Brake part interchange 65 LeSabre 400

[JeKel]

Hello everyone!

I went to pull my '65 LeSabre 400 out of storage, and found that the brakes were completely gone. Rather than rebuilding and re-plumbing the 4 wheel drums, I would like to upgrade to 4 wheel discs with a dual chamber reservoir. My question is, I can only find conversion kits for the 65 Skylark; I'm guessing that I can use it for my LeSabre, but I'd rather not make a $1300 mistake. Are brake parts for the Skylark and the LeSabre interchangeable?

[NTX5467]

ONLY brakes for the Buick B/C platforms will work on your car, as a general rule.  The same year Skylark is an A platform and uses smaller brake drums. 

 

The 4whl disc brake "upgrade" seems to be somewhat popular right now, for some reason.  NO real need to go to the trouble and expense of doing the disc brake deal as the brakes on the middle-60s Buicks were pretty good "as is".  Plenty of drum and lining area.  PLUS, they had no real trouble locking the wheels in hard braking, unless the driver had enough finesse to prevent it.

 

Upgrading to a dual master cylinder is much easier, as that became factory equipment a few years later.  Probably just might need a master cylinder from a '67 or so drum brake Buick LeSabre, providing that the booster is the same booster.  That way, just a little  bit of plumbing for the lines and divider block (NOT proportioning valve) would be all that was needed, I suspect.

 

Repro brake lines might be available from somebody like Fine Lines, either in "steel" or "stainless".

 

If you still want "disc brakes", then look for a full-size Buick a few years newer than yours with the factory front disc brake set-up.  You'll need a booster and master cylinder, the proportioning valve/divider block/switch, and the related tubing.  All under-the-hood items, other than the front brake items.  Check to see if the disc brake spindles/knuckles will be the same for your model year, though, which also might need the matching suspension control arms (IF the ball joints might be different).  I don't recall the specific year that power front disc brakes were optional on the full-size Buicks, but it could also be 1965, in which case changing the spindles/knuckles would be more sure to fit your control arms.  Just be sure to get the repro lines as trying to build them from "tubing stock" from the auto supply, then bending them to fit, can be tedious and time-consuming.

 

NTX5467

[Pete Phillips]

"The same year Skylark is an A platform and uses smaller brake drums" ...and smaller tires (14-inch versus 15-inch for the large cars).

[JohnD1956]

Buick started disc brakes in the full sized cars for 67.  Then they used the 4 piston calipers ( Bendix I believe) similar to the Corvette units.  That lasted till 69 and then in 70 the more common single piston caliper system was employed.

The full sized Buicks had 5x5 wheel stud centers.  The Skylark/Special had the 4 3/4 (?).   So in addition to problems encountered switching to the smaller sized hubs in front, you'll also need to source some rims.  15" rims should be available in the 4 3/4 wheel stud pattern.  But unless you change the rear axle you'd still have 5x5's back there.

The rebuild of your system is probably a good idea, however, I would vote for determining what's wrong with your current system before moving forward with a big change.  Just fill your MC and pump it a bit, you'll see where the problem is right away.  Maybe it's only changing two or three lines, like the one that runs to the back along the frame rail and then the flex lines to the axles. Certainly less costly. 

 

 

[NTX5467]

Quote

 

Thanks for that model year verification, JohnD.  For the first years of almost all USA-brand vehicles, the 4-piston caliper was the norm.  It's what Corvettes used, which was the performance icon of that time, if that might matter.

 

As time progressed, the 4-piston calipers were deemed to be more troublesome.  MORE pistons with outer seals which could, with time, seep.  Plus more caliper cylinder bores to corrode (from moisture content in the brake fluid), with time, and similarly leak fluid.  So, the single-piston caliper was its replacement.  One big caliper piston, directl attached to the other side of the caliper, with just ONE push that also pulled the other side of the caliper toward the brake rotor.  Much less expensive and equally-good brakng power.

 

In the mean time, an industry (of sorts) grew up around sleeving the cylinder bores of the 4-piston calipers with stainless steel for the Corvette trade.  That fixed the corrosion/pitting issues for good.  By that time, though, the single-piston calipers were the normal type of disc brakes used on USA-brand vehicles.  It worked well and everybody was happy . . . UNTIL powerful engines returned.

 

Suddenly, the most powerful and highest-performance vehicles were using SIX-piston calipers.  This allowed "longer" brake pads for more clamping force against the brake rotor.  It ALSO meant a more consistent clamping force from one end of the brake pad to the other, rather than more force in "the middle" and relying upon the stiffness of the pad's backing plate to relay the force to the far ends of the pad, especially at the (suspected) higher pressures needed for stopping from the 200mph speeds these cars were capable of.

