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Frankenbrakes and brake improvement discussion

Bikael Molton

goofy for life
Jun 9, 2003
3,861
1,000
El Lay
Question for Shimano guys,

I have found the "air issue" to only happen with the rear brake. Front has been solid and dead consistent.
Is this true for the rest of you?
Same here with my XT785s. Flip bike over for a minute and it needs the 2 pump rollover afterwards. Cant think of a scientific reason for issues with rear only though.

Related topic... Riding grabby XTs with baby-knob XC race tires is a scary-skid-happy experience. And my knee has a hole in it to prove that.
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,897
1,162
Talked to a friend of mine and he is riding MT7 calipers with Shimano Saint levers. He says it is fantastic. Stronger than with stock lever, much better feel. He says that he feels like pads from one side of the caliper last longer, but he is riding stock pads since the begining of the season, and it is not such a big deal.
Sounds good to me, how about lever throw inconsistencies / variations though? How does the total lever throw compare to standard M820s?
 

troy

Monkey
Dec 3, 2008
901
545
Sounds good to me, how about lever throw inconsistencies / variations though? How does the total lever throw compare to standard M820s?
No complains whatsoever. He says that Saint lever is much stiffer. Magura lever was so flexy, that it was making some noises. Lever throw similar to saints, and no spongy feel at all.
 

kidwoo

Artisanal Tweet Curator
Aug 25, 2003
33,352
8,002
The old timey times
Yup.

It's terrifying.




I think I'm gonna try some magura mt 5 calipers. I just looked and in the US the calipers are more expensive than buying a whole brake. :rofl:

Anybody want some flexy magura levers?
 
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csermonet

Monkey
Mar 5, 2010
940
123
yes me too, only the rear one.
my brake setup is irrelevant to this thread(i am using Formula t1's and Oro Biancos which both use DOT), but my rear brake is always more finnicky than the front. I think the rear brake are more caused by the longer hose length and more direction change in the hose. does anyone else have a theory on this?
 

frango

Turbo Monkey
Jun 13, 2007
1,454
5
I've got Sram Guide RSC with Glory 2015. Even though, I've been on XT 785 for few years, I've decided to give Sram another chance...
Total waste of time :( Rear brake with bubbles in the system out of box. Rebleeding several time didn't give any results. So, i've decided to go back to Shimano.
So, since I am not that good at math ;) Here come my question.
What would be practical result of pairing XT M8000 (or M785) lever with Saint caliper?
Will I get similarly powerful brake?
Will there be significant change of lever throw?

Thx for advice :)
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,897
1,162
So, since I am not that good at math ;) Here come my question.
What would be practical result of pairing XT M8000 (or M785) lever with Saint caliper?
Mike Kazimer said:
I found that the M8000 brakes had an inconsistent lever feel on extended downhill portions of the trail, occasionally pumping up during sustained braking.
From: www.pinkbike.com/u/mikekazimer/blog/first-ride-shimano-deore-xt-m8000.html

IMO all current Shimano levers have something like a 40% problem rate, it's up to you if you want to roll the dice. You might get a trouble free set or you might not. I'd be more inclined to use something like a Deore/Zee/SLX lever so it's a cheaper gamble, there isn't a functional difference aside from adjustment (Deore now has servo wave so the lever design is the same). Throw and power should be the same in all cases.
 

frango

Turbo Monkey
Jun 13, 2007
1,454
5
From: www.pinkbike.com/u/mikekazimer/blog/first-ride-shimano-deore-xt-m8000.html

IMO all current Shimano levers have something like a 40% problem rate, it's up to you if you want to roll the dice. You might get a trouble free set or you might not. I'd be more inclined to use something like a Deore/Zee/SLX lever so it's a cheaper gamble, there isn't a functional difference aside from adjustment (Deore now has servo wave so the lever design is the same). Throw and power should be the same in all cases.
Since price difference is not a problem, I'd like to have same levers, but stronger front brake.
Don't 4 pots make a difference? Amount of moved fluid, etc?
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,897
1,162
so are we mostly satisfied that the answer to the shimano problem is leaky calipers allowing air into the system, which works its way into the MC and then alternates between reservoir and line? So you could in theory grab a different caliper to reduce leaks or another lever to reduce leak effects.
I missed this one, but no, personally I don't really think this is a common scenario. I have never personally seen an M810, M820, or M640 caliper develop leaking seals, yet these brakes still suffer from the same lever issues that the M785 does (which do develop caliper seal leaks). To me this says that the problem is at the lever. In fact I've seen people replace the levers alone and have the problem go away - I can't say if permanently so, but it's enough to isolate the cause.

