Hypermile 1992 4Runner - Page 2 - Fuelly Forums

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Old 05-16-2008, 07:15 AM   #11
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I only tow a utility trailer for dirt, helping friends, and lumber. Towing or off-roading is NOT an issue. The truck doesn't have a lift and isn't all that high now; I can't see how lowering would affect much. It'll always be in the air, now my wife's Corolla I could take to ground easily but to do that on mine would take a LOT of work.

The mirrors are already small but in Missouri you only need a driver's side to stay legal.

The only things I'm worried about on high psi tires is blowouts, cupping and braking. The rest I can handle and IF we get a huge snow storm I can always deflate for a couple days.
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Old 05-16-2008, 07:24 AM   #12
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I still think I need to go a little smaller on tires. The highway rpm is on the high side BUT the low suck for power. I have to give it quite a bit of gas for it to get going from a stop. Toyota offered the 4runner with 2 different size tires that year. Mine calls for the smaller 225/75/r15 and right now it has on the larger 31" wide profile off-road tire. Is there a similar diameter tire that is more narrow like a 215/85/r15? I don't know and I can't fine an online tire diameter chart.
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Old 05-16-2008, 07:31 AM   #13
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I love this thing. It's loaded and it's so old it has an ash tray but it doesn't have cup holders or automatic lights. A trip back in time. Last night I looked at the inner door panel for OEM tire size and it called for only 26psi, I'm guessing for a smooth ride, obviously built before everyone freaked out about gas prices.
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Old 05-16-2008, 08:43 AM   #14
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I've run tires inflated to their sidewall-stamped maximum for wear, fuel economy, and handling purposes on various vehicles for probably 300,000 to 400,000 miles and they have been much more blowout resistant. Blowouts on modern automotive tubeless radials happen mainly for two reasons: Low pressure that causes high temperatures, or impact with a sharp edge that crushes the tire against the rim. Higher pressure protects against both of those blowout causes.

I've never experienced cupping. In fact, since I begin inflating to the tire's rated maximum, I've had perfectly even wear, which I never achieved before. Theoretically it can cause center wear but that consequence has not materialized for me.

At low RPM, a heavy foot is good, believe it or not. A light foot = a nearly closed throttle, which wastes a lot of energy as the engine sucks air through it. Low RPM + heavy foot really helps, so I wouldn't worry too much about the current tire size being too large as long as it's not tough on you or your clutch.

http://www.miata.net/garage/tirecalc.html is the standard tire size calculator. Check it out and be sure to calculate your speedometer/odometer error in to your fuel economy calculations, considering that your tires are not stock size. It says your speedometer (and therefore your odometer too) reads 8.6% too slow.

26psi is terrible for that. It's the minimum safe pressure to keep your tires from blowing out when they're brand new and not the defective Firestones that came on Ford Explorers. There's no way I'd ever run 26psi with any tires on that vehicle.
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Old 05-16-2008, 09:05 AM   #15
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Take a look at this thread, someone found some possibly good tires for you...
http://www.gassavers.org/showthread.php?t=7430
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Old 05-16-2008, 09:12 AM   #16
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Quote:
Originally Posted by theholycow View Post
Good FE generally involves low RPM

i disagree. good FE = a lightweight right foot.

open a factory honda .bin in a rom editor or a cavalier map in hptuner. the injector pulse duration is nearly the same at cruising vacuum levels from 2-5k rpm. granted, every engine will be different... but the difference in FE is minimal. the problem is really aero and wind resistance. FE reduces exponentially with speed.

i have very short gearing on my GSR and get great mileage spinning at 4200 rpm at 72mph.
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Old 05-16-2008, 03:30 PM   #17
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There have been good reports by people that have put front air dams on larger vehicles..

http://www.gassavers.org/showthread....light=f350+dam

It seems that a boattail works well on square backed vehicles.. Perhaps a plug in unit that goes into a trailer hitch receiver?
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Old 05-23-2008, 08:01 PM   #18
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I've got a 97 4runner 4cyl... different year and different motor but a lot still applies and I've worked on your generation 4runner.

If you don't need to carry the spare, don't. Throw in a bottle of fix-a-flat and remove the spare (it weighs a LOT), then fill the gap with colorplast or sheet aluminum, without the spare there is a huge hole back there that really eats up air at speed.

Check what your truck originally came with as far as tire size goes, yes Toyota did offer the 4runners in 2 tire sizes, but the transmissions and rear ends are geared differently between models.

FYI, that generation 4runner has always been known to be sluggish from a start, so it may not be your tire size.

The underside is pretty dirty on these, cleaning it up with an underbody pan or a front air dam will help.
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