Bicycle Tutor

I had a derailleur replaced on my Trek 7000 and have never been satisfied with the performance.

Today I noticed while adjusting the lateral position that using the 1-7 position the derailleur rides way up high...with the gears touching the cluster.

Image:



Is this a problem of adjustment?
Or the wrong model derailleur?
Or some other issue?

Not too sure on this one but gonna take a shot. Your chain length maybe too long. Did you have the length of the chain changed after putting this Shimano Deore Derailler on? Who replaced your derailler? Before I go on Ill let you answer.

(Sep 16, 2012 04:29 PM)Bill Wrote:  Not too sure on this one but gonna take a shot. Your chain length maybe too long. Did you have the length of the chain changed after putting this Shimano Deore Derailler on? Who replaced your derailler? Before I go on Ill let you answer.

I was a actually a while back when the derailler was changed so I'm not sure if they changed the chain.

I did think that maybe the chain could be shortened, but when I put the gears into the 3-1 position, using the most chain, that also seemed to be at the other end of the maximum stretch of the derailleur!

SHORT STORY

I had it replaced at a bike repair shop which has not often come through for me. This was part of a major overhaul after a crash where I wrecked the original wheel and derailleur.

LONG STORY

At that point I went through repair hell as they put on the wrong sized wheel and for a while every month a spoke would pop. I kept asking them if it was the wrong size and they insisted that it was ok. I went to another shop and they said the same thing. Finally I went to REI and demanded they give me the exact size (32mm width) I wanted, and they custom made me a wheel (they said there was nothing available off the shelf). That has worked great ever since.

But I also noticed that I seem to exert myself a lot more than other people on hills and also the chain was jumping when I was in say the 2-3 position and I exerted myself for speed. I made few turns on the rear cable adjustment and noticed it make a significant difference! But as I explored more I also noticed how the derailluer was riding up.

I went and looked at the original equipment for the Trek 7000 and I noticed the derailleur was much smaller. If you look at the picture, the arm with the two gears is very,very long. I'm not sure why that is or why the repair person picked that derailleur.

I am thinking of going back to REI...who did the work right...and asking them to replace the derailleur, but I was posting to see if anyone else things that model is absurdly sized and positioned to my bike!

Well, the chain jumping is from excessive wear on the drive train, at least the sprockets look all pointy to me in the picture.

That the custom built wheel works better ans is more durable is no wonder: the lower-end factory built wheels are not properly built, they are not stress relieved, the spoke tension is too low and uneven, the spokes are still torsioned... name a builder's mistake, they mostly got it. A custom made, hand-built wheel by somebody knowing what he (or she) is doing and who is not taking shortcuts is superior. A badly "built" (using that term very broadly) wheel is a nightmare and spoke breakage is a sure sign for that (unless you go downhill mountain biking with a light road bike wheel built for weight saving and aerodynamics = wrong use).

With the pizza plate size large sprocket you have you probably need a long cage dérailleur, but you should look at the differnece in total teeth ( (#teeth on large chain ring + #of t on large sprocket) - (#t small chain ring + #t small rear sprocket) ) between the large-large and small-small gear combos (not that you should use them at all). This determines the required capacity of the dérailleur. Another measure is the max sprocket size (in teeth) that the dérailleur can handle. Most modern road dérailleurs don't go above 27 teeth. Look at the Shimano tech docs and check the specs for the dérailleur you would want.