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A while back I bought an old dynatech bike, one I’d always lusted after as a kid. It needed some tlc and as such I thought it deserved some nicer parts.
duraace 7700 looks like bike jewelry, so I picked up a pair of brake calipers and a rear mech. After faffing around a bit the calipers now work great, which leads me to the rear mech
the issue is that the bike has a six speed cassette. Dura ace 7700 is 9 speed. Not a problem I thought, the indexing all happens at the down tube shifters (also 6 speed). Right enough in the small ring the shifting is great, but when it comes to the big ring it’s a disaster.
basically the chain angle from the biggest 3 sprockets means the chain (which is 8 speed as I was assured that would work fine on a 6 speed block) rubs against the mech cage creating a horrific grinding noise
i must admit I’d never thought about the fact a 9 speed mech wouldn’t be able to run an 8 speed chain.
so my question is, should this combo work, and I’ve set it up wrongly, or is the chain just too wide for that mech. And if so will a 9 speed chain work on a 6 speed block
the easiest option is to source a set of 9 speed shifters and matching cassette, but that’s really going to blow the budget of this already massively over budget ‘budget build’. I’m not even sure my rear wheel will take a 9 speed cassette (which I assume is a freewheel).
I’ve built dozens of modern bikes using components that are meant to work together, but have no idea with this retro mish mash
any help would be greatly appreciated
thanks
Will the shifting inserts from nine speed bar ends work in the six speed shifters? Have you confirmed nine speed is fine using friction mode and the existing shifters? I’d be tempted with that first and could dig out said bar ends if you need them.
will a 9 speed chain work on a 6 speed block
the easiest option is to source a set of 9 speed shifters and matching cassette,
The easiest option might be to try a 9 speed chain?
the easiest option is to source a set of 9 speed shifters and matching cassette, but that’s really going to blow the budget of this already massively over budget ‘budget build’. I’m not even sure my rear wheel will take a 9 speed cassette (which I assume is a freewheel)
You'd need a new wheel as well.
I doubt I’ll be able to bodge the shifters
however….
I don’t have a 9 speed chain but do have an old 11 speed hanging about. I thought there is no way this will work, and it doesn’t. But the issue is actually the same. The 11 speed chain works perfectly in the small ring, but as soon as we move to the big ring the angle throws the chain off the rear lower jockey wheel, causing the chain to rub against the cage
so it appears the issue is with maybe the second hand mech I bought, even though it does look pristine!
to further add confusion to the issue, when I back pedal there is no rubbing and the chain stays in the rear jockey, even at the most extreme chain line. Jockeys looks reasonably new and spin freely. I’m stumped!! Maybe swap the jockeys and see what happens? Top one retains the chain just fine!
The chainline can’t be the issue, as it works fine with the crappy old 6 speed mech it came with (which tbf was perfectly adequate and I may reluctantly need to return to)
Could be the bb axel is too long giving a bad chain line
For info.
6, 7, and 8 speed chains are the same width - and the lateral distance the chain has to across in order to shift up or down the cassette is the same. Each time the 'speed' increased from 6 to 7 to 8 the freehub body got longer by 1 sprocket (and the driveside flange moved inwards the same amount)
When 9 speed came along, they jammed the 9 rear sprockets into the space previously taken by 8. Ie the same freehub can take 8 or 9 speed cassettes.
BUT - the chain got correspondingly narrower to fit on the now narrower spaced sprockets at 9 speed.
Then the front mech got narrower too, as otherwise it won't shift as well (because the chain is narrower).
Also... when backpedalling the chain droops a bit at the top, whereas it's pulled tight when pedalling forward. That can make the difference on where it contacts the side plates of the front mech (see the front mech side plates are pressed / have wider and narrower bits)
So why does the 11 speed chain work fine on the 6 speed freewheel when in the small chainring?
is there anything I can do here , I’m not going to replace the rear wheel to accommodate a 9 speed freehub. Back to the old rear mech my only option?
Right.. just swapped the rear jockey wheel to an 11 speed from a rear mech I had spare and it no longer jumps!
it’s still a bit rumbly however, but I think that may because the jockey seems a bit wide for the mech. So I need a jockey wheel the same width as a 9 speed, but with the tooth profile of an 11 speed
the jockey wheel is defo the issue..
🤔
edit
@scotsroutes probably nailed it in the 2nd reply. Rather than source an oddly shaped jockey wheel, i assume that if an 11 speed chain fits then a 9 speed chain will also work, and that will gel perfectly with the existing jockey wheel..unless of course the 9 speed jockey I have is goosed. In which case should be easy enough to source a replacement