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28-08-2017, 18:34   #1
adrian.wiedemann
Junior Member
 
Join Date: Apr 2017
Posts: 6
Minimum wheel size setting
Hi,

I've tried to connect the M450 to my trainer last year however I've noticed then that the minimum circumference for a wheel that can be configured is 1000mm (1m). Obviously, this is an arbitrary size limit and effecively prevents the usage of the M450 for this scenario.

I've issued a support ticket with Polar support on this almost a year ago - nothing happened. Maybe anyone here has some hints how to circument this limitation?

(Fun fact: You can set the wheel size to almost 4 meters).

Best, Adrian
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29-08-2017, 06:56   #2
henrikteinvall
Member
 
Join Date: Nov 2011
Posts: 94
Originally Posted by adrian.wiedemann View Post
Hi,

I've tried to connect the M450 to my trainer last year however I've noticed then that the minimum circumference for a wheel that can be configured is 1000mm (1m). Obviously, this is an arbitrary size limit and effecively prevents the usage of the M450 for this scenario.

I've issued a support ticket with Polar support on this almost a year ago - nothing happened. Maybe anyone here has some hints how to circument this limitation?

(Fun fact: You can set the wheel size to almost 4 meters).

Best, Adrian
I had these thoughts as well for my Kurt Kinetic trainer.

At 35 km/h on the road the rear wheel spins at 4.5-5 revolutions per second. If you would have a 1000mm wheel 9.7 revolutions per second. With my trainer I had the trainer spin 12 times per wheel revolution so about 55 times per second. I believe the sensitivity of the sensor is the limit or how the rest of the data transfer handle the data.
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v800 | v650 | H7 | OH1 | Stride sensor | Stryd | Speed sensor | Keo Power Pedals | Balance

Previous watches: s610i | rs800 | rs800cx | cs600x
Previous W.I.N.D sensors: | G3 GPS | G5 GPS | S3 stride sensor | Cadense sensor | Speed sensor | Keo Power Pedals
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30-08-2017, 18:31   #3
adrian.wiedemann
Junior Member
 
Join Date: Apr 2017
Posts: 6
Originally Posted by henrikteinvall View Post
I had these thoughts as well for my Kurt Kinetic trainer.

At 35 km/h on the road the rear wheel spins at 4.5-5 revolutions per second. If you would have a 1000mm wheel 9.7 revolutions per second. With my trainer I had the trainer spin 12 times per wheel revolution so about 55 times per second. I believe the sensitivity of the sensor is the limit or how the rest of the data transfer handle the data.
Right. However, if I've understood the specification of the Cycling Speed and Cadende Specifications and the relevant GATT characteristics correctly, the possible issues pointed out above should not be a problem. With each datagram sent from sensor to collector (bike computer) a counter for the wheel revolutions is sent (besides other data). So if there have been multiple revolutions between distict datagrams, the computer must be capable of calculating the correct speed.

This even works on various apps on e.g. Android (Elite has its app for reading this data), so missing bandwidth should not be a problem here.

Best, Adrian
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