Quote:
Originally Posted by mwebb
did you calculate in a fudge factor to allow for the difference in OD when making the FE comparison between the
155x80x13 versus 195x50x15 tire wheel combination ?
are you thinking the change in 1/4 mile times are a direct result of
increased mass of the wheel tire assembly
or
increased aero drag of the wider tires / wheels
or
change in final drive ratio due to larger OD of the 15" wheel / tire ?
i have the same car and of yet un installed 15" alloy acura legend wheels with 195 60 15 tires
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The 155x80x13s were 22.8" in dia while the 195x50x15s are 22.7, a difference of only .2%....and even though tiny I correct the miles per tank to reflect the shorter tires...for example every 100 miles traveled is really 99.8.
The 1/4 ets are slower due to the extra wt of the tire/rim combo...not aero drag because the car aero was cleaned up better with a grill block and headlight covers. The new aero mods made the top speed on the hiway rise from 81 to 87 mph! The slower ets were not caused by the difference in tire diameer because the 15s are a bit smaller and should have helped a quicker et.
As for putting 195x60x15s on your car you might run into clearance troubles. That size is 24.2" in diameter, and if your speedo says 60 you will be really doing 63.8 or a error of 6.3%. If I am on a undulating country road I can hear my LR tire barely scrape the fenderwell...your problem will be MUCH worse due to the much larger dia of those 60 series tires. If you think you'll get better mpg because of the larger dia you will also need to figure in that the 195x50x15 tires are about 5 lbs heavier each than the stock 13s.
Here's a link to what my stuff looks like, and the cars I race against:
Even the 3 cylinder Geo gets action
UMTR Nationals at Edgewater - 9/26/09 - Hyper-Performance Motorsports Inc. Photography
The White Gnat strikes again
UMTR Nationals at Edgewater - 9/26/09 - Hyper-Performance Motorsports Inc. Photography