I'm running a 2014 Titanium X estate with 215/50/17 tyres but would like to go to 205/55s. Apart from a slight increase in gearing am I lilely to have any problems with this change?

If you change tyres from the Standard fitting as laid out in the car manual for the specific model and variant, you're unlikely to be insured by your insurance company.

Also, the slightly smaller 205 tyres will cause less mpg and will show a slightly higher mph reading on the average speed readout.

its 1.6% different

thats less than the drop from 8mm to 2mm tread on the standard tyre

youll actually see more mpg as the tyre has less rolling resistance

I know that there could be an insurance issue; ideally I'd go to 16" rims and the higher profile they use but can't source a set of 5 16" rims and tyres at a sensible price. I have never been keen on low-profile rubber and replaced the 60-series tyres on various other cars with 65-series to get a more comfortable ride.

 

 

1 hour ago, RedBlockFanatic said:

I know that there could be an insurance issue; ideally I'd go to 16" rims and the higher profile they use but can't source a set of 5 16" rims and tyres at a sensible price. I have never been keen on low-profile rubber and replaced the 60-series tyres on various other cars with 65-series to get a more comfortable ride.

 

 

If you do source 16" wheels it would be a good idea to check the Tyre Speed Rating for you car because if they are V rated like my Focus you might find that there are so few Tyres are made with a high speed rating in 65 series and narrow width and diameter that they are expensive, you don't have much choice and they are difficult to source quickly.

Technically if you did not tell your insurance company you have probably wrongly answered the question about modifications. I think an insurance company would be harsh if they tried to get out of a claim for this.did any model of your type of car come with those tyres? Example fiesta mk6.5 studio had 175/65/14 tyres. The style spec had 195/50/15 I think. So if I put 175/65/14 on a fiesta style it would be harsh to penalise me. But sometimes you can’t reason with insurance companies

22 hours ago, GoDiagnostics said:

its 1.6% different

thats less than the drop from 8mm to 2mm tread on the standard tyre

youll actually see more mpg as the tyre has less rolling resistance

Less mpg. More revolutions per mile with smaller tyres means more fuel usage. Less rolling resistance depends on what the smaller tyre is made from. Like for Like tyres will have the virtually the same resistance footprint or drag on the road if the tyre pressures are adjusted in the smaller tyres to compensate for the same weight load.

Don't forget all 4 will be 10mm thinner too...that's 40mm less rubber to cause friction...so more MPG there!

In the real world you won't notice any difference though!

 

It also depends on the weight of rubber in the tyres of course. If like for like, then small tyres should also weigh less. But tyres with deeper tread and thicker walls may weigh more if they are smaller. So, agree with the above. It's all about what you are measuring.

It's all academic - the car was written off after being shunted at 3mph last month!