Michael Angelo 

You can use a shorter spindle for the 68mm shell and still use a triple, I may have one that fits your aplication. I go look now.I'll let you know.

Velocivixen

@Uncle Randy- thanks for that information. I will read the entire article tonight. Good to know shorter crank arms won't make a bit of difference and may even improve my situation.
@jyl - you're so creative. I think getting a slightly longer spindle is the simplest route.

Michael Angelo 

Just looked in my inventory, I found a 129mm Spindle for 68mm Shell.....maybe you need it??

Velocivixen

@Michael Angelo - how very generous of you! I would like to try to get a 68 x 122 first to see how it works (I think it will be perfect), however if it turns out that I need a longer one, could I send you a pm? Thank you so much for checking your stock!
Cheers.

Michael Angelo 

Sure, I also have a 124mm for a 68mm shell

old's'cool

Sorry, don't know how I missed this thread before, and don't have time right now to read the whole thread, so I apologise if a resolution has been reached or if my input is otherwise redundant... @VV, what reason do you have to suppose your triple crankset will not work with the 68mm BB? The reason I ask is, I have converted 4 of my vintage bikes from double to triple (including a 1987 Miyata 312, not to mention its distant cousin a 1982 Univega Viva Touring); and not one of them needed any change to the bottom bracket. All have sufficient clearance between the inner ring and the driveside chainstay, not to mention excellent chainlines in all reasonable gearing combinations.

Velocivixen

@old's'cool - No worries. Here's the deal. Mixte has 68mm bb shell with double & 68 x 115 mm spindle cup N cone (no holes to add granny to this crankset). I have the EXACT model crankset only in a triple and it has 70 x 129.5 mm spindle. It's the bb shell difference. Yes - I can add a 1 mm spacer between frame & fixed cup & use the 70 spindle, but don't want to do that necessarily. I incorrectly thought there was some simple mathematical "formula", where I could just, say, subtract 2 mm & call it good. I need/want a 68 x 122 mm square taper JIS spindle, which I can most likely find at my favorite bike co-op OR I could simply buy a Shimano UN55 in the correct size.

I'm simply trying to learn how to make it happen, from a bike mechanic point of view. I have already swapped out the 42/52 for 38/48 using the original 68 x 115 mm spindle. But still want that granny ring. I tried the triple crankset on the current spindle just to see and 115 is definitely too short. I've done measuring & am fairly sure the 122 will be perfect. So....tomorrow the co-op.

Velocivixen

@Uncle Randy & @Bicycle Addict - I already own several Park Tool Bottom Bracket tools and have experience replacing cup 'n cone bb's with cartridges. I did this on my Hard Rock Ultra. I have quite the tool collection built up over the past year.

NOTE: could someone PLEASE explain to me how to reply with a quote? Every time I click bellower where it says "Reply With Quote" then respond, I get a pop up message saying I can't post because my message was too short, despite how long it may be. UGH

Shp4man

Type the reply after the "[/QUOTE]" HTML command.

Velocivixen

Like this?

well that didn't work.

Uncle Randy

I d

Uncle Randy

on't have this problem if I use two characters. Are you using Internet Explorer? If so, try Safari or Firefox.

onespeedbiker

Velocivixen, if you want to determine the proper length spindle, you need to measure the C measurement of the 70mm spindle as below; the C measurement is the drive side and then add 1mm for the 68mm spindle; the spindle for a 68 spindle with have a B measurement 2mm shorter than to 70mm spindle, so the over length can still be the same (but doesn't have to be).



Now go to this site Sheldon Brown's Bottom Bracket Size Database, check out the graph under the above spindle graphic and see if there is a spindle that has the same (or close) C measurement. The newer cartridge BB are all symmetrical, meaning the A and C measurement are the same. If you want to use one you will need to double the C measurement and add about 52 mm (the constant for a JIS B measurement for a 68mm shell spindle).

onespeedbiker

if the poster types between the HTML commands "[QUOTE=Poster Name; #######]" and "(/QUOTE]" (which contains the quoted message)then it will appear there has been no reply because the posters message will be incorporated with the quoted message, hence the warning; You can't post because your message was too short.

Uncle Randy

[QUOTE=onespeedbiker;17140550]if the poster types between the HTML commands "I don't think @Velocivixen is typing between those tags, onespeedbiker. VBulletin is the software they use for this forum. I've read that it sometimes has issues like this with IE.

Velocivixen

@onespeedbiker - thanks for actually explaining how to use Sheldon Brown's chart. I've used it before, but not quite in the way you've explained. I will measure and figure out what I get.
@Uncle Randy - I'm using Safari. So I'll have to practice. At the bottom of the text box after someone has posted there are 3 choices: an arrow wight he word Reply, "Reply With Quote or "+. I choose the middle one and it puts the person's info in a new box then I type. Obviously doing it wrong. No biggie.

onespeedbiker

[QUOTE=Uncle Randy;17140572] I was explaining a mistake I have made that resulted in the same issue. I don't use IE so I wasn't aware VBulletin and IE sometimes don't play well together; thanks for posting the info.

