Just priced 2 new back tyres at 80 quid for the pair for the back end of my fiesta. They only have in 205/45/17 stocked at the moment though. The front end tyres are 205/40/17.

Is it safe to drive with 2 different size ratios on either end of car? Or should it be completely avoided? Thanks for any tips in advance.

I would say no, since they will be a different size circumference to the front wheels. The 40 or 45 relates to the percentage of the width of the tyre is tall in the sidewall. On rwd cars with a staggered setup, the rear tyres will use a lower sidewall rating in order to compensate for the wider tyre. But from me the answer is no. Use the same size tyres all the way round.

It's fine legally.as long as they are the same size on the same axle.

Not a prob if the slightly smaller tyre profile is fitted in the back if a front wheel drive.

Power is nothing without control .

It's fine legally.as long as they are the same size on the same axle.

Not a prob if the slightly smaller tyre profile is fitted in the back if a front wheel drive.

Power is nothing without control .

Agreed - but its probably best to stick with the same, original size tyres all round unless its for a special reason (eg, racing, off road etc)

Just go to a different tyre supplier that can give you the correct size tyres for the car

I have used different tyre profiles before like you 5 mm difference. Legally it's fine and performance wise.

Although one end of the car felt higher than the other maybe it was just knowing about it but I certainly thought I could feel a difference in hight between the front and rear, I didn't like it.

My advice is that although it's perfectly safe, legal and okay to do I would suggest sticking with the same size.

Since a tyre last a long time especially on the rear end, if you don't like it after a while it'll be a long time before you can justify the cost of getting rid of good tyres. Spend the extra couple of quid and get the right size

Also good advise.an example is look at tyre sizes front to back on Porsche.

Power is nothing without control .

The higher the sidewall, the more flex. If your rear wheels are prone to tyre flexing more than the front, it may feel a bit weird with a slightly loose rear feel. This will be more evident on bumpy corners etc.

If you compare different manufacturer tyres, even though that may all be 205/45/17 you will notice that some seem to have really big profiles compared to others. Also some tyres ore more/less rigid than others.

However, bear this in mind. If you cause a huge accident and your car is taken away for examination, the fact you purposely fitted incorrect tyres (away from the manufacturers specification for that particular vehicle) could land you in deep !Removed!.

Personally I'd stick with manufacturer spec size.

Just my 2p.