bike tune up question. rear derailleur

[vash]

ok. i got my bike back from a full rear suspension rebuild. all new bushings.

i just got my bike back from a fresh tune-up when the mechanic showed me my bushings were toasted.

ok, new mechanic..new bushings..done. i refused to pay him to tune it again. i can do this. i thought he would just disconnect the derailleur and let it hang..but no, i dont think he did. yesterday, on my ride, it shifted fine. right up until you put the chain under serious loading by cranking up hills. i got major ghost shifting!! (i think i jammed my right knee when a chain slipped)

anyways..i brought it home, put it on the stand and ran it through the gears. i started over, confirmed the upper and lower stops, and got the thing to shift smoothly.

what about under load? is this an indication that i need a new chain or cluster? i had the chain measured and they told me it didnt stretch that much.

[stuartj]

Check that each link of the chain is moving/swivelling freely. If its not, if its been crimped too hard when joined, it may not be moving through the derailleur correctly and this can cause exactly what you describe.

[vash]

nota..

i am not cross-chaining. this one particular trail is perfect running the middle ring..and running the full cluster in back.

[gtc]

I would check the rear derailleur cable housing length. It sounds like it may be too short, and pulling the cable tight as the rear suspension squats. Try bouncing up and down on the rear suspension and see if it causes the derailleur to move up or down slightly.

[85eurocarrera]

yes, could need new chain and cassette. replace both at same time if you need to.

[Jim Bremner]

Originally Posted by 85eurocarrera

yes, could need new chain and cassette. replace both at same time if you need to.

same. Do not buy cheap chains. I had a fleet of sample bikes when I worked as a rep. Any time I had a new bike I would toss on an xtr/durace chain even if it was an lx bike. It would cost $$$ buy long term it was cheaper.

[cantdrv55]

Agreed, you probably new a new chain. Might as well put on a long cage and mtn bike cassette while you're at it. My steel climber as a 34 tooth cog in the rear and a triple up front. I figure a few extra grams of hardware won't matter much as the rider is overweight already.

[vash]

Originally Posted by gtc

I would check the rear derailleur cable housing length. It sounds like it may be too short, and pulling the cable tight as the rear suspension squats. Try bouncing up and down on the rear suspension and see if it causes the derailleur to move up or down slightly.

interesting!! i'll check

i will more than likely toss on a new quality chain to eliminate it as a possible problem. i found my chain tool last night

[vash]

everytime i think back to chains..i seem to remember a certian link that you disconnect at..but this is for motorcycle chains, right?

a bicycle chain i can break apart at any link, correct? just count links and match new to old?

[look 171]

I break at any point, but on my Dura Ace chain, there is a specific link. I have never notice the difference. Now you might get a quick release chain link so a tool is no longer needed.

Get a new chain. Your problem will go away. Like Jim said, get a quality one. I like the XTR/DuraAce chain. They are the same. Your balls are worth the extra bucks should the chain breaks under the off the saddle charge. I found that the more you pay for a chain, the quieter and smoother they are.

[look 171]

OH, Cogs usually do not wear out before chains unless its used a lot

[vash]

thanks everyone.!! i mean it.

i was not going to throw anymore real money at this bike.

[jtkkz]

Originally Posted by vash

everytime i think back to chains..i seem to remember a certian link that you disconnect at..but this is for motorcycle chains, right?

a bicycle chain i can break apart at any link, correct? just count links and match new to old?

shimano chains you can break anywhere and use a new chain pin when installing the new chain, yes match lenght of old chain if the lenght of old chain is fine

sram chains have master links that are removable, no pins needed

sometimes new chain may not match up with older cogs and front rings, can cause chain to skip around

make sure rear cable housing is lubed, cable not too tight

[teenerted1]

make sure to get the correct width of chain and cogs/chainwheels


6/7sp wont work with 8sp; 8sp wont work with 9sp; 9sp wont work with 10sp, etc

[John Rogers]

When I was bicycle racing we put on new chains probably monthly at least? This was when riding 500 miles a week in all kinds of weather too. If the chain was nearing the end of it's life and a race was coming up, a new one went on. I used to buy bulk chain from a distributor at about 300 feet at a time but I don't know if you can do that now? I used a teflon based lube that was dry after the liquid evaporated and picked up very little dirt. Here is a link that covers all the things I used to look at and for.

Chain Maintenance

[vash]

man, my chain was dry as a bone!

went over it with some Pedro teflon chain lube..we'll see tomorrow. a new XTR chain is pretty reasonable in price at some of the big online stores. not bad!

[look 171]

Make sure the hanger is straight. If not, it will skip all say long when power is applied

[John Rogers]

I looked at my old bicycle repair manual and went through the notes I had on shifters and found a bunch of things to measure and/or check. Most were hand written notes from some sessions we had with the old (I mean OLD) 7/11 cycling team back in the day.

- Make sure both derailleur pulleys are parallel with the front chain ring. I remember a tool that fit in the holes for both upper and then lower pulleys in place of the axle bolt and had a rod that would rest against the chain ring and the derailleur could be twisted to line things up. Some of the sprinters such as Davis Phinney were so strong they could twist things up pretty good.

- Make sure both pulleys are exactly over each other.

- Make sure the rear axle and cassette is 90 degrees to the line of the chain when the chain is in the mid gear and on which ever front chain ring you use most.

- Make sure the chain ring is completely flat. That was a problem with early Japanese rings as they were so soft.

- Make sure the length of the chain is correct for the gears. Just because it came on the bike does not make it correct. I had the steps to do it but now there is a website that calculates for you.
Bicycle Chain Length Calculator

Good luck