How to correct the speedo on the VX with non-OM tyres?

[TeeGee Lurker Find all posts View Profile Close TeeGee]

Hi All,

Is there an existing thread on this topic?

On my 2011 diesel VX I have changed to 17" rims and fitted 265/65/17 Bridgestone D694LTs. My thoughts were to get more rubber between my rims and the rocks on our gravel roads, and besides, Bridgestone don't make my preferred D694LT in 18". As these are standard sizes for the GXL, I thought there would be no problem with the changeover. But the speedo is reading way low.

So my question is: how do you guys correct the speedo reading when you fit non-OM rims and tyrers?

TIA
Cheers
TerryG

Edit: Oops speedo is reading High - about 10%

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

265/65 17 is as close as makes no difference to 265/60 18. If anything the 17" tyre will be slightly taller by virtue of the size and then taller again because AT tyres generally have more tread depth than a highway type tyre such as the OEM Dunlops. I suspect your speedometer was reading low before as well. Have you done a comparison against a GPS with both rims/tyres?

[Ages Senior Member Find all posts View Profile Close Ages]

My speedo with stock wheels reads about 115-117 when the gps shows 110


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I am here: http://maps.google.com/maps?ll=-33.281347,115.714941

[TeeGee Lurker Find all posts View Profile Close TeeGee]

265/65 17 is as close as makes no difference to 265/60 18. . . . . .

Yeah, That's what I thought - both about 30.5" rolling diamater.

I suspect your speedometer was reading low before as well. Have you done a comparison against a GPS with both rims/tyres?

Speedo at 100kph, GPS shows 92kph.

Rims and tyres fitted prior to delivery, so haven't done a comparison.

Cheers
T.

[yowie Advanced Member Find all posts View Profile Close yowie]

[QUOTE=TeeGee;312012]Hi All,




I fitted D694LTs to my GXL, on 17", in the size 275/65/17. It is about 13mm larger in diameter and gives a closer reading to the true speed.

Yowie.

[wooley Avid PP Poster! Find all posts View Profile Close wooley]

Yeah as they are a slighter bigger tyre the speedo should under read which means it is way out from manufacture. Maybe fit 5% larger tyres again to make up for it.

[TeeGee Lurker Find all posts View Profile Close TeeGee]

[QUOTE=yowie;312022]

Hi All,


I fitted D694LTs to my GXL, on 17", in the size 275/65/17. It is about 13mm larger in diameter and gives a closer reading to the true speed.

Yowie.

Thanks Yowie - Looks like I should have asked the question here before I chose the 265s. How are the 275s for clearance in the wheel arch and in the spare carrier.

This high speedo reading, of course, has a knockon affect that the ODO will read 10% too high and so onto service due points and also Warranty limits - Bugga.

Cheers
T.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

[QUOTE=TeeGee;312026]

This high speedo reading, of course, has a knockon affect that the ODO will read 10% too high and so onto service due points and also Warranty limits - Bugga.

Cheers
T.

This one I am not so sure of. There was a post in the dark ages by someone comparing a scangauge and GPS and speedo/odo which indicated the odometer was pretty close to spot on and it was only the speedometer that was out, cannot recall the details though other than the raw data was ok but it was 'adjusted' down. I know with my Commode you can 'tune' the speedo accuracy if you want to account for different tyres/diff ratios etc (and tune other things like kW ). By the way I too have 275/65s though they are on my lifted 120 and the speedo went from -4kph to about -2kph.

[yowie Advanced Member Find all posts View Profile Close yowie]

[QUOTE=TeeGee;312026]

Thanks Yowie - Looks like I should have asked the question here before I chose the 265s. How are the 275s for clearance in the wheel arch and in the spare carrier.

This high speedo reading, of course, has a knockon affect that the ODO will read 10% too high and so onto service due points and also Warranty limits - Bugga.

Cheers
T.

Fits the spare carrier without any problems, no problem in the wheel arches either. The 275's also give a higher load carrying capacity too, as compared to the 265's. Cannot remember the figures, but go to the Bridgestone website and it will give you load ratings for the different tyre sizes.

Yowie.