Another Wheel Question...

May 16, 2006

Different versions of the Yaris have different wheel/tyre set ups.

My question is this: Are the speedo’s calibrated differently?

So if for example a T Sport is riding along a T Spirit at 60mph, will the speedo’s read the same seeing as the Spirit has (I think) 175/60/14 compared to the T Sports 185/55/15?

If I put the Spirit wheels on my car, when the speedo reads 60mph I would actually be doing 58.1mph.

The same could be said for the SR as that has a different tyre size as well.

Any thoughts?

May 16, 2006

I would pretty much assume that no matter what size of wheel/tyre is on the car, the speedo will be calibrated before it leaves the factory. The calibration will be done with whatever wheels are on each model as standard, a few of the cars will be subject to a test (quality control of some sort) to ensure that the callibration is within permissable perameters.

To answer your other point on the speedo....

If you were to take off your 185/55x15 and put on 175/65x14 (its not 175/60x14) and were driving at 70mph, the difference between the 2 sets of tyres would be -0.24% meaning your speedo would read 69.83mph as oppesed to the 70mph as it was when the 185/55x15's were on.

If you were to put 195/50x15 on instead of the 185/55x15 then the difference would be -1.45% giving a speedo reading of 68.99mph as opposed to the previous 70mph.

If you were to put 205/45x16 on instead of the 185/55x15 then the difference would be +1.1% giving a speedo reading of 70.77mph as opposed to the previous 70mph.

If you were to put 205/40x17 on instead of the 185/55x15 then the difference would be +1.93% giving a speedo reading of 71.35mph as opposed to the previous 70mph.

If you were to put 215/38x18 on instead of the 185/55x15 then the difference would be +3.97% giving a speedo reading of 72.78mph as opposed to the previous 70mph.

May 16, 2006

your speedo wont even be properly calibrated

the joy of mass production

mines out by about +6mph

May 16, 2006

My above post doesn't assume your speedo is correct.. it only goes by the readings it gives, and the figures represent what the differences would be.

May 18, 2006

When I did the 1/4 runs at brunters I was crossing the line about 80-82mph... my time slip said nothing over 76mph. So.... my speedo's out too!

May 18, 2006

Speedo's always over-read from the factory, this is to prevent any kind of lawsuits being taken against the manufacturer if someone says that there speedo wasn't reading correctly and can proove it.