Gadget on rear chain stay of TdF bikes

zacklaws

Veteran
Location
Beverley
Anyone any idea what the "thing" is on the left hand rear chain stay is that pokes downwards about an inch or two, some bikes have them some don't, but when you spot them they stand out a mile? I initially thought it was for cadence, but after seeing some close ups of a rear chain stay yesterday with the item fitted, I also saw a bit further up the chain stay towards the BB is what looks more like a cadence sensor fitted on the top side of the chain stay as well.

Wireless cycle computer working off back wheel?
 

maurice

Well-Known Member
Location
Surrey
Anyone any idea what the "thing" is on the left hand rear chain stay is that pokes downwards about an inch or two, some bikes have them some don't, but when you spot them they stand out a mile? I initially thought it was for cadence, but after seeing some close ups of a rear chain stay yesterday with the item fitted, I also saw a bit further up the chain stay towards the BB is what looks more like a cadence sensor fitted on the top side of the chain stay as well.

Wireless cycle computer working off back wheel?

Shouldn't need a very big sensor for a normal bike computer, I was thinking the Polar CS600 power meter when I first read this, but that goes on the right hand chain stay, i.e.

overview.jpg
.
 
OP
OP
zacklaws

zacklaws

Veteran
Location
Beverley
I find it annoying that searching through all the photo's on line, I cannot find one with the item fitted, but I have suspicions it could have something regarding power meters. even more so seeing that polar one which measures vibrations from the chain, but as you say it is on the wrong side.
 
Timing transponders.

That's what I thought. They're on every bike and are exactly the same, same place as well.
 
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