mar3

iTrader: (8)

1980 GS with the drum brake rear...did a chirper for my buddy who was waiting for me at my house. No one, even me, believes this is a stock, untouched rear...I just can't figure out why the previous owner didn't get the disc rear-end instead of putting a posi in a drum rear-end...stranger things....

peejay

Open diffs can rip 'em both up if both tires have equal traction.

Why would you want the disc rear end? The discs weigh more and you don't really need them with a car that light...

riffraff

you really donot think that you need rear disks in our car? i figured the stoping power would be a hell of a lot better with them

repuguru

It is. You also have the benifit of a LSD 3rd member. Even though your current open rearend slipped both tires in a strait line it will not power both drive wheels while going around a curve in which your drive wheel loses traction. Thats why your drive tire can spin like hell when going around a corner.

mar3

iTrader: (8)

It does the infamous 180 degree turn if I nail it from a corner, just like my parents' '85 GSL which has the discs and posi. It's got a posi...I'm thinking since it's a CO car, the previous owner had it done so he could go up snowy hills...

hanman

From reading informed opinions on the disk brake subject, the consensus was as long as you don't have the "wedge" style drum brakes, you really are not going to gain anything with the disc. But, the LSD will really help.
hanman

peejay

Hanman I think you are confusing the wedge type CALIPERS...

One thing you must consider is that drums actually have more stopping power than discs. (Try to drive a car with power-assisted 4-wheel drums and you'll see what I mean) However they do not have as good fade resistance. They heat-soak easier. Given that the cars are fairly light and not very powerful, but the time you get back up to speed the brakes will have cooled back down again.

Another advantage discs have over drums is that they are easier to modulate than servo-type drum brakes. However the '79-80 models have non-servo drum brakes which are almost as easy to modulate as discs.

Where I live, rear disc brakes are a joke. They usually do so little work that they sieze up before they start wearing out. You pretty much have to go in there and lubricate the slides and work the pistons back and forth every 6 months if you don't want to buy new calipers, pads, and rotors every year.

mar3

iTrader: (8)

If it's the two-screw-adjuster style brake drums, should I go ahead and convert to disc? I can get a rear for $75, but it would need calipers rebuilt and new rotors before it could hit the road again. I guesstimate $350 total cost to get it in, but is it worth it? The car sees heavy street action but will never see heavy autox or road race duty...what's your thoughts, peejay?

peejay

The manual-adjust brakes IMO are the best drum brakes. No worries of the self-adjuster screwing up and causing the brakes to drag, and they are dead simple too.

mar3

iTrader: (8)

Got it...I'll spend the moolah on a twin Accel direct fire set-up, instead...check out this month's Car Craft as to why....coil included for each, maihn!!

peejay

Also snag the centersection from a '81-82 GSL...

riffraff

does any one know which years had which drum breaks?? the ones on the rear of my 79, what would the opinion be??

85RX7GS

iTrader: (1)

Thats pretty nice. On this old road near my place, I got my stock 85 GS sideways by just revving it up to 4k and dumping the clutch. I nearly spun 270 degrees, but it caught me by suprise so I hit the brakes. Whew! I'm lucky there weren't any cops.

riffraff

yah. i love getting my 79 sideways...
last time i did it was from simply a 2k dump.. (ofcourse my seven is not quite stock)

peejay

All years (on North America) had drum brakes. The rear discs were packaged with limited-slip and were on the GSL and GSL-SE ONLY.

riffraff

peejay, i know that.. but you guys were talking like there were two differnt style drum breaks on the sevens.. that is what i was woundering

peejay

Oh, okay. SA's (Series 1, '78-80) had manual-adjust drums. FB's (Series 2 and 3, '81-85) had self-adjusting drums.

I personally don't like self-adjusting brakes because either the self adjusters stick, meaning you have to adjust them manually ANYWAY, or they work too well and cause the brakes to drag. With the manual adjusters, you can set them exactly where you want them.

riffraff

so if i understand what you are saying correctly, there is no reason for me to replace my rear drums with disks.. (this is on a 79)

peejay

Well, you COULD. I mean, if you get the disc rear for free or cheap, go right ahead. You shouldn't have problems with corrosion, being in California. I'd say it's a wash either way. If you plan on going for big power or do a lot of downhill runs, it wouldn't be a bad idea to go for them in advance. Just keep in mind that the handbrake won't work as well as it did when you had drums.

riffraff

well considering the hand break does not work all that well right now...

i would like to eventually do a little bit of road racing, but it is not that often that i do down hill stuff... as far as power, if i keep it n/a then i will not go that high (maybe 200 to the wheels) but if i go ahead and slap a turbo on her, then that is a whole nother story.

4ohfour

NEWBIE ALERT NEWBIE ALERT

what is a posi and what are the benefits of having one?

cheers'

peejay

Posi (aka Positraction) is Chevrolet's brand name for their limited-slip differential. No car other than Chevy have a Posi in them.

Limited-slip diffs basically limit how much one axle can turn in relation to the other, normally by using preloaded clutch packs against the side gears. For one axle to turn faster or slower than the other, the side gears have to turn in the differential, and the clutch packs resist this.

MarkPerez

peejay,what about detroit lockers,,boss mustangs,
shelbys,even an 'N' case 9'inch ford stuff,,i think full
size bronco's have them too, not just bowtie stuff

nimrodTT

peejay is saying that Positraction is one of those name brands that become a generic name - like Kleenex or a Cresent wrench. Everyone knows what youre talking about but only Chevy can legally use that name for a LSD.

mar3

iTrader: (8)

If I pull the pumpkin from one of those year disc rears, will it still allow my '80 axles to pop in? The LSD in this one has got to be on its last legs and I'd use the opportunity to get a gear set change and not have the car immobile for more than an hour as opposed to days if I tried to rebuild the one from the car. She's my daily driver...