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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 08-22-12, 12:24 PM   #1
BezO
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Replacing Crankset - Questions

Trying to read up on this confused me more than it helped.

If I want to use my current bottom bracket, what should I be concerned with regarding the new crankset?
My BB is 68x103 tapered square. Not sure it's relevant, but my current chainring is 46T with a 130 BCD(according to this chart).

Is it better to change the BB along with the crankset to be sure everything is compatible?

Either way, since my freewheel is involved in creating the chainline, are there measurements back there I need to be concerned with?

Because I want a chain guard, and they seem non-existant for 46/48T chainrings, I'm considering the Sugino XD2 w/guard. There's no BB compatibility info listed and I'm not sure what to ask.

Any info would be appreciated.
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Old 08-22-12, 12:30 PM   #2
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Oh yay I get apply what i've learned.
Step 1: Pick Crankset
Step 2. find bb that fits cranks

If you want to re-use your bb then find a crankset that is compatible with a 103mm and Square Taper spindle. Like this one : Click me baby!
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Old 08-22-12, 12:51 PM   #3
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Thanks for the quick reply!

So it's the length of the BB that's important? I'm guessing because of the chainline.

That RD2 has the chain/tooth size & crank length I'm looking for. I just wonder why chain guards don't come in larger sizes? It's really the only reason I was looking at the XD2 that comes with the guard. But they don't list the BB length.

I'm also realizing that I was mistaking the XD2 for the RD2.
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Old 08-22-12, 02:05 PM   #4
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These guys say the chainline with a 103mm is 45mm.

See this post where dude says 110mm gives 45mm. The rest of that thread seems to indicate that 110 is the outer ring. Which makes sense.

I think it's all a load of crap and you are screwed!

46T bashguard $26 shipped
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Old 08-22-12, 02:17 PM   #5
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Thanks for the quick reply!

So it's the length of the BB that's important?...
yes...if by length you mean the spindle length to work with a particular crankset & you know whether taper is jis or iso.
Crandrew gave you good advice & you could do worse than take it. rd2 is fine as a ss crankset, i had my ring on the outside & had perfect 43mm chainline. while there are many other cranks that could work with your bb, do you really need/want to spend more time & effort looking thru them?

get smart & stop worrying about a chain/bashguard...
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Old 08-22-12, 02:23 PM   #6
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Why do you want a chaingaurd?
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Old 08-22-12, 02:25 PM   #7
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cause its JDM.

edit: wrong forum
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Old 08-23-12, 06:41 AM   #8
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Quote:
Originally Posted by Bat56 View Post
These guys say the chainline with a 103mm is 45mm.
According to a Sheldon Brown article, my chainline is likely 42mm. Now that I know how to measure it, I'll do so.
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46T bashguard $26 shipped
I came across this site at some point. No 46T in silver. And I'll likely be going with a 48T crankset and they don't carry that size guard at all.
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Originally Posted by markaitch View Post
yes...if by length you mean the spindle length to work with a particular crankset & you know whether taper is jis or iso.
Not sure about JIS vs ISO. I'll have to look into that.

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get smart & stop worrying about a chain/bashguard...
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Why do you want a chaingaurd?
I've ruined 2 pairs of pants so far. Not a terrible ratio as I commute to work almost every day, but I'd prefer not to ruin another pair of pants.

Thanks folks
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Old 08-23-12, 06:54 AM   #9
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Bashguard won't save pants. For real.
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Old 08-23-12, 07:04 AM   #10
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FWIW, the Sugino RD2/Messenger claims to have a chainline of 45mm when using the proper 103mm BB but the set on my lady's bike measures closer to 43mm.

OP - roll up your damn pant leg like the rest of us.
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Old 08-23-12, 07:45 AM   #11
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OP - roll up your damn pant leg like the rest of us.
+1
Its what the cool kids do.
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Old 08-23-12, 08:36 AM   #12
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Not sure about JIS vs ISO. I'll have to look into that.
Thanks folks
I might get some hate for this, But I wouldn't worry about iso - jis TOO much. I'm running an iso crank on a jis bb and have yet to have a single problem. But yes, ideally you'd want to have an iso with iso and jis with jis.
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Old 08-23-12, 08:51 AM   #13
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True, but

Quote:
Originally Posted by Sheldon Brown
If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length.

Confersely, if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.
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Old 08-23-12, 09:20 AM   #14
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True, but
Quote:
Originally Posted by Sheldon Brown
If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length.

Confersely, if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.
Confersely?

Anyhoo - I love this little diddy. After making the mistake a few times over the years I have a bucket of bottom brackets and a few cranks. I don't know if they are JIS, or ISO, or WTF. Plus, it does not matter because some of the cranks are used a bit compressed (the tapers). I just slap stuff together until it works.

I know this does not work with new stuff. And I apologize for that. But when splitting hairs over 2 mm here or there I do not believe that even new matched parts are going to work out perfectly every time. (Notice - I said "every" time.)

All that said, know the information above allows you to mix and match your parts and use that too-long or too-short bottom bracket that you got a great deal on.
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Old 08-23-12, 09:47 AM   #15
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Chainguards are useless, unless they enclose the whole drivetrain. False sense of security. You will still suck your pants leg into it, just a little less often.
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Old 08-23-12, 10:07 AM   #16
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You can also get the sweet reflective bands that hold your pants tighter to your leg.

Or just wear skinnier jeans.

Or just roll your pant leg up.


lol'd at replacing a crankset to solve the problem
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Old 08-23-12, 12:20 PM   #17
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Quote:
Originally Posted by Scrodzilla View Post
OP - roll up your damn pant leg like the rest of us.
C'mon man. It's the 1 time out of 100 that I forget that's the problem.

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lol'd at replacing a crankset to solve the problem
Yeah, it is funnier if you assume I'm changing my crankset instead of rolling my pant leg up.

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Chainguards are useless, unless they enclose the whole drivetrain. False sense of security. You will still suck your pants leg into it, just a little less often.
I've never actually had my pants leg eaten by the chain/crank. What happened each time was that I forgot to tuck my pants in my sock, went to put my foot in the strap & brushed my pants on the chain. The cleaners was not able to remove the stain.



Fellas, chain/bash guard or not, I'm changing my crankset. I purchased the bike used for the frame. Many of the parts were old and/or cheap. I've been replacing them as I go. The cranks are next in line.

I've seen the RD2 suggested a few times. The price & quality fit in with the rest of my bike. I mistook the XD2 for the RD2 & thought I found a great solution to 2 problems.

But again, I get it. It's much more fun to set up jokes. I'm happy for the few serious answers. Thank you!

Last edited by BezO; 08-23-12 at 12:27 PM.
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Old 08-23-12, 12:46 PM   #18
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We are just having fun. Im sure after the one pair of $200 pants are ruined you will remember to roll
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