Rear Disc Brake leverage(?)

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simonn
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Rear Disc Brake leverage(?)

Postby simonn » Mon Oct 21, 2013 12:55 pm

My Boardman CX has Avid BB5 disc brakes with full length outer brake cables from Shimano 105 5700 STIs. I removed the interrupter brakes (those are the ones on the tops) because I never used them.

The problem is the rear brake is a bit weak from the hoods. Takes longer to stop than a rear rim brake on any of my roadies. It is fine from the drops where I can get maximum leverage.

STIs are correctly positioned according the manual. Front brake is fine.

Any ideas for increasing the leverage from the hoods?

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MattyK
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Re: Rear Disc Brake leverage(?)

Postby MattyK » Mon Oct 21, 2013 1:28 pm

Leverage would refer to how far the lever moves (once the pads are engaged), not how effective the braking is. If the lever moves the appropriate amount, and isn't soft (pulling to the bars) when the pads engage, then the issue is elsewhere.

Are the pads bedded in? This took a while when I put a BB7 on my bike, and the rear would presumably take longer.
Is the inboard pad properly adjusted?
Is the cable tensioning (outer pad position) properly adjusted? (Do you hvae a barrel adjuster anymore after removing the interrupter levers?
What size rotors does it run?
How much are you willing to spend?

eeksll
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Re: Rear Disc Brake leverage(?)

Postby eeksll » Mon Oct 21, 2013 1:33 pm

a bigger disc rotor at the back if it will fit?

its not possible to get more levarge from the hoods as the anchor of your hands is on the hoods so i don't think any amount of moving on the bars will change it.

Campag and sram i hear have a higher pivot point, so that could be an option.

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drubie
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Re: Rear Disc Brake leverage(?)

Postby drubie » Mon Oct 21, 2013 3:07 pm

Double check that the disk is centred properly in the rear caliper so that the disk doesn't deflect too far under braking. It makes for soft, ineffective brakes if not adjusted properly.

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Mulger bill
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Re: Rear Disc Brake leverage(?)

Postby Mulger bill » Mon Oct 21, 2013 7:43 pm

drubie wrote:Double check that the disk is centred properly in the rear caliper so that the disk doesn't deflect too far under braking. It makes for soft, ineffective brakes if not adjusted properly.

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simonn
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Re: Rear Disc Brake leverage(?)

Postby simonn » Tue Oct 22, 2013 9:43 am

Thanks everyone. I guess it was a mixture of leverage - works better when on the drops than hoods - and bedding in - works better now I have used it to come to a stop a few times while descending.

It is better than it was, not quite as good as I'd like, but it stops me.

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baabaa
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Re: Rear Disc Brake leverage(?)

Postby baabaa » Tue Oct 22, 2013 7:36 pm

I would suggest a small dab of vaseline on each rear brake pad of the other bikes.
Your rear bb5s stopping power should then feel much better.
Oh and did you use new full length housing or just butt up the spot from the crosstop levers? (some how)

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visrealm
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Re: Rear Disc Brake leverage(?)

Postby visrealm » Tue Oct 22, 2013 7:43 pm

Do you use the rear brake as your primary brake?

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simonn
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Re: Rear Disc Brake leverage(?)

Postby simonn » Tue Oct 22, 2013 8:05 pm

baabaa wrote:I would suggest a small dab of vaseline on each rear brake pad of the other bikes.
Your rear bb5s stopping power should then feel much better.


Really...? I never heard of that before.

Oh and did you use new full length housing or just butt up the spot from the crosstop levers? (some how)


Nope. Full length housing from factory. No way of changing it - short of brazing on bits and bobs.

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simonn
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Re: Rear Disc Brake leverage(?)

Postby simonn » Tue Oct 22, 2013 8:06 pm

visrealm wrote:Do you use the rear brake as your primary brake?


No. Hardly ever use it, but that's part of the reason I want to make sure it works properly would be a bit of a bummer if the front failed only to find out the rear isn's working to well either :).

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visrealm
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Re: Rear Disc Brake leverage(?)

Postby visrealm » Tue Oct 22, 2013 8:29 pm

Heh fair point.

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