5mm

I recently acquired an 85 Trek 620 from a yard sale for $15! (pairs nicely with my 85 600)

Its in decent shape and I look forward to upgrading a few bits to make it a reliable commuter/ occasional tourer.


The main issue is that I cannot shift into the largest chainring no matter what (FD is original Huret and not hitting its limit and height is correct).

It's a chainline issue that I'm narrowing the culprit down to the drive side crank arm or spindle as only the drive side crank arm was swapped out to Sugino, where left side is still Shimano for some reason.

Maybe the spindle too was switched out for something too long when the crank arm was swapped I dunno.


Long story short, I came to ask a question which is: Does anyone out there know or have access to measure and tell me the stock spindle length on a Trek 620???? I would be forever grateful!

nlerner

Since you have it in hand, my suggestion is to measure the drive side and overall spindle length, estimate how far more outboard it needs to be, and go from there. Lots of inexpensive cartridge style BBs available.

noobinsf 

Stock would have been the Shimano FC-6206 (aka N600), and this shows the spindle length as 121.5mm:

https://velobase.com/ViewComponent.a...115&AbsPos=352

That said, you may or may not need the same spindle with the mix-and-match Sugino/Shimano set you have now. Since you need to pull the bottom bracket anyway, you'll just need to measure and have a little trial and error.

5mm

As a newbie here it blows me away to get such helpful replies within minutes! thank you!

The spindle length as I have it now is 121.5 and stamped Shimano so it looks like that is probably OEM and the Sugino crank is likely the culprit. Good to know.

I had already taken everything apart before measuring how much more inbound the chainrings need to go. duh! I'll either throw everything back together again in a temporary fashion or take an educated guess...

tricky 

@5mm

Spindle lengths are specific to cranksets, not bikes. Here's Sheldon Brown's list of Sugino cranksets and the needed spindle length. Sheldon Brown's Bottom Bracket Size Database

Are you sticking with the Sugino? If so, go with the Sugino spindle length and not the Shimano since the chainline is determined by the driveside crank arm and not the non-driveside (NDS). Caveat: If you are going to keep that Shimano NDS crank arm, measure the non-drive side of your current spindle to make sure the new one that you eventually get is not too short. You don't want to install just to find out that your NDS crank arm is hitting the frame.

Oh, and pics please.

5mm

Thanks tricky that Sheldon chart helped narrow things down further as its Sugino XD crank which puts the spindle in the 113-118 range. And I'll keep the NDS crank arm in mind too, good point. Hopefully I can keep my funky setup.

tricky 

The top end of your target range for your spindle length is only 3.5 mm from the length of the spindle you have. I am wondering if you cheat a bit and add a 4mm spacer between the locking cup on the NDS and bottom bracket shell. This would shift the spindle to the left a bit, but then your drive side BB cup would need to be long enough/have enough threads to put enough preload on the bearings AND give the lock ring enough threads outside the BB shell to work properly. You could dry fit this even without a spacer by threading in the fixed cup but leaving it backed out 4 mm, then install the rest of the BB to see if this would work.

To be clear, I haven't tried this before. Just brainstorming an option. Someone with personal experience might chime in here and offer up first hand experience on if this is a good idea or not.

Dfrost 

I always set the chainline (center of ST to middle ring) for triples at 45+/-1.0mm. Any less will result in the FD hitting the ST. I’ve used BB spacers to get there with a sealed BB if there’s plenty of room between NDS crank arm and CS.

bikingshearer 

Unless I'm misunderstanding you, that won't work. All it will do is move the NDS lockring a few mm to the left and add a couple of grams of weight. It will do nothing about moving either cup, DS or NDS, and hence will not do anything about repositioning the spindle. The fixed cup can only go so far in. You can move it outward some with spacers, but the BB shell is kind of a hard stop for moving it inbound. (Not true with Phil Wood BBs and some others that don't have a lip on the DS cup, but you aren't dealing with those.)

Good luck. Trying to figure out what BB dimension to use has always been a (frustrating) challenge for me. Here's hoping you nail it the first time.

tricky 

Yup, you are right. It's been a minute since I've worked on non-sealed BB and I forgot that both sides have lockrings, not just the DS. I was thinking of how you can shift sealed BBs like @Dfrost mentioned above.

bikingshearer 

Hay, I've had far bigger brain farts than that. Probably in the last hour.

merziac

At the end of the day this is the crux, mix and match, hunt and peck, swap and spin.

Combined with Sheldon's time honored info, the right tools and any better understanding and you will be good to go on these dilemma's from now on.

Don't get too hung up on the finite info, dig in, get the hang of it and build up a stock of parts and pieces to facilitate the process, you will often have the parts on hand, I save any and all cups and spindles for reference.

The co-op is the place to stock up if you have one nearby, if not buy a few clunkers with square taper BB's and have at it. The experience and practice getting them apart can also be invaluable and will get you able to knock em out easy when necessary.

Funky can be the name of the game on this, great fun.