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Discussion Starter · #1 ·
Morning,

First, I've been lurking he a while. This is my first post. I must say, thanks to everyone for all the informative and helpful posts. I've tweaked my bike and bought many items based on reviews and discussions here w/ + results. This is a great community. Thank you.

Second, my question. I just changed my brake pads, readjusted the distance from the wheels, and, although the rear wheel does not rub when the bike is in the stand, it rubs under load, esp up hill. Thus, I've spread the gap a little more to compensate.

I ride an aluminium 2002 Giant TCR 1 w/ Ksyrium SSC SL wheels. I'm guessing the frame is flexing. I bought the bike used 3 yrs ago. Is this flex normal? is this a big deal? am I losing lots o' energy b/c of this flex?

Any insight would be appreciated.

-MooseDawg
 

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Flexibility

MooseDawg said:
I ride an aluminium 2002 Giant TCR 1 w/ Ksyrium SSC SL wheels. I'm guessing the frame is flexing. I bought the bike used 3 yrs ago. Is this flex normal? is this a big deal? am I losing lots o' energy b/c of this flex?
Actually, Ksyrium wheels are pretty flexible, and brake pad rub is typically due to wheel flex rather than frame flex. Your experience is common, though not universal by any means. Lots of people like to set their brake pads very close to the rim because it makes the brakes seem more responsive, but IME it makes your brakes harder to modulate.

You will find those who will tell you that this flex is a big energy waster. There are others who will ask: "Where does that wasted energy go?" It would have to result in your frame or wheels heating up. There's not a lot of evidence that this happens.
 

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Besides, that which dose not bend, will break!
 

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+1 on the wheel flex being the more likely issue. You may want to check your spokes - or have them checked to see if tension is proper.

Also are you a heavier / more powerful rider? Power and weight will flex both the frame and the wheel more than a smaller finesse rider.
 

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MooseDawg said:
Second, my question. I just changed my brake pads, readjusted the distance from the wheels, and, although the rear wheel does not rub when the bike is in the stand, it rubs under load, esp up hill. Thus, I've spread the gap a little more to compensate.

Any insight would be appreciated.

-MooseDawg
How close are your pads to your rims? I'm seeing some people adjust really close like 1mm which doesn't allow for any wheel flex and if you hit one pothole, the brakes are rubbing. I've found a 1.5 - 2mm gap (each side) to be much more usable in the long run.
 

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It sounds to me as though something's wrong unless you're an exceptionally heavy/strong rider. Are you sure the q/r s are done up tight? Bearings adjusted correctly (never used a ksyrium so I don't know if they're adjustable) and not nackered? Spindle not broken?
 

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Discussion Starter · #9 ·
pdh77: I weigh 170, and am pretty powerful, I guess (I don't have a watt meter, so can't say w/any certainty). I'll check the wheels/spoke tension.

android: I did try and set the pads really close--probably toward the 1mm as opposed to 2mm. FYI: I've been riding for about 5 yrs; some crits, some road races, but I have an 11 mo old daughter, so, right now, I'm just trying to maintain; started working on my bike in the past yr or so w/o training, and enjoy working on my bike--I'd rather build one up, or upgrade my current bike, than buy a new one--it's just fun (and cheaper) to tinker.

fastpedaler: the rear spindle is ultegra; bearings are fine.

Based on all of your thoughts, I'm thinking the diagnosis is horse rather than zebra: I probably just set the pads too close.

Again, thanks for your time and advice.


-Moosedawg
 
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