GM metric caliper performance/feel?

I'm researching good but relatively cheap disc brake swaps for my 67 Coronet station wagon, aka B-body. Right now it's an all-drum manual system with 11x3 inch drums up front. They actually work pretty well in the dry for what they are, but drums are drums.

The most intriguing option I've found so far is a bracket set that would allow me to use GM metric calipers on an 11.75 inch Mopar disc. It's made by Dr. Diff, who is of renown for Mopar rear end stuff: http://www.doctordiff.com/front-disc-brake-caliper-brackets-for-11.75-on-drum-knuckles.html

I priced this out using good parts – Wilwood's aluminum big-piston calipers, Hawk pads (so many to pick from, jeez) , Centric even makes nice discs in the size I need – and ended up being pretty much at the same price I'd pay for this all-Wilwood kit, which I was previously considering.

Here's what I'd like to know – how do these calipers work from a brake feel standpoint? Is the typical GM squashy-brake feel more of a booster/pad thing? I grew up with a couple of cars from the long-running metric caliper era and braking always felt like stepping on a stale loaf of bread. The OE manual system currently on my car is actually pretty firm and offers decent feedback on what's happening with the brakes.

It's mostly a booster-pad thing, IMO. That and poor maintenance. The slide pins are horrible to sieze up, and the calipers seize to the spindle, and the pads seize to the spindle... If everything is working correctly, they're great.

Careful with aluminum calipers. They tend to be noticeably flexible.

Knurled wrote: It's mostly a booster-pad thing, IMO. That and poor maintenance. The slide pins are horrible to sieze up, and the calipers seize to the spindle, and the pads seize to the spindle... If everything is working correctly, they're great. Careful with aluminum calipers. They tend to be noticeably flexible.

Cool, that's good to know. What've you driven with these calipers that you liked? Any specific pads that you personally know of? I've never been a huge fan of OE GM setups from the era of this caliper design.

For aluminum, are you talking in general or Wilwood's specifically? I was looking at these supposed "improved design" ones since they're only like $20 more than regular replacements: http://www.summitracing.com/parts/wil-120-7197/overview/

Whatever people put on Grand Nationals. I experience a lot of them, and they're usually far better maintained than your average bourge-mobile in the 80s.

Any later model "B" body disk will swap right one with the spindels. but have you check out Scarbird? https://scarebird.com/index.php?route=product/product&path=64&product_id=101 Change out your inadequate front drums for affordable disc with our US-made CNC laser-cut brackets. These cold-rolled steel adapters bolt straight on to your drum spindles- no machining is necessary to the spindle, nor any realignment. We use 1970-72 Ford full size rotors (11-3/4", same wheel bolt pattern and pilot size) and 1994-99 Dodge Ram 1/2 ton pickup calipers. This will NOT clear your OEM 14" rims, but will clear the stock 15" rims.

In reply to 44Dwarf:

I'm aware of the Mopar-parts disc swap - it's impossible to find used parts like that around here, which was kind of the whole point of the swap (save hundreds by visiting your local junkyard! maybe 20 years ago, now guys want $150-200 just for the spindles...). I wrote off that option awhile ago, there's no savings/benefit to it any more IMO unless you're one of those brand-parts-only guys.

And I considered Scarebird's bracket setup, but this is the GM Metric bracket kit I'm referring to (also edited my original post since this should've gone in there originally): http://www.doctordiff.com/front-disc-brake-caliper-brackets-for-11.75-on-drum-knuckles.html

For an extra $30, the adapters look way more substantial than Scarebird's. The caliper bolts through threaded holes in a solid plate, whereas Scarebird just uses nuts welded on to a much thinner piece of metal. Obviously unsprung weight is bad and Dr. Diff's brackets are likely heavier, but I'd put way more trust in DD's bracket for strength in such an important area. Plus I get brake hoses as part of the deal too, so there's my $30, right :P

Knurled wrote: Whatever people put on Grand Nationals. I experience a lot of them, and they're usually far better maintained than your average bourge-mobile in the 80s.

