lever fluid can flow through the timing port into the reservoir. The MC doesn't act as a restriction.

[HAB]

Thanks, that makes sense. Looks like there really are no options to achieve what I'm trying to do, at least with the Shimano brakes. Maybe I can find a way to 3D print a "shallower" lever blade. Won't fix the stroke issue but at least it would allow for more reach and I think I get less fatigue in my hand when my index stays more extended in general.

Any Hayes gurus out there? DTM, your latest hose swap story hasn't completely made me lose confidence in your advice! Of note, the 2mm dead stroke adjustment on my levers is all the way in already...

Yeah, there's not much you can do to make the stroke shorter. That's just how tradeoffs in brakes go — anything you do to add power inherently has to increase the amount of leverage the brake has, and therefore the longer the stroke gets. You can reduce the piston rollback to compensate to some extent (as a brake designer, not you the consumer) but there's obviously a limit to how far you can go with that before you have a brake that you can't get to stop rubbing.


If you want mondo reach and fairly short stroke, the TRP Trail Evo or DHR Evo is your brake. The Trail has shorter stroke but less power. If you're interested in swapping one of those for your Hayes (assuming they're Dominion A4s), let's talk.

[toast2266]

No, Sir DeJong has it right. Piston rollback is determined by caliper seal geometry. Basically, under normal braking, the pistons don't actually slide in the seal when you squeeze the brake. Instead, the seal flexes to move with the piston. However, when the pads wear enough that the seals can't flex enough to get the pads to the rotor the piston then slides in them, which is how the brake automatically adjusts for pad wear.

The master cylinder doesn't matter because when you let off the lever fluid can flow through the timing port into the reservoir. The MC doesn't act as a restriction.

Huh, interesting.

But I still don't see why that would render a pad advance temporary. I've always had good luck doing a pad advance to reduce lever throw. The piston retraction is a fixed distance, but if the fixed range of movement is closer to the rotor, you get less lever throw.

[Andeh]

Thanks, that makes sense. Looks like there really are no options to achieve what I'm trying to do, at least with the Shimano brakes. Maybe I can find a way to 3D print a "shallower" lever blade. Won't fix the stroke issue but at least it would allow for more reach and I think I get less fatigue in my hand when my index stays more extended in general.

Any Hayes gurus out there? DTM, your latest hose swap story hasn't completely made me lose confidence in your advice! Of note, the 2mm dead stroke adjustment on my levers is all the way in already...

The main hack to make any brake bite sooner is to overfill the oil during a bleed. Adding more oil to the closed system effectively acts like partially depressing the lever. The way I usually do this is to do a top bleed until any air is removed, push the syringe until it's got pressure, then pull the lever a few times to suck more oil into the system and advance the pistons. You kind of learn through trial and error how many lever pulls you can do before you run into issues with pad rollback / rub, or make them too bitey. Start with doing this with bleed block in place. If you need it even shorter you can pull the bleed block out but obviously be really careful and do it incrementally.

The functioning contact adjust on the Code RSCs is one of the biggest reason why I've switched to using them, from Magura MT7s. With Maguras, I always had to do the overfill hack to get them to feel right. With Codes, I just do a normal bleed then adjust the contact point. The nice thing about doing it with an adjuster is it's easy to compensate for pad wear and keep your front/rear brakes feeling the same.

[HAB]

Huh, interesting.

But I still don't see why that would render a pad advance temporary. I've always had good luck doing a pad advance to reduce lever throw. The piston retraction is a fixed distance, but if the fixed range of movement is closer to the rotor, you get less lever throw.

Let's say the maximum amount that the seals can flex before the piston has to slide is 0.2 mm (a number I pulled out of my ass). If you don't do any pad advance fuckery there will be that much clearance between the pads and rotor to begin with, because the pistons will only advance to the point where they don't have to slide to hit the rotor.

If you advance the pistons 0.1mm and cut that distance in half, you'll have gradually increasing throw until you wear the pads down by 0.1mm at which point you'll be back to where you started.

[Boissal]

I think the manufacturers are trying to maximize pad retraction so slightly warped rotors won't rub, but it comes at the cost of a lot of free play.

I think you're right. Seems like most people aren't particularly picky about their controls but a rubbing rotor is impossible to ignore for most anyone so priority goes to a more robust system that doesn't require constant adjustment.

