Wheel size change = Altered speedo readings?

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Big Jim
Posts: 301
Joined: February 25th, 2015, 9:19 am
Location: Wolverhampton

Re: Wheel size change = Altered speedo readings?

Post: # 16559Post Big Jim
January 12th, 2017, 7:56 am

I make the difference 12.7%
Normally 2.5% is the max recommendation .
If your speedo now reads 50 you are now doing 56 , assuming that your speedo is accurate . They normally read a little more than the actual speed so if your speedo says 50 I would guess you are actually doing 53ish . Check it with a sat nav .

Jim

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sabconsulting
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Joined: July 27th, 2015, 9:49 pm
Location: High Wycombe

Re: Wheel size change = Altered speedo readings?

Post: # 16560Post sabconsulting
January 12th, 2017, 6:30 pm

earthman wrote:Another option maybe, find a place on the dash to mount a Scangauge or similar, apart from giving a speed readout there's other features, it can read/clear some fault codes too,.....all assuming that the vehicle has an OBD2 port in the first place.

https://www.scangauge.com/
Do those electronic ODBII gauges allow you to apply a factor to the speed reading to cater for differing final drive ratio / tyre diameter?

Steve.
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earthman
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Joined: April 22nd, 2015, 2:26 pm

Re: Wheel size change = Altered speedo readings?

Post: # 16566Post earthman
January 13th, 2017, 12:18 pm

sabconsulting wrote:
earthman wrote:Another option maybe, find a place on the dash to mount a Scangauge or similar, apart from giving a speed readout there's other features, it can read/clear some fault codes too,.....all assuming that the vehicle has an OBD2 port in the first place.

https://www.scangauge.com/
Do those electronic ODBII gauges allow you to apply a factor to the speed reading to cater for differing final drive ratio / tyre diameter?

Steve.
Ah, that's a good question, I never thought of that.

I don't recall ever seeing such settings, I have no idea on how it actually works 'out of the box' considering that it's plug & play, can be used on many different vehicles which would have many different wheel/tyre combinations.

I used mine on a Smart car and now a Dmax, the speed reading it gives is the same or within 1mph of the Sat Navs I've used at the time too.

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Gary W
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Re: Wheel size change = Altered speedo readings?

Post: # 16567Post Gary W
January 13th, 2017, 3:21 pm

sabconsulting wrote:
earthman wrote:Another option maybe, find a place on the dash to mount a Scangauge or similar, apart from giving a speed readout there's other features, it can read/clear some fault codes too,.....all assuming that the vehicle has an OBD2 port in the first place.

https://www.scangauge.com/
Do those electronic ODBII gauges allow you to apply a factor to the speed reading to cater for differing final drive ratio / tyre diameter?

Steve.
Scangauge yes, either by adding/subtracting theoretical difference in circumference as a percentage, or by synchronising with GPS speed.

Best wishes

Gary

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rubberrat
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Re: Wheel size change = Altered speedo readings?

Post: # 16614Post rubberrat
January 18th, 2017, 1:26 pm

Another vote for the phone app. I have an outdated spare Samsung Y that I use every day as a speedo - no sim in it but have DiGiHUD downloaded.
Mainly because it has a very large digital readout that I can see without taking my eyes off the road.
Handy now that police will be looking for a potential revenue stream for being 1mph over. Good luck if you can hold + or - 1 mph with an analogue speedo over any distance without staring at the needle rather than the road andits hazards ahead.
I can't so the digi HUD it is.

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sabconsulting
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Location: High Wycombe

Re: Wheel size change = Altered speedo readings?

Post: # 16620Post sabconsulting
January 18th, 2017, 7:00 pm

rubberrat wrote:Another vote for the phone app. I have an outdated spare Samsung Y that I use every day as a speedo - no sim in it but have DiGiHUD downloaded.
Mainly because it has a very large digital readout that I can see without taking my eyes off the road.
Handy now that police will be looking for a potential revenue stream for being 1mph over. Good luck if you can hold + or - 1 mph with an analogue speedo over any distance without staring at the needle rather than the road andits hazards ahead.
I can't so the digi HUD it is.

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Does that use the phone's GPS for speed measurement?

Steve.
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