dstrong 

I've been mapping out a few new routes in unfamiliar areas lately on RWG (including a certain 56 mile half-ironman bike route somebody I know is going to ride later this year ), and it occured to me that it would make sense if my bike computer was in sync with the mileage produced by RWG to lower the chances of getting lost.

My computer (VDO C3) has 2 bike settings...and I have 2 bikes...but I've never used the 2nd bike feature, figuring it was "close enough" when I moved the computer from one bike to the other (I run 700x25 GP4000 on both).

Yesterday's ride was super windy, so I decided to try to check the accuracy, knowing I wasn't going to be setting any land speed records.

First I reset the "Bike 1" setting using the "measure the distance the wheel travels in one revolution" method, which resulted in 82.5 inches. Interestingly, this corresponded in the instructions to a 700x20 tire.

"Bike 2" was set to 84.5 inches, per the table in the instructions for a 700x25 tire.

I was riding a 23 mile out-and-back route according to RWG, so I decided to use the Bike 1 setting on the outbound and the Bike 2 setting on the return. I also chose two intermediate points each direction and logged those legs also.


Results:
Outbound/return distance according to RWG: 11.5 miles
Outbound Bike 1 reading: 10.85 (-5.65%)
Return Bike 2 reading: 11.5 (+2.96)

The short legs actually provide some confusing data...so I'm going to ignore it for right now and reset Bike 1 and 2 based on the data above.

New Bike 1 setting: 83.5 (was 82.5)
New Bike 2 setting: 84 (was 84.5)

Totally anal retentive, I know...I figure it might come in handy someday to be exact.