HELP: Change chain and get weird problem ?
01-09-08, 03:30 AM
#1
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HELP: Change chain and get weird problem ?
I have an old MTB bike 15-20 year old. Front 4 and back 5 speed.
What I have done:
1. Repaint the frame,
2. Replace shifters (SRAM MRX grip shifter),
3. Cassette are changed before a ~ 200Km.
After this changing everything was ok.
And yesterday I replace old chain (no-name very old and to strech) with new KMC (8 -speed).
On the all 3 big chain rings (30T, 38T and 48T) shifting is much better but shifting is impossible on the smaller chain ring (24T).
When is chain on the smallest ring (24T) on the repair stand everything is ok but on the road (under load when riding) the teeth on the next bigger chain ring (30T) catch the chain on the bottom of ring and the chain finish blocked between rings (24T and 30T).
What to do:
1. Replace only crank for standard MTB triple (but compatibility with old BB should be problem),
or
2. Replace crank and BB,
or
3. Replace chain,
or
Something else...
Please help!
And one more question:
Whold Deore crank (9 speed) work fine with 8-speed chain?
Best Regards,
PD.
What I have done:
1. Repaint the frame,
2. Replace shifters (SRAM MRX grip shifter),
3. Cassette are changed before a ~ 200Km.
After this changing everything was ok.
And yesterday I replace old chain (no-name very old and to strech) with new KMC (8 -speed).
On the all 3 big chain rings (30T, 38T and 48T) shifting is much better but shifting is impossible on the smaller chain ring (24T).
When is chain on the smallest ring (24T) on the repair stand everything is ok but on the road (under load when riding) the teeth on the next bigger chain ring (30T) catch the chain on the bottom of ring and the chain finish blocked between rings (24T and 30T).
What to do:
1. Replace only crank for standard MTB triple (but compatibility with old BB should be problem),
or
2. Replace crank and BB,
or
3. Replace chain,
or
Something else...
Please help!
And one more question:
Whold Deore crank (9 speed) work fine with 8-speed chain?
Best Regards,
PD.
01-09-08, 03:50 AM
#2
The Weird Beard
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I wish I had more to offer you other than the fact that I've never seen a 4-ring crankset before. I'm curious - can you tell what brand of bike this is/was? Also, heard (from my LBS wrench) it was a good idea to do the BB while you're changing the crankset. Is it possible the shifters you installed are indexed for three rings instead of four?
01-09-08, 05:12 AM
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I wish I had more to offer you other than the fact that I've never seen a 4-ring crankset before. I'm curious - can you tell what brand of bike this is/was? Also, heard (from my LBS wrench) it was a good idea to do the BB while you're changing the crankset. Is it possible the shifters you installed are indexed for three rings instead of four?
Brand of bike? I don't know but is made of steel and rigid. .)
PD.
01-09-08, 08:22 AM
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And yesterday I replace old chain (no-name very old and to strech) with new KMC (8 -speed).
On the all 3 big chain rings (30T, 38T and 48T) shifting is much better but shifting is impossible on the smaller chain ring (24T).
When is chain on the smallest ring (24T) on the repair stand everything is ok but on the road (under load when riding) the teeth on the next bigger chain ring (30T) catch the chain on the bottom of ring and the chain finish blocked between rings (24T and 30T).
On the all 3 big chain rings (30T, 38T and 48T) shifting is much better but shifting is impossible on the smaller chain ring (24T).
When is chain on the smallest ring (24T) on the repair stand everything is ok but on the road (under load when riding) the teeth on the next bigger chain ring (30T) catch the chain on the bottom of ring and the chain finish blocked between rings (24T and 30T).
https://abundantadventures.com/mt_plus.html
You might be able to space the inner 24 tooth ring inward a bit more. Otherwise you most certainly will need a new BB to go with a newer MTB triple crank set.
01-09-08, 12:47 PM
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It sounds like the FD doesn't have enough clearance on the inside and that walks the chain off the small ring. But why it would do that only with a new chain is a mystery.
Does it matter what rear gear you're in when the chain pulls off the 24T? The potential for cross-chaining must be horrendous with 4 up front.
Consider removing the 4th (24T) ring and adjusting for 3 rings.
Does it matter what rear gear you're in when the chain pulls off the 24T? The potential for cross-chaining must be horrendous with 4 up front.
Consider removing the 4th (24T) ring and adjusting for 3 rings.
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01-09-08, 02:57 PM
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I don't think that the problem is with FD because chain is stuck between 24T and 30T on the bottom side of rings.
I suppose that the problem is with the fact that the new chain is more flexible and when is on 24T ring also touching 30T ring. It happened only under pressure on pedal.
The crankset has no replaceable chainrings.
Maybe the solution is finding the way to move rings out for 2-3 mm from seat stay.
I suppose that the problem is with the fact that the new chain is more flexible and when is on 24T ring also touching 30T ring. It happened only under pressure on pedal.
The crankset has no replaceable chainrings.
Maybe the solution is finding the way to move rings out for 2-3 mm from seat stay.
