Boxguy
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• San, TX, USA |
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• Registered on 1/11/2005 |
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• 9 posts |
• 1
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 Posted:1/16/2005 20:10 |
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Just put new tires on my X (305 x 55 x20). What effect has this had on my speedometer?
Also does anyone have any idea on how much of a lift I am going to need to put on to get rid of the rubbing on sharp turns.
Great site you have going here, glad I found you guys! |
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CHPMustang
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• Plano, TX, USA |
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• Registered on 7/24/2002 |
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• 1,800 posts |
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 Posted:1/16/2005 22:48 |
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Hi Rob Welcome to the site 
If your tire height deviated from the 265's you may or maynot need a recal,I went to 285's and didn't need it,I think it'll personal preference mostly.
The tire clearance question I don't ahve the answer for,one of the guys here in Richardson did a 6" has somewhat of a rub when in the turns.
Are you over there in the Windmill community?
Bill
Bill
2002 Excursion XLT-P 4x4 7.3L Powerstroke Diesel
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Boxguy
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• San, TX, USA |
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• Registered on 1/11/2005 |
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• 9 posts |
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Posted:1/17/2005 06:21 |
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No we are on the south side of town in Winner's Circle.
Thanks for the info. |
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LANDYOT
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• Subscriber since 11/23/2003 |
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• Newport News, VA, USA |
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• Registered on 7/15/2003 |
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• 1,110 posts |
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Posted:1/17/2005 07:54 |
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The "calculated" tire diameters are as follow:
... 265-75R-16 = 31.7" dia.
... 305-70R-16 = 32.8" dia.
... 305-55R-20 = 33.2" dia.
I have the 305-70R-16s on mine, and the speedometer is now dead on ... at least in accordance with those mobile "This is your speed" radar trailers the police set out from time to time. Typically, OEM tires produce speedo readings a little on the high side. 33.2" diameter? You're speedometer is probably reading about 1 or 2 percent slower than you're actually travelling .... if your speedo says 50MPH, you're doing maybe 51.
Oops! Almost forgot. WELCOME to the forum! |
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J-Douglas
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• San Antonio, TX, USA |
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• Registered on 3/18/2004 |
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• 89 posts |
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Posted:1/17/2005 14:28 |
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Good info guys...... I have found a GREAT source for calculating speedometer descrepencies.
Go to www.tires.com (discount tire's website). On there, you'll see a tab called "Info Center". Then, click on "Tire Dimensions made simple"
There, you can input your original tire, and the new tire, and it will calculate all sorts of figures (including actual speedometer and indicated speedometer ratings).
Its great! Check it out.
Just remember..... along with your speedometer being off, your odometer, your tripmeter, and your onboard computer will be off.
I just installed 37's, and this is what I did: I found the circumference of the old tire and new tire, and found that they were about 18% difference. SO, everytime I figure out my mileage, my odometer, or my speed. I take the indicated figure and multiply by 1.18 (or, add 18%) for the actual figure.
Good luck!
5.5" Fabtech, 37x12.5x17 BFG AllTerrains, 17x9 Helo Maxx 8 Chrome. 6.0 Powerstroke Diesel. |
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Boxguy
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• San, TX, USA |
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• Registered on 1/11/2005 |
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• 9 posts |
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Posted:1/18/2005 15:41 |
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Thanks for all the info ! |
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David Feldner
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• Morgan's Point Resort, TX, USA |
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• Registered on 4/19/2002 |
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• 11 posts |
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Brian Barnett
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• San Antonio, TX, USA |
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• Registered on 9/6/2004 |
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• 103 posts |
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Posted:1/20/2005 19:06 |
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I heard that if you put bigger tires on and then change the gears in the diff you can get the power back and the speedo will get back to normal.. is this true???
It really is all about size!!!!!! |
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