I have an 89 B2 4x4 5 speed. I have a 4inch lift and run 31 10X50s. My speedo runs ~ 5mph over and my question is what kind of gas mileage am i getting?
When i do the normal calculations i get around 12-13 mpg but i know my car is traveling farther then what my odometer is reading.
Anybody know the stock size tires and how to convert the differences in distance?
If that's 5 mph over at ~60 mph, that means 65/60 or ~10%. I would guess you are going 10% farther (eg odometer says 100 miles, you've actually gone 110) than reported.
When I've dealt with this, I prefer to simply get on the freeway, count 10 mileposts (DOT's are usually good about having those accurate), and note how far the odometer says I've gone.
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'87 Bronco II XLT 4x4 & '92 Explorer XLT 4x4 & '98 Chev Suburban K1500 SLT 4x4
If that's 5 mph over at ~60 mph, that means 65/60 or ~10%. I would guess you are going 10% farther (eg odometer says 100 miles, you've actually gone 110) than reported.
When I've dealt with this, I prefer to simply get on the freeway, count 10 mileposts (DOT's are usually good about having those accurate), and note how far the odometer says I've gone.
Duh thats a good idea, count mile markers. Thx shorty!
I mount a Garmin GPS-76 to my dash as a speedometer and use that instead, though I also note the speedo differences and glue a sticker with them to the dash. 15=25 etc.
FWIW: If you have not regeared it, your speedo is way off with 31s, and not just 5 mph over.
__________________ The Year 2008 Anno Domini - May it bring a great year of Revelations to you.
You can't try to figure out milage by guessing how far everything is off just on speed alone. You changed tire size so your speed is off my a percentage, the faster you go the more inaccurate your speedo is. Most BIIs are stock with 225s which is approx. 27 inches, your door sticker will tell you what was stock on you particular BII. You changed to 31's so 31/27 is 1.13xxxx, so thats a 13% difference. So take your miles per tank by 113% (times 1.13) for your actual traveled distance, divide that by the gallons used and you will have your actual milage. You're most likely getting around 15mpg.
Matt
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88 Ranger XLT 4x4, 396W stroker, ZF 5 speed, twin stick NP 205, Perry's Fab n' Fiber fenders & bedsides and hood, 8.8 swap, BII gas tank, lifted a bit, 35in ProComp M/Ts.....4 linked Rockewells and supercharged 557 on the way
My door sticker says 225s and that's what was on it when I bought it. What I listed above is the exact same formula on the links so either will work out just fine for your calculations.
Matt
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88 Ranger XLT 4x4, 396W stroker, ZF 5 speed, twin stick NP 205, Perry's Fab n' Fiber fenders & bedsides and hood, 8.8 swap, BII gas tank, lifted a bit, 35in ProComp M/Ts.....4 linked Rockewells and supercharged 557 on the way
The first number in the tire size is the width,(225)I don't think this will change the MPG.The second number( 50,55,60,)is the percentage of the first number added to the inside diameter (15), to make up the height
I would have to see a door sticker on someone's truck for that.
My Ford data books list P205/75R15 as the only tire size ever offered.
You are correct. At some point in time one of the previous owners put a Ranger door on my BII. I noticed the vin didn't match the BII and and noticed it was a Ranger VIN.
Matt
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88 Ranger XLT 4x4, 396W stroker, ZF 5 speed, twin stick NP 205, Perry's Fab n' Fiber fenders & bedsides and hood, 8.8 swap, BII gas tank, lifted a bit, 35in ProComp M/Ts.....4 linked Rockewells and supercharged 557 on the way
You can't try to figure out milage by guessing how far everything is off just on speed alone. You changed tire size so your speed is off my a percentage, the faster you go the more inaccurate your speedo is. Most BIIs are stock with 225s which is approx. 27 inches, your door sticker will tell you what was stock on you particular BII. You changed to 31's so 31/27 is 1.13xxxx, so thats a 13% difference. So take your miles per tank by 113% (times 1.13) for your actual traveled distance, divide that by the gallons used and you will have your actual milage. You're most likely getting around 15mpg.
Matt
Thanks this is what i was looking for. 15 mpg seems to be about right. What kind of improvement in MPG would i get if i changed the gears to match the tires? Or would it just be more power?
There should be an ID tag on the cover and one on the front beam bolted on with a differential bolt. If those are missing then you can jack up a rear wheel, turn it one revolution. Count the number of times the driveshaft spins and you will have your gear ratio. You will have either 3.45, 3.55, 3.73s or 4.10. The suggested gearing for 31s is 4.10 to keep stock performace. My BII has 3.45s and 31s, runs fine but is a dog. As for purchasing gears 4wheel parts tends to have a good selection at a decent price. I highly suggest you have a pro install them for you.
Matt
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88 Ranger XLT 4x4, 396W stroker, ZF 5 speed, twin stick NP 205, Perry's Fab n' Fiber fenders & bedsides and hood, 8.8 swap, BII gas tank, lifted a bit, 35in ProComp M/Ts.....4 linked Rockewells and supercharged 557 on the way
Thanks projectnitemare, Im a decent mechanic but when it comes to gears im lost. Could i swap in a rear end from an X plorer to get higher gearing such as 4.10? I know you can get the d35 i believe and they will fit from the X's but not sure if that would fix my low gear and big tire problem....
Checked 4wheel parts and they only have the front D28 rack and pinion gear at 4.56 ratio. Does not have 4.10 gears and doesnt offer anything for the rear.
I await your help,
Thanks
Last edited by Aggie05 : 02-07-2008 at 12:38 PM.
Reason: new information
The BIIs have a different spring width for the rear axle. I ran into this problem with mine. Yes you can swap in Explorer stuff to achieve a lower gearing (stonger as well) but there are also gears offered for you current axles. The 7.5 rear had 4.10s from the factory in some appications. If you choose to have gears installed have a pro do them. I do that line of work for a living so it's nothing for me to do but not all that good for a first timer, especially without the correct tools. It probably would be cheaper to swap the D35 and the 8.8 rear from the Explorer but you will need a welder to relocate the spring mounts and you will have to shorten the front driveshaft about an inch, or swap your t-case out for the one from the explorer, should be a BW1354. The D35 beams are pretty much bolt in aside from a few steering issues because the tire rod ends are different.
Matt
__________________
88 Ranger XLT 4x4, 396W stroker, ZF 5 speed, twin stick NP 205, Perry's Fab n' Fiber fenders & bedsides and hood, 8.8 swap, BII gas tank, lifted a bit, 35in ProComp M/Ts.....4 linked Rockewells and supercharged 557 on the way
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