Dura Ace SIS shifter woes and in a further funk.

[bugloss]

Groanings.....

Continuing on my theme of Dura Ace woes, I now have an issue with the SIS 8 speed down tube shifters.......

My set up is a 7402 Dura Ace rear derailleur, HG narrow chain, HG rear Dura Ace 8 speed cassette on an 8 speed Dura Ace SIS hub. Is this combination correct for SIS changing heaven.

My problem is that it skips like hell. When I get it to SIS on the rear it skips over 7 on the way up but lands on it on the way down and when climbing it skips 3-2 like a beast.

Is this a known issue or am I missing a trick.

Yours,
Bugloss

 

[hamster]

Sounds like dirty cables and outers. Replace both and then take it from there. The fact it is inconsistent between up and down the cassette suggests the cable is sticking.

There was a funny series of early indexed Dura Ace that took a different pull per click - yours might be it, IIRC there is something about it on the Shimergo section on the CTC site.

 

[bugloss]

Re:

Thanks for the reply. They are down tube shifters and the only cable outer is from the chain stay nipple thing to the derailleur, cables are new.

Hmmmmm....

 

[bugloss]

Could the difference be in the chain. At the moment there isa HG narrow chain stamped ED on it. I'm assuming this is a HD70 chain, as the HG40 chain I have is stamped HG narrow LD.

Anybody know the difference between the two?

 

[foz]

your da parts are the ones that have a different cable pull, but you only need to match the shifters and rear mech, which you have so that's not the problem. Try cleaning or changing the cables and outers, check the rear hanger alignment too. Are the sprockets and/or chain worn?

 

[stringfellow1946]

Make sure the rear outer casing is SIS & NOT a brake cable outer.
If thats ok rear gear hanger alignement
Then the Bottom bracket cable guide. Make sure its the Shimano one & NOT some cheep plastic one. This particular part causes no end of shifting problems like the ones you describe.

 

[bugloss]

Re:

Thanks for the suggestions.......

An Update.

Cables good and casing good SIS. I've managed to cure the skipping from No. 2/3 by shortening the cable outer by 2", which I was going to do anyway, but it still skips over No. 7 on up and down.

It stays in the others when going up hill, which is a big bonus.

The front inner chain ring needs replacing as it's worn but I would imagine this wouldn't make much difference to No. 7 on the back.

 

[TGR]

Good evening,

I have an interest in this. A question - would the BB length affect movement?

Also, my neighbour had a similar problem last year and it was a bent hanger.

Richard

 

[hamster]

BB length is irrelevant. I suspect it's dirty cabling - down tube levers are the best for clean frictionless cable runs, but it might be something silly like a kink, burr or broken strand on the cable / outer.

When you say skipping, are you sure it is jumping gear and not just skipping cogs due to worn chain / cogs? Have you checked the chain with a chain checker / ruler?

 

[bugloss]

I think it's been cold set from 126-130mm to make room for the 8 speed hub and the dropout screws are at different depths when the wheel is straight, so the hanger may not be square with it on the x axis.

The rear derailleur is vertical though. Strange it goes over No.7 and not the others. I'll have a look at the cassette/ chain/ lg. rings. Cables on very good condition as is the cable housing at the rear derailleur.