Disc brake issues

[lightning]

My new folding ebike came with Clark's mechanical disc brakes.

They are a fairly basic design, in that the lever only moves the outside pad, so it pushes the disc against the other pad to apply the brake.

While it does work, both front and rear brakes are not smooth in their operation, it's as if the discs are warped (which they are, slightly)

On a hydraulic brake that would probably not matter, but on the mechanical brakes it causes the brake not to be smooth.

l wonder if there is a solution to this, short of replacement with hydraulic brakes? Nobody's mentioned it in any bike reviews for this model.

Should l just buy two new brake discs (or take it back to the shop maybe) or am l expecting too much, having been used to XT hydraulic brakes on my mountain bike.

 

[Woosh]

cable actuated disc brakes have only one piston on the caliper while hydraulic brakes have two.
With one piston pressing against the rotor, the rotor bends when you brake. With two pistons, the rotor stays undeformed. the simplest way to improve the performance of single piston is to use a larger rotor. I usually fit 180mm rotor to the front brakes where 80% of braking is done.
Other method is to replace your Clarke caliper with a TRP HY/RD one. It's not cheap though and the actual improvement depends also on the quality of the inner and outer brake cable.

TRP HY/RD

If your brakes don't not have sensors, replace them with hydraulic ones.

 

[Andy-Mat]

My new folding ebike came with Clark's mechanical disc brakes.

They are a fairly basic design, in that the lever only moves the outside pad, so it pushes the disc against the other pad to apply the brake.

While it does work, both front and rear brakes are not smooth in their operation, it's as if the discs are warped (which they are, slightly)

On a hydraulic brake that would probably not matter, but on the mechanical brakes it causes the brake not to be smooth.

l wonder if there is a solution to this, short of replacement with hydraulic brakes? Nobody's mentioned it in any bike reviews for this model.

Should l just buy two new brake discs (or take it back to the shop maybe) or am l expecting too much, having been used to XT hydraulic brakes on my mountain bike.

With standard disks, one does need to regularly check that the pad that does not move when braking, is always adjusted to be as close to the (unwarped) disk as possible.
The only change that I made some years ago (which many here were rudely critical of, but did not try it out for a long period, or only tried it once the disk had warped!), was to reverse the disk, as the standard way, not only heats up the disks more under heavy braking, but also forces the now (almost red?) hot disk to be compacted together, promoting disk warping, something I have never had!
When installed the other way around, the heating and braking effect serve only to "lenghthen" the spokes of the disk.....allowing it to remain true.
Even after almost 5 years of usage, I still have the same disks in use with no warping.
A professional metallurgist would explain it better than I can I feel.
Its just that hot steel, does not like being compacted together, causing even more heat in the disk, and wearing the pads out even faster...
But it is eacand everyh person's own choice as whether to try it out, but please alll of you, do not criticise until you have tried it for a year at least, to get a good comparison!
This tip applies only to disks that the "spokes" are angled to the center hub. But some are straight, and swapping these around would make no difference whatsoever of course.b If anyone needs pictures, just ask.
regards
Andy

 

[Nealh]

For £69 on can buy a set of complete 4 piston hydraulic brakes.

 

[lightning]

l could, and it would be much better, but the brake levers have switches on them for the motor (so when you apply the brakes it shuts off the motor)

l guess l would have to bypass those? My Kona e-mountain bike doesn't have them, so they can't be a legal requirement or essential.

Although on more than one occasion when l've been pushing the bike, the motor has started up because the pedals turned, and l applied the brake to shut off the motor.

 

[Nealh]

These brakes are 4 pot e brakes.
I lied they aren't £69 they are a penny short of £70.

 

[Woosh]

l could, and it would be much better, but the brake levers have switches on them for the motor (so when you apply the brakes it shuts off the motor)

l guess l would have to bypass those? My Kona e-mountain bike doesn't have them, so they can't be a legal requirement or essential.

Although on more than one occasion when l've been pushing the bike, the motor has started up because the pedals turned, and l applied the brake to shut off the motor.

you can bypass the sensors if you don't have a full throttle The hydraulic brakes are strong enough to stop the motor.
check first that your pedal sensor works properly and does not accidentally start the motor when spinning in reverse.

 

[Benjahmin]

First move would be a better quality disc, with a bigger disc fitted to the front. Then adjustment. Adjust the none moving pad so that it just skims the disc (you'll hear it rub as it passes the high spot) then back it off to just clear the disc. Then loosen the caliper mount and squeeze the brake on and, whilst holding it on, tighten the mount . Then adjust the cable length to give appropriate bite. Finally adjust lever for your preferred bite point. Takes about 10 minutes per brake.
OR
You could put a hydraulic on the front (I'd still use a bigger disc) and keep the rear, so keeping one cutoff switch. Yes, I know, unmatched levers. But really after a few miles of great, trustworthy brakes, you won't care.

