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Experts to the square taper phone please

2771 Views 36 Replies 20 Participants Last post by dRjOn, Dec 8, 2005

Cloxxki

Discussion Starter · Dec 6, 2005

My deal : I have a saweeet 2005 paragon frame I'm trying to build up, and I'm dead-set on using the silly TA 185mm cranks I have for it. After long searching, finally Dave Blum from these forums was so cool to just sent me his, gratis! (and that's a Dutch word), thanks Dave! He also inclused a Phil Wood 125mm without telling me, which will sure work well on another, similar project.

Now the problem : the Paragon is obviously made for modern wide chainlines and 22/32/44 chainrings, understandably.
34t middle ring, with the 127.5mm BB, is already too much. Cranks close to the chainstays BTW. So I put a spacer under the driveside BB cup, and that helps. I might get away with a thinner spacer too, but anyway the left side crank is really close to the chainstay, and might even hit it under power.

I'm really dead-set on using this BB and crank combo, so please be nice to me.

Question : can I warp or fold something around the non-driveside BB spindle taper so the crank doesn't slide onto it aaaaalllll the way? The taper is quite shallow obviously, so even the slightest (o,1mm?) thickening of the spindle would give me a very welcome mm of extra clearance, or more. I *think* I've seen people using some sort of copper tape in similar applications, but am not sure. I could also craft something from a coke can, like 2 thin strips with a bolthole or something.

I KNOW it's not an a-status setup, but what can you think of to make this work just a little better?

I already have a 34t middle ring, 33/44t would be ideal (but costly) so I could cannibalize a 42t outer from a cross bike. The 26t granny I planned to use looks like too much to ask for, but a 24t may alrady be on it's way from I friend I had an outstanding favor with.

Unfortunately I'm building this bike, which will be a disc(disc-only, duh) hardtail for general use, rough XC and marathon), on a negative budget, making it a slow process. Else I'd have just gotten a $300 custom 195-200mm crankset for it, with more practical BB compatibility. Someday...

Thanks for you insights!

J

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eric

· #2 · Dec 6, 2005

Yo Cloxxki

Whaddayamean "34t middle ring, with the 127.5mm BB, is already too much"?

Are you saying the cranks are too close to the chainstay, but the rings are too far out? Or are the rings too close, too?

dompedro3

· #3 · Dec 6, 2005

not sure if it will help, but i've always used teflon tape over the tapers when my sq tapers creaked too much..a couple layers may give you the space you need...

Cloxxki

Discussion Starter · #4 · Dec 6, 2005

Eric, 34t ring running into the chainstays. Whatcha lurking on the adult wheeled forum for?

Teflon tape, good to hear that at least worked for someone before. thanks!

Other types of tape or material to consider?

dRjOn

· #5 · Dec 6, 2005

teflon tape? wow, thats brave...

if you think about it the cranks are only rea\lly under flexing risk at the end of the stroke (ie pedal at the bottom) so if there is some clearance at chainstay, it should be fine...

as for spacing the cranks off the spindle with a shim, i guess some formed steal if it was hard enough would be ok, otherwise you are asking for movement...and creaks...why not use a smaller ring than 34? or spcae the ring out on the cranks with washers?

Cloxxki

Discussion Starter · #6 · Dec 6, 2005

33t would help yes, but smaller doesn't exist for 110mm chainrings. Spacers will only bring the ring in closer.

~martini~

· #7 · Dec 6, 2005

I did read that Shiggy suggested slicing off a section of soda(or beer) can and installing that on one or two of the tapers. He suggested this for a wallowed out crank solution though, so it may not be appropriate in this case.

I suppose he could go down to a 33, but finding a 33 is hard. Since this crank is 110 spacing, he really can't go smaller than that.

dRjOn

· #8 · Dec 6, 2005

what sort of crank? can you not mount the ring in the outer ring position?

