Bicycle Mechanics - Shifter Cable Tension Changes with Temperature?
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12-23-12, 03:11 PM
Do RD shifter cables expand/contract enough to cause indexing to drift out of whack between summer and winter riding?
the sheath should expand contract at close enough to the same rate to make it a wash. at most you'd be looking at about a 1/4 turn on the SiS adjustment (the stops aren't going to change).
IMO there shouldn't be an issue with contraction, even with aluminum or carbon frames. Yes there are differences, but since everything is moving in the same direction, you're not dealing with the total change, but only with relative differences among parts.
However, I do notice differences in shift performance, mostly in upshifts, because of stiffening of cable lube.
12-23-12, 04:03 PM
I'm feeling a similar thing with my shifting as it gets around freezing. I'm now convinced its more just road filth making shifting funny.
12-23-12, 07:12 PM
I have used bikes with 8 and 10 speed indexed shifting in temperatures between 35 deg. C and -30 deg. c, and I nver noticed a difference in shift precision... sometimes it shifts more slowly but more slowly shifting up and down so probably because everything is stiffened up in the cold.
certainly most greases become hard as wax at sub-freezing temperatures.
Andrew R Stewart
12-23-12, 08:13 PM
One thing not yet mentioned with Winter riding is the icing of any water. If any moisture is inside cable casings (and freewheel/cassettes often as well) the freezing will cause issues.
My shop in cleveland serviced some of the town's bike messengers. At least a couple times a Winter one would come in complaning of a freewheel that lost it's ratchets and would either not grab forwards or lock up and not coast. We had an old steam radiator by the door. The gaps between the loops were perfect for road tires to be slid into. You could say it was a bike rack and the guys would use it to park their bikes. Well after a few minutes of explaning the problem and generally shooting the breeze one of us would go over to their, now, dripping bike and low and behold their freewheel worked!
Cleaning and drying out the freewheel then lubing it would help extend the amount of time before it would repeate this. I knew Winter riders who never allowed their bikes to warm up. Water will sneak into gaps, frozen water won't (snow/ice). I always thought this was a bit extreem. I like to error on the too much TLC side of things. Andy.
Yes, the absolutely worst temperature band for bike riding is from about 28-32F. Warmer, and freezing isn't an issue, much colder, and everything's frozen already. But at slightly sub freezing pavement temps may be above freezing, so water sprays up and freezes on contact with your colder bike. Not only does it jam mechanisms, it can make a bike incredibly heavy. I've had my bike gain over 50#s in ice glaze. I've had rims glaze with ice rendering brakes 100% useless.
If you ride in the winter, it's important that everything is well lubed with water repellent oil, and that there are no spaces for water to wick into. But even with the best of preparation, don't be surprised if you leave your bike outside for a short while and come back to fine parts, like chains, freewheels, and headsets frozen solid. I have fond(?) memories of having to massage the chain to free all the frozen links.
Winter riding may be one of the best arguments for riding fixed, or with an IGH,
12-24-12, 04:30 AM
Yes - and it's worsened by the cold air being thicker, slowing down the rate at which the derailleurs can swing.
Andrew R Stewart
12-24-12, 07:12 AM
The other problem with the Winter on Earth, as far a riding goes, is that it contracts. Kind of like an accordian. So the hills get steeper and taller. Of course as Summer comes and we get fitter the earth expands with the heat and those hills get smaller and shallower:) Andy. Happy Holidays.
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