Trialtech rim brake leaking in winter

[DYAKOV]

I’ve got carthy levers on new shape magura pistons front and rear. I’d been using the setup for a full spring/summer/autumn seasons and when weather got cold in the winter last year my brakes started leaking from the lever pistons.

I got in touch with trialtech to ask if changing to alu pistons would make things better. They advised not to because the lever body is made of a very soft alloy and the alu piston might scratch it. Their tip was to change all seals and a general service + use their fluid which would grease the whole system as well as won’t freeze/expand/get absorbed in the rubber/plastic components etc.

Got new seals (the carthy setup incl a silicone seal and an o-ring) and bled with the trialtech fluid. Brakes stopped leaking for another spring/summer/autumn and last week during a ride the rear started leaking again so badly that every 15-20min my lever would bottom out completely and I kept topping up the fluid.

Got home, changed the o-ring which btw looked brand spanking new - brake was still leaking.

Removed the silicone seal and switched to a double o-ring setup - brake started running super slowly, not returning well and still leaking.

Is it possible that the piston shrinks because of the weather? I mean it’s chilly but surely not that cold if we’re talking physics…

 

has anybody else had the same issue? Should I just bite the bullet and switch to an alu piston instead (never had issues with alu pistons)? Anything else I might have not considered?

 

Cheers,

Nas

[Tidy]

If your running a double o-ring, alu piston will be fine i never had a problem doing that with mine. Just check the the walls for any damage/ware before assembly to rule out ruined lever.

Slow return was friction from my o-rings, i doubled up the springs and lubed everything, and ran fine for years.