jag brakes

[bava]

Am building a 3000 from bits! The car came with Jag three spot front calipers & jag rear calipers, all need rebuilding. I also have a Girling original servo booster. Question, would you go to a split system for brakes? if so what booster would work? Also do bj8 discs fit ok on early model hubs with the appropriate 31/2" mounting plates. Looking for a rally based car not concours.
Cheers, Bryn

 

[steveg]

I've seen Healey Factory-prepared cars that use your brake setup.

You would need BJ8 front hubs to accommodate the discs. They use bolts instead of studs.

I have a split system without booster with fiat 124/131 3/4" dual master cyl. and proportioning valve. IMO thru careful adjustment of the prop valve, you could use the booster on the front circuit only.

The Healey Factory could help you with this. They may sell the mounting plates. The UK suppliers do.

I have pix of a lot of this stuff at the link below.

 

[TFR1]

Am building a 3000 from bits! The car came with Jag three spot front calipers & jag rear calipers, all need rebuilding. I also have a Girling original servo booster. Question, would you go to a split system for brakes? if so what booster would work? Also do bj8 discs fit ok on early model hubs with the appropriate 31/2" mounting plates. Looking for a rally based car not concours.
Cheers, Bryn

Bryn,

Are you planning to put disc brakes on all 4 wheels?
I have a BN4 with disc brakes at all wheels.

I experimented with a booster but it really did not improve my braking. It did improve the pedal effort, but car took same distance to stop. Your results may be different.

FWIW, I believe front brakes on all Big Healey's from BN4 up to, but not including BJ8, are interchangeable. The uprights/spindles are the same so disc from one year will fit all.

If using Dunlop calipers, bolt spacing and offset will be different, but caliper mounts are available or can be easily made.

Good Luck

 

[John Turney]

Like Steve, I have a split system with four wheel disc brakes, proportioning valve and no booster on my BN4. My front calipers are Girling 16s so they fit BJ8 pads, but they appear to be from a TR6. The rears are Jaguar. The discs and mounting brackets came from Denis Welch and no modification or replacement of my hubs were required.

The front brakes on 3000s, except BJ8s are Girling 14s. On BJ8s, they are Girling 16s, with a different mounting bolt spacing. TRF1's Dunlop discs on his BN4 were a period, factory special order item, and not used on any other Healeys, except the 100S.

With the three-pot fronts, I doubt you would need a booster, since neither Steve or I use one. IIRC, Steve has three-pot Toyota calipers in front.

With Jaguar three-pot calipers, the first question is the mounting bolt spacing to determine a mounting bracket. If they fit your 3000, great. If not are they the same as a BJ8? If not, then custom brackets would be required, or find different calipers.

IIRC, Steve makes brackets for the rear Jaguar calipers.

Hope that helps.

 

[steveg]

Like Steve, I have a split system with four wheel disc brakes, proportioning valve and no booster on my BN4. My front calipers are Girling 16s so they fit BJ8 pads, but they appear to be from a TR6. The rears are Jaguar. The discs and mounting brackets came from Denis Welch and no modification or replacement of my hubs were required.

The front brakes on 3000s, except BJ8s are Girling 14s. On BJ8s, they are Girling 16s, with a different mounting bolt spacing. TRF1's Dunlop discs on his BN4 were a period, factory special order item, and not used on any other Healeys, except the 100S.

With the three-pot fronts, I doubt you would need a booster, since neither Steve or I use one. IIRC, Steve has three-pot Toyota calipers in front.

With Jaguar three-pot calipers, the first question is the mounting bolt spacing to determine a mounting bracket. If they fit your 3000, great. If not are they the same as a BJ8? If not, then custom brackets would be required, or find different calipers.

IIRC, Steve makes brackets for the rear Jaguar calipers.

Hope that helps.

John, thank you for the shoutout.

Slight correction - the Toyotas are 4-pot with 2 larger and 2 smaller pistons. Guessing this may cause a servo effect because I'm able to use a 3/4" MC with similar (or lighter) pedal pressure than with the std BN6 4-wheel drums.

DW and AHSpares (IIRC) make the brackets in both 3.25" and 3.5" bolt centers.

It should be added the BJ8 discs are 1/2" thick vs older 3/8" style. They and BJ8 hubs may be required for the 3-pot Jag calipers. IMO it's better to convert to these anyway as they're less likely to warp.

