Speedo

**Leespe** · 10-11-2013, 05:23 PM

Is it possible to get a speedo altered to allow for bigger wheels

**tigger73** · 10-11-2013, 06:46 PM

Most people changing rim size will change tyre profile/size also to keep the rolling circumference/diameter the same (and hence no need to change the speedo).

I'm not sure it is legal to fit larger wheels/adjust the speedo. Though I believe there are some VCDS options to make adjustment to the speedo if you need to.

**Transporter** · 10-11-2013, 07:24 PM

If it's the earlier T5 then the distance impulse no. can't be changed in VCDS. Though you could experiment with modifying the VSS signal from the gearbox.

**Leespe** · 10-11-2013, 07:34 PM

Any good vw specialists in Melbourne who you could recommend or is it a dealer thing.

**Guest001** · 10-11-2013, 07:57 PM

Wheel diameter more than 25mm over largest stock size is illegal.
Check your speedo against a GPS and you will probably find its fast by up to 7kph.

Our Polo is 7kph fast at 100kph and to get it accurate would take a wheel diameter 40mm larger which apart from being illegal would overgear it so far it might not move very fast LOL

Checked this with GPS and with secret menu readings.

**Transporter** · 10-11-2013, 08:53 PM

Originally Posted by Leespe

Any good vw specialists in Melbourne who you could recommend or is it a dealer thing.

Not even dealer will be able to do it.

**Sunny43.5** · 11-11-2013, 11:40 AM

Best option is to get a GPS as suggested and do some open flat road driving then note the difference , I imported some heads up displays that give speed readings from the ECU strange thing is I get three different readings Speedo will say 104 k the GPS will show 100 k and the heads up displays 98 . Its very hard to get a totally accurate reading from any car speedo if you change tyre wheel combination then allowances for worn tyres has to factored in that's why most car speedos will give a higher than actual speed .How accurate is the speedo

**Guest001** · 11-11-2013, 11:53 AM

Originally Posted by Sunny43.5

. Its very hard to get a totally accurate reading from any car speedo if you change tyre wheel combination then allowances for worn tyres has to factored in that's why most car speedos will give a lower than actual speed .How accurate is the speedo

Speedos are required BY LAW to give a HIGHER THAN ACTUAL READING

The ADR says it can be up to 10% fast <> 4% but NOT less than actual.

Here is the ADR rule 18/03 http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf

Thought we sorted all this out in the other thread LOL