Mechanical advice - Fulcrum Racing 1 Rim Wear

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paul
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Postby paul » 28 Jul 2010, 10:08

The rims on my Fulcrum Racing 1 wheels are showing wear, with the braking surface having a concave profile.
There does not seem to be any wear indicators, how how to know when to replace?

Also, are replacement rims available/affordable, or do I need a whole new wheel?

Paul

christian
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Postby christian » 28 Jul 2010, 10:59

I just did a quick search and you can buy the rims. It should be a lot cheaper then a new wheel as they have some pretty expensive spokes in them don't they. As for how worn they can be, that depends on the thickness of the rim. If they are noticeably concave then I'd say its time to replace them.

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fenn_paddler
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Postby fenn_paddler » 28 Jul 2010, 11:09

I've replaced rims / wheels in the past when the pads have worn through the rim at some point. You can tell when you're at that point, becuase the brakes start 'grabbing' when they're applied.

Not to hijack the thread, but I've noticed much higher rim wear on the fixie versus standard roadie. Why would that be? I hate to see excessive pad or rim wear because it represents huge amounts of wasted energy.

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weiyun
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Postby weiyun » 28 Jul 2010, 12:09

As much the rims are available, replacement for factory wheels would not come cheaply with labour added. So check costs before the jump. Otherwise new R1s cost less than $1k mail order. Further, some people advocate replacement of Alu spokes on these rebuilds and that'd add cost too.

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Toff
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Postby Toff » 29 Jul 2010, 11:52

fenn_paddler wrote:Not to hijack the thread, but I've noticed much higher rim wear on the fixie versus standard roadie. Why would that be? I hate to see excessive pad or rim wear because it represents huge amounts of wasted energy.

I have ripped through a pair of pads on my fixed gear bike in just a few months. Part of this has been because I only use the front brake on my fixie, but even road bikes do 90% of their braking on the front, so this does not explain what's goiong on.

I think the answer lies with the forces going through the drivetrain. On a freewheeled bike, when you brake you have to overcome the bike's inertia, but you are not applying force to the pedals. When you brake on a fixed gear bike you have to overcome inertia of the bike, plus the angular momentum of your turning legs. The forces that are needed to overcome this additional momentum are greater and this leads to faster brake wear. It would be similar to trying to apply brakes in a car, whilst continuing to rev the engine.

Another way to look at it is this... On a freewheeled bike, we use our muscles to stop our legs turning, not the brakes. This is easy to do, because the legs no longer have any external load on them when you decide to turn them slower or stop them. Riders who are new to fixed gear bikes soon learn to not stop pedalling, as stopping pedalling results in your bum lifting off the saddle, or the back wheel lifting off the ground, or some other manifestation of the rotational load that has to be dissipated. (Technically it's called a "moment of inertia", and it is a body's tendendcy to continue to rotate once set in motion.) Once we have been conditioned to not stop our legs turning, we continue to turn our legs even when the brakes are applied, to ensure a nice smooth deceleration, not a bumpy violent one.

Very skilled riders may be able to not only pedal smoothly, but may also be able to apply a smooth deceleration of their legs' angular velocity throughout the whole pedal stroke as as they apply the brakes. In doing so, they may be able to have similar (or possibly superior) brake wear than a freewheel bike rider. However, it really is an un-necessary skill. Also, a rider doing it would need to remember to do it every time he applied the brakes - which is unlikely. It is also not recommended to try to slow your leg speed down by back-pedalling, as the experts will tell you that this can damage your ability to generate high leg speed due to eccentric muscle exercise damage. Track racers are told to never pedal backwards for this reason.

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Karzie
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Postby Karzie » 29 Jul 2010, 14:05

I also brake sometime on a fixie when I wouldn't on a freewheel, just because my legs are going around uncomfortably fast. As I'm a bit of a Woos, this probably leads to ridiculous amounts of wear!

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weiyun
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Postby weiyun » 29 Jul 2010, 14:30

Karzie wrote:I also brake sometime on a fixie... just because my legs are going around uncomfortably fast. As I'm a bit of a Woos, this probably leads to ridiculous amounts of wear!

Maybe someone should invent a mechanism that permits the wheel to spin without rotating the cranks to avoid these problems.... Call it "freewheeling" perhaps? :!:

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Toff
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Postby Toff » 29 Jul 2010, 15:12

Maybe someone should invent a game where you go on forums and try to bait the people posting legitimate comments into making defensive, irate or angry responses. Call it "trolling" perhaps?

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fenn_paddler
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Postby fenn_paddler » 29 Jul 2010, 15:13

Nice explanation Toff. I'm glad it's not just me wearing brake pads out...

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weiyun
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Postby weiyun » 29 Jul 2010, 17:28

Toff wrote:Maybe someone should invent a game where you go on forums and try to bait the people posting legitimate comments into making defensive, irate or angry responses. Call it "trolling" perhaps?

That wasn't trolling. Your post above was a real troll.

Legitimate technical comments don't equate with the gospel. Questioning and subsequent discussion is but a function of a forum.

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Karzie
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Postby Karzie » 29 Jul 2010, 18:59

weiyun wrote:
Toff wrote:Maybe someone should invent a game where you go on forums and try to bait the people posting legitimate comments into making defensive, irate or angry responses. Call it "trolling" perhaps?

That wasn't trolling. Your post above was a real troll.

Legitimate technical comments don't equate with the gospel. Questioning and subsequent discussion is but a function of a forum.


Guys! Peace and Love!

But Weyun, you did have to edit my comment in order to be sarcastic. That's ok. Sometimes you have to be cruel to be funny!

I was just commenting on why fixies brakes wear out quicker. I brake more like this esp when I have my jeans on or there are undulations of uncomfortability or I just want to look more cool.

Maybe other people do this too (not that i'm pointing any fingers at all the REAL cyclists in the club!).

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Stuart
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Postby Stuart » 30 Jul 2010, 09:45

[mod] OK guys settle and back on topic please [/mod]

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williamd
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Postby williamd » 30 Jul 2010, 19:30

Getting off the trolls
For anyone with campag brakes like Toff I have some new campag brake cartridges going cheap.


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