DA shifting compatibility

[Tandem Rider]

Heck, other than different cranks, that's exactly what we use on one of our tandems, it works great. I would check the hanger if it's rear problems. I have had issues with that in the past. Anytime something doesn't shift right with all the "normal" boxes checked look at the alignments, including the front, I've had a bent frame cause front shifting problems.

[tjg]

I’m questioning the rear derailleur. The B tension bolt assembly looks cracked and I’m not able to adjust properly. That reminded me that I had a MTB crash landing on that derailleur (different bike) some years ago. I picked up a nice same model XTR with a mid cage for a good price last night. I’ll figure out how to check my hanger alignment too, but I have a feeling the “new” RD may solve it.

I appreciate all the advice. If I still have issues, I’ll have a good check list to continue to troubleshoot.

[dddd]

Originally Posted by tjg

...***I had forgotten that my front derailleur is a 7400. Would this be the cause of the less than precise front shifting more than the crankset?

74xx front AND rear derailers have their uniquely higher cage-to-cable travel ratio, or actuation ratio.

The only problem using a 74xx front derailer is that with the setup correctly adcjusted for best shifting and chain control, there will be an excess of cable slack when using the small chainring. This of course applies only to use with an indexing front shifter that is non-74xx.
Also the spring will feel slightly stiffer.

The 74xx front derailer was also never intended to handle more than a 14t jump between chainrings, but should be ok in this regard imo.

Generally, it is with triple front derailers that the tooth-count jump from middle to big rings is precisely designed into the shape of the cage and shouldn't be changed in either direction out of specification.

Shimano 9s chain is by far your best bet for more immediate upshifts in front. This is measurable!

[tjg]

So, I bought a nice XTR 9 speed and a DA FD-7700 front derailleur for good prices. I have my nearly new Shimano chain that I took off recently (i don’t remember the model but is DA level).

I’ll check hanger alignment.

This is all on my Kirk MRB which is getting the most miles by far.

The Sugino compact crankset was originally intended to be short term, but have stayed on the bike for several years now.
New question. I’ve been looking at White Industries and Rene Herse cranks because of the distinctive “look” each will give my bike. Any opinions on function/performance of either or is finding a nice DA my best bet to continue to improve current drivetrain (or are there others to consider that are even better)? I really like compacts though.

[PacNW2Ford]

I would recommend a CX70 front derailleur. I am running one with DA bar-ends on a 9-speed setup with a 48-34 Sugino XD crankset and Shimano chain. Front shifts are like a light switch, best shifting of all my bikes and I have a lot of bikes. If it matters, this bike is also running a DA7800 rear derailleur.

[tjg]

I replaced my broken RD with an excellent 9 speed XTR mid-cage. Other than shortening the current (SRAM) chain, all else stayed the same.

As I shift from smaller cogs to larger cogs, it skips position #2 (32t). I am able to adjust it to skip position #3 instead, but I can’t get it to not skip either #2 or 3. It shifts fine shifting from large (34t) toward small (11t).

What’s the logical next step?

[dddd]

It sounds like the B-tension screw might need to be tightened a little, there is supposed to be some gap so that the shift motion at the top pulley isn't too forceful as the shifter overshifts sightly with each shift to a larger cog.

If the problem seems to change when a different chainring is used, this might be a case of the cage rotating off-axis with the rear axle (i.e. a bent hanger).

As for cranksets, I sure wouldn't use a modern Shimano road crankset on a 130mm-width frame if I could avoid it. The chainline is just too far out there for my tastes and there is no fix for this.
This seems to have gotten worse over the last few years as the disc-braked 135mm frames seem to be what these cranksets are being designed for, and I dare say that the chainline seems a bit excessive even with them.

Unless you like having to downshift off of your big ring early to avoid severe cross-chain noise and wear, I would go with an older-school crank with a shorter chainline.

[tjg]

Thank you for everyone's input. It seems as though I had 2 things happening, a damaged RD and a slightly torqued hanger. I haven’t done an extensive test ride yet, but on the stand and quick ride, all seems right and crisp again. I feel like I have gained a great deal of new information and knowledge from all this.