technical build question-road cassette with 135 spacing

[sfghbiker]

Hey all,
I am in the process of building up my new frame and am running into problems with chainline. What I want to do is run my 135 spaced "cross" frame (salsa la cruz) with a 10 speed dura ace drivetrain (12-27)with a fcr700 crank (what I have lying around.) I imagine this can be done as Salsa sells these frames with road drivetrains. the problem is my shifting sucks, specifically shifting into the smallest sprocket. No matter how much tinkering I do, I can't seem get the indexing down right and there is difficulty shifting into the small sprocket. Do I need to put a spacer behind my cassette to make this work? spacer somewhere else? anyone sell/build these and run into this?
thanks for your help.

[Ken Robb]

It sounds like your cogs are 2.5mm farther out than they would be on the 130mm spacing. Can you re-dish the wheel to get the cassette where it should be? Maybe a spacer behind the cassette? Longer bottom bracket to get the chainrings farther out?

[Peter P.]

Redishing the wheel as Ken Robb suggests won't do anything to change the position of the cassette so I wouldn't bother going that route.

Is the derailleur old and possibly bent?

Is it possible the derailleur hanger is bent or the rear end is out of alignment? I just took delivery of a new custom frame and found the derailleur hanger 12mm out of alignment when 4mm is the max allowed. I shipped the frame back to the builder and he said the rear end was 3-4mm out of alignment. My point is, this could be your problem.

Spacers aren't the solution; you've got a problem elsewhere. You sure the cable is not routed incorrectly or is binding somewhere?

[paulrad9]

I may be missing something, but I don't think re-dishing will help as it will move the rim, not the cassette.

Are you trying to shift the 34/39 into the small sprocket? If so, this won't work with many Shimano 10 speed setups. Per instructions, the last two to three small sprockets are typically not accessible with the small chainring

[sfghbiker]

thanks everyone. I guess it is possible the hanger is bent. Not sure how I check for this short of an alignment table. As to the derailleur malfunctioning, I guess this is also a possibility though I transferred this drivetrain from my IF road bike where it was functioning fine and just put new cables on. I suppose that the cables may be binding and this could be the problem. would a binding cable have the most impact with small sprocket shifting? I am also aware the the smallest cog is really the domain of only the 50 tooth chainring so have been toying around with lining this up only on the big ring. perhaps a need a 2.5mm spacer on my my driveside crank arm?

[nahtnoj]

I didn't read what your frame is made out of. If steel, your LBS should have a Park tool called a DAG-1 which they can use to measure alignment of the tab. It uses your wheel as a reference - pretty neat tool.

[C50]

A few things, what type of hub is the cassette going on? I assume it is a hub with 135mm spacing also. If that is the case and you have put the very thin spacer needed to go on the hub body first for 10 speed cassettes then check the cable attachment at the rear derailleur. It is quite possible from the description of the problem that the little tab at the pinch bolt is in the wrong position. The tab should not be on the side where the cable gets attached but turned 90 degrees from there. Check this just to make sure but it could cause shifting problems in the bottom cogs.

[RPS]

thanks everyone. I guess it is possible the hanger is bent. Not sure how I check for this short of an alignment table. As to the derailleur malfunctioning, I guess this is also a possibility though I transferred this drivetrain from my IF road bike where it was functioning fine and just put new cables on. I suppose that the cables may be binding and this could be the problem. would a binding cable have the most impact with small sprocket shifting? I am also aware the the smallest cog is really the domain of only the 50 tooth chainring so have been toying around with lining this up only on the big ring. perhaps a need a 2.5mm spacer on my my driveside crank arm?Most likely.

Cable tension is reduced as you move towards the smallest sprocket, and if you have excessive friction in the cable, it may not allow the derailleur to move freely to the smallest cog. I'm not saying that's your problem....just answering your question.

Spacers to correct for chainline are not the solution in my opinion since it should work just fine if it is set up right and everything is working correctly. My Co-Motion tandem has 135MM MTB wheel spacing with dual road chainrings and it works great. The only limitation is that there is a slight bias for not being able to cross the chain as far from the small ring towards the small cogs -- as you'd expect from the chainline numbers. On the other hand it makes it easier for the big ring to hit all the cogs without crossing the chain as far.

If you started adjusting the derailleur by setting cable tension while on the smallest cog and it then doesn't return back to that spot after you shift up and down, I'd look again at cable friction. Make sure nothing is hanging up.

[Ken Robb]

[QUOTE=RPS]Most likely.

Spacers to correct for chainline are not the solution in my opinion since it should work just fine if it is set up right and everything is working correctly. My Co-Motion tandem has 135MM MTB wheel spacing with dual road chainrings and it works great.

I read that he is squeezing a 135mm wheel into a 130mm frame and thought that was what was causing a misalignment that becomes critical when he shifts to the smallest cogs which are farthest out from the ideally-centered location for a good chainline.

On some Rivendell models the rear spacing is 132.5mm to allow the use of 130 and 135mm hubs. Some people have tried this on other bikes and found the shifting to be less than wonderful. I think the different results may be due to the Riv bikes having chainstays of 44.5-45.5 mm rather than the 40-41 mm stays used on racier bikes. I have several Rivs like this and they all shift perfectly with triple cranks. I have read complaints about shift quality of triples from riders with racy bikes with short chainstays so I think long stays make acute chain angles shift better but being off by 5mm on this bike is just too much to overcome with the geos it has.

[RPS]

I read that he is squeezing a 135mm wheel into a 130mm frame and thought that was what was causing a misalignment that becomes critical when he shifts to the smallest cogs which are farthest out from the ideally-centered location for a good chainline.Ken, I read the OP differently.

I agree that if a person tried to switch between 130 and 135 wheels without doing any adjustments then nothing is going to work correctly, but that’s not what I think he is doing. The fact that he has spent time “tinkering” with adjustments to make it work suggests to me that he’s tried to adjust the cable for that particular combination of parts.

Spreading or compressing a frame whether 130, 132.5 or 135 shouldn’t matter to the cogs, just to the frame itself. The only thing that’s important is where the cogs end up and as long as the frame flexes equally on both sides then original frame spacing is irrelevant ATMO. Unless I’m wrong.

[Ken Robb]

beats me. I have a pal who swaps his 9 spd Ultegra rear derailer/cassette for and XT derailer and mtn. cassette for trips to the mountains and it always wiorks fine so I was focused on the idea of a mismatch between frame and axle size.

[RPS]

beats me. I have a pal who swaps his 9 spd Ultegra rear derailer/cassette for and XT derailer and mtn. cassette for trips to the mountains and it always wiorks fine so I was focused on the idea of a mismatch between frame and axle size.
Ken, I’ll even correct myself and say that “sometimes” changing from 130 to 135 wheel by spreading the frame may even work fine because the derailleur is moved right along with the cogs (it doesn't have to not work as I stated above). As long as the dimension from the outer cog to the derailleur remains the same it may work without adjustments – much like changing to a different rear wheel during a race. It may require a little on-the-go tweaking but it may not.

As to your friend, if he changes derailleur to XT then he’s having to adjust the cable to the new parts. And that should take care of it as long as he does it right.