Squeal with CSS rim and V brakes in front tire

[martinf]

Im think of replacing the worn rims of my tandem with CSS rims.

Some users have noticed reduced wet-weather performance with CSS rims. I haven't noticed this myself, but I am used to cantilever brakes from the 1980's and older, so may be less demanding than others.

IIRC, for the Raven and Nomad, Thorn now recommend CSS on the rear and standard rim on the front.

[garyper]

Hi Peoples,

Had my Thorn Raven Tour since 2009.  Rode a bit around Australia, then England to Croatia and me front brakes squealed all they way.  The wife's bike (same spec) has never made a squeak.  I just put on some Magura HS33 and they are fantastic, the wife and I have ordered them for all four v-brakes.

Cheers
Gary

[Slammin Sammy]

Hi Peoples,

Had my Thorn Raven Tour since 2009.  Rode a bit around Australia, then England to Croatia and me front brakes squealed all they way.  The wife's bike (same spec) has never made a squeak.  I just put on some Magura HS33 and they are fantastic, the wife and I have ordered them for all four v-brakes.

Cheers
Gary

I use the HS33s on my Nomad with CSS - no squeaks. My wife's Raven has XT brakes and no CSS. Squeaks often.

Go figure...

[Andre Jute]

I use Magura HS11 rim brakes on my big, fast Utiopia Kranich. Mine are from seven or eight years ago, when the HS11 was less powerful than the HS33, and were deliberately chosen as more suitable for avoiding face plants while still braking securely because I'm often distracted; they're fitted without any of the bracing connections across the fork between the calipers that today is everything that makes the HS33 functionally different. The rims are very wide (32mm) Exal XL. I've found that when the brakes squeal, wiping the braking surfaces on the rim and the brake blocka themselves stops the noise. I mean literally just wiping with a tissue from my pocket, not even with a damp cloth.

[JimK]

No idea why, but on my Nomad I have XTR V-brakes, blue Swiss Stop pads, and CSS rims - they've never squeaked to any significant extent!

[Matt2matt2002]

I have the Swiss Stop on my Raven.
Any idea how I should know when the rims are worn?
Bike was second hand and is 8+ years old.
Not to say the rimsare that old of course.

Fitted new pads a few months ago and now the bike stops in the rain!

[geocycle]

I have the Swiss Stop on my Raven.
Any idea how I should know when the rims are worn?
Bike was second hand and is 8+ years old.
Not to say the rimsare that old of course.

Fitted new pads a few months ago and now the bike stops in the rain!

Very hard to tell without taking the tyres off and measuring thickness with a vernier gauge. I don't think these have wear indicators?? Mine now have a smooth braking line on them but I can't detect signs they are about to give up.  Things to look out for are a concave surface and flairing. My CSS grizzlies have now done 16k miles.

[mickeg]

I suspect that CSS rims won't wear out unless somehow the CSS layer is damaged enough that the underlying softer metal can erode.  Grinding wheels in machine shops use a similar substance to the carbide that is impregnated into the rims.

I use Koolstop CSS pads on my Nomad CSS rims.  I have an XT V brake on front (do not recall the XT model number) and I have to use a lot of angle to keep them from squealing.  By angle, I mean that when I apply light pressure to the brake, initially only the trailing part of the brake block (the end towards the front) contacts the rim, more of the brake block contacts the rim as more pressure is applied to the brake.  I have them setup so that I get a slight amount of squeal, but not too much.  I do not want to make them totally silent, that much angle would likely cause premature brake block wear at only the front end of the brake.

I use Tektro CR720 cantilever brakes on the rear, I think I have a tiny amount of squeal there too, but I have been off the bike since January so I do not really remember very well how the squeal is distributed.

On the Nomad fork with the brake bosses on back instead of front of the fork, I think that design is rather poor because the axis of the bearing that the brakes rotate on is not even close to being parallel with the rim. As the brake is applied the leading edge and trailing edge of the brake blocks approach the rim at different rates.  But it is much closer to parallel when the brake bosses are on the front of the fork like on my Sherpa. 

I do not have CSS on my Sherpa, so I can't compare for "squeal" on a fork with a brake on the front of the fork since I would be comparing squeal from different brake blocks and different rim materials, thus I can't say if the brake geometry is in part the reason for the squeal.  I did have a suspension fork on my Nomad a year ago and that has the brakes on the front, but I can't remember if that design lessened the amount of squeal.  I was more focused on getting my suspension preload and rebound set and was not thinking too much about brake squeal.

Just a side note - on my LHT, I had an average of about 2,400 feet (~730m) of elevation gain and loss every day last summer for a month of loaded touring with a bike that weighed (with camping gear) about 100 pounds (~45kg) in addition to my weight of about 180 pounds (~80kg).  I did not start the trip with new brake blocks, but I was surprised how much wear I got on them during the trip.  I had to replace both front and rear brake blocks after the trip, see photo.  I do not have CSS on that bike.

