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twist grip BRAKES! Possible or crazy pip dream?!

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twist grip BRAKES! Possible or crazy pip dream?!

Old 10-13-10, 06:46 AM
  #1  
zombieThemepark
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twist grip BRAKES! Possible or crazy pip dream?!

Okay, so I am currently building up an old mountain bike into something that is, I guess, a cruiser/mtb hybrid (so chopper-style handlebars, singlespeed, mtb frame, focus on looks over utility etc. etc.) and Iíve come up with an idea that I want to run past people that know much, MUCH more than I do about bicycle engineering.

What I want to know is, is it possible to purchase twist grip style brakes (NOT integrated with a gearing mech, like that Shimano thingy, as this is a singlespeed machine) and if not, would they be feasible to make/convert, mechanically-speaking? Iím currently running {V-brakes / calliper brakes, not sure which, but no hydraulics anyway**. I was thinking that I could salvage some non-indexed gear shifters and hook the brake cables up to those, my rudimentary understanding of how these things works indicate this might actually work, but Iím curious as to:

a) Why this doesnít seem to be available or been done before anywhere (actually, wikipedia mentions it under it's bicycle braking methods page, but only very, very briefly)

and

b) Whether it is even feasible.

Why do I want to do this you ask? Well, for the same reason that I want to run the brake cables through the frame, at some point; because I want this bike to look as clean and clutter-free as possible.

The problems I have envisioned so far:

1) there might be a difficulty in maintaining the same pressure on the brakes as with traditional lever brakes

2) possible friction/premature wearing of the brake cable through the twisting motion

3) I am unsure if it would even be possible to set the twist to pull enough of the cable to brake effectively

4) Where on earth would I get non-indexed grip shifters?!

5) wrist damage if braking too hard or quickly, depending on how much twist is required to get full power I guess


So been done? Possible? Opinions?

Cheers for reading guys and gals (and apologies for the verbosity and overuse of parenthesis!), any input (even ď NO, thatís crazyĒ) will be appreciated!


Cheers

Paul
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Old 10-13-10, 07:00 AM
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Grip shifters are cheap ($15 or less at a LBS- they might even give you old busted ones for free if they have them sitting around for some reason), and should be easy enough to remove the indexing on with a rasp, sandpaper, grinding wheel, etc., as they're generally made entirely of plastic. I have no idea what the pull on the cable is, but make sure your brake springs have a strong pull, so that everything returns to position.

Since this is on a 'cruiser-bike-for-looks', I think the biggest problem might be the amount of rotation in your wrist to actuate the brake. Hopefully you don't actually need to use the full range of the shifter's motion to pull the amount of cable you need for your brake.

Edit: If you're really going for looks, I suggest just going with a coaster brake. grip shifters are the epitome of cheap plastic junk, and cables are rarely attractive
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Old 10-13-10, 07:09 AM
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Should work. In theory. Shifter cables aren't as thick as brake cables, so you'd either have to use shifter cables to the brakes or check to see if you could get a brake cable to work in the shifter--there may be interference issues with the head inside the shifter, and maybe the holes the cable runs through is too small diameter for brake cable. I think if you just take out the spring mechanism that works with the molded detentes in cheap Grip Shifters, you'd get what you are looking for. Since there would not be any kind of spring return in the shifter, you'd want to make sure your spring tension at the brakes is ramped all the way up and that you have brake housing runs with no tight radii or kinks. Real issue is going to be what kind of leverage you can get out of the shifters--if there's enough cable pull to make the brakes work.
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Old 10-13-10, 07:28 AM
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Aside from putting life and limb under the control of one of the cheapest, poorest designed pieces of bicycle junk ever, there's sweaty hands and ligament/muscle injury to hands, wrists, and forearms to think about. In case of an accident that injures someone else, I'd love to be the trial lawyer going after your wallet! +1 on the coaster brake hub for the simplest set up.
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Old 10-13-10, 07:43 AM
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There's a reason no one makes such an animal. I can think of numerous reasons why. How clean it looks will only matter to you.

Look at a real brake lever. The part that carries the cable head is metal and the cable head is larger for a reason. Braking forces are much, much greater than shifting forces, and the grip shifter not only is almost entirely plastic, but won't accept the larger head. I know you mentioned using a derailleur cable but please don't. You are likely to snap the head off, or break internal shifter parts leading to brake failure just when you need them the most.

I can't really see any upside to this plan. Like someone said-if you want no cables and don't care about braking efficacy, get a coaster brake.
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Old 10-13-10, 07:48 AM
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More like Crazy Crack Pipe Dream.

Yeah I agree with Cross Creek. Grip shifters are really crappy. This isn't a good idea. You will end up messing up your wrist. I would also not feel confident using shifter cables to brake either since they are thinner than brake cables.

