Swapping Wheels and Tyres

**Maverick** · 19th August 2005, 17:49

For those of you who wish to change wheels and tyres on your Vectra C, the following information may be of interest.

If you change to a larger or smaller size (Not that you wish to go smaller), as long as you choose a tyre size that is fitted to a Vectra C as standard, you can get your dealer to change the speedo settings on your car with tech two. These tech 2 changes also take into account extra drag/load caused by the larger set up

Example, I am picking up my 19's next week. My standard size from Vauxhall is 225 45 18", and I am fitting 235 35 19's as Vauxhall recommend for 19" clad Vectra's and Signums.

Now the over all diameter of the 19" tyres is 13mm (1.97%) smaller than the 18's. So my car is booked into my dealer to have the 'tyre size' changed by Tech 2. This will ensure the speedo etc is correct.

Here is a list of the 'Sportier' tyre sizes.
215 x 55 x 16" 643mm (Design/SXi)
215 x 50 x 17" 647mm (SRi/Elite/GSi)
225 x 45 x 18" 660mm (Design/SRi/Elite/GSi Optional)
235 x 35 x 19" 647mm (Design/SRi/Elite/GSi Optional)

Other Popular Sizes that are non Vectra C standard fitment
225 x 45 x 17" 634mm
225 x 40 x 18" 637mm

**installer** · 19th August 2005, 19:46

thats what I said but seemed no one listened.
so back up has arrived

**Maverick** · 19th August 2005, 20:22

To be honest, although I knew the speedo is electronic, I did'nt know that speedo settings could be changed until I enquired about mine.

I thought each car was set in the factory with it's particular wheel/tyre set up. But at least we know it can be done afterwards.

**installer** · 19th August 2005, 20:32

I knew it could be done (- in my mondeo handbook it states if change wheels etc go to dealer and get it recalibrated).

**cyb** · 19th August 2005, 20:37

Matt since I changed up to 19's I have noticed no changes at all with the speed readings.

I have a gps road angel which gives a speed reading which is 2mph (approx) more than the car speedometer. Which is the same as when I had standard 17's fitted.

**Maverick** · 20th August 2005, 11:31

Originally Posted by cyb

Matt since I changed up to 19's I have noticed no changes at all with the speed readings.

I have a gps road angel which gives a speed reading which is 2mph (approx) more than the car speedometer. Which is the same as when I had standard 17's fitted.

Cyb, I think your OK, the overall diameter of the 235 35 19" and 215 50 17" is the same. So you should be OK.

The main reason I am having mine changed, apart from the diamters are different, is for insurance purposes.

My insurance know my car has the 'factory' alloy wheel upgrade for which I don't get charged extra, but I did not state which size upgrade I had.

So if the cars electronics are written with the 19" set up, as far as I am concerned this is how it was done in the factory. It is crazy that if the car is built with 18's or 19's in the factory it is classed asstandard, but if you change them later, it is classed as modified.

In reference to your speedo, mine is also 2-3mph slower than my Tom tom 500. (Well it was before I took the TOM TOM back for a refund. Bought it for Sam for our Zaf GSi, and it does not work very well as it has a heat reflective windscreen.