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Post by cusqueno on Apr 25, 2015 20:29:59 GMT
Perhaps someone can suggest a solution to something that has been puzzling me for some time. My Aerospace 400 frame is kitted out with first gen Dura Ace components. So there is a Crane RD, DA crank set and rings and DA FD. The wheels have Viscount hubs and there is a six speed Ultra Glide block. Trouble is, I find it very difficult to get into top gear when the chain is on the largest chain wheel. It works fine on the smaller chain wheel.
In general, the chain line looks ok and I would have thought that changing into top from the largest chain wheel would be easier, the chain line being better? If I adjust the dérailleur so that I can get top (actually quite difficult), then I risk the chain coming off when selecting top from the smaller chain wheel.
The bottom bracket is DA, but not first gen, and I cannot recall how long it is. Block is 14-24 and it's a usual 53-42 chain set so I'm not asking it to do anything very ambitious. Any ideas gratefully received, it's a bit of a bore to have to change right down at every traffic light.
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Post by Stella on Apr 26, 2015 9:52:32 GMT
Hey, John. It shouldn't pose such a problem with friction shifting, unless the chain line is off severely. When I encounter such a problem I go by process of elimination: Check if the hanger's straight or bent. There's a special tool for that (I'm sure you know that already), and it often detects what the eyes mistake for a 'everything looks fine'. In most cases, straightening it solves the problem. You did the limit screw already, then there's only cables to consider. If they're older ones they seize up and replacing them can solve the issue. Cable tension can be a factor, too. My wild guess is a bent derailleur hanger. Hope this helps. |
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Post by raymondo on Apr 26, 2015 22:02:22 GMT
Having messed about with deraileur fitting a double skip tooth free wheel (Inot an easy two days) I found slack in the derailleur mechanisms detremental to complete gear selection. I had to complete the whole job by junking what looked like a good usable Shimano 600 long cage in favour of a brand new cheap Sunrace option. It worked, and comparing the Altus i took off with the Shimano i brought second hand, plus the sun race you could see or feel the problem. Even with a new hanger it would not work. I would have had to bend the hanger to get it to go into all gears. It just flapped about instead of working as it should.
My view is the derailleur is the most engineed part on a cycle so they have the potencial to give the most greif and the most likely cause. Swap the derailleur if you can just to elliminate a possible cause.
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Post by velocipete on Apr 27, 2015 6:04:51 GMT
Good advice there Raymondo. When I worked full time as a bike mechanic,I found that it wasn't always the mech hanger that was bent,but the lower part of the mech itself.
This was usually caused by dropping the bike gears side down,or bad storage.Some bike racks will happliy knacker a rear mech with ease.You can "adjust" the mech by a careful
application of brute force! Sometimes the jockey wheels will be out of line causing simlilar gear selection problems.This can also be "adjusted" out.
Hope this helps.
Cheers,
Pete.
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Post by Stella on Apr 27, 2015 10:26:35 GMT
Actually, that's good advice, Pete. Just yesterday I encountered a bent and twisted derailleur (SIS). I've bent back rear mechs in the past when the customer really didn't have any money to replace it, just to sort of get it back to working. My vice, my best friend. :-)
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Post by cusqueno on Sept 29, 2015 20:24:06 GMT
An interesting ps to this story. I put some new(er) wheels on, with a seven speed block and, with the minimum of adjustment, all 14 gears work fine. No need to be d anything. The wheels have Mavic hubs and Ambrosio Durex Aero rims. Interestingly they are two-cross front & rear with 32 spokes on the front and 28 on the rear. (Yes I have got that right. ) |
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