NDS crank arm slipping off

[marciero]

I have a recently-acquired Sugino crank, and the nds crank arm keeps gradually slipping off the spindle. This is a modern two-piece outboard bearing-type crank like Shimano where the crank arm slides on the splined axle/spindle, is seated with a large adjustment bolt that threads into the spindle, sandwiching the crank arm between the bolt and the bearings, with the arm itself secured to the spindle with two opposing pinch bolts. Every 40 miles or so I look down and can see a little daylight between crank arm and bearing (though one time it lasted a few hundred miles). I've removed the crank arm and cleaned the splined surfaces, and also cleaned the adjusting bolt threads and corresponding threads on the spindle. My thinking is not to have these lubed, but rather, increase friction. I was even considering loctite on the spindle.
My thanks in advance for any other suggestions.

Mike

[Cicli]

It may be hoggered out from being loose. There is no fix for that. Used to happed to square taper cranks that were ran loose.

[mktng]

you have the appropriate spacers (if needed) ? is there any play when you have it reinstalled ?

even the slightest of gap when installed is enough to wiggle itself loose under the load of riding.

[cmbicycles]

If its worn from being ridden loose, it may never stay tight. You could try some carbon paste to add a little friction and see if that helps. Is the spindle worn, or the crank arm show signs of wear at the interface? Does the spindle seat tightly in the bottom bracket, or does it need spacers? What model crank is it?

[marciero]

It could be worn, but I am not seeing it. If it is I certainly have a bone to pick with the guy I bought it from (a paceliner as I recall). I did have this happen with an octalink crank years ago.
The splined surfaces on this one appear to be clean and sharp. The spline fits snugly in the bearing.

As for spacers-I've never used spacers with Shimano cranks of this type, and none came with this one. Again, it was used though. It's a Sugino OX
http://store.somafab.com/suoxcrarwcu.html
It;s about the only 110/74 outboard bearing double crank that I know of.
I'll give it one more try after cleaning up and then it goes in the scrap heap.

[moobikes]

I would not use the cranks before taking a really good look. The NDS crank or the BB could be unsafe to use.

This is not a taper fit type of crank/ BB design. I'm not sure how the crank can work loose if the 2 clamp bolts are tight. The retaining/ adjuster bolt isn't that tight, so if the crank is lose it will still work it's way off the spindle.

But, did you have the 2 clamp bolts down to the right torque? If the clamp bolts are tight, and the crank still works lose, either the crank or the BB could be damaged or cracked.

Take the cranks off the bike and look closely at the arms and the BB after cleaning them. Do you see any signs of cracking or warping or something that tells you the spindle or the crank is off spec? Maybe the BB is no longer round at the interface? Maybe the NDS crank is starting to crack?

[Black Dog]

I would not use the cranks before taking a really good look. The NDS crank or the BB could be unsafe to use.

This is not a taper fit type of crank/ BB design. I'm not sure how the crank can work loose if the 2 clamp bolts are tight. The retaining/ adjuster bolt isn't that tight, so if the crank is lose it will still work it's way off the spindle.

But, did you have the 2 clamp bolts down to the right torque? If the clamp bolts are tight, and the crank still works lose, either the crank or the BB could be damaged or cracked.

Take the cranks off the bike and look closely at the arms and the BB after cleaning them. Do you see any signs of cracking or warping or something that tells you the spindle or the crank is off spec? Maybe the BB is no longer round at the interface? Maybe the NDS crank is starting to crack?

This was my thought as well as not using grease. Friction paste yes, grease no.

[cmbicycles]

If you look on the sugino website, they have two different clamp bolt configurations (M5 vs M6) with different torque values. Might be worth a check to see which you have and how tight they need to be. They also suggest you tighten down the spindle bolt after the clamp bolts are tight.
https://www.suginoltd.co.jp/us/products/road/ox.html

[Black Dog]

https://www.suginoltd.co.jp/us/products/road/images/ox-caution-M6.png

https://www.suginoltd.co.jp/us/products/road/images/ox-caution-M5-L.png

[marciero]

I would not use the cranks before taking a really good look. The NDS crank or the BB could be unsafe to use.

This is not a taper fit type of crank/ BB design. I'm not sure how the crank can work loose if the 2 clamp bolts are tight. The retaining/ adjuster bolt isn't that tight, so if the crank is lose it will still work it's way off the spindle.

But, did you have the 2 clamp bolts down to the right torque? If the clamp bolts are tight, and the crank still works lose, either the crank or the BB could be damaged or cracked.

Take the cranks off the bike and look closely at the arms and the BB after cleaning them. Do you see any signs of cracking or warping or something that tells you the spindle or the crank is off spec? Maybe the BB is no longer round at the interface? Maybe the NDS crank is starting to crack?

Nothing like that visible.

[marciero]

Thanks cmb and Black Dog.
Mine has the 4mm bolts. I am probably over tight at this point. I do take care to tighten evenly though. And yes-will be good idea to tighten the spindle bolt after!

[marciero]

This was my thought as well as not using grease. Friction paste yes, grease no.

Well, I used grease to facilitate a tighter torque. Loosening of the cinch bolts has not been an issue-they've been tight when I have loosened them.