So all of my gears work apart from the rear 26..?

vectra0

Hi All

Im a little bit stumped with this one.... if any one could shed some light it would be much appreciated. :idea:

So ive just upgraded to brand new DA9000. Im running Reynolds strike wheels with a 11-26 SRAM cassette.
Everything seemed to be straight forward... except I cant get on to the rear cassettes largest cog (26) when i am in the big (52) front chainring....
It works fine in the small (36) chainring, shifts up and down crisply, then when I go to the 52 it runs up the block fine until the last cog!??
I can fine tune the barrel adjusters and it will eventually jump up, but then it wont drop back down to the 11when I dump the gears again...?
I can't see how it all works fine in the small front chainring, but then does not work in the big front chainring.... It can clearly shift up there fine.
Any ideas would be fantastic
cheers all :?: :?: :?:

dabber

Perhaps the Low Limit Adjustment Screw needs adjusting a little?

arlowood

Maybe your chain is a bit too short.

Running big/big will have the chain stretched to it's limit and the rear derailleur also pulled out almost straight. If the top guide pulley gets too close to the 26 cog it may foul and prevent the smooth shifting.

Sometimes tweaking the B-screw can solve that issue but maybe a longer chain length could be the answer

vectra0

So limit screws are where they need to be when on the small front ring. Any more and it jumps off the top.
I noticed when i slackened the B screw right off it will go into the top cog, but this is with absolutely no tension on it at all on the mech. Which is not ideal right?? The chain didn't seem to be too small. And there is plenty of pull on the mech still...

Rightarmbad

Bent hanger.
Possibly too short chain as well.

vectra0

I've just had it down to the LBS and they checked the mech hanger on the jig thing... its fine. They couldn't work it out either and they said chain length looks fine....
I'm going to add a link to see what happens, other than that I'm stumped. Possibly a longer cable sleeve into the rear mech... even though I'm using the dura ace cable kit

Bobbinogs

ermm, did the LBS mention that you shouldn't be trying to get the bike into top/bottom anyway? Its a bit like going to the doctors and saying "It hurts when I do this", the answer is "Don't do it".

What you are trying to do is cross the chain and if you want to know why that is bad idea then just look at the chain line when you are in 52/23.

I suspect your problem is down to chain length but you should not be adding links in unless they are the KMC ones (with the inner links used from any chain). The majority of link pins (Shimano for instance) are not made to be removed and replaced. The pins have a mushroom shaped end that deforms on removal.

There are some good online chain length tools, old school is to wrap the chain around big/big (without the RD) and add two links.

vectra0

Cheers all.
So I've had it in to two separate mechanics today. (One of them a giant store) Both unable to fix it or know what is going. Not a gear I would ever really ride with that much cross chain but still something that is achievable on every other bike I've ever seen/worked on. I have replaced all the cables and housings. The bike has internal cable routing via a sheath which runs all the way to the rear mech. The only thing we can come up with is that due to the frame angles etc it's making the final shift spongy... I didn't want to cut the sheath away as I don't want the frame rattle from the cables.... this may be the only option... a bit shit really for a such a high end product....

Guernsey Donkey

I think what we have here is the cycling equivalent of a PEBKAC (IT experts will know!).

Maybe a PEBSAS?

vectra0

I'm not sure coming on here to put people down with a genuine problem is really what the forum is for thanks. If you have no advice you don't have to say anything, stop trolling with insults, go and join a Google forum. Totally un called for....

Bobbinogs

I still don't get why you are trying to fix something that shouldn't be done? Why bother wasting your time and the mechanics' time when the fact that you can't cross the chain is probably a good thing (bit like a dork disc but then we all remove that, eh!). Just live with it for now. When you need to replace the chain, cut it a link or two longer and see if the problem goes away, if not, just cut it the right size and forget the whole thing.

keef66

It's the internet; don't take offence too easily. I couldn't even be arsed to google donkey's acronyms.

It occurs to me that in that extreme big - big combo, both cables are under maximum tension. Is there any way they are interfering with each other eg in the downtube? I'd be the first to admit I have no idea about internally routed cables; all the bikes I deal with have them all on the outside. But I have come across bikes with cables crossed beneath the downtube producing something similar.

vectra0

Yeah thanks, that is the only option at the moment....
Still a £900 groupset should manage what a £300 groupset can do.... irrelevant of whether you need it to or not....
It's a handy gear for when racing. No body appreciates a small ring gear change, mid pack up a sharp hill.... causes accidents...
If I'd known the internal cabling would have caused such issues I'd have probably stayed well clear :-)
I'll let you know if I get it sorted. Cheers

g00se

Is it a stock build - or a custom one? have you tried a different rear wheel with the same cassette or the different rear wheel with a different cassette - it may help eliminate the issue?

As others have said, you shouldn't normally cross chain, but there shouldn't be a technical reason it shouldn't work.

It may be the chain line is outside of 9000 specification. That is, the 26 is too far inboard compared to the big chain-ring?

Also, what size is the frame and specifically, what is the chainstay length as a short chainstay will compound chain-line out-of-spec issues.

vectra0

Hi Thanks
It's a custom build. The guy who sold the frame was running DA Di2, I chose mechanical DA. Size m52 and chainstay is 40.5cm
I've tried another wheel: DA c24 with an 11-28 ultegra cassette. Same problem. Works fine in the small chainring but couldn't hit the top in the large chainring. The chain line is very angled... maybe a spacer behind the cassette...? As it only just doesn't reach. Not sure if the cassette will sit on the free hub properly though....

vectra0

I'd add picture but I can't resize to 250ks :-)

g00se

40.5cm is the minimum chainstay length for Shimano with standard hubs - it's not a 135mm disc hub is it?

Assuming it isn't, could there be an issue with the chainset sitting too far outboard? Could it be the BB was built up with incorrect spacers etc?

If you look from the rear of the bike, in the plane of the gap right between the middle of the two chainrings, it should be in line with the 6th sprocket (middle one) - or possibly the cassette could be a coupe of mm inboard of that. If the cassette seems a lot further inboard, that could well be the issue and you have the chainset spaced too far out.

More details here:

http://www.parktool.com/blog/repair-help/chainline-concepts


For a photo - upload it free to somewhere like http://postimage.org/
then link to it.

vectra0

Ah goose that's brilliant. It makes perfect sense. I will take a good look at it all tonight when I get in from work .
It's a standard hub. And I'm not sure about the BB as it was already installed on the frame....
Thanks

6wheels

If goose's idea doesn't help, try running an outer from shifter to the rear mech, that should help to isolate the problem.

I agree with you, paid for 22 spd , that's what you should have.

vectra0

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19774778#p19774778]6wheels[/url] wrote:

If goose's idea doesn't help, try running an outer from shifter to the rear mech, that should help to isolate the problem.

I agree with you, paid for 22 spd , that's what you should have.

Very good shout. Thanks