From the archives, I think everybody agrees that the C2 drums work pretty well when set up right, and that the discs may be a bit better, to the point where tires become the limiting factor, but I wondered if there was any stopping data distance.

I did find in the archives somebody's old post of the Car and Driver 1967 L89 road test. The test car had power disc brakes and stopped from 80mph in 257 feet. The car's test weight was 3563 lbs. Brake swept area was 461.2 sq. in.

Interestingly, according to R&T, the current Z06 stops from 80mph in 189 ft, the base C6 in 212 ft, the Lexus LS460 is near the bottom of the heap at 251ft.

Anybody have any C2 drum brake data?

 

The drum brake's stopping distances are also limited by the tires.

A lot of the differences you posted in those stopping distances are because of TIRES and weight transfer, not brakes.

There may be a possibility that the tires on today's ZO-6, for example may not be a limiting factor in stopping if they were placed on a mid-year with either disc or drum brakes WITHOUT a power booster. I don't know if you could apply enough pedal pressure with manual brakes on the old cars to slide those big meats.

 

The disc advantage is more than just stopping distance too. They repel water after running through a puddle, use less heat when stopping, etc.

 

Its tires and antilock brake systems. The rest of the stats are relatively minor factors, until you try to stop the second and third time. The big advantage to swept area and disc brakes is the fade resistance. If you have ever experienced real brake fade (to the point where they simply stop working) you'll be a believer in big disc brakes!

Harry

 

Discs have several advantages, and require much less maintenance overall. But they do add constant minimal drag and are dirtier (from brake dust).

I changed to front discs on the 62 simply because of braking directional stability. New "everything" drums were still prone to very uneven directional stability while braking. That went away immediately upon switching to front discs. Overall braking appears to be about the same, with a slight edge to the discs. And I have not "touched" them (other than cleanup) since install (going on 3 years ago), while the drums (so it seemed) to required constant adjustment.

Plasticman

 

The way I see it, if you're overdriving a set of mid-year drum brakes on the street, you should probably be in jail to protect the public from your reckless driving.

No question about it, Discs are superior on the race track, through water and consistent directional stability. If there's a problem with directional stability, there's a problem with your mechanicals, somewhere.

 

My experience is identical to yours John. Additionally, I've been on more than a few long hauls and the discs are definitely better in the rain when you're using the brakes more often. It sometimes got a bit scary when I had front drums and the brakes faded. But the discs solved that.

- Pat

 

Almost every cool car I've ever owned started out with drums, but as soon as they needed rebuilding I converted to discs, some with power, some without. I've never regretted the swaps. Just remember to keep the original equipment in case you want to switch back in the future.

 

Mike,

In 1972, I was driving my new bride and all my worldly possessions to my first duty station, from NJ, across the USA to Yuma Arizona... We were driving my "hot-rod" Falcon with all new drum brakes. (Brakes that had no difficulty stopping it's 2900# from north of 100 mph on the drag strip.)

Unfortunately as we were crossing the continental divide, we happened to get behind a new 5000+ pound Chrysler New Yorker that must have had disc brakes on it. There was no room to pass and he insisted on driving (with the use of his big disc brakes), just below the speed at which my little Falcon was happy coasting. In short order I realized I had almost no brakes as I was pumping as much as I could just to keep off of his rear bumper. (If you've ever been there, you know this not a fun place to be!)

None of this is impressing my new bride and the look on her face told me it was going to be a cold, lonely night if I didn't quickly get us out of this situation.

Fortunately we hit a short rise and a scenic turnoff about this time and I was able to pull over and save my bride and myself from a trip down the side of a mountain. We waited for about 30 minutes to let the brakes cool and give Mr "New Yorker" time to get well ahead of us.

I decided this was an omen that the Falcon needed a set of disc brake on it. Believe it or not I found a Shelby, Mustang, GT-350 in a local junkyard within a month of arriving in Yuma...

GUSTO

 

Cute story but but my example was about mid-year Corvette brakes, not the tiny brakes you find on a 6 banger Falcon.

I too, used to drag race a '61 Falcon. It had the full Shelby 289 in it with a top loader and 9 incher. Mustang V-8 drum brakes.

This thread is a little off track. The original poster wanted to compare stopping distance, disc vs drum. Not which is better. Or maybe I read it wrong.

 

No offense is intended, but the Falcon was no 6-banger. It ran mid 13's with slicks, had a 9-inch ('57 Ford) in the rear and stock V-8 (Mustang) brakes in the front. All of this was adequate... up until it wasn't.

I also still have the '63 Corvette I owned at that time along with it's drum brakes... which is why I was paying attention to the thread... and trust me, my situation was all about stopping distances!

The bottom line is that under normal circumstances and even a few extreme situations (such as at the end of the drag strip), the drum brakes are fine when well maintained. However, those times when you find yourself outside of the box (such as trailing a slow moving vehicle down a mountain pass?) you will quickly realize the limits of your drum brakes. You may never get there, but if you do... hang on!!

I'm currently doing a frame-off on the '63 Corvette (after 36 years in storage) and intend to replace the front brakes with a disc set-up. I personally like the drums in the rear of the mid-year because it gives you an excellent parking-brake. However since most of the actual stopping comes from the front, I will replace them with disc... I like to think of it as the best of both worlds.

GUSTO

 

True, but my point was that there are other valid reasons to change to discs (other than just stopping distance). If the vehicle veers into another lane with (new everything) drums, and is constantly needing adjustment with drums, and then cured by disc conversion, than that is reason enough. I am not a newbie with drums, having dealt with them since the 1950's, but sometimes it just is time to throw in the towel and admit defeat. I don't doubt there was something else wrong, but it is consistently reported on the forum that the conversion to discs works well. Discs offer better stability and reliability, and GM (and the rest of the auto manufacturers) did not stay with drums because drums were "better"....end of story.