Last edited by 531phile; 10-13-10 at 07:51 AM.
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Old 10-13-10, 08:19 AM
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Mini bikes and motorcycles use twist grip throttles. Seems like they are built better than a shifter and might be easier to adapt to your usage. Just a thought.
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Old 10-13-10, 08:31 AM
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I hooked up a brake to a friction stem shifter once. Bad idea. It was way too easy to lock up the wheel. Plus, the friction of the shifter was so strong I had to release the brake manually. Not a good feeling. I returned the brake to the actual lever after about 5 minutes.
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Old 10-13-10, 08:38 AM
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Originally Posted by Raiden View Post
If you're really going for looks, I suggest just going with a coaster brake. grip shifters are the epitome of cheap plastic junk, and cables are rarely attractive
Originally Posted by WIKIPEDIA
<b>Advantages and disadvantages</b>
Coaster brakes also do not have sufficient heat dissipation for use on long descents. A coaster brake can only be applied when the cranks are reasonably level, limiting how quickly it can be applied.
coaster brakes are only made for rear wheels, so they have the disadvantage common to all rear brakes of skidding the wheel easily.
These are pretty much the reasons why I didn't really consider coaster brakes (I mean, I knew they existed and had thought about it but dismissed them for the above reasons).

Originally Posted by mconlonx View Post
Real issue is going to be what kind of leverage you can get out of the shifters--if there's enough cable pull to make the brakes work.
Thanks for the tech advice, I shall bear all that in mind. This is the issue that I thought would be the most pressing as well, but I think that it would have enough pull, would need to test though.
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Old 10-13-10, 08:52 AM
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The reason why multiple people on here are saying Gripshifters are junk is because many of us have seen multiple examples of them breaking just do to shifting forces... but since losing the ability to shift is not a safety issue, it's a quality problem that does not affect safety. However, if you convert the weak-as-a-kitten plastic shifters into weak-as-a-kitten plastic brake levers... well, geez - if it doesn't seem like a bad idea to you yet then I don't know what I can say to pursuade you.

Please post pictures of what is left of your bike after you get out of the hospital!
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Old 10-13-10, 09:50 AM
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It's a daft idea, consider this ..
In your hand, when the G force of braking twists the grip increasing the braking force,
in a manner over which .. you may have no control over, you may regret it.

bracing your hand against the back if a stationary grip while you are pulling a lever on the other side of the grip
works..
is there an orthopedic reason? are there prosthetic substitutes for hands involved?

Last edited by fietsbob; 10-13-10 at 02:19 PM.
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Old 10-13-10, 09:56 AM
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It is a crazy pip dream
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Old 10-13-10, 10:41 AM
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I'd go with halfpipe gripshifts or MC throttle grips that jsharr suggested if anything. Standard gripshifts are only designed to be gripped with the index finger and thumb, which ain't a lot of grip to be pulling on a brake with. I don't think I'd like the feel of twist braking personally, but I've never tried it.

I'm amazed by the utter hatred for the Gripshift. My Sram 600 8-speed shifters have been performing flawlessly since 1997.

I just scored a dumpster Trek 4000 with MRX 7-speed, which don't have as nice a feel as the 600, but seem to shift well on this poorly maintained bicycle.

I'd take mid 90s 600 or 800 over most Shimano alternatives of the era anyday.

Last edited by LesterOfPuppets; 10-13-10 at 10:45 AM.
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Old 10-13-10, 11:09 AM
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Well, the grip shift mechanisms are easy to remove the indexing. You remember that funny logo that SRAM used to use? It was in the shape of the spring that their shifters use for indexing. Remove that spring and you have a freely rotating barrel. But by the time you enlarge the claw in the spool to accept a brake cable barrel end there won't be anything left and it likely won't fit inside the outer shell anyway. There isn't a lot of room in there to work with.

Motorcycle throttle assemblies are far more along the line of what you want to go with. There's some slick looking ones for the custom bike world. And the cables they use are either bicycle brake cables or darn near to it so modifiying the spool to accept a bike brake cable would be easy. But then you run into the cable pull leverage effort and difficulty with getting a good enough grip when twisting the cable.

Looking for a nice clean look? I've got an option for you. For the rear go with a coaster brake. Nothing is cleaner than no caliper and no housings at all. And you ARE going single speed with this project I trust? That would be almost a must for this sort of bike. It avoids that clunky looking derrailleur hanging down.

For the front brake, if you mount one, get one of the reverse levers that fits into the bar end. Velo Orange has them. These levers use cable and housing runs that run along the surface of the bars. So it would be easy to either wrap the housing close to the bars using bar tape or if you don't plan on big pedalling loads where you lever the bike back and forth with your arms on the bars then you could even drill the bars for internal housing run that pops back out near the stem to run to a front caliper or even down behind the fork leg to a center hub drum brake.