MtotheF

· #9 · Dec 6, 2005

p*ssing in the wind

you might be on a lost cause here cloxxi, unless you want to consider somehow flattening the chainstay to get more ring clearance (which can be done with steel frames, but i would be loathe to do that to aluminum). if the bike was designed around modern compact cranks, and you are using some dead flat TA's from the time when chainstays had little to no manipulation, and want to run old school larger rings, then you might just be banging your head against a wall.

i would strongly advise AGAINST wedging anything between the crank and bb spindle (teflon tape is acceptable in some cases, but anything more serious is just asking for failure). how wide a spacer do you have beneath the drive side bb cup? i have gone out as far as 3mm on some bikes, but only when the cup and shell have plenty of threads left. if you are using up half or more of the available threads with spacers, STOP! you need to have enough thread to clamp things down tight without stripping threads. bear in mind that as you space the drive side outward, you are also screwing up your chainline.

also, think about this: you are a very tall, very strong rider. your cranks are the conduit for ALL your power and leverage. right now you are contemplating some pretty serious compromises to the performance, strength, and reliability, of a crucial central component of your crivetrain, for what are basically aesthetic reasons.

think hard.
mf

dompedro3 said:
not sure if it will help, but i've always used teflon tape over the tapers when my sq tapers creaked too much..a couple layers may give you the space you need...

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Cloxxki

Discussion Starter · #10 · Dec 6, 2005

I'm using a 2mm or so spacer, could try 1mm also, but if I can get away with the present spacer, I will.
Teflon tape, whatever that is, looks like something to try! The BB has quite a few threads left, but thanks for keeping me sharp!
I've heard before that someone's cranks would clean the chainstay in the repair stand, but on the trail would hit. Frame flexes a bit too of course. Even it I'm barely clean, I'd gladly win a mm. It's about everything being close, not impossible

eric

· #11 · Dec 6, 2005

Git y'r hands on a tandem bracket!

Don't tease me about my wheels. Smaller wheels leave more room for the mind.

Scour Marktplaats.nl. You often see goofy BB-units pass the review there, so if you can find a wide BB there you won't be spending a ton of cash, either. I don't know how wide Shimano goes (127 mm I thought) but Edco - among others - goes even wider.

dRjOn

· #12 · Dec 6, 2005

has anyone actually used teflon tape to good effect. i mean, its use is to seal (against water at pressure) plumbing connections, it is deformable and slippy right? so why would you want to put it between a friction joint?

MtotheF

· #13 · Dec 6, 2005

okay

the teflon tape probably won't give you much room, and it is quite possible that your chainline will be so far outboard that you will be plagued with chainsuck, but if you have room to space the bb further over, you can try that. if the crank hits on the left, you can CAREFULLY shave the backside of the left crankarm down a mm or two.

BUT, bear in mind that your cranks flex quite a bit, especially long ones. i recently built up a bike with plain ol' 175mm cranks, and had to space things out for ring clearance issues (same deal, running large 110bcd rings on a new compact specific, wide tire clearance, frame). ended up with teh left crank clearing the frame by about 1.5mm. it hit whenever i pedalled with any conviction. in your case, given your size, the length of your crankarms, and the noted flexiness of TA cranks, i would want at least 3mm clearance, at the minimum, for your left crank.

Cloxxki said:
I'm using a 2mm or so spacer, could try 1mm also, but if I can get away with the present spacer, I will.
Teflon tape, whatever that is, looks like something to try! The BB has quite a few threads left, but thanks for keeping me sharp!
I've heard before that someone's cranks would clean the chainstay in the repair stand, but on the trail would hit. Frame flexes a bit too of course. Even it I'm barely clean, I'd gladly win a mm. It's about everything being close, not impossible

itsdoable

· #14 · Dec 6, 2005 (Edited)

I'd advise looking for a wider BB. I don't advise shimming the taper, you are asking for trouble. However, if you must, and you don't mind experimenting, go pick up a package of assorted brass shims (machine shop equipment, not expensive) and start with the thinnest, make sure you shim all four surfaces identically.

