Brake Caliper Upgrade

[Bob_Spidell]

You're welcome, Steve. Glad to be able to pass it along.

 

[RAC68]

Hi All,

OK, I appreciate that you are discussing the new calipers but no one has answered the question of what was the issues with the original 2 piston brakes with cintered metalic pads? Other then a conversion from drums, why would you change the front calipers to the 4 piston version in a car not used for racing? I would be more incline to install rear disks then change the original front calipers that I have found more then adequate for the past 54 years and only 1 rebuild. I use silicone brake fluid and have had very good performance.

I would expect this choice to be of interest to a limited group of Healey owners but are not a selection of general necessity/need. Am I correct in my thought?

Ray(64BJ8P1)

 

[Bob_Spidell]

...
I would expect this choice to be of interest to a limited group of Healey owners but are not a selection of general necessity/need. Am I correct in my thought?

I think so (though I have no problem with owners upgrading their cars). FWIW, I've put over 140K miles on my BJ8 in (mostly) cross-county driving in all conditions and never felt like the brakes were inadequate. When I get a chance, I'll drive the car hard, but not push the limits much on a 53 year-old car, which certainly has not gotten better with time and wear (and rust). My BN2, however, is a different story: the 4-wheel drums do not inspire confidence and I drive it accordingly (it's also worth a lot more than the 3000). The drums show noticeable fade.

I learned to drive on a Model A with mechanical drum brakes, and habitually do not depend on my brakes to save my bacon if I'm inattentive or reckless (my Mustang's brakes are going on 134K miles with the original pads). If your brakes are sufficient to lock up the wheels, the rest is up to the tires anyway.

 

[HealeyRick]

Hi All,

OK, I appreciate that you are discussing the new calipers but no one has answered the question of what was the issues with the original 2 piston brakes with cintered metalic pads? Other then a conversion from drums, why would you change the front calipers to the 4 piston version in a car not used for racing? I would be more incline to install rear disks then change the original front calipers that I have found more then adequate for the past 54 years and only 1 rebuild. I use silicone brake fluid and have had very good performance.

I would expect this choice to be of interest to a limited group of Healey owners but are not a selection of general necessity/need. Am I correct in my thought?

Ray(64BJ8P1)

Ray,

I have a 345hp V8 with BJ7 brakes and I autox on occasion. Even the factory went to bigger pad area when they switched from Girling 14 calipers in the BJ7 to Girling 16 calipers in the BJ8. Although my brakes are adequate for street use, they could be better for autox. Using the Toyota calipers will allow me to use the vented/slotted discs from Moss that only fit BJ8 calipers that have a wider spacing between the pistons than the BJ7 calipers. The Toyota calipers have the same spacing.

 

[RAC68]

Rick,

For those with the HP you have, I can understand larger brakes and even 4-wheel Disks. However, for the 6-cylinder Healey with even a more reasonable HP increase, the standard BJ7/8-phase 1 setup should be sufficient...it has been for me.

Ray(64BJ8P1)

 

[dougie]

I had interference issues with my hard line at full lock. It took me three iterations to get mine correct. See: https://www.pbase.com/stevegerow/healey_discs

You might want to remove the spring and move the suspension up and down at full lock to make sure the hard line isn't hitting the shock tower.

Much easier using stainless flex hoses.

 

[Legal Bill]

I'll have to assume that these calipers will reduce stopping distances in all cars. SO while I may not buy them, I can certainly understand that some in bone stock cars would like to reduce their chances of crashing. Emergency stopping circumstances occur and a 30, 20, and even 10 foot reduction in stopping distance can make all the difference.

 

[steveg]

Much easier using stainless flex hoses.

Great stuff - links?

 

[Jack T]

I have to chime in here. Going to a larger (bigger bore) master cylinder will not reduce pedal pressure.... it will do the opposite ..... it will increase your pedal pressure. This may seem counter-intuitive to some but it is true.

Hmm, now that caught my attention. My 'restorer' installed a 7/8" MC in my BT7 without a servo. I did not like the pedal effort nor the pedal travel so I installed a booster. That helped the effort a little, but the pedal travel is still longer than I like. Would going to the standard 5/8" MC reduce pedal travel? I do have the stock BT7 calipers.

Thanks.

 

[HealeyRick]

I have to chime in here. Going to a larger (bigger bore) master cylinder will not reduce pedal pressure.... it will do the opposite ..... it will increase your pedal pressure. This may seem counter-intuitive to some but it is true.

Hmm, now that caught my attention. My 'restorer' installed a 7/8" MC in my BT7 without a servo. I did not like the pedal effort nor the pedal travel so I installed a booster. That helped the effort a little, but the pedal travel is still longer than I like. Would going to the standard 5/8" MC reduce pedal travel? I do have the stock BT7 calipers.

Thanks.

I

No, just the opposite. A smaller master bore size will increase pedal travel. You might check if you have an adjustable clevis that attaches to the brake pedal that could change your brake travel.

