New Disc Brakes A Little Soft?

[Tim330]

Hi

I just picked up a new rockhopper at lunchtime from Evans to replace my ageing hardrock. On the short ride back to the car park the brakes didn't feel great.
(Shimano BR-M505 hydraulic disc brake, dual piston) from the website

http://www.evanscycles.com/products/specialized/ro...


They stopped the bike ok but weren't as sharp as the v brakes on my old bike (the std ones on a 2006 hardrock)

Are MTB brakes like cars brakes requiring some bedding in before they function fully?

[Trevelyan]

Yep, they need a bit of time for the pads to bed in and also for any surface contamination on the discs to wear off.

You might also need to bleed them after a while. I had to do mine after a couple of months and it made a world of difference.

[Tim330]

Thanks, the shop offered a free running in service after 4-6 weeks so I'll ask about this then if needed.

[curlie467]

Get up to a decent speed, say 10 - 15 mph, hit the brakes hard without locking up the wheel and almost stop, do this about 10 - 15 times and they should feel much better. You will feel them getting better and better each time. knackers you out though!

[Tim330]

I'll find a big hill. Out of interest how long will the pads last compared to pads on v brakes? I've had the same pads on my old bike for 3 years & they still have some life left. I don't do much heavy braking though & probably ride about 10-20m/week

[Mars]

Don't want to be the voice of doom and gloom but mine (hybrid) were sharp from day-1. I would question the shop about this and see if they have any other bikes you can compare with.

[Gooby]

Mine have always been sharp. Do they need a bleed? Moisture in the fluid would be my first guess.

[Tim330]

Its currently in the back of my car. I'll take it for a ride after work & see if they bed in. If not its back to the shop!

[Mr E]

Tim330 said:

I'll find a big hill. Out of interest how long will the pads last compared to pads on v brakes? I've had the same pads on my old bike for 3 years & they still have some life left. I don't do much heavy braking though & probably ride about 10-20m/week

Depends where you're riding. I've burnt a set out in a weekend...

[mk1fan]

Gooby said:

Mine have always been sharp. Do they need a bleed? Moisture in the fluid would be my first guess.

Shimano run mineral oil so it's won't be moisture.

It could be any, some or all of the following;
1, the brakes need bleeding.
2, the pads are contaminated.
3, the rotor is contaminated.
4, they just need bedding in.

Don't be tempted to 'drag' the brakes to bed them in. Do successive, hard stops from speed. This gives a final cure to the pads and they will last a lot longer.

I've gone through sets of pads in a single ride - both 'v' and disc brakes - so bedding in the pads is worth it.

[Tim330]

mk1fan said:

Shimano run mineral oil so it's won't be moisture.

It could be any, some or all of the following;
1, the brakes need bleeding.
2, the pads are contaminated.
3, the rotor is contaminated.
4, they just need bedding in.

Don't be tempted to 'drag' the brakes to bed them in. Do successive, hard stops from speed. This gives a final cure to the pads and they will last a lot longer.

I've gone through sets of pads in a single ride - both 'v' and disc brakes - so bedding in the pads is worth it.

I thought it would be slow, gentle braking to bed in. At least thats what I've always done on my car/motorcycle with new pads. What is the difference with the material type that means hard stops are better please?

[Trevelyan]

Just so you don't panic about some of the comments above, I've got M575 brakes on my bike and have had the same pads for 2000 miles now. Bed them in properly and keep them free of sand etc. and they should last fine.

[mk1fan]

Tim330 said:

I thought it would be slow, gentle braking to bed in. At least thats what I've always done on my car/motorcycle with new pads. What is the difference with the material type that means hard stops are better please?

There's a slight difference in the forces involved between a car and a push bike!

The brake pads are similar (being very general here) in that they are a back plate with a wearing material added to it. To get the high temperature into the bicycle pads though, you need to do hard braking as there's (relatively) little force being dissapated. Doing slow, gentle braking [on a bicycle] just doesn't generate the high enough heat to do this final cure.

There's also a tranferance of materail from the pad on to the rotor but that's starting to get a bit technical.

Bed the pads in properly and they will last a lot better than just using them. Doesn't take long 5-mins maximum.

[caiss4]

I've done about 9000km over 3 years and the rear wheel has just had its 3rd set of pads whilst the front is still on the second and I don't expect to have to change them for some time yet.

As for the 'soft' feeling providing the brakes have been bled properly then it's almost certainly bedding in that's required. I noticed a significant improvement in the braking feel after a couple of hard braking descents following the recent replacement.

[Tim330]

To update I've just been out on 3m road circuit I run round. I did about 10 hard stops from flat out. By about the 5th stop I had to ease off to prevent going over the bars so the brakes are now fine. Thanks for everyones input.

The bike itself is much better than the last one. It feels much lighter, Ive gone from a 19" to 17" frame though which probably helped.

[WeirdNeville]

They just need bedding in. My new bikes brakes went from uninspiring to frankly awesome over two 20km rides. They bed in and just provide loads of bite, and are much less fatiguing on your forearms on long descents etc.
That said, the lever response is a little 'spongy', not a dead stop like you get from cable brakes.