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idodweck 06-22-09 06:06 PM

help choosing a road crank for a not-a-road bike
 
hi,


i'm looking for a new chainset for my scott sub 10. the current one, though decent, can't have more than 50t since it's 104mm bcd (at least i couldn't find).
- what kind of issues i might encounter?
- what specs should i pay attention to?

for example - i thought about the ta specialities alizé that i found for not too much. the quated chainline is 45mm while right now it's 50mm. is it a problem?

any other recommendation for another good (mainly strong as i'm an urban/touring cyclist) in the 100-200 euros zone?

thanks///

thirdin77 06-22-09 10:13 PM

So you want bigger than a 50T big ring? That's why you want a different crankset?

You could use a square taper crankset and then use whatever bottom bracket length you need to in order to get a 50mm chainline. That's the upside of such cranksets, you can adjust the chainline.

I'm thinking you could get a 130/74 or 110/74 bcd crankset and run a 52 or 53T big ring.

idodweck 06-23-09 01:23 AM

yes, it's for having a bigger than 50t.
how do you adjust the chainline with a square one? washers?

thirdin77 06-23-09 01:59 AM

AFAIK, You adjust the chainline by just using a new, different bottom bracket. It's not that awful, monetarily, since they cost about $20-30 each

There's an old school bike shop in my area and he has a bunch of used bottom brackets which would be good for someone to buy or borrow for going through the trial and error process of finding the right size. You might inquire with a local shop for just that.

You can check sheldonbrown.com for sizing advice.

bikinfool 06-23-09 01:59 AM


Originally Posted by idodweck (Post 9149969)
yes, it's for having a bigger than 50t.
how do you adjust the chainline with a square one? washers?

Different spindle length bottom brackets is how you adjust on a square taper type.

You don't necessarily need a 50mm chainline but that depends on your bike. How close are your cranks to your frame's chainstays now? Are you running the 700c or 26" wheels on yours, and how big a tire would do you want to use (might get some interference with a narrower chainline in low gears with fat tires)? Do you still want a triple crank?

idodweck 06-23-09 02:18 AM

thanks for the inputs.
So if i understand - i have to figure out before buying a new bb the exact size I'll need in order to make it work at 50mm?
right now i 15-16mm distance from the chainstay to the big chainring.
I'm using 26" wheels 1.35 tyres but might go to 700cc one of these days.
anyone tried the alize crank? I use the chinhook chainrings which are good but never tried any other ta-specialities product. any other suggestions?

Garthr 06-23-09 05:24 AM

While an Alize is a fine crankset, you are aware it has a 130mmBCD, yes? Just so you know, you're limited to 38t min ring, so in the future if you want to use it with lower gears on this or any other bike, you can't. TA makes great stuff, and I would recommend this crank for a road bike, this bike I'm not so sure.

110mm BCD cranks are the most versatile. You can still get big rings, up to 60t, and can go low as 34t. You can get a nice one here with your choice of rings, a big plus. http://gaerlan.com/bikeparts/parts/crank/crank.html
I wouldn't recommend the Sugino XD crank unless you bought it from someone who could swap out the rings you wanted on it, as it comes with smaller rings.


Looking at the Scott here http://scottusa.com/gb_en/product/196/665/sub_10 it comes with a 26/36/48 and a 11-32. That's a 111 gear inch top gear. You're paying a steep price for a few extra gear inches!

You may want to check of a 50 or 52 ring even clears your stays.

As far as chainline, yes, you adjust it by BB length, but also using 1,1.5 or 2mm spacers between the frame and DS cup. Many times all you need is a mm or two on the DS, so these save you from getting another BB. http://www.biketoolsetc.com/index.cg...-and-Freewheel

idodweck 06-23-09 05:05 PM

thanks garther,
it's not only for getting extra power but in order to use more efficiently the gears - i tend to use quite exclusively the 48t chainring and 3-4 cogs.
considering your reply I spent way too much time looking for a triple crank in my price range, available in Europe with 110mm BCD....

found out that only stronglight have some:
stronglight impact triple..
stronglight z light triple
otherwise there are all 130mm...
worth it?
any other suggestions?
thanks again

thirdin77 06-23-09 11:56 PM

I have the Stronglight Impact triple with 48/34/24 rings and I got it mostly because it came in the exact ring combination that I wanted. I got it from xxcycle.com.

It was worth it for me at the time and I still have it on the bike but xxcycle charged me about $20 for shipping and it took about 3-4 weeks to reach my doorstep.

If I were to do it again, I would probably just get an equivalent Sugino crankset from a vendor here in the United States as shipping would probably cost less and would certainly be faster.

The Impact Triple works fine though like all 3-piece type cranksets, it's laterally flexible and I get some chain rub against the front derailleur when I get out of saddle to sprint.

I don't know of any other 110/74 bcd cranksets.

chrispe 06-24-09 12:38 AM


Originally Posted by idodweck (Post 9154039)
thanks garther,
it's not only for getting extra power but in order to use more efficiently the gears - i tend to use quite exclusively the 48t chainring and 3-4 cogs.
considering your reply I spent way too much time looking for a triple crank in my price range, available in Europe with 110mm BCD....

found out that only stronglight have some:
stronglight impact triple..
stronglight z light triple
otherwise there are all 130mm...
worth it?
any other suggestions?
thanks again

If all you are looking for is to have more gears available in the range you normally use it might make sense to just replace the cassette or at least try that first. It will be cheaper, easier, and possibly a better solution. If you are still using the stock 11-32 cassette you could try a 11-25 or something like that. If your only using the 3-4 smallest cogs this would put more like 4 or 5 maybe even 6 in the same range.

Garthr 06-24-09 06:12 AM

I agree with chrispe here, trying a close ratio cassette is much cheaper possible solution. There's nothing wrong with using a 48t ring. I use a 48t big ring with a 13t cog, and I live in hilly area. . . I just learned to pedal fast and smooth. . . or if I'm out of gear . . . enjoy the ride downhill:) My only competition is my own head, so I don't worry about that.

I'd put your gears into a gear chart like this one http://home.earthlink.net/~mike.sherman/shift.html , look at what gears you are using the most, and try to find a close ratio cassette that would fill some of the gaps in your current cassette(11-32 is your current?). This will make your smaller rings more usable too, if you need to use them.

:cheers:

idodweck 06-24-09 09:38 AM

thanks. tried it already but i still spend most of the ride on the big one in front and the 3 small ones behind and for some reason the derailleur is less smooth with the cassette i use (shimano 6500). even when touring with a load. maybe it is bad technique though. the idea is to go up in front in order to use more of the 2nd ring with the middle of the cassette.
I can change the 2nd ring for 42t and the third for 30t but i have the impression the the progression between the rings will be a bit awkward - lot of "space" between the 3rd and the second and much less between the 2nd and the 1st. (40% and 14.3% while 38.5% and 33.3%). so i figured out the i could change the 1st to 50t (the biggest 104mm i could find) in order to compensate but the price of the 3 comes to almost the price of a new crank (100 euros...).

btw I just figured out i might need to change the derailleur to a road and and find a way to adjust the routing for button pull... clamp and such... anyone tried deore xt front with bigger than 48t?

Garthr 06-24-09 10:50 AM

Well, it's back to a new crank then:) The Stronglight Impact is sold with 30/42//52 in Europe. That's a good deal there. Yeah, that's your best option in my opinion.

Super easy to get replacement rings down the road for the 110/74. Easy to get the BB's. What's not to like?

You may need a 113 or 115 BB for your frame. http://www.xxcycle.com/jp400-alloy-cups,,en.php This will take some trial on your part. If I was installing it, I'd get the 113 BB and a 1, 1.5 and 2mm BB spacer. That said, I don't know your frame at all, so I cannot be sure.

You would need a road triple FD, I believe the rings are too big for XT FD's.

Hope that helps.

:cheers:


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