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Changing tire size
mrs102
Member Posts: 1,169 ✭✭✭
Hey you car guys. What might be the effect, other than speedometer error, of going to a P255 tire when factory is P235? Both 18", 60 series.
Are speedometer calibrations a computer program now?
Comments
I have frequently done that and have had no problems. Naturally we are talk 2 wheel drive here. Check fender clearance.
Pretty much what Jeff said. It's going to change your speedo by about 8%.
If your vehicle is so equipped, most dealers that install larger/smaller tires should be able to reprogram your vehicle for the new tire size.
I went with larger 10 ply and lost a bit on the gas milage as well.
Your chains won't fit, you will have to add a couple of links on each side.
One caution to consider.....
Since with increased tire diameter, the cruising highway RPM will be somewhat reduced......and available torque, at that RPM, will possibly also be slightly reduced.
Bottom line........you MAY experience increased instances of transmission downshifting, while crossing overpasses, etc......depending on speed and incline.
My old hunting pal found out, to his dismay, what can possibly happen with increased tire diameter. In the early 2000's we were headed north out of Amarillo at the Canadian River area. I'd swear that his Ford pickups transmission cruise control tried to downshift to SECOND gear while climbing out of the river bottom area on hwy 287. Wow.......it got our attention real fast. Good times on pd trips though.👍
Hope this helps.
If I'm rememberizing correctly if you go to an aspect ratio off 55 on the new P255's instead of 60's then the tires will be within a fraction of a percent of the same diameter.
Son recently put new tires on his company vehicle(2021?) F-150 wimpwagon with the 2.7L(?) twin turbo engine. Same size but a switch to load range E to reduce gravel punctures on the roads he runs for work.
I told him mileage would be reduced. 10K miles later, he's getting 2-3 MPG less and can't hold highest gear on the slightest uphill stretch even @75 mph.
I run 'winter tires' and 'summer tires' to improve performance in my work vehicle. Winter tires are higher load range, more aggressive tread pattern, and different rim diameter but same rolling diameter. Mileage is reduced by 1-2 mpg simply due to the rougher tread creating more air drag and the heavier weight at the outer surface of the tire.
This website has all the info you need…
it has calculators for just about everything related to tire size.
🇺🇲 "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants." - Thomas Jefferson 🇺🇲
A few years ago I changed size on my old Tundra from 16 to 17 inch wheels and tires.I checked the speedometer with GPS after the change and it was right on.
Go too wide and you won't be able to turn as sharply--tire will hit the wheel well or chassis, and your three-point turn (on a forest road) will become a 10-point or worse. That got me into trouble with my 10.5's on my 4Runner designed for 7.5's a couple of years ago; put a tire over the edge and hung 'er up.