# Bottom Bracket Size for 94' MB4 Bridgestone



## sonypete (Jun 15, 2008)

Hi Guys,
Need to replace the original crankset on my 94' Bridgestone MB4. I would like to goto a external BB bearing. I'm currently having issues finding out what BB size it used. Can anyone recall these stats?


- Pete


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## sonypete (Jun 15, 2008)

Okay after finding out some more details, I think I need to ask a different question. My bike came with an internal BB where as I want to goto an external one. The original was a Shimano STX BB. I think that detail might be irrelevant. 

I think I just need to know the overall BB shell width on my bike (i.e.68,70,73mm). Is that correct?

- Pete


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## theMeat (Jan 5, 2010)

The crank will determine the overall length of the spindle, with a particular frame. Sheldon Brown bb webpage might get you onto some good info.
There's also some very knowledgeable folk on here about Bridgestones so hopefully someone will chime in and save you the homework. 
Post up what type before and after crank to maybe help speed the prosses of finding out.

Pete - "theMeat"


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## laffeaux (Jan 4, 2004)

Yep. Bridgestones had 68mm BB shells. If you want external bearings (not sure why you would on that bike), you'll need to buy a new crankset that uses external bearings and install it as instructed for a frame with a 68mm shell.


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## sonypete (Jun 15, 2008)

laffeaux,
I'm a heavier rider so like to go beefier. I'm looking to get away from the square cranks as I tend to beat them up. But since this is a low budget bike, I will probably go with an internal BB.

After reviewing the sheldon brown site, I see the Shimano STX BB listed with lengths from 110 to 113. I only see 113 length BB online. 

Not sure if any 68 BB crankset in a 113 length will fit my bike.

Any bridgestone guys recently upgrade thier crankset?


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## laffeaux (Jan 4, 2004)

sonypete said:


> not sure if any 68 BB crankset in a 113 length will fit my bike.
> 
> Any bridgestone guys recently upgrade thier crankset?


As "theMeat" said, it's the crank set that determines the BB that you need, not the frame. What cranks are you trying to install?


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## sonypete (Jun 15, 2008)

laffeaux im looking to install a lower end deore or something equivalent. The original crankset is the Shimano STX from 94'

Shimano Deore Fc-M590 Crankset
http://thebikesmiths.com/product/shimano-fcm590-blk-44/

Or something older like below

Shimano Deore Fc-M532 Crankset
http://www.cambriabike.com/shopexd.asp?Item=100040535


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## da'HOOV (Jan 3, 2009)

there's actually nothing wrong with STX stuff....not vintage but totally serviceable.


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## sonypete (Jun 15, 2008)

da'HOOV its has allot of play and the square drives on it don't have much life left in them. They def need to be replaced.

I have no issues going with an internal square tappered BB crankset on the cheap, if you guys can point me to a known compatible set. All the listed cranksets all seem to lack various bits of details I require to feel safe ordering.


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## theMeat (Jan 5, 2010)

Yes Pete that's the issue. Plus more modern bike geo became concerned with a lower "Q-factor", so newer shape/style cranks might not clear your chainstays.
Many early 90's mtbs had wide chainstays (higher Q). Althou it will take a certain size spindle to get the required 47 1/2 - 50mm between the middle chainring and the center of the seat tube for proper front derailleur reach, it might not be enough for the arms to clear the chainstay. So it needs to have the right "dish" and shape to do so. None of the specs for cranksets tell of dish for derailluer reach, or the shape of the arms for clearance of the chainstay. Unless you have a bunch of spindles and cranksets to try out, the best you can do is make an educated guess and buy a crankset from the same time period and hope to be able to get a spindle length that will make both things work for your frame. 

Unless of coarse someone familiar with 94' MB4s will post up a list of cranksets that'll work and the spindle it'll work with. 

Sorry I can't tell you more. Be patient, someone here knows for sure.


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## sonypete (Jun 15, 2008)

theMeat, I forgot to mention, this is a single speed rig so centerline is of a little less concern. Do you have any experience with Bridgestone bike specifically? I guess I could go measure the width of chainstays at the end of the current crank and compare it to my modern bikes. If its super close I might just give it a shot.

I spotted the below parts and want to say the crank arms look like they might fit. I'm just not sure if a 113mm BB will work since the Sheldon site says 110-113 *shrugs*

http://www.jensonusa.com/store/product/CR703A00-Shimano+Deore+Crankset+M510.aspx

http://www.jensonusa.com/store/product/CR703A00-Shimano+Deore+Crankset+M510.aspx

If there are any Bridgestone experts out there I would def appreciate your thoughts. 