 

[RAC68]

Hi Guys,

As I see MC travel and going back to basics, the purpose of the MC is to fill and apply pressure to the wheel brake cylinders. Since a higher pressure can be applied by a smaller diameter MC per unit of peddle pressure when fluid fully fills all brake lines and fully extended slave cylinders. Supplying a sufficient amount of fluid to achieve this fill per unit of time and peddle travel is better done if the bore of the MC is larger. So, as I see it, a balance must be satisfied to use a MC bore that is Large enough to satisfy a quick and sufficient fill of brakes and lines and that is Small enough to apply the greatest amount of pressure.

Where a great amount of fluid movement is required per unit of peddle travel and a large bore MC used to satisfy that factor, a Brake Booster was employed to supply a differential amount of pressure to help maintain the same amount of foot pressure. So, when considering going from 2 piston to 4 piston calipers and/or rear calipers, it is assumed that a greater volume of fluid movement would be required per unit of peddle travel and opting for a larger MC bore would seem to be required. If this holds true and the same amount of brake pad pressure required at the SC, an increase in foot pressure or booster assist required.

Last, stopping efficiency differs between drum and disk brakes with disk brakes providing more stopping power. Additionally, rear brakes hold an opposite application profile then front brakes with the rear brakes coming on first and the front brakes taking over. For rear disk brakes, rear pads have a different composition then fronts to satisfy this profile where rear drums naturally satisfy this profile. I bring this up because required peddle pressure will be increased on hard stops where an inefficient compound or a mismatched pad/shoe profile is implemented in the braking system.

This is where it would be nice to have a number of MCs at different bores and a number of boosters available to experiment, but for most making these changes, we would simply rely on one of the already used MCs to a (usually) less then optimum result...but who knows for sure. I would assume that their is a formula used by the brake system manufacturers that could be used to calculate all these factors to come up with a good choice but I have no idea and wonder if others do.

So, when reading Jack's and Rick's seemingly diametrically apposed posts, consider the full picture and what is required to stop the car.

Just my thoughts,
Ray(64BJ8P1)

 

[steveg]

Stock BT7 (no servo) is supposed to have a 5/8" master cyl. with rear brake cylinders that are smaller-bore than the previous drum items.

If your "restorer" installed the larger cylinders, that would also contribute to pedal travel. Moss tech support could probably tell you the proper bore.

Make sure your rear brakes are adjusted to remove extra pedal travel.

Also check the holes where your clevis fork pins to the pedal arm - if they're elongated, suggest getting an adjustable clevis & rod from, say, Pegasus auto racing.

 

[Magnus Karlsson]

The type 16 metric caliper you have were used on European Fords in the early seventiees, like Escorts and Granadas.

 

[Jack T]

I

No, just the opposite. A smaller master bore size will increase pedal travel. You might check if you have an adjustable clevis that attaches to the brake pedal that could change your brake travel.

Yeah, i just did the contortionist routine and wound the yoke on the mc rod out about 3/8". Feels much better after a short drive, will see how it does on a longer trip through the mountains.

 

[HealeyRick]

Proof of concept:

Using the Denis Welch Racing caliper brackets with 3.5" spacing on the ears on the original BJ7 spindle will allow use of the Toyota 4-pot calipers and BJ8 slotted, vented discs.

Total price of the Moss BJ8 upgrade is $805, plus you would have to add $160 plus shipping for the DWR brackets.

I already had the drilled rotors {$190} and caliper brackets ($160) and bought the loaded Toyota calipers from Amazon - $180 , and $16 for the TR6 caliper mounting bolets - so saved a considerable amount over the Moss kit.

The installation isn't complete yet, I need to make up the hard brake line between the caliper and braided stainless line per Steve Gerow's instructions. It looks to me like British Car Specialists are now carrying the caliper brackets: https://www.britishcarspecialists.c...e/index.php?category=BRAKES&subcategory=FRONT and TS Imports carries steel braided lines from the calipers for the TR6 that look like they might work. https://www.tsimportedautomotive.com/tr250_tr6.html I haven't verified these parts, so check them out before you purchase.

 

[Bob_Spidell]

Did the BJ7 have the smaller, (allegedly) weaker axles?

 

[HealeyRick]

Did the BJ7 have the smaller, (allegedly) weaker axles?

Yes, although I have a new Denis Welch spindle on one side that replaced a bad axle, so I'm 50% stronger.

 

[steveg]

The Moss ss lines and fittings work fine. You don't need to look at a tr 6 line.

 

[HealeyRick]

The Moss ss lines and fittings work fine. You don't need to look at a tr 6 line.

Steve,

I'm talking about the braided lines that Moss sells as part of their kit and leads directly from the caliper. I didn't think Moss sold those separately, but it looks like TSI does a similar looking line for their TR6 Toyota conversion.

 

[CraigC]

Rick, what material were the caliper mounting brackets? I asked them some time back and was told they're "as per original" which did not answer my question.