The issue is usually not a big deal for me but yesterday I dropped > 2000' of super steep tech stuff and by the end my hands were cooked and I was getting way looser than I should have... Cratering off a berm into a tree cause my index isn't happy would really piss me off.

The main hack to make any brake bite sooner is to overfill the oil during a bleed. Adding more oil to the closed system effectively acts like partially depressing the lever. The way I usually do this is to do a top bleed until any air is removed, push the syringe until it's got pressure, then pull the lever a few times to suck more oil into the system and advance the pistons. You kind of learn through trial and error how many lever pulls you can do before you run into issues with pad rollback / rub, or make them too bitey. Start with doing this with bleed block in place. If you need it even shorter you can pull the bleed block out but obviously be really careful and do it incrementally.

The functioning contact adjust on the Code RSCs is one of the biggest reason why I've switched to using them, from Magura MT7s. With Maguras, I always had to do the overfill hack to get them to feel right. With Codes, I just do a normal bleed then adjust the contact point. The nice thing about doing it with an adjuster is it's easy to compensate for pad wear and keep your front/rear brakes feeling the same.

Thanks, I'll try again with the Shimanos and see.
Funny you mention the MT7s, what go me started down this path was hearing a podcast with Bruni and the Magura guys. Apparently he wants his finger to barely move at all when braking and they went to great length to make that happen. Having the design team to do your bidding, design calipers and custom blades, and probably the best mechanic in the industry is probably really nice when you want your shit to work exactly how you like.

[Andeh]

^ yeah, that's a major downside to overfilling / pad advance hack. Especially if you run thinner rotors which are more prone to warping (cough... Shimano). With Maguras and overfilling them, I constantly was battling pad rub, and had to obsess over having perfectly true rotors.

[skaredshtles]

<snip>
The issue is usually not a big deal for me but yesterday I dropped > 2000' of super steep tech stuff and by the end my hands were cooked and I was getting way looser than I should have... Cratering off a berm into a tree cause my index isn't happy would really piss me off.

For me, my old shitty Fox 34 has a *big* impact on how knackered my hands and forearms got on long, rough descents. I replaced it with a Ribbon coil and the hand/arm fatigue issue got *way* better... just a data point.

[toast2266]

Let's say the maximum amount that the seals can flex before the piston has to slide is 0.2 mm (a number I pulled out of my ass). If you don't do any pad advance fuckery there will be that much clearance between the pads and rotor to begin with, because the pistons will only advance to the point where they don't have to slide to hit the rotor.

If you advance the pistons 0.1mm and cut that distance in half, you'll have gradually increasing throw until you wear the pads down by 0.1mm at which point you'll be back to where you started.

That makes sense.

I guess all of my experience has been using srams where I just roll the contact point in a bit to accommodate for that pad wear as it happens.

[El Chupacabra]

The 12s SRAM chains (and others?) need the new style checkers that have 2 opposing hooks on one end because the rollers are slightly different in diameter. Park CC4 etc. They work on all chains, so I've retired my old style one. It's easy to do on the bike but they are fine off of it too.

If you have a new one, you can hang them both from a nail or something through a link and compare the total length. If you measure 100cm to a pin on the new one, and the old one is more than 105cm, there's your 5%. Extrapolate as necessary. 12s recommends replacing at 5%.

Agreed on the fresh queso. It definitely takes up some slack, so ride 10 miles or so to be sure before measuring.

5% wear?

I assume you meant 0.5%...

[Dantheman]

Any Hayes gurus out there? DTM, your latest hose swap story hasn't completely made me lose confidence in your advice! Of note, the 2mm dead stroke adjustment on my levers is all the way in already...

No freestroke adjustment on the Dominions. They're already factory-tuned to be as short as possible. And, LOL, turns out the caliper-side seal fell out and I didn't notice.

[Boissal]

No freestroke adjustment on the Dominions. They're already factory-tuned to be as short as possible. And, LOL, turns out the caliper-side seal fell out and I didn't notice.

Wasn't all the way in on my brakes. Made a bit of difference.

[climberevan]

5% wear?

I assume you meant 0.5%...

Haha. This is ok, right?