Or with some care and by using a cap style stem you may even be able to have the housing run through the stem and down the steer tube of the fork. You would need to run the star nut up near the top of the tube and obviously drill the steer tube on the front just where the hole in the middle of the stem sits. The housing would need to be placed as the assembly is done and you can forget about adjustments of course. So run with external cable until you KNOW you like where the bars are sitting. Once down and through the bottom of the steer tube you would need to just secure it to the fork leg. Those are just way too fragile to be drilled for internal runs.... unless perhaps you opt for one of the thicker tube burly "jump" forks which have oversize tubes and thick walls. Then you could drill at the top inside of the leg and down near the base to bring out the housing. All of these holes would need to be "ovalized" by angling the drill after the first hole and then cleaned up with a small round file and/or Dremel to remove all the burrs that would otherwise scrape away the housing cover.

NONE of this drilling woudl be wise on a bike intended for hard riding of course. I only suggest this because you're looking at this bike as a cruiser. Even so drilling handlebars is a suggestion I give with great hesitation. If you want to do this you will need to find a very heavy duty set of bars with thick walls or the chrome steel bars so that you have a lot of reserve strength and adding a housing size hole will not greatly compromise the strength of the bars. No weight weenie stuff for something like this or you run a high risk of eating pavement.

And of course all this advice on drilling parts that should not be drilled comes with the iron clad 10-10 guarantee.... ten seconds or ten feet. While I'm pretty sure that with the right parts there is more than enough reserve strength to allow such a conversion for cruiser riding duties obviously we don't see this sort of thing so you're on your own.
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Old 10-13-10, 11:49 AM
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I've used SunTour bar-cons in the past for brake levers; they work pretty OK. I re-purposed one of those XTR 'butterlfly' remote shifters to act as an auxiliary brake, it worked fine but it took a ton of effort. If you're looking for a grip shifter to modify, there are other options besides SRAM and ShimaNO. Consider the old Sturmey grip shifters, which would look pretty sharp on a cruiser.

If you mount the caliper below the chainstay, your brake would be almost invisible. I'm not a fan of coaster brakes except as an auxiliary, but I'm a pretty heavy rider, so....
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Old 10-13-10, 12:09 PM
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Even if you find a grip shifter / motorcycle throttle that is strong enough and will accept a real brake cable (I agree with all the comments about not using a derailleur cable because it is not strong enough) then you still have the problem of ergonomics. It may be very hard to put the proper amount of power into the brake with a twist of your wrist (using a gripping motion like with normal brake levers must be much stronger) and I'd also be worried that it might not be easy to modulate the braking power (i.e., control the exact amount of braking force that is being applied).

I would therefore not have much hope that an experienced bike mechanic would be able to achieve a good result with such a project. Given that you don't even know what kind of brakes you have ("V-brakes / calliper brakes, not sure which, but no hydraulics anyway") then it doesn't sound like you know enough about what you're doing to start messing so drastically with an item that is so important to your safety. As mentioned by others, the accident that this could cause may not just involve you, but may involve innocent other people. Please forget the idea!

As for coaster brakes, my experience was that they don't really stop you, they just slow you down a little. I was amazed that in the US it is legal to sell a bike with one rear coaster brake and no other braking system (in other countries they have a minimum requirement of two brakes on a bicycle).

Last edited by Chris_W; 10-15-10 at 04:31 AM.
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Old 10-13-10, 12:55 PM
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i wouldn't ride it but grip brakes on a mountain bike doesn't sound much crazier than a grip throtle on a dirt bike.
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Old 10-13-10, 01:31 PM
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Originally Posted by luv2ride View Post
i wouldn't ride it but grip brakes on a mountain bike doesn't sound much crazier than a grip throtle on a dirt bike.
It is crazier than a grip throttle.
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Old 10-13-10, 02:17 PM
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Originally Posted by zombieThemepark View Post
1) there might be a difficulty in maintaining the same pressure on the brakes as with traditional lever brakes
I agree with all the naysayers above, but no one has addressed the shortage of cable tension that you will be stuck with. If you look at any brake lever, whether for caliper, v-brakes or cantis, they all have a large mechanical advantage. This means that you pull the lever a large distance (say 2 inches or so) with a relatively puny force and the leverage converts that to a much smaller travel of the cable (say 1/2") at a multiplied force (in this example 4 to 1). So the example above has a theoretical mechanical advantage (M.A.) of 4 meaning that the cable tension is magnified by 4times what your hand applied.