 

In the mean time, brake systems had obtained anti-lock mechanisms which could pulsate the brake pressures to help lessen brake lock-up.  This might have also been a reason as the more-piston calipers would use brake pads with backing plates which would have a higher resonant frequency and therefore have a more consistent and uniform clamping force during the entire braking event.

 

What allowed the return to multi-piston calipers?  One was improved brake fluids which didn't absorb moisture as readily which were more readily-available.  Castrol had its "LMA" fluid, back then, but it was more of a niche market AND people didn't flush their brake systems (as a matter of course) back then.  Such flushes became more needed when the Anti-Lock Brake Systems came online on vehicles.  Electronic-controlled valves for which any sticking would render them "inoperable" is another reason for periodic brake fluid flushes.  PLUS the wider-availability of automated machines to perform these activities (rather than getting under the car and all of the "pressure/release/refill" activities).

 

Another item is probably improved sealing materials and designs.

 

Back then, everybody knew how to rebuild drum brake systems.  How to hone the wheel cylinders and install a rebuild kit.  All pretty simple to do, albeit a little messy sometimes.  The simplicity of replacing a set of brake pads on a single-piston caliper system was even better, plus "no mess"!  Everybody was "in love".

 

As with drum brakes, the surface finish on a disc brake rotor IS critical to correct braking performance, especially just after the brake rotors are "resurfaced".  As the cutting lathe tip removes metal from the braking rotor surface, it leaves small grooves in the metal (just like the grooves on a phonograph record!  remember those?) from the outer edge to the inner edge of the pad contact surface.  Not unlike what a boring bar does to the inside of an engine's cylinder bore, either.  All done in small increments for the best resultant surface!!  Then, the "final cut" on the rotor is done "slow feed", followed by a "swirl finish" to smooth the edges and "polish" the resurfaced area such that the brake pads will not try to follow the grooves in the rotor. 

 

How does this affect initial braking performance?  Let me tell you!  I knew of the reasoning behind the swirl finish and that if it was not necessary, the factory wouldn't do it.  I purchased a pair of front rotors for my '77 Camaro, which were the "low cost alternative" at the time.  I was easy on the brakes, initially, as I knew there was no swirl finish and that a "wear-in" period would be necessary.  So after driving the car about 30 miles on the freeway, when I got to the surface streets, with not much traffic, I did some moderate-force stops from about 40mph.  First one was decent with a little "pull" at the end.  Second one had more brake fade.  Third one had MORE brake fade AND more smell of "hot linings" (which I'd never smelled before, with the prior linings, even after some really hard stops from higher speeds).  When I got to my car shop, I parked the car and let it cool down.  The brakes were a little better when cool, but I knew it was going to take more than just what I did to get them broken-in and the rotors' surface similarly broken-in.

 

The next day, more moderate-level stops.  Better stopping and less smell.  Then a complete cool-down.  Cycle repeat a few more times until "no smell" or fade.  NOW . . . I knew what was happening and why, BUT the average consumer will not!  Many feel that with "new brakes", panic stops will be no problem . . . which can be that way IF the brake rotor surface has the non-directional "swirl finish" as the final resurfacing operation.  Otherwise, a first panic stop (without the swirl finish) can result in brake fade and severe brake "pull", not things you want in a panic stop situation!

 

One other thing for the perceived popularity of disc brakes.  The rotor components and calipers can be "lightened" and pad materials made "more aggressive", such that less contact surface areas can be compensated for, which is not possible with drum brakes where "mass and surface area" are "king".  In the 1960s and 1970s, disc brakes and drum brakes had much more "meat" in them than they now do.  All performed very credibly in normal and higher-performance uses, typically.  Lighter vehicles which followed depending upon "getting the weight out", which disc brakes allowed to happen and still maintain reasonable braking performance.  AND the related parking brake mechanisms for rear disc brakes also received some scrutiny as to how they were actuated, with many having a mini-drum brake inside of the rear rotor as others mechanically applied the caliper piston via cables and linkage.

 

AND, as many don't drive on downhill mountain roads all of the time, or pull heavy trailers all of the time . . . which would require a higher level of brake performance and lack of brake fade, it's that "first stop" that matters most.  And, as mentioned, those prior drum brake systems would do that very well, with stopping performance generally dictated by the "tire/pavement" interface than otherwise.  As JohnD recommends, put some fluid in the system and see where the problems might be.  Then go from there.  The "shotgun" approach of "changing everything" rather than just what needs to be changed can be expensive, but generally less expensive than a non-OEM disc brake conversion kit.

 

NTX5467

[60FlatTop]

Rebuilding the original system with a $1300 budget should be very rewarding. I have done it on a few cars. One was so long ago I will probably do it again this year.

Bernie