difference between 195/45/15 and 195/55/15
- Thread starter richj
- Start date
Speed change
Remember, when changing tyre profiles, your speedo will NOT account for these changes so will not show you the 'correct' speed.
If the 195/55/15 tyres were the original as fitted to your car from the factory, then if you change to 195/45/15 tyres, the speedo will then under-read by approx 6.5% - i.e. if your speedo is showing 70mph, then your real speed is actually only 65mph.
(Beware, as 'standard', your speedo can read from 0% up to 10% optimistic !)
I have a useful excel spreadsheet which shows the relative speed/size changes foir different tyres - PM me if you want it.
Cheers
Graeme
Remember, when changing tyre profiles, your speedo will NOT account for these changes so will not show you the 'correct' speed.
If the 195/55/15 tyres were the original as fitted to your car from the factory, then if you change to 195/45/15 tyres, the speedo will then under-read by approx 6.5% - i.e. if your speedo is showing 70mph, then your real speed is actually only 65mph.
(Beware, as 'standard', your speedo can read from 0% up to 10% optimistic !)
I have a useful excel spreadsheet which shows the relative speed/size changes foir different tyres - PM me if you want it.
Cheers
Graeme
Circumferences
Yes - here's the info:
Original tyre size - 195/55/15 (thats 195mm tread width, 55% tyre height of width & 15" diameter of wheel)
That makes a grand total of (((195x0.55)x2)+(15x25.4))xPi = 1870.82mm circumference.
New tyre size - 195/4/15 (thats 195mm tread width, 45% tyre height of width & 15" diameter of wheel)
That makes a grand total of (((195x0.45)x2)+(15x25.4))xPi = 1748.3mm circumference.
Difference is ~6.5% (assuming tread depth is the same)
NB - changes in tread depth can also account for a change of ~2% in a tyre's circumference
Hope this helps
Cheers
Graeme
Yes - here's the info:
Original tyre size - 195/55/15 (thats 195mm tread width, 55% tyre height of width & 15" diameter of wheel)
That makes a grand total of (((195x0.55)x2)+(15x25.4))xPi = 1870.82mm circumference.
New tyre size - 195/4/15 (thats 195mm tread width, 45% tyre height of width & 15" diameter of wheel)
That makes a grand total of (((195x0.45)x2)+(15x25.4))xPi = 1748.3mm circumference.
Difference is ~6.5% (assuming tread depth is the same)
NB - changes in tread depth can also account for a change of ~2% in a tyre's circumference
Hope this helps
Cheers
Graeme
cool stuff
I upped my wheel from a stock 13 to 14 inch but used a 195x50R14 in stead of the stock tyre ....awesome gearing difference......My speedo now READS 10% high...(so it reads 33mph when the car is really doing 30mph...etc)
when I eventually put 195x50R13 tyres on the stock trailers (rear) rims....I stopped sliding on every corner tooo... and since this squatted the back lower than the front...stopping distances dropped too
plus the -35mm suspension: GO_KART
...shame about the recent MOT failure on sills corrosion..LOL
I upped my wheel from a stock 13 to 14 inch but used a 195x50R14 in stead of the stock tyre ....awesome gearing difference......My speedo now READS 10% high...(so it reads 33mph when the car is really doing 30mph...etc)
when I eventually put 195x50R13 tyres on the stock trailers (rear) rims....I stopped sliding on every corner tooo... and since this squatted the back lower than the front...stopping distances dropped too
plus the -35mm suspension: GO_KART
...shame about the recent MOT failure on sills corrosion..LOL
