How to improve Park Brake Performance with Dr Diff Rear Wheel Disc Conversion?

[Cal Tonsley]

Hi All
I’ve converted my Aus Valiant Hardtop (69 Dart) with 8 3/4” to rear wheel discs using the Dr Diff Mopar 10.7" Rear Disc Brake Kit
While braking performance has been track tested and is very good, I need to improve the effectiveness of the park brake in order to pass my roadworthy inspection. I find that the park brake holds the vehicle somewhat satisfactorily with the rear of the vehicle facing downhill but it is hard pressed holding the vehicle on an incline when the front of the vehicle is facing downhill. I have done a fair bit of searching regarding adjustment methods and optimisation but am still looking for some advice. Apart from cable adjustment, the only other tip I found for these Cobra calipers is to apply and release the handbrake 20-25 times and then apply the foot brake. I have done this once but found little in the way of improvement. I have adjusted the cable to where there is a little drag in the released position and I can only pull the park brake out 3-4 clicks. With the foot brakes applied I can pull out the park brake another 4-5 clicks but still the performance of the brake is marginal on anything but a level road.
Can anyone please advise any other tips regarding adjustment of the park brake using the Dr Diff kit in order to maximize park brake holding power?

Thanks in advance!

 

[Bewy]

Leverage my boy, leverage. You need to find some way of increasing the mechanical advantage.

 

[Cal Tonsley]

Leverage my boy, leverage. You need to find some way of increasing the mechanical advantage.

True, problem is that the pivot is fixed on the caliper so I guess I might just have to tug harder on the handbrake lever

 

[72bluNblu]

Hi All
I’ve converted my Aus Valiant Hardtop (69 Dart) with 8 3/4” to rear wheel discs using the Dr Diff Mopar 10.7" Rear Disc Brake Kit
While braking performance has been track tested and is very good, I need to improve the effectiveness of the park brake in order to pass my roadworthy inspection. I find that the park brake holds the vehicle somewhat satisfactorily with the rear of the vehicle facing downhill but it is hard pressed holding the vehicle on an incline when the front of the vehicle is facing downhill. I have done a fair bit of searching regarding adjustment methods and optimisation but am still looking for some advice. Apart from cable adjustment, the only other tip I found for these Cobra calipers is to apply and release the handbrake 20-25 times and then apply the foot brake. I have done this once but found little in the way of improvement. I have adjusted the cable to where there is a little drag in the released position and I can only pull the park brake out 3-4 clicks. With the foot brakes applied I can pull out the park brake another 4-5 clicks but still the performance of the brake is marginal on anything but a level road.
Can anyone please advise any other tips regarding adjustment of the park brake using the Dr Diff kit in order to maximize park brake holding power?

Thanks in advance!

View attachment 1716342328

View attachment 1716342329

I run DoctorDiff's 11.7" rear disk kit on my Duster and haven't had any issues with the parking brake holding the car on a hill in either direction, my driveway is fairly steep so it has definitely been parked on a hill.

How many miles are on the rotors and pads at this point? Is the picture of the rotor you posted the current condition or just a picture from when you first installed them?

I tested my car and found the number of "clicks" pretty hard to count accurately, can you take a picture of the lever with the park brake fully applied? Or maybe count the number of ridges visible on the park brake lever when it's fully applied?

 

[Cal Tonsley]

I run DoctorDiff's 11.7" rear disk kit on my Duster and haven't had any issues with the parking brake holding the car on a hill in either direction, my driveway is fairly steep so it has definitely been parked on a hill.

How many miles are on the rotors and pads at this point? Is the picture of the rotor you posted the current condition or just a picture from when you first installed them?

I tested my car and found the number of "clicks" pretty hard to count accurately, can you take a picture of the lever with the park brake fully applied? Or maybe count the number of ridges visible on the park brake lever when it's fully applied?

Only about 60 miles on the discs!
With it applied as hard as i dare there’s 3 ridges past the upper mount (see photo)- this is 10 clicks in total which may be one or two more clicks than I previously tested it at! I might test it again tomorrow to see if that helps.

 

[72bluNblu]

Only about 60 miles on the discs!
With it applied as hard as i dare there’s 3 ridges past the upper mount (see photo)- this is 10 clicks in total which may be one or two more clicks than I previously tested it at! I might test it again tomorrow to see if that helps.

View attachment 1716342355

Hmm, ok. When fully applied on my car I'm usually pulling 5 ridges clear of the upper mount.