- Pete


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## theMeat (Jan 5, 2010)

No Pete, would think you'd be able to figure I'm not a Bridgestone expert since I mentioned it a few times, and after doing alota typing to help your cause I would have just simply said yes or no, those cranks will or will not work.
But now that you finally decided to tell us that it's a SS convert, I will go a little further and say that anything from 110-113 should work, as long as you don't have the other clearance issues mentioned, because with a SS you have a little wiggle room with chainline. 

You're Welcome
Pete "theMeat"


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## laffeaux (Jan 4, 2004)

Shimano STX uses a 110mm to 113mm BB spindle length to have the proper chain line. See info here: 
http://www.sheldonbrown.com/bbsize.html#shimano

Assuming that you can make adjustments to the chain line at the rear wheel, a spindle anywhere near the lengths above will work fine on a single speed. A shorter spindle will be more durable under your weight.


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## laffeaux (Jan 4, 2004)

sonypete said:


> I spotted the below parts and want to say the crank arms look like they might fit. I'm just not sure if a 113mm BB will work since the Sheldon site says 110-113 *shrugs*
> 
> http://www.jensonusa.com/store/product/CR703A00-Shimano+Deore+Crankset+M510.aspx
> 
> http://www.jensonusa.com/store/product/CR703A00-Shimano+Deore+Crankset+M510.aspx


Yes, that crank will work fine. Your frame requires a BB that fits a 68mm shell and has English threads. The crank st requires a BB that has a spindle length between 110 and 113mm.

Bridgestone is noted for using the lowest Q-factor cranks that they could find - so Q-factor is a non-issue on the frame.


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## sonypete (Jun 15, 2008)

Awesome, so basically any english 68mm BB crankset will work. Bridgestone unknowingly made my life that much easier almost 20 years later. 

Also just noticed I double posted links. Below is the actual BB I was gonna get with those cranks.

http://www.jensonusa.com/store/product/BB309B01-Shimano+Es25+Octalink+Bottom+Bracket.aspx


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## laffeaux (Jan 4, 2004)

sonypete said:


> Also just noticed I double posted links. Below is the actual BB I was gonna get with those cranks.
> 
> http://www.jensonusa.com/store/product/BB309B01-Shimano+Es25+Octalink+Bottom+Bracket.aspx


That BB will not work with the cranks that you posted earlier. The crank uses a "square taper" BB, but the BB that you link to is an "Octalink" design (although the dimensions are correct).

There are several types of internal bearing BBs.
- square taper (have a square spindle that attaches to the cranks)
- Octalink (a splined crank interface that fits Shimano-compatible cranks - there are actually 2 different versions of this BB)
- ISIS (a splined crank interface that fits non-Shimano-compatible cranks)

The cranks and BB need to have the same interface in order to work together.

For the cranks that you linked to, you'll need either one of these:
http://www.jensonusa.com/store/product/BB407A02-Shimano+Un-26+Bottom+Bracket.aspx
http://www.jensonusa.com/store/product/BB309F06-Shimano+Un54+Bottom+Bracket.aspx


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## sonypete (Jun 15, 2008)

Yes I know the various BB styles.  The link for the crank lists both styles. You have to manually select the octalink in the drop down menu 

I figured octalink would gain me a little more stiffness and durability long term wise. I find that I get more play on the square tappers sooner then I would like.


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## laffeaux (Jan 4, 2004)

Ahhh... my bad.


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## sonypete (Jun 15, 2008)

Hey laffeaux,
I'm coming across allot of cranksets that only reference the chain line measurement. I know how its measuredfor the BB/chainring, but not sure how to compare it to what my frame might need. Not sure if it as safe as meauring my current chainline and comparing. Doesn't the chainline measurement change if using the same crankset on a 68mm or 73mm BB?


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## laffeaux (Jan 4, 2004)

Chain line is the measurement from the center of your frame to the middle ring position. It's pretty standard on bikes with standard rear spacing. Bikes with spacing wider than 135mm (Manitou, Potts, tandems, snow bikes, etc) need a non-standard chain line.

With square taper and octalink (to some degree) you can vary the chain line by selecting a BB with a different spindle length. Some square taper BBs (Phil Wood, and others) allow for adjusting a few millimeters of chain lines at the BB.

Modern external BBs have no (or minimal) way to adjust for chain line. They work on 73mm shells, or by adding a 2.5mm spacer they work on 68mm shells. If you need something non-standard, you're out of luck.

Your Bridgestone has nothing non-standard about it. It's about as simple as a frame gets. Use the recommended BB for a crank and it will work (regardless of the BB age).

You can measure your current chain line and base your decisions on what to buy on that. If you're going from a triple to a double ring, go with a narrower chain line. The idea is that you want the ring(s) that you use the most roughly aligned with the center of the rear cogs so that your chain runs in the straightest possible line.