Thanks, I've already found some good tips searching G-body forums just now.

Secret_Chimp wrote: For an extra $30, the adapters look way more substantial than Scarebird's. The caliper bolts through threaded holes in a solid plate, whereas Scarebird just uses nuts welded on to a much thinner piece of metal.

FWIW i bought some scarebird rear disc brackets, and promptly sold them without even considering using them on my car. they were scary thin wjere they mounted to the axle(half the thickness of factory parts), and the caliper didn't even slide into the area it was supposed to fit. i was going to return them but they wanted pics of me measuring everything before taking them back, so i just offed them listing my issues and took a hit financially to be rid of them. i think you're doing well to buy elsewhere based on my experience.

Scarebird is a local (to me) Trans Am guy and he has been selling disc brake kits for years and has a great reputation in the TA community.

just for the record you must have used different parts than me, because substantial is the farthest word away from what they were.

Pat - you must have posted when I was still typing. I was mainly commenting on what sounded like folks comparing pictures on the internet, not your first-hand experience.

SEADave wrote: Just for the record, I have used Scarebirds parts and they are pretty darn substantial. I'm not saying Doc Diff's stuff isn't substantial in its own right, but I think without holding them both in your hands it is a disservice to be posting this kind of speculation based on photographs. Scarebird is a local (to me) Trans Am guy and he has been selling disc brake kits for years and has a great reputation in the TA community.

I live in the Seattle metro-ish area too, and I'm not saying Scarebird makes bad stuff or that that bracket's unsafe or anything like that. It was just a subjective impression.

Knurled wrote: Whatever people put on Grand Nationals. I experience a lot of them, and they're usually far better maintained than your average bourge-mobile in the 80s.

there is nothing special about the stock brakes of a Grand National compared to any other 78-88 G body- they are the exact same undersized brakes as everything else, except they got either a hydraboost (84-early 85) or failure prone Powermaster (late 85-87) brake booster... but the average GN will probably see less miles and is probably better maintained than the average G body...

maybe the booster makes all the difference, because the brakes on my 70,000 mile 84 T Type are awesome..

I'd not seen the Dif Docs stuff that nice set up too. He noted use the aftermarket GM calipers like most Circle Track supplier's sell. https://www.lefthanderchassis.com/v2a/products.asp?idcategory=1641 http://www.cmwraceparts.com/grp2A1.php

Personally I used buy from the second link often when I was racing.

Thanks for the link to dif docs as my 62 dart will need disks at some point and it too is a "B" body as it an early car not the later A body. so guess now i'll wait for an update on how you like them.

SEADave wrote: Pat - you must have posted when I was still typing. I was mainly commenting on what sounded like folks comparing pictures on the internet, not your first-hand experience.

got ya. didn't look at the time on the posts.

novaderrik wrote:

Knurled wrote: Whatever people put on Grand Nationals. I experience a lot of them, and they're usually far better maintained than your average bourge-mobile in the 80s.

there is nothing special about the stock brakes of a Grand National compared to any other 78-88 G body- they are the exact same undersized brakes as everything else, except they got either a hydraboost (84-early 85) or failure prone Powermaster (late 85-87) brake booster... but the average GN will probably see less miles and is probably better maintained than the average G body...

Exactly the point I was making - it's all in the vehicle, not really the design.

I kinda prefer the funky booster to the vacuum one. Have done lots of vacuum booster conversions on cold-air cars because even with all of the labor involved, it's still cheaper than repairing/replacing the electric unit.

And, really, it seems like what fails is the pressure bomb. When that fails, the motor runs constantly every time you apply the brakes. That eventually kills the motor. I had an idea while back to see if I could adapt Audi nitrogen bombs to the Buick system but ran into a pile of no longer giving a crap.

I almost want to install one of those systems in my car so I can see people's faces when I refer to a "pressure bomb" under the hood of this thing.