 

[red57]

Mine is pretty much the same but single circuit. I have the "replacement" calipers from Denis Welch (they are 16s but mount on the smaller/earlier bracket) and the jag rears. I have no servo and do not want one because the pedal pressure required is fine for me and modulating is easy, and I like the KISS method wherever possible. I also run R4 carbon Kevlar pads from Porterfield - the hotter they get, the better they work.
Dave

 

[TFR1]

I use EBC 'green stuff' pads with my BN4's Dunlop brakes. They significantly improved stopping power and are available here in the USA at Summit.

Much easier to change pads than add a booster.

tfr1

 

[BoyRacer]

I use the 3 pot jag calipers on my race car. They mount up directly to the BJ8 spindles, that have the mounting ears (unlike the early 3000s that have separate mounting brackets). These puppies are quite rare, But, I do have a pair that I am willing to sell. Send me a private message if interested.

 

[steveg]

FWIW - whether they're reamed to fit the kingpins is a consideration in the purchase of spindles.

 

[steveg]

Bryn - if you do establish that the BJ8 thicker discs can be used with the older hubs, please let us know.

 

[red57]

steveg - It depends on the calipers used - I run the BJ8 1/2" rotors on the earlier hubs and use the Denis Welch "replacement" calipers and the 1/2" rotors clear with some very minor clearance trimming to the caliper body.
I did that to hopefully extend brake life while racing but it didn't help much.

I would never give up the 3/8" rotors for a street driven car - they are a much lighter 'unsprung weight' and much less rotational mass. The 1/2" rotors give a heavier steering feel much like going from 185 tires to 205 tires and you aren't gaining anything.
If you can lock-up the tires and modulate that breaking, then you don't need more brakes - you are already at the limit of tire adhesion.... and no kind of street driving will make hot brakes like track use does.

On the subject of hot brakes, another element to this is 'warped' rotors. Over 15 years of racing I have never had a warped rotor. I have had a lumpy vibration from the brakes and what I always found was pad material transfer (welding) onto the rotors leaving a variable thickness. The rotors started at .375 and are now as much as .380 or so but uneven so there is chatter as you brake and we tend to think this is a warped rotor and that is why we want thicker rotors, to combat the warpage (that is not really warpage).

My experiences and opinions - YMMV.
Dave

 

[elrey]

A very good point as to rotational mass and unsprung weight. I heretofore had never equated pad transfer with chattering. Keep spreading your welcome breadth of knowledge with the rest of us. Informative and fascinating. All of you bright folks make BCF the best forum on the net. Thanks again.

 

[Bob_Spidell]

... On the subject of hot brakes, another element to this is 'warped' rotors. Over 15 years of racing I have never had a warped rotor. I have had a lumpy vibration from the brakes and what I always found was pad material transfer (welding) onto the rotors leaving a variable thickness. The rotors started at .375 and are now as much as .380 or so but uneven so there is chatter as you brake and we tend to think this is a warped rotor and that is why we want thicker rotors, to combat the warpage (that is not really warpage).

My experiences and opinions - YMMV.
Dave

Not just your opinion:

https://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

 

[HealeyRick]

Somewhere in this discussion, I think the question was asked whether the BJ8 discs will work on the earlier spindles. Here are BJ8 discs on my BJ7 from an ill-fated attempt to use M16 calipers from an early '70s Mercury Capri. which have the correct lug spacing to fit on the earlier cars. Everything worked out ok until I fit my 72 spoke wheels, which rubbed on the calipers. So if you're doing a front brake swap, the later discs will fit although you will need a caliper that has sufficient width that will clear the later disc. IIRC, the earlier calipers are too narrow between the pads to allow the later disc to fit.

 

[steveg]

steveg - It depends on the calipers used - I run the BJ8 1/2" rotors on the earlier hubs and use the Denis Welch "replacement" calipers and the 1/2" rotors clear with some very minor clearance trimming to the caliper body.
I did that to hopefully extend brake life while racing but it didn't help much.

I would never give up the 3/8" rotors for a street driven car - they are a much lighter 'unsprung weight' and much less rotational mass. The 1/2" rotors give a heavier steering feel much like going from 185 tires to 205 tires and you aren't gaining anything.
If you can lock-up the tires and modulate that breaking, then you don't need more brakes - you are already at the limit of tire adhesion.... and no kind of street driving will make hot brakes like track use does.

