plonz 

I have 3 sets of cranks I will be installing in the near future and don't have bottom bracket specs for any of them. I can determine shell width and taper but I struggle figuring out what spindle length I need. Is there a way to determine this through measuring? I'm assuming you'd try to calculate what it would take to get 43.5mm chainline but I'm not sure how to go about doing this without being able to properly mount the cranks.

Up to now I've poured through pages online looking for this information. I've managed to get close this way but too many times it's through trial and error with multiple BBs. I'm certainly open to a more effective way of doing this. Thanks for any help!

ramzilla

I've never been able to measure axle length until after both crank arms are removed. And, you need to pick up a cheap caliper measurement tool. Get one that's about the length of a dollar bill - around six inches or like 150- 175mm. You can get one on ebay for about ten bucks.

plonz 

Thanks for the reply but I don't think I was clear enough on my original post. I have to buy a new bottom bracket and need to know the correct spindle length. I've never had the cranks mounted and don't have the old bottom bracket to measure. Appreciate the help.

wrk101

Choice 1: Check Sheldon Brown listing of cranksets and their spindle length. Not every crank is listed.

Choice 2 (what I do): keep a variety of UN26 BB, available on line for $10 each, and use trial and error. Also need to keep a handful of spacers to mimic asymmetric spindles on older bikes.

Steve Whitlatch 

What about Velobase? They list the spindle measurement for each crank set. Is that a good place to look or does each frame model have a variation? I am interested in knowing because that is what I used as a guide?

Slash5

I always keep old cartridge BBs that I remove just for testing width. In theory just about any BB can be used to check as long as the chainring doesn't hit the chainstay.
Install a BB and measure the chainline and measure each crank arm to chainstay distance. That will tell you if you need to shim and what length of BB you need for the correct chainline.

noglider 

I am coming to believe there is no art to this. I've only done it by trial and error. If you have a double crankset, 113mm is a good place to start, but no guarantees.

verktyg 

Velobase is a great site for finding cycling related information. There's good stuff that you may not find anywhere else but just like wikipedia there's some urban myths and wrong information posted by a few contributors.

Listmaster Jon Fischer does a good job of monitoring the submissions but it's hard to know everything about bikes. Like wiki, corrections and additions are submitted by other users.

@wrk101 - Sheldon Brown's website has a lot of good information too but without knowing the make and models of the cranks in question everyone is just guessing....

verktyg

Chas.

plonz 

I was figuring that's how this might end up. 113 seems like a good middle ground but question for you: How precise do you have to be? For instance, if the spec is 109 but I use a 113 would I feel this and/or would I likely have shift issues?

Bad Lag

I don't think you need more than one basic (cheap) bottom bracket set to start with. Use that cheapie BB with your crank set. Measure how far off line you are. That offset plus the dimensions of the cheapie will get you there.

I may do this because I've been wanting to convert to a triple crank and will almost certainly need a new BB.

verktyg 

@plonz It would help to know the make and model of the cranks in question plus the BB shell width. Some pictures would be even better.

A few years ago I was putting together a single speed beater using an old Gitane Interclub frame with a French BB.

I'd been down the road of matching cranks and BBs for ~40 years. I decided to document some of the steps that I went through on this project. Here's a link to my Flickr album that may give you some ideas:

https://www.flickr.com/photos/282672...57627678462359

Click on the pictures and read the descriptions below them...

EDITORIAL COMMENT:

All of the crap about ISO, JIS, Campy, French, Japanese spindle tapers is just that!!! In the 1970's Phil Wood made "one size taper works with all" cartridges. They worked fine most of the time!

1. Once a crank arm has been torqued onto the spindle, the soft aluminum alloy deforms to fit the spindle taper. More so with crank arms that have been removed and replaced a number of times. Factor in used cranks that have been run loose and that the magnifies the problem.


2. These are/were BICYCLE parts not Swiss watch movements! The manufacturing tolerances in the tapered square mounting holes in the crank arms plus the small end measurements and lengths of the tapers combined with the overall spindle lengths vary substantially within the same make and part number! I've known this for many years but never documented it.



