The 'mechanical numpty needs some help please' thread...
Discussion
So, my bike has started throwing a fit in the middle cogs of the sprocket - and generally when going down a gear. It was fine yesterday, but today it's really unhappy. I've checked for obstruction, it's a new sprocket, new chain and I'm out of ideas. Help please! (I think it's Shimano SRAM on a Boardman Team FS).
Starting with the absolute easiest thing you can do tighten the cable a tiny bit at the barrel adjuster on the rear mech. That'll be by turning it anti clockwise. Just do small increments, maybe a quarter turn at a time.
Have a few goes and that'll hopefully sort it. Cables stretch a small amount over time and can mess up the indexing. If that doesn't sort it you're into setting it up again. I've long found that if it isn't working it's best to just set it up again from scratch. Very easy to do, you'll just need an hex key for the cable clamp (5mm usually), maybe some pliers to hold the cable tight while you tighten it and a screwdriver to adjust the limit screws.
Park do some good guides on all things mechanical and SRAM and Shimano both have their manuals available online.
Here's the Park one for rear derailleurs.
http://www.parktool.com/blog/repair-help/rear-dera...
Have a few goes and that'll hopefully sort it. Cables stretch a small amount over time and can mess up the indexing. If that doesn't sort it you're into setting it up again. I've long found that if it isn't working it's best to just set it up again from scratch. Very easy to do, you'll just need an hex key for the cable clamp (5mm usually), maybe some pliers to hold the cable tight while you tighten it and a screwdriver to adjust the limit screws.
Park do some good guides on all things mechanical and SRAM and Shimano both have their manuals available online.
Here's the Park one for rear derailleurs.
http://www.parktool.com/blog/repair-help/rear-dera...
I used youtube for gear setup. Dead easy once you get it.
You say it's chucking a wobbly in the middle - so imo change to big / small, turn the cranks and try to go to an easier gear on the back. If it doesn't change instantly, turn the barrel adjuster anticlockwise 1/4 turn.
If it foes change, keep going up till you get a bother. Again, 1/4 turn at a time. If you get all the way to big/ small and it's changing fine, go to small / big and change down. If it doesn't want to change to a harder gear, do clockwise 1/4 turn.
Nb - you'll always have noisy nastyness on big / small and small / big. However, they should still select fine.
You say it's chucking a wobbly in the middle - so imo change to big / small, turn the cranks and try to go to an easier gear on the back. If it doesn't change instantly, turn the barrel adjuster anticlockwise 1/4 turn.
If it foes change, keep going up till you get a bother. Again, 1/4 turn at a time. If you get all the way to big/ small and it's changing fine, go to small / big and change down. If it doesn't want to change to a harder gear, do clockwise 1/4 turn.
Nb - you'll always have noisy nastyness on big / small and small / big. However, they should still select fine.
For rear mech adjustments, the easiest way to remember which way to adjust that I find (and teach others) is to look down on the mech from the top of the bike, and then turn the barrel adjuster a quarter of a turn in the direction that the chain is struggling to go when you are shifting gears.
I.e., if when shifting into a bigger cog, the chain skips and doesn't shift cleanly, turn the barrel adjuster in that direction as you look at it (anti-clockwise). Try again, and repeat if necessary.
And vice versa if struggling to shift down to smaller cogs.
Mech limit screws should be set up beforehand however.
If you are having problems with it shifting cleanly in both directions, check the gear cables - lube your outers (oo-er) and check the ends for obstructions that will make them drag. If they're all rusted and gammy, replace.
I.e., if when shifting into a bigger cog, the chain skips and doesn't shift cleanly, turn the barrel adjuster in that direction as you look at it (anti-clockwise). Try again, and repeat if necessary.
And vice versa if struggling to shift down to smaller cogs.
Mech limit screws should be set up beforehand however.
If you are having problems with it shifting cleanly in both directions, check the gear cables - lube your outers (oo-er) and check the ends for obstructions that will make them drag. If they're all rusted and gammy, replace.
Edited by ccr32 on Tuesday 22 July 12:49
Just so you know what the tutorials are on about, it's middle sprockets on your cassette, and your rear mech (derraileur) will be either Shimano or SRAM.
When setting your mech up, always get a good view from directly behind, you'll see how it's all supposed to line up and will become clear.
When setting your mech up, always get a good view from directly behind, you'll see how it's all supposed to line up and will become clear.
ccr32 said:
For rear mech adjustments, the easiest way to remember which way to adjust that I find (and teach others) is to look down on the mech from the top of the bike, and then turn the barrel adjuster a quarter of a turn in the direction that the chain is struggling to go when you are shifting gears.
