ACHiPo 

I’m refurbishing a c1978 Centurion Pro Tour. More of a resto-mod actually: new tubeless wheels with 9-speed cassette, triple crankset, etc.

I ordered a used Specialized Flag triple crankset that should be delivered next week. I’d like to make sure the bottom bracket is ready to go when it arrives. If the existing (excellent condition) cup and ball bottom bracket set won’t work, I want to move to a modern sealed unit.

Research suggests 115 - 125 mm spindle length for the Centurion’s 68 mm shell width for a triple crankset. The existing spindle is 124 mm (32 mm left, middle 53 mm, 39 mm right drive side). It has a 1 mm spacer on the right side between the cup and shell, presumably for the stock Suntour SR double.

Will the stock BB work with the Specialized triple (inner chainring clearance, chain line)? If not, what size cartridge would work?

Thanks.

Kontact 

Spindle length and type are dictated by the crank. Look it up in velobase or some other reference.

sd5782 

Others will say that ultimately you won’t know until you try it. That being said, my guess is it will work. I personally like the inner ring on a triple to be close to the chainstay.

merziac

You will need to test fit the crank when it gets here, no way to know for sure until then.

Used cranks that have been in service will end up in different places depending on stretch, taper, wear, the sun, moon, tides, etc, etc.

This is where a co-op can be invaluable if you can grab a hand full of spindles to test fit, mix and match, etc which is what it usually takes to get there.

Plenty of info out there and many here have it down to a science but can always be hunt and peck.

I encourage you to stick with cup and spindle on this, experience you gain from this can be invaluable going forward.

merziac

Guilty, but I never have to ask the question, the futzing is the best part IMO and the experience is priceless as a problem solving exercise.

I usually get it right by the second stab.

ACHiPo 

Velobase is where I found the 115: “The spindle length was listed as 114.5 or 115.5, with a 20.5 to 21.5 offset on the right side. Some sources identify these as ISO taper. I tried mine with a Campy cartridge BB and they were a better fit than on a JIS taper. These cranks are not the same as the similar-looking version with the lazy-S logo. The flag version were the top, cold-forged model.”

ACHiPo 

Thanks!

ACHiPo 

Got the Specialized flag crankset. Surprise—the 124 mm spindle is too long! The inner triple chainring sits about where the SR double sat, but the big ring is ~5 mm too far out.

SR double crankset

Specialized flag triple crankset



The Specialized crankset has a ~7 mm “bump” protruding inboard.

Specialized on the left. You can see the “bump” that pushes the middle and outer chainrings out 5-7 mm.

I found this Specialized datasheet which calls for a 114.5 mm spindle for a 68 mm BB and Specialized triple. That would be ~9 mm shorter than the current spindle which seems excessive. Maybe with a symmetric spindle it would be correct?

ACHiPo 

I visited the LBS yesterday. They had a 115 and 125 mm cartridge and no spindles, so no luck.

Sooo…
At this point I’m thinking the easiest/most likely solution would be to find a new JIS spindle with 32-35 mm on the right side, so a 117 mm spindle with 32 mm left, 53 mm center, 32 mm right. No luck finding one online yet.

OR…

Should I just order a 118 mm Shimano cartridge and a few shims and make it work?

Meanwhile I’m going to install the 52/40 double to get it on the road. Who knows, mebbe I’ll grow me some quads!

KCT1986

Attached is pic of the specs for Tange cartridge BBs and the aprox. length comparison to a cup/cone spindle (red #s). This is based on 52mm middle measurement (usual stated spec.).
Shimano lengths are very similar +/-0.5mm in most cases.




So a 118mm cartridge BB would move your DS in about 6mm and the NDS out about 1mm. These are estimates based on a 52mm center measurement, don't know where your measured lengths varies from the 52mm spec. It's somewhat difficult to determine exactly where to measure on the spindle.

Overall, for a crankset install, a couple of mm is irrelevant one way or the other. Unless the frame has clearance issues with the crankarm/chainrings, or FD range limitations, on a multispeed bike the chainline can work fine if it's close.

ACHiPo 

Thank you. This is helpful. I figure +/- 1 mm should be fine, especially since I have a ~0.5 mm shim to move the spindle out a bit if things are too close.

Where can I find 1.37” ID shims? I find a bunch of options for smaller BBs.

mpetry912 

Get a phil 121 mm bb and solve your problem

/markp

ACHiPo 

How does that solve the problem of the big ring being about 7mm too far out with a 124 mm spindle?

KCT1986

The Phil Wood BB gives you some leeway in the clearance on each side, by being able to be installed up to 5mm (?) offset in the frame shell. This does change the NDS as well.

Did Phil have 121?

And of course the Phil is $180 when a Shimano is $20 or so.

ACHiPo 

Makes sense. If this turns into my forever bike, mebbe Phil is a possibility. As of now, I have about 3x more into this project than it’s worth. The $20 Shimano seems more attractive.

oneclick 

1.375" is the standard BB cup and freewheel shim ID.

If you need a 36mm shim instead pm me, I make them when I need one.

What are these smaller BBs of which you speak?

due ruote 

If my mental math is correct, it sounds like you could flip the existing spindle and space the DS cup out by 1-2mm and it would work.

ACHiPo 

That’s a heck of an idea! Thanks! Even if it is not successful, it will give me another data point before ordering a cartridge.

ACHiPo 

Brilliant suggestion!

I flipped the spindle this morning and voila! Even without the 0.5 mm spacer. Now the question is whether I can/should live with the Q of the left crank being out a little further than necessary? It seems like something I can fix down the road if/when I strip the paint and wrap the main triangle.


Thanks!

ACHiPo 

Just mounted the left crank and torqued both sides down. It definitely looks too far out. Oh well, I’ll add it to the punch list…

brooklyn_bike

looks like maybe the velobase listed 115mm length could be closer to correct. to my eye the smallest chainring could still be pulled in closer to the frame even after flipping the spindle. i happen to prefer my cranks as close as reasonably possible on the drive and non-drive. i find the front derailleur shifts best when the small chainring is fairly close to the chainstay . but i use cup + cone and have a bin of nicer bottom bracket spindles i've collected over the years so i try one spindle i guess to be close (like you've done) take careful measurements and use the spindle that gets things as tight as possible.

so if my math is right you could move in the DS another 2-3mm so that's 32/53/30 = 115mm and also possibly move in the NDS as well (i haven't seen a photo of the clearance that 32mm would give you on the NDS) so it's possible the NDS and DS could also be 30 : 30/53/30 = 113mm

ACHiPo 

You may right. The 3x little ring is about the same place as the 2x little ring. It could maybe get a little closer. The 32 mm distance with the axle flipped should be equivalent to 115 symmetric? It’s hard to think 113 would be better, although it could work for the little ring distance.

I ordered a 115 cartridge. I’m pretty confident it will work well.