Uncle Randy

Yes, she should click on the Reply with Quote button and start typing after the /QUOTE closing tag.

Bicycle Addict

@Velocivixen, are you planning to use the front mech off of the donor bike? Some twin ring front mechs will cope with changing triple rings with some stop screw adjustments.
As far as tools go . . . I have an addiction here too! It is not only bikes that I can not/will not stop buying(my bikes bar 2 cost me less than $60 per item), next tools on the planner are a Park TS2.2 a spoke tension meter and Ice tools bottom bracket tap and facing tool, I hope to have these within about 6 months, fingers crossed.
I have to say my wife is incredibly patient with me here, the lovely lady she is. Yea I know

Velocivixen

@Bicycle Addict - I could try to use the front derailleur of the current bike (derailleur for the double), however the donor bike had the "triple version" of the same derailleur, so aesthetically they look very similar. I was just gonna use the triple front der. I used the freewheel (14-30) from the donor bike and ended up needing to use the donor bike rear derailleur, as the larger 30 cog was taxing the mid cage der. that was on there. So basically using freewheel, crankset and front/rear derailleurs from donor bike. Current levers will play nicely with the setup.

Just got back from the co-op with a new used spindle that I think will work.

Bicycle Addict

I see happy wrench turning times ahead, look forward to seeing the conversion complete, and hoping the 122 spindle works out.

old's'cool

@VV, not sure if it was clear in my initial post. I did not change the BB on any of my triple swaps. I just installed the triple crankset on the original double BB.

Uncle Randy

@Velocivixen, did the spindle work?

Velocivixen

@Uncle Randy - I'm having so much trouble. I transferred all the mountain rings (28/38/48) onto its original crank arm (spider?) and installed the new spindle. It fit well, although the left side was a little shorter than original, but it all fit. I tried keeping the original double Derailleur, but it didn't shift well, so I installed the Shimano triple front Derailleur. I use KMC X8.93 - supposedly a 6/7/8 speed chain. I followed ParkTool website on setting up & adjusting front dersilleurs METICULOUSLY. Also this is not my first front Derailleur install, but I do think they're finicky. Had to remove 1 full link of chain for optimal length (went from 52 to 48 teeth & yes I know how to do this).

PROBLEM- setting low limit. Chain in big cog rear and middle chain ring will not fall to small chainring unless I loosen the low limit screw A LOT, then chain falls past small chain ring off the bike. I set low limit by having chain on small ring/ large cog & have inner Der. Plate about 1-2 mm from chain as a starting point. I pull inner wire by hand (not shifter) to move chain to middle then release while pedaling & note how chain falls back to small ring. Again, I have to keep loosening low limit screw to get it so work, but then when I go through all the shifting the chain falls off little ring MOSTLY when chain is in big cog rear. Interestingly, if the chain is in the next to largest cog/middle ring chain will fall to small ring and Mostly not fall off.

Lower edge of outer cage is just about 2-3 mm above teeth of large chain ring (tried putting a penny there & wouldn't shift well). High limit is set properly. Rear deraulleur indexing is set properly. I tried rotating front Derailleur various ways (I.e., tail in more, tail out slightly) with no discernible improvement. I noticed when chain is is MIDDLE cog rear & middle chainring(higher angle of front deraulleur to chain angle) the chain would drop to small chainring without falling off. This angle lead me to try rotating the tail out away from bike a little. The lower profile crank arm hit the tail of the front Der. When I did that.

NOTE: this crankset/ front & rear derailleurs, and rear freewheel ALL were OEM from a 1987 Miyata Valley Runner mountain bike. They should all play nicely. The ONLY thing different is they're on a road frame and the replaced spindle is for a bb shell of 68 vs 70. The new spindle has the exact same amount of projection out past the fixed cup as the original spindle, so lateral position of crankset in relation to midline of bike should be adequate.

I know now this is a lot of detail & Ive included it because if I don't, I will end up with a lot of helpful folks telling me to do things I've already done. Bottom line is that I followe complete Derailleur install & adjustment, all Derailleurs shift beautifully EXCEPT when trying to move the chain from middle chain ring to small AND chain is on larger cogs rear.

My assessment is that I 1. Need a wider chain (I'm not gonna do that), or 2. I need to bend the outer cage plate IN approx 1-2 mm so it pushes the chain onto the small chain ring and I can have the low limit set so chain doesn't fall off. I will note that it was dark out and I have not actually ridden the bike to see if it falls or fails to shift properly in practice.

Velocivixen

Update/Conclusion: I "toed in" the front Derailleur, meaning I bent the outer plate in a little, and now I can have the low limit screw set reasonably and have the chain move off the middle chainring. I noted that the chain was not seating correctly on one spot on the small ring, so I marked the tooth with a sharpie, removed the chainring and saw a warp, and that tooth was bent and the area near it was roughed up. I straightened the mild warp as well as the tooth & used a Dremel to smooth out the rough areas and now the chain stays seated.