Tire size difference - spare tire

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Old 06-11-07, 10:49 AM
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Tire size difference - spare tire

97 Ford 150 6 cyl 2WD
The tires on the used-bought pickup are LT 235-85-16. Spare is LT 245-75-16, smaller in diameter by 4.1%. In terms of revolutions/mile, 636 vs. 662. In case of flat tire, can I drive 20-30 miles back home with the spare? Does it make any difference whether the spare goes on rear or front? Thanks.
 
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Old 06-11-07, 10:59 AM
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shouldnt be a problem to drive on it but would only use it for a spare tire only.
it doesnt matter wether it goes on front or rear.
 
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Old 06-11-07, 11:21 AM
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It's good to know I can keep the spare. Yes, I will use it only for spare. By the way, how do 2 tires of different sizes run on the same axle? I have always wanted to know. Thanks.
 
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Old 06-11-07, 11:34 AM
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The wheel has the same bolt pattern as the studs on the vehicle.
 
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Old 06-11-07, 01:34 PM
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the axle isnt locked there for one can turn more rpm than the other this is true for most stock vehicles even front wheel drives unless a performance locker differential is used that actually locks the axles together, even most positrac differentials can allow some slipage and allow one axle to turn at a different speed. many vehicles do not have a full size spare to begin with.
 
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Old 06-11-07, 04:15 PM
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spare tire

then again on a 4x4 truck or car you have to use the same size tire for all wheels at all times, to prevent damage to the transfer case, that's why you see a full size spare tire on most trucks ( 4x4 at least ) .
also, dont ever do a rear wheels dyno test on a 4x4 vehicle unless dyno is equipped for all wheel drive vehicles.
 
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Old 06-11-07, 05:46 PM
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Lou,

Why is that? If the vehicle is full time 4x4 or AWD, I understand, but with 4 wheel drive off, just the rears are applying the power.


"also, dont ever do a rear wheels dyno test on a 4x4 vehicle unless dyno is equipped for all wheel drive vehicles."
 
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Old 06-11-07, 07:39 PM
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Yes even though AWD or 4x4 may not be engaged , I know a couple people who have ruined their transfer case because of a diff. size tire used on their vehicle. One was a Toyota Tacoma the other one I dont remember.
Google it and see. As for the dyno testing some 4x4 ( my suburban does ) have a warning against using one not equipped for 4x4 vehicles,something to do with transfer case being automatic.
 

Last edited by LouBazooka; 06-11-07 at 07:41 PM. Reason: added more info
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Old 06-11-07, 07:43 PM
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I understand the tire size issue with respect to 4x4, but my question was about the dyno.

I've seen trucks, SUV's, etc with selectable 4x4 dyno'd many times on a stand dyno. If the vehicle is in 2 wheel drive, the xfer case is not supplying any power to the fronts.

+++ Locking thread. Getting off topic now+++
 
 

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