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Discussion Starter · #1 ·
Hey all,

I do a lot of climbing here in Utah, but I am only 135 pounds soaking wet so I descend like a feather. (remember, F=MA)

For making it up the hills I currently run a 50/34 (FSA K-Force 110 BCD, 10 speed) with a 12/25 shimano cassette. I run a standard ultegra front derailleur. I would like to descend a bit faster, but the 12 in the back and the 50 up front slow me down. Therefore, I'd like to put a 52 on there and keep the 34. Will this work? Has anyone ever had an 18 tooth transition with an Ultegra? I have an FSA compact specific FD on my 'cross bike, is that going to help? I know an 18 tooth transition is a lot to ask of a FD, but if it works...

What types of alternatives are out there?

Would a 12/27 with a 53/39 afford me similar ratios?
I'd rather not buy a whole new crank.
 

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Sounds like a stretch

The 16 tooth jump is a big one anyway for the standard derailleur. Going to 18 is definitely stretching things. You can probably get a 52 at airbomb.com or aebike.com, but they would not be matched for the small compact ring (110bcd compared to 130bcd for the standard cranks). You likely will also need to try a compact FD. Normally not a requirement, but you would need the additional capacity. These are pretty cheap.

You may also be able to try a 52/36, which then maintains the 16 tooth jump. 34 to 36 is not much of a jump. Not sure of the make of your compact crank, but I know aebike has chainrings you can buy to create the setup you want (just don't know if there is anything bigger than a 50T for 110bcd cranks).

Probably my biggest question is whether you can ride the 39/27 for the climbing you do. If so, that sounds like a better option.
 

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no math whiz...

A 34/25 is about the same as a 39/29, since 25/34 x 39 = 28.7. Your current 34/23 is just a little lower than a 39/26. Changing to a 53/39 with a 12-27 would than be a costly option that would not provide the same low ratio as yo have now. If you don't have any real need for the 34/25, then one option would be to switch to an 11-23 cassette.

Trying a 52/34 would be a poor choice since not only would the shifting be lousy, it would require a 4-5 cog shifts to make the transition.
 

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11-25

Another possibility is to make an 11-25. You do this by buying either a 11-23 cassette, or loose 11 & 12 tooth cogs. Then your (10 speed) cassette is:

11 12 13 14 15 17 19 (21 23 25)

I haven't tried this before, but it is a pretty common trick. You lose the 16 tooth cog, but getting wide gearing like this forces a comprimise somewhere.

You can use this page to compare the gear ratios of all of your options...
http://sheldonbrown.com/gears/
 

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Discussion Starter · #6 ·
C-40 said:
Changing to a 53/39 with a 12-27 would than be a costly option
I agree. Also, I never thought of the transition issue. That's way too much shifting, especially if I do crits on that same bike setup. Great observation.

bobsmargs said:
Another possibility is to make an 11-25. You do this by buying either a 11-23 cassette, or loose 11 & 12 tooth cogs.
I think I may try this. There's a crit here every tuesday that I could use the 11-23 if my little experiment goes awry.

cthomas said:
Probably my biggest question is whether you can ride the 39/27 for the climbing you do. If so, that sounds like a better option.
A bit pricey, but it would provide most of the ratios I need for racing.

I also have a compact FSA 16-tooth FD on my CX bike, I could steal it. However, honestly, the Ultegra works better on my compact crank than the "compact specific" FSA one. Go figure.

Hey everyone, thanks for the advice. I think I may try the homemade 12-25 option. It will be cheap, easy, and I can always use the 11-23 on flat courses and crits if it doesn't work out. It's fun being small going up hills, but the other side...
 

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I think Shimano sells an 11-25 now.
Another option is to use 110mm BCD 52/36 chainrings and change the cluster to a 12-27. You'd still have the 16t difference up front, and a similar low gear.

I'm 6' tall and 142 lbs so I've got a similar problem. The only time I could use gearing higher than 50x12 is on not so steep or technical descents, to squeeze out a couple more mph to get into the draft of a larger rider.
 

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As much as I enjoy my compact with a 36/50, it sounds like you need a standard crankset and a big cassette, some thing like a 13-29 or 12-27. I usually have an 11-23 on my bike and find that I can descend well on a 50-12 or 11. I am usually the guy people line up behind. A 36-23 will handle most anything I encounter here on Oahu. If I did swap back to my old 39/53, I would use a 12-25. When I reach the triple point of my life, I will have to rethink everything.
 

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Good thought going on here, adding a twist

I race cyclocross and recall running out of gears on the final sprint. I run a single ring 42 or 44 with a 13-26 (campy).
I hashed out everything last night noting gear inches, then stumbled upon this discussion this afternoon.
Campy offers 11-21, 12-23 and 13-26. Seems that building a custom 12-25 or even an 11-25 for some races should work. The other option would be two re-configure a double in the front, anything between a 39-42 inner and a 46-50 outer.
I deduced that signifigant increases in gear inches happen in the rear, not by adding 2t in the front. ie running an 11 opposed to a 12 and in my case 12 for a 13.
 

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Discussion Starter · #10 ·
kannas said:
I race cyclocross and recall running out of gears on the final sprint. I run a single ring 42 or 44 with a 13-26 (campy).
I hashed out everything last night noting gear inches, then stumbled upon this discussion this afternoon.
Campy offers 11-21, 12-23 and 13-26. Seems that building a custom 12-25 or even an 11-25 for some races should work. The other option would be two re-configure a double in the front, anything between a 39-42 inner and a 46-50 outer.
I deduced that signifigant increases in gear inches happen in the rear, not by adding 2t in the front. ie running an 11 opposed to a 12 and in my case 12 for a 13.
Yeah, an 11 vs 12 or 13 in the back will give you more gear inches the right direction. That's a good point, because it would save a lot of folks $ who are in my similar predicament. I run shimano so I'll have to look for that 11-25 or build one myself.

A single 44 or 42 up front on a cx bike is pretty common on the courses out here, but most of the A's/pros out here will run a 46/36 with anything between an 11-23 and a 12-27 in the back. I'm not sure about the campy boys, though.
 

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I pondered teh whole compact idea for awhile, but I found the cheapest solution for steep climbs, (category 1) is to go with a standard durace 10 and swap out the 39 for a 38 and run a 12-27. It gives just a little more but it helps, and the shifting is ok as well, with the added bonus of 53 up for to crank on.
 
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