A mechanical system with no magnification of force would have a M.A. of 1.0. A grip shifter probably has a very miniscule M.A. by comparison due to the fact that the radius of the cable winding is slightly smaller than the radius of the grip where your hand applies the force, so maybe you have a M.A. of 1.5 or 2.0, depending on how large a grip you use. I doubt that this will be enough to provide sufficient force for braking, unless you are in the top percentile or two of arm strength.
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Old 10-13-10, 02:29 PM
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Originally Posted by Steve Katzman View Post
A grip shifter probably has a very miniscule M.A. by comparison due to the fact that the radius of the cable winding is slightly smaller than the radius of the grip where your hand applies the force
I'd estimate the diameter of the cable run in the (Sram Gripshift 600 and MRX) shifter to be about 1 5/8", you'd have to have some Mega grips to beat that. Maybe some pipe insulation would get you there

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Old 10-13-10, 02:47 PM
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Originally Posted by Steve Katzman View Post
I agree with all the naysayers above, but no one has addressed the shortage of cable tension that you will be stuck with. If you look at any brake lever, whether for caliper, v-brakes or cantis, they all have a large mechanical advantage. This means that you pull the lever a large distance (say 2 inches or so) with a relatively puny force and the leverage converts that to a much smaller travel of the cable (say 1/2") at a multiplied force (in this example 4 to 1). So the example above has a theoretical mechanical advantage (M.A.) of 4 meaning that the cable tension is magnified by 4times what your hand applied.

A mechanical system with no magnification of force would have a M.A. of 1.0. A grip shifter probably has a very miniscule M.A. by comparison due to the fact that the radius of the cable winding is slightly smaller than the radius of the grip where your hand applies the force, so maybe you have a M.A. of 1.5 or 2.0, depending on how large a grip you use. I doubt that this will be enough to provide sufficient force for braking, unless you are in the top percentile or two of arm strength.
Actually, the method by which the cable is pulled in most gripshift is not the head locked into a sleeve turning around another sleeve - the head is on the stationary (inner) sleeve and the cable pulling action comes from turning an eccentric ouoter sleeve, over which the cable runs. This is, IMHO, the primary design flaw with the gripshifts as the cable sliding over the sleeve causes too much friction if not perfectly clean and properly lubricated.

Anyhoo, the result is a little more MA than you would get with the head fastened tot he outer sleeve... it's still a stupid and dangerous idea, though.
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Old 10-13-10, 02:50 PM
  #22  
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Originally Posted by LesterOfPuppets View Post
I'd estimate the diameter of the cable run in the (Sram Gripshift 600 and MRX) shifter to be about 1 5/8", you'd have to have some Mega grips to beat that. Maybe some pipe insulation would get you there
I haven't taken one of those apart in years. However, that being the case you might be looking at a M.A. of close to 1.0 (or maybe even less) which only makes a stronger case for the inadequacy of using twist grips for braking.
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Old 10-13-10, 02:59 PM
  #23  
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Originally Posted by LarDasse74 View Post
Actually, the method by which the cable is pulled in most gripshift is not the head locked into a sleeve turning around another sleeve - the head is on the stationary (inner) sleeve and the cable pulling action comes from turning an eccentric ouoter sleeve, over which the cable runs.
This is not how the 1999 Sram Gripshift MRX is designed. The cable head is indeed locked into the outer sleeve. The piece with the cable run also has serrations for the indexing molded into it. The primary shifting functionality of the inner sleeve is that it houses the "clicker" - the bit that rubs against and locks into the serrations in the outer sleeve for indexing.

I'm pretty sure the 1996 Sram Gripshift 600 is similar, but I don't feel like taking it apart at the moment. The main difference I know off the top of my head is that the "clicker" is metal and not molded plastic, and very easy to lose track of upon shifter disassembly.
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Old 10-14-10, 08:47 AM
  #24  
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voila:

photo 2..JPG

photo 1..JPG

This is our crappy shop bike. That's a GripShift 3.0 Comp. Spring removed, ran a road brake cable through the shifter cable routing--you can see the round head on the shifter, just below the number 7. No drilling needed, shifter orifices accepted larger diameter brake cable. Ran these to canti brakes because that's what was on this bike.

Pull is minimal to brake contact, about one shift from 7 to just beyond 6. And it works. Kind of. Yes you get stopping power, but nowhere near what you'd need in an emergency situation at speed. Very smooth action with more than adequate spring return at the cantis to get the pads off the rim. You'd need a monster grip to lock up the front. Stopping power seems mediocre at best, bordering on perhaps dangerous.

Would definitely not recommend this to someone who bikes anywhere there are lots of steep hills. Grip shifts are actually pretty robust, so I wouldn't bet against longevity, but not even sure this will last long enough for any kind of long term test... some other tech will probably switch this back to a boring lever when they almost run into a car...

AYHSMB
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Old 10-14-10, 09:34 AM
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luv2ride
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i guess that's that
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