12 bolt to 14B FF width difference.

[Cohl]

I have a 1970 Blazer with its stock 12 bolt. How much wider will I be once I bolt my tires back on the new 14b FF? Just trying to figure out if I need to change my wheel backspacing to compensate.

[ryanroo]

i dont know the exact difference if there is any. i think the 14 bolt is a touch wider than a 67-72 rear axle but not much. it also depends on the application of the 14 bolt. vans had wider rears and c&c and duallys had narrower wms to wms. some of the difference is in the hubs and some of them have different housings. i know the van housing is wider. i cant remember if the c&c housing is the same as a regular truck and the hubs are different or if the dually is the same with different hubs. one of them has a narrower housing. one has the same housing as a regular truck with different hubs.

so, i would say you can keep the BS the same.

here is my truck with a SRW K30 14 bolt rear. this would be the "standard" housing and hub set up on any SRW 14 bolt that came in any truck with a ff 14 bolt.

[Orange Crate]

Please read here:

http://www.pirate4x4.com/tech/billav...ble/index.html

[whitedog76]

The Single wheel 73-87's were 67". The Dually rears were 63". The one I had was actually 62.75" to be precise. There were some differences depending on application. GM also used Dana70's throughout the era. You can use the Dually hubs from a 63" on a 67" to narrow it up. You will have to use a Van drum though.

I want to say the 88-98's were the same, they just had more reinforcing on the center section.

When you get into the 99 and newer, they get wider. Plus you start seeing the 11.5" rears.