compact double or triple for low gears?

[cindysue]

Hey folks,

Due to my love of hills (and a recent tour with a loaded trailer), I added a 11-34 cassette and XT derailleur to my (52-42-30 triple) road bike - giving me a low low 23.2 gear inches according to Sheldon Brown's gear calculator. Well that bike has since been stolen, and now I'm looking for a replacement. I'll most likely buy a FELT bike because I get a very nice discount. The two bikes I'm considering are:

The F70 -- comes with a FSA Gossamer triple (53-42-30) crankset, a 9s 12-25 cassette, 105 shifters and derailleurs, and KMC Z9900 chain. This set-up gives me a low of 34.3 gear inches

The F55 -- comes with a FSA SL-K compact double (50-34) crankset, a 10s 11-23 cassette, Duran-Ace shifters and derailleurs, and DX10 chain. This set-up gives me a low of 38.8 gear inches. If I switch to a 10s 13-29, I get down to a 30.8. I'm not sure if this set up requires me to change out anything else (the rear derailleur, bottom bracket, etc.?). OR, Can I use a 9s 11-34 with the compact crankset? IF I can, that gives me a low of 26.3 gear inches. Not sure how 9s vs. 10s thing works........

I like the F70 for the fact it has the triple and I can change out the cassette and rear derailleur to be like my old bike. I also like that it's inexpensive.

I like the F55 because it has better components (DuraAce) and a carbon seat post. But, I've heard that the 50-34 compact crankset has problems shifting. Anyone know about this?

I don't race (but would love to increase my speed), I like hills, and I like long distances. I plan on doing a U.S. tour next June/July.

Which of the above bikes and set-ups seem optimal?

[DaveB]

Some thoughts:

Shimano doesn't make a 13x29 cassette.  Only Campy does and you can't use it on a Shimano hub or with Shimano shifters.

The widest range Shimano 9 or 10-speed road cassette is 12x27.  Shimano makes 12x32 and 11x32 MTB cassettes but only in 9-speed form.

Sheldon Brown at Harris Cyclery has custom Shimano 9-speed road cassettes in 13x30 and 13x32 format. I don't know if he has them in 10-speed yet.

Nine speed components will be obsolete quite soon. Dura Ace and Ultegra are already 10-speed and 105 will be next year.  9-speed components will be available for quite a while but will be special order only.  That's the problem with the F70.

A compact crank is limited to a 34T small chainring and there is no way you can get the same low gear as a triple.  Most road triples come stock with a 30T granny ring which can be cheaply changed out for a 26T.  This works fine and I've done it on a dozen 8 and 9-speed cranks.  A 26x25 gives a 28" low gear and a 26x27 gives a 26" low gear.  You can have super low gears with a reasonable range cassette like a 12x25 or 12x27 and not have to change the rear derailleur or have huge gaps in the cassette gearing.  

Compact cranks with a normal double front derailleur don't shift ideally but they are still very good.  The "special" front derailluers marketed by FSA and Campy only provide a slight improvement.  I wouldn't let that influence me one way or the other.  

[Styx]

I use a 42-32-22 8 Speed XT with a XTR 12-32 cassette
and need every bit of the low gearing. This is on a mountain bike with 26" wheels and a shock. I use an
Old Man Mountain rack in the front which works well with the shock in place. This gives me a 17.9 and my riding partner uses a 50-32-24 with a 12 -34 for a
19.1. I am 187 pounds and he is 225 and very strong.
I would suggest you get even lower gearing than you
are planning on, especially if you are doing LOADED
SELF-CONTAINED Tours.

[RussellSeaton]

For loaded touring, or mountain riding, loaded or not, I am of the opinion you need a triple.  I know many people claim to scale mountains with ease using the same gears the pros use, but I'd have to see it to believe it.

With 10 speed Shimano, the biggest cassettes are 12-27 from shimano and 12-28 from Interloc Racing Design.  You can use any triple crankset on 10 speed.  Or any double crankset too.  Most "road" triples have 74mm bolt circle diameters for the inner chainring.  This will take as small as a 24 tooth cog.  So you have a low gear of roughly 24x27, about 24 gear inches.  Not low enough in my loaded touring experience.  TA makes a triple crankset that will take a 58mm bcd inner chainring.  So you can get a 20 tooth inner ring.  Expensive crank but nice and low.  Having a 52 tooth outer chainring and shifting with STI will likely result in more than a few dropped chains.  Best with bar end shifters but the bikes you list have STI.

