DA triple - will this work

dazman said:

Hi,

I'm doing the TDF Etape (200K in the Pyrenees) in a couple of weeks and I ordered a DA triple, together with triple shifters and front derailleur just in case I run out of gas on the final climbs.

Has anyone had success with a 12-27 cassette and 52-30 crank with the standard DA7800 rear derailleur? I’m worried the chain is going to be very slack on the small/small combos.

Cheers.

You'll also need a longer spindle bottom bracket. Triples use a long cage rear derailler to take up excess chain slack when in the smaller chainrings.

It won't work. Too much difference between cassette cogs and crank cogs. You'll need a new derailleur too.

dazman said:

Hi,

I'm doing the TDF Etape (200K in the Pyrenees) in a couple of weeks and I ordered a DA triple, together with triple shifters and front derailleur just in case I run out of gas on the final climbs.

Has anyone had success with a 12-27 cassette and 52-30 crank with the standard DA7800 rear derailleur? I’m worried the chain is going to be very slack on the small/small combos.

Cheers.

Your chain will be slack if you don't use a long/SGS OR medium/GS cage rear derailleur ... how slack depends on how long it is, initially.

Realizing that you don't intentionally plan on using the small-small combination, if your chain does end up THERE, it is mostly a cosmetic issue, IMO, unless you have REALLY BAD pedaling style or are planning on some MTB-type curb-jumping or hucking ...

A few years ago, I put an old Nuovo Record rear derailleur on a bike (for one ride) which also had (for the one ride) a 42/32/22 MTB triple with a 13-28 freewheel (yes, a long-long time ago) ... since it was a very temporary setup, the chain for a ROAD crank was still in place -- the chain did not slip-or-jump when the "return" was slack (but, it did look stupid when I was stopped) and the chain was on the 32t chainring.

For piece of mind, either get an Ultegra 6603 (better) or a 105 5603 (not quite as good because of the slightly inferior pulley wheels) rear derailleur if you are concerned OR have a longer cage installed on your DA rear derailleur by your LBS (however, that will probably cost as much as a new, 6603 rear derailleur).

Thanks alfeng,

I just tried a quick experiment. With the same chain length from my double setup, the chain drop is not too bad in 30/12 and just about copes with 52/25 and I would never be riding there.

It locks with my wheelset with the bigger cassette in 52/27 however and if I made the chain longer it would be too slack. It looks like I'll do the Ultegra transplant this weekend then. Will just check first with a calculator if 30/25 gives me sufficient gain over 32/27 and if so I'll not bother. I suspect I've gained little in this easy config though.

dazman said:

Has anyone had success with a 12-27 cassette and 52-30 crank with the standard DA7800 rear derailleur? I’m worried the chain is going to be very slack on the small/small combos.

The bad news is that a short cage rear derailleur won't be able to take up the chain slack in the little/little combinations.

The good news is that practically nobody uses the granny chainring with more than the two or three largest rear cogs. Your rear derailleur will handle the gear combinations that you really use.