I measured all of these BB spindles and cartridges in this box plus a lot more. They were various Campy, Ofmega, Avocet, Shimano, Suntour, SR, Sugino, TA, Stronglight, Phil Wood and other brands.


3. If it fits, it works! These views show the proper crankarm fit on the BB spindle taper




4. Fitting the spindle to the BB cups presents some additional issues. The balls should run in the center "ball track" - not too high or too low. The second picture shows the proper ball contact area.




5. So how do you determine what's going toi fit?

The easiest was is to get the correct BB and spindle that matches the crank arms - no guessing or trial and error!

When that's not practical, get a pair of 1/4" caged ball bearings. Clean ALL of the grease off. Get a pair of cups and a spindle and do the same with them. When all of the parts are clean and dry, take a magic marker and cover the ball track area on the spindle and both cups and let dry (you could use a product called ****m Layout Fluid too).

Assemble the BB with the dry components by hand tight enough to take up the slack. Rotate the spindle a few times and take the BB apart to check the ball contact areas on the parts. If everything looks good put it back together by hand again.

Slide the crank arms onto the spindle and check to see how well the fit -see drawing above in #3 . Keep in mind that when you torque the crank arms onto the spindle at 20 to 30 Foot Pounds, they will seat 1mm to 3mm further onto the spindle.


6. The small chainring should clear the chain stay by about 4 to 5mm, depending on small chainring diameter and any clearance flat on the chainstay.

Every time you remove and replace the crankarm it will seat a little further onto the spindle. Also the crank arm bolts should be re-torqued after 50-100 miles of riding depending on the rider's weight, strength and style of riding. That seats them further onto the spindle too.

If a bike gets used a lot the crank bolts or nuts should be frequently checked to make sure they haven't worked loose. Squeaking or creaking when honking up a hill is a good (bad) sign that the crankarms need to be retightened! Continued riding with that condition will end up trashing the taper in the crankarms. That's why used cranks should be carefully checked for damaged tapers.

The 4-5mm figure is a "WAG" (wild assed guess) but gives wiggle room for future crankarm re-seating on the spindle plus it allows for switching to a larger inner chainring.

Another point, a frame with short chainstays a 130mm rear hub and larger inner chainrings will run out of clearance a lot faster than one with 120mm or 126mm rear dropout spacing and longer chainstays.

If there's not enough clearance or if the crankarm sticks out too far you have to use a different spindle or BB.


7. Q-Factor like chain line is another throw back affectation... Q-Factor is a one size fits all fit fascist fantasy...

Chainline was a Brit obsession when they used SS and internal hub gears with stiff 1/8" chains. In mid 70's 3/32" bushing-less chains became the standard. They have a lot of lateral flexibility so chainline is much less of a concern!

verktyg

Chas. Breaker of hearts, destroyer of myths and seeker of truth!

dicktill

WOW, excellent technical description AND great drawings. Thanks Chas!

plonz 

Wow that is some great information. I especially like your comments on #6 . If I read this correct, as long as the chainring clears the stay by 5mm and doesn't extend past the derailleur movement, there is a bit of wiggle room in chainring and Q-factor allowances.

My current conundrum is with a late(er) model SR Suntour Superbe crankset that I picked up from forum member @guygadois. He pointed me in the direction of a Shimano UN55 but does not know the spindle length. I have also emailed SR Suntour and will try calling them as well. In the meantime I was asking to see if there was a way for me to just figure this out on my own. I do have a couple of spare BBs so I can assemble one and start measuring from there.

Here is the sellers pic of the item. They look a lot like vintage Superbe cranks but I'm not assuming same dimensions. Frame shell width is 68mm. Thanks for the help!

wrk101

5mm guidance above is an opinion. You will find others using less clearance. Some guide that 2mm is enough. At some point, you can get a little flex and the chainring will rub against the chain stay. At that point, you need more clearance.

RobbieTunes

+1

RobbieTunes

Tried that, failed that, with a square taper Athena on a Suntour BB.
Am somewhat in the same boat now with an Italian frame I want to run Suntour cranks on, which definitely will not work on an Athena BB.

