Results 1 to 22 of 22
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452

    Chain jumps down a sprocket in front on bumpy downhills

    Got a Trek Liquid 10 thats bone stock in good shape.

    I go down bumpy trails and when I reach the bottom and start pedaling again I'm constantly finding that my chain is now on the next lower gear. It will do both; jump from big to middle or middle to small. The front derailler will rub and grind away on the chain that's now on the wrong ring unless I half upshift to get it back on the next larger proper gear.

    The bike shifts and works well under coast, flat or uphill. Its only when going down bumpy downhills in which all that jarring is going on that the chain jumps down a size.

    I will note that one of the first things I put on my bike was a Lizard Skin on the right hand 'chain arm' to quiet down all the chain slap that was going on.

    What should I look for or what can I do to help this problem? Thanks in advance.

  2. #2
    EDR
    Reputation: eatdrinkride's Avatar
    Join Date
    Jun 2005
    Posts
    9,029
    when about to take a fast/bumpy/hard d/h section be sure you have already moved your chain in the rear to a large cog. This takes up the chainslack and will help avoid the front from bouncing down.
    Last edited by eatdrinkride; 10-14-2005 at 09:11 PM.

  3. #3
    1x9'er
    Reputation:
    Join Date
    Jul 2005
    Posts
    263
    Quote Originally Posted by eatdrinkride
    when about to take a fast/bumpy/hard d/h section be sure you have already moved your chain in the rear to a large cog. This takes up the chainslack and will help avoid the front from bouncing down.
    You can also try shortening up the chain a bit. When bikes are new, their chains are too long, in my opinion. They set the chain length so that there is enough chain to run the big ring up front with the big cog in the back. That's a rediculus gear combination and there's no point in ever using it. You only need enough chain to run the big ring with the smallest 2 or 3 cogs and the middle ring with the biggest cog. Cutting down the chain allows the derailuer to put more tension on the chain so it doesn't slap around so much. The shorter length of the lower run of chain also weighs less, which helps decrease the slapping too. Just be careful to know what gear you're in and not shift into the big ring unless you're in the smaller cogs.

  4. #4
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452
    There's gotta be something wrong with my drivetrain. Went for a longish 20 mile ride on some new easy trails yesterday. My bike works great except for one type of problem that seems to be a problem of dropping down a gear in front in different situations.

    When I would need to pedal with strong force on a short bumpy steep uphill area, my chain would often skip and grind only once like its trying to change gears. My crank would skip 1/4 a revolution and really throw my stride and effort in the gutter making it 3x as difficult in a section than it should be. This large skipping/jumping of the chain would only occur when the rear wheel would be going over the bumps.

    I wish I could watch and see what its doing but its only on difficult steep or tricky sections where I really can't be starring down at my frt gears while I'm straining to get past the tough terrain.

    It would happen like clock work on one area of the trail every time. It was a 90 degree single track uphill turn with lots of large roots smack center in the turn. I'd bounce my way over this turn fine until my rear tire hit the 2nd root and *CLACK GRUNCH*, my crank would spin a 1/4 turn instantly, I would loose stride and momentum, then it would crunch a bit more and I'd pass through over the roots or, like on the first time I went through this section, the chain would pop off and lay on the bottom bracket inside the small frt gear.

    I really don't ever remember this happening before, its only started to happen lately on my last 4 rides or so. I haven't crashed or changed anything. Under normal situations, it shifts and works flawlessly.

    I'm almost always in the middle frt ring and large rear ring when this happens.

    Its like the bumps cause the chain to flop out of place and miss shift. But how? It even happens when the chain is really tight (due to hard pedaling force up a hill) but throw some sharp bumps in there and it trys to jump down a gear in front.
    Last edited by Destroy; 10-16-2005 at 08:34 AM.

  5. #5
    Bodhisattva
    Reputation: The Squeaky Wheel's Avatar
    Join Date
    Dec 2003
    Posts
    9,613
    Sources & solutions:

    chain is too long...shorten it
    RD B-tension is too lose...tighten it

    and sometimes it'll just happen from all that jarring. If the above doesn't help then you may need to consider a chainguide. That's why DHers use them.
    “Life is like riding a bicycle. To keep your balance, you must keep moving.”

