Paul Racer Brake Noise/Vibration

[Ben Mihovk]

Good morning,

I just got a new set of Racer (regular) brakes for my sidepull Hillborne. Everything's set up, the brakes are grabbing/stopping, but I'm getting the most horrific noises from the pads on the front brakes. I'm using the Kool Stop Thinlines that Paul sends with the brakes. I set them up following the instructions from Paul initially (no toe-in), and the brakes squealed on the first test ride. So I toed them in and now I'm getting this awful vibration when the pads touch the rims that gets louder/more intense with speed. The vibration can be felt in the saddle...all through the frame. Truly harrowing stuff here. When I full pull the brake levers, the vibration kind of goes away but I get a light squeal (even with brakes toed in). 

I've never set up centerpull brakes or any brakes with a straddle wire/hanger. I can't see how the problem could be from anything but how the pads are hitting. I've double checked to see that the unit is centered when I tighten it. The one goofy thing I'm noticing is that the right arm of the brake seems lower because I have the pad set higher in the arm than on the left side...but I've taken the pads off completely and recentered the brake unit and I'm getting the same results.

I've read a little about how big frames (this is a 62cm Sam) can have the vibrations because of the length of cable and how tension varies through the pull (or something like that). I've also read that this kind issue could be from cheap/flimsly brakes...but I would hope that Paul brakes would be above suspicion here. I've also heard that if something is loose on the brake assembly, the vibrations can happen.

However...I'm convinced it's in how I have the pads set...I don't get vibrations when the pads are not toed-in...toeing in almost seems to bring about the vibrations. 

Any ideas anyone has would be very helpful. I'm at the end of my rope and considering removing the Pauls and going back to the squisy and not very good Tektros Riv put on it originally.

Thanks!

Ben in Omaha

[Jay Lonner]

This is a common complaint with headset-mounted cable hangers. Changing to a fork-mounted hanger usually alleviates the problem. Shovel Research just released a nice one: https://shovelresearch.com/fork-mounted-brake-cable-hanger

Jay Lonner

Bellingham, WA

Sent from my Atari 400

On Sep 8, 2023, at 5:54 AM, Ben Mihovk <bjmi...@gmail.com> wrote:

Good morning,

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[Ben Mihovk]

Good to know...but if my brake is mounted on the fork, I'm not sure where I'd mount a fork-mounted cable hanger. 

Ben

[JohnS]

Hello Ben, maybe it would help the group if you were to post a picture or two of your current set up.

Thanks,

JohnS

[J G]

I am a big fan of the Racer brakes.  Would hope that you would not need to dump.  Set mine up many years ago, but seem to remember them not being toed in.

I would recommend going back to no toe in and first see if the squealing ceases once bedded in, before considering other changes.

As far as the shudder, big bikes with 1" tubes and a canti hanger above the top of the headset, is a candidate for said shudder so a plus that you are not seeing that when not toed.

[Ben Mihovk]

For sure! I'll see if I can find time when I get home from work. 

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[Patrick Moore]

Are the rims and pads clean? 

Are the rims new? I've found that a hundred miles or so of not-too-clean riding surfaces can do a lot to "match" pads to rims.

I had horrible squeal and front judder with Tektro CR 720s on my then-new 2020 Matthews (26" wheels on largish frame, so very long steerer). I toed the salmon pads in to a comical degree and both stopped or -- judder -- reduced to a barely noticeable hint under medium braking pressures. The braking effectiveness remained much the same; that is to say, mediocre -- but: when I replaced the Tektros with Pauls the braking effectiveness remained the same even through the squeal and judder went away with the same pads normally toed in.

OTOH again, after several hundreds of miles on the pads the "force" of the brakes is now noticeably better and there is no more squeal or judder than at first. (There is just a faint hint of judder in front under medium braking, but it does not bother me who am excessively obsessive about such things. I can't drill the fork crown because of the deep front fender mounting boss under the crown.)

If I were in your place I'd increase toe-in and ride the bike on some dusty roads and re-evaluate the situation after 100 miles or so.

[J G]

Agree with Patrick that whatever change you make, give it a 100 miles.

Only disagree with the idea to toe in more.  Centerpull brakes work best with no toe in, in my experience.  

I have 2 bikes with Paul Racers, with one center mount and one post mount.  No toe in for either and no squeal or shudder.  Just some of the best braking power and modulation of any bikes I have.

Here is a good link that discusses center pull brakes and toe in:

https://www.renehersecycles.com/a-better-way-to-adjust-toe-in/

Here is a key excerpt from page and the theory stands IMHO for both center and post mount, even though the statement specifically alludes to post mount:

"Centerpull brakes attach close to the fork crown, so the fork blades don’t twist significantly. This is why centerpull brakes offer such consistent brake modulation. It’s also the reason they don’t require toe-in. Centerpull brakes work best when the pads are parallel to the rim.

When we introduced the Compass centerpull brakes, the toe-in was not adjustable. In our testing of prototypes, we found that the brakes might squeal for the first few rides, but they became quiet as the pads wore until they were parallel to the rim. Most of our customers have had similar experiences."

[Ben Mihovk]

Thanks for all the feedback ideas.

1. Old rims, not new. 

2. I got home from work and got to work on adjusting the springs on the breaks and making sure each arm felt as stiff as the other. I also re-centered the brake once again.

3. Cleaned rims and pads again with isopropyl alcohol. 

4. I reset the pads once again, triple checking position, making sure they contact the rim at the same time, etc... 

With pads mounted flush...no shudder but some squeal. Not terrible.

With pads toed in, no shudder on light braking. Squealing is absent at the beginning of braking but comes in eventually with a little bit of shudder. My next move is to reset the pads with minimal toe in.

I also e-mailed Kool Stop and a very nice guy named Tim e-mailed back and suggested doing the toe-in with a dime in the rear of the pad first and trying it out. Then move up to a nickel if that's not enough toe in. I have them toed in a lot at the moment so I'm hopeful that backing it off with improve it. The braking is AMAZING with the pads parallel to the rim, so maybe I'll just do a long dusty ride tomorrow out in a remote area so I don't bother anyone with my squealing. 

Finally, I e-mailed Will at Riv and just asked if there was an issue with big frames and Paul Racers...he actually had these on his Sam and said he didn't have a problem, so there should be a solution to getting these brakes to work. 

I feel a lot better now than I did this morning, for sure. Thanks again for all the help!

Here's how I have it set up...I know I cut the brake cable way too short...this is my first crack at this kind of set up.

On Friday, September 8, 2023 at 1:34:07 PM UTC-5 Patrick Moore wrote: