Mileometer distance - wheels change

[denz1968]

Hi there all

Is there anything that needs doing when changing from 16" factory claytons to Navis 17" swamper tyres.
Just been down to cornwall and i have a 60 mile discrepancy with what i believe the mileage to be using google maps and the odometer reading on my trip

Any suggections

Thanks

Denz

 

[archersam]

how does your speedo read? In the 6.1 I understand there is a setting to change wheel/tyre size although havent botherd with it myself.

 

[Scottish Scrutineer]

Hi there all

Is there anything that needs doing when changing from 16" factory claytons to Navis 17" swamper tyres.
Just been down to cornwall and i have a 60 mile discrepancy with what i believe the mileage to be using google maps and the odometer reading on my trip

Any suggections

Thanks

Denz

What size of swamper tyres? If they are a larger circumference that standard, then the speed/distance will be inaccurate compared to previous

 

[denz1968]

how does your speedo read? In the 6.1 I understand there is a setting to change wheel/tyre size although havent botherd with it myself.

I have checked it, and it is what would be considered correct.

Where is the wheel/tyre size change please

 

[denz1968]

What size of swamper tyres? If they are a larger circumference that standard, then the speed/distance will be inaccurate compared to previous

235/65R17 Falken Wildpeaks

 

[archersam]

235/65R17 Falken Wildpeaks

in which case your speedo is now reading more accurate than it was before. At least in my case having gone from some standard size on my Devonports where my speedo underread as most do as it is iillegal to have one overreading by the manufacturer i beleive. Now on same size tyres my speedo is more accurate than it was although it does now underread by 1mph. So 30mph on my speedo is 31 on my sat nav and the numbers are similar across the range.

As I almost exclusively use my sat nv speed I dont worry about the dashboard. As the speed is correct I assume the mileage is too.

 

[denz1968]

east in my case having gone from some standard size on my Devonports where my speedo underread as most do as it is iillegal to have one overreading by the manufacturer i beleive. Now on same size tyres my speedo is more accurate than it was although it does now underread by 1mph. So 30mph on my speedo is 31 on my sat nav and the numbers are similar across the range.

As I almost exclusively use my sat nv speed I dont worry about the dashboard. As the speed is correct I assume the mileage is too.

Yes mine was within 1mph on the whole across the range upto 60mps (no motorway to test on near me).

However i drove a 6.2 mile route which I know is that distance from GPS watches (10k = 6.2 miles) and the app confirmed it as 6.2miles, but the odometer read 5.6 miles

 

[The Bear78]

235/65/17 usually corrects the factory speedo over read for vans that came with 17" wheels from the factory. Standard 16's are smaller (the tyre OD...) and the speedo is calibrated differently. 235/65/17 will, I believe, under read on a 16'" van.

 

[TallPaul_S]

Your speedometer would have been the usual slightly under reading, but the odometer would have been correct with your original wheels.

Looks like your odometer is about 10% out now, which will also affect your mpg figure as the van things it's done less miles than it's actually done.

Check your new tyre size against the old size at Alloy Wheel & Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit to see what the percentage difference is.

If you've got a T6 you can alter the wheel size with VCDS.

 

[Bav]

Just been down to cornwall and i have a 60 mile discrepancy

What's that discrepancy when expressed as a percentage?

 

[Pauly]

Do your research and read thoroughly before making any changes, there are two different wheel circumference settings within the vehicle that can be adjusted but it needs to be done correctly and some settings are one way tickets and cannot be reverted, if you get the settings wrong it can mess with your ACC function

 

[denz1968]

What's that discrepancy when expressed as a percentage?

9% lower on the odometer compared to what it should have been

 

[Bav]

9% lower on the odometer compared to what it should have been

I guess that's one way to keep the mileage down.

 

[TeeCeeJay]

I really want to get rid of my Claytons and put some 18s on, but threads like this make me over think it and doubt it. For some reason more so than deciding to take a saw to the van to put a huge hole in the roof and sides!

All the under and over speed and distance calculations make my head hurt.

