Wheel size change - Adjusting speedo

marcusjames · Post by **marcusjames** » Fri Jun 19, 2020 6:31 pm

Hi

I've switched the Nomad from the 15" off-road wheels to factory 18" with Yokohama A052s. This has reduced the complete wheel size and as such the speedo is over-reading.

Is there a way to re-calibrate the dash for different wheel sizes?

Many thanks

phil4 · Post by **phil4** » Fri Jun 19, 2020 8:36 pm

There is, yes.

I’ve never done this, so this is general as opposed to specific step by step advice.

The dash has a way of telling it how many rotations per rpm. Pulses I think it counts, and I recall the number default on the atom is around 4000.

I don’t recall if you can change it just using the dash button, I think you can. If not you need a Pc with serial port (or usb to serial) and the serial connector behind the dash.

Sorry this is so vague but as I say, I’ve never actually done it.

Sent from my iPhone using Tapatalk

Post by **stupot** » Fri Jun 19, 2020 8:55 pm

It is in the dash menu under "speedo and RPM"; I think it's called pulses per mile. I remember it from when I would scroll through that particular sub menu to switch the speedo units from MPH to KPH when in Europe.

Post by **stupot** » Fri Jun 19, 2020 9:04 pm

Forgot I had this manual which should help with menus etc

DASH2 instruction manual v35 20Aug 2009.pdf: (497.08 KiB) Downloaded 84 times

marcusjames · Post by **marcusjames** » Sun Jul 05, 2020 5:55 pm

Thanks for the replies.

I finally got around to re-setting the speedo (after another trip out wondering why Sunday drivers were racing past me at 75mph! I suspect I was doing circa 60...whoops)

So a revolution of the wheel is 2 metres. According to the DASH manual it’s 1609/revolution in meters. I assume this means 805 but that seems very low against the 3500 for the 15” wheels. Have I done something wrong? Haven’t had a chance to go for another drive yet.

Thanks.

Post by **John Scherrer** » Sun Jul 05, 2020 11:09 pm

I don't know about the dash setting on the Nomad but this is how it looks comparing the 2 tyres you mention

235/75 -15 700 revolutions / mile circumference 2,305 mm
235/40 -18 796 revolutions / mile circumference 2,025 mm

Changing from the 15" to 18" wheels/tyres without changing the dash calibration would give a 12.1 % speedo over read.
- As you said, if the speedo read 70mph, you'd only be actually doing 62.4mph

Post by **stupot** » Mon Jul 06, 2020 6:34 am

If the dash is currently set at 3500 for the 15" wheels (1609 x 2.305 = 3708) then 18" wheels could be 1609 x 2.025 = 3258. I recall my Atom over read from the factory hence the c6% difference between 3500 dash and 3708 calculated.

Ariel.Club Forum