410, 411, 412 servos

[dwomby]

I fitted a 4.25x boost brake servo (Lockheed LR18230) to the front brakes and left the 1.9x servo on the rear brakes. After days of fiddling to stop a fluid leak at the caliper, I finally put it back on the road today and took a VERY slow drive down the street to test the brakes still worked at all! It seemed ok so I took it for 30 minutes on the back roads.

The new servo for the front brakes gives over twice the boost the old one did and it really makes a huge difference. The pedal effort to stop the car is now similar to our modern Mazda and the stopping power is impressive for a car of this vintage and weight.. I'm really glad I made that change.

David

[Geoff Dowdle]

David,
When you have confidence in the brakes I suggest you take the car out on a quiet country road at say 60 mph and when safe do an emergency stop .
You might find the front brakes might lock up!!!!!!!!!!!!

BCL would have done a lot of testing of Servos in conjunction with Lockheed for more than 10 years to decide on the original servos of the 410.

Geoff

[dwomby]

Originally Posted by Geoff Dowdle

David,
When you have confidence in the brakes I suggest you take the car out on a quiet country road at say 60 mph and when safe do an emergency stop .
You might find the front brakes might lock up!!!!!!!!!!!!

BCL would have done a lot of testing of Servos in conjunction with Lockheed for more than 10 years to decide on the original servos of the 410.

Geoff

Thank you for that, Geoff. I did try that yesterday on dry, straight road. I am pretty sure all 4 locked up. The car stayed pretty much straight throughout but one pair left darker rubber lines than the others and appear to have started further back along the road.

I do not know how to tell if one pair locked before the other. How do you know if front or rears locked first? I am guessing the darker line was the fronts as they carry a lot more weight in a hard stop and that line started further back (about 3 yards before the lighter lines appeared) but does that mean they locked first?

Any advice, please?

David

[Geoff Dowdle]

David ,
I'm certainly not a brake expert/engineer but I would not want brakes on my Bristols to lock on a dry road .
Imagine what would happen on a wet road if you had to brake suddenly while going through a corner . It could be a disaster .

Years ago I had a 411S1 with standard brakes in good condition . They worked very well for normal road use . Pressing the pedal half way gave average to good braking, then pressing harder really pulled the car up , with no fuss or lockup.
It gave good feel and was not over assisted.

Drive carefully !!!!!!!!!

Geoff

[Kevin H]

I had a 3.0 Si BMW on which I could lock up the wheels on a dry road - it happened on the Finchley Rd in London and I skidded into the back of a Porsche!


I'm sure I've had other cars with standard brakes on which I could lock up the wheels on a dry road.