computer sensor on trike

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3tyretrackterry

Active Member
Location
East Midlands UK
hello
I have given in and bought a computer for my trike at present it is fitted to my front wheel. the magnet is on my spokes within 3 inches of the centre of the wheel. is this about right and if it isnt what effect will having it near the middle of the wheel have on my speed reading if any
 

Davidc

Guru
Location
Somerset UK
It shouldn't matter where it is.

The time taken for a revolution of the wheel is the same at all points, and cycle computers measure the time between successive passes of the magnet, which is just that.
 

marc-triker

Veteran
Location
South Derbyshire
mine is on my rear wheel on the Classic. i didnt know but thought the front wheels woulnt be as accurate. let me try to explain my logic. in the corners both front wheels are travelling at different speeds depending on how sharp the turns are. i am not to bothered by speed as such but my distance measurements are. the rear (26") being in the middle of the track i figured it the best place 2 mount my sensor...
 

dataretriever

New Member
Location
NW London
I don't think it really matters where you put it when you take cornering and wheel slippage into account. Front wheel mounting will even itself out between inside and outside line in bends unless you only ever take left hand bends, and the rear wheel will slip occasionally on gravel and mud. The few metres difference various mounting points would give you over a decent length ride would be negligible. A GPS system won't improve things as they can only give accuracy to a few metres. It's more important to be accurate with your wheel measurement - use chalk and a tape measure to physically measure the circumference rather than relying on published tables as variations in tyre types and pressure will give different measurements.

You could try four computers; one on each wheel and a GPS system then average the readings out after a ride for more accurate trip analysis, but personally I'm not bothered whether it's 20km or 20.02Km; I'll still have a grin and mud splatted over me which reminds me, I ought to put the mudguards back on.....
 
OP
OP
3

3tyretrackterry

Active Member
Location
East Midlands UK
thanks again for the replies i was wondering because when i was out on trike the other day it told me i was doing 18mph on flat and i didnt think i was i know the distance is about right as ive checked it against a map and on one of the route planner websites was just wondering about my speed reading
 

byegad

Legendary Member
Location
NE England
3tyretrackterry said:
and i did physically measure the circumference as well and came up with 1570mm for a 20 inch wheel wearing a 20 x 1.35 (35-406) schwalbe marathon slick

That sounds about right, I use 1602 (calculated not measured) for my 406 wheel with 2" Big Apples.
 
marc-triker said:
mine is on my rear wheel on the Classic. i didnt know but thought the front wheels woulnt be as accurate. let me try to explain my logic. in the corners both front wheels are travelling at different speeds depending on how sharp the turns are. i am not to bothered by speed as such but my distance measurements are. the rear (26") being in the middle of the track i figured it the best place 2 mount my sensor...

You are right..... the same error can occur with any route as well though

Imagine a sweeping curve - the trip out and home will be different for the sae reasons.
 

byegad

Legendary Member
Location
NE England
But rear wheel spin can spoil a accurate reason too. I often spin the rear wheel a turn or two as I pull out of side roads and the rear wheel goes over loose gravel.
 
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