new crankset

[HONDO]

Ive decided to have my entire front crankset changed out on my touring bike to a mt.crankset for overall lower gearing.I dropped the 30 for a 24 up front which was fine but I would like more useable gears.Ive got an 11-34 in the back.Suggestions, advice appreciated.My knees will thank you.

[whittierider]

What do you have now?  A standard road triple with 74mm BCD tiny ring and 130mm BCD middle and outer rings can go down to 24 teeth for the small one, but the middle won't go below 38.  Any smaller would make the bolts get in the way of the chain.  110mm BCD, used on road compacts, will go a little smaller, but I don't remember offhand ever seeing a triple with 110mm BCD for the middle and outer rings.  They probably exist but I haven't paid enough attention.  Otherwise you're into an MTB crankset.  If your frame won't allow a clamp-on front derailleur, you might be limited on how small you can go, since the bracket for the other type might be too high for good operation with smaller rings.  Our tandem has 24-42-52 and shifts fine and does not drop the chain even when going from 42 to 24 (which is a big jump).  Our low is 24/34 which I put on after the first time I climbed an 8-mile-long 10% grade with my wife who's definitely not a climber!

[HONDO]

My front is now 52-42-24 with a chain watcher and honestly it works great.I just wasnt sure if I would be getting into a mess not including the cost by lowering the entire crankset.  

[DaveB]

If you stay with a 24T granny ring, your lowest gear will remain exactly the same as it is now but fitting a "touring" crank with smaller middle and large chainrings can give you more usable intermediate gears with smaller steps.  A current MTB crank (58 mm BCD or 64 mm for the granny ring) will accept down to a 20T chainring.  

Note to Wittierider: 110/74 BCD triple cranks used to be very common and, in fact, were the original MTB crank configuration.  Suguino, SR, Shimano and Sun Tour all made them in the past.  Shimano's RSX triple road crank, made through the late '90's had a 110/74 BCD.  

A 110 mm BCD will accept down to a 33T chainring but 34T rings are far more common.  

[WesternFlyer]

I ride with a set of Race Face 110/74 with 46/34/24 chainwheels and a 11-34 cassette and love it.  The Race Face is CNC milled and is butter smooth.  You will not find yourself setting any land speed records with the tallest gears, but I do find I use the 46 much more and in different gear combinations than I ever did a 48 or 50.

Western Flyer

We must ride light and swift.  It is a long road ahead.

King Theoden

[HONDO]

Thanks again all for the info.This kind of stuff gets me through the winter until riding season.Until then its back to the stationary.

[Westinghouse]

I have never attended much to such matters as gear numbers and such, though I suppose I should have more carefully. I might generally go with 48-38-28 on the front, and a standard (if there is such a thing) five-ring cluster on the rear. Hitting mostly level or relatively level ground on coastal Florida is one matter. The S-tier is another matter. And the PCBR is quite another  matter again. Gear numbers are something to consider for sure. It is just that I have always just geared up and gone. I remember using a  seven ring rear cluster on the northern tier with a large inside gear because of long steep grades. Usually, on highway ninety, I used only two or three gears on the rear, and 38 and 28 on the front.

[RussSeaton]

You should be able to buy any mountain bike crankset from a place like Nashbar put it on the bike.  I suspect an appropriate bottom bracket would be available at the same store.  The 4 arm 104/64 mm bcd configuration which seems to be most common, only allows a 22 inner ring, which does not get you much lower than your current 24 ring.  The hard to find 58mm 5 arm does go down to 20 for the inner, but its hard to find.  The 44-32-22 rings on the 64mm bcd crank will give you more medium gears with the 44-32 rings.  I guess that may be better than the 42 middle ring you currently have.

Depending on which front derailleur and shifters you have, you may have less than good shifting with the new setup.  Road and mountain bike front derailleurs have different curvature for their different big rings.  And I've heard road shifters and mountain shifters don't particularly like to shift the other type of front derailleur.  So changing cranks may introduce other problems.

[Tourista829]

I have a Raceface crank on my Comotion. I love it! 24-34-46. Built extremely stout. The 34 is very smooth and the 46 flys. I believe a 24 front and 34 rear is pretty low, but a 22 would work too. I would pay attention to the crank length. Raceface only comes in 5mm increments. So if you need a 172.5 like me, well, but the 175's still allow me to spin enough.

[paddleboy17]

I don't always like to promote Shimano, but its hard to beat the current Shimano LX crank.  It is stupid lite, and has a sensible steel 22 tooth granny, and equally sensible aluminum middle and outer chain rings.  If you are going to a smaller crank, you probably have to replace the front deraileur as well.  The Shimano XT crank has an aluminum inner chain ring and composite middle chain ring (might have steel teeth).  That might be OK for mountain bike racing, but I don't think I would tour on it.

It was not that many years ago that cranks were a lot heavier.

[yakjack]

Does anyone have experience marrying a mostly shimano 10 sp road bike with a Sugino xd600, 46-36-26 crankset? I'm trying, using a 12-27 cassette, 105 FD-5603 (band type), 110mm BB. Kind of works, but shifting from the middle to the top is not so smooth. Any suggestions on what I can do to improve this? Any other options for crankset gearing in this range on a 10 sp?

[staehpj1]

You might find that the less expensive Tiagra FD works better with that range of rings.  Never done it with 10 speed though.

[RussSeaton]

Does anyone have experience marrying a mostly shimano 10 sp road bike with a Sugino xd600, 46-36-26 crankset? I'm trying, using a 12-27 cassette, 105 FD-5603 (band type), 110mm BB. Kind of works, but shifting from the middle to the top is not so smooth. Any suggestions on what I can do to improve this? Any other options for crankset gearing in this range on a 10 sp?

Your problem is front derailleurs are shaped for specific size chainrings.  Road front derailleurs are shaped to curve just right along the outside of a 53 tooth chainring.  The tail end of the front derailleur will hit the chain just right when shifting and move the chain up to the big ring.  With your smaller 46 ring, there is a big gap between the tail of the front derailleur and the chain.  The tail of your front derailleur is an inch or so higher than the chain.  So the chain hits towards the middle of the front derailleur when upshifting.  Whereas on a road bike, the gap between the tail of the front derailleur and the chain is less than half inch.  There isn't much of a fix for your situation other than trying different front derailleurs in the hope one will shift better.  Or change the outer and likely middle ring to the common road size of 53-39.

[whittierider]

Your problem is front derailleurs are shaped for specific size chainrings.  Road front derailleurs are shaped to curve just right along the outside of a 53 tooth chainring.

Additionally, the sides of the FD are not just flat pieces of sheet metal, but shapes pressed into them are intended for certain step sizes between rings.  FDs made for doubles are usually intende for about a 14-tooth size difference between rings, and for road triples, 30-39-52 or 30-42-52.  A common problem I see though is that the FD is mounted too high.  The outer piece should clear the big ring by only 2mm as it goes by in a shift to or from the big ring.  Another common problem I see is the angle, with the rear tip of the FD rotated in too far.

[yakjack]

With your smaller 46 ring, there is a big gap between the tail of the front derailleur and the chain.  The tail of your front derailleur is an inch or so higher than the chain.  So the chain hits towards the middle of the front derailleur when upshifting.  Whereas on a road bike, the gap between the tail of the front derailleur and the chain is less than half inch.  

I have to assume you mean the tail of the FD is lower than the chain? And I am dealing with a road bike. I know I'm trying something unconventional here, but what FD do people generally use with these Sugino cranksets?