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tire size & gas mileage

I use my '98 taco for auto parts delivery in and around Los Angeles and have bandied this issue about with coworkers with varying opinions and explantions being the result but no definitive answer. Will I get better gas mileage with bigger than OEM tires or smaller? Replacement time is drawing near and I want to be sure I spend my money wisely. I recently bought it used and aside from the bench seat, which I've read similar complaints about in previous posts, I'm quite happy with it. Anyway, thanks in advance for any sound advice I may glean from someone in this fine group, gl

Reply to
gl753
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Changing the tire size will alter your final drive ratio. An increase in diameter will reduce the engine RPM for any given speed, and will improve your HIGHWAY mileage.

The tradeoff is that you will need to hold the tranny down a gear longer while accelerating, thus, no change or possibly a decrease due to higher engine loads when immediately starting out in 1st.

If you make a lot of trips over the passes, you will find that you will need to drop down into 4th (and 3rd) sooner to maintain speed... again, no improvement there.

Note that you need to have your speedometer recalibrated to be able to measure any of this properly. Bigger tires will cause your speedo to run slow, thus, if you change the tire size but not the speedo,

3000rpm will still be 70mph on your dash, but you'll actually be going 75 (hence, net LOSS in economy due to wind resistance). The odometer will also read "slow"... that 75 mile trip will only read 70 miles, so if you try to calculate economy you'll see a drop, when you may have actually improved.

If you do a lot of stop-and-go (sounds like you do), stick with the stock size... it's your best compromise.

--- Rich

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Reply to
Rich Lockyer

I have a 2003 Taco 4x4. I replaced the stock P225 tires with LT265 tires, a

2 inch increase in tire height.

A highway trip last weekend, I got 25mpg doing the speed limit. My speedo is off I figure by 6-7% so I may have gotten slightly better

I know this from experience...problem is I didn't have the stock tires on long enough to see the difference on the highway. On hills, many times I got to drop to 4th, and even sometimes 3rd to keep it at the limit, ie, 100kph ~

62mph.

In the city, I get 20-21mpg.

But my Taco as far as I know was designed with 265 tires in mind, it has the same gear ratio as the V6's but the 4cyl may not have all the power it needs to turn them, but I have no complaints yet.

Reply to
Brad

Other considerations beside size and inflation are the tread design and tire width. Lumpy off-road looking tread will worsen your gas mileage. Skinny, highway rib-type tires of the original diameter are probably best. If the original tire is 265/70-16, a rib tire with 245/75-16 might get better mileage.

Ken

Reply to
Ken Shelton

I should add then I have BFG All Terrains, LT 265 70R 16

Reply to
Brad

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