Square BB question
 

Are they all alike? I am planning to swap Cranks. the current set has Shimano MC08 cranks. I was planning on buying

http://www.bikeparts.com/search_resu...p?ID=BPC332188

Does anyone froesee any problems w/ a direct swap?

Thanks!

As long as they both take the same spindle length, you should be fine.

Ok, I will have to look in to that! I don't know the length of the orgional spindle yet so I will have to remove it tonight and measure.

Thanks :)

Ooops, I got current and new crank mixed up, this should make sense now:

Current crank mc08 likes a 110mm spindle for a 47.5mm chainline.

possible new crank fc-m410 likes a 113mm spindle for a 47.5mm chain line,

If your bb is as Lester looked up, and you increase chainline by 1.5 mm (1/2 of 3mm difference in spindle length) you'll have a 49mm chainline. The current crop of Shimano external bb type cranks are 50mm chainline, so likely you won't have a problem with just swapping cranks...

May be true but all that's done for me generally is getting me in trouble...

Where can one find information like you have presented? I think it might prove to be handy in the future

nevermind my googlefu is getting better. I just didn't know to ask about the length of the spindle. I'm such a newb. :lol:

Now that i reviewed my options, would these be a better choice? I was planning on staying Shimano, but I am having trouble finding a good fit.

Sugino Impel 150X triple mountain bike crankset is 7- and 8-speed compatible.

• SuperShift chainrings with ramps, pickup pins and special tooth profiles for shifting performance and less chainsuck
• Black outer ring, silver steel inner rings
• 7/8-speed compatible
• 4-arm, 4-bolt spider
• Color: Silver
• Weight: 690 grams
• Spindle Interface Type: Square Taper JIS
• Spindle Length: 113, 110mm
• Pedal Spindle: 9/16-inch
• Bolt Pattern: 4-Bolt
• Chainring BCD: 64, 104mm
• Arm Length: 170mm
• Rings: 22-32-42T
• Crank / FD Type: Mountain Triple
• Intended Use: Mountain
• Chain Compatibility: 3/32-inch
• Crankarm bolts not included

Thanks for the help so far! I would have messed up pretty good. :)

If you put a M410 (which takes a 113 spindle) on a 110 spindle it will be 3 mm further in, which may result in granny ring hitting the chainstay.

Yeah, well, the only way to get unstupid is to ask questions. Back when I was learning to work on bikes (eek! 30 years ago) we figured out bottom bracket lengths the hard way: we tried them out. If one didn't work, we tried a different one!

Google... phoo...

Not quite. If the crank is put on a 110mm spindle it will be 3/2=1.5mm further in.

So if I am looking at the specs for a replacement crank set, what numbers should I be paying attention to? The Shimano specs state:

FC MODEL # CN SP LGTH 47.5 CN LINE SP LGTH 50 CN LINE SQR TAPER INTERFACE
FC-MC08 110 113 X

then I should be ok swapping in:

Sugino Impel 150X triple mountain bike crankset is 7- and 8-speed compatible.

• 7/8-speed compatible
• Spindle Interface Type: Square Taper JIS
• Spindle Length: 113, 110mm

I just want to be able to do this the first time with out trying to return parts and losing more time.

Thanks everyone again :)

It's tough to say. That Sugino has some giant chainrings by modern standards. Does it seem like there's enough room for your chainstay to accommodate bigger rings?

Do you know the length of your current BB spindle yet?

Yes, the two cranks use the same spindle specs, so you should be fine. I'm not sure what Lester's thinking about, a 22/32/42 is pretty typical these days for a mountain crank, and the same as the MC08 from what I googled, so fit is fine on both counts.

The Impel 150x I saw had 28-38-48 rings on it - totally pre-1990 style. Perhaps they have compact also.

Ah, yes I see some 24-34-42 available now.

Go for the smaller ones to ensure clearance. Unless you need a higher gear and/or run a 13 or 14 small cog in the back.

No, I had Cub Scouts last night w/ my son so by the time I got him home, washed, and in bed it was 9pm and I didn't want to mess w/ it. I have to work job#2 tonight-Fri so I will see how it goes and what time I get off. I have an old CC-1 crank puller so it shouldn't take too long (famous last words)
I do not know if it helps but here is a pic from the Trek Web Site of the bike.

Thanks again.



http://bikeforums.net/attachment.php...hmentid=132914

In his previous post (#8) he's looking at a set with 22-32-42....

Sweet!
 

OK Great news regarding the size!

I didn't have to work so I just snatched the cranks off. I was thinking it was going to be a tougher job than it turned out to be :)

Measuring the spindle questions. Do I need to pull the spindle? I am thinking I will need BB tool for that, huh? Once I get my batteries charged I'll take pics.

I was looking at the chainstay and I have about an inch of room from the 42t chainring to the chainstay. I was thinking about moving up to a bigger one but I'll stay w/ the size I have now to make things easy.

I'm not sure what you mean by "bigger", but size has little to do with chainstay clearance.

What is it you're trying to accomplish here?

Since you're dealing with differences of a few mm, unless you have a caliper that will accurately measure the spindle in place, probably have to remove it. Before you do that, you might check the bb on each end to see if the length is stamped into the spindle.

I have a micrometer in inches I can measure each side w/ that.

No such luck w/ the stamp.

.731" +.676"= 1.407=35.7378 mm

What/how are you measuring? Even if you have a 68mm shell, that only adds up to 103.7378....or 108.7378 for a 73mm shell. What shell width do you have anyways?

I measured from the point where the shaft exited the housing, flush. Then to the outside

I
I___________________
I I
I---------------------------I
I___________________I
I
I<~~~~~.731"~~~~~~>
The shell is the part the BB is house I assume. Ok I'll measure.
Since I had sucess pulling the cranks I went ahead and pulled another from a smaller bike that had Acera cranks with the same tooth count and installed them and adjusted the derailleurs so it would shift. Somewhat anyway. The angle of the chain looked very extreem while on the 42t front ring and the 11t rear chainring. It was very slow shifting too. The front shifted fine.

It measured 2 7/8" which comes out to 50.8 mm but you are right it seems kinda small. The bike is a 21 or 22" bike, so I guess I am measuring wrong.

I really appreciate the time you are taking. Even since I have swapped the other cranks i still would like to have the correct set on the bike. Once I get the correct size I will swap them back. I am trying to get a bike together so I can ride w/ my son on the weekends. My road bike wont cut the dirt trails he wants to ride lol.

Thanks so much again!!

Well, 2-7/8" is 70.8mm so I then checked your other conversions but found those correct...the shell width is just that, the width of the bottom bracket shell of your bike...don't include any part of the bottom bracket cartridge.

PS the size frame has nothing to do with shell width...mountain bikes are almost always 68 or 73 mm shells....