Hi thanks for looking!

I bought some Formula T1s brakes about 5 months ago. I attempted to bleed the rear and the seals were blown at the calliper, leaking air into the syringe.

I took them back and the mechanic has now claimed that I had bled them with Mineral Oil and that the seals had expanded.

Frankly, this is nonsense. I didn’t even own mineral oil until last night when I bought some XT brakes. He has stripped the lever and the bladder in the master cylinder has expanded to ‘twice the size’, has anyone any idea why this would happen? I have ridden in some pretty hot conditions but surely that wouldn’t cause the bladder to expand?

So, I need advice! How do I argue my case?

Cheers, advice much appreciated.

Hmmmm. Only thought is gt85/wd40 type water dispersers.

gt85 can have a similar effect ie swelling/failure on seals/etc of dot-fluid brakes. (iirc the overzealous use of gt85 posed a frequent problem with avid juicys back along)

-are you sure you couldn’t have got some on/in the lever when cleaning/lubing/removing anytning else on the bar? IIRC there will be a little breather hole inside the bar clamp that has the bladder/bellows bit behind it and I would imagine that would be a weak point in terms of a contaminant getting inside and sitting there unnoticed until failure of the bladder.

Aha! Could be onto something there, yes there is a little breather hole on the master cylinder body with the bladder behind it. I’m not a user of wd40 or any water disperser really though.

Surely a great deal of water disperser would have to get in though before expansion?

Thanks!