memnoch_proxy

I'm considering an upgrade to my rear derailleur on my XC. It has a tough time upshifting but a fine time downshifting. I'm going to start by re-routing the cable. However, I have a shimano style derailer and a 34T 8 cog cassette...I can get into 34T just fine. When I want to get into higher gears, I often have to pedal up to 10 revs before getting into a smaller cog. Downshifting is much more responsive. Does this have to do with cable length? And is the a better derailer for tandem-length cables that I should consider?

xtrajack

I have a 11-34 tooth, 8 speed cassette as well, on an Xtracycle. I haven't had any issues with the stock derailleur that came on my Kona Fire Mountain (before I X'ed it).
I am running vintage Shimano Fingertip shifters (friction), I don't know if that is why I am not experiencing the issues that you are.

I don't remember having issues with the indexed shifters, before I changed to friction shifters. I swapped out the indexed shifters for the friction shifters for reasons unrelated to performance.
I am not a trained mechanic. I am sorry I couldn't be of more help to you.

vik 

Unless you have a reverse action derailleur [not that common] you are pulling the chain onto a bigger [easier] cog at the back, but the derailleur's spring has to pull it back down to a smaller cog. If you are using full run cable housing and/or have dirty cables or sharp bends in the cable routing the friction inside the housing makes the shift to a smaller rear cog poor.

The solution can include any and possibly all of the following:

- low friction cables and housing
- better routing of the derailleur cable
- getting rid of a full run of cable and replacing it with only partial cable housing sections
- checking the derailleur's return spring

It's quite possible there is nothing wrong with the derailleur at all.

AdamDZ

I agree with Vik: most likely there is nothing wrong with the RD. Replace the cable and clean the chain, cassette and the RD first. If the RD has hard time shifting to a smaller cog that usually means dirty cables: there is too much friction in the cable so that the RD spring is unable to pull the cable back. That is assuming you have a traditional RD as Vik pointed out.

For the first time ever I installed a full housing, sealed cables from Gore. I wonder how that will work.

memnoch_proxy

Thanks for the advice. The cable, cable housing probably only has 100 miles on it, replacement was the first thing I did when this problem started occurring. I also have a rollamajig before the RD. The cabling is stainless with TriFlo applied to it, but not teflon cabling (LBS discouraged me to, apparently teflon rubs off cables quickly) but the housing should be be teflon coated. The RD is of unknown extraction, it might have a few thousand miles on it. When I changed the cabing, I did notice that there was a permanent bend in the cabling where the rollamajig lived. I'm tempted to reroute with a bigger loop and no rollamajig, but make the housing run along the FreeRad say straight instead of curving. Maybe I can post a pic tonight so yall can see. I can also check the specific model of RD.

Is it feasible to evaluate the tension in the RD spring?

memnoch_proxy

Speaking of wanting to route a straight run u-turn away looks pretty trick :-) Is this only for certain RDs?

coldfeet

I seem to remember reading somewhere that the extra chain makes it a little harder for the RD to "pull back" to the smaller cogs. The fix that was mentioned involved adding a little "helper spring" attached to back end of the Xtracycles frame. ( bungee cord ) I think it was on the Xtraxcycle forum. I also remember reading that they recommended a better than average RD because of this.

vik 

If you have a low cost unbranded rear mechanism I wouldn't feel too bad about an upgrade.

If you get a LX/XT level mechanism and try it you'll at least know you've got no derailleur issues and you have to focus on the cable/housing. Your LBS may well have something slightly used you can borrow to troubleshoot the situation.

memnoch_proxy

Here's some pics of how I have the RD cable run. This one might be enough:



I think I'm going to get a barrel adjuster, remove the rollamajig, route the cable outside the fender stays without trimming the housing and see how that handles.

AdamDZ

Put the bike on a stand, hang it or flip it over, so you can spin the wheels by turning the pedals in place. Detach the cable. Spin the pedals and push the RD with your fingers (watch the spokes!!!). Then let the RD go (keep spinning). Does it still have hard time returning? If so, then yeah, it's the RD. Otherwise it's the cable. Make sure there are no sharp curves.

memnoch_proxy

I took off the rollamajig and routed the cable outside the fender stays, going flatter along the chainstay and I am able to upshift within a half a pedal stroke. Much better! The shifter feels like it has plenty of spring left in it. After I cleaned it up *blushes* it is a shimano XT. Thanks for the advice!

AdamDZ

I'm glad you figured this out. Keeping the cable run simple, straight with smooth curves is important. Oh, and if you use zip ties to attach it, go easy on them too. Shimano XT RD should last well over a decade unless used in extreme off-road conditions, or unless you physically damage it. I've just retired a Deore (non XT) RD, that was about 10 years old just because I had some extra RDs, but it still has life in it.