Hollowtech cranks and sensor fitting

[x332race]

I want to fit the pedelec sensor to the left side of my bike but have a Hollowtech crank. There is almost no clearance between the crank arm and the crank itself....has anyone fitted a pedelec sensor to Hollowtech cranks?

 

[eddieo]

Is yours a two piece sensor? My wisper Daahub sensor is and was fitted OK....

here is a pic ( poor quality as taken with phone)

 

[Deleted member 4366]

There was a guy on the forum that did one about a year ago, which, IIRC, he did by makinging the hole in the magnet ring bigger and then he glued it with epoxy putty. He didn't fit the sensor in the normal way, but instead bent the metal ring back and fixed it to his chainstay again with epoxy putty.

If I were to do it, I'd fix the sensor in the normal way and then dremmel out the hole in the magnet ring to the exact size for a tight fit on the spindle and then put a fillet of silicone sealant on each side before re-fitting the pedal. That should be strong enough as there's no force on the magnet ring

 

[x332race]

d8veh.....I have seen the thread you refer to and I was considering going down that route, however I like idea of dremmelling out the hole but I would do it to the sensor so it fits over the bottom bracket.

eddieo....any chance of a better quality photo....I cant really see what is going on in the one you have posted?

As you can see from attached photo, I do not have much clearance.

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[eddieo]

my crank looks exactly the same as yours...would take better pic but son has my camera and he is at Uni

what bike is it? what kit is it? does sensor split?

 

[Deleted member 4366]

It doesn't look like the normal magnet disc will fit Another possibility is to mount the sensor on the other side somewhere behind the chain-wheel and then stick the magnets directly to the chainwheel without using the disc. You can either prise them out of the disc or buy some more on Ebay for a few pence each. just search on" Neodymium". the only thing you need to figure out is which way up they go - as they'll only work one way up (all the same way). You don't need glue, but if you get them working OK, you can eeither superglue or epoxy them permanently in place.

 

[x332race]

It doesn't look like the normal magnet disc will fit Another possibility is to mount the sensor on the other side somewhere behind the chain-wheel and then stick the magnets directly to the chainwheel without using the disc. You can either prise them out of the disc or buy some more on Ebay for a few pence each. just search on" Neodymium". the only thing you need to figure out is which way up they go - as they'll only work one way up (all the same way). You don't need glue, but if you get them working OK, you can either superglue or epoxy them permanently in place.

Sounds too complicated for me to not use the sensor wheel....I have same problems with clearance on the other side too. I think I can gain a few mm clearance if I fix the left crank slightly further out...not ideal but may work.

Its on a Cannondale but it is not the original crank. 2 piece sensor as normal.

 

[eddieo]

I think I can gain a few mm clearance if I fix the left crank slightly further out...not ideal but may work.

Mine was fitted back in June and have had no problem with it.....Its only a few mm?

 

[JuicyBike]

3mm ish. I can measure tomorrow...

 

[JuicyBike]

Between 2.5 and 3 mm. Christmas wishlist = +digital calipers...

 

[x332race]

Between 2.5 and 3 mm. Christmas wishlist = +digital calipers...

Thanks for that...its going to be a tight fit to get the sensor wheel in..

 

[Deleted member 4366]

You can thin them down a bit by grinding off the thin boss on each side. Also, I've made more space on some bikes by grinding a few mm of the back side of the pedal crank with an angle grinder, but I'm not sure you can do that with hollowtech cranks - depends what type you have.

 

[x332race]

Looking at the crank arm, it should be possible to take a mm or so off the back of it if necessary...thanks you have given me several options that I have not considered....I feel more confident in being able to make something work now.