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Time for a tune up?

Old 10-11-04, 11:59 PM
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unrelated
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Time for a tune up?

Is it normal that the rear derailler refuses to shift while pedalling uphill (referring to XC)? I have Deore LX on the rear and it doesn't shift when I am pedalling up hill. Then when I reach the top, or when I ease down on pedalling, it then shifts. So I have shift in advance before I hit the spot.

Also, how often do you guys do a tune up, say if you ride once a week?
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Old 10-12-04, 06:55 AM
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Al.canoe
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Mine always up-shifts well under heavy load at the rear. I don't do tune-ups, preferring to adjust things at the fist sign that all is not perfect. I clean the mechanical parts (I don't worry too much about the frame) and inspect my mountain bike after every ride which for me is between 18 and 24 miles. That's a lot of use off-road.


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Old 10-12-04, 07:01 AM
  #3  
Matt Gaunt
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Good call.

My MTB has never refused to shift apart from when the release spring went in the shifter.

Maybe take a look at the two adjustment screws at the rear mech and have a play - that usually stops slow-ish shifts for me. I don't ride anything like as nice as Deore LX so you shouldn't be experiencing mis-shifts.

I tend to look over my MTB after every couple of ten mile rides at least, usually after every ride if I just do one a day. Pays off though.

Good luck and if you don't have any results, let your dealer have a look.
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Old 10-13-04, 03:42 PM
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You should always ease pedalling pressure when changing gear while going uphill. You need only do it momentarily but saves wear and gives slicker shifts.
You need to also ensure your B-tension adjusting screw is set correctly for crisp shifting. The screw is the one on its own ar the top of the derailleur behind the cable adjuster. The screw touches a lug on the frame and adjusts the tension of a spring which keeps your jockey wheels from touching the cogs.
Put the bike in bottom gear and adjust this screw out until the top jockey wheel nearly touches the cog. This will give much faster shifting under pressure than if the top jockey wheel was further away from the cogs.
If you can't identify the screw, go into the Shimano website and view the exploded, labelled diagram of a rear derailleur there which will help you.
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Old 10-13-04, 04:08 PM
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You didn't tell us anything about the history of the bike. Worn cogs and chain will act the way that you describe. It's easy to tell if the chain is worn, just take an ordinary ruler and see where the closest chain rivet falls relative to the 12" mark. If it's 12 1/8" or more, you need a new chain and a new cassette or freewheel.

Incidentally, one of the other posters suggested playing with the derailleur's limit screws. That's bad advice. Once the limit screws are correctly set, they never need readjustment. Most rear derailleur adjustments are made with cable tension.
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Old 10-13-04, 08:17 PM
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Ok, I am going to clean it up and get a new chain. The chain is pretty worn although I have pertty low miles on it. I think it's mainly due to the sandy surface I ride on. My friend who used to race mt bikes looked at it and can't really find any problem. He suggested, other than the chain factor, that it may be the hub or something, but unlikely.

Just to give a bit more info:
This is a 01 GT Avalanche 1.0 with Deore on the front and LX at the rear. I got it not because I am a good rider, but because it was sold to me at a very good deal. I wasn't looking for anything this good but it actually fall within my budget.
Then it sat there for 2 whole years, until recently I got it back onto the trails. I've ridden 3 times since mid Sept, about 40miles in total, so that's practically new.

Shifters are Deore Mega, and my friend said it isn't the best, which may be one of the reasons too.

I am just going to do what I can now, wash it and get a new chain. I'll see how it goes. If not, I just have to change my way of climbing those hills.
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Old 10-13-04, 08:27 PM
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When I got out my single bike after not riding for over a year (knee surgery) I found I had a bike which didn't like to shift.

Cleaned the chain, lubed the chain, cleaned the cogs, lubed the cogs, cleaned the chain rings, lubed the chain rings, cleaned the derailers, lubed the derailers. Do you see a pattern here?

At this point, some minor trimming of cable tension made the bike shift properly once again.

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Old 10-14-04, 01:10 AM
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Just to rule out another possibility, you should make sure that your derailleur isn't bent and that it moves freely. You probably won't have to worry about that unless you crashed or dropped your bike or something, or if the derailleur is really dirty or rusty.

As far as bike maintenance is concerned, it is an ongoing and neverending process so long as you are riding a bike. A rule of thumb is an hour or so of maintenance for every 5 or 10 hours of riding, and maybe more if you ride when it is muddy, extremely dusty, or wet.

Once you get the shifting problem(s) ironed out you probably won't have to deal with any for quite some time. For me, this happened when I got rid of grip shifters. They were so damn light, but such a pain to keep clean and to have the right cable tension. Maintenance will never compensate for what design lacks. In your case, unrelated, LX should function pretty well.

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Old 10-14-04, 01:27 AM
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1.
I can easily change the rear gears at any steepness, under any presssure, BUT, it is almost impossible for me to change the front set of gears pedalling up hill. Maybe becasue they're bigger?

2.
In answer to your other question about 'tuning up', i also ride about once a week. I wipe the bike down with a damp cloth, and just get a tooth brush and clean the derailars. After about every 3 long rides i give the rimes a good cean, the cog and gears a clean, nearly everything. This takes at least 30min, but its worth it. Dirt and grime mess's up cables, parts and performence. I say its worth the clean.

3.
I take it to the LBS at least once a year, now every 6 months for a full service. But i still do take it up for small problems i have.

Hope this helps.

Last edited by blue_neon; 10-14-04 at 01:33 AM. Reason: more information
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Old 10-14-04, 07:40 AM
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Well its important to still know it is always going to be harder to shift well if you are pedaling uphil hard, it puts more tension on the chain. So really make sure that the derailleur is in line with each cog by adjusting the screws, if the shifter says its on gear 5 then make sure the thing is really right on gear 5, even me, being an anti shimano guy, well you shouldnt be having issues so yea tune that hting.
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Old 10-14-04, 07:41 AM
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oh i forgot the second part of the question, i tune my bike whenever i find something not workring perfectly. useually after a ride i will look it over real quickly.
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Old 10-14-04, 08:50 AM
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I can easily change the rear gears at any steepness, under any presssure, BUT, it is almost impossible for me to change the front set of gears pedalling up hill. Maybe becasue they're bigger?
No, it's because of the design of the bike. The rear derailleur pushes the chain left/right in a place where the chain is not under pedaling tension. The front derailleur acts on a part of the chain that is under a lot of tension while you pedal, because it's the part of the chain between the top of the front gears and the top of the rear gears that pulls the rear gears around. The derailleurs can't move a chain that's under a lot of tension, but there isn't much tension on the bottom of the chain, just the tension from the springs in the rear derailleur.
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