Relationship between wear on bike rims and braking performance

[David Dowding]

I am a Mechanical engineering student at the University of the West of England, for my final year
project I am investigating how braking performance of a bicycle is affected by the amount of wear on
the rim. i have set up a test rig with a wheel turned by a motor (weighted with lead to get
momentum) and will be measuring the time taken to stop the wheel when a brake is applied with a
known force. If anyone has any comments on this subject they would be very much apprecieated, or if
anyone knows of any other research into this subject it would be very useful. Thanks Dave

 

[Zog The Undenia]

David Dowding wrote:

> I am a Mechanical engineering student at the University of the West of England, for my final year
> project I am investigating how braking performance of a bicycle is affected by the amount of wear
> on the rim. i have set up a test rig with a wheel turned by a motor (weighted with lead to get
> momentum) and will be measuring the time taken to stop the wheel when a brake is applied with a
> known force. If anyone has any comments on this subject they would be very much apprecieated, or
> if anyone knows of any other research into this subject it would be very useful.

The main factor will be whether the rim is anodised or not. You get much better wet braking when
it's all been ground off.

Oh yeah, and don't use a chromed steel rim - they last a few years longer than the age of
the Universe.

 

[Werehatrack]

On 22 Jan 2004 03:44:12 -0800, [email protected] (David Dowding)
may have said:

>I am a Mechanical engineering student at the University of the West of England, for my final year
>project I am investigating how braking performance of a bicycle is affected by the amount of wear
>on the rim. i have set up a test rig with a wheel turned by a motor (weighted with lead to get
>momentum) and will be measuring the time taken to stop the wheel when a brake is applied with a
>known force. If anyone has any comments on this subject they would be very much apprecieated, or if
>anyone knows of any other research into this subject it would be very useful.

Plain aluminum rim: Brake effectiveness and rim wear rates will be primarily a function of the pad
material. In particular, some pads are known to become contaminated with aluminum particles faster
and more heavily than others, which then increases the wear rate of the rim.

Anodized aluminum rim: Effectiveness will increase when the anodizing wears through. The rate at
which this will occur is probably dependent upon the amount of environmental abrasive contamination
present in the pads, which in a lab setting may be insufficient to wear through the anodizing in a
useful period of time.

Chromed steel rim: What wear? (I have rims of this type on one bike that is about thirty years old,
and they show no wear.)

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[Dion Dock]

What about the wear of the brake pads? How are you going to keep that from changing? Is the wear on
the rim more or less important than the wear on the pads?

-Dion

"David Dowding" <[email protected]> wrote in message
news:[email protected]...
> I am a Mechanical engineering student at the University of the West of England, for my final year
> project I am investigating how braking performance of a bicycle is affected by the amount of wear
> on the rim. i have set up a test rig with a wheel turned by a motor (weighted with lead to get
> momentum) and will be measuring the time taken to stop the wheel when a brake is applied with a
> known force. If anyone has any comments on this subject they would be very much apprecieated, or
> if anyone knows of any other research into this subject it would be very useful. Thanks Dave

 

[Bill Putnam]

Werehatrack <[email protected]> wrote in message news:<[email protected]>......
> Chromed steel rim: What wear? (I have rims of this type on one bike that is about thirty years
> old, and they show no wear.)

This is a bit off topic, but if a bike with steel rims is used in the winter in areas where salt is
applied to the roads, it will rust given enough use and time. A friend of mine wore out his original
Schwinn steel rim after about 25 years of daily year round use (he commuted by bicycle in Madison WI
for his entire working life, he's retired now). The wall thickness got thin enough that the pressure
from the tire bent the walls outward and the tire would no longer stay on the rim. The original
sturmey archer hub was still working fine with the only maintenance being regular application of oil
and the occasional control cable and indicator rod.

Getting back to the original poster's questions, I am very curious how consistent his data will be.
I would expect that contamination of the brake pad material from the aluminum on the rim could
result in problems. Also, how will rim wear be measured, and how will a rim be worn? Does he have
several identical rims from the same manufacturer in new and various states of used condition? I
would submit that the experiment would be more useful to compare the performance of different brake
pad materials using the same rim, though each pad would need to be bedded into the rim to get
reasonably consistent results.

Bill Putnam

 

[David Dowding]

"Dion Dock" <[email protected]> wrote in message news:<[email protected]>...
> What about the wear of the brake pads? How are you going to keep that from changing? Is the wear
> on the rim more or less important than the wear on the pads?
The test is going to look at several wheels worn varying amounts in normal use and a new wheel so
the wearing of the rim will already have been done thus only small amounts of braking will have to
be done so little wear of the brake pads should occur in that time

Bill Putnam ([email protected])wrote
> I would expect that contamination of the
brake pad material from the aluminum on the rim could result in problems. Also, how will rim wear be
measured, and how will a rim be worn? Does he have several identical rims from the same manufacturer
in new and various states of used condition? I would submit that the experiment would be more useful
to compare the performance of different brake pad materials using the same rim, though each pad
would need to be bedded into the rim to get reasonably consistent results.

I am going to measure the thickness of the rim material to see how much it has been worn and study
the material afterwards to see how the material has worn.

 

[Jobst Brandt]

David Dowding writes:

> I am a Mechanical engineering student at the University of the West of England, for my final year
> project I am investigating how braking performance of a bicycle is affected by the amount of wear
> on the rim. I have set up a test rig with a wheel turned by a motor (weighted with lead to get
> momentum) and will be measuring the time taken to stop the wheel when a brake is applied with a
> known force. If anyone has any comments on this subject they would be very much apprecieated, or
> if anyone knows of any other research into this subject it would be very useful.

See test route descriptions:

http://tinyurl.com/adls

This subject has been discussed in wreck.bike often and as I have mentioned, I have often ridden my
annual tour of the Alps with practically no brake pad and rim wear when the weather is dry and once
used up a practically new set of MA-2 rims on a typical 2200 mile tour on which every major descent
was with rain. I still have a cross section of the rims that were worn to less than 0.5mm thickness
in the center of the brake track. This occurred without metal shavings building up on my Kool-Stop
Salmon-red brake pads.

Therefore, I don't see how you are going to define your test. We have seen the extremes. What are
you going to add to that and what will it mean? Rim wear does not affect brake performance but it
will cause rim failure if allowed to progress beyond reasonable limits. Brake pad contamination by
aluminum shavings degrades braking but that can be avoided if suitable brake pads are used. My
experience is that Kool-Stop Salmon-red pads are essentially immune to that problem.

Jobst Brandt [email protected]