Set-up Tri Pro Cycle computer

Muzz Mackay

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Feb 25, 1997, 3:00:00 AM2/25/97

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I bought a cheapo Tri Pro 5 computer to keep a check on my mph. There
were no instructions and when I phoned the shop the guy said to set the
number at 203 for a 26" MTB wheel, but he didn't have any info for a
700c road bike wheel. Can anyone help me out ?

I thought it would have something to do with the distance of the spoke
magnet from the axle or something scientific like that ?
--
Muzz Mackay
mu...@fyrish.demon.co.uk www.fyrish.demon.co.uk

Phil George

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Feb 25, 1997, 3:00:00 AM2/25/97

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Muzz Mackay wrote:
>
> I bought a cheapo Tri Pro 5 computer to keep a check on my mph. There
> were no instructions and when I phoned the shop the guy said to set the
> number at 203 for a 26" MTB wheel, but he didn't have any info for a
> 700c road bike wheel. Can anyone help me out ?
>
> I thought it would have something to do with the distance of the spoke
> magnet from the axle or something scientific like that ?

Nothing that obscure, thankfully.
The number you enter is simply the circumference of the wheel in
centimetres. That is, the distance the wheel travels in one revolution.
I don't have my Tri Pro instructions to hand which suggested certain
values for 'standard' types of wheel. No matter though, the way to get a
more accurate setting for your computer is to roll the front wheel out
and measure it.

Pump up your tyre to the normal pressure; bring your bike to a flat
stretch of concrete; mark a start position on the ground with chalk;
line up a fixed position on your front tyre with the start position;
roll the bike forward (in a straight line) until the fixed position on
the tyre comes back to the ground and mark this end position with chalk.
Now measure the start to end distance in cm and enter it into the
computer!

Phil

James D Annan

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Feb 25, 1997, 3:00:00 AM2/25/97

to mu...@fyrish.demon.co.uk

Muzz Mackay <mu...@fyrish.demon.co.uk> wrote:
> I bought a cheapo Tri Pro 5 computer to keep a check on my mph. There
>were no instructions and when I phoned the shop the guy said to set the
>number at 203 for a 26" MTB wheel, but he didn't have any info for a
>700c road bike wheel. Can anyone help me out ?

Around 210, depending on tyre size. 208 for a thin tyre.

>
> I thought it would have something to do with the distance of the spoke
>magnet from the axle or something scientific like that ?

No, it's the wheel circumference in cm (so the computer knows how far you
have gone each time the magnet comes around)

I've had one for a few years now, and its worked well enough.

HTH,
James
--
James Annan jd...@pol.ac.uk
Proudman Oceanographic Lab
Bidston, Merseyside, L43 7RA

Dr. David Martin

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Feb 25, 1997, 3:00:00 AM2/25/97

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In article <3312D6...@parallax.co.uk>,
Phil George <phi...@parallax.co.uk> wrote:

+>Muzz Mackay wrote:
+>>
+>> I bought a cheapo Tri Pro 5 computer to keep a check on my mph.
There
+>> were no instructions and when I phoned the shop the guy said to
set the
+>> number at 203 for a 26" MTB wheel, but he didn't have any info for
a
+>> 700c road bike wheel. Can anyone help me out ?
+>>
+>> I thought it would have something to do with the distance of the
spoke
+>> magnet from the axle or something scientific like that ?
+>
+>Nothing that obscure, thankfully.
+>The number you enter is simply the circumference of the wheel in
+>centimetres. That is, the distance the wheel travels in one
revolution.
+>I don't have my Tri Pro instructions to hand which suggested certain
+>values for 'standard' types of wheel. No matter though, the way to
get a
+>more accurate setting for your computer is to roll the front wheel
out
+>and measure it.
+>
+>Pump up your tyre to the normal pressure; bring your bike to a flat
+>stretch of concrete; mark a start position on the ground with chalk;
+>line up a fixed position on your front tyre with the start position;
+>roll the bike forward (in a straight line) until the fixed position
on
+>the tyre comes back to the ground and mark this end position with
chalk.
+>Now measure the start to end distance in cm and enter it into the
+>computer!
+>

Don't forget to sit on the bike as you roll it...

.d

* David Martin - Atherosclerosis and Thrombosis research group *
* http://www.uio.no/~damartin/ david....@biotek.uio.no *
* Lab +47 22 95 84 54 Fax +47 22 69 41 30 GSM +47 90 74 27 65 *

David J Bennett

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Feb 25, 1997, 3:00:00 AM2/25/97

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Muzz Mackay (mu...@fyrish.demon.co.uk) wrote:
: I bought a cheapo Tri Pro 5 computer to keep a check on my mph. There
: were no instructions and when I phoned the shop the guy said to set the
: number at 203 for a 26" MTB wheel, but he didn't have any info for a
: 700c road bike wheel. Can anyone help me out ?

'bout 206/207 for thin tyres, more for fatties.

: I thought it would have something to do with the distance of the spoke
: magnet from the axle or something scientific like that ?

Nahh, just circumference of the wheel.

Muzz Mackay

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Feb 25, 1997, 3:00:00 AM2/25/97

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Thanks all, I knew it would be something logical, and not my axle-to-
magnet-distance pish !