I recently changed my tire/wheel combination from the MINI OEM 15" wheel with Conti 175/65-15 to a Rota RB 16 x 7 wheel with a General UHP 205/50 - 16. I'm seeing a 4 mpg reduction that I attribute purely to this change having made no other changes to the car.

In my research I saw no discussion about this impact, and I'm curious what others have observed when changing tires. Is the just the tire size change or have I picked a poor mpg tire. Otherwise I'm very happy with the aesthetics and handling.

 

probably just has more to do with the revolutions per mile. when i change wheels, the more accurate my speedo gets the worst gas mileage i get.

with my 17s and overall smaller diameter, the car 'thinks' its getting many more miles per tank....thus when i put on my 16s with larger tires, the speedo is more accurate and 'thinks' im getting less miles per gallon, when in actuality it is closer to correct readings

 

Weight matters a good deal on the MC. I reduced the wheel weight by 1.2lbs but increased the tire weight by 6lbs per corner. The mileage promptly went down 3 mpg. The rolling resistance of the tire also matters.

You have increased the tire weight by 3 lbs. The diameters are 24.0 and 24.1 so the odometer should not show significant change. Weights of OEM wheels are here:
http://www.mini2.com/forum/faq.php?f...heel_tire_tech

 

I doubt it, the diameter difference between the 205/50-16 and 175/65-15 is extremely small.

 

Changes to the rolling resistance can have a huge impact on gas mileage. Besides the effect that the change in tire compound will have, going to a wider tire will definitely increase the rolling resistance, even if you used the same model tire.

When I went from the stock 175/65-15 to a 205/50-16 on my MC, I saw a decrease of about 4 MPG. Every year when I throw the stock sized snow tires on, my mileage jumps back up.

 

I may try the Yokohama AVID ENVigor next time in a smaller size (195/55-16). According to Tire Rack it helps mpg and the smaller size may help a little too.

 

The wider your tire is the less your mpg will be.

 

Bump

 

Michelin is known for it's LRR (Low Rolling Resistance) "Green X" design. Changing from OE 195/55/16 Conti runflats tonight, to 205/55/16 Michelin Primacy MXV4's....... Expect to see an MPG gain even though stepping up a size.

 

When I switched from the OEM Goodyear RFs to Yoko S.Drives, I lost about 3 mpg. After some research and discussion on the THMMC board, I decided it was mainly due to the grippier compound of a summer tire even though I had gone up slightly in size. I've now switched to some Conti DW tires, so still a summer compound. The Conti stuff claims they are LRR to help with gas mileage. Still a bit earlier, but I think I may have gained back 1 mpg with this latest switch.

 

Not a bad idea to get your alignment checked, too. If the toe is off, a wider tire will have even more resistance than a narrower tire.

 

I have 205/50/16 summer tires and I used to have 175/65/15 winter all seasons (oem conti),
now I have 195/60/15 winter snows (Michelin Pilot Alpin). My 16x7 rims
are only 15#. For summer, I used to have Bridgestone S-03 205s which were
on the heavy side and now have Dunlop SportMaxx 205s which are on
the light side of the 205/50/16 range. I'm sure the 195 snows have more
rolling resistance than the 175 Conti all seasons. Despite all these factors,
I have always seen very little change in gas mileage when I switch tires
in the late fall and early spring, and I have measured every tank since 3/03
(actual gallons per fill/actual miles driven - don't have the mileage computer
on my MINI).

+1 on checking the alignment, as Dan00Hawk said.

 

Took first trip on the Primacy MXV4s today, 300 miles over Snoqualmie to Yakima and back over Chinook Pass - Not the best roads for MPG - Great for bumps and curves. Great ride comfort - less noise - and the icing on the cake even over these roads ... 36.5 MPG! Previous trip on the Conti's to Pullman and back 33mpg.