    ― Albert Einstein

  6. #6
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452
    Quote Originally Posted by The Squeaky Wheel
    Sources & solutions:

    chain is too long...shorten it
    RD B-tension is too lose...tighten it

    and sometimes it'll just happen from all that jarring. If the above doesn't help then you may need to consider a chainguide. That's why DHers use them.
    But why all of a sudden? I didn't have this problem in spring. Only recently has my bike developed this problem. I know my B tension is already maxed out. I measured the chain and it is like brand new, no stretch or kinks that I can see.

    Just looking for tips on what I should be looking for that could be wrong.

  7. #7
    just along for the ride
    Reputation: Brown_Teeth's Avatar
    Join Date
    Jan 2004
    Posts
    3,037
    First make sure your drive train is not work out (chains tend to take cassettes and ring with it if not changed). But I think cable routing might have caused your shift cable to dig into the worn cable housing during suspension movement causing ghost shifting. I'd replace your cable housing make it uninterupted for less maintenance needs and if possible make it smooth as possible in the routing. Multiple 90 degree bends make for fast cable housing wear. Good luck!

  8. #8
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452
    OMG, am I a tard.

    Finally spent some good time looking over my drivetrain on my bike upsidedown in bright sunlight this time instead of in a dark 1 bulb lit garage at night.

    Everything is worn out!!!! I never realized this stuff wore out so fast. I've got 900 miles on this thing. Is it normal for rings and chain to wear out this quickly?

    Chain is almost 1/8 inch stretched. Frt middle ring has several really bad teeth and mega wear in spots. Frt large and small ring seem gouged and scratched up. Cassette seems fair I think.

    Suggestions on what frt rings to buy? Got Bonterage Race now.

    I'm a bit unsure of my derailleurs. How does one know and what determines when they need to replace their derailleurs? I've got a LX rear and Deore front.

  9. #9
    just along for the ride
    Reputation: Brown_Teeth's Avatar
    Join Date
    Jan 2004
    Posts
    3,037
    I'd replace the whole drivetrain, JensonUSA.com has LX cassettes for 24$, get a new chain and the front rings too. Derailleurs don't wear just the small sprockets, no need to replace them until they are about gone. Also replace your cable housing, its worn out too. Good luck!

  10. #10
    Space for rent...
    Reputation: SSteve F's Avatar
    Join Date
    Jan 2004
    Posts
    1,012
    If you need a full set of rings, you may be better off to buy a new crank as you can get a great deal this time of year. You then have the option to replace the entire unit or just the rings only and sell the arms on ebay.

    You may also want to consider checking your BB, as you may want to buy a crank/BB combo.

    Check out
    http://www.coloradocyclist.com/commo...20,34945,22975
    It's only pain......

  11. #11
    mtbr member
    Reputation:
    Join Date
    Apr 2005
    Posts
    37

    future consideration

    In your case replacing the entire drivetrain is probably advisable. However your LBS can can cast an experienced eye on everything to know for sure. If you don't already have one get a chain checker, and check your chain regularly for stretch. Replace your chain often (of course as needed), but maybe 2/3 times a year. The rest of your drivetrain will last much longer. Maintain your chain! You may want to check out "Purple Extreme" chain lube, it's awsome.

    Good luck

  12. #12
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452
    Just posting an part update that may prove interesting to some:

    I bought a SRAM PC950 chain from the LBS and installed only that on my current condition bike from my above posts. Chain that was on originally was a Shimano HG-53 rather worn and stretched.

    Just got back from my normal ride I aways do. 2 huge things I noticed:

    1. Front middle ring skips horribly now when putting medium or higher power to the pedals. Don't need any bumps or anything for this to happen. Light power is ok. Small and big sprocket are ok at any power level.

