Hydraulic disc brakes brake less than rim brakes?

javidr

Hi

I bought a bike a couple of months ago, which has hydraulic disc brakes. I was expecting it to brake a lot more than the old rim brakes, but my feeling is exactly the opposite.

I feel it quite soft. If there’s a need for a sharp braking, I don’t think I would be able to brake the bike completely.

I don’t know if this is expected, or if it is just because the discs are new.

Also when I brake hard, I can hear like the brake rubbing with the disc, instead of braking completely

Any advise on this please?

Thanks

trevor.hall12

How much travel is on the levers ? How soft do they feel .

javidr

Not much, looks normal, halfway I would say, but doesnt feel quite hard, more or less like rim brakes

First.Aspect

In which case you are at the clean the discs, clean the pads, rub the top surface of the pads off stage.

There's a lot of tecnobollocks talked about cleaning stuff off rotors, and you can even get super expensive spray cans (which are either acetone or ethyl ether). Use washing up liquid and water. And a scouring pad.

Same for the pads. I've found the starting from scratch approach of skimming the surface over a paving stone... or wet and dry... fairly effective.

Other things to look at are centring of the rotor. So consider retracting the pads, releasing the bolts holding the capers, and pulling the levers then retightening the bolts.

As I've said in previous threads, when they work well, they are great, but hydro discs are comparatively complex and fickle. At least in the dry, the only possible benefit is ease of modulation (which isn't a benefit at all if you are remotely experienced), because outright braking performance is tyre-limited.

Good luck.

super_davo

In many cases you don't get that much more out and out braking power on discs over rim brakes, because caliper brakes are already pretty effective, and the limiting factor is usually tyres. Where hydraullic discs should be better is in modulation i.e. letting you use the most of that power & of course wet conditions.

Based on your description of your symptoms I'd expect the likely culprit is air in the system, and bleeding the brakes should fix it.

Some people swear by bedding in pads and have a process to do it like a number of hard stops in succession, and say it makes a massive difference. If you've had the bike a couple of months, then you would likely have had the same effect just through normal usage.

The other thing that can increase power is increasing the size of the rotors. If you've got standard flat mount brakes with 140 rotors on the front then you can usually flip over the adaptor on the mount and fit 160s. However, that should be one of the "last resort" things you do when you're confident the system is working as it should - and I don't think you're there yet.

First.Aspect

I like 700mm rotors.

trevor.hall12

The symptoms suggest there might be some air in the system.
I've seen brand new bikes not set up properly from wherever they were bought.
I would suggest if you can going to where you bought the bike to get them bled .All my disc bikes levers have a solid feel nothing like my rim brake bikes .

First.Aspect

Er... all hydro systems have a bit less initial bite than a rim brake setup. But they should still feel pretty solid.

Air in the system is characterised by the spongey feeling even after the pads have engaged. Which isn't the same feeling as a nice solid lever feel but no stopping power.

Hard to say which one the OP has.

But i would note that most new hydraulic brake systems come pre-bled.

trevor.hall12

It's 2 months in
It should feel harder than rim
Agree
They come pre bled before you cut the hose to fit .
I always top bleed a new system ,it's just good practice as I say I see new bikes( weeks old ) from everyone that are poorly fitted/bled
It's also a simple thing to try and eradicate what the issue might be .

First.Aspect

I'd love to get your take on chain cleaning.

super_davo

Not that hard to clean a chain without contaminating disc brakes. On the winter bike that gets covered in crud I just stick muc off disc covers on and go nuts with degreaser and a hose. On the summer bike, I wax the chain, so it never really needs anything beyond a wipe with a baby wipe anyway.

First.Aspect

I've gone into the twighlight zone.

imposter2.0

Hoses may be leaking, or kinked. I had a similar spongey feel on a new hydro disc bike - turned out the brake hoses were both leaking from new...

First.Aspect

He hasn't said they are spongey. He's said they feel about the same as his rim brakes. So either the brakes on all of his bikes are spongey, or none of them are.

DeVlaeminck

Symptoms would fit with contaminated or glazed pads - that - I'm not sure which - was the issue with my Genesis CdF that runs those cable operated hydro disc calipers.

