Optimum Di2 Setup

oblongomaculatus

Hi. Bought a Specialized Roubaix with Di2 about 3 months ago, and while I'm generally delighted with it, I suspect the rear mech could be set up better. Sometimes the shifting is so smooth you can't feel or hear it, but sometimes the chain drops onto the next sprocket with a real clatter. I know how to make the micro adjustments - hold the little button down until you get a red light, then press the shifters one way or the other, which adjusts 0.2mm per click. Experimentation has shown that the full range is 32 clicks from one end to the other. Obviously, at either extreme, the adjustment is way out, so the proper adjustment will be somewhere in the middle. The thing is, I've found there are several settings around the middle of the range where the shifting works fine - runs up and down all the sprockets with no hesitation when on the work stand - but it's not clear which one is the best. Logically there should be one setting which is the optimum.

I mentioned this to the shop when I took the bike in for its 6 week check, but I don't think the mechanic appreciated what I was getting at. I probably didn't explain too clearly, hope I've managed to here. Is it just a matter of micro adjustment, am I expecting too much of the system, or is there perhaps something wrong with my rear mech?

smidsy

oblongomaculatus wrote:

The thing is, I've found there are several settings around the middle of the range where the shifting works fine - runs up and down all the sprockets with no hesitation when on the work stand - but it's not clear which one is the best.

Seems to me you need to select the middle one of those and then micro adjust one way or the other when you get it out and about under load (as this tends to find the real setting needed).

oblongomaculatus

Thanks; I have tried making adjustments on the road, but the dilemma is the same: is the new setting better, worse or the same as the old one? It's hard to tell.

mpdouglas

In principle, your aiming for the setting where the centre line of the chain is sitting bang in line with the cog on the cassette. The gap between cogs on the cassette is slightly wider than the chain and hence there is a range of settings where things are properly in gear but perhaps not dead central to the cassette cog. If you've got a workshop stand, a torch and your eyes are a pretty good way of telling whether the gap from sides of the chain to the cogs either side of your current gear are identical or not. I might even be tempted to check it with feeler gauges if you want an exact answer (although you'll have to be gentle as the gauge itself could move the chain sideways on the current gear).

An alternative is to micro adjust in one direction until it starts making a noise to indicate it's trying to shift. I'd then micro adjust in the other direction until I get the same level of noise, counting the number of micro clicks needed to go from one to the other. If you half that number and then micro shift that amount, it should be dead centre between the two extremes.

oblongomaculatus

Thanks, those are two useful suggestions. I'll try the by-eye thing first. I do have a workstand, and my eyes are pretty good. I might also use a mangifying glass, we are talking about fractions of a mm here after all! If I can't see clearly enough I'll have a go at the other method.

I can't help thinking I'm being a bit fussy here, after all it is shifting reliably. On the other hand, it's an expensive bit of kit on an expensive bike, so perhaps it's not unreasonable to want it to work as well as it possibly can.

majormantra

Rarely in my experience is a hanger absolutely perfectly straight, so that will affect your shifting too. I think you may be being a little fussy, although I am sympathetic.

oblongomaculatus

Update: I have just had the bike on the workstand. Couldn't see clearly enough how central the chain was running due to variations in the shape and angle of the teeth, so tried the other method. After recounting the number of micro clicks across the full range I discovered that there are in fact 30, (not32) with my present setting 17 from the hub. By micro clicking towards the hub the chain began to make a noise - ie rubbing on the next sprocket at 13 clicks from the hub, and was really obviously noisy at 9. Moving back the other way, it became progressively quieter, as you would expect, as it reached 17, where it had been when I started. I continued in that direction until I started to get noise again, then moved back and forth in that area to find the quietest setting. As far as I can tell - and you have to listen really carefully - this is 20 clicks from the hub, or five out from the central point.I presume that being that far from the central point is due to my derailleur not being perfectly straight. It looks OK, but if each micro click is 0.2 mm this would mean it's only 1mm out, hard to tell visually. On the workstand shifting up and down the full range does seem a little smoother/quieter/faster though I haven't ridden it yet.

mallorcajeff

In the manual i have and i set mine up the same it says put in adjust mode then go left until it starts to make a noise and rub, then go four clicks away from the gear its touching. Works every time on my da 7900 di2