Sugino AT and MT68 spindle problems
 

Hi guys,

I'm hoping someone can shed some light on this one for me.

I have a 1984 Centurion Pro-Tour on which I am using a Sugino AT crankset. The bike came without the original BB unfortunately, so I don''t have that to refer to. The previous owner had been using the AT like a compact double with a cheap Shimano cartridge BB.

Well, I set the AT up as a triple, and everything I've read online told me to find a Sugino MT68 spindle if using the AT as a triple. It took me a long time to find an MT68, but in the meantime I happened to have a non hollow asymmetric JIS spindle that worked very well. I believe it is marked SCMB-3T; I will double check this tomorrow. It is VERY wide, something to the tune of 135mm IIRC (I'll measure it tomorrow)

Anyway, I still lusted for an MT68 because its hollow and very beautifully made. I finally found one, and tried to install it yesterday, and I encountered a lot of problems. I was under the impression that all MT68 spindles have the same dimensions; others have said they measure 37.5mm right, 52mm center, 29.5mm left, and the calipers confirmed mine to be the same.

First problem: My crank almost runs out of taper on the MT 68 (i.e., the fixing bolt almost bottoms out on the spindle) when torqued close to spec
Second problem: It became very clear the granny ring was not going to clear the chainstay even with a 1mm spacer under the drive side cup. I was thinking thinner spacers under the granny ring could help but I don't know how much thinner I could go before interfering with the chain. Also, with 3.5mm spacers under the granny ring, it looks to be perfectly equal distance from the middle ring as the middle ring is from the large ring, which has me thinking 3.5mm spacers are probably the intended thickness and also not the real issue
For reference, the bearing cups and bearings I am using are also Sugino, basically NOS. They are higher end, NJS stamped, and came paired with an MW68 spindle on a Univega Gran Premio I parted out. The non drive cup has small holes drilled in a circular pattern concentric to the spindle hole
Lastly, why are Sugino fixing bolts 15mm lol? I cant find a 15mm socket to fit in the hole in the crank arm so I used other bolts

I put a 2mm spacer (calipers had it more like 1.85mm) under the drive side cup, and once the crank was torqued, the granny ring bolts still would barely not clear the chainstay. Additionally, there really wasn't enough thread on the non drive side cup for the lock ring to grab, in my opinion

Can anyone help me understand why my Sugino AT and Sugino MT68 combo is not right? Are there ISO and JIS versions of the MT68? Which interface does the AT crank use, JIS or ISO? Thanks in advance

As an alternative, if you can find a 127mm (or is it 127.5?) Shimano cartridge bearing bb of any variety, I think it will work, although it sounds like you may not want to use a cartridge bb. It's been awhile since I thought about the bb on it, but I have an '83 Centurion Pro Tour with that same (beautiful) Sugino AT triple crankset, and I think a Shimano cartridge bb in 127mm spindle length works great if I remember correctly. My only other comment is that although Shimano cartridge bb's are inexpensive, don't take that to mean they are not extremely durable, no-maintenance, and for some, preferable to even high end cup and cone bb's.

Thank you for a very thoughtful and helpful response :) from one ProTour owner to another. I really appreciate it !

Yes, as you say and from what I gather a 127.5mm catridge BB with spacers should do the trick. Everything you said is true- the Shimano style cartridge BBs would make a very good solution. I'm not opposed to them in any way, but my bike is 100% early/mid 80s in terms of components so a part of me is really hoping to maintain that. But in lieu of a vintage- Sugino wizard I think you have offered a very practical and functional solution.

Its rolling on some lovely Sansin sealed bearing hubs so add a sealed cartridge BB and what will be left to maintain :D?

I'm seeing a lot of 127mm BB's and not so many 127.5mm BB's. That extra .5mm can't be a make or break detail can it?

No, the 127 spindle length should be fine, I just couldn't remember what I had installed on my Pro Tour with the Sugino AT crankset. :)

Awesome, thank you!!

Kind of makes me wonder why there was ever a 127.5mm, since that .5mm split evenly is .25mm per side... I know there are situations where a quarter of a mm would be important but this doesn't seem like one of those situations

According to my scanned Sugino catalog, the AT takes an RB spindle with a BB-SC bottom bracket, and either a 3U-B (bolted) or 3U (nutted) with a Maxy.

The RB spindle looks like it only fits the BB-SC bottom bracket.
Dimensions:
129 mm overall
30.5 mm drive side
16 mm taper (I think this is the taper length. It's confusing, because on the diagram it looks like the non-drive side length, until you look closely and realized that it's measured from the start of the taper rather than from the spindle shoulder.)
78.5 mm R' (measured from the centerline of the BB to outside edge of the crankarm's mounting bolt hole.)

That catalog doesn't show a Maxy bottom bracket, so the 3U-B / 3U dimensions come from Sheldon's database:
124.5 mm overall
32 mm non-drive side
40.5 mm drive side
Symmetrical equivalent 133 mm

But then, in the crankset-specific section of the database, for the Sugino AT Saint Sheldon calls out both a 127.5 and a 122.5 Shimano cartridge BB as a replacement, both with a 2 mm drive-side spacer for a 150 mm tread, plus a 115.5 +2 for a 139 mm tread. I'd assume that which one you need will depend on your frame and chosen gearing. (Smaller rings can be run tighter to the frame, since the chainstay angles outward.)

Hope this is useful.

--Shannon

PS: Does Phil Wood still do custom spindles? I bet that they used to make a bunch of bottom brackets for Sugino ATs, maybe they'd make you one?

i have the original cup and cone BB for my AT in a bag i can measure if need be? otherwise, SR spindles work for them. at least from an old SR super custom. lastly, as for the 15mm spindle bolt, i have a shallow thin wall craftsman i use. i say thin wall, but that's standard for craftsman. otoh, it's also almost 30 years old.

Spindle matchup is a nightmare, I feel your pain!

The 1984 Specialized Stumpjumper used the Sugino AT crank set along with a Specialized "Sealed" bottom bracket.
The Specialized bottom bracket was probably made by Suntour/SR. I do not believe that Specialized put their name on their bottom brackets for very long.

So you need that square taper that some say is a bit different from Campagnolo, ie: specific only to Suntour.
If you measure a bunch of Suntour spindles you will find that there are some slight differences in the taper due to machine shop tolerances.

Their is a set of Specilized cups and bearings for sale on evilbay right now. It is a good setup. I do not believe i ever had to repack the bottom bracket on my 1984 Stumpjumper, even after 30 years of constant torture.

The 84 Stumpy with the 68 mm shell appears to have used a 130 mm spindle according to this Specialized BB doc.
Hope this helps.
https://cimg5.ibsrv.net/gimg/bikefor...1386b3ceb1.jpg

Sorry it took me so long to respond but really, thank you to everyone for all this info ❤

thook, if you vould measure your original BB and possibly send me some pictures of it I would be eternally grateful! Any interest in selling it as well..?

I ran a Sugino AT triple on my 79 Pro Tour, using a Suntour Vx Sealed triple BB (subsequently moved to my Spec. Sequoia and replaced with a Stronglight 99 triple and BB). The Vx worked fine without any clearance issues. I think it's a 131mm spindle, I remember there being plenty of room to spare between the chain ring and the stay; a 127mm spindle will probably work fine (worse comes to worse you can throw a spacer on).

no interest in selling...sorry. ;)

i can get a measurement within the next day or so. i will try on a picture, but no promises there.

sharts!! completely spaced this out. terribly sorry! i'll make sure to get the measurement tomorrow :(