MT5 or MT7, because MT5 pads are different than MT7's. They have common, much thicker back plate. MT7 pads are separate for each piston with thinner back plate (and thicker friction material), so MT5 shouldn't suffer that much in theory (?).
That's not an accurate theory, because the uneven pad wear was on the L vs R side of the caliper, not between individual pads on the same side. Joining the pads together would make zero difference in this case - in fact the offending item was an MT5. It may be an isolated issue, but I read a few more cases when I looked up reviews.
Enduro Magazine said:
"After a second pad change, the (on test) Magura MT7 brakes are removed to be replaced by Sram Guides. The last set of rear pads (MT5 model) lasted one muddy ride! Both front and rear have completely uneven wear, one side worn out and other side still fine"


Since price difference is not a problem, I'd like to have same levers, but stronger front brake. Don't 4 pots make a difference? Amount of moved fluid, etc?
Yes, the 4-pots are more powerful and result in longer throw due to greater slave piston area. The levers use the same master cylinder diameter (and mechanical leverage curve to my knowledge - if it's different, it's not significant) which is why the M820/M640 brakesets have an excessively long lever throw. My point is that using the M785 lever on the M820 caliper will make no noticeable difference compared to an M820 lever on M820 caliper - however if you have a complete M785 brake set and swap the front caliper for an M820, you'll get increased lever throw on that brake and have a throw mismatch L/R.
 
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troy

Monkey
Dec 3, 2008
901
545
That's not an accurate theory, because the uneven pad wear was on the L vs R side of the caliper, not between individual pads on the same side. Joining the pads together would make zero difference in this case - in fact the offending item was an MT5. It may be an isolated issue, but I read a few more cases when I looked up reviews.
Oh, I thought they were wearing from uneven piston movement on each side (have seen that many times in Codes). I have noticed similar behavior with my Louise calipers, one piston is always sticking out a little more than the other, but it is not as extreme difference as in this picture, that you have posted. Sometimes pistons get sticky in magura calipers (tight seals) and it helps to hold the other piston with something and pump the lever few times, to lubricate the sticky one, maybe that is the case.
 

TrumbullHucker

trumbullruxer
Aug 29, 2005
2,284
718
shimzbury, ct
alright so i am going to re-bleed both front and rear zee's this week
i've had the shimano bleed kit ( with the small "bucket" and plunger type deal

i have seen alot of different methods.. but i would really appreciate you guys filling in the blanks for me

- put the levers parallel with the ground
-screw in the "bucket" into the lever with plunger snugged into the hole
-put hose and a "drain" (plastic bag, whatever) on the caliper, unscrew the nipple 1/4 turn
-keep filling and filling the bucket at the lever( i have a shit ton of mineral oil, i bought the big 1 liter container)
-random flicks and or vibratory action to the lever and hose and caliper to hopefully escape all air?

... after that i'm not really sure how to properly finish the bleed. there are so many different articles; im not sure which one is the best way. I would rather have a bunch of tips from monkeys

commence!
 

Nick

My name is Nick
Sep 21, 2001
21,917
10,255
behind you, don't wait up.
the only thing I do differently is after installing the bleed cup and hose/syringe to the caliper nipple, I pull the lever as hard as I can and then crack the bleed nip, close nip, release and re-pump lever, crack nip, repeat.

I also swivel my handlebars to the left, tap hose, bleed, then to the right, tap hose, bleed, just to encourage any air near the master cylinder to break free and escape into the bleed cup.

Other than a leaky 810 caliper I've had great luck with all my various Shimano brakes.
 

frango

Turbo Monkey
Jun 13, 2007
1,454
5
however if you have a complete M785 brake set and swap the front caliper for an M820, you'll get increased lever throw on that brake and have a throw mismatch L/R.
And this is what I feared of :(
It seems, that it's better to just use different but complete set of M785 (or M8000) on the rear wheel and M820 on the front.
Thanx, Udi!
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,897
1,162
Still waiting on someone to measure Hope Tech3 and Race MC for me, would be appreciated for the benefit of all.

@troy
Yeah entirely possible that piston lubing would help, but in general I feel I shouldn't need to do that on any brake before it's 1-2 years old (that's how long before I've done it on Shimano/Formula in the past, Avid not so good!). Cheers for the Magura data, I have added it. The Julie is interesting (large pistons and low pressure), and so is the low ~5.0 hydraulic leverage on the Gustav. Big long mechanical lever.

