Rear disk brake conversion WHY? any pros?

[Custom 68]

Not to start a fight or anything because I would like (I think) to convert to the rear disk but why? I mean on my 68 I converted to disk up front with a new prop valve. I have added an adjustable proportioning valve to the rear because they are so touchy. I had to do a panic stop or attempt to stop the other day and my rear locked up and sent me into a slide? I have since been adjusting the rear pressure to tone this down, I now feel I am relying soley on my front brakes to stop with very little pressure going to the rears.
so my question is 2 fold first do I have something setup wrong on my brakes? of course you dont know what all I have but it is power with a disk\drum proportioning valve and a conversion from GMC Pauls. and secondly, if my drum brakes will lock up (easily) what benifit is seen from the disk in rear?

Again I know there are vendors on here selling these so I am not slamming them I just am wondering is it more of a change because it sounds cool or is there benifits?
Thanks
Dave

[herb101]

For me, it's all about rotation mass and leverage. My Blazer is up in the air 6" and it's running on 35's. A rear disk conversion will offer more muscle to slow that extra spinning weight that's been added. I have already done a new booster (1-ton), new master cylinder (1-ton) and new calipers, new rotors, new braided lines, new pads and shoes, and new wheel cylinders, but even with all that, my breaks still need help.

On your situation, I think there is still an issue with bias. There should not be a dramatic difference in lock-up, but the rear should lock just slightly before the fronts.

Herb

[Longhorn Man]

if you havve a street driven 2 wheel drive 1/2 ton truck, that is unloaded, or hardly loaded most of the time, converting to discs would be a waste of time. They will do very little to help you stop and they weigh more.

[jkade]

Originally Posted by Longhorn Man

if you havve a street driven 2 wheel drive 1/2 ton truck, that is unloaded, or hardly loaded most of the time, converting to discs would be a waste of time. They will do very little to help you stop and they weigh more.

I will have to disagree with that. I have 72 front and implala disc on the rear of my 67 and it will stop on a dime and not lock up the rear tires. I am running 20's all the way around so that might have something to do with it but I think it is a great investment and you can put a kit together for less than $250 if you shop around.

[Custom 68]

Andy, that was kindof the direction I was pointing to also, my tires are 275/15/60 so they are not as heavy as say jkades 20s or herbs 35s so maybe that is where the difference is made?
I have fought or had concerns with my rear brakes for quite a while. I will keep digging but keep the coments coming!
thanks guys
Dave

[SactoJim]

I put rear discs on mine and to be honest, I'm not sure if they work better or not, but I'm sure they didn't hurt the way it stops.

Just take a look at the OEM's......I don't think there are too many new vehicles (including trucks) that don't have rear discs, which says something to me.

Sometimes some of the things we do to our trucks doesn't have to make sense and besides....rear discs are kinda cool!

[herb101]

Originally Posted by SactoJim

I put rear discs on mine and to be honest, I'm not sure if they work better or not, but I'm sure they didn't hurt the way it stops.

Just take a look at the OEM's......I don't think there are too many new vehicles (including trucks) that don't have rear discs, which says something to me.

Sometimes some of the things we do to our trucks doesn't have to make sense and besides....rear discs are kinda cool!

I think GM has actually stopped discs on the pick-up line (at least the heavier ones). {flamesuit on - I said THINK - lol}

Herb

[SactoJim]

Think you're right Herb. Don't recall seeing discs on heavier trucks.

[1fun71]

I have a 07' GMC Sierra new body style GMT900 I believe is what they call the half ton now. It has drums on the rear.

[PanelDeland]

I doubt there's much advantage to them since the rear is usually light unless it's a work truck.The main thing I see for going with them is if running big open style wheels.They just look cool.However if the drums are painted and match or contrast with the paint on the truck they look just as good to me and I consider it foolish to spend money on a "Hot Rod" that doesn't make it perform better.

[Custom 68]

Thanks guys, my Tahoe has rear disk but I do think they quit doing that also the newer stuff also has ABS so that may help some?. but regardless they are cool that is probably why I have been looking and asking
I will try to work on mine some more, I am just not happy with the way they stop I may remove the adjustaable valve maybe that is getting me?
thanks
Dave

[N2TRUX]

The reason GM quit putting discs on the rear of their 1/2 ton trucks is because they were too cheap to do it correctly. They put too small of a disc in the rear and had problems with warping rotors.

Having had multiple trucks with rear discs both converted and factory I can attest that rear disc is the way to go. It must be done correctly, with the right size rotor and caliper, but it offers a huge advantage over drum brakes.

The common misconception is that drum brakes work just fine because they can be made to lock up. That will only cause you to skid, and we all know that is counter productive to stopping.

If you use the proper components, and the proportioning valve is set with the correct bias rear discs will greatly improve your braking ability...

[whatnow123]

I put rear disks on mine, I haven't driven it yet so I don't know if there was an improvment over drums, but I did it becuase of looks with my wheels.