<VV> Disk Brake for LM

[Sethracer at aol.com]

In a message dated 11/20/2013 2:52:19 P.M. Pacific Standard Time,  
info at california-camping.de writes:

Hi  folks,

what would you suggest to buy if you want to do a front disk  brake 
conversion on a LM Coupe?
I am not sure what to buy because there are  so many thoughts and offers 
out there.
Price range is between 545 and 1,150  USD - I am a little bit confused and 
would be happy to here what you think  about it or what you can recommend.
 
Ulli - As you are noting by all of these replies, there is a wide  
difference in opinions of front disks for the Corvair. Since I drive other cars  
most of the time, including a C6 Corvette, I am spoiled when it come to brakes. 
 The stock, street Corvair is actually suited perfectly for drum brakes all 
 around, since, under heavy braking, the front/rear weight distribution is 
around  50/50. With this distribution, the front brakes do not have to do a 
lot  more work than the rears. Contrast that with many other cars of that 
era which  almost lifted the rear wheels off the ground in a panic stop. (Even 
excluding  the Econoline pick-ups!) GM, of course, recognized this 
attribute and  placed the wider drums at the rear of the Corvair. If a Corvair is 
driven  to club meetings, to car shows and even to an occasional 
autocross/slalom, the  original drum brakes, if kept in good condition, are quite 
adequate. For regular  high-speed driving, or use in the mountains, only highly 
modified drums would be  sufficient. In that case it may be easier to switch to 
front  disks. GM never offered disk brakes on the front spindle used on the 
 Corvair. The spindle is like a smaller-sized version of the Chevelle 
spindle  used in several cars out of GM in the sixties and early 70s. One 
difference  being the driver's side spindle on the late Corvair has a feed for the  
speedometer cable. 
As noted by at least one respondent, changing over to disk brakes may  be 
an option, but unless the TUV tells you cannot change the master cylinder,  
you should definitely change to the dual master cylinder design. If you add  
front disk brakes, you will have to change to a dual master for the 
conversion  to be effective. 
Most of the front conversions use a sliding pin GM single-piston caliper  
(known in the HotRod industry as a Metric caliper.) Mid-80s GM intermediates  
used these cast iron calipers. There are several replacement  calipers for 
this design, offered in aluminum. They use the standard GM size  pads. D154 
is the industry size call out. The kits also use a GM  rotor, usually the 
S10 pick-up 4WD rotor. It slips on over the  original Corvair front hub, after 
a slight outside diameter trim of the hub. The  unique parts of the Corvair 
front-disk kit are the caliper mounting  brackets. These have to bolt on to 
the spindle and properly position the caliper  to "float" over the rotor. 
One thing to keep in mind is that almost all of these kits use parts  that 
were designed for cars with 14" diameter wheels, sometimes 15" wheels. A  
change to disks usually involves a switch to 14s or 15s. Finally, master  
cylinders. All OEM masters for disk/drum combos are different from  their 
drum-drum dual master equivalents. When disk brake pads wear, the  calipers "use" 
fluid, in that the fluid fills in behind the pistons. Master  cylinders for 
disks need a larger reservoir to keep enough fluid on hand. Drum  brakes, if 
they are correctly maintained, move the shoes out to the drum as they  
wear, and should never need fluid replenishment in the master, or, at least very 
 little. So a disk/drum master will have a larger reservoir for the disk 
side of  the system. Many - but not all - disk/drum systems use some type of 
limiter  in the line to the rear (drum) brakes. Otherwise, those rear drums 
will do 90%  of the braking and those new front disks will be loafing along. 
At the same line  pressure - created by your foot on the MC, drum brakes can 
be fully applied  and working, where disks would need a lot more pressure 
behind the piston  to do much of anything. 
The actual caliper/rotor mounting of the front-disk hardware is the easiest 
 part of the conversion. Hardware selection and installation/tuning of the  
hydraulic system to optimize the installation is the real hard work. In  
evaluating all of the suggestions from the people who supply and have 
installed  the kits, pay closer attention to those who have actually installed the  
hardware. Know the application for their install, preferable 
high-performance  street use, exactly which pieces they used, how they tested it and if 
there were  any drawbacks to their installation. 
 
My racing Corvair has 4-wheel disks, but I cannot recommend this  
installation for a street car, at least the way it is  installed.