smilesyota

Hello, just bought a 90 w350 and the brakes are destroyed!
will a disc brake work with the dual rear wheels? what rotors can be used?
I have a set of 4x4 chevy 8 lug rotors from a k20 with some half ton front calipers but will they clear the inside rim?

PS the drum exploded! nothing left on one side. that is why I'm thinking the disc route.

thanks.

apwatson50

From what i've heard/read they won't clear 16" duals. If you had 19.5" duals they would clear.

wannadiesel

What he said.

A new drum is just a tad cheaper than 19.5's.

RamW350 dually

Could you buy new brake component parts from an auto parts outfit to do a rear disc conversion on a dually D70 or D80 rear or is it recommended to buy a kit specific for them? I'm sure a specific kit would cost a good bit though. Would it be easier to convert a Dana 70 or Dana 80, since the 70 has inboard brake drums and the 80 has outboard brake drums? I think the 80 would be, but I don't know a whole lot about converting over to rotors and pads in the rear. I think it would be a pretty cool modification, even stepping up with the 19.5 wheels too. The Chevy 14 bolt dually rear can be changed over and they actually covered it in an article in the last issue of Diesel Power magazine (thought that was cool). Made me want to change over to rotors/pads on my truck too.

wannadiesel

You can get all the parts except the caliper mount brackets at the auto parts store.

It does not make a difference what sort of hub you start with.

smilesyota

Im going to order a set of weld on caliper brakets from ballistic fab.
I think it can be done! all of the new trucks have disc in the back.
It will take a little work thats all.

smilesyota

I've come across two 14b rear axles and have a disc brake swap that would work with this axle. would that be a better swap in the long run?

Mopar Kid

I'd rather run a 14 bolt rear any day of the week I love them. But on the disc brake set up I'm with wanna that they will not clear 16" wheels because the inside wheel is set so far to the inside. I need to just get a dang 16" wheel and slide it up on my disc braked 14 and see cause if it can be done we need to on one of our trucks. All the new trucks run discs on the rear but also all are running 17" wheels or bigger so think about that too.

BearKiller

Not all of the factory disc-braked tons are 17s, as I see several Fords with 16s and rear discs.

I have not tried this yet myself, but I sort of figure that the wheel clearance issue is very much like when, back in the seventies, MANY, myself included, opted to run 15-inch wheels on their 3/4-ton Chevy 4x4s (due to the VERY limited selection of decent off-road tires in 16-inch, whereas a vast selection of 15-inchers were available).

The fifteen-inch wheels would not clear the calipers on the disc-braked front, BUT about thirty minutes with a good 9-inch Milwaulkee grinder, knocking the corners and the casting ridge off the calipers, and those fifteen-inch wheels would spin like a top.

I have a 1978 Chevy in the yard that I personally did this to over 400,000-miles ago, and I have never had a negative issue from removing that un-necessary metal.

I could very well be wrong, but I would bet that some judicious caliper-grinding would allow the DRW 16s to clear with ease.

Someone that actually has a SRW rear-disc-CONVERTED axle could try a DRW inside wheel and see just how much smaller the caliper would have to be to work.




My main hold-up at changing mine over to rear discs is the sacrifice of my constantly used park-brakes.

A drive-shaft park-brake would need be invented (or taken from an old GM ton-and-a-half or two-ton truck), before I would remove my drums, and I have no idea just what negative impact spinning this big mass of metal on the drive-shaft would have on power/mileage.

I have and constantly use the MICO line-lock, but hydraulics can bleed off, whereas that stretched/locked cable ain't going anywhere.




Another point to consider on a trailer-hauling truck is the loss of brake surface area between properly trued and adjusted drum-brakes, as opposed to the comparable miniscule amount of surface on a pair of disc-brake pads.

Granted, discs/rotors can't get hot and the drum expand to a larger diameter such that the shoes no longer can reach it; and, discs don't get out of adjustment, so those too lazy to properly service/adjust things have one less thing to worry about.

Also, compared to having to do the open-heart surgery necessary to replace a set of drum-brakes and wheel-cylinder, the five minutes required to swap a set of brake-pads is a cake-walk.



Another point, the reason most of the factory rear-disc-brake equipped trucks will stand on their nose so easily has more to do with them also having HYDRO-BOOST.


Before I converted to rear discs, I would install a HYDRO-BOOST system.



Just my nickels worth.

BearKiller

For what it's worth, the 70s-87 GM 1/2 and 3/4, and probably many of the tons, use the same caliper.

smilesyota

thanks for your two cents bearkiller, good points! I will try two fit the dualy wheel over a friends chevy hd 2500 and see if it clears. I will take some pics and try and post them later.

ppiggppenn

don't rear disk systems have a dumb-down device to keep them from locking up?, .... maybe if the RWAL system can be adapted to this then no problem

wannadiesel

The dump valve can't handle the volume of fluid the calipers use, it runs out of capacity and stops cycling the brakes quickly.

Alwaysworking

ford f-super dutys from the 90's have rear disk brakes on a dana 80 with 10 hole 16's

BearKiller

Yes they do, and stupid me procrastinated about ten-minutes and let a cab-burnt one get away for $1500.