Dammit’s adventures in mountain biking

I’m calling @edscoble randonneurgate

Given that Ed eventually got that tyre on (?) I would be delighted to be in the same category.

Just tell us it is so.
We believe.

Ok, upper two pistons- if both retracted and the brake lever operated then only the external piston moves. If you hold the external piston in with a tool then the inner piston moves. Once you start the inner piston from its bore then it continues to move, even when you stop holding the external piston.

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Ok, bleed port on the lever is leaking, so at least that's one (maybe the) fault found. Which is something of a relief.

I'll fix that, then see if the pistons start behaving.

For those unfamiliar with the Magura lever design they're a single design that mounts on either side. Why am I mentioning this? Because in order for the lever to mount on either side they have a bleed port on both sides, so whichever side the lever is mounted one will be on the top.

Both my bleed ports are leaking - so the one under the lever that has, to my knowledge, never been touched.

Bit of PTFE tape might help you out.

bleed port on the lever is leaking

Right, I don't suppose you keep that Klein in the parts bin? You have my address yeah? :)

Leaky bleed port would maybe explain why some of the pistons weren't moving when the lever was pulled. Oil/air being displaced out through the bleed port instead of moving the pistons?

These brakes are, and I don't say this lightly, going to fucking work.

I know I've often said Magura are shit but I've never really thought that they actually are shit.
But theres no way that all mt7's can be this much of a ball ache. Maybe theres a dodgy batch?
Any more issues after this and I'd probably ask for a warranty replacement on the whole lot.

Leaky bleed port would maybe explain why some of the pistons weren't moving when the lever was pulled. Oil/air being displaced out through the bleed port instead of moving the pistons?

At a guess I'd say that what's happening is that when the inner pistons are in their bore the resistance to initial movement is greater than the resistance of the seals in the bleed screws, so fluid pushes past them. When the pistons are started out of their bores then the resistance of the seals is slightly greater than that of the piston, so the piston moves.

And whatever the position of the pistons in their respective bores, moving both at the same time is always a greater resistance than the seals in the bleed screws.

I know I've often said Magura are shit but I've never really thought that they actually are shit.

But theres no way that all mt7's can be this much of a ball ache. Maybe theres a dodgy batch?
Any more issues after this and I'd probably ask for a warranty replacement on the whole lot.

The lever is new, a replacement I bought in the UK from a local bike shop.

At a guess I'd say that what's happening is that when the inner pistons are in their bore the resistance to initial movement is greater than the resistance of the seals in the bleed screws, so fluid pushes past them. When the pistons are started out of their bores then the resistance of the seals is slightly greater than that of the piston, so the piston moves.

And whatever the position of the pistons in their respective bores, moving both at the same time is always a greater resistance than the seals in the bleed screws.

Yeah I'm nodding my head in agreement here.

The lever thats leaking is the new one?
Your patience with these is commendable, I'd have had a complete melt down by now.
I don't think it too much to ask that top shelf brakes should be able to go 6 months at the very least without having to be bled or fucked about with.

Or LS-X (liquid PTFE).

Wouldn’t think the seals on the bleed port would be bearing any kind of pressure unless something has gone wrong - like the brake being over filled or the seal on the master piston being bypassed.

Yes, that’s what a chap at Tarty Bikes thinks. I’m open to having over-filled them, but I can’t spot where it happened in this process:

• Bike in stand, wheels off
  
• Rear calliper pads pushed back, pins out, pads out, spacers fitted, pins in
  
• Lever bleed port screw removed, syringe with hole in fitted
  
• Bike angled so rear calliper above lever, bleed screw removed, syringe fitted, bike back to normal angle
  
• System bled, pushing and pulling fluid through, brake lever operated to push fluid down from upper reservoir to lower as this releases air bubbles, smooth pulls and “pings”, bars moved through full range of motion as this is done as different angles free more bubbles
  
• Upper syringe removed, small amount of fluid dropped into bleed port, bleed screw fitted (doesn’t stop rotating, worryingly)
  
• Bike angled so rear calliper above lever, syringe removed, small amount of fluid dripped into bleed port, bleed screw re-fitted
  
• At this point I dicked around cleaning and lubing pistons for a while
  
• Piston spacers out, pads in, pins in, rear wheel refitted, lever operated a lot, leaks observed
  
  

Looking at it in daylight it could be that fluid leaking from the upper bleed screw has run down onto the lower, kind of hard to tell.

If Maguragate continues I'd suggest ditching them for some TRP Quadiem G-Spec. Best brakes I've ever felt. Also hard to fault Saints for beefy braking...

TRP

absolutely not, 5.5mm hose ?!?! NO

shimano only pls

Doesn't help with the levers, but ime pistons often extend at different rates when the wheel is out - its pretty normal. Once the disc is in and there's something to press against they balance & work fine.

It's not all about the size...

I am actually removing TRPs from cargo bike to put some shimano 4 piston because I know everything about the bleed, have plenty of spare BH90 and pads are cheap and plentiful

shimano is the truth

@Dammit I have the XTR M9100 levers on MTB and they are amazing, get the set (didnt you have on scalpel?)

Those are extremely good brakes and @amey doesn't deserve them

I had those XTR on the Scalpel, once I dealt with a contaminated set of pads they just worked.

But I'm probably in for close to a grand, trying to make the Magura work, so the sunk cost of my fallacy is significant.

For home mechanics you can leave it overnight. Workshops, not so much.

Exactly, time is money also.

But I'm probably in for close to a grand

Fuckkkkkk. Could have got some Maximas for that.

Sorry I know that's extremely unhelpful but I am impressed by your perseverance! I would have sent everything back for a refund long before now.