MtotheF

· #15 · Dec 6, 2005

yup

itsdoable said:
I'd advise looking for a wider BB. I don't advise shimming the taper, you are asking for trouble. However, if you must, and you don't mind experimenting, go pick up a package of assorted brass shims (machine shop equipment, not expensive) and start with the thinnest, make sure you shim all for surfaces identically.

agreed on the wider bb, by the way (but not the taper shims). after all the babble i just posted, i noticed that TA/stronglight make 131mm bb's. didn't search any further. sounds like a much smaller headache...

shiggy

· #16 · Dec 6, 2005

~martini~ said:
I did read that Shiggy suggested slicing off a section of soda(or beer) can and installing that on one or two of the tapers. He suggested this for a wallowed out crank solution though, so it may not be appropriate in this case.

I suppose he could go down to a 33, but finding a 33 is hard. Since this crank is 110 spacing, he really can't go smaller than that.

I used the blade of a steel measuring tape. Very hard and brittle stuff.

Chequama Mama

· #17 · Dec 6, 2005

At the torque you must be able to put onto the cranks (given your race results and non-featherweight build) I would be really uncomfortable modifying the crank/bb interface, especially for race use. If this was an around-towner, I would say go for it, and let us know how it goes, but you don't want this failing on you in the middle of a race.

I did a bit of looking on sheldon brown and am also relying my memory, which might be a bit dangerous.
I would join in advising you to look for a wider BB setup. Harris cyclery has some TA stuff. But being in Europe, you might have an easier time tracking down the parts you need there, for less cash.
I don't know or remember which type of TA crank you're using, but two bits that you probably are already be aware of:
1. Some TA cranks need a different puller (the backside of the park puller)
2. According to Sutherlands, the taper on stronglights is shorter, and so you'll end up going too far onto the spindle and bottoming out the crank bolt. If this is the case with your cranks a proper BB would push the cranks out a bit on the spindle, so you might get away with a 127 spindle, though 133s are also available.

YO MAMA

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Cloxxki

Discussion Starter · #18 · Dec 6, 2005

All good thoughts, thanks.

Hardest part in finding a BB for me WAS (I have the BB now Eric) the Fisher using a 73mm BB shell. Some suggested milling it down, and that was my first thought, but the welders really made use of the available BB width, and milling down welds...nah thanks!

Shiggy, for what job did you use that method? Did it hold up? I can see myself cutting some exactly fitting pieces from a coke can or indeed measuring tape, keeping the solid corners of the square axle in use without any tape.

Once I find a 33t somewhere (as cheap as myself), I'll be able to narrow the driveside spacer and get some clearance back on the left.

Note to self : design a 2-part axle that threads together, for custom widh and spacing. Now where does one buy a CNC machine cheap?

MtotheF

· #19 · Dec 6, 2005

but...

well, at least we tried to warn you.

or was there some part of "shimming cranks to bb spindles is a very, very bad idea" that somehow got lost in translation?

whatever. there are cheapass chinese cup and cone 73x131 bb's out there in spades. and you could easily use a 68 x131 without any real weirdness. but if you want to do it the worst way possible, and maybe ruin those cranks you are so attached to, go right ahead. post pics, and keep a log!

ta

Cloxxki said:
All good thoughts, thanks.

Hardest part in finding a BB for me WAS (I have the BB now Eric) the Fisher using a 73mm BB shell. Some suggested milling it down, and that was my first thought, but the welders really made use of the available BB width, and milling down welds...nah thanks!

Shiggy, for what job did you use that method? Did it hold up? I can see myself cutting some exactly fitting pieces from a coke can or indeed measuring tape, keeping the solid corners of the square axle in use without any tape.

Once I find a 33t somewhere (as cheap as myself), I'll be able to narrow the driveside spacer and get some clearance back on the left.

Note to self : design a 2-part axle that threads together, for custom widh and spacing. Now where does one buy a CNC machine cheap?

AKamp

· #20 · Dec 6, 2005

I have used soda can shims before but I wouldn't on my own bike. I have pretty much only done it when someone would come in the shop with no money and a need to get back on the bike. I wouldn't recommend it over spending the money for a new BB. If you have a phil you could always just buy a new spindle and replace it in the BB. I think that would really be your best bet. I would hate to see you screw up the taper on your crank. And have you ridden the bike yet, it is possible that you won't get enough deflection in the system to hit the chainstay even though it is close. My cranks are about 3 mm from the CS and even though I can get them to meet if I really think about it, they never do in actual riding.

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