Problem with discs is not so much fixing an issue once you know what it is it's more getting an accurate diagnosis. It can be frustrating because you can try different solutions just to eliminate causes.

veronese68

If you can't pull the lever back to the bar it's probably not a bleeding issue. As DeV says it sounds more like glazing or contamination. Did you buy the bike new? If so can you take it back to the shop you bought it from and get them to look at it? Probably better than getting guesses from people on the internet that can't have a proper look.

First.Aspect

Or you could take my advice and give the pads and rotors a good clean, scoue the surface of the pads and see if that fixes it.

veronese68

First.Aspect said:

Or you could take my advice and give the pads and rotors a good clean, scoue the surface of the pads and see if that fixes it.

Yes, that would be my next step. But if it's a newish bike the shop should sort it and would save the OP some time

First.Aspect

I suppose. Depends if you need to leave it there for several days.

lesfirth

First.Aspect said:

Or you could take my advice and give the pads and rotors a good clean, scoue the surface of the pads and see if that fixes it.

..... and then bed them in by doing hard braking.

First.Aspect

lesfirth said:

First.Aspect said:

Or you could take my advice and give the pads and rotors a good clean, scoue the surface of the pads and see if that fixes it.

..... and then bed them in by doing hard braking.

Some say that causes glazing. Others say it avoids glazing.

pangolin

I've certainly glazed over

lesfirth

The problem with this forum is that the sound advise is lost in piles of bulsh1t. I will just keep my fingers off my key board in future.

paulbnix

I've got rim braked and hydraulic disc braked bikes.
Both are SRAM Force so similar quality point.

In the dry the actual braking performance is similar but feels different.

Basically the disc brake lever is a lot softer feel with more travel.
The rim lever is setup to engage in the first bit of movement then its just applying pressure.

I notice this because I have some arthritis in my hands so the disc setup is more forgiving but I prefer the rim brakes simplicity and ease of maintenance.

In the wet of course the rim brake suffers much more performance degradation.

I think your disc setup should give at least the same performance as the rim.

I would take up the suggestions above - give the rotor a clean with iso propyl alcohol and gently rub the pads over some fine sandpaper.

javidr

Thanks all. I think the problem might be the lack of bedding in, I will try to do the process today and if ir doesn’t work I will sand a bit the pads and try again

Thanks!

javidr

Right, I did the bed in process and the brakes are better now, but I still feel they have issues. When breaking it still makes noise, like if the pad was jumping over the disc, and a bit of vibration.

So, assuming it’s related to not having done a bed in on the brakes, what can I do now once to fix it?

paulbnix

Seems like you are running through the disc brake problems.

Noise is an issue that I have managed to avoid except when the disc is wet and then it will happen for a period then stop.

I had some SRAM Centre Line rotors that would not stop making a noise if the slightest bit damp.

I ditched them for Shimano ice tech and they are much better for me.

Once you have been through the bedding in process you could try fiddling with the alignment of the caliper to see if it helps.

I have heard stories of some disc brakes that are always noisy but not experienced it myself.

zest28

Do you see mountain bikes, motorcycles and car uses rim brakes? Nope. Bring your bike to the bike shop and let them check out your brakes.

pblakeney

zest28 said:

Do you see mountain bikes, motorcycles and car uses rim brakes? Nope. Bring your bike to the bike shop and let them check out your brakes.

I have 700mm disc brakes.

First.Aspect

zest28 said:

Do you see mountain bikes, motorcycles and car uses rim brakes? Nope. Bring your bike to the bike shop and let them check out your brakes.

Motor cycles and cars never used rim brakes, go slightly faster and weigh a bit more. The main motivation for using discs in mountain biking does not exist on the road.

They are slightly nicer to use, when they are set up okay, I'll agree. But at the cost of everything else about the bike.

Can you comment on the effect that disc brake have on the stiffness of wheels and forks? Or are force moments not your thing...

trevor.hall12

paulbnix said:

Seems like you are running through the disc brake problems.

Noise is an issue that I have managed to avoid except when the disc is wet and then it will happen for a period then stop.

I had some SRAM Centre Line rotors that would not stop making a noise if the slightest bit damp.

I ditched them for Shimano ice tech and they are much better for me.

Once you have been through the bedding in process you could try fiddling with the alignment of the caliper to see if it helps.

I have heard stories of some disc brakes that are always noisy but not experienced it myself.

Sram Centreline turn up bent from new in my experience .