8.5 GM Axle strength

[Anubis]

Wait, What???

I’d consider rear disk brakes for the cool factor. Not because they’re necessary

 

[454cid]

I’d consider rear disk brakes for the cool factor. Not because they’re necessary

Let me say up front, that I've never done a disc conversion myself. However, from all the conversions I've seen online, I'm not very impressed. They all seem to use Squarebody front calipers or Cadillac rear calipers from the late-70's/early-80's. Why not some of the newer calipers that are available, I have no idea.

If I were to do a disc conversion, I think I'd go a different route..... grab a newer axle from a GMT-800 (or later truck?) and move the spring perches and shock mounts.

 

[Schurkey]

There’s nothing wrong with drum brakes in the rear. I’ll admit disc brakes are better in preventing brake fade but in my opinion there’s nothing wrong with the 8.5 set up for the rear end. Drums probably have more apply area than discs do. The front disk brakes however need to be addressed.

The leading/trailing shoe design on the 8.5" axle is a travesty. Everyone, especially GM engineers, knows that nobody uses the park brake regularly. So GM releases a rear drum assembly that requires regular park-brake use to stay in adjustment. Friggin' criminal.

Then there's the problem that the front shoe on each side wears out five times as fast as the rear shoe. JUNK.

OTOH, Duo-servo brakes have been in production by the millions, for decades. Pretty-much every potential problem with them was worked-out a long, long time ago. They're all but bullet-proof. Add in the larger diameter of the drum, the wider shoe, and you've got a far superior rear brake on the 9.5" axles.

 

[stutaeng]

Let me say up front, that I've never done a disc conversion myself. However, from all the conversions I've seen online, I'm not very impressed. They all seem to use Squarebody front calipers or Cadillac rear calipers from the late-70's/early-80's. Why not some of the newer calipers that are available, I have no idea.

If I were to do a disc conversion, I think I'd go a different route..... grab a newer axle from a GMT-800 (or later truck?) and move the spring perches and shock mounts.

/\ This /\

I drove my Dads '89 RCSB C1500 when I was 18 a few times many years ago. I can't recall how brake pedal feel was (probably didn't have enough experience to tell anyway, LOL.) But my youngest brother has driven it a few times lately and says brakes are really spongy.

I agree on the disc conversion with the 70s/80s stuff. Doesn't make sense, but I think it works out with the e-brake or something. "If" I ever would need to do a disc conversion on the 10 bolt drum GMT400, I'd be looking for a 99-02 1500 truck.

My 99 NBS has 260k miles. About 5k miles ago the front started squealing just a bit on the second set of pads and I replaced them and rotors. The first set of front pads was done around 150k, replaced with dealership pads, kept original rotors. At that point, my mechanic said rear had plenty of life left, so I left them alone.

This time I thought surely the rears must be ready to be replaced. I removed the wheels, and rear pads are still good! So 260k on original rear pads and rotors and still going! I think brakes are okay on that truck BTW. Can't complain! It's a shame GM reverted back to the drums on the 03-07 1500 trucks though.

 

[Schurkey]

If I had 260K on rear pads, I'd wonder why the rear brakes don't work.

 

[454cid]

If I had 260K on rear pads, I'd wonder why the rear brakes don't work.

I was thinking the same..... sounds like they are just along for the ride.

 

[stutaeng]

I was thinking the same..... sounds like they are just along for the ride.

Um, I never thought about that... But truck was driven all across the country, including a few times in Sierras in California and Rockies in CO. Even once made a trip though the treacherous Sierra Madre Sur in Southern Mexico: 5-6 hours of nothing but going uphill or downhill, switchback roads trying to pass double tandem trucks loaded with portland cement going like 10 K/hr without falling off the cliffs. On the way back I had about 1,500 lbs of various "souvenirs!"

In fact, heard guys driving down there from 'merica will overheat their brakes on those roads in that area. It's been a while, but I don't recall not having enough stopping power. But most of my miles were highway, so maybe that's why?