And this is what I feared of :(
It seems, that it's better to just use different but complete set of M785 (or M8000) on the rear wheel and M820 on the front. Thanx, Udi!
Maybe you misunderstood, if you use a complete M820 on front and complete M785/8000 on rear the result will be the same (throw mismatch L/R). The hydraulic and mechanical leverage of the M820 and M785 levers are similar if not the same, so the throw increase is due to the caliper, there's no need or benefit to purchasing the M820 lever (for you). If you want a throw match you need M820 caliper both ends, or M785/8000 caliper both ends. With that said - you could still try an 820 caliper just on the front, it's possible that it may feel okay, purely because rear brakes can sometimes have longer throws than the front (even though they technically shouldn't) - and the 'longer' front stroke may be closer to a match in practice than in theory. :)

-random flicks and or vibratory action to the lever and hose and caliper to hopefully escape all air?
I've found that with the reservoir open (bleed nipple closed), flicking the brake lever tip by compressing it and letting it snap back (under spring force) helps dislodge plenty of stuck air bubbles in the lever. You can watch them pop up in the reservoir (in this case you want the res filled with oil, bladder and cap removed like in the old days).

Another tip (this one from the Shimano manual) is to hold the brake lever compressed (w/nipple shut + tubed), and quickly open and close the nipple to encourage any bubbles out of the caliper. In both cases watch that reservoir or cup level doesn't drop too far.

The other piece of general advice is, if you're doing a fluid flush be careful to not introduce any new air - that way the system is mostly bled already. Don't empty the system first or let the reservoir run empty during your flush. My final tip would be to alcohol wipe the nipple and surrounds not just after the bleed but regularly for the next few rides, as it seeps out for a while after bleeding and can contaminate things if not checked.
 

frango

Turbo Monkey
Jun 13, 2007
1,454
5
Maybe you misunderstood, if you use a complete M820 on front and complete M785/8000 on rear the result will be the same (throw mismatch L/R). The hydraulic and mechanical leverage of the M820 and M785 levers are similar if not the same, so the throw increase is due to the caliper, there's no need or benefit to purchasing the M820 lever (for you). If you want a throw match you need M820 caliper both ends, or M785/8000 caliper both ends. With that said - you could still try an 820 caliper just on the front, it's possible that it may feel okay, purely because rear brakes can sometimes have longer throws than the front (even though they technically shouldn't) - and the 'longer' front stroke may be closer to a match in practice than in theory. :)
I will think about it.
Thx!
 

troy

Monkey
Dec 3, 2008
901
545
@Udi Julie brakes were in 2 versions High Pressure and Low Pressure, don't know what is the difference between them. IIRC in some VERY olde Julie models had only 1 moving piston, newer ones probably had 2x28mm moving pistons and the newest model (HP ver.) had two moving pistons, but it looks like it was just a Louise caliper with different lever.

Any1 had one of those and can verify that?


According to this, it seems like they have 2 moving pistons:
http://www.magura.com/uploads/media/downloads/JULIE_08_E.pdf
 
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troy

Monkey
Dec 3, 2008
901
545
Ok, Magura Julie caliper from the picture above, has two, 28 mm diameter, moving pistons. [confirmed]

@Udi are You 100% sure about Formula MC diameter? Long time ago my T1 MC seal failed and I had ordered some custom made copy of the original seals. I have one of those left and from my measurements it is clear that it has to be for a 11mm MC. No way it would fit 10mm bore.

Some data for You:

Magura Louise lever dimensions:

Blade tip to pivot distance [red] : 110mm
Lever pivot to cam [don't know how exactly you have measured it- I've measured a distance from the center of the lever pivot to the place where blade lever cam meets MC pushrod (??)]
[blue]: 10mm (long reach) and 11mm (short reach)

Main pivot position is adjustable (reach adj.) [orange]: 2.5mm range
louise blade.jpg


1 more thing - Magura and some of the Formula rotors are 2mm thick, Shimano/Hayes/Avid rotors are 1.8mm thick.
 
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yd35

Monkey
Oct 28, 2008
741
61
NY
did a successful bleed with new pads on my Zees at the race at blue this weekend

i dont know why you would need a stronger brake... felt great
If you get a reliable set of Shimano brakes, power is definitely not an issue! Where people have a legitimate gripe, IMO, is in the modulation department.
 

Kanye West

220# bag of hacktastic
Aug 31, 2006
3,680
405
Well I spent my time at Whistler riding, and not mic'ing brake part diameters, although that's in large part because I didn't have a mic or a caliper...

Will have my bikes back from their alternate mode of transport in a couple weeks and I can measure then if you still don't have it.


