sjanzeir

Good morning everyone,

I'm having a real issue here:



This is a new Tiagra FC-R460 crank, and that is a new, never-before-installed SM-BBR60 bottom bracket. I'm trying to install these on my 2014 Trek 7.6 FX (this is a 165mm replacement crankset to the factory 170mm.) I wanted to test fit everything to figure out how many shims I'm going to need for the proper chain line.

No amount of finessing, cajoling, and hammering (with a composite mullet, of course) will drive the shaft into the BB. I decided to stop before I do any damage and ask here. What's the deal with this thing?

HillRider

That is unusual (I hope) as I've never had any fit issues with multiple Shimano HTII cranks in Shimano HTII bottom brackets. The fit is snug but not difficult. If you still have the old crank and bottom bracket and they are both HTII types try the old crank in the new bottom bracket and vice versa to see which component is the problem. Obviously one of them is off-spec. Also, try the non-drive side crank arm on that spindle to be sure the spindle isn't oversize.

Iride01 

That's odd for me too. On several bikes that I have Shimano 2 piece cranks they just slide right through. Maybe needed a little coaxing. Although there was a recent thread where another seemed to suggest they've had to bump the crank with the butt of their hand or a mallet.

What does the old crank do? If it too is an issue, then I might wonder if the sides of your BB are parallel. But I thought these type bearings made up for much of the reasons we use to face BB's. Or is the spindle getting caught in the first side of the BB?

Or is the BB new too? What crank and BB were on it before?

sjanzeir

It pains me to say that both crank and BB are brand new, never used, straight out of the packaging. The setup I'm swapping out is a good old square taper, so I can't test against that.

Now, here's what happens when I hammer the crank back out:




It seems that the plastic cap that acts as a spacer between the shaft and actual bearing race isn't to spec; for some reason, it's just too snug.

Now, here's how the crank fits without the plastic spacer:




The same issue isn't there on the non-drive side; the shaft didn't push the other plastic cap out with it as it worked its way through, as I thought it might.

However, here's how far the shaft went into the drive-side cup of an off-brand, Chinese BB before it stopped cold. That's a BB I had used on another bike without issue for months:




That, too, is a no-go. I measured the shaft at several places along its length and I got everything between 23.93mm and 24.01mm.

Here's the BBR60 on the shaft of a Chinese Hollowtech II knockoff:




Fits about as snugly as you might expect with the force of my hands, no issues there.

I must admit that I have no idea what I'm going to do at this point. My options are to order another BB and see if that'll fit, or talk to the LBS and see if they can help. I could order a square taper 165mm crankset and call it a day, or I could just go with Chinese parts off of Aliexpress again. We'll see.

Barry2 

What happens if you take the plastic spacer, slide it all the way onto the HTII shaft, then insert the spacer/shaft into the bearing?

Barry

Iride01 

Any chance that BB shell is too wide for the inner sleeve of the BB and you were hanging up on the edge of the inner sleeve. due to the BB faces not being parallel? Or if it is the correct size for the BB, they say to install the right cup first, which is the one with the sleeve isn't it? That might let you better feel if the sleeve is fitting into the other cup as you put it on.

But I guess part of the thing I'm describing above will require the sleeve to have been put on the wrong side, which might be a possibility if you have the version where both sides are right threaded.

Otherwise a FC-4600 is supposed to fit a SM-BBR60. How sure are you that the person selling the crank wasn't just selling what was a problem for them? Used crank or NOS?

sjanzeir

Tried that. The spacer just refuses to go past about halfway up the left-side splines, and then it would take a few blows from a heavy rubber mullet to force it off.

sjanzeir

The crankset is NOS; it came in a nicely closed Shimano factory box with all the protective packaging and documentation intact, and they still have five of them left!

As for the BBs themselves, both the genuine BBR60 and the Chinese knockoff (both BSA) fit into the BB shell as they should, with no odd snugness or resistance that could suggest that the sleeve is off; they thread right up to the shell faces, by hand.

Iride01 

If the end of the spindle is going in far enough to be through the first cup and into the sleeve and I felt that the issue might be the sleeve itself then I'd probably just hit the crank hard with my palm or butt of my fist or may hit it with a big rubber mallet. Just be careful when the end of the spindle gets to the beginning of the cup on the other side. If it's still giving you resistance, you might mess up the splines there.

sjanzeir

As I mentioned earlier, it's the plastic spacer that won't clear the splines (or, rather, is too tight to let the left-hand bearing surface go through it and on to the other side.) My big-ass rubber mullet - that thing must weigh a couple of pounds - damaged the sparkly finish next to the Shimano logo and the spindle still never budged beyond the line between the splines and the bearing surface.

Anyway, I've just ordered a BB-RS500 (a proper Tiagra BB if there ever was one) and will see if it fares any better. There's also a Sinz square taper crankset in the pipeline if Hollowtech II isn't in this bike's crystal ball.

sjanzeir

I finally grew a pair and banged harder and harder until I thrusted the shaft all the way in:








No spacers needed. I got this pair of used 165mm Sinz crank arms just in case this Hollowtech thing didn't work out for any reason and I needed to stick with square taper. Now I'm going to temporarily run them on my other 7.6 until I get around to doing the same Hollowtech upgrade to it: