My SRM is back and along with it came a new ring sensor designed for mountain bikes. Not free tho’ it cost me $80. Whoa baby sticker shock there but what can ya do. My beef with the mtb SRM is each time one of the bolts on the small chain ring passes the sensor it knocks out the signal – that’s five times per pedal revolution. I was told (or was it sold) the new ring sensor fits inside the small chain ring so doesn’t have that issue. Here is a pic of the old two piece sensor and the new ring sensor.
It sits on the bb axle like so:
and I mean sits – nothing holds it on there. It came with no instructions. This confused me. Anything which is not held onto my bike with velcro, epoxy, zip-ties, locktite or electrical tape falls off – no exceptions including me sometimes… When I put my cranks on the bike the small chainring rubbed the ring sensor enough to rotate it. I tried zip-ties and electrical tape but there is nothing to get a grip on. So a call to the SRM tech folks was made before I broke out the epoxy.
Me: How do I make sure this thing is not ripped off my bike when I start pedaling.
Tech guy: Oh you have to take a file and shave down your small chain ring.
So here I am with a power meter that cost $3,000 and a new sensor that cost $80 and the tech guy is telling ME to take a freakin’ file to it. Who are their designers?? Shouldn’t things like this work without a file manhandling?
Me: You want me to take a file to my $3k power meter?
Tech guy: ok how about this, we’ll send you a new small chainring machined out specially for you and overnight it to you.
Me: Well that sounds like a pretty cool thing to do.
THREE days later the new specially machined out small chainring arrives along with a $40 charge on my credit card. They have my credit card on file and took the liberty of swiping it without asking me. Have at it SRM feckers. I guess I assumed they were gonna send me a free chainring and stump up for the overnight shipping charges – NOT.
So here is a pic of the new chainring.
Dam! Their machining came close to those bolt holes. Does anyone think this is a problem? Should I have just done the filing myself, done a better job than this and saved $40? What if I am 50 miles into a 100 miler and one of these bolt holes decides to peel open? Would that cause me a problem? Would that possibly rip off my $80 sensor?
To additionally inspire SRM confidence consider these facts:
June 2005 Brand new SRM arrived with a factory calibrated slope of 23.6 Hz/Nm.
October 2005 SRM returned to service center for wacko readings. Diagnosis: 2 broken strain guages. Strain guages fixed and unit recalibrated. Returned with a slope of 20.5 Hz/Nm
December 2006 SRM returned to service center not working at all. Replaced cadence sensor and sending coil and unit recalibrated. This time returned with a slope of 19.1 Hz/Nm.
So are these slope numbers random or is the slope sliding. Should I have it recalibrated weekly or monthly? If they did it again for me next week would I have a different number than I received last week? How do I know how hard I am pedaling and how much power I am putting out? Am I getting weaker or is my slope sliding? Should I put this thing up on EBay, buy myself a nice pair of FSA carbon cranks, lose a fat pile of weight off my bike, gain a whole bunch of time wasted messing around in my bike room and go for a ride?