# Electronics, Lighting, & Gadgets - Cycle Computer with 29" Front Wheel

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pOrk
11-12-08, 10:27 PM
I am running a 29X2.25 front tire and the Cycle Computer I bought only has a 29X1.75 size for a 29 " wheel, how do I find out how many millimeters the outside of the wheel equals? I can't find a metric tape measure for the life of me.

mechBgon
11-12-08, 10:30 PM
Measure the distance the tire rolls in one revolution while you're sitting on the bike. Then convert it from inches to millimeters and there you go. One inch is 25.4mm.

bbgobie
11-13-08, 09:27 AM

Hint: google does math and conversions.

For example (type into google): 5in=?mm
10*5=?
:crash:

pOrk
11-13-08, 09:48 AM
I used a standard fabric tape measure the first time and the reading is way off on my computer, I followed the directions exactly with the same result. Hence my reasoning for asking on here, I'm hoping someone has done this with good results. My computer is reading on average bout 2 mph off.

TromboneAl
11-13-08, 10:08 AM

It even has spelling advice! ;)

resipsa
11-13-08, 10:17 AM
Just do the roll-out as mechBgon advised; don't worry about computing it, as you're likely going to be off in the inital measurement, and don't worry about the instructions as they're not going to take into account your exact tire size + flattening due to weight.

A small dab of paint (or whatever is of similar viscosity, really) on your tire will make a good pair of marks on the ground, the distance between which you can then measure.

jsharr
11-13-08, 10:43 AM
http://knowledgebase.cateye.com/questions/45/What+tire+size+should+I+use+for+my+29er%3F

You are off by 2 mph at what speed? How are you averaging this? The deviation should be linear. How do you know it if off by 2 mph, what are you comparing to to reach this number?

pOrk
11-14-08, 08:40 PM
^ That link is great, as is the paint blob advice. Thanks guys.

jsharr, I was averaging what I thought to be 10-12 mph and used the average speed on my cycle computer compared to my buds who was riding either side by side or close behind on some single track, as well as asking while riding what he was reading and what mine was reading. His might be off some too though I suppose, although his correct tire size was in the booklet that came with his computer.