Seeing is believing

[Rusty's Uncle]

My wife has a Fiat Panda Cross that she has had for 6 years now. She just discovered that it had air con about a week ago but that is another story. Some months ago I saw an ad for a brand new set of Fiat 500 (new model) 8 spoke Abarth alloy wheels and tyres. I thought they would look good on the Panda , could be used as summer tyres and took a chance even though they are 16" wheels with 195 45 low profile high performance tyres. The guy selling them had a brand new car delivered then immediatly changed the wheels & tyres for Esse Esse specs.
Finaly got round to doing something this morning so loaded up the new wheels and went down to Blackboots which is just down the road as I thought they could fit the wheels then do the tracking. Told the guy what the plan was and he said that changing wheels and tyres on a car with electronically controlled 4 wheel  drive can cause problems and upset the system but the only way to find out was to fit the wheels and see. I was pretty confident as the outside diameter of the tyres was identical but the originals were 175 wide plus the hub casting was the same on new set.
Wheel fitted and everything looking good . The guy reversed the car back about 5 metres , stopped thed called me over. The digital display was scrolling through all of the thing that were now inactive and not working 
I had no idea what some of the things were but it lit up like a Christmas tree 
Much panic by me & a quick discussion. Original wheels went back on and all returned to normal 
So how the hell did that car know that the Fiat wheels that were fitted were not standard, same O/D , same hub & slightly wider, very scarey this new technology!
Reminds me that I must sort out the starter cable on my 126 but in the meantime I have a brand new set of Abarth alloy wheels & tyres up for sale 

[Hazey-n-Marc]

Sounds very odd, you sure he didn't set off the display test in the hope that you would sell him the wheels cheap? It obviously couldn't have a spare as it would be unuseable if it did that, sounds most iffy.

Marc

As you say, seeing is believing, but I have just looked this up, there are people with Panda Crosses of less than 5 years old changing wheels with no issues. It might be a load of man plums, change one yourself and see what happens.

Or just alter the tyre pressures, that will change the rolling radius and if it doesn't set off all of the warning lights then it would seem that they may have been trying to pull a fast one.

[Rusty's Uncle]

Believe me there were no tricks as I watched the whole procedure. When the car was lowered back on the garage painted floor & the guy reversed it at poodle-pace the tyres squeeled as if the 4 wheel drive was working overtime 
As for those plums , I thought mine were in danger when I thought that I had screwed up my good lady's beloved car. Also found out that the tyres fitted to the front by Quickfit some time back are not right for the car 

[grubscrew]

 I have a Landcruiser and also know that if you don t swap over the wheels (inc spare) to create an even wear on all 5 wheels, that if a new tyre is fitted the radius is critical and not to differ as it "winds up the diffs" apparantly .
 But in your case it sounds weird seeing as they were all new