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## Rumpfy (Dec 21, 2003)

You are a patient man EL.


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## Fillet-brazed (Jan 13, 2004)

"How big a boy are ya?" Square taper should hold up just fine for most anybody as long as they're installed correctly and kept tight. But ride on them loose and it's over.

Anyway, Laffeaux has done well here.

Oh, and modern cranks are not narrower (Q factor) than old cranks, it's the other way around.


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## sonypete (Jun 15, 2008)

I'm about 245lbs all geared up. I don't mash pedals but put allot of power down so looking for a good solid base. Any extra % in the efficiency department helps especially on a single speed. 

Laffeaux, I appreciate the effort. After reading your post, I guess I just need to quit sweating the details, "just order and go ride", since most matching combos should work.


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## theMeat (Jan 5, 2010)

Pete, glad you seem to be on your way to a solution.



Fillet-brazed said:


> Oh, and modern cranks are not narrower (Q factor) than old cranks, it's the other way around.


Hmm, that's odd. A few years ago I was trying to build up an 88' titanium fisher frame. Tried every crank off every bike I had and either it wasn't even close to derailluer reach or wham, hit the chainstay. I tried no less than 10 cranksets I had on hand. Even thou the frame had a 127.5mm spindle, wham or way too far for derailluer. So after some nice, helpful folk on the vintage forum, and the older mechanic at my lbs set me straight about q and how newer cranks mostly don't work on late 80's - early 90's frames because of it. 
As it turns out, I bought an older, period correct crankset and walla. it fit.
I realize that as rear axles went from 130 to 135 it made the chainline wider, and the triple chainring obviously did also. All the cranks I tried on that older frame where from 95' to 07'. I thought I had it figured, so please, I'm not being a smart ass or sarcastic, I'd just like to know, enlighten me


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## tductape (Mar 31, 2008)

Per Sheldon:


The tread, or "Q factor" of a crank set is the horizontal width of the cranks, measured from where the pedals screw in. The wider the tread, the farther apart your feet will be. It is generally considered a good idea to keep the tread fairly narrow. There are three main reasons for this:

The hip joint is optimized for walking, and in normal walking the footsteps are pretty much in line, with little or no "tread."
For standing pedaling, the farther out the pedals are from the centerline, the harder you have to pull on the handlbar to counterbalance the tendency of the pedaling force to tip the bike sideways.
The wider the tread, the higher the bottom bracket needs to be to prevent clipping a pedal while pedaling through a turn.
Older bikes were generally designed to keep tread to a minimum, but starting in the late 1970s there has been a trend to wider tread, for a variety of reasons:
The popularity of triple-chainwheel cranksets has moved the right side outward.
Front derailers designed for triple-chainwheels have a more 3-dimensional shape to the derailer cage, which requires more clearance between the large chainring and the right crank.
Mountain bikes have wider-spaced chainstays for tire clearance, which requires moving the chainwheels outward so they won't hit the chainstays.
Newer bikes with more sprockets in back move the chainline outboard.


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## theMeat (Jan 5, 2010)

Thanx Aemmer for posting that. I'v read that before and



theMeat said:


> I realize that as rear axles went from 130 to 135 it made the chainline wider, and the triple chainring obviously did also.


among other reasons you posted. That read doesn't explain it thou. I know I'm not always the brightest bulb in the box but just don't get how if more modern cranks got wider, why none of them would fit on my older frame even thou it had a 127mm spindle and why I HAD to get an older period correct crank to clear the chainstays if that's the case......?

anyone?


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## Fillet-brazed (Jan 13, 2004)

theMeat said:


> Thanx Aemmer for posting that. I'v read that before and
> 
> among other reasons you posted. That read doesn't explain it thou. I know I'm not always the brightest bulb in the box but just don't get how if more modern cranks got wider, why none of them would fit on my older frame even thou it had a 127mm spindle and why I HAD to get an older period correct crank to clear the chainstays if that's the case......?
> 
> anyone?


There are lots of variables in square taper crank arms, some are designed to use a really wide spindle (ie TA cranks and the like) and then there are the later versions (ie M900 or compact XC Pro) that were called low profile that used roughly a 10-20mm narrower spindle while achieving the same Q.

I don't have any web references with measurements handy, and I haven't taken any measurements, but I know when I go from my bikes with square taper cranks to my modern bike with XT or XTR cranks it's noticably wider.

One other thing, with square taper you can change the spindle length based on chainstay clearance and on many of mine I've run as short as a 107mm spindle. I always try to get them as narrow as possible. With the new two piece cranks you're stuck in a very wide stance that Shimano knows will fit on pretty much _any_ bike.


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