I've just bought some genuine Fiat alloys (at a great price) for my Fiat Stilo 1.2 16v Active, and I am looking to replace my current iron wheels. My iron wheels are 195/65R15, and the new wheels are 205/55R16. I have a few questions:

Do I need to buy spacers?
Will my speedometer read incorrectly now I've increased wheel size?
Do I need to know/buy anything else before I fit the alloys?

Thanks everyone.

You have increased the alloy size. Not so much the wheels itself Im pretty sure thats goin 2 be the same size wheel uv jus got more alloy less tyre. They shud fit straight onif they have come off another gp

Meant stilo not gp lol

Great, thanks. So even though these wheels are 205mm wide instead of 195mm they will be fine?

They shud b yes. its only a centimetre difference n u shud have alredy alot more clearance then a cm

Your question on speedo difference i can ansewer from the info you gave. I have checked on a few online tyre differecnce calculators and most of them returned a circumfrence difference of just -0.41% or -0.81cm.

So 30mph will show as 30.12mph
and 60mph will show as 60.25mph

www.wheelcalc.com
http://www.willtheyfit.com

To answer the question on spacers, we would need to know the offset (measured in mm) and rim width (measured in j ie 6j). What your looking at buying will probably be fine but you could end up with the wheels looking sunken in or stuck or even rubbing out if the difference is too big.

Here is a diagram explaining offset. Its the wheels mounting face distance from the centre line of the wheel.



You also need to check if your wheelbots will have the correct ammount of thread sticking out from the wheel and if the bolt head is the right shape (taper) to seat in the bolt holes. Hopefully the stilo guys can give you a better answer on this. If you have too much bolt sticking out it could smash the bits inside your hubs to bits. Too short and your wheels fall off. One simple and definate way to check, take your steel wheel off put a bolt through the wheels hole and measure how much thread sticks out. Put the same bolt through your alloy wheel and measure how much sticks out the back again.

The other important things to consider are PCD Pitch Circle Diameter;


and centre bore.

Thanks Adrian. I'll check the bolts as soon as I can.

The PCD looks interesting, I didn't know about that. As tthe new wheels are genuine Fiat Stilo alloys I hope that there is no difference between the two diameters, however it is another thing that I was check to be sure. Thanks again

Adrian Bravo said:

So 30mph will show as 30.12mph
and 60mph will show as 60.25mph

Click to expand...

So it'll be a tiny fraction more optimistic (indicates a higher speed than actual) than it is now (legally, speedos must be optimistic).

Terrific post, Adrian.