    2. Rear derailleur shifting was slower and less solid feeling.

    Never knew a chain could cause so much havoc. I may have to go back to a Shimano chain. Dunno. Will wait till I replace all 3 front rings to make a final judgement.

  13. #13
    just along for the ride
    Reputation: Brown_Teeth's Avatar
    Join Date
    Jan 2004
    Posts
    3,037
    LOL chains are steel your rings are AL you are lucky you didn't chain suck and really mess up you knee bouncing off the top tube with that new chain. Get real you DESTROYED your middle ring minimum replace it unless you want to tell us something we all ready know, you can't reason away from friction wear, pla you pay

  14. #14
    MTB B'dos
    Reputation: LyNx's Avatar
    Join Date
    Oct 2004
    Posts
    17,698
    Quote Originally Posted by Destroy
    Just posting an part update that may prove interesting to some:

    I bought a SRAM PC950 chain from the LBS and installed only that on my current condition bike from my above posts. Chain that was on originally was a Shimano HG-53 rather worn and stretched.

    Just got back from my normal ride I aways do. 2 huge things I noticed:

    1. Front middle ring skips horribly now when putting medium or higher power to the pedals. Don't need any bumps or anything for this to happen. Light power is ok. Small and big sprocket are ok at any power level.

    2. Rear derailleur shifting was slower and less solid feeling.

    Never knew a chain could cause so much havoc. I may have to go back to a Shimano chain. Dunno. Will wait till I replace all 3 front rings to make a final judgement.
    Yup from that report I'd have to agree with BT and say you've definitely hosed your middle-ring and I would bet the cassette too. Take the advice and change the middle-ring and get the LX cassette off Jenson for $24 (I just got one and it works sweet and is lighter than the PG950 I had on). Check your chain on a regular basis (as in every month if your riding alot) and change your chain if you notice any stretch - if you messure it and find it's started getting stretch replace it, since a chain costs way less than an entire drive-train. I may have hossed something on my DT 'cause I didn't replace my chain as soon as I saw it wearing - just replaced it with 1/32 stretch and it may at that have damaged my (super soft) XT middle ring.

    Just an FYI.... SRAM chains are not as laterally flexable as Shimano. I still like them but will not be buying one anytime in the near future at the prices SRAM is selling them at - I can get 2 Shimano XTR chains for the price of 1 SRAM high end chain.
    One day your life will flash before your eyes, will it be worth watching??
    MTB Barbados
    My Phantom pics

  15. #15
    MTB B'dos
    Reputation: LyNx's Avatar
    Join Date
    Oct 2004
    Posts
    17,698
    Quote Originally Posted by LyNx
    Yup from that report I'd have to agree with BT and say you've definitely hosed your middle-ring and I would bet the cassette too. Take the advice and change the middle-ring and get the LX cassette off Jenson for $24 (I just got one and it works sweet and is lighter than the PG950 I had on). Check your chain on a regular basis (as in every month if your riding alot) and change your chain if you notice any stretch - if you messure it and find it's started getting stretch replace it, since a chain costs way less than an entire drive-train. I may have hossed something on my DT 'cause I didn't replace my chain as soon as I saw it wearing - just replaced it with 1/32 stretch and it may at that have damaged my (super soft) XT middle ring.

    Just an FYI.... SRAM chains are not as laterally flexable as Shimano. I still like them but will not be buying one anytime in the near future at the prices SRAM is selling them at - I can get 2 Shimano XTR chains for the price of 1 SRAM high end chain.
    Just an update :@ I definitely hossed the middle ring of my new XT crankset. I only got it just about 2 months ago, when the SRAM chain was on it's way out and didn't change the chain when I installed the new crankset and this is my lesson - 1 worn out middle-ring The 1st chain I had was a Shimano HG53 which I then replaced at 1000 miles (with no stretch but thought ita smart move) with the SRAM PC59 which doesn't seem to have lasted as long (all be it the 2nd 1,000 miles were harder than the first 1,000 since I was getting accustomed to my new bike) Anyway lesson learned changed your chain if you're changing your crankset. Just hope this middle-ring holds up for me till I find a replacement (it's about twice as heavy as the Shimano one)
    Last edited by LyNx; 10-21-2005 at 08:52 PM.
    One day your life will flash before your eyes, will it be worth watching??
    MTB Barbados
    My Phantom pics

