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Old 06-15-2011, 09:49 AM
sixshooter sixshooter is offline
Ford Truck Driver
 
Join Date: Oct 2010
Posts: 75
Default Bigger-than-stock tires - no power in 5th gear... gear ratio?

more details in my sig. I have put on 225/75-15 (28") tires instead of the stock 225/70-14 (26"). What is happening is at highway speed I'm having to keep my gas pedal pegged on the floorboards to maintain 70 mph. Passing is a joke, I always have to downshift, sometimes to 3rd just to get the revs high enough to pass, even at 60 mph. I got it into the 90s once going downhill (I don't always drive that fast, either, I was trying to catch up to someone on a road trip).

Here's the issue: I can only imagine that this lack of oomph (to use a technical term) is caused by the larger tires throwing off the gear ratio that the engine is designed to work with. I can also imagine that this is having a negative effect on my gas mileage AND is causing my engine and transmission undue stress.

Here's the problem: I'm going to school in the fall, and I'll be commuting twice a week (to school on Monday, home on Friday) and I'm concerned about my truck. It's going to be a lot of miles over the next 2 years.

Is it possible that 2" in overall tire height is really killing it on the highway? Around town it's fine, from a red light it'll squeal the tires and I'm always the first through an intersection, so it's not like I'm having engine trouble.

Any ideas or suggestions?

PS: should this have gone in "Wheels and Tires" or "Drivetrain Tech"?
__________________
1995 2.3L 2WD 5 speed 201k (10/10/15) no A/C
{extra leaf springs, the rattiest set of AR Outlaw IIs you've ever seen, aftermarket lead foot, stock rust and other broken parts}
180k (5/17/13)

Last edited by sixshooter; 06-15-2011 at 10:08 AM. Reason: wrong sub-forum?
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