Front brake "pulses"

[Baka Dasai]

My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
wheel where the brake grabs. It's not a big problem under light braking, but under heavy braking I
always get the feeling that I'm going to go over the handlebars.

I've visually checked the rim, but I can't see any deformation. I've also cleaned the rim
thoroughly.

Any ideas/solutions? Or is time to get a new rim?
--
"Naturally, the common people don't want war. But, after all, it is the leaders of a country who
determine policy, and it is always a simple matter to drag the people along. All you have to do is
tell them they are being attacked, and denounce the peacemakers for lack of patriotism and exposing
the country to danger. It works the same in any country."
- Hermann Goering

 

[James Connell]

Baka Dasai wrote:
> My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
> wheel where the brake grabs. It's not a big problem under light braking, but under heavy braking I
> always get the feeling that I'm going to go over the handlebars.
>
> I've visually checked the rim, but I can't see any deformation. I've also cleaned the rim
> thoroughly.
>
> Any ideas/solutions? Or is time to get a new rim?

deglase the pads (not likely the problem), clean the rim with a degreaser. if this doesn't help look
harder rim damage.

 

[Jeff]

Is the brake fastened tight to the fork? Loose brake installation can cause pulsing.

"Baka Dasai" <[email protected]> wrote
> My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
> wheel where the brake grabs.

 

[Mike S.]

"Baka Dasai" <[email protected]> wrote in message
news:[email protected]...
> My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
> wheel where the brake grabs. It's not a big problem under light braking, but under heavy braking I
> always get the feeling that I'm going to go over the handlebars.
>
> I've visually checked the rim, but I can't see any deformation. I've also cleaned the rim
> thoroughly.
>
> Any ideas/solutions? Or is time to get a new rim?
> --

What kind of rim? Is it one with a machined sidewall, or the old pinned and glued joint?

Mike

> "Naturally, the common people don't want war. But, after all, it is the leaders of a country who
> determine policy, and it is always a simple
matter
> to drag the people along. All you have to do is tell them they are being attacked, and denounce
> the peacemakers for lack of patriotism and exposing the country to danger. It works the same in
> any country."
> - Hermann Goering

 

[Baka Dasai]

On Fri, 2 May 2003 23:23:00 -0700, Mike S. said (and I quote):
>
> "Baka Dasai" <[email protected]> wrote in message
> news:[email protected]...
>> My front brake has a very annoying "pulse". There seems to be one point in every revolution of
>> the wheel where the brake grabs. It's not a big problem under light braking, but under heavy
>> braking I always get the feeling that I'm going to go over the handlebars.
>>
>> I've visually checked the rim, but I can't see any deformation. I've also cleaned the rim
>> thoroughly.
>>
>> Any ideas/solutions? Or is time to get a new rim?
>
> What kind of rim? Is it one with a machined sidewall, or the old pinned and glued joint?

I don't know enough about rims to answer with any confidence. It's a Mavic ceramic rim, probably
less than 10 years old. (I bought the bike second- hand from a friend)

And I checked the tightness of the bolts that connect the (V-) brakes. They were fine.
--
"Naturally, the common people don't want war. But, after all, it is the leaders of a country who
determine policy, and it is always a simple matter to drag the people along. All you have to do is
tell them they are being attacked, and denounce the peacemakers for lack of patriotism and exposing
the country to danger. It works the same in any country."
- Hermann Goering

 

[David Kunz]

Baka Dasai wrote:
> My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
> wheel where the brake grabs. It's not a big problem under light braking, but under heavy braking I
> always get the feeling that I'm going to go over the handlebars.
>
> I've visually checked the rim, but I can't see any deformation. I've also cleaned the rim
> thoroughly.
>
> Any ideas/solutions? Or is time to get a new rim?

Several things come to mind. Hold the brake lever slightly and turn the wheel to see if you can find
where's it's slipping or where it's grabbing. This could be oil or contamination on the rim, it
could be a rim that's splitting (both sides will bow out), it could be a rim that's out of true or
been hit. If you can't find it that way, try turning the rim and looking at the gap between the rim
and the pads to see if there's a place where it gets suddenly small -- if you find that, the rim
needs to be trued or replaced. If you can't find anything, I'd clean the rim with something like
comet (a highly abrasive strong detergent) or maybe a brillo pad and see if I can make it go away
. Use something that will break a glaze or wax and disolve grease. Do that pads too.

David

 

[David L. Johnso]

On Sat, 03 May 2003 04:41:05 +0000, Baka Dasai wrote:

> My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
> wheel where the brake grabs. It's not a big problem under light braking, but under heavy braking I
> always get the feeling that I'm going to go over the handlebars.

Typically this happens at the joint, opposite the valve.

> Any ideas/solutions? Or is time to get a new rim?

If it bothers you, yes.

--

David L. Johnson

__o | It is a scientifically proven fact that a mid life crisis can _`\(,_ | only be cured by
something racy and Italian. Bianchis and (_)/ (_) | Colnagos are a lot cheaper than Maserattis
and Ferraris. -- Glenn Davies

 

[Chris Zacho "Th]

Look for any dents or bumps in the rim Have you hit any large potholes or bumps in the road
recently?. Is the rim true? Spin the wheel and watch carefully where it passes the brake blocks.
Are there any places where it seems to jump outwards or inwards from the hub (out of roundness)?
This is a lot easier to see on a truing stand. If you don't have one, find a friend who does or try
at your LBS.

If this is the case, true the wheel, if possible

Having eliminated that possibility, look at the spot where the rim is joined together. i.e., where
the ends meet. Is the joint smooth? if not, try a little sandpaper to smooth it.

If the ends have been welded together, you're probably out of luck. Rims that have been weldee
together are usually of lower quality grade meaning not much attention is given to the smoothness of
the joint, or the roundness of the rim at this point.

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": http://www.geocities.com/czcorner

 

[Barbara Larrain]

I'm surprised no one mentioned this. I recently had something similar when I switched from my Rolf
Wheels to my Zipp wheels which "come out farther" than the Rolf. I have Ultegra brakes with the
cartridge pad & when they wear down to below a certain point the small little screw (not the one
that holds the cartridge in place) at the bottom of the pad holder & isn't removable, will grab on
the rim & can cause the pulse sensation. It's desigend to let you know it's time to replace the pad.

The only other time I have experienced something similar was when I had an out of tru wheel.

Barbara L

"Baka Dasai" <[email protected]> wrote in message
news:[email protected]...
> My front brake has a very annoying "pulse". There seems to be one point in every revolution of the
> wheel where the brake grabs. It's not a big problem under light braking, but under heavy braking I
> always get the feeling that I'm going to go over the handlebars.
>
> I've visually checked the rim, but I can't see any deformation. I've also cleaned the rim
> thoroughly.
>
> Any ideas/solutions? Or is time to get a new rim?
> --
> "Naturally, the common people don't want war. But, after all, it is the leaders of a country who
> determine policy, and it is always a simple
matter
> to drag the people along. All you have to do is tell them they are being attacked, and denounce
> the peacemakers for lack of patriotism and exposing the country to danger. It works the same in
> any country."
> - Hermann Goering

 

[Rudge]

A LOOSE HEADSET can exagerate the effect of any small differences of thickness or ridges on the rim
(usually at the rim joint).

I had this problem myself.