Hi All
I have just had new tyres put in
245 17†40 at the rear and 225 17†45 front
When I got home I noticed that the front ones where 45 and seemed a touch higher / bigger
I called the tyre fitter and he said that my old font ones were also 45 and any way it was ok to have them different
What does the 45 stands for and is it OK to drive like this?
Regards,
Michaelb
245is the width 17"wheel diameter 45 profile tyre hight http://www.tyresave.co.uk/tyresize.html heres a handy link
The fronts are 6mm bigger overall with approximately 3mm difference in tyre wall height. Nothing to worry about. The rears have more rubber on the road for greater grip and improved power delivery.
The 40 and 45 is the percentage of the large number (the tyre width - 225 and 245) that is in the side wall of the tyre.
Jon
The profile is the sidewall height a a percentage of the width. Soon a 225.45 the sidewall is 45% of 245 high. 255\'s are wider, so to keep the same rolling radius, you need a lower profile :)
HTH
Si
Or what johnny said (I used that link too, lol) link should be: http://www.tyresave.co.uk/tyresize.html
Quote from: J_T;593881Or what johnny said (I used that link too, lol) link should be: http://www.tyresave.co.uk/tyresize.html (http://www.tyresave.co.uk/tyresize.html)[/URL]
i kept looking and i couldent see wat i did wrong lol but i got it,thanks:Thumbsup!
Chaps
Many thanks for your informative replies
I actually see the front tyres as being bigger
Honestly, the front tyres look bigger then rear ones when looking at the car from the side
The question is do I change the back ones to 45 or front ones to 40
What would give me better handling? What is the “done thing! For an fd with 245 at the rear and 225 at the front?
Regards,
Michaelb
It would depend on how much flex you want in the tyre. The tyre is the last part of the suspension, the less give in the sidewall the firmer the ride etc...
Quote from: michaelb;593944Chaps
Many thanks for your informative replies
I actually see the front tyres as being bigger
Honestly, the front tyres look bigger then rear ones when looking at the car from the side
The question is do I change the back ones to 45 or front ones to 40
What would give me better handling? What is the “done thing! For an fd with 245 at the rear and 225 at the front?
Regards,
Michaelb
I have 245/35/17 on the rear of mine and 225/40/17 on the front,its all about rolling circumference,stick with what you have got,if you went to a reputable tyre place,i am sure they would have looked it up,cheers
Yup as others have said, the 40/45 is a percentage.
I have 235/40/18 front and 265/35/18 rear.
I always thought the lower profile figure (percentage) should be on the rear so as to equalise the difference in tyre width\'s
Ill try to explain what i mean
Take michael\'s tyres
F 225/40 R 245/45
So 225 x 40 / 100 = 90
and 245 x 45 / 100 = 110.25
The a difference of 20.25
But take the higher profile on the rear and do the percentage again
F 225 x 45 / 100 = 101.25
R 245 x 40 /100 = 98
Only give a difference of 3.25 Thus equalising the pressure beween the 4 much more evenly
Happy to be corrected though if im talking out of my dish
neiljdmr - The only thing you\'re working out there is the height of the sidewall. It\'s the circumference of the tyre that matters.
michaelb - Use the link above to work out how close to the oem tyre circumference your new ones are. Too far out and it\'ll affect your speedo reading. From memory, originals are either 225/50 16 all round or R 255/40 17 and F 235/45 17 (both of wich are very close in circumference to the original 16"s).
Steve
Steve
Quote from: Brett;593945It would depend on how much flex you want in the tyre. The tyre is the last part of the suspension, the less give in the sidewall the firmer the ride etc...
I have my tain set up on almost the hardest setting as I like a firm ride so on that note which set up would give me the most firm ride?
Which tyre combinantion?
Regards,
Michaelb
Quote from: neil_jdmr;593968I always thought the lower profile figure (percentage) should be on the rear so as to equalise the difference in tyre width\'s
Ill try to explain what i mean
Take michael\'s tyres
F 225/40 R 245/45
So 225 x 40 / 100 = 90
and 245 x 45 / 100 = 110.25
The a difference of 20.25
But take the higher profile on the rear and do the percentage again
F 225 x 45 / 100 = 101.25
R 245 x 40 /100 = 98
Only give a difference of 3.25 Thus equalising the pressure beween the 4 much more evenly
Happy to be corrected though if im talking out of my dish
Thanks for all the figures so the more even spread across all fours the better the handling? So I should really have them all at 40, right? or am I missing a point here and it does not really matter?
Regards,
Michaelb
Quote from: efiniste;593980neiljdmr - The only thing you\'re working out there is the height of the sidewall. It\'s the circumference of the tyre that matters.
michaelb - Use the link above to work out how close to the oem tyre circumference your new ones are. Too far out and it\'ll affect your speedo reading. From memory, originals are either 225/50 16 all round or R 255/40 17 and F 235/45 17 (both of wich are very close in circumference to the original 16"s).
Steve
Steve
My radar detector is already telling me that my speedo is showing more sspeed than I am doing and that was before the change ...
Regards,
Michaelb
Quote from: probedb;593962Yup as others have said, the 40/45 is a percentage.
I have 235/40/18 front and 265/35/18 rear.
Mate, I am still a bit lost with it, persantage of what? What is on the road and the height of the tyre?
Regards,
Michaelb
Quote from: michaelb;593991My radar detector is already telling me that my speedo is showing more sspeed than I am doing and that was before the change ...
Regards,
Michaelb
Unless you are Lewis Hamilton in disguise you\'ll find that happens with every car you drive.
Tyre numbering is as follows:
245/40 17
245: width of the tread in millimetres
40: sidewall height as a percentage of tread width
17: wheel size
The lower the middle number, the harsher the ride and the quicker it will break away when cornering (less tyre sidewall to flex).
Your current setup is 10mm narrower in tread, front and rear, than a standard FD on factory 17" wheels.
Your sidewalls are 4mm smaller at the rear and 4.5mm smaller at the front than a standard FD on factory 17" wheels.
Personally, I wouldn\'t worry about it.