Ordered a UN55 with Italian threading. We'll see how it works.

Just a note on the 5mm clearance. I am restoring a 1985 Raleigh, and simply pulled the R crank arm off. It will not go back on as close to the BB as it was before. I've filed any possible burrs inside the crank arm and on the spindle, and still, I'm about 2-3mm farther out than I want to be. I have no idea why.

verktyg 

@wrk101 I rewrote line 6:

"6. The small chainring should clear the chain stay by about 4 to 5mm, depending on small chainring diameter and any clearance flat on the chainstay.

Every time you remove and replace the crankarm it will seat a little further onto the spindle. Also the crank arm bolts should be re-torqued after 50-100 miles of riding depending on the rider's weight, strength and style of riding. That seats them further onto the spindle too.

If a bike gets used a lot the crank bolts or nuts should be frequently checked to make sure they haven't worked loose. Squeaking or creaking when honking up a hill is a good (bad) sign that the crankarms need to be retightened! Continued riding with that condition will end up trashing the taper in the crankarms. That's why used cranks should be carefully checked for damaged tapers.

The 4-5mm figure is a "WAG" (wild assed guess) but gives wiggle room for future crankarm re-seating on the spindle plus it allows for switching to a larger inner chainring.

Another point, a frame with short chainstays a 130mm rear hub and larger inner chainrings will run out of clearance a lot faster than one with 120mm or 126mm rear dropout spacing and longer chainstays.

If there's not enough clearance or if the crankarm sticks out too far you have to use a different spindle or BB."


@wrk101 "At some point, you can get a little flex and the chainring will rub against the chain stay. At that point, you need more clearance."


I'm lazy!

Many years ago I realized the old adage - "Do it right the first time!" was true!

It's a lot easier spending a little extra time and effort than repeatedly redoing a repair!


verktyg

Chas.

verktyg 

HISTORY LESSON...

From an article "Sundown for Suntour" by Frank Berto:

https://pages.citebite.com/o2n1u6u4w3qui

"In late 1989, Mori Industries Inc., a Japanese steel tubing company, bought Sakae Ringyo Ltd. ...In mid-1990, Mori bought Maeda SunTour. ...Shortly afterwards, Mori combined the two acquisitions. The new company was named SR SunTour."

Around 1991 SunTour changed from a Japanese company based in Osaka to a Taiwan company.

"...Mori decided to shut down their bicycle component business in March, 1995. Daisuke Kobayashi and Hideo Hashizume, the former owners of SR Sakae Ringyo, arranged a management buyout. ...They bought the SunTour name and the SR factory in Taiwan."

The current SR Suntour is related to the 2 Japanese companies in name only.


I did some searching for SR Suntour BBs. Apparently the company is primarily producing suspension forks and modern cranks that use a different style BB than the square taper standard. Their website says that the square taper cranks that they do make fit "square taper spindles" with no other information.

Good luck getting help from them....


They look like beefy cranks. It looks like a lot of those SR Suntour Superbe cranks have been hitting the market for the past 5-6 years with no reference to matching BBs!

BTW, the early Suntour cranks were made by Sugino...


Back to basics...

I'd start off finding a BB spindle or cartridge that properly fits in the crankarm taper:



Next, measure the size of the small end of the taper and the length of the taper. That's a good starting point.

Then, work out the spindle length.

A bike co-op or similar operation might be a good place to look for spindles.



The Shimano UN55 cartridge BBs are very good (the old UN72 BBs were better, the UN26 BBs have plastic left side cups). It looks like Shimano started making the UN55 BBs again at their Singapore operation. The last time I checked they were available with British threads in a wide range of widths. I bought a bunch of them for ~$25.00 last year.




Another suggestion would be the Campagnolo Veloce cartridge BBs. They are/were available with British or Italian threads in 111mm and 116mm spindle lengths. I bought a bunch of them too, for ~$15 to $25 USD.



They were made for Campy Veloce, Mirage, Xenon and Centaur Cranks. I've used them with Campy Victory and Triomphe cranks plus I have them on several bikes with late 1980's Suntour Superbe Pro cranks.



