Bill Kapaun

Possibly, you might be able to simply "flip" the spindle.
I've seen some early 80's? Diamondbacks that came in a triple & double.
They used the same spindle, long side out for the triple and short side out for the double.

Velocivixen

@Amesja - the Mixte, the bike I want to ADD the triple to already has a bb shell of 68. It's the spindle for the triple that came from a donor bike with bb of 70. Regarding my comment on shifting, and your response about knees. I do shift, but not like my cycling partner who downshifts multiple times before coming to a stop sign, then multiple upshifts once we get going again. This particular bike has brazed on down tube shifters and I have short arms, so I don't like reaching way down to shift. I have good knees at this point and won't do anything to harm them.
@ThermionicScott - I've had some bike mechanics say they would just add spacer to drive side & use original triple spindle, and others who say they'd just get the "correct" spindle. So 6 of one - half dozen of the other???
@Bill Kapaun - Howdy neighbor. I've wanted to say that to you. Good idea. I will check things out.
@fietsbob - ok, that's good to know. I'm not sure what constitutes "low profile" vs more profile. Here's a photo of just the crank arm and the distance from the large ring. Is this photo enough to demonstrate whether it's a low profile or would a different angle or overall shot be more informative?

fietsbob

Shimano XTR M 900 cranks were more of what is low profile ..
VeloBase.com - Component: Shimano FC-M900, XTR M900

lower end, even the XT M730, the spindle comes out a bit more, to meet the crank.

the Right angle straight arm cranks from the Pre MTB mass production era are the wider style TA Cyclotouriste

VeloBase.com - Component: Spécialités TA Cyclotouriste

Bicycle Addict

Velocivixen, if I lived in the States I would just send you a 122.5 for you to try, I am almost certain it will work.

1 question though on the Nishiki how much of a gap is there between your on the crank and your BB cage? and chain ring to seat stay

Could you please take a photo looking down the seat tube at the BB and chain stay? Also one from the back of the bike as it sits with the chain in 2 on the cogs and also on inner chain ring? I would like to see the chain line.

I wouldn't want to say for definite but, I have found some cases on 70s-80's 10/12 speeds some bikes had such wide BB axle widths that I could use the original axle to convert to triple when setting these up as retro tourers for friends, this may be the case on your bike. With a very nice chain line.

likebike23

I would just get a couple of 1mm spacers and put them on the fixed cup and use the crank's spindle. Spacers are cheap enough, cassette spacers are the same size, it doesn't have to say "for bottom bracket".

onespeedbiker

As juvela said The difference between to two BB shells is only 1 mm on each side. To install the 70mm spindle in a 68mm shell, all you need to do is add a 1mm spacer to the fixed side and it should solve your problem. The adjustable side cup will extend 1mm farther, but it's "adjustable" so there shouldn't be a problem.

ofgit

Most of my stuff is set up with similar low gearing 'cause that's the way I like it. Only time I might need a 52 tooth ring is when there is a huge tailwind but I probably wouldn't be riding that day anyway to avoid the headwind.

jyl

I forget who is was, but when asked if it was better to spin a small gear fast or to push a big gear slow, he said it was best to spin a big gear fast . . .

Need muscle to do that, build it by attacking a big gear instead of dropping to a little gear whenever it gets hard :-)

I'm in the minority maybe but I think a 52/14 is an important gear to have. 80 rpm gets you 24 mph. 42/14 at 100 rpm gets the same speed but when the lungs run out, good to be able to gear up and use up the legs.

Velocivixen

@jyl - I'm all for building muscle - that's what personal trainers & PTs are for. Seriously, I'm afraid to go fast. More than about 20 mph & I'm holding on for dear life. It's not my nature to cycle fast, so I'm not worried about what I might loose moving from a 52 to a 48. Now, I'll go full steam in other athletic endeavors, just not cycling.

Amesja

Spinning a big gear slow is increasing the amount of force transmitted through your knees by a huge amount.

Jamming a big gear taking off is analogous to slipping the clutch and lugging an engine at a stop sign in 2nd or even 3rd gear. Sure, you can get the car to take off but you are burning the valves and slipping the clutch -causing wear on both of them.

There is an auto repair shop at just about every major intersection in a decent-sized city that can replace a clutch and most can do a valve job too. It's expensive, but not a big deal.

Have you priced a knee surgery lately?

You downshift your car or your motorcycle as you come to a stop, and then shift back up. Why not do it on your bicycle? Ask your doctor what he thinks.

Go ahead, they are your knees. Unfortunately with the unaffordable care act that passed a few years back, and is taking effect in stages, everyone is eventually going to be sharing in the future for the paying to fix bad health decisions other people made in the past.

jyl

VV, you need to be able to grind your husband into dust! Which, from what I've seen, will take some doing. So you need all the weapons (gears). Eventually you will be flying in 52/12 and he'll be seizing up trying to catch you.

Anyway, I would hold the triple crank on the double spindle and eyeball what spindle length you might need, then go to CityBikes and rummage around their loose spindles. Take the double crank spindle to know what cone spacing you need. I bet you'll find something suitable there. They have spacers too.

Amesja, everyone has to respect the limitations of their particular body parts. But knees will give you plenty of warning. If you listen and back off when you hit those limits, I think it will be fine.

As cyclists, I think we've picked an activity that is pretty knee-friendly. The people I know who have had TKR are life long runners ( evil for knees ), played high football in high school ( ditto ), or have carried way too much weight for way too long ( ditto ).

