When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey all I have a friend that has a 1966 Starfire and is trying to do a disc brake conversion. Question being is where is a good place to find this conversion kit.
The 1965-1970 full size Oldsmobiles are not particularly popular and thus are not well supported in the aftermarket. You only have a few options here. First is to install a set of the optional factory disk brakes, preferably from a 1969-70 car with the single piston calipers. The downside here is that no one sells replacement rotors for that application, but you can adapt the rotors from a 2010 Camaro six cylinder with minor machining mods. This is probably your best choice. The second option is the Scarebird brackets. This application uses custom hubs and Ford (?) rotors. One other option is to configure a performance disk installation from Wilwood. The latter yields the best brakes but at the highest cost. No, Impala disk brake kits do not fit an Olds.
I used and can vouch for the Scarebird kit, all worked great and has been for a few years now. When you get the kit it will tell you to get, for instance, rotors for XXXX car, calipers for XXXX car etc.I think mine used some late 70's early 80's Monte parts, I could check for you if you need that info. Super easy to install. I was concerned with setting the prop valve but it was a non issue it was so easy. I don't recall 100% but I think you will need 15" wheels as well.
There are a couple of more options for this conversion. I researched for a 1966 98. Kanter's has a complete kit with 12" rotors and single piston calipers; including M/C, booster and proportion valve for $1299. Classicdiscbrakes.com has both for just at the wheel or complete at corresponding prices. They sell the prop valve separately. Again, 12" rotors and single piston calipers. Some wheel size/configuration may be a problem. I am using 15" Buick wheels.
The problem is that not all "12 inch rotors" nor all "single piston calipers" are the same. The stock disc brakes on the 67-70 full size cars used 12" diameter by 1.25" thick rotors. The 69-70 single piston calipers used 2.75" pistons - they are the same calipers as used on the half ton pickups. The Eldorado rotor mentioned above (which is the same part used on 69-78 Toros and Eldos) is only 11" diameter by 1.2" thick. Most of the aftermarket disc brake kits for these cars use the later metric calipers that only have 2.375" pistons. That's a 25% reduction in piston area and thus a 25% reduction in braking force for the same pedal pressure. Not my first choice. In converting my 67 Delta, I'm using the Wilwood D52 calipers that have two pistons and 10% more piston area than stock. And finally, my biggest concern on all aftermarket disc brake kits are the flat plate caliper brackets. Every single factory installation that uses sliding calipers has "ears" on the bracket that guide the caliper as it slides. More importantly, these ears are what actually react the braking loads from the pads into the spindle. These flat plate brackets don't have this feature, so all braking load gets reacted through the caliper pins. This is NOT what the pins were designed to do. Your brakes, your life, your choice.
The problem is that not all "12 inch rotors" nor all "single piston calipers" are the same. The stock disc brakes on the 67-70 full size cars used 12" diameter by 1.25" thick rotors. The 69-70 single piston calipers used 2.75" pistons - they are the same calipers as used on the half ton pickups. The Eldorado rotor mentioned above (which is the same part used on 69-78 Toros and Eldos) is only 11" diameter by 1.2" thick. Most of the aftermarket disc brake kits for these cars use the later metric calipers that only have 2.375" pistons. That's a 25% reduction in piston area and thus a 25% reduction in braking force for the same pedal pressure. Not my first choice. In converting my 67 Delta, I'm using the Wilwood D52 calipers that have two pistons and 10% more piston area than stock. And finally, my biggest concern on all aftermarket disc brake kits are the flat plate caliper brackets. Every single factory installation that uses sliding calipers has "ears" on the bracket that guide the caliper as it slides. More importantly, these ears are what actually react the braking loads from the pads into the spindle. These flat plate brackets don't have this feature, so all braking load gets reacted through the caliper pins. This is NOT what the pins were designed to do. Your brakes, your life, your choice.
The only other question I have is about Rotor size. Weren't those 69-78 Eldo's heavier than our 66s Olds? I would expect somehow GM got those cars to stop reasonably with those rotors and calipers. I am sure the 12" are better, but not sure if the 11" are completely inadequate.
I agree. The only difference I would say is that the caliper pins don't bear all the load. Actually the caliper sits inside the flat plate caliper bracket. So the load is not on the pins, it's actually on the 1/4" edge of the caliper bracket at that single point on the caliper. So it's still a concern, as factory caliper brackets spread the load across probably an inch and a half of cast iron on the bracket and on the caliper. Here the load is on 1/4" edge of the bracket. If I am right about the measurements (1.5in vs .25in), that's about 6x the point pressure on the caliper and bracket than stock.
I do have a question though. I am sure the 12" rotors are better than the 11". But aren't the 69-78 Eldos quite a bit heavier than our 66 Olds? I would think somehow GM got those to stop reasonably, with the 11" rotors. So I would think they 11"s may not be optimal, but perhaps they are adequate.
Last edited by sysmg; March 18th, 2019 at 07:10 AM.
