Moving from 16" Claytons to 18" Sportlines

[mellow yellow]

Hi

My T6.1 came with 205.65.16 claytons from factory. I've Bought some 18" sportline with 255.45.18

I want to fit these but have read these will make my speedo under read by 2% and my speedo wrong
So at 70 mph. I'll be doing 71.4 mph.

Do I need to get my van recoded/changed to the size of the sportline wheels? My plan is to use 17s for winter, but if I swap between. 17s and 18s, would that that make it worse..

I've already got speeding point.

I did search on here but couldn't find the answer. The willtheyfit says my speedo will be - 1.5% and at 60 mph, it'll be 59.1 mph

From what I've read there is a factory margin on the speedo, but when I've checked my van to GPS, mine seems to be dead on. I.e. 70mph at 70mph.

So will i be over the 70 mph limit at 70mph on the 18's?

Do I need to get it recoded?



what have you guys done when swapping from claytons to 18s or larger? Cheers

 

[DaveD]

Hi

I've searched but couldn't fund the answer.

I've a T6.1 and was fed up with the 205.65.16 claytons. Bought some 18" sportline with 255.45.18

I want to fit these this week but have read these will make my speedo under read by 2% and it'll make my speedo wrong
So at 70 mph. I'll be doing 71.4 mph.

Is that right? The sportlines are standard size tyres.

Do I need to get someone to change the software for the sportline wheels? I plan to use 17s for winter, so if I change ge back between. 17s and 18s will that make it worse..

Don't fancy a speeding ticket...I've had a few of those previously

Have any members who have also changed from 205.65.16 clayton wheels to 18s etc just left them and speedo is correct or have you had van recoded for 18s

Cheers

In my opinion, as your new tyres are an O.E size you shouldn't need to do anything regarding your speedometer, it'll be just as correct as it is now with the Claytons on.
I fitted 235/55/18 tyres on mine after having Claytons and now if I drive at an indicated 70MPH my Sat Nav, which obviously doesn't care what tyre size you're running, says 69MPH, so I know I'm fine to trust the speedometer.

 

[JumpShip]

I wouldn't be stressing over 2% .
Like above compare your speedo to GPS for an idea of what's actual reality.

 

[mellow yellow]

On the claytons, Waze GPS has me doing 70mph when speedo is 70mph...I haven't put the 18s on yet. Need a damn good clean, so I plan to do that today. Was just worried as I'm doing a trip to Kent and back next week and loads of average speed cameras and gatso's lol and don't want anymore points lol.

I'll dig out my old TomTom and compare GPS to speedo on the Devonports 1st.
Then put on the sportlines when I'm back from Kent lol

Thanks for your advice

 

[dubber36]

Just assume the speed limit is 68mph and drive to that.

 

[mellow yellow]

Thanks, I'll drive at 28mph in 30 and 68 in a 70mph, Cheers

 

[Bav]

Vehicle speedos are inherently innaccurate - IIRC, the UK legal requirement is merely that they read with 10% of true speed at 30mph and at 70mph. Add to that the EU dictat that no vehicle speedo shall underread true speed and you have a situation where, on factory-fitted wheels, you're already travelling slower than your speedo says (notwithstanding your matching GPS measurement).

So, provided you drive as if your speedo is accurate, a 2% variance isn't going to make a jot of difference... m'Lud.

 

[dubber36]

Vehicle speedos are inherently innaccurate - IIRC, the UK legal requirement is merely that they read with 10% of true speed at 30mph and at 70mph. Add to that the EU dictat that no vehicle speedo shall under overread true speed and you have a situation where, on factory-fitted wheels, you're already travelling slower than your speedo says (notwithstanding your matching GPS measurement).

So, provided you drive as if your speedo is accurate, a 2% variance isn't going to make a jot of difference... m'Lud.

 

[Bav]

Vehicle speedos are inherently innaccurate - IIRC, the UK legal requirement is merely that they read with 10% of true speed at 30mph and at 70mph. Add to that the EU dictat that NO vehicle speedo shall underread true speed and you have a situation where, on factory-fitted wheels, you're already travelling slower than your speedo says (notwithstanding your matching GPS measurement).

So, provided you drive as if your speedo is accurate, a 2% variance isn't going to make a jot of difference... m'Lud.

@dubber36 - there may have been a crucial word you missed?

Anyhoo, a speedo isn't allowed to read less than actual speed, as that could lead to inadvertent speeding.