Velocivixen

I know technically this should go under the bike mechanics sub forum, but am posting here because I like you. It's a vintage bike. If mods feel the need to move this post then pardon me and go ahead.

I have a 1987 Miyata One Twelve with a 42/52 SR "Signature" crankset. The bottom bracket shell on this bike is 68mm


I recently bought a 1987 Miyata Velley Runner (frame is toast, but kept all the parts) which has the exact same SR "Signature" crankset but in a triple (28/38/48). The bottom bracket shell on this bike is 70! The spindle is 129.5 mm. I also have the appropriate front & rear derailleurs for the triple as well as shift levers (the ones on the mixte will work with the triple derailleurs).

I want to put the triple on to the mixte, but the bb spindle will be an issue because of the bb shell differences 68 vs 70. I know I could try the spindle for the triple in my mixte, but I'm certain that the adjustable cup won't grab enough threads to make it work. Anyway, is there a way or do you have any reasonable guesses as to what spindle length I'd need to make this work? Would I just go to the co-op and get a 68 x 129 mm spindle? I know some would say "trial & error". I understand that the distance from the fixed cup out to the end of the spindle is the important number to maintain for the chainrings. Just not sure of the math or ???

In the meantime I replaced the 42 chainring with the 38 chainring, put the 14-30 freewheel on the mixte as well as the long cage version rear derailleur. So I currently have somewhat of a vintage "compact double"!!!!

juvela

to get a good chainline all you would need to is to place a 1mm spacer behind the fixed cup and you can use the 3x spindle for 70mm shell. you will have about 1mm of threads showing on the adjustable cup.

Velocivixen

@juvela - Thanks! I may just give that a try!

I rode the Mixte around this morning with the new 38/52 chainring + 14-30 freewheel and the lower gearing was nice. I may just leave it as is and see how it goes. I think the vintage 42/52 was nice on road bikes when people wanted to go fast. I like having the 52, but just felt the need to have something lower. Ultimately a 36/50 would be nice.

Thanks for responding to my question. Cheers.

juvela

best o ' luck wit it!

ThermionicScott 

@Velocivixen, that looks an awful lot like a 110 BCD crank. I bet you could install 50/34 rings (or 48/36, or whatever combo you like) on that thing without messing with a crank swap.

The Golden Boy 

*blush*

I don't know anything for sure- but I hear it often recommended to use one of the sealed Shimano BBs.

Velocivixen

@ThermionicScott - yes, I think I will leave it either as 38/52 or 38/48 because those are the chainrings I already own and am cheap.
@The Golden Boy - Yes, those UN-55's are nice. Just really trying to be creative with what I already own for now. I'm still figuring it out. I have my Nishiki Riviera, which is also a 42/52 with 14-28 rear, so it could be nice to have something a little different.

ThermionicScott 

If those chainrings do what you need, more power to you! I've been running 48/38 on one bike for a while but just switched to 50/38 for more range, and it's kind of a goal at this point to honestly wear out a couple before buying more to fiddle around with.

Sixty Fiver

Can you double check your bottom bracket measurements ?

70mm suggests an Italian bottom bracket which also has a larger inner diameter than a BSA (standard).

Swapping to a triple is not that hard, you will need a long cage rear derailleur and the right bottom bracket for proper chain line.

Wulf

I have a 68 mm tripple spindle - Campy NR that I would like trade for a double.

Velocivixen

@Sixty Fiver -I'm positive it is 70 mm bb shell and the two spindles side by side demonstrated a difference between distance of races. I read Sheldon Browns cribsheet for bb and mine is not Italian. It is standard threading except for bb shell. Research indicates that some Japanese manufacturers made bb 70mm. So who knows why? I did online search of "'80's Miyata bb 70 mm" and found others with same issue.

Anyway, I rode about 12 miles with the new 38/52 and really liked the 38 chainring. Don't know that I'll go so fast as to benefit from a 52, so may go 38/48 and keep the 14-30 cluster. I am not one who shifts frequently. Guess I don't care about my cadence. If I'm going up a hill I, of course, anticipate and shift to a lower gear, but on flat land I just pedal harder vs shifting all the time.

Uncle Randy

Is it possible to use a sealed cartridge for a 68mm shell and adjust for the 2mm difference with the mounting rings?

Velocivixen

@Uncle Randy - sure I could do that but I am trying to use things from my relatively modest "parts bin". I like to try different things out to see what works, see if I can accomplish something with what I've got. I live in a town that has several bike co-ops, so finding a spindle should not be a big deal. By the way, how'd you choose your name? Are you someone's uncle?



If I get a spindle that is meant for a 68 mm bb shell does the OVERALL length of the spindle need to change? Like decrease by 2 mm or ? Want to keep the correct chain line.

Uncle Randy

I have 3 nephews and 1 niece, Velocivixen.

I used one of these $13.98 68x127 cartidges on my aluminum frame Fausto Coppi. Since the shell on the One Twelve is 2 mm smaller it seems like you could use a shorter spindle, but I'm not an expert like these other guys.

