Need help with dB 4LW wireless computer

[Bolo Grubb]

for those of you that have the db 4LW did you have any problems calibrating it?

My brother-in-law just got one and it is reading 2-3 mph slower then my Cateye.

we are both running 700x23 tires, but his instruction did not have the setting for that size tire, so he had to do the math. There was a formula there to use.

Seems very strange to me that his speed and distance are so far off for mine.

Any help would be appreciated

[Auperator]

Do you still have instructions for the dB 4LW? I need to set my tire diameter and the setting on this computer is so ridiculous, you need some sort of code.
Thanks,
Andrew

[formulaben]

http://www.filzer.com/img/products/7-instructions1.pdf

[kdelong]

I suggest that you do the roll out, option 2, to get your wheel circumference. This is the most accurate way.

Just for the record, there are variations in size between brands of tires and even between individual tires of the same make and model. Just because it says that it is 700X23 does not mean that it is exactly that size. It means that it is close enough to that size to be classed as that size. It is easier to say that than 703X23.027 or some such nonsense. Even the pressure that the tire is pumped to will effect the size. It does not take much variation in sizes, as well as a possible minor math error, to throw your speed off from each other by 2 -3 MPH.