I.e., if when shifting into a bigger cog, the chain skips and doesn't shift cleanly, turn the barrel adjuster in that direction as you look at it (anti-clockwise). Try again, and repeat if necessary.
And vice versa if struggling to shift down to smaller cogs.
Mech limit screws should be set up beforehand however.
If you are having problems with it shifting cleanly in both directions, check the gear cables - lube your outers (oo-er) and check the ends for obstructions that will make them drag. If they're all rusted and gammy, replace.
Good advice that!I.e., if when shifting into a bigger cog, the chain skips and doesn't shift cleanly, turn the barrel adjuster in that direction as you look at it (anti-clockwise). Try again, and repeat if necessary.
And vice versa if struggling to shift down to smaller cogs.
Mech limit screws should be set up beforehand however.
If you are having problems with it shifting cleanly in both directions, check the gear cables - lube your outers (oo-er) and check the ends for obstructions that will make them drag. If they're all rusted and gammy, replace.
Edited by ccr32 on Tuesday 22 July 12:49
Steve
FFS. It's not fixed - I just chase the jump up and down the cassette. No happy medium. So, with a new chain, new rear derailer, new cassette sprocket thing, I'm out of ideas. Could the mounting brackets be out of whack?
Also.... four punctures in four rides. New inners across the board - what else should I check? I've done the rims, seen for anything else mechanical. The tyre is looking a bit second hand now, so I'll replace that. Is 'Slime' worth it? I'm not a small lump, so I can imagine the rear wheel takes a battering generally, but I'm not jumping it, pinching rocks or anything else like that....
(At this rate I'm going to give myself an early Xmas present...)
Thanks!
Also.... four punctures in four rides. New inners across the board - what else should I check? I've done the rims, seen for anything else mechanical. The tyre is looking a bit second hand now, so I'll replace that. Is 'Slime' worth it? I'm not a small lump, so I can imagine the rear wheel takes a battering generally, but I'm not jumping it, pinching rocks or anything else like that....
(At this rate I'm going to give myself an early Xmas present...)
Thanks!
For the ouncture issue - have they been in the same position? If so, REALLY check the tyre over. I had a small cut in a tyre once and it just kept "eating" through the inner - new tyre in the end. Even the smallest bit of debris sticking through a tyre / misspositioned rim tape etc etc will cause repeated punctures.
Oh, and the deralliur issue - is it always whilst changing in 1 direction, or is it both up and down? If it's only when taking tension off, it could be gunky cable syndrome?
Oh, and the deralliur issue - is it always whilst changing in 1 direction, or is it both up and down? If it's only when taking tension off, it could be gunky cable syndrome?
Get your hanger assessed for trueness. I adjusted my own gears and managed to get either the highest OR the lowest ratios to index but never both. Took the bike to Cult Cycles in Earlswood and the first thing he did was to unscrew my mech, and check the hanger, which was significantly out of true.
Once straigtened, he got them clocking through the whole range with rifle-bolt accuracy. Very satisfying.
Once straigtened, he got them clocking through the whole range with rifle-bolt accuracy. Very satisfying.
Edited by Watchman on Thursday 31st July 12:56
Watchman said:
Get your hanger assessed for trueness. I adjusted my own gears and managed to get either the highest OR the lowest ratios to index but never both. Took the bike to Cult Cycles in Earlswood and the first thing he did was to unscrew my mech, and check the hanger, which was significantly out of true.
Once straigtened, he got them clocking through the whole range with rifle-bolt accuracy. Very satisfying.
Agree with this - if the mech hanger is twisted slightly it is impossible to get it working properly at both ends of the cassette (other than the top and bottom gears which rely on the stops for position). This is the tool to do it, cheaper versions are available:Once straigtened, he got them clocking through the whole range with rifle-bolt accuracy. Very satisfying.
Edited by Watchman on Thursday 31st July 12:56
http://www.parktool.com/product/derailleur-hanger-...
Don1 said:
For the love of God.... looks like both of my disks are now warped as well. ARGH!
It's really not your week is it?If it helps I took my summer road bike apart, fitted a new chain, stripped and cleaned the rear derailleur.
Its soooo shiny but also utterly stuffed. Wont index at all. I suspect the rear mech was happy gunked up, but is now very unhappy clean. Also I may have over shortened the chain...
But hey it looks pretty and it wont get dirty again like that.
Professional intervention needed before ridelondon!
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