Brake servos - any opinions?

All,

What is the general consensus on the necessity of servos? I'm putting together a spec for my braking system, including a new pedal box with twin M/C's.

I'm keen to do away with the servos, does anyone have any experience of running with/without?

Will a non-servo system have a really tough pedal?

Does anyone have a starting point for pedal ratios?

Any opinions greatly received!

I have heard the rule of thumb is 2500 lbs. Above needs servo assist, below does not. That would put the GT40 right at the limit.

Also, as I have stated previously I have a self written program in Matlab that does a complete analysis of the braking system (non-servo) that is available free to those who have access to Matlab.

Thanks Brian, I'm glad my membership was recieved OK.

Julian,

The need or not for servo's or boosters is to do with design of the COMPLETE break system but can also be function of "what feeling is NORMAL".

The later is best dealt with first : many people have an understanding of what a break pedle SHOULD feel like. They have an understanding of how much pressure should be applied and the only system that will satisfy them is the system that they are used to, the system that makes them feel comfortable. This system usually involves a servo and this is because the servo system requires less pressure to apply and therefore our weaker sex can operate with ease.

Almost ALL true race cars do not fit boosters. There must be a reason !!!

With good design and correct matching of front combined piston area, rear combined piston area and master cylinder ('s) piston size and whether a proportioning valve is REQUIRED or not a well balanced and adjustable system can be easily designed. The quality of the components is also very important as pedal feel is dependant on quality of components. This system without the servo will give a good pedal and optimum breaking can be easily obtained with practice.


Best wishes,

Robert

Julian

Your December edition of Fortyfication will be with you in the next few days. In it is an article headed 'Stopping the Momentum' by club member Lyndon Evans. It is an excellent article to refer to and finishes with a chart of Actions and Effects such as changing from solid to vented discs or using a smaller master cylinder. I think this will answer most of your questions.

Brian.

Hi Julian

If you stay with the GTD pedal box the chances are you will need servos. The guys that have Tilton pedal boxes often remove the servos as pedal ratios are better for it. Obviuosly whole brake package needs thought as tiny brakes plus no servos is a disaster waiting to happen. I run servos but guess split in competition crowd is about 50/50. Do you need to decide soon? Can you wait till next comp event and then come and ask the guys to sit in cars to check out differences?

Malcolm

Robert, Malcolm, thanks for our opinions. I hear what you're saying!

I'm answering my own question now, but now I know there are others successfully running without servo's I'll be doing the same.

I prefer a harder pedal & don't like the feel of the servo's 'sucking' the brakes on. Oh, & I like the 'KISS' philosophy!

I'm not happy with the GTD pedal box either so that'll be joining the servos!

Altho I haven't put a tape on it yet, faveourite option (at the moment) looks like the Tilton firewall mounted pedal box. It looks like it'll fit without too much fabrication.

With this option, the MC's are easily changed & bias is driver adjustable for fine tuning.

Loks like another item to add to the shopping list!

Hi Julian, I have a Tilton pedal box and giant AP 6 pots at the front and 4 pots at the rear, Tilton master cyliders and no servos. The installation is fairly straight forward, but there are one or two details that make all the diference )apart from a bottomless bank account).
Braking is excellent, firm and progressive with plenty of feel. If you are ever in the Surrey area and want to have a look at the set up, please drop me an e-mail.
Regards and best wishes of the season,

Mike

Mike
I have 6 pot front/ 4 pot rear AP calipers with tilton pedal box. What size master cylinders did you fit? As I'm installing the brakes at the moment, I'm interested in the details that made the difference.

Ross

Julian

I can also confirm that I have removed my servos after swapping the standard GTD pedal box for a Tilton pedal assembly. Instead of going down the AP Racing route for the brakes
(which are undoubtedly great brakes), I opted for 6 pot calipers on the front and 4 pot calipers on the back from Hi-Spec. These also have phenomenal stopping power but are more competitively priced than those by AP Racing.

Hi Ross, I haven't got the car at home at the moment, but I'll check in the next few days.
regards, Mike

Martin, thanks for your input. I've spoken to Hi-spec & they seem very attractively priced & Look the biz!

Is your pedal box a firewall mount or overhung? IE are the mastercylinders ontop of the pedals or infront of them?

It looks like either pedal box will fit.

The pedals are on a special mounted bracket manufactured by Wealden Engineering and they are on forward-mounted master cylinders.

Thanks Martin, input much appreciated!

Martin
Do you have a web site or contact # for Hi-Spec??
Bill

Bill,
http://www.hispecbigbrakes.co.uk/

regards,