A couple of basic questions about brake pedal adjustments

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Photoguy
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A couple of basic questions about brake pedal adjustments

Post by Photoguy »

For those that have been following along in my quest to expand the legroom of my bike, I've installed a set lowering brackets. Tundra Dweller has been extremely helpful with my questions about adjusting the shift and brake lever to accommodate the lowered pegs but I don't want to be a pest so I thought I'd throw this next (hopefully last) question out to the board.

I'm good to go with the gear shift lever height. I've left it's height untouched. It's only slightly awkward now that the peg is lowered so I'm focusing on the brake lever (pedal). I had a thought of making a bracket to offset and only lower the rubber part of the lever (what your foot actually pushes on) but discovered that the rubber part isn't easily removable from the rest of the arm without drilling it out and I don't want to ruin the lever in case I decide to go back some day.

So, I've decided to adjust the lever itself by shortening the plunger that goes into the master cylinder (I turned it away from the master cylinder as far as it would go) and then by lengthening the bolt that closes the switch so that it contacts the switch. Since I only needed to lower the lever by 3/4" or so, this seems to have worked out fine.

My question is: how do I know that I've got enough free play in the lever? The rear wheel turns when the bike is on the center stand. Not entirely freely but seemingly with the same resistance as was there before I touched anything. A test ride showed that the rear brake worked just fine, but I keep thinking that there must be some kind of quantative measurement for the 'free play' part. Right? I mean, these engineers are German after all, I can't imagine that they'd simply go by 'feel' :lol: So, is there some kind of measurable quantity of 'free play' for the rear brake pedal, something an unskilled mechanic like myself can actually measure? ...or should I just ride off in comfortable ignorance? :lol:
Thanks as always!
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sykospain
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Re: A couple of basic questions about brake pedal adjustments

Post by sykospain »

Yes, there should be a millimetre or two of free play in the pedal's downward movement before it compresses the hydraulic fluid in the master cylinder to lock the rear wheel.

As follows : - with the bike on the centre stand, check for free movement of the rear wheel - moving it round by hand. There's a certain amount of inertia due to the drag caused by the shaft mechanism, but you should be able to turn the wheel without too much difficulty. But it won't spin freely like the front wheel would.

That's OK. Now, gently press the pedal, taking up the tiny amount of free play in the movement downwards. As soon as you feel any resistance in the pedal's movement, the rear wheel should lock on solid. Then you're OK. kushtie....
It's not like the cable-operated clutch lever on the handlebar, where for correct operation you have a measured amount of free play in millimetres at the lever before the friction plate starts to move. No, the rear wheel's brake pedal free play is just a natch - not a measured amount.
If the stopping effect feels in the least spongey, simply bleed the rear brake hydraulic fluid of air. Takes quite a while, surprisingly, to rid that comparatively short circuit of hidden air.
This is the list of people I'd trust with my bike
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sykospain
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Re: A couple of basic questions about brake pedal adjustments

Post by sykospain »

Yes, there should be a millimetre or two of free play in the pedal's downward movement before it compresses the hydraulic fluid in the master cylinder to lock the rear wheel.

As follows : - with the bike on the centre stand, check for free movement of the rear wheel - moving it round by hand. There's a certain amount of inertia due to the drag caused by the shaft and final drive mechanism, but you should be able to turn the wheel without difficulty. But it won't spin freely like the front wheel would.

That's OK. Now, gently press the brake pedal, taking up the tiny amount of free play in the movement downwards. As soon as you feel any resistance in the pedal's movement, the rear wheel should lock on solid. Then you're OK. kushtie....

It's not like the cable-operated clutch lever on the handlebar, where for correct operation you have a measured amount of free play in millimetres at the lever before the friction plate starts to move. No, the rear wheel's brake pedal free play is "just a natch" - not a measured amount.
If the stopping effect feels in the least spongey, simply bleed the rear brake hydraulic fluid of air. Takes quite a while, surprisingly, to rid that comparatively short circuit of trapped air.

And remember, trapped air means condensation - means wetness, means eventual rust. Horror ! !
This is the list of people I'd trust with my bike
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Photoguy
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Re: A couple of basic questions about brake pedal adjustments

Post by Photoguy »

Many thanks! That’s a great explanation and confirms that my intuition was at least in the right direction-
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