This modern new fangled stuff....

[LikeClockwork]

....what's the theory behind it?

I've just taken this set up off a bike, 68mm shell, and am trying to work out how you tension the bearings, etc. I probably won't reuse it, it is in fact for sale, but I'm intrigued as to the theory in case it does end up being used on something. The non-drive side crank doesn't have a bolt holding it on....?

Excuse my thickness

 

[legrandefromage]

Think of it as the Ahead system on your forks and apply it the cranks and you'll get it.

 

[legrandefromage]

Some's spilt paint on the cranks btw...

 

[LikeClockwork]

Some's spilt paint on the cranks btw...

Ah right, thanks, that's kind of what I figured but googling it, there's a few similar systems around, hollowtech etc, lots of different brand names for a similar set up I presume.

 

[catf]

Re:

pretty sure that design should use a spring washer to do the tension. teh ahead-like designs would have the axle built into the drive side and teh other arm clamped on after pretensioning. imo they should just use a pipe like on bmx cranks, impossible to sideload teh bearings with a pipe

 

[legrandefromage]

Re: Re:

pretty sure that design should use a spring washer to do the tension. teh ahead-like designs would have the axle built into the drive side and teh other arm clamped on after pretensioning. imo they should just use a pipe like on bmx cranks, impossible to sideload teh bearings with a pipe

There are no spring washers. Never have been either. Think 'Ahead' and you'll get it.

 

[MarinMartin]

Re:

Not sure if the same as yours but I had a similar set to that and they used a special tool to pre-tension the cranks before tightening them. Think they were hollowtech actually. tightened them from the non driveside.

 

[klunkrider]

Re: Re:

pretty sure that design should use a spring washer to do the tension. teh ahead-like designs would have the axle built into the drive side and teh other arm clamped on after pretensioning. imo they should just use a pipe like on bmx cranks, impossible to sideload teh bearings with a pipe

There are no spring washers. Never have been either. Think 'Ahead' and you'll get it.

These diagrams refer to GXP (sram) and Hollowtech 2 (shimano) cranks. OP is about Raceface cranks which do infact use a preload elastomer (same idea as a spring washer) on the spindle.

 

[LikeClockwork]

Re:

Just taken these extra picks, as I'm still confused!!

For reference, I took them off a bike I split, they came fitted with the BB in the background, a Shimano item. Starting to wonder whether to use them now, so really want to get my head around how to set them up properly. Mind you, I've just seen what the cost new :shock:

 

[catf]

Re:

looks like that thing on the nondrive side where the axle meets the arm is teh tensioner, give it a poke to see if its springy. if so they should just slide into the bb and you can use the bolt to attach the driveside like isis/octalink

point was all the crank pics on this thread are taperlock, which need something springlike to do the tensioning, lgf referring to ahead was just confusing things cos he was talking about ht2 and some others that use a preloading bolt, like an ahead top cap, and an arm that clamps on the axle with pinch bolts, like an ahead stem. that tool in the pic is for the preload bolt on ht2 cranks, allen key does the same job