[beaterdit]

I've broken two spokes on the rear wheel of my mountain bike in the past three weeks. They are Reynolds carbon rims, unknown brand straight pull bladed spokes, and i9 hubs. Both spokes have broken just inside the nipple, meaning I've had to take tire/insert/tape off twice and I'm getting frustrated. Is there anything I can to stop this from happening? Both breaks have come while climbing, no sticks or rock impacts that I know of. Wheel is true, and a little bit out of round. Spoke tension felt ok by hand, nothing super loose or tight. I guess whatever spokes Reynolds used might just suck

Sent from my SM-G960U using TGR Forums mobile app

I have the same wheels and I'm re-lacing them now due to nipple rot. The wheels are Black Label 349s with Sapim C-Xray spokes. All the specs are on the website and yeah, their customer service is excellent. My spoke bed got contaminated with sealant due to tape failure and the alloy nipples rotted and started breaking but I haven't broken any of the actual spokes. They are light for the application though.

The main hack to make any brake bite sooner is to overfill the oil during a bleed. Adding more oil to the closed system effectively acts like partially depressing the lever. The way I usually do this is to do a top bleed until any air is removed, push the syringe until it's got pressure, then pull the lever a few times to suck more oil into the system and advance the pistons. You kind of learn through trial and error how many lever pulls you can do before you run into issues with pad rollback / rub, or make them too bitey. Start with doing this with bleed block in place. If you need it even shorter you can pull the bleed block out but obviously be really careful and do it incrementally.

The functioning contact adjust on the Code RSCs is one of the biggest reason why I've switched to using them, from Magura MT7s. With Maguras, I always had to do the overfill hack to get them to feel right. With Codes, I just do a normal bleed then adjust the contact point. The nice thing about doing it with an adjuster is it's easy to compensate for pad wear and keep your front/rear brakes feeling the same.

Same. Pretty picky about my brake feel and having a functional free throw adjustment is key. Plus CODE RSCs are just so consistent and IME, reliable.

[XXX-er]

any traction for the idea that its better to replace brake padz before they get too worn down from the POV of lever feel ? ?

[Benneke10]

Are those little washers that go between SRAM cranks and pedals really necessary? I lost one in transit, is it worth the hassle to replace it?

[toast2266]

Are those little washers that go between SRAM cranks and pedals really necessary? I lost one in transit, is it worth the hassle to replace it?

Not super necessary, but easy enough to replace. Go to any shop and I bet they'll have a pile of them.

[Gunder]

Are those little washers that go between SRAM cranks and pedals really necessary? I lost one in transit, is it worth the hassle to replace it?

Depends on the pedals, but usually yes. They are cheap and most bike shops should have a stack of them.

[HAB]

any traction for the idea that its better to replace brake padz before they get too worn down from the POV of lever feel ? ?

Depends a bit on the brake IME. In theory it shouldn't really matter if the brake has enough fluid volume in the reservoir to take the pads down to nothing, but some don't, especially if you're hanging the bike for storage and can start to get air in the line when the reservoir gets low.

Adding fluid when the pads get worn down and then taking some back out when you replace them is also valid.

[XXX-er]

Depends a bit on the brake IME. In theory it shouldn't really matter if the brake has enough fluid volume in the reservoir to take the pads down to nothing, but some don't, especially if you're hanging the bike for storage and can start to get air in the line when the reservoir gets low.

Adding fluid when the pads get worn down and then taking some back out when you replace them is also valid.

Well no it shouldn't but does it ?

The shimano on my Yeti felt spongy in a couple of years, but it would pump up, so we bled it by pumping fluid top to bottom and it felt great, I sold it to an MD ( who else ) so i don't know how that ended up

I definatly replace well worn padz at the same time I bleed


we drive cars for decades without needing to bled the brakes so how do mtnbike brakes suddenly get spongy/ air in them in a year or two ?

[Gunder]

Well no it shouldn't but does it ?

we drive cars for decades without needing to bled the brakes so how do mtnbike brakes suddenly get spongy/ air in them in a year or two ?

Better seals, more mass for heat dispersion, mostly solid lines and just better built. With bikes, is all built to be as light as possible and doing so, you loose some long term performance. I try to replace my pads before they get too worn. I have found when they do get worn quite low and I bleed I tend to have more discolored fluid, so thats telling me there is a heat issue going on. I also like a really firm and pretty quick to engage bleed, so I tend to over prime mine a bit as well.

[rideit]

Just chiming in to state the obvious, be very, VERY careful overfilling any Shimano system, or you can very easily damage the reservoir bladder. I learned the expensive way that this generally is not repairable. There are a few hacks, but I doubt they work long term?