Plasticman

 

I know what your point was. It's all valid. I too am no rookie when it comes to drum brakes and I'm very familiar with their shortcomings and the fact they require more attention than disc brakes.

The guy simply asked for stopping distance with drum brakes on a mid-year.

That's the end of the story unless you'd like to add something.

 

It's NOT just about stopping distances, but about consistency and repeatability.....and Feel. If I was still running drum brakes....the best in the world in 1963 BTW....I would be dead now. There are thousands of different brake pad materials available for discs.....and almost none for drums. There is NO comparison. go to discs....the stock K-H discs are (still) excellent brakes with modern pad material.

 

You should start your own new thread. This one asked for stopping distance comparison, not "consistency and repeatability.....and Feel".



"From the archives, I think everybody agrees that the C2 drums work pretty well when set up right, and that the discs may be a bit better, to the point where tires become the limiting factor, but I wondered if there was any stopping data distance."



Can you stay on topic and answer that question?

 

Mike, I hope you see the irony in your comment. You have posted 5 times in this thread without answering the question.

- Pat

 

He is practicing to be a moderator.

Just to be back on track I have the following road tests:

1984 Vette coupe: 80 to zero in 250 feet. And by most accounts (mine included), the 84-87 Vette brakes were the worst ever used!
1978 Vette coupe: 80 to zero in 244 feet.
1977 Vette coupe: 80 to zero in 265 feet.
1973 Vette coupe: 80 to zero in 314 feet!
1970 Vette coupe: 80 to zero in 310 feet! (Had BB 454)

Some earlier tests from Road & Track only measured Deceleration in % G (not distance).
1970 Vette Convert.: 84% @ 80 to zero
1967 Vette Convert.: 75% @ 80 to zero.

Even earlier tests did not measure braking at all.
1965 Vette Convert.: Brakes not tested.
1965 Vette Coupe: Brakes not tested.

Then earlier tests check braking in ft./sec/sec.
1964 Vette coupe: 20 ft./sec/sec. Same reading seen for 2nd stop.

And then the very early tests did not show braking performance, period.

Plasticman

 

Plasticman has answered the question.. 20ft/sec squared is 62.5% of a g (1g = 32ft/sec squared) so the discs are quite a bit more efficient than the drums even in 67 at 75% with old pad technology. With new pad technology they probably get to 90% with the advances in tire polymers as well. I have Pirelli 4000 tires on my car and I know that they have a larger contact patch and are a lot stickier than 60's bias ply tires. Only really old people stick to drum brakes

Another thing to consider when you are "beating the drum" so to speak, is that all the cars around you on the freeway or the street have both disc brakes and larger tires than your vette and sooner or later you will hit one of them when they panic stop in front of you unless you are saved by the "automatic lane change" feature of the crappy drum brakes that are as modern as a crank starter...

I found that the Michigan Highway Patrol tested a 3/4 ton 4x4 suburban and it stopped from 60 in 156 feet. I found a road test of a 67 427 and it stopped in 176 feet even though the Suburban weighs almost twice as much - tires and abs...

You need disc brakes and you need not to tailgate

http://www.officer.com/web/online/Operations-and-Tactics/Michigan-State-Police-2008-Model-Year-Vehicle-Tests/3$38828

http://www.corvetteactioncenter.com/...67/67prod.html

 

I do, I do. Believe me I do. I was just hoping to suck an anwer out of somebody to get this guy's question answered. Actually, I did look through my old Hot Rod's from '61 through '65. There were a couple of driving impressions but no stopping distances posted. I know Motor Trend did a complete road test on the '63 Sting Ray but I ran out of time to look.

 

Plasticman hasn't answered the question and you haven't answered the question either. I'd bet the 20 ft/sec listed is not a constant for the duration of the braking for starters. Both the disc and the drums of the era would slide the OEM tires so I don't know how you can claim: ( "so the discs are quite a bit more efficient than the drums even in 67 at 75%") Further, you totally ignore that the drum brakes will overcome the tires of the times.

Further, you ramble on about old/new pad technology and your Pirelli tires that they didn't have in the '60's. You further go on to say that others around you on the road have disc brakes and larger tires and therefore, sooner or later, you'll hit one of them because of the automatic lane change feature. I think you need to go back and edit your post to make it coherent and logical.

Here's the only solid statement you've made in your post: "you need not to tailgate"


The May, 1963 issue of Motor Trend says 1963 Corvette stopping distances are:

30 mph 30 feet

60 mph 134 feet

Motor Trend, who was a proponent of disc brakes had this to say about the Corvette drum brakes:

"The brakes in the test car were used very hard at the end of several high-speed runs and showed very little tendency to fade. ......once they get warmed up, they're excellent. Self adjusting brakes are now standard equipment............. The brakes in our test car pulled the Sting Ray down to quick straight-line stops time and time again without any sudden locking of the wheels and without apparent fade. Several stretches of mountain roads showed that they could stand up to prolonged hard use without failure.

For all-out competition there's a special performance (drum) brake option that includes a little more effective brake lining area, bigger finned drums, power assist and a divided output master cylinder. Combined with the optional cast-alloy wheels (knock offs), this set-up gives the competition Corvette braking power on par with many of it's disc brake competitors."


So, that's what they did when they were new and working correctly, not 45 years later with who knows who working on them.

That 130 ft stopping distance from 60 mph they listed was about 30-35 feet better than other cars of the period. Many cars back then would take 160-180 feet to stop from 60 mph. Again, tires being the limiting factor. Not the brakes.

It's the SECOND hard, high speed stop on drum brakes where brake fade would come into play.

Yeah, I know I still haven't answered the 80 mph to zero question.