Velocivixen

Yo! Let's get off the knee topic. I didn't say I never shift. I'm usually in such an easy gear I don't have to downshift & starting from a stop is easy. Many people shift in order to keep a particular cadence. I don't give a rip about my cadence. Just wanna ride. My joints are all in fantastic shape including my knees. I'm an endurance runner (think 26.2 miles), do crossfit, and many other activities that keep my body in tip top shape.
@jyl- I did a bunch of measuring, mounting, etc. & Ill need 68 x 122 spindle. I'll go to Citybikes and get hooked up.

Bicycle Addict

I am really surprised how complicated this thread got!? @Velocivixen, glad to see you on your way to being sorted, a UN55 would be a nice upgrade while you have the cranks off.
122's fit that era of 10/12 speed and the early 90's MTB's well.

Uncle Randy

I like cartridges, too. She also has to get the special tool for the cartridge $13-18 or use one at the co-op.



I clean the threads with a Dremel and wire buffer, wipe down with mineral spirits and grease them so the cartridge threads in easier.

Bicycle Addict

Agreed Uncle Randy, I like Parks Shimano BB tool, it fits an existing socket wrench I had etc.

I am lucky enough to have access to the BB tap at work, I only really chase difficult BB threads all other cleaning of threads happens with a steel cup each side with some cuts in the threads, homemade BB taps! Stay away from the lead in thread, makes life hard otherwise.

Grease is a wonderful thing you can actually get old BB's out when the threads are greased, when installing I always use a nice heavy black grease from Morris Lubricants.

Michael Angelo 

I also have a Mixte Frame set with a 70mm shell and english Threads. I am currently building it up for my Daughter. When I first measured the BB shell I couldn't believe it, The bottom bracket is is fine shape so it will be reused. That's a good thing, if not I would be facing it to 68mm in a flash.

ironwood

Is your SR Signature crank drilled for a triple? Some are and some aren't. If it is, it might be possible to simply add a small ring. SR made it difficult because some cranks were drilled with a small, non-standard hole. (sorry, I can't give the precise thread size)

On a Miyata made Univega, I was able to fit a third chainring without changng to a longer spindle.

Your spouse must ride a Volpe.

jyl

I have a childlike faith in Citybikes' ability to find anything I need in their parts bins. I've even found loose spindles to convert cottered cranks to square taper. They have more stuff in the back room than what you see in the front. CCC is also very good for dumpster diving.

Velocivixen

@IRONweed -my spouse rides a 2008 Trek 200SU with pletscher double leg kick stand, front & rear racks, a trunk bag on back, a leather U-lock holster and a myriad of lights. His bike weighs about 40 lbs. He can show up at ANY century race wearing cargo shorts, a polo shirt and hiking boots (he's not into fashion) and hang with the "carbon & Lycra" crowd. They've been known to try to shake him and mostly they can't and they end up scratching their heads. He has a Go-Pro camera & films it. Pretty cute.

Also there are only "divots" where the holes would be to mount a smaller chainring on that double crankset.
@Michael Angelo - would love to see your Mixte. My mixte HAS 68 mm bb shell; it's the mountain bike that I stole the triple crankset from that has a 70mm bb shell, so the bb spindle is too long. I don't want to use spacers, as others have mentioned.

UPDATE: I rode about 8 miles last night with my new & improved 38-48 double on the mixte. I determined that, if I want a triple, I will require a 68 x 122 square taper spindle. I will go to the co-op, where hopefully, they would have one. Or if one of you is feeling particularly generous and want to lighten your inventory, you can PM me with an offer to gift me one. I do "pay it forward".

likebike23

You know, a compact double is actually pretty nice. I have a 47-36 on one of my bikes and like that I can keep it in the 47 most of the time and use the 36 for more hilly or windy rides. I like to spin and not grind, so 47 is a good for me. I don't track speed or anything, but feel like I ride faster overall cruising in the 47T ring. You may find that what you've got is fine for your style of riding.

Uncle Randy

That could be the same for a Miyata. It's worth a try.

Uncle Randy

It would probably be too close to the right chainstay and the chain would rub against it.

Velocivixen

@Uncle Randy & @intransit1217 - Bingo! I tried hand mounting the triple on to the current spindle and the chainring was extremely close to the chain stay. If I had mounted it all the way, it would not be able to spin and would ruin a perfectly lovely paint job. Definitely need a longer spindle. Current spindle length for the double is 68 x 115.

Also, there are no threaded holes on the backside of the spider arms (or whatever) where I could mount a smaller chainring using this crankset. I would have to use the triple entire crankset. Also, not sure this matters, but the crank arms on the mountain triple crankset are 5mm shorter (165mm) than on the current double (170mm). I guess that's ok. Guess it depends on whether or not I'm a "spinner".

Uncle Randy

@Velocivixen


“Martin conducted a study using 60 racers of all skill levels. He would vary crank length in 15mm increments, both longer and shorter. His findings showed that there was no power difference from one length to another, but that oxygen uptake was always better with shorter cranks.

“Subsequently I worked with a rider who is 6'5", bringing his crank length down to 165mm’s over three months. He’s gained 65 watts of power.”
- See more at: Crank Length: Coming Full Circle

and then there's your Q Factor:



https://www.sheldonbrown.com/bridgest...ne-1991-13.htm

jyl

Interesting. Can you drill and tap holes at the divots and mount the small ring to the double crank? Will the small ring clear the chainstay if mounted that way? The crank is aluminum, so will drill and tap like butter. Ideal to use a drill press (I have one . . . ).