  16. #16
    just along for the ride
    Reputation: Brown_Teeth's Avatar
    Join Date
    Jan 2004
    Posts
    3,037
    LX shimano chains are cheap and strong, problem with rings like you said depends on use, I have a wall of worn chains hanging up, might make a nice Halloween project, can't seem to get more that 800 mile out of one. Best way to measure them is over 4 feet, easier to see the wear, best rides!

  17. #17
    MTB B'dos
    Reputation: LyNx's Avatar
    Join Date
    Oct 2004
    Posts
    17,698
    Quote Originally Posted by Brown_Teeth
    LX shimano chains are cheap and strong, problem with rings like you said depends on use, I have a wall of worn chains hanging up, might make a nice Halloween project, can't seem to get more that 800 mile out of one. Best way to measure them is over 4 feet, easier to see the wear, best rides!
    Yeh, that's what chain I ended up getting - LX chain (bought 2 this time so I'd have 1 ready when the first wears) along with the LX cassette. Now I got to find a good/hard/strong replacement middle chainring - using the one off my old RF Ride crankset that came with the Trance (kept it on for about 300 miles and then changed it for my older, heavier, stronger Deore set). Any suggestions? Like the checking over a longer distance than 1ft BT. Even if you only check over 2ft it makes a huge difference in how easily you see the stretch, even found out the HG53 I thought hadn't stretched was slightly stretched.
    One day your life will flash before your eyes, will it be worth watching??
    MTB Barbados
    My Phantom pics

  18. #18
    just along for the ride
    Reputation: Brown_Teeth's Avatar
    Join Date
    Jan 2004
    Posts
    3,037
    If you can stand the extra grams I'd go deore middle and small ring (both are steel) with your new chain, cassette, that will be your longest lasting solution albeit not the lightest. Simplest way to measure chain wear is make a 4' mark on the bench from a corner. Take an old spoke place it through one end of the chain (The end by the table end) so you can apply tension w/o having the chain move, if its more than 1/8 off its time to replace if you want max life out of your drivetrain.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Nov 2004
    Posts
    100

    Deore steel middle ring $10 bikeparts.com NM

    Deore steel middle ring $10 bikeparts.com NM

  20. #20
    mtbr member
    Reputation: disco's Avatar
    Join Date
    Jul 2004
    Posts
    120

    check chainline

    as a fellow Liquid owner who just replaced his entire drivetrain (Sram '06 980 cassette, Sram 970 chain, Truvativ rings) I can say it is a world of difference. Like a whole new bike.

    What my LBS noticed is that the chainline was off in the stock setup. BBspindle was a 113 and said it would be better with a 108 b/c the middle ring was not lining up where it should have (in the middle of the rear cassette) Trek did not spec this bike out correctly.

    my drivetrain had considerable wear but I was getting all the same problems as you were - chain jumping, skipping, etc. Bad chainline can cause these problems as well. Just another thing to look out for

  21. #21
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452
    Here are a few pics of the sad condition of my middle front chainring. I've replaced it now with a new one (Shimano LX 32t 104mm) and on a brief ride through the parking lot all seems great. Will be riding on my usual trail tomorrow evening so I'll report back of how it went under full on riding.
    Attached Images Attached Images

  22. #22
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    452
    Update: Did my full normal trail ride tonight. Bike works great!!!!! Not a single jump or skip or even attempt to jump down on the frt ring. Bike shifts cleanly and quickly up frt again too.

    Only issue I had was now the frt derailleur has some trouble getting the chain to the granny gear from the middle gear when under mild power or greater. This issue got better as my ride progressed however probably both due to me shifting better and the gear wearing in a bit.

    All in all, I'm happy its fixed with simply a new chain and middle ring replacement. Will keep an eye more sharply on my equipment from now on.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •