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-   -   Crankset 130BCD for Shimano UN55 BB (68 x 115mm) (http://www.bikeforums.net/bicycle-mechanics/941715-crankset-130bcd-shimano-un55-bb-68-x-115mm.html)

HK 45 04-04-14 08:42 PM

Crankset 130BCD for Shimano UN55 BB (68 x 115mm)
 
I'm looking for a replacement crankset that will work with some parts that I already have on the bike but it's a real headache looking for something specific using amazon or ebay. Anyone know of any site that lets you look for cranksets based on measurements or of any cranksets that might work in my case? I've found a few that work with 68 x 113mm BB's but not 115mm and I've no idea if such a jump would make a difference since I tend to stay with within 1mm +/- of most specs.

Jeff Wills 04-04-14 09:31 PM

A crank that works "best" with a 113mm BB will probably work OK with a 115mm BB. You're only moving the crank outboard by 2mm at most- remember, most rear cogs are 5mm apart. Derailleur systems deal with more deflection all the time.

If it's a single-speed, put a spacer under the rear cog and quite worrying.

HK 45 04-05-14 02:33 AM

Quote:

Originally Posted by Jeff Wills (Post 16643204)
A crank that works "best" with a 113mm BB will probably work OK with a 115mm BB. You're only moving the crank outboard by 2mm at most- remember, most rear cogs are 5mm apart. Derailleur systems deal with more deflection all the time.


If it's a single-speed, put a spacer under the rear cog and quite worrying.


The ones I found before were mtn bike tripples, particularly the alivio which didn't clearly state if it was the octalink or the square model but it definitely wasn't 130BCD.


The crank is for an 8 speed bike that I use with a 130 x 38t surley steel chainring and ride most of them time on the 11t of the cassette.


My biggest problem in finding a suitable replacement is having faulty specs in nearly every site. I like how this one changes BCD based on what color the crankset is.


http://www.amazon.com/Retrospec-Bicy...8Q4SBJ8NP7T9XV

dsbrantjr 04-05-14 05:44 AM

I think that you are letting the tail wag the dog. Find a crankset that you like and get the BB it requires (they are sometimes sold as a set at an attractive price) rather than trying to find a crankset which matches the BB you've got.

Bill Kapaun 04-05-14 06:20 AM

Quote:

Originally Posted by dsbrantjr (Post 16643566)
I think that you are letting the tail wag the dog. Find a crankset that you like and get the BB it requires (they are sometimes sold as a set at an attractive price) rather than trying to find a crankset which matches the BB you've got.

+1
That's akin to saying I have an engine. What car fits it.

Also 130BCD really doesn't have anything to do with the BB. That's just a typical "road" crank BCD.

2mm probably isn't going to matter.
I actually have my chainlines a little wide since I tend to use the outer cogs more.

A 2mm longer BB "MIGHT" only be 1mm longer on the DS, if it's symmetrical.

HillRider 04-05-14 07:42 AM

The 8-speed era Shimano Ultegra crank (FC-6400) specified a 115 mm square taper bottom bracket so, if you can find one of them, your bottom bracket will work.

However, I agree you are looking at this backwards. A BB-UN55 is a low cost bottom bracket and trying to find a crank based on using it is a poor approach. Find a suitable crank and then get the matching bottom bracket.

HK 45 04-05-14 04:29 PM

I decided to go with a 170mm FSA Tempo Tripple crank after finding a site that listed some info on it

Bolt Circle Diameter (BCD) The middle and outer ring are 130mm BCD, inner is 74mm.

BB spindle; Standard (JIS) Square Taper.
118mm produces the same chainline as Shimano 105/Ultegra triples.


160mm FSA Tempo 130/74 BCD Triple Crankset

I bought it from this seller which doesn't list much info but I asked him what the BCD was in case the cranks varied in any way.

FSA Tempo Triple 170mm Crankset | eBay

Bit of trouble to find a proper crank but not bad for $31 and I plan on taking off the 52t to move the 42t up front and use my Surley 38t in the middle which my chain is used to using by now.


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