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October 10, 2005
First flat on the new bike, part II
Not sure whether this is advancement of the last few years, or whether it was already true before, but I don't seem to have to use tire irons with either bicycle bought since 2004. You change the tire and the tube with bare hands, and so are less likely to puncture the new tube before you even get the tire inflated.
I could find the little hole in the inner tube, a very small hole indeed. Maybe the puncture was a pinch, as there appeared to be a little crease in the tube with a half moon shape around the tiny puncture. I cannot tell for sure, and could find nothing sharp anywhere inside the tire or the rim. Right now I simply hope the flat doesn't come back in the new inner tube.
Next, the chain has been rubbing since at least this morning on the outside of the front derailleur when I use the small sprockets in back. So I used the screw adjustment on the front derailleur cable holder next to the levers to pull that more taut and push the derailleur out. This only partly resolved the problem of rubbing. The front derailleur is well centered when the chain's on the little chain ring in front. I'm not so sure about centering on the other two.
Dad and Matt suggested I might want a stand. It sure would've come in handy tonight. Adjusting the derailleurs and having to hold the bike at the same time is a pain. The same's true for adjusting the wheels that have disc brakes when you put them back on. The disc brakes themselves are fine, but the tolerance is tiny. You have less than a milimeter to play with on either side of the disk.
Derailleur and brake adjustments remind me of tuning a guitar with a floating bridge. For someone with no patience and no dexterity, both are a sure fire way to raise the blood pressure.
Speaking of bike related things that would raise my blood pressure, my brother Matt apparently built a bike himself from components. Bravo, Matt!
Posted by Mark at October 10, 2005 09:26 PM
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Comments
I believe for chain adjustment, the set screws on the derailleur only set the maximum travel distance of the derailleur, that is, how far to the outside or the inside the derailleur will go before the set screws stop it. However, these set scrrews will not change the position of the derailleur in relation to the various postions of the shifter. To set where the exact position of the derailleur will be when the shift level is in a certain position, you adjust the derailleur cable length. There is probably some adjustment unit you can twist where the cable leaves the shifter or enters the derailluer or both. For more extreme changes in cable length, you can loosen the screw that locks the cable to the derailluer arm and pull the cable tighter or looser with a pair of pliers. It sounds like your cable might have just stretched a bit since it was new and now, when tighten by the shifter, will not pull the derailler quite far enough hence the rubbing. sheldonbrown.com is one of the best sites for all sorts of information about bicycles, adjustments and repairs -- really a quite impressive site since it seems to be the work of one person.
Posted by: Teena at October 11, 2005 02:32 AM
You're probably right about needing to tighten the cable.
I think there's been some problem in general about the way the front derailleur's set up. There's always been a bit of rubbing, but I've had difficulty pinpointing it.
At higher speeds I get a strange ring from time to time, like metal glancing off metal. Must have a look at Sheldon Brown's site. I've added it to my links at del.icio.us.
Posted by: Mark at October 11, 2005 08:30 PM