Posted by CSCameron [71.223.220.155] on Sunday, November 01, 2015 at 19:09:27 :
Me again. I was able to take some measurements today. There is very little room between rotor and rim to do anything. As such, I don't believe a low enough profile caliper could be made that would allow clearance of the valve stem in this application. So, barring re-engineering the brake system, or finding a different style tube that would work, I've determined that there are three basic options to run duals on the FFPW.
Option 1: Have a 1" spacer made to run between the stock rim (inner) and the dually rim (outer). This will yield 1+" space between the tires (1.2" would be optimal) and brings the overall width of the truck to ~97". Using the stock rim on the inside position means no clearance issues regarding the rim and brakes. This option would require the use of the longer Budd lug extensions (2 9/16") to mount the outer rim. A benefit of this option is that to return to the stock setup, just remove the outer dually rim, spacer, and lug extensions.
Option 2: Have a 2" adapter made to bolt to the hub. This will replace the 3/8" spacer that was part of the disc brake conversion kit. This moves the inner dually rim out approx. 1 5/8" net to clear the valve stem from the brake caliper. Once installed, the inner dually rim would be mounted and cinched with the standard Budd lug extensions(2 7/32"). Then the outer dually rim would be mounted. This set up gives the proper tire clearance but does extend the width of the truck to ~98".
Option 3: As suggested on the forum, remove the rear disc brake setup and return to a stock rear drum setup. Then have the brake drums machined to clear the inside dually rim. Then you can just mount the dual/dual rim combo, apparently without drama. I think I'll keep my disc's, however, this would be worth looking into if you have the stock brakes and are interested in running duals. Comparatively, it seems like it might be pretty painless.
With either the spacer or adapter option, I would use steel, not aluminum. I think having a spacer machined will be less expensive than an adapter because of the complexity of the adapter. However, I would rather run the dual/dual set up which requires the adapter, because of the built-in correct tire spacing and I think it would be stronger overall.
The pic should help clarify what I am referring to...
Of course, if you were to choose different tires, all bets are off... :)
This next week I'll be determining how much a spacer and adapter will be. To be continued...
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