Hydraulic disc brakes - poor performance

jdobson76

Just got a brand new bike which has hydraulic disc brakes, never had disc brakes before (wasn't looking for them this time but this was the best value bike I could find which had decent gears as well).

I am finding the performance of the brakes awful. The back one is OK, in that it does some stopping, but not as good as the v-brakes on my (very) old bike. The front one is next to useless, virtually does nothing.

I've tried some tips I was given on here (go down a hill and do some hard stops - I live in the fens so this is easier said than done but I got going as fast as I could) but nothing has improved yet.

I took it for about 20 miles on a traffic-free cycle path first and subsequently rode it into work (through town) twice, but I'm actually feeling unsafe in town with these brakes so will switch back to my old bike.

Is there anything else I can try myself, before I take it into a shop, or things to look out for when in a shop to see if they know what they're doing? Don't really have confidence taking it to where I bought it (Halfords, I know I know) as it's been like this since I first rode it. Don't know any bike shops round here as the one I used to go to has closed, so I'll be taking pot luck with any shop.

The Rookie

Sounds like contamination, the smallest amount of oil/grease in the pads and there is little or no braking, only solution is new pads and a complete clean of the discs with Alcohol (rubbing alcohol/IPA) while the contaminated pads are out..

Don't use any sprayed oil near a disc brake bike AT ALL (GT85/WD40 etc).

imatfaal

Perhaps they need bleeding. Does the braking improve if you pump them - that can be a sign of the need to bleed.

Ditto what rookie said - GT85 on pads or disc is lethal

Hydraulic disks when grabbed stop the wheel like nothing else - if they aren't doing that then something is very wrong. I would take it straight back to Halford's - and that's why we go to LBS :-)

First.Aspect

Oil on brake pads is a no no, but in my experience its effect can be over stated. Should burn off fairly soon if its contamination - I've done some pretty dumb things with WD40 and had useable brakes very soon thereafter. If discs were as sensitive as mtbers claim, I doubt they'd let people use them on cars.

My bet is brakes need bleeding. Shimano ship them dry and so it up to the staff at Halfwits to assemble and bleed them.

Whatever the reason, I'd get the bike back to the shop and let them sort it out.

The Rookie

Car and motorbike brake pads are easy to get hot enough to burn off the contamination, on a bike its hard to get enough heat into them as the contamination means little friction is available to generate that heat, not uncommon for pads to be ruined by a small amount of WD40 and never ever recover.

father_jack

I have cable disc brakes on my other bike, you virtually lock up the wheels pulling the levers

I don't find much control over them, it's not like no braking/lock up but it's not as gradual as rim brakes.

I don't have hydraulic brakes but it could also just be air in the tube? Try bleeding them.

Neil_aky

Take the pads out and rub them with some emery tape; clean the discs with IPA / IPA Wipe. If that doesn't work look at the options e.g. bleeding etc. but better to take it to LBS to check them out if the above doesn't work

The Rookie

Bleeding is needed if there is a long lever travel back to the bars, for anything else, BLEEDING CAUSES MORE PROBLEMS THAN IT FIXES if you don't know what you are doing.

The OP's description shows bleeding is not a fix here.

woodyonthebeach

Start with the following

1. Clean disk with some sort of alcohol (I use cheap nail varnish remover) Test and to see if that works
2. Remove pads clean with alcohol then rub on sand paper (wet and dry with a fine grain is best) then clean again with alcohol and replace, take time to clean the disk as well. Test to see improvement.
3. Local bike shop and get them to bleed the brakes

The Rookie

Step 2 is unlikely to decontaminate pads, and again if the lever operation is normal then bleeding is a waste of time and likely to create more issues than it will fix, air in the system creates a very specific symptom as does contamination (a very different one).

Also bleeding is dead easy, so why a bike shop?

DJFish

It does sound like they need, cleaning, bleeding or setting up properly.
I've just changed my pads & bled them and the first time I went for a hard stop I nearly went over the bars.

Silly question but are the front pads in the right way round?

The Rookie

That was probably just changing the pads, bleeding ONLY changes level travel, not power (assuming the lever doesn't come back to touching the bars).

turkeytickler

I'd take it back to Halfords and give the problem to them.