June 7, 200718 yr '90 Legacy wagon. 185/70R14: Stock tire size. Jerky acceleration. Revs pretty high for the speed between shifts(4.11:1, 5 speed). Gas mileage kinda lame compared to my EA7/81 old school. Speedo at least 3 MPH faster than actual vehicle speed, being clocked by radar. 185/75R14: Smoother acceleration, better gas mileage and lower revs at cruising, no noticable loss of torque, and a higher range of speed in each gear. And the speedo is right on. I know the 75's are taller and narrower than the 70's. Don't know why they(Subaru) came with the 70's when 75's drive like they're the right tire size for the vehicle. The 70's were way off. What gives? Anyone else experience this?
June 7, 200718 yr im sure the stock size is 185 70 r 14 thats what my leg has also and seems to get along nicely
June 7, 200718 yr OK, I am confused. An 80 series tire is supposed to be taller than a 75 series. There is about 3% difference between the two tires. This would only be noticeable if checking the speedometer calibration, or on a long trip, where youir destination apparently moves 5-10 miles. The difference will affect your apparent fuel consumption by the same 3%, but it is not enough to change the overall final drive ratio significantly to change either the true fuel consumption or acceleration. 3% is only 100 RPM at 3000 RPM. Can you check your figures, and make sure you have the numbers right? Fuel consumption is higher than the old school cars because the Legacy is significantly larger, heavier and has a larger engine. And in 1990, it didn't have the benefit of all the refinements that have been made in the last 17 years, like variable cam timing and other engine control refinements.
June 7, 200718 yr '90 Legacy wagon.185/80R14: Stock tire size. Jerky acceleration. Revs pretty high for the speed between shifts(4.11:1, 5 speed). Gas mileage kinda lame compared to my EA7/81 old school. Speedo at least 3 MPH faster than actual vehicle speed, being clocked by radar. 185/75R14: Smoother acceleration, better gas mileage and lower revs at cruising, no noticable loss of torque, and a higher range of speed in each gear. And the speedo is right on. I know the 75's are taller and narrower than the 80's. Don't know why they(Subaru) came with the 80's when 75's drive like they're the right tire size for the vehicle. The 80's were way off. What gives? Anyone else experience this? The factory size was 185/70R14 by my owners manual. An 80 series tire is taller and bigger in diameter. Thus you will have lower revs at hwy speed the with a 75 series tire. You won't notice it on the tach though as you will be just going a little faster for any given rpm (that's why you speedo was off). I run 195/65R14 on my 1st gen Legacy wagon, same diameter as stock and a little better handling.
June 7, 200718 yr speedo's are off anyway, it's common for them to be off right off the showroom floor. tires aren't too blame for that. jerky acceleration...that may be to the tires being mismatched. were they all properly inflated? was it an equal, rotated, matching set? and even still it's possible for a tire to not be in spec, causing an unknown mismatch? these trans will act funny when the tires don't match, particularly the automatics, they will shift erratically. the manuals i'm not so sure about, i wouldn't expect as dramatic effects, but it can't help them at all.
June 8, 200718 yr Author CORRECTION: The stock tires are 185/70R14. My bad. The jerky acceleration feels like the driveline is twisting. My mom's Corolla had taller tires installed, and before that the acceleration was jerky just like my Legacy. Exact same feel. The tires were a matching set (Legacy).
June 8, 200718 yr Sounds like there was something a lot more wrong with those tires than the size! Could have been one or two really underinflated, or maybe you threw a wheel weight, and the out-of balance wheel was throwing everthing else off?
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