 

[WinFreak]

With my 265/40/20s the speedo reads exactly 70mph when my Waze gps says 70 so it's spot on, with the standard 17s it'll do 70 on the speedo and like 65 on the gps

Actually prefer having the 20s on for that, you know doing 50 in a average speed area is actually 50 and you're not guessing oh maybe I can do 54 and it'll be ok.

 

[denz1968]

I really want to get rid of my Claytons and put some 18s on, but threads like this make me over think it and doubt it. For some reason more so than deciding to take a saw to the van to put a huge hole in the roof and sides!

All the under and over speed and distance calculations make my head hurt.

It doesn't bother me in so much as my speed is good v gps speed. So my only niggle is the kilometre difference and then only because my MPG is lower than it should be.
Otherwise its miles in the bag for me as my mileage if I ever come to sell is lower than reality

 

[TeeCeeJay]

It doesn't bother me in so much as my speed is good v gps speed. So my only niggle is the kilometre difference and then only because my MPG is lower than it should be.
Otherwise its miles in the bag for me as my mileage if I ever come to sell is lower than reality

So you didn't do any coding adjustment to your van? I've just read this thread and it made my brain bleed even more than this one.

I'm on factory 16 Claytons and want to go to Wolfrace X10X with 235/50/18 tyres.

Will they fit.com says that with my new set up the Speedo will say 60mph when in reality I'm doing 56mph. But this is already the case now when I've checked with GPS against the 16s.

Does this mean the error will be cancelled out or doubled? Will my new setup mean that at Speedo 60 I'm doing 60 or 50?

Sorry if this is blindingly obvious to everyone else, I'm just getting wrapped round the axle with double negatives!

Or just shut up TCJ, stick the new shoes on and enjoy the van?...

 

[TallPaul_S]

So you didn't do any coding adjustment to your van? I've just read this thread and it made my brain bleed even more than this one.

I'm on factory 16 Claytons and want to go to Wolfrace X10X with 235/50/18 tyres.

Will they fit.com says that with my new set up the Speedo will say 60mph when in reality I'm doing 56mph. But this is already the case now when I've checked with GPS against the 16s.

Does this mean the error will be cancelled out or doubled? Will my new setup mean that at Speedo 60 I'm doing 60 or 50?

Sorry if this is blindingly obvious to everyone else, I'm just getting wrapped round the axle with double negatives!

Or just shut up TCJ, stick the new shoes on and enjoy the van?...

56mph GPS on 60mph Speedo means the Speedo is currently reading at 107% out, I'm guessing your new tyres will be about 7% bigger than the 16's?

If so, then yes your Speedo should then read almost exactly accurately. However, it will mean that your odometer will be under reading by the same percentage, and your mpg figure will also be off as the van will think it's done less miles for the same fuel.

At 42mpg that's a 3mpg difference with a 7% bigger wheel.

Willtheyfit.com doesn't take into account the over reading that most speedometers have, so you just need to take that into account. Ie, if the tyres are 7% bigger your speedometer will read 7% less, at the same real speed. So 60mph on 16's would read as 56mph on the new tyres.

But, if you have VCDS I'd still adjust the gearing so your odometer and mpg reads correctly.

 

[mmi]

then only because my MPG is lower than it should be.

MPG can be adjusted separately - an adaptation in 17-Instruments

 

[TeeCeeJay]

56mph GPS on 60mph Speedo means the Speedo is currently reading at 107% out, I'm guessing your new tyres will be about 7% bigger than the 16's?

If so, then yes your Speedo should then read almost exactly accurately. However, it will mean that your odometer will be under reading by the same percentage, and your mpg figure will also be off as the van will think it's done less miles for the same fuel.

At 42mpg that's a 3mpg difference with a 7% bigger wheel.

Willtheyfit.com doesn't take into account the over reading that most speedometers have, so you just need to take that into account. Ie, if the tyres are 7% bigger your speedometer will read 7% less, at the same real speed. So 60mph on 16's would read as 56mph on the new tyres.

But, if you have VCDS I'd still adjust the gearing so your odometer and mpg reads correctly.

Thanks. I think it was knowing the Speedo was already off which compounded my confusion.