60 miles should be more than enough for the pads to be bedded in, so that shouldn't be an issue. Is the picture of the rotor you posted earlier before the 60 miles?

 

[Cal Tonsley]

I run DoctorDiff's 11.7" rear disk kit on my Duster and haven't had any issues with the parking brake holding the car on a hill in either direction, my driveway is fairly steep so it has definitely been parked on a hill.

How many miles are on the rotors and pads at this point? Is the picture of the rotor you posted the current condition or just a picture from when you first installed them?

I tested my car and found the number of "clicks" pretty hard to count accurately, can you take a picture of the lever with the park brake fully applied? Or maybe count the number of ridges visible on the park brake lever when it's fully applied?

Hmm, ok. When fully applied on my car I'm usually pulling 5 ridges clear of the upper mount.

60 miles should be more than enough for the pads to be bedded in, so that shouldn't be an issue. Is the picture of the rotor you posted earlier before the 60 miles?

Yes it would have been at about 45 and just before the track day tests. Having said that any meaningful brake bedding in work would have only been during the last 15 miles as the first 20 or so miles would have been spent on a chassis dyno!

 

[MV8]

Lube the slide pins, cables, equalizer, and hand brake. Clean the pads and rotors. Scuff the rotors. Support both the rear wheels off the ground, have someone apply the brake pedal and check for rotating resistance on each wheel, then set the parking brake, hands on the tire or a lug wrench to compare effort from side to side and equalize. Look at the arm on the calipers to see if they are rotated the same and have not run out of travel/hit the stop.

Caliper type parking brakes do not hold very well compared to drums. Larger cars typically have a small drum in the rotor just for parking.

 

[Dana67Dart]

I had Ford rear disk back in the day.

The parking brake had a self adjuster that had to be turned back in on a pad change. To do that you had to remove the lever on the caliper, turn the piston with a special wrench then put the lever back on.

I don't know the dr diff brake parts but if it uses the caliper to press the pads then there might be more adjusting you need to do. If it has separate drum shoes inside the center of the disk rotor check for pad alignment and adjustment


You mentioned you could press the foot brake and get a few more clicks out of the parking brake. That suggests to me the adjustment is the issue

 

[72bluNblu]

Yes it would have been at about 45 and just before the track day tests. Having said that any meaningful brake bedding in work would have only been during the last 15 miles as the first 20 or so miles would have been spent on a chassis dyno!

Ok, because in that picture it looks like the rear brakes are barely doing anything, you can still see the original rotor texture and after bedding in that should be entirely gone where the pads ride.

I had Ford rear disk back in the day.

The parking brake had a self adjuster that had to be turned back in on a pad change. To do that you had to remove the lever on the caliper, turn the piston with a special wrench then put the lever back on.

I don't know the dr diff brake parts but if it uses the caliper to press the pads then there might be more adjusting you need to do. If it has separate drum shoes inside the center of the disk rotor check for pad alignment and adjustment


You mentioned you could press the foot brake and get a few more clicks out of the parking brake. That suggests to me the adjustment is the issue

The 10.7’s are a Mustang cobra caliper, the parking brake uses the caliper there’s no separate pads or drum.

I thought the same thing about being able to get a few more clicks when the brake pedal is depressed, but honestly when I tried setting the parking brake with my feet on the floor I realized I had much better leverage to pull the handle when I was stepping on the brake. And I’m pretty much always stepping on the pedal when setting the parking brake so the difference didn’t occur to me. Not saying there can’t also be an adjustment issue but there’s definitely a leverage difference.

 

[Cal Tonsley]

Ok, because in that picture it looks like the rear brakes are barely doing anything, you can still see the original rotor texture and after bedding in that should be entirely gone where the pads ride.



The 10.7’s are a Mustang cobra caliper, the parking brake uses the caliper there’s no separate pads or drum.

I thought the same thing about being able to get a few more clicks when the brake pedal is depressed, but honestly when I tried setting the parking brake with my feet on the floor I realized I had much better leverage to pull the handle when I was stepping on the brake. And I’m pretty much always stepping on the pedal when setting the parking brake so the difference didn’t occur to me. Not saying there can’t also be an adjustment issue but there’s definitely a leverage difference.

Thanks for the updates, really appreciate your input.
I’ll do some more testing today and will aim to extend the handbrake lever as far as possible in the process!