Reason: left something out
I agree. The only difference I would say is that the caliper pins don't bear all the load. Actually the caliper sits inside the flat plate caliper bracket. So the load is not on the pins, it's actually on the 1/4" edge of the caliper bracket at that single point on the caliper. So it's still a concern, as factory caliper brackets spread the load across probably an inch and a half of cast iron on the bracket and on the caliper. Here the load is on 1/4" edge of the bracket. If I am right about the measurements (1.5in vs .25in), that's about 6x the point pressure on the caliper and bracket than stock.
Draw the free body diagram. The flat plate bracket reacts the load from the inboard pad, but what about the load on the outboard pad? That either has to go through the pins or it twists the caliper on the rotor. The latter is the more likely result, given that the pins bend and are mounted in rubber o-rings anyway.
I do have a question though. I am sure the 12" rotors are better than the 11". But aren't the 69-78 Eldos quite a bit heavier than our 66 Olds? I would think somehow GM got those to stop reasonably, with the 11" rotors. So I would think they 11"s may not be optimal, but perhaps they are adequate.
There are a lot of factors. Rotor diameter sets lever arm, but piston area and brake line pressure also have direct impacts on braking force. How do the master cylinder piston size and brake pedal lever arm compare?
Draw the free body diagram. The flat plate bracket reacts the load from the inboard pad, but what about the load on the outboard pad? That either has to go through the pins or it twists the caliper on the rotor. The latter is the more likely result, given that the pins bend and are mounted in rubber o-rings anyway.
Excellent analysis! The twisting would be significant and potentially cause brake lockup. Not to mention failure of the pins.
Originally Posted by joe_padavano
There are a lot of factors. Rotor diameter sets lever arm, but piston area and brake line pressure also have direct impacts on braking force. How do the master cylinder piston size and brake pedal lever arm compare?
Yup. Many variables that are not considered in the kits but were carefully taken into account by GM. I may be sticking with my drums.
Yup. Many variables that are not considered in the kits but were carefully taken into account by GM.
This is the thing that most people overlook. GM designed and tested the brakes on these cars to ensure operation under ALL conditions. Wet or dry. Vehicle empty or loaded. Pads new or worn. Brakes hot or cold. Gentle stopping or panic stop. Etc, etc, for a hundred thousand miles or more. I can guarantee that these aftermarket kits don't have a fraction of that amount of engineering and test.
In 1967, disc brakes were new-fangled technology that CHP "experts" didn't understand. Also keep in mind that in the 1960s, metallic brake shoes for drum brakes were a factory option on the police package that dramatically increased stopping power (at the expense of short brake drum life). Self-energizing drum brakes are a better choice when power brakes were still an option. Disc calipers do not self-energize, thus they require more pedal force for the same applied braking force. Also, on the full size cars in 1967, disc brakes required 15" wheels. I'm sure the CHP was still highly invested in 14" police tires.
The fact remains that as drum brakes heat up, the drum expands and moves AWAY from the shoes, causing brake fade. Rotors expand TOWARDS the pads as they heat up, increasing brake force. There's no comparison in the technologies. Just because a decision is made out of ignorance doesn't make it right.
In 1967, disc brakes were new-fangled technology that CHP "experts" didn't understand. Also keep in mind that in the 1960s, metallic brake shoes for drum brakes were a factory option on the police package that dramatically increased stopping power (at the expense of short brake drum life). Self-energizing drum brakes are a better choice when power brakes were still an option. Disc calipers do not self-energize, thus they require more pedal force for the same applied braking force. Also, on the full size cars in 1967, disc brakes required 15" wheels. I'm sure the CHP was still highly invested in 14" police tires.
The fact remains that as drum brakes heat up, the drum expands and moves AWAY from the shoes, causing brake fade. Rotors expand TOWARDS the pads as they heat up, increasing brake force. There's no comparison in the technologies. Just because a decision is made out of ignorance doesn't make it right.
Another factor in brake fade, is a closed drum's inability to shed heat. So the drum and shoes get so hot, that they have a hard time converting any more kinetic energy into heat. Also shoes coefficient of friction drop as they get hotter. Disc's have more swept area and the surfaces are open to the air, so shed heat more readily.
I have the full metallic drum brakes on my car now. They grab like all heck and never fade. Aside from the terrible wear on the drums, the other problem is they don't pull evenly. There is always one wheel locking before the others. Makes emergency stops squirrely. If I can switch to discs, it should make braking more predictable. I still would need to decide what type of brake pads to use (if there are any options). Stock compound or semi ceramic/metallic: something like Hawk HPS.
I hope I'm not too late to this thread. I just want to warn anyone NOT to buy from classicdiscbrakes.com. I ordered a full conversion for my '61 last year and I still haven't received all the parts. Every call to them just gets me more excuses. I'm at the point to where I'm just going to cut my losses and move forward with a different company like Scarebird.
March 20th, 2018, 08:16 AM
