If my car tyre sizes are 205/50/17 what difference will it make if i put on 205/45/17 
wife’s xmas pressie is depending on this 
You’ll scrape them on the kerb easier! 
I would expect the speedo to give an improper reading also.
There may be a marginal improvement in handling, but doubt you’ll really feel much difference.
you will save money
the 45 defines how high the tyre wall is
it would mean that acceleration and top speed would be less ,by a tiny amout as ff says and due to the tyre wall being smaaler it wouldnt bend as much under duress so it would improve the cars handling when clarkson drove it
sidewall will be smaller and your backside will make up for the size. small bumps in the road will fill bigger.
they are 64.4mm smaller in hight.
and when your speedo is reading 70 your only doing 67.75
have a look on here to see the differences
http://www.rochfordtyres.co.uk/tyrecalc.asp
mobi:
sidewall will be smaller and your backside will make up for the size. small bumps in the road will fill bigger.they are 64.4mm smaller in hight.
and when your speedo is reading 70 your only doing 67.75have a look on here to see the differences
http://www.rochfordtyres.co.uk/tyrecalc.asp
Sorry mobi - the 64.4mm is the reduction in circumference.
The sidewall will be (and therefore the car will sit) 10.5mm lower, and the circumference will be 3.3% smaller but the 67.75 mph rather than 70 is correct.
TC
sorry got the diameter and circumference mixed up.
mobi:
sorry got the diameter and circumference mixed up.
No prob - easily done 
TC
so no mileometer/speedo problems and i get them for the price of part worns
im goin to buy the wife a hoover for xmas now 
thanks all and merry christmas
Less fresh air to fill up. Don’t tell the Government though. 
Dave L:
If my car tyre sizes are 205/50/17 what difference will it make if i put on 205/45/17wife’s xmas pressie is depending on this
you cant go smaller without acceptance of cardealer and MOT.
If you have 205.50/17 in your Paper can you go two numbers bigger to 225/50/17,but check first before doing so.
the other:if you have all sorted out to go to 205/45/17 think on your Tacho
Lovlyperson:
Dave L:
If my car tyre sizes are 205/50/17 what difference will it make if i put on 205/45/17wife’s xmas pressie is depending on this
you cant go smaller without acceptance of cardealer and MOT.
If you have 205.50/17 in your Paper can you go two numbers bigger to 225/50/17,but check first before doing so.
the other:if you have all sorted out to go to 205/45/17 think on your Tacho
chaversdad:
Lovlyperson:
Dave L:
If my car tyre sizes are 205/50/17 what difference will it make if i put on 205/45/17wife’s xmas pressie is depending on this
you cant go smaller without acceptance of cardealer and MOT.
If you have 205.50/17 in your Paper can you go two numbers bigger to 225/50/17,but check first before doing so.
the other:if you have all sorted out to go to 205/45/17 think on your Tacho
What this post means, I think, that if a vehicle is type approved, the paperwork will state what size tyres are fitted and have to be replaced with. My truck has a data sheet in the document folder which tells me and the polce everything about it and its build
oh just to add u cannot have two diffrent tyre size,s on the front or rear meaning on the same axle
mezzzz1211:
the 45 defines how high the tyre wall is
it would mean that acceleration and top speed would be less ,by a tiny amout
correct, the top speed would be slightly less, but acceleration would be improved as the gearing is lowered due to smaller radius.