Converting to Compact Cranks
 

I'd like to convert to a compact crank set up. Currently I have a 10 speed Ultegra setup with the standard 53X39 in the front and 12X25 in the rear. I would like to do this as inexpensively as possible. I assume I can keep the cassette and hopefully both the derailers. What are my options and cost assuming I have to have the LBS do the work.

If you really want to do it on the cheap this is a fairly easy DIY job. You'll need to buy the crankset and probably a new/matching bottom bracket -- though if you know what you have and shop carefully you might be able to reuse the existing BB. You'll also need to buy or borrow BB and crank puller tools. Don't let that put you off: buying will still probably be cheaper than the labor the LBS will charge you, and you can re-use them for later maintenance, upgrades, friends, etc. Procedures are documented at the Park Tool website.

A far cheaper way to achieve the same effect is to just replace your chainrings. A 48-tooth outer ring and a 38-tooth inner ring can be had for about $75 at most mail-order houses. Just be sure they're 5-bolt rings for a 130mm diameter bolt circle. And you don't even have to remove the drive-side crank arm to do the job! You will, however need to remove a couple of links from your chain. And you'll want to re-position the front derailler about 10mm lower to match up with the smaller diameter outer ring.

The difference between a 38T and 39T chainring is too small to bother with. What are you trying to accomplish? A lower high gear or a lower low gear?

I agree with HillRider. Though changing out the cranks would be less expensive outright, it's a practically useless exercise unless the entire purpose of the exercise is to lose a lot of high-end. I have to assume that the OP wants to go compact in order to get a lower low gearing, and going from 39 to 38 is just not going to have much effect at all. You can't go lower than 38* on 130 BCD, you have to go to 110/"compact". Most compacts are 50/34 which still keeps a decent high end but gives a pretty good low-end with that 12-25 cassette.

Cost-wise, a new compact crank setup will run around $200 on the cheap end (sometimes Performance/Nashbar run specials and I've seen them as low as $169). A BB should be around $50, and the tools will cost about $20-30. An LBS is sure to charge at least that much when you include the labor, not to mention the problem of being without your bike while they do the work.


*sydney used to say there were 37s available but I think I remember you had to have special chainring fixing bolts because the clearance is so tight. I've never seen 'em and I'm not sure I'd want to use them!

Shimano now makes an Ultegra-grade compact crank, the R700 for 10spd that retails for around $269. You wont need to replace anything, just lower your current front der. As for tools all you need is the TL-FC16 for tightening the cap on the non-drive crank, which may come with the crank, and a torque wrench for the pinch bolts. Shimano 10spd cranks dont require crank pullers -just tap with a mallet to remove after removing the black crank cap and loosening the pinch bolts on the lh crankarm. Seems perfectly logical to go to a compact setup if you dont have the knees for a 53x12...

on the r700 you also have to buy the bbcups, they do not come with the r700

nashbar has a compact crank for around 100$ last i looked. you can find a ritchey wcs compact for about 150$ at performance, glorycycles, and repartocorse.com,
i can't remember which had the best deal.

AEbike sells FSA Gossamer cranks for about $120, but you need an ISIS bb, so that has to be factored in.
I saw Nashbars, recently, think it is probably ISIS also though.
Steve

If you are going from Ultegra to a Shimano compact why do you need new cups? They should be reusable.

Tim

doco, Ive sourced them and the cups do come with depending on where you get them. Since he already has Ult 10spd setup OP has no need for them anyway, 'cept as spares. Simpler to get the R700 and adj frnt der accordingly than downgrade. A few links will likely need to be removed, also. Simple task for yer lbs or yer self if you have right chain tool, crank cap tool(may be included with crank) and access to a torque wrench for pinch bolts. The service instructions that come with the crank are pretty straightforward or refer to Park Tool's site for advice. Yes, a $100 Nashbar crank would be cheaper, $13o with Nashbar ISIS bb, but why not stick with comp. quality to what you have. The nashbar crank is 8/9spd anyway, meaning it could still functionally work, but may be more finicky and I doubt that it will have the stiffness of the Ultegra crank you already own. There's a reason theyre so cheap, but if price is more of a concern...

Thanks for the replies. I've been trying to respond since last night but the server keeps stalling my attempts. This is the 4th or 5th time I am trying. Anyway my reasons are two fold. Mainly I want a lower gear the spin better up the fairly steep, but short hills around where I ride. I like to ride in the large chain ring in the front. At the speeds I usually ride I find myself shifting between the two front rings too frequently although slightly more in the large ring. A compact will keep me in the larger ring most of the time except when those steep hills come up.

...and youll be able to make use of the higher cogs on yer cassete without taxing yerself with a 53. Seems like a better solution overall than a triple which would be slightly more expensive and add more confusion to gear choices for most folks. Simple in your case is better.

My experience with the compact conversion is what you hypothesize, you stay in one chainring til near the very end and then when you do shift you have to double shift, 50->34 front and 23->19 or 17 in the rear. Altho the 50/25 works fine I find it better to downshift to the 34 early on longer hills and upshift the cassette 3 cogs at the same time and work back up the cassette as the hill progresses. A bit awkward but it works better for me than bogging down near the top in the 50/25. The opposite occurs at the 12t cog end for the 34t cw. As I use the 30t CW on the triple only on rare hills (about once every 4-6wks) the compact is a welcome improvement.
Steve