Thumb Brake

[tombo46]

Ok, Ive avoided asking this question for fear of sounding like a burk. but has anyone tried making a thumb brake for the rear wheel on a trials bike? It seems like a very logical thing to do for a few reasons.

It could be an alternative way of holding the rear tyre when balancing instead of slipping the clutch, it can sometimes be hard when you have to take your right leg off the peg (and rear brake) for balance and find your front wheel starts to slip down the rock.

Wheelies! For balance and various other flashy stunty type things you sometimes need to take your foot off the peg! it would be very reasurring and very confidence boosting to know that you have another way to bring your bike back down to earth.

Saving you and your bike when you get a little throttle happy but need to maintain your balance. sometimes on nice big rocks where theres a smooth run up the front wheel can get pretty high, so you need to bring it back down once your over the obsticle, and sometimes kick a leg out to save a dab or to save binning the bike upon exiting the rock. personally I sometimes find it uncomfortable aproaching a rock for a jap-zap or something similar when I have my rear brake covered, it doesnt seem natural.

Im no expert but I would think it could be done pretty easily? you could take a front brake master clylinder and put it next to the clutch, with the lever running on the oposite side to the bar.

The only thing that Im not sure about is if there would be a loss in pressure, another brake line would have to be run from the master clyinder to the rear caliper. It wouldnt be much good if it impared the use of your normal foot operated brake. also, where would the line join? directly onto the caliper ontop of the other hose using a double connection of some sort?

I know alot of people will be thinking "whats the point? everyone does fine as the bikes are now" but im curious to see if it would work.

if anyone has any suggestions or obvious faults please let me know!!

All the best

Tom

[madalec]

This isn't really a thumb brake, but it sounds as though it's what you're after

http://www.clake.com.au/

[tombo46]

Ive seen that before, I dont think that would have the same effect, 2 flaw's i can see in it are that you can only bring your clutch in so far before your hitting your rear brake, which wouldnt be good for frantic clutch grabbing. also, I like my clutch to bite just away from my fingers and I think it would have to bit alot further out if it still has to allow travel for a rear brake to be applied. Ill have my new bike on tuesday so i may experiment a little bit with my old beta, only problem is that i hear the rear on a beta can be a bugger to bleed (never tried it).

All the best

Tom

[chris morris]

Is This what your on about?

Edited February 15, 2008 by Chris Morris

[dibdab]

Ive seen that before, I dont think that would have the same effect, 2 flaw's i can see in it are that you can only bring your clutch in so far before your hitting your rear brake, which wouldnt be good for frantic clutch grabbing. also, I like my clutch to bite just away from my fingers and I think it would have to bit alot further out if it still has to allow travel for a rear brake to be applied. Ill have my new bike on tuesday so i may experiment a little bit with my old beta, only problem is that i hear the rear on a beta can be a bugger to bleed (never tried it).

All the best

Tom

Funny you should mention this, I have thought about fittig a thumb brake to my bike.

I fancy the idea because I have ltd movement in my right ankle and so struggle a bit sometimes.

They are now readily avaialble for road race bikes, but quite expensive.

I have knwn a few roads racers rig something up before they came on the markey, so it is possible and worth playing about with.

If you look in a Demon Tweeks catalog or their website you will see them and it may give you a few pointers.

Keep us posted

Edited February 15, 2008 by dibdab

[tombo46]

where do you think the extra hose should fit? straight onto the caliper or elsewhere? To try it im just going to use a normal master cylinder, but may change for a proper thumb brake one as it will be more compact.

Tom

[slapshot 3]

Is This what your on about?

Chris that would be a BREAK rather than a brake.......that looks horrible

[kevin j]

do you think the extra hose should fit? straight onto the caliper or elsewhere? To try it im just going to use a normal master cylinder, but may change for a proper thumb brake one as it will be more compact.

Can't just tee them together as when you apply one master cylinder, the glycol would go back through the bleed hole into the other reservor.

You will need what is called a shuttle valve that take the higher of two signals and passes it through. Easily available for vehicle hydraulic systems and air brakes, but for brakes, this small I have no idea.

Both the action of the shuttle and the increased volume of the system will reduce the stiffness of the system, it will feel like there is some spongy or air in it.

Way more complicated, but you could put an entire second capiper and pads on the same disc. Original from foot, plus one from thumb. If you don't need as much power, maybe a MTB bicycle caliper added to the rear disc might work.

k