[Healeys] Rear wheel cylinders on a BJ8

Wed Aug 28 07:29:54 MDT 2019

Ok. At the risk of getting flamed by more armchair warriors, I’ll have a pop at a reply.

‘BlueHealey’ is my carefully modified and upgraded 100/6. When first built and restored it had the original drum brakes and 7/8” rear wheel cylinders. All very standard.  After a few years I decided to upgrade to discs at the front. This was driven by the need for more effective bite and control of the brakes in modern traffic conditions. The drums just didn’t inspire confidence.
Jeremy Welch (DenisWelch Motorsport) can supply a disc brake kit with Calipers the same size as BJ8 (M16), but a bolt pattern that fits the adaptor for the early uprights.  It all bolts up a treat. The bonus is that the original 3/4” Master Cylinder works well with the big Calipers.  No servo needed and pedal travel is only slightly longer then previously.
The armchair surfer in me worried that the pedal travel might be too great and that 7/8” Master and Servo might be a phase two requirement. It wasn’t.

Then came the road test. Brakes felt good despite being new and I set off to put some heat cycles into the pads with steadily harder stops being applied.  You guessed it - I could lock the rears much sooner than I was happy with.  Good solid, hard braking on dry roads appeared to lighten the rear end and one or other of the rears would chirrup and skid.
I reduced the rear cylinders to 3/4” and the problem was gone.  By the time I got the rears to smoke the fronts were letting go too.

It is a good set up, certainly as good as my previous BJ8 but the servo isn’t needed.
Alan Bromfield
Bluehealey.com

Alan - from my iPad

> On 28 Aug 2019, at 12:23, Chris Dimmock <austin.healey at gmail.com> wrote:
> 
> Seriously, 
> So all you men who have fitted rear disc brakes to your Healey, have only ever done this in order to "reduce" your rear braking effort?
> To make your rear brakes "less efficient" than they already are?
> And you've fitted Discs to "increase" your unsprung weight, and upset the balance of your car?
> Seriously?
> Sincerely, this group used to share ideas. 
> Now, instead of people saying "nah, tried that, but I locked rear wheels" it's a bunch of hypothetical Wikipedia answers. 
> So I will ask again. 
> Has anyone else changed their rear wheel cylinders on a 3000 from 3/4 inch to 7/8 inch?
> If yes - I'd love to hear your feedback. 
> If you've fitted disk brakes on your Jensen Healey, or what ever - I'm not interested in your comments. Im not interested in the theory - I'm interested in the practice and real results from on the road. 
> Too much bullshit internet "searching" is infiltrating this list. I've always only answered when I've actually done something. 
> Armchair experts who google answers and Have now experience in the question I've asked need to pull their head in - that's you Kees. 
>>> Has anyone else ever changed their rear wheel cylinders from 3/4 inch to 7/8 inch?
> If you have? I'd love to hear from you. 
> If you haven't, well, I don't really care!
> Yes. I'm pissed off. 
> People who have the answer - from experience- don't answer when 4 others respond. 
> I'm just pissed off 
> A lot going on. 
> Chris
> 
> On 28 Aug 2019, at 2:29 am, Michael Salter <michaelsalter at gmail.com> wrote:
> 
>> Have to agree with Kees on this one. 
>> We have a brake bias control on AHX12 and I can certainly attest to the fact that when the conditions change to "wet" removing a lot of rear braking is absolutely essential to prevent the car from swapping ends. 
>> As most road cars don't have adjustable brake bias I would be very careful in trying to increase the rear braking.
>> When braking into a corner the last thing you want is the rear end coming around, particularly in the wet.
>> 
>> M
>> 
>>> On Tue, Aug 27, 2019 at 12:09 PM Kees Oudesluijs <coudesluijs at chello.nl> wrote:
>>> Whatch out driving in the rain as the rear brakes will lock the rear 
>>> wheels much quicker than with the smaller pistons.Rear brakes are only 
>>> providing a small portion of the total brake force.
>>> 
>>> Kees Oudesluijs
>>> 
>>> Op 27-8-2019 om 18:04 schreef Chris Dimmock:
>>> > Hi Men
>>> > 
>>> > I just did. Sick of the rear brakes doing nothing. Freeloaders!!
>>> > Yes, no problem with seized wheel cylinders, no problem with the flexible hose - just bugger all wear on the rear linings.
>>> > I'll let you know how it goes on my BJ8
>>> > Best
>>> > Chris
>>> >
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