On the subject of hot brakes, another element to this is 'warped' rotors. Over 15 years of racing I have never had a warped rotor. I have had a lumpy vibration from the brakes and what I always found was pad material transfer (welding) onto the rotors leaving a variable thickness. The rotors started at .375 and are now as much as .380 or so but uneven so there is chatter as you brake and we tend to think this is a warped rotor and that is why we want thicker rotors, to combat the warpage (that is not really warpage).

My experiences and opinions - YMMV.
Dave

Dave, thank you for the correction! So, is it OK to run the thinner rotors with the wider calipers? - the pistons would protrude 1/16" further on either side of the rotor.

 

[red57]

@HealeyRick, I think you are right - if I remember correctly the earlier calipers are too narrow to insert the 1/2" disc. And you raised another point with your wheel not clearing, I never thought about that earlier when I was posting - I have bolt-on wheels, I quit the spokes 20 years ago and never looked back - too high a maintenance for me when racing...all it takes is one broken spoke and you will not pass tech, therefore you will not have fun.

@steveg, When I first bought the "replacement" calipers from Denis Welch about 20 years ago, they were selling them as replacements for the 'stock' early disc set-up so I would guess there are lots of them running around with the thinner rotors, I did for at least 10 years. I never learned what the "replacement calipers" are from. Side note: I did have to shim my calipers at the mounts a bit to get the caliper seam centered on the disc (iirc about 1/8" but not certain)
Dave

 

[HealeyRick]

@HealeyRick, I think you are right - if I remember correctly the earlier calipers are too narrow to insert the 1/2" disc. And you raised another point with your wheel not clearing, I never thought about that earlier when I was posting - I have bolt-on wheels, I quit the spokes 20 years ago and never looked back - too high a maintenance for me when racing...all it takes is one broken spoke and you will not pass tech, therefore you will not have fun.


Dave

Yes, the person who had posted online about this swap was using minilite style wheels and did not have the fouling problem. My spokes were hitting on the outside edge of the caliper by a tiny amount, sort of like when we put baseball cards in our bikes. Not sure if 60 spoke wheels would work. Still have the BJ8 discs put away awaiting doing Steve's Toyota swap, that is if he thinks it's a worthwhile upgrade without going to rear discs as well.

 

[John Turney]

@HealeyRick, I think you are right - if I remember correctly the earlier calipers are too narrow to insert the 1/2" disc. And you raised another point with your wheel not clearing, I never thought about that earlier when I was posting - I have bolt-on wheels, I quit the spokes 20 years ago and never looked back - too high a maintenance for me when racing...all it takes is one broken spoke and you will not pass tech, therefore you will not have fun.

@steveg, When I first bought the "replacement" calipers from Denis Welch about 20 years ago, they were selling them as replacements for the 'stock' early disc set-up so I would guess there are lots of them running around with the thinner rotors, I did for at least 10 years. I never learned what the "replacement calipers" are from. Side note: I did have to shim my calipers at the mounts a bit to get the caliper seam centered on the disc (iirc about 1/8" but not certain)
Dave

The Denis Welch calipers that I bought about 20 years ago seem to be from a TR6, at least they take a TR6 rebuild kit. The slot for the rotor is 21/32".

 

[steveg]

The Denis Welch calipers that I bought about 20 years ago seem to be from a TR6, at least they take a TR6 rebuild kit. The slot for the rotor is 21/32".

I've heard TR6, too. My Healey friend Peter Roses is running the DW kit, which came with the thinner rotors (as well as my rear kit). He had to use the 5/8" MC from the Mk I 3000s to get acceptable pedal pressure, as the 3/4" wouldn't work with the Type 16s -- at least with the pads we tried (Moss Ceramic/Centric Ceramic).

PS - he had no clearance problem on the 72-spoke Daytons. Maybe because both of us started with the (IIRC TR6) Daytons which originally cleared our front drums. A couple of grade 8 washers centered the calipers on the rotors.

 

[bava]

Thanks everone for their various bits of advice.
As the car is still very much in bits I will let you know on progress but from the advice so far it seems
BJ8 rotors will fit earlier hubs
The jag calipers take 1/2" rotors
Probably does not need a booster
Split system just for safety reasons
I am hoping to get a pair of BJ8 rotors of a mate who put new ones on so will use these to try out the fitment
Will keep you posted!
Cheers
Bryn