Maxxis Ardent Skinwall speedometer setup

[Guest]

Hi there.

I bought a maxxis ardent skinwall tyre last week, and it looked so amazing on my bike i bought one for the rear today.

What im struggling with is the setup of the speedometer.

I have a formula where i use the ERTRO Numbers.

3.142x(2×??+622)= circumference in mm.

 

Now what im struggling with, on the sidewall the numbers are showing as follows: 54/56-622

My schwalbe only has 56-622.

 

So im uncertain on which number to calculate. Sunday did 34.8km as per map my ride, speedo was out by 2.8km.

 

Any advice would be appreciated.

[Eldron]

Make a chalk line on the tyre - jump in the bike and roll just over 1 revolution then measure the distance between chalk lines on the ground. Perfect circumference and no math(s)ematic(al) skills required :-)

[Guest]

Ok cool. Wil give it a go. Thanks

[divernick]

Get a GPS?

 

[Mongoose!]

Get a GPS?

 

or a cell phone

[Jewbacca]

Maybe his type of racing is not cell phone or GPS legal?

 

For AR and Freedom Challenge/Nav Challenge races GPS and Cell phones are banned but you still need to know how far you have gone for navigation...... OR he lives in a dodgy area where it is unsafe to ride with anything valuable on your person? (we all do so that's my secondary approach!)

 

Just for the smarty pantses....

 

OP, the marked tire is the most accurate way of getting a reading. We normally do 5 or 6 single rotations and take and average to calibrate ours before a race.

Edited September 5, 2017 by Jewbacca

[Guest]

Maybe his type of racing is not cell phone or GPS legal?

 

For AR and Freedom Challenge/Nav Challenge races GPS and Cell phones are banned but you still need to know how far you have gone for navigation...... OR he lives in a dodgy area where it is unsafe to ride with anything valuable on your person? (we all do so that's my secondary approach!)

 

Just for the smarty pantses....

 

OP, the marked tire is the most accurate way of getting a reading. We normally do 5 or 6 single rotations and take and average to calibrate ours before a race.

 

Thanks for your replies guys. I prefer using it... as a phone. 

 

I will do the single rotations and I have tried a couple of different calculations too. Hopefully I get it sorted soon!