computer problem

Mark Alexander

I'm between a rock and a hard place.

I have a Polar HRM and have just fitted a cateye strada to my race bike. I finished a ride with two different measurements.

I had a look at the respective manuals for 700x23C. Polar says 2070mm and the Cateye says 2096mm so naturally, the numbers are out.

So which is it?

pdstsp

The best one

pdstsp

Sorry - the better one :oops:

MIsterGoof

Mark Alexander wrote:

I'm between a rock and a hard place.

I have a Polar HRM and have just fitted a cateye strada to my race bike. I finished a ride with two different measurements.

I had a look at the respective manuals for 700x23C. Polar says 2070mm and the Cateye says 2096mm so naturally, the numbers are out.

So which is it?

possibly neither.

The diameter of you wheel is just that, not some figure that Polar or Cateye say it is.

Measure the diameter of you wheel and set you computers to that.

The way I measure is

place a chalk mark on the road Place the wheel over the line, lining up the valve with the line. Roll the wheel forward until it has done a complete revolution (i normally do 2, it halves the error), the mark the road again where the valve is at the end of a complete revolution. Now you have 2 marks measure the distance (half it if you do 2 revolutions) ans set up you computers to that value.

Stewie Griffin

Circumference (which is what you are after, not the diameter) = pi times the diameter. MisterGoofs recommendation will work and will give you the circumference, not the diameter.

edit. How anal is it that I left skool 21 years ago and can remember the above and that pi= 3.1415926? Can anyone recommend somewhere that I might be able to get a life from ?

MIsterGoof

Stewie Griffin wrote:

Circumference (which is what you are after,

doh ! was sleeping on a conf call when i posted that

Mark Alexander

thanks guys. I was running 2070mm but they're 2120mm

W5454

MIsterGoof wrote:

The way I measure is

place a chalk mark on the road Place the wheel over the line, lining up the valve with the line. Roll the wheel forward until it has done a complete revolution (i normally do 2, it halves the error), the mark the road again where the valve is at the end of a complete revolution. Now you have 2 marks measure the distance (half it if you do 2 revolutions) ans set up you computers to that value.

When I use this circumference finding method I sit on the bike to replicate riding conditions.
It reduces the wheel diameter slightly and therefore the circumference.

Stewie Griffin

Mark Alexander wrote:

thanks guys. I was running 2070mm but they're 2120mm

:shock: Theres me running the 2096 that Cateye suggested. Where can I get 1 stick of chalk from ? My sister is a school teacher and they dont use the stuff any more as they no longer use "chalkboards" :? . They stopped calling it a blackboard in my Borough a long time ago :roll: .

SteveR_100Milers

Buy a Garmin instead, its got GPS so it cannot possibly be wrong...

Mark Alexander

SteveR_100Milers wrote:

Buy a Garmin instead, its got GPS so it cannot possibly be wrong...

I'd love to Steve but it's a bit out of my price range. Do you use one? Which one?
Stewie, Dover has some chalk

SteveR_100Milers

I use a basic edge 205 and it works fine for me - the satnav function is all I need to be honest, and so long s you trust your online maping skills and you can point your bike to follow a black line then you're away.

Mark Alexander

SteveR_100Milers wrote:

I use a basic edge 205 and it works fine for me - the satnav function is all I need to be honest, and so long s you trust your online maping skills and you can point your bike to follow a black line then you're away.

Hey Steve, I'm bad enough at following the black line around Newport track, let alone a winding road Lol 8) I'd like to take a look next time I see you.

SteveR_100Milers

Mark Alexander wrote:

SteveR_100Milers wrote:

I use a basic edge 205 and it works fine for me - the satnav function is all I need to be honest, and so long s you trust your online maping skills and you can point your bike to follow a black line then you're away.

Hey Steve, I'm bad enough at following the black line around Newport track, let alone a winding road Lol 8) I'd like to take a look next time I see you.

Milers 10 week saturday on the R10/23, or maybe the 25 on the R25/7 mid July?