PAS not working with tapered crank

[John3mary]

I received the AW rear wheel conversion kit from Amazon. My bike shop looked at it and there are two problems. First problem is that my Shimano crank is tapered and the PAS takes up room so that my crank will not slide back on all the way, I can tighten the bolt but the crank is not seated all the way and the bike shop said it will eventually wear out the crank arm since it is not tightly seated. My bike mechanic said the only thing he could think of is to grind off some of the crank. Is there a PAS system that will work in this case or do I need to buy a grinder? Also the derailer rubs in top gear and the bike shop said no way to fix except to adjust it and lose the top gear.

 

[Benjahmin]

Grinding crank bosses is quite common on here. It can be difficult to get the ground face flat and square, so I marked round the boss rim with a marker pen before grinding. Probably best to seat crank without pas and measure the existing gap. Then measure pas thickness, this'll tell you how much you need to remove. Up to 3mm should be fine. The other solution is to change the bottom bracket for a longer spindle.
How many gears have you got? If deraileur is rubbing then the wheel may need dishing, but check it's centering first. It's a fairly simple, if laborious, excercise. Loosen spokes on gear side by one quarter turn, tighten spokes on opposite side by one quarter turn. Check wheel in the frame.
It may be possible to put a spacer washer on the gear side, again check the centering.

 

[Nealh]

Which pas is it, a one piece V12L or a two piece unit ?
Another option is to replace the BB with a longer unit, depending on the size currently fitted. The reach of the derailleur may not be enough.

 

[vfr400]

You can grind afew mm off the back of the crank without any harm. That's the quickest and simplest solution.

 

[John3mary]

Thanks for all the great advice. I am new to doing my own bike repair or maintenance so I a learning all about the terms and crank bosses what BB means, etc....

The PAS is a single piece and works very well, I just had it out yesterday, but as I said, my local bike repairman said I need to grind it down or something, he did not suggest a longer spindle. I do not have a grinder, but I might add one to my tool kit. I would like to get a hand grinder, but I am sure a bench mounted one would be better, just not as portable.

Thanks again to all, I appreciate your help.

John

 

[Sturmey]

Thanks for all the great advice. I am new to doing my own bike repair or maintenance so I a learning all about the terms and crank bosses what BB means, etc....

The PAS is a single piece and works very well, I just had it out yesterday, but as I said, my local bike repairman said I need to grind it down or something, he did not suggest a longer spindle. I do not have a grinder, but I might add one to my tool kit. I would like to get a hand grinder, but I am sure a bench mounted one would be better, just not as portable.

Thanks again to all, I appreciate your help.

John

I used a hacksaw to slice about 3 mm off my crank. It was easy enough in my case as the crank was made of aluminium alloy, so was fairly soft. I used a file afterward to clean it up. Took about 20 minutes. You probably need the grinder for a steel crank.

 

[Kwozzymodo]

Buy a two- piece PAS. The sensor should fit between the bottom bracket and frame no problem. You will need to cut out the centre of the magnet ring until it sits nicely on the chainset behind the inner chainring. Epoxy the magnet into place. You can then put the chainring back on the square taper bracket and you shouldn’t have any problems with binding up, etc.

It is easier to butcher plastic than metal.....!

 

[John3mary]

I used a hacksaw to slice about 3 mm off my crank. It was easy enough in my case as the crank was made of aluminium alloy, so was fairly soft. I used a file afterward to clean it up. Took about 20 minutes. You probably need the grinder for a steel crank.

I can do that, I have a hack saw and mine are aluminium, so I can give that a try. Thanks for sharing.

 

[John3mary]

Buy a two- piece PAS. The sensor should fit between the bottom bracket and frame no problem. You will need to cut out the centre of the magnet ring until it sits nicely on the chainset behind the inner chainring. Epoxy the magnet into place. You can then put the chainring back on the square taper bracket and you shouldn’t have any problems with binding up, etc.

It is easier to butcher plastic than metal.....!

I might try the two piece PAS if I don't have a new hacksaw blade. -)