10-14-2011, 02:54 PM
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#1
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Tires and Speedo
My 94 came OE with 225/75 r15's, but i have since gone up to 31 x 10.5 r15. My question is this, how is my speedo on the money with no modifications? I have checked it with GPS as well as those "your speed is" things.
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1994 4runner sr5 v6 stock with 227,000 miles, 31'' ProComps, New Rear Coils, 8000k 55w HID's. Aquired from father in law who bought it new in '95.
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10-14-2011, 03:03 PM
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#2
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I love this thing
With 31x10.5's, your axle gear ratio is now like having 3.74 gears instead of 4.10 gears.
At 50 mph, you're really going about 55 mph.
Every 100 miles driven by odometer is really about 109 miles.
Last edited by SUBTEGRAL; 10-15-2011 at 05:17 PM.
Reason: clarification
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10-14-2011, 03:03 PM
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#3
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Quote:
Originally Posted by SUBTEGRAL
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You still have 4.10s. Its impossible to change that by changing tire size. I think what you mean is it will FEEL like 3.74s, die to the fact that the engine isnt in its proper power band anymore.
Its possible 31s are stock on your truck. Or someone has swapped gears previously. Your stock gear code and tire size should be listed on the tag in the drivers door.
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Last edited by Hyde802; 10-14-2011 at 03:07 PM.
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10-14-2011, 03:10 PM
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#4
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Yeah, that's what I meant - I didn't mean a physical gear ratio change.
His 4Runner is the same year as mine.
Toyota specs say 4.10 with P225/75/R15's
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10-14-2011, 06:30 PM
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#5
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I also have 31's on my rig. So, aside from doing a little mental math while I am driving, is there any somewhat simple and cheap way to get the speedo and odometer to be accurate?
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10-14-2011, 09:16 PM
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#6
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Go back to stock tires or re-gear.
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10-14-2011, 09:48 PM
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#7
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Quote:
Originally Posted by Vegas4Runner
I also have 31's on my rig. So, aside from doing a little mental math while I am driving, is there any somewhat simple and cheap way to get the speedo and odometer to be accurate?
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I didn't do the research, but i believe you can change the speedo gears in the T-case to compensate for bigger tires. Well at least on most T-cases. I think stock to 31's is too small of difference to deal with though. I say just leave it until you get into bigger tires, say 35's then regear the axles to compensate and get power back.
Thank you Hyde, for yet again clearing up non-sense.
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10-14-2011, 10:01 PM
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#8
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It wasn't non-sense, I didn't mean he physically had lower gears because of larger tires.
Hyde knew what I meant, he was just clarifying.
As far as the difference between stocks (28x8.86) and 31x10.5's not being a big deal, according to the math, it is. ... especially when figuring your gas mileage.
I explained the exact difference.
Check the calculator link I provided if you don't believe me.
From calculator link: As far as gearing goes, if you have a 4.10 rear-end and 225/75 R 15 tires (28 x 8.86 x 15), changing to 267/76 R 15's (31 x 10.51 x 15's) would be the same as if you kept your stock wheels and tires but changed your rear-end gears down to 3.74's
Last edited by SUBTEGRAL; 10-14-2011 at 10:41 PM.
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10-14-2011, 10:31 PM
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#9
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What confuses me is that the door sticker shows the OE 225/75r15 and i know for a fact that nothing has been done to correct this in the transfer case. According to my GPS as well as the radar things on the road, my speedometer is dead on at all sppeds. Everything about my truck indicates that it had the 225/75r15's from the factory in Japan...door sticker and smaller gas tank.
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1994 4runner sr5 v6 stock with 227,000 miles, 31'' ProComps, New Rear Coils, 8000k 55w HID's. Aquired from father in law who bought it new in '95.
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10-14-2011, 10:43 PM
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#10
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OK so your speedo is dead on... what's the problem? The fact that your door sticker say's the factory tire size?
If your speedometer is dead on with 31's then great! No mental speedo math. Enjoy the rest of your driving days being sane. Who cares what a sticker says, unless its radioactive, explosive, etc.
Heck come drive mine, maybe your magic is strong enough to correct my speedo for 40's.
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10-15-2011, 12:02 AM
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#11
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Quote:
Originally Posted by buzzie0013
According to my GPS as well as the radar things on the road, my speedometer is dead on at all speeds.
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Maybe a previous owner upgraded your differential gears..
That would explain not having any speedometer/odometer discrepancy..
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10-15-2011, 01:03 AM
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#12
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I guess I answered my own question before I posted... I realize that everything is dead on with my truck, but theoretically, with no modifications, the speedo should be off.
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1994 4runner sr5 v6 stock with 227,000 miles, 31'' ProComps, New Rear Coils, 8000k 55w HID's. Aquired from father in law who bought it new in '95.
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10-15-2011, 01:33 AM
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#13
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are the 31s brand new? i know my almost bald 31s are more like 28 lol
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10-15-2011, 10:09 AM
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#14
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One question I noticed didn't get answered...IS there a way to corect the spedo through an adapter, gears, whatever? I've noticed mine is about 5 off...I know it's just mental math and not that big of deal, just an annoyance. Given there are speed sensors and all kinds of other BS associated with the computer, what do you change (other than rear gears) and not screw other things up? Is there some magical box to plug in to solve tire/speedo issues?
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10-15-2011, 04:33 PM
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#15
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Quote:
Originally Posted by csrobb007
I've noticed mine is about 5 off...
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You must mean when traveling at least 50 mph?
I have to be going at least 50 mph to be 5 mph off.
At 30 mph, I'm only about 2 or 3 mph off.. and so on and so forth.
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