JT!

Magura MT4. Front is amazing, back is meh.

18 posts in this topic

Picked up a used Inspired Fourplay last year. The rear brake had been replaced under warranty but was sent to the owner without the line been cut to length. So he had it wrapped around the headtube about 5 times instead of cutting it down. So a few days ago I cut it down and bled the brake.

I realized I may have done it wrong the first time because where I wanted the bite point the reach screw was all the way in. I forgot to unscrew this out before I bled. So I re did it and it seemed better. But when I took it out for a spin today, there's no real hold on the brake compared to the front one which is shockingly powerful. Another thing I noticed is that the bit point seems to be changing as I ride. It'll get further towards the bars, but if I bring the bike up on to the back wheel and pump the brake it'll move further out. Is this a sign of air in the system still?

Also even though the brake caliper is absolutely center over the rotor, only one pad had a noticeable gap from the rotor, the other one seems to skim up against the disc. Would this be something that would happen if there's air in the system?

Thanks!

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Posted (edited)

Try doing Maguras 'fast bleed', I tried to bleed one of my MT7s a while back after routing the hose through the steerer tube but couldn't quite get it right until I did a fast bleed as per this video:

https://youtu.be/RtqwQB8wtYQ

Worth a shot as it only takes a minute, mine was perfect afterwards. 

 

Edited by Rip

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45 minutes ago, Rip said:

Try doing Maguras 'fast bleed', I tried to bleed one of my MT7s a while back after routing the hose through the steerer tube but couldn't quite get it right until I did a fast bleed as per this video:

https://youtu.be/RtqwQB8wtYQ

Worth a shot as it only takes a minute, mine was perfect afterwards. 

 

Done this like 8 times :lol:

Although I think I may have got it now. Pads are pulling in evenly and seems much more solid. Will take a ride tomorrow morning and see how it is.

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Just now, JT! said:

Done this like 8 times :lol:

Although I think I may have got it now. Pads are pulling in evenly and seems much more solid. Will take a ride tomorrow morning and see how it is.

Oh lol, hopefully you've already sorted it then :-)

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These are tricky to get right - even Magura can't do it. They can feel fine until you take the bike off road, or have a bail, or tip it upside down, when the trapped air is released and gets into the system.

Hopefully the following images will help...

 

tap.jpg

normalbleed.jpg

layout.jpg

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2 minutes ago, Adam@TartyBikes said:

These are tricky to get right - even Magura can't do it. They can feel fine until you take the bike off road, or have a bail, or tip it upside down, when the trapped air is released and gets into the system.

Hopefully the following images will help...

 

tap.jpg

normalbleed.jpg

layout.jpg

Those pictures are very handy. Mine are fine for the most part but the lever will go to the bar a couple of times after the bike has been upside down, after a couple of pulls they are perfect again. 

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Yep. Exactly the symptoms of these brakes with air in.

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Just now, Adam@TartyBikes said:

Yep. Exactly the symptoms of these brakes with air in.

Haha well I'm leaving them alone for now as they work perfectly when they are the right side up lol

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1 hour ago, Adam@TartyBikes said:

Hopefully the following images will help...

So are you suggesting a just take the lever off, hold it in this orientation, tap it, and then put the lever back on and done? Or should I do this then bleed again?

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Orientate / tap as described while bleeding.

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Ok I'll give this a shot. Thanks!

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Took it for a spin today and the lever felt solid and the pads seem to be moving perfectly now. No changing lever reach either. So I think maybe the issue is that it hasn't bedded in yet so I'll assume that's what's going on before I try again.

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I was having an utter nightmare trying to bleed up mt brakes until I tried this 

Create a vacuum to sick any trapped air out of the bleed port, it took a couple of tries but worked pretty well.

 

Now I'm leaving the bloody things well alone, never had as many problems bleeding up brakes than these maguras :S

 

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If you look at the photos I posted above, you can see why a vacuum technique won't work very well (and hence took a couple of tries).

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I made a power bleeder (adapted a car specific one to suit the bike) for the brakes on my old moto trials bike a few years back that connects to the front tyre valve (to give you pressure) and forces the fluid down through the system where you bleed it it off at the caliper. It turned out to be very good  because it always worked, it kept the whole system under pressure while you flicked the brake lever and shook the hoses about to release any trapped air bubbles. 

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Seems like I've solved the issue. After trying a few more times I still had issue with the lever pull being inconsistent even though I was convinced I'd got all the air out after trying all the advice given here.

What I was doing wrong with the syringe/vacuum trick was simply not pulling hard enough. Once I started really pulling on that thing a lot of air came out, and then a lot of tiny air bubbles too.

I knew I'd cracked it when I pulled the lever for the first time and once the pads had settled into position the bite point was closer than the front brake. To even get near to this point before I'd have to pump the brakes when the bike was upright, and even then it'd pull back in after a few mins. Went out for a test ride and on my first pump of the rear brake damn near went of the bars because I wasn't used to that kind of power.

Can't wait for it to fully bed in like the front has, but for I can actually gap up onto a curb without fear of death.

TL;DR wasn't pulling hard enough on the syringe.

Thanks all!

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Posted (edited)

Glad you've sorted it, I should have another crack at my MT7s soon but it's always a messy faff and very hit and miss as to whether it works so it's not a fun job. I'm always so paranoid about getting brake fluid on the rotors and pads as well so I usually take them off and put them in another room. 

I had to switch to Magura Comfort pads after my Performance pads bedded in because I went over the bars at least once every time I took the bike out! Far too much initial bite for me! Now I'm a bit more used to them I might try Maguras green eStop pads as they seem to sit in between Comfort pads and Performance pads on the Bite section of their graphs. 

Edited by Rip

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