My Hope V4 brakes did hold up flawlessly however. Not a single change in feel over the course of any top to bottom runs, or over the course of the week up there. Never once felt a need for more power.
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,897
1,162
Will have my bikes back from their alternate mode of transport in a couple weeks and I can measure then if you still don't have it.
Yeah that'd be great, no one else is providing it so I'd appreciate that. I assume it's the Tech3 lever.

I scored a deal for a friend on the Tech3 V4 recently so will try it out soon, hopefully it's as good as you say.

Ok, Magura Julie caliper from the picture above, has two, 28 mm diameter, moving pistons. [confirmed]

@Udi are You 100% sure about Formula MC diameter? Long time ago my T1 MC seal failed and I had ordered some custom made copy of the original seals. I have one of those left and from my measurements it is clear that it has to be for a 11mm MC. No way it would fit 10mm bore.
Thanks for that - I just measured quickly, and not only is it not 10mm, it seems bigger than 11mm even. Are you sure of 11? It looks more like 12mm to me, although that seems a little crazy. I will get the verniers onto it later.

I will add you lever data when I get a chance to measure a few other levers, cheers.
 

troy

Monkey
Dec 3, 2008
901
545
@Udi Can't find that seal at the moment, but it was bigger than 11mm. 11.5ish most probably. Sealing O-Ring has ~11.36mm outside dia., so after putting it onto the MC piston it would fit 11.5 MC bore.
 

maxyedor

<b>TOOL PRO</b>
Oct 20, 2005
4,896
2,422
In the bathroom, fighting a battle
Anybody know the weight difference between Magura mt5s and 7s and who's got the best pricing? Scared the shit out of myself with my XTRs once again, so it's time to change, thinking about my old school LOuise levers which I've always loved with some quad piston calipers.

That or saint calipers with Magura Louise levers?
 

Flo33

Turbo Monkey
Mar 3, 2015
1,722
985
Styria
Anybody know the weight difference between Magura mt5s and 7s and who's got the best pricing? Scared the shit out of myself with my XTRs once again, so it's time to change, thinking about my old school LOuise levers which I've always loved with some quad piston calipers.

That or saint calipers with Magura Louise levers?
MT5 268.50 g

MT7 270.00 g

Zee Shermans have everything and even more NOx than promised - http://gewichte.mtb-news.de/ You should be able to navigate without sprechen Deutsch. If you need some help, shout it out loud, maybe I'll hear you.

Edit: I guess bike-discount.de will be the cheapest, again

MT5

MT7
 
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norbar

Turbo Monkey
Jun 7, 2007
10,517
968
Warsaw :/
Yes, the 4-pots are more powerful and result in longer throw due to greater slave piston area. The levers use the same master cylinder diameter (and mechanical leverage curve to my knowledge - if it's different, it's not significant) which is why the M820/M640 brakesets have an excessively long lever throw. My point is that using the M785 lever on the M820 caliper will make no noticeable difference compared to an M820 lever on M820 caliper - however if you have a complete M785 brake set and swap the front caliper for an M820, you'll get increased lever throw on that brake and have a throw mismatch L/R.
I'm a bit sleep deprived and stupified after watching a mexican cartoon for work so it may be a stupid question but how does the greater sleve piston area relate to old gustav 2 piston brakes? I remember that while lever was really long the later model lever (plastic, not cast) was really consistent and I'd still run them if not for the weight.

Also I've heard great things about hope v2's. Rode them (2011) and they felt great. Do we have the difference between different hope tech lever generations?

btw. I still run 220mm formula on my 810's.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
19,458
3,488
01776
AFAIK there's no difference in the caliper, only in the lever. Some reports of the mt7 lever being flexy.

I've read one or two comments that the mt7 caliper is made in germany, while the mt5 is taiwan, but I doubt that very much.

"King barcelona" has the cheapest price I've found shipped to the US.
 

StiHacka

Compensating for something
Jan 4, 2013
19,749
10,892
What's happening?
So, Saint lever + MT8 caliper -> so far so good, def mucho better than the awful plastic magura levers. I need to do some trail riding before the jury announces the verdict tho.
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,897
1,162
@troy
I just set the spreadsheet so anyone can edit. Maybe you can change the columns to suit your measurements and make it work? Feel free to have a go, I can add my measurements later to fit your ideas. I only made temporary column names so maybe you'll have a better methodology (the tricky part will be for Shimano / other variable-leverage designs, but perhaps for those we can just use the values that give the highest leverage and replace my average/peak columns with peak-only data).

@norbar
The Gustav is interesting, if you check the spreadsheet it has very low hydraulic leverage, and uses a long mechanical lever instead - on the original version at least. I think this may have changed in a later version (shorter lever and possibly a smaller master piston to increase hydraulic leverage) but I haven't checked, troy might know.