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9000 Brakes Uprating the Servo ?

3K views 5 replies 2 participants last post by  wrighar 
#1 ·
I originally posted this query on UKSaabs, but got no response because
(a) the site went awol
(b) its a stupid question
(c ) obviously too difficult. :smirk:

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Aeroadster wrote: On YLee's subject of underservoed brakes, has anyone fitted the servo from a 9-3 Viggen. If so, does it fit, does it work (i.e. more effective than the servo from the 9000) and is it a pain in the neck to do?


LoganSaab
Does anyone have experience of fitting an uprated servo to the 9000? Or if not perhaps some pointers to the likely problems involved, or an opinion on likely candidate units?



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ylee coyote wrote: ......9000 brakes now that is a subject. I think I have spent more on my brakes than probably anyone here looking for the perfect set up, the standard 9000 set up is inadequate .......I have tried lots of set ups and have improved the feel but still not there......My current set up is AP calipers /discs and ds2500 pads but the brembo's had better bite.

My view is the set up is probably under servoed and increasing the servo size would improve things immeasurably............


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LoganSaab

Well I have made a few people laugh when phoning up with my query, 'upgrade the servo Sir'? etc. I've had immense trouble even trying to identify the OEM manufacturer of the servo, let alone its original specification. Ho hum

Finally got some sense from Saabflight who suggest that the ABS will intervene and negate the benefit of the 'bigger boot' from a different servo. I am still not completely convinced that this is a dead end, and find it amazing that SAAB considered the same brakes to be adequate for both the 150bhp 2.0lpt and 225bhp 2.3 Aero.

Saabflight did suggest that in the early days they were able to shave almost a full second from the 0-60 by changes to the suspension, and that logically changes to the suspension that stopped the nose from diving under aggressive braking could help with the 60-0 braking and braking overall.


Any views??

Regards Logan
 
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#2 ·
It depends, Ylee's monster, as is my Scaero, being TCS cars, don't have servo's, so we are stuck there.

The tcs cars have a brake fluid pump and pressure accumulator system which supply's the servo power for the front brakes, and direct high pressure fluid to the rears!

Andew
 
#3 ·
Thanks for the reply Andrew.

I should perhaps have included with the original enquiry the information that I am 'limited' in brake options by retaining the original 15" wheels, and do not intend to change the size, preferring the original look. Changes made include; better than OEM fluid, DS2500 pads and Goodridge hose. Still using the OEM discs, because I have several sets in the shed, but will change eventually to Brembo. The option of different callipers like 4 pots, or larger discs for better 'swept area' are closed because of the limited space inside the 15" wheel. The DS2500 is a slightly larger pad and this may have something to do with the effectiveness.

Many many threads on here and other forums about changing or uprating the brakes, and everyone has an opinion or their favourite, but generally the views are pretty subjective, 'more bite' 'better feel' etc. What I want is more braking 'grunt' actual stopping power, the ability to shed excess speed in a safe and controlled manner.

I still think that a solution can be found by increasing the pressure at the pad/discs by increasing the hydraulic capacity /pressure. I am stymied by a lack of any real knowledge of the hydraulics and braking control systems.

Regards Logan
 
#4 ·
Increased pad size will do nothing, as braking performance is down to mostly

Pad friction coefficent
Calliper piston area
Disk Radius

And to a smaller extent:

Brake fluid compressibility
Brake line rigidity


Disk radius you can't change as you want 15" wheels
Piston area will be the same unless you change calipers (not easily done in 15" wheels)

biggest change you can make is friction pad material.

A bigger servo will just make the brake pedal lighter in pressure to achieve the same result.
A bigger servo will make the barkes less controllable over it's range.
As the standard setup is more than capable of locking the wheels in the dry from all speeds, I'd say it correctly servo'd


To that end, I'd get some good pads such as DS2500, yellow stuff etc
Refresh the brake fluid with a good Dot 4
Fit SS brake line

And then go out and enjoy it.

Andrew
 
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