Modifying the Brake Booster Reaction Disc?

[260DET]

When my 280ZXT hybridz was first built the booster had been reconditioned but no reaction disc fitted. Consequently it was impossible to modulate the brakes but when braking at high speed the car stopped in a very short distance, it does have a big brake upgrade. Since then a reaction disc has been fitted and the brakes behave and work prefectly, except that no matter how hard the pedal is pushed at high speed the stopping distance although good is not as good as it was without the disc.

 

So I'm wondering if it would be possible to get more boost with high pedal pressure to regain that original stopping performance without losing any of the present modulation quality.

[hoov100]

Would a billet aluminum disk in the same dimensions as the OE rubber disk work? I have never really been a fan of brake booster setups and usually opt to connect the M/C directly to the brake pedal. But I don't think you can do that down there and still pass inspection.

[260DET]

Hoping someone will have 'been there done that', otherwise I'm going to have to pull a spare booster to bits and work out how the reaction disc functions

[johnc]

Hoping someone will have 'been there done that', otherwise I'm going to have to pull a spare booster to bits and work out how the reaction disc functions

 

The reaction disc acts like a bump stop in the suspension. You should be able to experiment with various durometers of rubber and/or urethane to get the feel you want. You can also glue two different durometers of material together to give a soft initial touch and then a harder touch as more pressure is applied.

[260DET]

Thanks John, the harder the disc material the more boost assistance I assume.

[johnc]

Thanks John, the harder the disc material the more boost assistance I assume.

 

Not really. You get the same amount of boost assistance and pressure applied to the MC (the equal and opposite reaction thing). What you can change with the reaction disc is pedal feel, travel, and the rate of pressure application.

[fhptom]

Would a billet aluminum disk in the same dimensions as the OE rubber disk work? I have never really been a fan of brake booster setups and usually opt to connect the M/C directly to the brake pedal. But I don't think you can do that down there and still pass inspection.

 

Hoov100, have you done this with the stock M/C or just after market ones like Wilwood or Tilton. I am not happy with not knowing which pedal feel I am going to have when I do track events. Or would this even affect the feel. I run Wilwood calipers F/R with stock m/c.

 

Tom

[260DET]

Not really. You get the same amount of boost assistance and pressure applied to the MC (the equal and opposite reaction thing). What you can change with the reaction disc is pedal feel, travel, and the rate of pressure application.

 

Interesting. The difference I experienced on the track was quite remarkable, brakes were basically either on of off. When on the car would stop in about half the distance it does with a reaction disc fitted but the rate of braking was uncontrollable.

[hoov100]

Would a billet aluminum disk in the same dimensions as the OE rubber disk work? I have never really been a fan of brake booster setups and usually opt to connect the M/C directly to the brake pedal. But I don't think you can do that down there and still pass inspection.

 

Hoov100, have you done this with the stock M/C or just after market ones like Wilwood or Tilton. I am not happy with not knowing which pedal feel I am going to have when I do track events. Or would this even affect the feel. I run Wilwood calipers F/R with stock m/c.

 

Tom

 

I have only done it with stock car brake setups using stock M/C's, I had my 240z setup like that before I got my wilwood pedals and I ran my z32 without a booster. IMHO I love the feel of not having a booster in between the M/C and pedal. My current auto-x car ran a tilton M/C's for 15 years on the street before they sold the car to us and the brakes feel bitchin' even with 10 inch tires.

[fhptom]

Do you happen to have any pics of the setup without the booster. Did you have to fab up some type of mounting plate.

 

Tom

[260DET]

What may have happened with mine initially is, because the reaction disc was missing, a misalignment changed the amount of boost effort that was being applied. So, while the reaction disc itself does not change the amount of ultimate boost effort its absence results in that happening. Anyway thats the present theory, I'll strip a spare booster sometime and have a look.

 

On the subject of using twin master cylinders instead of the OE booster setup, for a road car in NannystateAU it would be just another thing requiring approval to be road legal. But unless you are going to run high friction race brake pads I'm not sure that they would be able to provide sufficient braking effort for something which is not a lightweight race car.

[Cannonball89]

I thought about doing that once. I even posted a thread about it: http://forums.hybridz.org/index.php/topic/88518-solid-reaction-disk/page__p__840639__hl__%2Bsolid+%2Breaction+%2Bdisk__fromsearch__1#entry840639

 

I decided it would be a dumb idea... but experimenting with different stiffness's of rubber sounds interesting. But at the end of the day you are only changing the feel. If I can find three or four blocks of rubber of different hardness's I may try it... maybe lol.

Edited August 20, 2010 by Cannonball89

[260DET]

Had cause just the other day to apply the brakes in a fast corner for avoidance purposes, lost grip momentarily but was able to recover and avoid a crash. Nice modulation saved the day, something to keep in mind.