Another joyous hydraulic brake thread

[Jody]

Front brake has started acting up in the last month. It needs a couple of heat cycles through before it will stop properly with full power. Used from cold it just doesn't have any power. If you ride for an hour or so without using the brake it can loose its power again.

Lever feels fine, no oil leaking from the caliper and I don't use spray type lubes.

Any ideas?

 

[Yellow Saddle]

I don't understand.

Is the lever slack and then gradually pumps harder or;

Does the bike not stop at first and then later on stops?

 

[Jody]

I don't understand.

Is the lever slack and then gradually pumps harder or;

Does the bike not stop at first and then later on stops?

The lever is as normal at its usual bite point, no change in its feel but there is no bite to the pads. First pull is yank on the lever, lots of pressure and very little happens, second pull gains a bit of bite with less pressure and third/fourth pull is back to normal with one finger over the bar type braking.

Feels like when you have to bed a new set of pads in but every ride.

 

[Yellow Saddle]

OK, I understand.
Can we assume that you have checked that the pistons can move freely and that there is indeed pad material left?

 

[Bodhbh]

You don't store the bike upside down or anything funky like that? Does it get up-ended in any other way before you ride it?

 

[Jody]

OK, I understand.
Can we assume that you have checked that the pistons can move freely and that there is indeed pad material left?

Pistons are moving freely and retracting OK. There is still plenty of meat left on the pads. Standard finned Shimano resin pads used.

 

[Jody]

You don't store the bike upside down or anything funky like that? Does it get up-ended in any other way before you ride it?

Stored normal and not usually tipped upside down. Can do when it travels in the car but it doesn't cause an issue.

 

[Yellow Saddle]

I can only guess that the pads and discs are badly glazed and provide no adherence until the pad has heated up a bit.
Could you perhaps post a good photo of the pad's surface, as well as the disc's?

 

[I like Skol]

I put my money on contaminated pads. Have been in this situation myself and no amount of pad Sanding or cleaning would cure the issue. New pads were the answer, which smarts a bit when you are using finned Shimano pads because they can be quite pricey and not something you want to throw away if lots of meat remain!

 

[Drago]

Some folk put the pads through the dishwasher.

 

[Jody]

I put my money on contaminated pads. Have been in this situation myself and no amount of pad Sanding or cleaning would cure the issue. New pads were the answer, which smarts a bit when you are using finned Shimano pads because they can be quite pricey and not something you want to throw away if lots of meat remain!

It does feel like a contamination issue but can't work out why it goes away every ride. It will smart a bit as they are not cheap but have managed two years up to now but they have great feel and stopping power so don't mind so much.

 

[Jody]

I can only guess that the pads and discs are badly glazed and provide no adherence until the pad has heated up a bit.
Could you perhaps post a good photo of the pad's surface, as well as the disc's?

Will see if I can sort a pic tonight. Might swap the pads round to test @I like Skol 's theory.

 

[Yellow Saddle]

Will see if I can sort a pic tonight. Might swap the pads round to test @I like Skol 's theory.

It's not that simple though. Some stuff transfers invisibly and indelibly to the disc itself. Don't throw new pads at a contaminated disc.

 

[I like Skol]

I tried the dishwasher, sanding & IPA but nothing worked.

EDIT: But they were really clean......

 

[fossyant]

And thoroughly clean the did. I'd say new pads. Take a look at Uber Brakes. I have a pair of race matrix as spares when the SRAM one wear out.