[Andre Jute]

Just a side note - on my LHT, I had an average of about 2,400 feet (~730m) of elevation gain and loss every day last summer for a month of loaded touring with a bike that weighed (with camping gear) about 100 pounds (~45kg) in addition to my weight of about 180 pounds (~80kg).  I did not start the trip with new brake blocks, but I was surprised how much wear I got on them during the trip.  I had to replace both front and rear brake blocks after the trip, see photo. 

George's experience sounds like a touring rule in the making:

Brake wear is clearly a function of the mass to be slowed, the velocity by which it is to be slowed, and the friction between the braking surfaces (not all brake blocks are equally good, not all rim brake tracks offer equal friction). We can leave the road surface out here as a random factor, though we shouldn't forget that, in the final analysis, the rate of retardation is strictly limited by the friction between the road and the tyre, so that many more factors could be involved in the lesser, fractional elements of brake block and rim flange wear.

A reliable substitute for velocity retarded, which is difficult to work measure in the wild (and is anyway generally approximated by accumulated negative changes in velocity), is the elevation achieved over a period: the cyclist who goes up a hill generally goes down the other side or returns downhill on the same road.

So I suggest as a first approximation for tarmac touring that brake block wear, and eventually rim wear, amounts to:

Bw = 2(M * E * k(f1))

Rw = (Bw * k(f2))^-x

where
Bw is brake block wear
M is the mass of bike, gear and riders
E is elevation
k(f1) is a constant to allow for wear characteristics of different brake blocks
Rw is rim wear
k(f2) is a constant to allow for the wear characteristics of different rims, with CSS as 1 and all others as fractions of 1
x is a factor to allow for the rim wearing slower than the brake blocks by a multiple which we hope is large
and
the answer is in distance,
which is what accounts for the doubling, on the assumption that every inch of elevation will on average become an inch of descent.

The Jute Rule of Touring Bike Brake Longevity is a corollary of Andre's Neddy Rule for Budding Tricyclists: "If you ain't got brakes, you crash at the bottom of the hill, so it is better to crash near the top where you'll still be going slowly."

[mickeg]

There are other factors for braking and brake wear on a tour. 
- You start at the top of a hill, probably rolling rather slowly, at the bottom you are much faster and carrying extra kinetic energy.  That extra kinetic energy is brake wear that did not happen.  More hills with less elevation will result in less brake wear than one huge hill.
- A long shallow downhill can result in a lot less brake wear than a steep hill of equivalent elevation loss, the aerodynamic drag and tire friction on the shallow hill is spread over a greater distance.  The attached is an elevation profile of my last day on a tour about six years ago.  Almost the entire day was down hill.  That day was almost all on gravel which increases rolling friction.  Although the graph makes the hill look steep, the grade was quite shallow.  The sum of rolling friction and aerodynamic drag was greater than energy from loss of elevation.  Thus, for most of that downhill I was pedaling in my two highest gears, not braking.

Thus, I would not propose that brake wear is linear with elevation loss.

[Matt2matt2002]

In the last few weeks my back brake has started squelling.
CSS rims.
I'll investigate and report back.
2_000 Km from new ( pads) not rims.
Strange.
Matt

[mickeg]

I have CSS on front and rear.  Front uses an XT V brake, rear is a Tekro CR720 cantilever.  Koolstop CSS pads on both brakes.

I have noticed that my brake pads were wearing more on the front of the pad than the rear, that of course is how I installed them with sufficient toe in to minimize squeal.

At the cost of CSS pads, I wanted to distribute the wear better.  In a few weeks I will be doing a couple hundred miles of single track touring with my Nomad, elevation gain (and loss) is expected to be about 24,000 feet.  So I figured if I am in the middle of a wilderness where only one other person would have to listen to my brake squeal, that would be a perfect place to suffer loud brake squeal while I better distribute the brake pad wear on my expensive pads.

Thus, I adjusted the pads to use "negative" toe in, the rearmost part of the pad now contacts the rims first.  I was expecting my brakes to squeal very badly, but I was really surprised that I just barely get a slight squeal on one brake and no squeal on the other.

I find this to be a pleasant surprise, although quite odd.

[il padrone]

I've been running Andra CSS rims with Swissstop Blue pads. They are now up to 25,000kms, and I replaced the pads about 1-2,000 kms back. The pads were always run pretty flat-faced to the rim - I think the front has a bit of toe-in, perhaps a bit too much. They brakes have never squealed at any time, just the trademark grating sound of the CSS surface.

I love these brakes and rims...... except for the occasional wet weather slowness to work. But that is generally a pretty rare occurrence. I really got my money's worth out of the first brake pads, and I fully expect the rims to last until about 40,000kms