magura interchangeability?
- Thread starter Bullpup
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suburbanreuben
Old School Grand Master
I've seen it done!
Not sure how effective it was .
Not sure how effective it was .
RadNomad
Senior Retro Guru
The hydraulic brake system is amplifying the applied force with mechanical advantage via hydraulic actuation. The MASTER cylinder piston has a small cross sectional area, moving a long distance with small force. The SLAVE cylinder (brake caliper) piston has a large cross sectional area, moving a short distance with large force. The slave and master piston sizes and strokes are selected such that both cylinders displace the same volume of hydraulic fluid while delivering the intended stroke and force to the brake pads.
This means that if you fit a different master cylinder with different dimensions, you are altering this relationship. A too-small diameter master piston with same stroke will reduce the required lever force to stop the bike in theory, but in practice will likely not displace enough fluid volume to complete the stroke at the caliper end, or at least will require longer lever travel. By contrast a too-large master piston with same stroke will definately displace enough fluid to give the caliper full stroke but you'd need to input more lever pressure to stop the bike as compared with the correct size master piston.
An untrained person could assemble a mismatched combination of master and slave cylinder and may find that it "works", but in reality some aspect of the assembly will be operating not as intended (master or slave pistons not running full stroke, seals of wrong sized cylinders exposed to higher fluid pressures than intended, levers running shorter or longer travel than intended).
For example, i considered using a 2012 Shimano XT lever/master to operate a Magura HS33 rim brake. The Shimano master piston had much smaller diameter (therefore cross sectional area) than the Magura's master piston, i didn't go as far as to measure stroke or displacement volume because it was already clear that i would be using a home-made and unproven resultant mechanical advantage. While it might've "worked" it was guesswork and that is not a very professional way to proceed on a safety system. In my view if you have a professional approach it's better to stick with correctly designed systems or if wanting to modify then at least determine the specs of the proposed alteration and make an evaluation. However if you're desperate or aren't bothered about expertise then you could try anything - but it isn't advisable. New front teeth are expensive!
This means that if you fit a different master cylinder with different dimensions, you are altering this relationship. A too-small diameter master piston with same stroke will reduce the required lever force to stop the bike in theory, but in practice will likely not displace enough fluid volume to complete the stroke at the caliper end, or at least will require longer lever travel. By contrast a too-large master piston with same stroke will definately displace enough fluid to give the caliper full stroke but you'd need to input more lever pressure to stop the bike as compared with the correct size master piston.
An untrained person could assemble a mismatched combination of master and slave cylinder and may find that it "works", but in reality some aspect of the assembly will be operating not as intended (master or slave pistons not running full stroke, seals of wrong sized cylinders exposed to higher fluid pressures than intended, levers running shorter or longer travel than intended).
For example, i considered using a 2012 Shimano XT lever/master to operate a Magura HS33 rim brake. The Shimano master piston had much smaller diameter (therefore cross sectional area) than the Magura's master piston, i didn't go as far as to measure stroke or displacement volume because it was already clear that i would be using a home-made and unproven resultant mechanical advantage. While it might've "worked" it was guesswork and that is not a very professional way to proceed on a safety system. In my view if you have a professional approach it's better to stick with correctly designed systems or if wanting to modify then at least determine the specs of the proposed alteration and make an evaluation. However if you're desperate or aren't bothered about expertise then you could try anything - but it isn't advisable. New front teeth are expensive!
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2 thoughts;
1. connect an empty syringe to the 2 levers and measure the fluid diplacement at typical lever pull. If they're the same, then you should be fine (depending on the answer to 2).
2. (I only know about Magura rim brakes) HS11/22/33 don't compensate for brake wear, you have to dial this in manually. Most disk systems can account for this, and push more fluid from the master cylinder into the system as needed. If the Magura disc lever compensates, then you're in for a world of pain...
My gut feeling is that a disc lever won't push nearly enough fluid.
1. connect an empty syringe to the 2 levers and measure the fluid diplacement at typical lever pull. If they're the same, then you should be fine (depending on the answer to 2).
2. (I only know about Magura rim brakes) HS11/22/33 don't compensate for brake wear, you have to dial this in manually. Most disk systems can account for this, and push more fluid from the master cylinder into the system as needed. If the Magura disc lever compensates, then you're in for a world of pain...
My gut feeling is that a disc lever won't push nearly enough fluid.
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I've been messing with hydraulic brake systems since 1996 which makes me super speshul and faffer extraordinaire
From memory and explained far better above, the magura lever doesnt move enough fluid or it moves far too much fluid (i cant remember which I'm afraid) - either way it doesnt work.
I remember using the ultra rare magura road lever and that also didnt work - it was mated to an early hope sport and it was 'wooden' and ineffective.
Early Hope levers were great with Formula single and twin pots, Grimeca/XT twin pots and a few others. The adjustable master cylinder was great in the cold weather as well as hot days, dialing it in and out to suit. I've mixed up a few others, Hayes, Coda and the like but its been a while now.
From memory and explained far better above, the magura lever doesnt move enough fluid or it moves far too much fluid (i cant remember which I'm afraid) - either way it doesnt work.
I remember using the ultra rare magura road lever and that also didnt work - it was mated to an early hope sport and it was 'wooden' and ineffective.
Early Hope levers were great with Formula single and twin pots, Grimeca/XT twin pots and a few others. The adjustable master cylinder was great in the cold weather as well as hot days, dialing it in and out to suit. I've mixed up a few others, Hayes, Coda and the like but its been a while now.