The Veloce BBs were made in 3 styles:

AC-H - Aluminum Cups with hollow steel spindle

AC-S - Aluminum Cups with solid steel spindle

SC-S - Steel Cups with solid steel spindle


The ultimate solution is a Phil Wood BB. You have about about 5mm of wiggle room on the drive side.

Good luck...


verktyg

Chas.

plonz 

@verktyg, thank you again for some great info. I have a couple of BBs laying around so I'm hoping to luck out and get one where the taper fits. I'll install it and measure to figure out how much shorter or longer I need to be to get my chainring clearance. I'll factor in chain line as well.

Also thanks for the Veloce references. I may take a look at that AC-H. It is going on my Olmo San Remo and I hope to keep this bike <22 lbs so weight is also a consideration. My experience with the typical $20 BB cartridge is they weigh a ton.

verktyg 

They weigh a ton....

BTW, I stopped weighing my bikes years ago... On hard climbs, the bike's wight was all that I used to think about! Ride and handling are what's important to me now.

verktyg

Chas.

richardalan

In my experience, this is very true so long as the BB spindle is symmetrical.

plonz 

I attempt to ride my C&V bikes with speedy groups and an extra 2-3 pounds make a noticeable difference. My 23+ lb Bridgestone is a real challenge to keep pace vs my 21+ Lb Raleigh. The big difference between these two is in rotational mass so I'm mostly focusing on wheels, cog and cranks.

verktyg 

@RobbieTunes bear with me and I might have an answer for you.

Short course on BB spindles...

The 1st section covers traditional square taper bottom brackets with cups and loose or caged ball bearings.

The highest quality BB spindles were made from high quality alloy steel or bearing steel.

They were fully machined from bar stock in an unhardened condition to near finished dimensions. The shape of the bearing races and the 2° tapers were cut on both ends. Bolt holes or through holes were drilled and the threads were tapped. The 2° tapered flats were machined in another operation.

The spindles were then heat treated to a high temperature and quenched to either through harden or deep harden them, depending on the type pf steel. The spindles were hardened to about 60 Rc. (Rc stands for the Rockwell C Scale which is a measure of hardness - for example, hand files are about 55 Rc, metal cutting tools like drills taps and so on are 60 to 68 Rc)

The last steps were to precision grind the bearing races to size (which can leave a polished finish). The flats were finish ground too.

Campagnolo Record, Nuovo Record, steel Super Record, C-Record, Chorus and some of the others were made this way.



Suntour G1 top quality Spindle ???



A few other companies produced BB spindles with the same quality.

The flats of many BB spindles were not finish ground after hardening which could leave a rough surface that can cause the soft aluminum to gall on tapers and the arms may not seat properly.

@RobbieTunes this may be your problem...

Check out the cutter feed lines on these tapers.

Avocet/Ofmega spindle



Lower quality Suntour Spindle



Stronglight from the 1950's



Later Stronglight 118 Spindle



TA 344 Spindle



Some other methods used to form the basic spindle shape are:

Hot drop forged blanks - this leave separation lines from the forging dies in the mid section.

Hot roll forging reduces the amount of machining. The complete rough shape including the tapers and flats can be done in one operation.

Roll forged Stronglight spindle for lower priced cranks like the TS, 100, 200, 104 etc.



Continued in next message....

verktyg

Chas.

verktyg 

To be continued...

verktyg

ThermionicScott 

At the risk of stepping on your toes, as they say, you can leave test-adjusting the derailleurs for much later.

All you really need to do is thread on one of those $10 cartridge BBs hand-tight (don't bother with the NDS cup), place the crankarms on the spindle and slap the mounting area with your palms to get them started. From there, you can gauge the chainline and clearance and subtract a couple mm to account for the cranks moving inward when they would be torqued down. Obviously, if things are almost touching with a particular BB, you know it'll be too short with everything properly installed, and conversely, if everything is hanging way out there, that it'll probably be too long.

The nice thing about this method is that it won't put any wear/squishage on your crank tapers. And it lets you figure out the ballpark BB length and then remove everything by hand to try again, or install everything for real.