Speedo reading excessively high

[Akzle]

little hoop on der frunt?

[anthraxnz]

so i pulled the speedo apart and it appears there no screw to calibrate it.

I thought the tyres might be part of the problem.

Factory sticker says:
Front: 90/90/17 45S
Rear: 110/90/17 60S

Current Tyres:
Front: 120/80/17
Rear: 120/80/17

Would this change throw the speedo off by 16.7%?

[Mike.Gayner]

By my calculation that only puts it out by about 5%.

edit: And would make the speedo under-read, not over-read.

[Asher]

Same width front rim?
While the tyre has gone down in profile the increase in width to 120 will force the profile up quite a lot. This will probably be causing the readings

Edit: actually that should make it under read, not over read.....

[nzspokes]

http://www.bikebarn.co.nz/echowell-u...-computer.html

Mines been going for about 30,000ks on different bikes.

[george formby]

http://www.bikebarn.co.nz/echowell-u...-computer.html

Mines been going for about 30,000ks on different bikes.

How do you get the magnet close enough to the sensor? The gap on mine has to be <5mm. PITA

[anthraxnz]

I found this calculator: http://tire-size-conversion.com/spee...r-calibration/

Seems to be in the right area when i punch the differences in.

@100km\h i should get 127km\h on the clock which is about right. I see 120.

Pretty sure this is the problem. Thanks for all your help


ps i had to convert it from MPH to KM\h

[leathel]

I found this calculator: http://tire-size-conversion.com/spee...r-calibration/

Seems to be in the right area when i punch the differences in.

@100km\h i should get 127km\h on the clock which is about right. I see 120.

Pretty sure this is the problem. Thanks for all your help


ps i had to convert it from MPH to KM\h

That site didn't work correct for me.... you could enter all sorts of profile and it wouldn't change, change the width and it would?

Bike tyre is width x % = height

120x80% = 96

90 x 90% = 81 profile the smaller the profile the faster it reads

so unless you got the factory & actual around the wrong way above it should be reading slow

[Akzle]

That site didn't work correct for me.... you could enter all sorts of profile and it wouldn't change, change the width and it would?

Bike tyre is width x % = height

120x80% = 96

90 x 90% = 81 profile the smaller the profile the faster it reads

so unless you got the factory & actual around the wrong way above it should be reading slow

rim width. Different from tyre width.

[nzspokes]

How do you get the magnet close enough to the sensor? The gap on mine has to be <5mm. PITA

Old magnet with double sided tape on the rim. Sensor on fork leg. Easy.

[anthraxnz]

That site didn't work correct for me.... you could enter all sorts of profile and it wouldn't change, change the width and it would?

Bike tyre is width x % = height

120x80% = 96

90 x 90% = 81 profile the smaller the profile the faster it reads

so unless you got the factory & actual around the wrong way above it should be reading slow

sorry i typed the front tyre in wrong. its 100 not 120

[FJRider]

The question is ... how long has the issue existed .. ???

Since the OP "Noticed" it .. ??

Or .. since it left the factory .. ???

A little arrow sticker on the speedo dial at all speed limit (actual as opposed to indicated) points and no worries.


Too easy ... ???

[leathel]

sorry i typed the front tyre in wrong. its 100 not 120

in that case they are pretty much the same actual height..

put a 19" wheel on the front :P

[george formby]

Old magnet with double sided tape on the rim. Sensor on fork leg. Easy.

Ah, on ze rim! I've used 19 cat stranglers & a bit of alkathene pipe to stick it on ze spoke. 2 pearls of wisdom from KB & it's only 9:30. Grouse!

[clint640]

Your error does seem excessive. .

Not for a 150, every one I've met over-read the speed to a hilarious degree. I'd go with the wee sticker on the speedo solution, borrow a gps to calibrate it.

Cheers
Clint