235/85R16 vs 255/85R16

**VladTepes** · 10th May 2011, 12:30 PM

Originally Posted by weeds

vlad will buy your 235/85/16 off you.............

I would too.

**Camper** · 14th May 2011, 02:52 PM

Would you expect a noticable difference in the spedo reading? My spedo is out ~+10k/h.

**rick130** · 14th May 2011, 03:37 PM

Originally Posted by Camper

Would you expect a noticable difference in the spedo reading? My spedo is out ~+10k/h.

255/85's pretty much correct your speedo.

Mine was 7-8km/h out @ 100km/h with 235/85-16's.
New 255/85's correct it so that the speedo would be damned near 100km/h @ 100km/h actual road speed according to the GPS I borrowed.

**Camper** · 15th May 2011, 01:13 PM

Could I also expect a reduction in the RPM at the same speed with the 255/85 oposed to the 235/85's?

**rick130** · 15th May 2011, 05:19 PM

Originally Posted by Camper

Could I also expect a reduction in the RPM at the same speed with the 255/85 oposed to the 235/85's?

If it's corrected the speedo by 8% I'd reckon so

A 255/85, depending on brand is around 33.3" in diameter, vs a 235/85 @ 31.8" or so.

On the open road the taller gearing is better IMO, but firsts a bugger, particularly when towing.

**Camper** · 16th May 2011, 06:22 PM

In what way is it a bugger? I have a clutch issue at present, going to be fixed very soon I hope!!!!!!!

**rick130** · 16th May 2011, 07:17 PM

Fitting a 255/85 is a larger diameter tyre so you've effectively raised your gearing by 8% or so.

With a Tdi when towing you either need to start in low range second gear and shift into high range when you need another gear (high second) or slip your clutch a hell of a lot more on starting.

**harro** · 17th May 2011, 06:26 AM

Originally Posted by rick130

255/85's pretty much correct your speedo.

Mine was 7-8km/h out @ 100km/h with 235/85-16's.
New 255/85's correct it so that the speedo would be damned near 100km/h @ 100km/h actual road speed according to the GPS I borrowed.

Am I reading this right?
So on my td5 02 Xtreme, the factory fitted 235/85/16 tyres give me an incorrect
speedo reading but 255/85's will make it read correctly or is this only for TDi's?

Cheers,
Paul.

**weeds** · 17th May 2011, 06:29 AM

Originally Posted by harro

Am I reading this right?
So on my td5 02 Xtreme, the factory fitted 235/85/16 tyres give me an incorrect
speedo reading but 255/85's will make it read correctly or is this only for TDi's?

Cheers,
Paul.

all speedo's are inaccurate to some degree, i think its and ARD thing. Nearly all cars i have driven with a GPS the speedo can be out as much as 5kms @100km/h

i reckon your td5 will be much the same as the tdi and nearly every other car on the road

OH..........and GO THE CATS

**harlie** · 17th May 2011, 06:44 AM

Originally Posted by Ranga

Apart from thinking I'm too bloody indecisive, what are your thoughts?

you're not alone in this respect.

255/85s are not legal. (someone should at least acknowledge it)

The speedo being inaccurate with the standard tyres is pretty normal these days, the ADRs state that a speedometer can vary by up to 10% from the cars true speed BUT it cannot read slower than the true speed. New VWs have a the ability to show ECU data on the nav screen including speed as sceen by the ECU – it’s spot on, and the instrument panel speedo is high by 6-8%.

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