Road Bike, Cycling Forums banner
1 - 8 of 8 Posts

· Cycling induced anoesis
Joined
·
13,019 Posts
roadandtrail said:
I am setting up my computer on a new Roubaix Pro. It has tires that read 700x23/25c. What tire size should I set my computer at?
This is Spec's description:
Comfortable large volume 25c casing, merged with fast-rolling 23c Dual Radius Tread
Seeing as the casing is 25c, I'd go with that.
 

· RoadBikeRider
Joined
·
1,053 Posts
The size listed on the tire does not mean a whole lot as far as setting up your computer accurately. I have seen HUGE variances from brand to brand. The most accurate way to set up the computer is by doing a roll out test to find the circumference then put your numbers into the computer..radius, diameter or circumference or whatever it may be based on your roll out.
 

· Registered
Joined
·
3,431 Posts
andulong said:
The size listed on the tire does not mean a whole lot as far as setting up your computer accurately. I have seen HUGE variances from brand to brand. The most accurate way to set up the computer is by doing a roll out test to find the circumference then put your numbers into the computer..radius, diameter or circumference or whatever it may be based on your roll out.
Some people's experience may be different, but I've always had reasonably accurate mileage readings from simply using the tire size chart for the computer. This is for several different computers and various tires. Like, within one or two tenths in 10 miles and/or a very tiny percentage difference between my computer(s) and my Garmin (i.e. my daily commute - if garmin says 12.36, computer may say say 12.2 to 12.4). So, what I'm trying to say is depending on ones' tolerance for accuracy, that's what I'd try since it's easiest. Most likely plenty accurate.

Interestingly, for my two sets of wheels, I'm not finding a meaningful difference in mileage readings between my Michelin 23 mm tires and my Schwalbe 25mm tires. They do look different in size (haven't actually measured), but the overall mileage difference is very minor - well within the meaningless differences we get when comparing ending mileage among the people I ride with. Typically, among 4-5 people, we'll be within 1/2 to 1 mile of each other in a 20-30 mile ride. I'm not concerned with being closer than 1/2 mile or so for a 20 - 30 mile ride, but others may want to be more accurate.
 

· Resident Curmudgeon
Joined
·
13,390 Posts
step 1 pump your tires up the the pressure at which you normally ride.
step 2 go get a friend/wife to help you.
step 3 mark a fine line on the tire sidewall using a ballpoint pen or similar.
step 4 get on the bike and have your friend tell you when the mark is exactly straight down , closest to the pavement.
step 5 make a mark on the pavement that corresponds to the mark on the tire
step 6 "ride" the bike slowly along a wall (I use a garage wall) for exactly 1 revolution. you'll need your friend to tell you when this happens. try to keep the front wheel traveling in as straight a path as possible
step 7 mark the pavement as in step 5
step 8 carefully measure the distance between the two marks & convert to metric (centimeters)
step 9 set your computer to this number
 

· Registered
Joined
·
217 Posts
Mr. Versatile said:
step 1 pump your tires up the the pressure at which you normally ride.
step 2 go get a friend/wife to help you.
step 3 mark a fine line on the tire sidewall using a ballpoint pen or similar.
step 4 get on the bike and have your friend tell you when the mark is exactly straight down , closest to the pavement.
step 5 make a mark on the pavement that corresponds to the mark on the tire
step 6 "ride" the bike slowly along a wall (I use a garage wall) for exactly 1 revolution. you'll need your friend to tell you when this happens. try to keep the front wheel traveling in as straight a path as possible
step 7 mark the pavement as in step 5
step 8 carefully measure the distance between the two marks & convert to metric (centimeters)
step 9 set your computer to this number
You can also do this without someone else's help by riding thru a water puddle. Just measure from the front edge of the puddle to the front edge of the next water spot (one revolution later).
 

· RoadBikeRider
Joined
·
1,053 Posts
I do the roll out by putting a small dot of paint or nail polish on the tire tread and roll along a straight line on the bike in the garage or any flat surface while the paint is still wet. Then go back and take measurements..this does not require an assistant.
 
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top