 

[sjpt]

The brake sensors are only important on cadence sensor bikes; maybe the Kona you mention has cadence sensor? I find them important when doing tight manoeuvres, you don't want the engine suddenly kicking in unexpectedly Just one brake sensor is probably pretty much as good as two, so Benjahmin's suggestion of front hydraulic could work well.

I'm surprised Woosh didn't mention hydraulic sensor, eg https://wooshbikes.co.uk/cart/#/product/uid-196-hdbs-red/hydraulic-brake-sensors-on-their-own. Also available cheaper on ebay. I've been using those for 4 years; not on hydraulic levers but on integrated brake/gear levers. Also, if you are a bit handy you can probably do a DIY kit and take the switch parts out of your existing levers and attach them to hydraulic levers.

 

[lightning]

Good points, the Kona has a torque sensor as well as a cadence sensor so the motor won't start unless you actually put pressure on the pedals (just turning them won't do it!)

Where the folding ebike is just a cadence sensor so if the pedals turn, the motor can spring into life at full power, depending on what setting it's on.

lt does make it tricky to negotiate tight turns and being able to stop it happening by applying one or both brakes is useful

 

[lightning]

Well, for now l've ordered two new discs as they are only £6 each, it's not worth taking the bike back to the shop for a £12 warranty claim.

 

[lightning]

l fitted two new discs tonight, the brakes are fine now.
l set them up as recommended above. The rear pads were only partially over the disc, so changed the spacers around and it works a lot better.
They are still nothing like hydraulic brakes, it may be partially to do with the pads that are fitted, but it's made me realise how nice hydraulic brakes are.

 

[soundwave]

these are the brakes that i have on my bike but mine are silver.

avid xo trail hydraulic disc brakes set carbon levers Front And Rear Sram #010 | eBay

Rear hose length 1370mm. These are bled and ready to fit on a bike and use. Very good used condition no major marks or scuffs nice and clean, fully working and tested pistons all move freely as they should.

www.ebay.co.uk

only had to bleed them once so far and have lever and pad adjust and 4 pot calipers.

the original rotors on my bike were toast in no time esp the rear as was warped to crap and the front not far behind so got a 203 adaptor for the back and got a cheap 203 rotor and destroyed it in one ride at the fod.



not good when going 60mph down a fire road, well it was nearly on fire lol

 

[lightning]

The problem is my brake levers have cut out switches in them and l don't want to lose the switches as they are quite useful.
Otherwise l would probably go hydraulic

 

[soundwave]

you wont need cut out switches with 4 pot calipers and decent rotors and why i dont let many ppl ride my bike as i like my brakes like buttons so if you try slam the front brake on going 30mph the wheel will lock and kiss ur ass goodbye

 

[lightning]

Just to update this thread.

l fixed the brakes, new discs didn't cure it so l had a more careful look at it, and discovered that the brake pads were not covering the entire braking surface. That is, they went off the top of the disc.

l took off the calipers and reset the shims on both calipers, so the pads were properly aligned, and both brakes were perfectly smooth after that.

You can see on the photo how the brake pads were not contacting the entire disc surface

 

[AndyBike]

Well, for now l've ordered two new discs as they are only £6 each, it's not worth taking the bike back to the shop for a £12 warranty claim.

Learn how to straighten rotors. Plenty of YT vids on the subject.

Save yourself 12 quid

 

[lightning]

l did try to straighten the rotors but it made no difference to the brakes not being smooth.

Of course that's because it was not the cause of the fault, although l didn't know that at the time, so l bought the new discs.

At least they were only £12! l can save the originals as spares.

 

[AndyBike]

Brakes are the only safety feature on your bike. Cheap brakes are a danger to you. and you'd be far better looking to either get a new pair of basic shimano 4 pots, or a 2nd hand pair of Hopes.

Given your life depends on it, the words 'Only £12' isnt really something that should inspire confidence.

 

[cyclebuddy]

Brakes are the only safety feature on your bike. Cheap brakes are a danger to you. and you'd be far better looking to either get a new pair of basic shimano 4 pots, or a 2nd hand pair of Hopes.

Given your life depends on it, the words 'Only £12' isnt really something that should inspire confidence.

It's not the fact they're cheap brakes that worries me: Mechanical discs IMHO are adequate for a lower cost, small-wheeled folding ebike.

It's the fact you're paying a premium for what is in essence a sub-£700 Onebot Chinese ebike and the extra £700 premium you're paying for the "British" MiRider is in part for the "assembled in Britain" bit... including the brakes, which differ from the Onebot. Is that poor attention to brake set-up typical?

It's a bit alarming.