9 speed is very abundant.  And will remain so because there are millions, and millions of 9 speed mountain bikes.  All with 9 speed Shimano and 9 speed SRAM components.  Shimano only makes its mountain bike stuff in 9 speed today.  There is no 10 speed mountain bike stuff made by anyone.  Mountain bikes continue to outsell road bikes today.  You are far more likely to find 9 speed stuff in remote locations than 10 speed.  9 speed cassettes for Shimano have up to a 34 tooth large cog.  Nice for loaded touring.

If forced to buy a new loaded touring bike, it would be 9 speed.  There is no other choice really.  If I was forced to buy a new road racing bike, it would be 10 speed.  If forced to have one compromise bike, I don't know which I would choose.

If you are not doing a loaded tour, then get the road racing bike with 10 speed and get a triple.  Changing the inner chainring to 28 or 26 or 24 teeth will allow the unloaded racing bike to climb mountains very well.  Its cheap ($10) and very easy and quick to change inner chainrings on cranksets.

[sunfisher]

50-34 = 26,
23-11 = 12
yields  = 38 teeth of wrap.
DA short cage will wrap up to 29 teeth (won't work with this), the DA
medium cage supposedly will wrap 38 teeth.

You could maybe get away with an 11-25 or a 12-27, but..
Also, a quick google indicates the DA triple will accept up to a 27 tooth
cog on the cassette, so anything much beyond a 12-28 is probably out
of the question unless you swap out the rear derailleur for something
more touring oriented.

[unsub1]

Hey Russell,
Do you know if I can use an XTR crankset on Dura Ace 10sp setup? If so, which front derailleur should I use with a DA triple STI shifter?

Thanks,
steven

[tofubicycle]

The only thing I can add to what has been said here is... for practical purposes you will continue to find 9 speed cassettes of reasonable quality for years to come.  

[edit:] That, and to say: go triple.[/edit]


--
......... __ o
.........-\<,
......(O) (O)...........
...........................
i'd rather be biking.

This message was edited by tofubicycle on 7-12-06 @ 7:40 PM

[RussellSeaton]

"Do you know if I can use an XTR crankset on Dura Ace 10sp setup? If so, which front derailleur should I use with a DA triple STI shifter?"

The answer is no if using STI to shift the front derailleur.  STI and Shimano's mountain bike integrated shifters pull a different amount of cable so the front derailleur does not move the same distance.  And Shimano indexes, 2-3 clicks, the front shifter so the cable pull and front derailleur and shifter have to match between road or mountain setup.  And front derailleurs work best when the curvature of the derailleur cages match the size of the rings.  There are ridges, bumps, etc. on the front derailleur cages, inner and outer, that touch the chain at the right spot to facilitate shifting.

If you were to use a bar end shifter for the front shifting add the mountain bike triple front derailleur, it would work OK.  If you were to find a large ring of 48 to 52 teeth for the XTR crankset, it would work sort of OK with a road style triple front derailleur.  Problem then becomes the upshift from the middle to the outer ring on the crank.  If you changed both to larger rings, it would work fine.  If you used a Campagnolo Ergo shfter to shift the front derailleur it would work fine with a road style triple front derailleur.

[biker_james]

50-34 = 26,

Actually, thats 16, making for a wrap of 28, not 38.
Nine speed is going to be around for a while. As mentioned, there is no 10 speed MTB gear, so if you want to mix and match you need to stay with 9. Just think, if your shifters wear out in 5 years, and you can't find new 9 speed shifters then, buy the 10 speed, and a new cassette, and you'll be done.

[unsub1]

Hey Russell and everyone,
Well don't ask me why, but this setup works great. I've done three pretty grueling on/off-road rides on pretty technical trails and the shifting has been flawless.

I'm using:
XTR 960 cranks (22-32-42)
XTR 961 front der
Dura-Ace 7803 Triple STI shifters
Dura-Ace 7803 mid-cage rear der
Dura-Ace 7800 cassette (12-27)
Wippermann ConneX 10S1 chain

Here's the setup before I went triple.

Thanks for all your help!

-steven