In case of use: front caliper bleed nipple info

[billy10]

I had to replace the original part a few years ago and did so with a stainless item from Motorworks. Have had problems with the nipple sealing properly after bleeding, and in the end have worked out why. The base of bleed valve on stainless replacement is a different shape to the original part, and this appears to have caused problems seating it. Have now replaced with Stahlbus which has same seat shape as original, and problems fixed. To give you an idea, i could only seat the stainless replacement at higher torques otherwise it leaked even while the bike was left overnight (at the spec 10nm). Stahlbus nipples also get a much better result in terms of firmness and save a lot of faff. In case of use to anyone else

 

[billy10]

2008 GS with Brembo Evo front calipers (BMW marked on outside, Brembo marked on inside). M8 valves

 

[Bendy toy]

Stainless sounds great but electrolytic corrosion of the alloy will quickly seize the bleed nipple. It’s far better to use zinc plated carbon steel and replace when they get rusty (zinc depleted).

 

[billy10]

Interesting, thanks. Actually the stainless didn't seize at all in the 3 years I had them in the calipers (althought the OEM nipples did seize). On removal there was no corrosion on the threads or the seats of the nipples. Do you think there might be some corrosion in the alloy seat of the caliper? New valve seals normally at specified torque so I assume not.

Stahlbus item appears to be titanium. Do you have a view on how appropriate that is?

http://www.stahlbus.com/info/images/Downloads/Flyer_Entlueftungsventil_englisch-web.pdf

Was planning to subscribe and post photos to show the different seats of the valves but on reflection don't think I will be subscribing.

 

[Popell]

Each to their own but for 12nicker you won’t find better value for money in a long time.

 

[Bendy toy]

My Kettle brakes were rebuilt 5 years ago and ever since the bike has been dry stored. The aluminium around the stainless bleed nipples has oxidised and lifted the paint. Thankfully the threads are all ok. Had I used zinc plated carbon steel there would have been no problem.

Titanium is even worse than stainless for corroding aluminium. Zinc is below aluminium on the galvanic scale so will corrode/erode first. The nipple is ready for replacing when the underlying steel goes rusty.

https://www.corrosionpedia.com/an-i...s-galvanic-compatibility-and-corrosion/2/1403