Home made floating brake?

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Home made floating brake?
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flag sonicsloth
Posted: Feb 5, 2009 at 14:41 Quote
A friend made a suggestion to me, and my first reaction was "don't be a moron, course it wouldn't work" but the more i've been thinking about it, the more i've been wondering, well, why wouldn't it work? maybe i'm just being an idiot, but anyway -

Making a custom floating brake arm/dope system for any full suspension bike. mount the rear brake caliper to just one of the IS frame mounts, then attach a pole of some description to the brake caliper's other mount. run the pole back and attach it to some point on the seat tube. obviously it's not quite as simple as that, but it's the theory of this idea that i'm worring about, not the details.

evedently, in comparison to an axel mounted system, this has a weak point in that it is only attached to the frame at the rear end by a single bolt, but then i think, well, it was only two bolts to begin with, and now it's secured to the seat tube as well. and if you think about the amount of force that goes through the four tiny bolts holding the weight of a child + babyseat + rack + bumpy roads with rack-mounted babyseat systems, it doesn't seem so bad.

so why wouldn't this work? Please! voice your opinion and we can see what people think.
flag jonbikes
Posted: Feb 5, 2009 at 14:50 Quote
The only reason anything home made doesn't work is due to the creators limited fabrication skill.

That is to say, if you have the resources and skills, you should be able to make anything on your own and have it work perfectly fine.
flag laurie1
Mod
Posted: Feb 5, 2009 at 15:00 Quote
It already exists. There is a company, Brake Therapy, who actually partnered with Kona to make the DOPE system. They also make floaters for pretty much any bike on the market regardless of if they have a post to mount the rod on.
flag jonbikes
Posted: Feb 5, 2009 at 15:01 Quote
There's only one problem, it's not home made. Some people enjoy the challenge of making something that already exists.
flag kovacs2121
Posted: Feb 5, 2009 at 15:01 Quote
when the suspension moves on a bike with an actual floating brake system the caliper is moving in a perfect circle as to not change its location of the pads on the rotor.

doing your home made system would move the caliper at an unknown path around the rotor. and most likely your caliper would come off the rotor at some point in your travel.

thats why floating brakes are axle mounted
flag the1nonlyj
Posted: Feb 5, 2009 at 15:03 Quote
Did i read somewhere that the dope system only works with a single pivot sus setup?
flag Shoe2190
O+
Posted: Feb 5, 2009 at 15:03 Quote
kovacs2121 wrote:
when the suspension moves on a bike with an actual floating brake system the caliper is moving in a perfect circle as to not change its location of the pads on the rotor.

doing your home made system would move the caliper at an unknown path around the rotor. and most likely your caliper would come off the rotor at some point in your travel.

thats why floating brakes are axle mounted

Exactly what he said the radius of the rotor must be what the caliper moves around
flag kovacs2121
Posted: Feb 5, 2009 at 15:05 Quote
the1nonlyj wrote:
Did i read somewhere that the dope system only works with a single pivot sus setup?

i dont believe so. but the floating brake is mainly to solve brake jack from single pivot bikes, if thats what your talking about
flag cthorpe
Posted: Feb 5, 2009 at 15:06 Quote
you would not be able to connect the caliper to one of the IS mounts and have it work. if oyu did that, then when the bike goes through its travel the caliper would rotate up and away from the rotor. the caliper would have to pivot off the axle in order to keep proper alignment with the rotor. also if you dont pivot off the axle then you won't be eliminating the brake force. you would change it in some way but you wouldn't get the desired result. keep thinking about it though. its definitely possible to build yourself. also as far as where to mount to your seat post. i believe you want the distance from your rear axle to caliper to match the distance from your main pivot to where the rod connects to the seat post. if this alignment is off then your brake will have a surging feel when you bike goes through its travel while on the brakes.
flag freeride5
Posted: Feb 5, 2009 at 15:17 Quote
ok here is the low down
not all bikes need a floating brake some are designed so you dont need one

first thing you should do is losen your suspension super loose and sit down bounce up and down on the bike and notice how it feels next grab the brake and then do the same thing depending on the bike if it needs on the feel will be alot different your fornt wheel would move foreward.

when suspension is compressed it changes the angle of the swing arm which means the caliper moves a floating brake prevents the caliper from changing position.

if your bike is a single pivot you can use some thing like the DOPE system which actually never had anything to do with kona in the first place they just gave it a fancy name for a single pivot bike the other aend of the rod just needs to be mounted against the main frame

if you have a non single pivot design like vpp fsr or dw it will be tricky the brake rod would needed to be mounted on a linkage and put in the right place to ensure when the wheel moves in toward the frame the caliper deosnt get pushed away instead of staying in a neutral position

if your not sure if your bike needs a floating brake use the program called linkage and get the file for your bike and then veiw it going through travel if any of the wheels move foreward or backward on the grid a floating brake will help
flag kovacs2121
Posted: Feb 5, 2009 at 15:19 Quote
before travel usage
photo

2968824


after travel usage
photo

2968825
flag sonicsloth
Posted: Feb 6, 2009 at 1:54 Quote
that's all been fantastic! thanks guys! that was the detail i was overlooking - the caliper rotation is not concentric to the rear axel, so i was just being a bit dense. should have thought of that. As i said, it was just the theory i was interested in - my bike doesn't actually need a dope arm. but thanks for the input!
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