Bicycle Mechanics - Front DR question
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When I'm in the middle ring on my bike, the bottom of the front dr scrapes against the big ring. I can trim it so that the dr straddles the big ring and doesn't scrape, but that isn't really a long term solution. This is a pretty new bike (two weeks old), and I'm sure that the lbs would be happy to fix it for me. However, I don't think that I'll be able to get to the store for about a week or so. How hard is this to adjust? Could I just raise the entire dr by lifting the clamp a bit? Is there a better way?
Or, do you think that it would be better to get the shop that I bought the bike to make the adjustment?
07-09-03, 09:56 PM
Sounds as if the der is a bit low to me. The lbs is of course as always the best choice for a fix but you could try to fix it yourself if need be. First shift to the small chainring up front. Then detach the cable from the anchor bolt on the front der. Then loosen the clamp and move the der up only as much as you need to clear the chainring. (If it is too high then it will shift poorly.) Make sure the der is straight with the chainrings and snug the clamp up. Then reattach the cable pulling it finger tight under the anchor bolt. Check the shifting and if it doesnt go to the larger chainrings on the first try then unscrew the barrel adjuster on the shifter where the housing enters it to tighten the cable. Good Luck,
07-09-03, 11:50 PM
Bezzo......also, don't be afraid to 'bend' the derailleur cage to prevent these minor, but annoying scrapes. Sometimes, bending and re-shaping are quick and rather effective remedies..... always worked for me... (LBS's do it all the time.....when you're not looking...)
Always best to go the adjustment route first rather than force a solution by bending. A bent derailleur, especially if you aren't sure of what you are doing, could result in other unwanted things like poor changes. The bike's also under warranty and if the LBS identifies any "bending" when you do back to them, you've lost the warranty on that part. The cage is designed with certain features to make shifting of the chain better, and bending one section might change the dimensions of another section.
Barnett's manual has all the descriptions needed. BikerRyan is pretty well on track, but it's the clearance over the *big* chainring you need to make the adjustment for, and the clearance is between 1 and 3mm. You will have to move the derailleur out by hand, to check the clearance (because you've disconneted the shifter cable), and you may need to make several adjustments up and/or down with the seat tube clamp before you get it right.
The outer part of derailleur cage also needs to be parallel with the chainrings, and you will almost certainly need to check this as moving the seat tube clamp up and down may require a certain degree of rotation. Barnett's is a little detailed on this, but usually making sure the outside (right) side of the cage is parallel adjacent to the big chainring is sufficient.
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