fix her grinding rear?

[Yeti]

Let's just get it out of the way: photos of my wife's grinding rear might make this thread less worthless. I'm trying to do some basic tuning of her rear derailleur (2003 XT), and am running up against some issues.

The problem: the chain does not like to be in the two biggest gears in the rear cassette (Deore HG-50 11-34T, 9-speed). It doesn't seat well on those gears. When you shift up from the smaller rear gears, the chain hangs up high on the teeth of the second-biggest gear and occasionally leaps up onto the biggest gear.

Some observations: the indexing on the rear shifter (LX) seems screwy. When the chain is in the 7th biggest (of 9) gears, the indexer is just about in the middle of the index window. Despite all of this, the chain runs fine in the 7 smallest gears of the cassette. This is a 2003 bike, with the original drivetrain as far as I know.

Questions: How do I fix this? For the riding we do, it's very nice to have a full range in your rear cassette. Is this likely to be a simple matter of chain stretch? What about cassette tooth wear? Or is this a matter of my ineptitude at tuning the rear derailleur? I've played with the limit screws in a semi-scientific way, and haven't had any luck at resolving the issue.

While we're talking tuning drivetrains, I'm also having issues with getting her front der to drop into the smallest ring. The limit stops don't seem to be the problem there; when unloaded (i.e. upside down) the shifting into granny works much better than under load. Ideas?

[mntlion]

Rear Der

get a store to check chain strech. (or buy the park tool)

get a store to check the der hanger adjustment. (or buy the park tool)

when where cables and housing last changed? more then 90 days, changes them

limit screws are for a max and min (if the chain goes off the cogs totally) dont touch.

play with the barrel adjustment screw (where the cable goes in).

F der: is the bike a full suspension? if the der will not go to the inside enought with the limit screws.

check the der is at the right height, (2mm from the big ring to der cage)

check the der is straight with the chain

then play with the cable tension

[kidwoo]

What mtlion said

PLUS.....check your b-tension screw. That's the screw on the rear of the derailleur that adjusts the angle of the dangle. Tightening it will hold the derailleur more clockwise, bringing the top pulley off the larger cogs. If that pulley is dragging, you get the behavior you described. Shimano derailleurs are notorious for these things getting stretched easily.

As far as the front derailleur goes, like mtl said, it may be the bike design or you may have to adjust the limit screw AND the cable tension. And you should whenever possible back off on the pedals when you downshift.

[Yeti]

Sounds like some good tips. As for that b-tension screw, it did appear that with the chain in the biggest cogs, the pulley was basically touching (almost meshing with) the chain at the point where the chain hits the cog.

Yes, it's full suspension. I'll keep working on shifting early and not-under-load.

[Natedogg]

get a store to check chain strech. (or buy the park tool)

Or use a ruler. First pin in link to first pin in the next link = 1 inch. Exactly.

[mntlion]

Or use a ruler. First pin in link to first pin in the next link = 1 inch. Exactly.

is that for a new chain, or when it is time to replace?

good tip

[Pedro]

I encourage everyone to dickaround and try to to adjust things themselves, but somtimes you gotta bring it to the shop. I like to do a lot of stuff myself, but the good thing about bringing it to the shop, is you bring it in they fix it, sometimes you try to self diagnose the problem and you buy a new component and there is still a problem. You might be overlooking somthing obvious. Who knows??

[XtrPickels]

is that for a new chain, or when it is time to replace?

good tip

New chain, if its stretched more than that, time to replace

[DerJaeger]

Minor thread hi-jack: is there a good source for learning this stuff? I'm clueless when it comes to derailer tuning and really love to learn how to do it properly.

[Natedogg]

^^^
Like Pedro said, its good to dick around with it yourself. But youre right, you do need some kind of formal training in addition to trial and error.

This guy is a whiz. Ive been using tidbits from his site for years.

http://www.sheldonbrown.com/

Never met him and his shop is only a five-minute jaunt up Chestnut Street... I really gotta stop in there...

[Pedro]

Another Good reference for trying to dick around...

http://www.mtbr.com/mb101/dtguide/dtguide.shtml

Kind of gives you the baiscs to what the limiting screws and cable tension actually do.

[ShawnB]

Originally Posted by mntlion
is that for a new chain, or when it is time to replace? good tip.

New chain, if its stretched more than that, time to replace

If it's anything BUT new, it will be stretched more than that... However:

A) if it's between 1" pin-to-pin (i.e. just installed) and 1 1/16" pin-to-pin, you're basically OK.

B) if it's creeping up on that extra 1/16", it's time to think about replacing it, and

C) if it's at or over 1 1/16" pin-to-pin, change it NOW, or even better, last week.

BTW: I hereby volunteer my rear der. as the Rescussi-Extey for newby maggots to practice wrenching on: It can't possibly get worse than my own expert "adjustments"...

[mntlion]

park tools makes a great book on how to tune your bike. also the park web site has info on what the tools do.

[gravitylover]

DJ, where are you in DC? I have two friends with shops down there that have repair classes you can take. Lemme know and I'll point you to the closest one.

[flowtron]

Aaaaand finally, the hanger might very well be out of alignment.
My advice is to take it to a shop. You've monkeyed with the stop screws, the hanger might be out of alignment, and you may very well need new cable and housing, and finally and perhaps most importantly, its your woman's bike. Screw up your own bike all you want...but take my advice here: You want your woman's bike to run clean.
Zinn and the Art of Mtn Bike Maint. is a good book to buy and tweak on your bike with it over the winter.

[L7]

Also check side to side play on chain. If it's too long it will have too much side play but it is possible it could have too much side play and not measure that long. The Front issue sounds like the chain is shot. The rear sounds like derailluer and/or hanger out of alignment PLUS a shot chain wouldn't be helping.

Ask Mtnlion, I change chains a lot, keeps shifting much crisper and saves changing the whole drive train when everything gets worn way down.

[Yeti]

...finally and perhaps most importantly, its your woman's bike. Screw up your own bike all you want...but take my advice here: You want your woman's bike to run clean.

Indeed. Since I'm somehow "responsible" for mech issues on her bike (partially because I caused them by dicking around with the screws, and maybe by bashing her derailleur/hanger into that tree last month... oops), I start losing credibility and a ride partner when her bike doesn't run right. Solid advice.

[doublediamond223]

Minor thread hi-jack: is there a good source for learning this stuff? I'm clueless when it comes to derailer tuning and really love to learn how to do it properly.

A lot of LBS's have classes you can enroll in, usually for free. I learned most of the techniques mentioned here in the first few weeks of working in a shop, hands-on experience can't be beaten.

BTW, the chain on my dad's 10-year old trek rigid that I'm riding around campus is stretched beyond the range of the park chain checker tool, lol. I just don't care. I took the entire driveline off of it in august and soaked it in the parts washer, that's about as much maintenance as it's going to get. The crank and cassette are severely worn, so replacing the chain would really be a moot point. It runs acceptably with weekly lubes, so it's fine for something where the main goal is to not have it stolen. Of course, I miss my SJ FSR...

[DerJaeger]

DJ, where are you in DC? I have two friends with shops down there that have repair classes you can take. Lemme know and I'll point you to the closest one.

I live in Silver Spring MD, but work in Georgetown. I'm within easy reach of several of the better bike shops in the area.