Andrew R Stewart could answer your question.

Sunlite SL 26 BB Bike Cartridge Bottom Bracket English Square Taper 68mm x 127mm | eBay

Uncle Randy

I didn't realize the Valley Runner was a mountain bike. These threads might have some useful information:
https://www.bikeforums.net/bicycle-me...-roadbike.html
https://www.bikeforums.net/bicycle-me...d-cx-bike.html
https://www.bikeforums.net/bicycle-me...-crankset.html

jyl

I applaud this practice.

intransit1217

Help you make a mixtape ? Wait, what? Oh. Make your mixte a triple! Sorry, can't help you with that. Can't help with a mixtape, either.



I'll go away now.

Velocivixen

@intransit1217- haha! I remember making mixed tapes! Off the radio no less.

This is the triple from Miyata Valley Runner Mountain bike - 28-38-48. Brand is SR "Signature" model 307 I believe. It's spindle is 70x 129.5



Here is the Miyaya One Twelve Mixte which has 68mm bb shell & currently has a SR "Signature" double (42-52 - which I changed to 38-52).



I just just want to know, what length spindle to get. Shimano UN55 has 68x127 so that's gonna be longest spindle, but how do I know, in advance, if that's the best length without trial & error? I can't go out and buy a bunch of used spindles to try.
@Uncle Randy- thanks for those links. I'll look at those shortly.


As an aside, Miyata had three dedicated touring specific bikes that year, and their lowest touring model, the 215, came in a Mixte AND used this exact same triple crankset, so Miyata was mixing & matching some components. So I'm not off my rocker to think this will work.

Uncle Randy

Maybe @wrk101 can help, Velocivixen.

Bicycle Addict

I use 122.5 on the earlier triple cranks when it comes to a 68mm BB shell, sometimes going down to 118mm, getting the drive crank in for a nicer chain line from top to bottom. Your small ring to seat stay will be the best guide, without seeing the reverse of the cranks I can not tell for sure but it seems that 127mm in a 68mm BB shell will pull the cranks quite out quite far.
A lot of bikes have BB's that are too wide, Sheldon Browns BB database lists nothing wider than 122mm faor SR cranks.
Hope this helps

intransit1217

Clearly others are better versed in this than I am. But I'm watching with interest, for educational reasons.

So my ignorant question of the day would be: what is preventing you from simply bolting on the inner chainring to the current crank set up?

Amesja

I'd make sure first that there is going to be enough clearance for the triple's inner ring against the chainstay before I went one step further. It might just not work at all with this frame. No use wasting energy if it can't and still have proper chainline.

Then, personally, if it wasn't a valuable and/or rare collector's frame I'd simply modify the 70mm BB shell to 68mm. I'd install the BB I had that matched the triple crankset I wanted to use and measure to the seat tube center to figure out where the chainline was as-is, how far it had to move in, and how much clearance I had between the rings and the chainstay to play with. This all would determine how much I milled off of each side of the shell. You have 2mm to play with here that can come off of either side or both. I've got a spare BB facing die that I use just for these "excessive facing" jobs like this that I don't mind abusing for milling off 2mm of shell. Yes, I've done this in the past...

OK, I know I'm a bad C&V-er heathen and this might draw the ire of the traditionalists who flip out if you so much as remove the original decals on a bike, much less start modifying things like the BB shell to fit modern standards so that you can fit modern components. But a bike is just a thing, and things can be molded and shaped to our needs and wants if we have the creative skill and drive to make it conform to our wishes. It's just a machine, not a fetish object to be worshiped on some altar. If a machine doesn't fit your purposes then you just re-make it using your skills and knowledge to suit them.

I've got a '74 Raleigh Competition frame currently running outboard BB cups with a Hollowtech 2-piece crankset, and a Raleigh LTD-3 running a standard 24tpi ISO square-taper 68mm cartridge BB, so you know right away how I roll.

Amesja

They are your knees. Treat them however you like. Sure, modern medical science has gotten to the point where they can put one (1) new set in -but everyone I know who's had knee-replacement surgery says to do whatever it takes to avoid the necessity.

YMMV

fietsbob

appears all you have to do is buy some new chainrings, 110 BCD will take a 34t..

Surly(QBP) Stainless steel are very long wearing*... get a newer style ramped and pinned Outer one.
they help pick up the chain a bit quicker when you upshift ..

7075-t6 is a long wearing aluminum alloy used to make chainrings.

as to the triple

Depends on the crank profile * .. have the crank ? take it and the bike to a Shop and let them use their BB inventory ..
you only have to pay for the last one they install .

Your trial and error is eliminated or shifted to the shop . UN-55 cartridge BBs are cheap (made by Robots).

* low profile type, the crank, by design, comes in to meet the spindle.. for example. That uses a shorter one..

ThermionicScott 

The cool thing about BBs like the one pictured is that the NDS cup doesn't have a lip on the end. So you can install them in an English-threaded 70mm shell and add spacers on the DS in order to play with your chainline, since the NDS cup will just thread in however far it needs to hold that end in place.