Wheel bolt pattern questions on 81 F100
#1
01-30-2016, 05:22 PM
Wheel bolt pattern questions on 81 F100
Ok I have seen it posted that there are 2 different size wheel bolt patterns 5x4.5 and 5x5 if I have it right.
What dictates what size wheel goes on what truck?
I ask because I have 2-81 F100’s both 4x2’s both with 300’s, both have manual tranys 1-T18 other-Srod, 1 a SWB flare side (t18) custom the other a LWB style side (Srod) ranger. The ranger has the small pattern the custom the large pattern.
Now the real questions, are the spindles/caliper brackets the same between the two? I need to have the larger pattern to match the rear but I need to use the beams & spindles of the small front suspension because the kingpins on the large are frozen and have a lot of play in them.The plan was (and has been done) to undo the beam bolts/strut rods/springs @frame/shocks/brake line on both and swap the parts between the two but now???
The plan now is if the spindle/caliper brackets are the same is to swap the large pattern rotors over to the good spindle/caliper/beams
And this comes after I spent time cleaning and painting the parts only to find the wheel bolt pattern difference .
Thanks for any help you can give.
Dave ----
What dictates what size wheel goes on what truck?
I ask because I have 2-81 F100’s both 4x2’s both with 300’s, both have manual tranys 1-T18 other-Srod, 1 a SWB flare side (t18) custom the other a LWB style side (Srod) ranger. The ranger has the small pattern the custom the large pattern.
Now the real questions, are the spindles/caliper brackets the same between the two? I need to have the larger pattern to match the rear but I need to use the beams & spindles of the small front suspension because the kingpins on the large are frozen and have a lot of play in them.The plan was (and has been done) to undo the beam bolts/strut rods/springs @frame/shocks/brake line on both and swap the parts between the two but now???
The plan now is if the spindle/caliper brackets are the same is to swap the large pattern rotors over to the good spindle/caliper/beams
And this comes after I spent time cleaning and painting the parts only to find the wheel bolt pattern difference .
Thanks for any help you can give.
Dave ----
#2
01-30-2016, 06:37 PM
I had to look this up as it's one of those things I refuse to dedicate brain cells remembering but I believe the following is correct:
It went by GVWR as well.
Here is a simple chart, and is the general rule...
1980-1983: F-100: GVWR: 4700/5000: with Power Brakes: 10inch brakes: 5x4.5
1980-1983: F-100: GVWR: 5150 and 4700/5000 with manual brakes.: 11 inch brakes: 5x5.5
1980-1986: F-150 and U-150: 11 inch brakes: 5x5.5
Source: Ford light truck service specs manual: FPS-365-322-81
Here is a simple chart, and is the general rule...
1980-1983: F-100: GVWR: 4700/5000: with Power Brakes: 10inch brakes: 5x4.5
1980-1983: F-100: GVWR: 5150 and 4700/5000 with manual brakes.: 11 inch brakes: 5x5.5
1980-1986: F-150 and U-150: 11 inch brakes: 5x5.5
Source: Ford light truck service specs manual: FPS-365-322-81
#4
01-30-2016, 07:12 PM
Small pattern has power brakes and guess the small drums?
Large pattern has manual brakes and guess the large drums?
So both are 4700 GVWR so it must be the power/non-power& drum brake size.
I also just saw the smaller pattern has 15x6 wheels and the large pattern 15x5.5 wheels, strange.
So does anyone know if I can swap the rotors between the spindles?
Anyone have a parts book/CD to see if the spindles are the same? I cant look up bearings as they will be different (I am sure) because the large pattern looks like it has larger bearings just looking at the two.
Maybe I can look up the seals but would not tell me if the ID of the bearings are the same and more so if the distance between inner & outer bearing races of the two spindles are the same.
Dave ----
Large pattern has manual brakes and guess the large drums?
So both are 4700 GVWR so it must be the power/non-power& drum brake size.
I also just saw the smaller pattern has 15x6 wheels and the large pattern 15x5.5 wheels, strange.
So does anyone know if I can swap the rotors between the spindles?
Anyone have a parts book/CD to see if the spindles are the same? I cant look up bearings as they will be different (I am sure) because the large pattern looks like it has larger bearings just looking at the two.
Maybe I can look up the seals but would not tell me if the ID of the bearings are the same and more so if the distance between inner & outer bearing races of the two spindles are the same.
Dave ----
#5
01-30-2016, 07:32 PM
I just looked up the bearings, they only show one set for a f100, A-12 and A-13. So I looked up a f150 and they show the same set of bearings. So the bearings look like they are the same. If the rotors are different diameters, then the caliper brackets may not mount the caliper correctly.
#6
01-30-2016, 08:31 PM
I just did the same thing on the bearings. I also did the seal & calipers and it also list only 1 and I know they both mount the same way.
Did a little more hunting and AZ only lists the small bolt pattern but Advance Auto listed both but in MM spec. so did a little converting and came up with this:
114.3 = 4.5 bolt / 278.9 =10-63/64
139.7 =5.5 bolt / 297.7 =11-23/32
So I might be good? But would still like to know if the spindles/brackets are the same to be 100%.
Dave ----
Did a little more hunting and AZ only lists the small bolt pattern but Advance Auto listed both but in MM spec. so did a little converting and came up with this:
114.3 = 4.5 bolt / 278.9 =10-63/64
139.7 =5.5 bolt / 297.7 =11-23/32
So I might be good? But would still like to know if the spindles/brackets are the same to be 100%.
Dave ----
#7
01-31-2016, 04:43 PM
Well boys & girls we learned something today you CAN NOTswap large wheel bolt pattern (BP) rotors to small wheel bolt pattern spindle/caliper bracket assy.
Yes they both use the same inner/outer bearings and calipers and you can mount the small BP rotor on the large spindle. That is as far as I went with it so I would not lose the wheel bearings or get dirt on the spindle. I also did not care if the rest worked as I was not going to use the small BP rotor. So don’t know if caliper would work or not?
The trouble was when I went to put the large BP rotor on the small BP spindle the rotor would not go on all the way as it hit the caliper bracket and the dust shield. Could not get the outer bearing on enough to get the washer & nut on.
So now we know there must be 2 different part numbers for spindles 1 for small BP and 1 for large BP. I also do not know if the dust shields are different or if it is the mounts for them that causes them to hit the rotor so will look into that when I do a spindle swap as the dust shields that are on the large BP spindles are rotted.
Dave ----
Yes they both use the same inner/outer bearings and calipers and you can mount the small BP rotor on the large spindle. That is as far as I went with it so I would not lose the wheel bearings or get dirt on the spindle. I also did not care if the rest worked as I was not going to use the small BP rotor. So don’t know if caliper would work or not?
The trouble was when I went to put the large BP rotor on the small BP spindle the rotor would not go on all the way as it hit the caliper bracket and the dust shield. Could not get the outer bearing on enough to get the washer & nut on.
So now we know there must be 2 different part numbers for spindles 1 for small BP and 1 for large BP. I also do not know if the dust shields are different or if it is the mounts for them that causes them to hit the rotor so will look into that when I do a spindle swap as the dust shields that are on the large BP spindles are rotted.
Dave ----
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