Wheel offset question
Senior User
Joined: Jan 2002
Posts: 207
Likes: 0
From: Las Vegas
Wheel offset question
Hi all,
I have a '68 F250. I installed a '67 ford 9" rear end on it,
and I'm doing a disc brake conversion on the front using '76
f100/150 components.
I'm in the process of shopping for wheels and need to know
what offset to give the wheel people.
Is the offset a set figure for the setup I'm constructing?
Or, is it different on front axle and back axle with the different years
parts I have used?
Any help will be greatly appreciated.
Thanks.
Hawkeye
I have a '68 F250. I installed a '67 ford 9" rear end on it,
and I'm doing a disc brake conversion on the front using '76
f100/150 components.
I'm in the process of shopping for wheels and need to know
what offset to give the wheel people.
Is the offset a set figure for the setup I'm constructing?
Or, is it different on front axle and back axle with the different years
parts I have used?
Any help will be greatly appreciated.
Thanks.
Hawkeye
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
Wheel offset question
Offset is difference from backspacing ...
On most Fords it is a zero offset from the factory, 15x6, 3" backspacing. On most Fords, once you get more than 4" into the wheel well you are going to start hitting things.
As an example, how I figure things:
TE1=tire extension: tire width ((12.50)- rim width (8))/2=2.25
TE2=backspacing (with zero offset 4")+ TE1 = 6.25
Depending on the truck, you are going to hit everything from inner fenders to radius arms. With three inch backspacing TE2 comes to 5.25 and might/might not hit something.
It is more important not to hit metal to metal on full lock (say rim vs. control arm), then hitting a rubber tire against a radius arm. On my F-100 the previous owner ran 33x12.50x15 tires on 12.50 rims (4" TE2) and they did not hit anything. Now, with 31.50x10.50x15 tires on stock 15x6 rims (5.25" TE2) they do. I choose the minor rubber rubbing at full lock vs. rims too wide for the tire/truck/driving I do.
Buy the tire for your needs and get the rims to fit your needs. I would say for a F-250 with a stock 9" in back, 35x12.50x15 on 15x10 rims with 3.50" backspacing (TE2 4.75")would probably clear everything AND be easy to find.
The other thing to consider is tire/rim weight. If you decide to run anything bigger than 35s on steel rims, you will find the tire weight over 100 pounds. This is too much for most people to change their own tire without risk of injury. Aluminum rims will usually knock at least 20 pounds off a 35 inch combination.
On most Fords it is a zero offset from the factory, 15x6, 3" backspacing. On most Fords, once you get more than 4" into the wheel well you are going to start hitting things.
As an example, how I figure things:
TE1=tire extension: tire width ((12.50)- rim width (8))/2=2.25
TE2=backspacing (with zero offset 4")+ TE1 = 6.25
Depending on the truck, you are going to hit everything from inner fenders to radius arms. With three inch backspacing TE2 comes to 5.25 and might/might not hit something.
It is more important not to hit metal to metal on full lock (say rim vs. control arm), then hitting a rubber tire against a radius arm. On my F-100 the previous owner ran 33x12.50x15 tires on 12.50 rims (4" TE2) and they did not hit anything. Now, with 31.50x10.50x15 tires on stock 15x6 rims (5.25" TE2) they do. I choose the minor rubber rubbing at full lock vs. rims too wide for the tire/truck/driving I do.
Buy the tire for your needs and get the rims to fit your needs. I would say for a F-250 with a stock 9" in back, 35x12.50x15 on 15x10 rims with 3.50" backspacing (TE2 4.75")would probably clear everything AND be easy to find.
The other thing to consider is tire/rim weight. If you decide to run anything bigger than 35s on steel rims, you will find the tire weight over 100 pounds. This is too much for most people to change their own tire without risk of injury. Aluminum rims will usually knock at least 20 pounds off a 35 inch combination.
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