Article on The Internet Mini Encyclopædia |
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SSI Insert revised (no index tag!): 22-Feb-2016
Article on The Internet Mini Encyclopædia |
"Under heavy braking the servo effort is over-powered by foot effort, so it's redundant. Under light braking, yes, servos do make it easier for you.
Many people say the servo power is ADDED to the foot power, even when standing on the pedal. This isn't true, because once the force of the servo diaphragm acting on the master cylinder was surpassed by the force of the foot acting on the master cylinder then the diapragm has no effect. It will now be just sitting there, or even acting against the foot!
BUT!!! And this the bit everyone forgets!! "It's not how big your brakes are, it's what you do with them"...
Think about what happens when a kid runs out in front of your car. What do you do? Stamp on the brakes and stop ASAP.
This is what really happens.
"Oh, look a kid. I must stop.Where's the brake? Under my right foot. Hang on my foot's on the throttle. Move it over. Start pressing down. Am I stopping? Nah..not much. Push harder then! Stopped? No! God damn it! Push bloody hard! Jeeeeeeeeee..." crunch...squish... kid leaps out the way, but drops his lunchbox on the road!
Now with a servo....
"Oh, look a kid. I must stop. Where's the brake? Under my right foot. Hang on my foot's on the throttle. Move it over. Start pressing down. Mmmm...nice. Am I stopping? Yeh, the brakes are on pretty good already actually. Stopped? Not yet. Push harder! Stopped? Yep....just!" Kid picks up lunch box and runs off.
If you drew a graph of braking power against time, a servo graph would go up quick and level off at max. An unservod graph would pretty much be a linear rise, as the human brain feeds back at regular intervals. Personally, I prefer the 'in touch' feel of un-servo'd brakes. That's why I haven't fitted one."
Removing the servo (2 versions)
Once the reservoir is drained, disconnect the brake pipes. Then there are 4 nuts which hold the servo onto the mounting bracket. Undo these, then there is just a split pin to remove and the unit will come away. If you need to remove the bracket, then the clutch servo will need to come off too.
If you can't get to the split pin at the bulkhead end of the servo pushrod, then you can unscrew the rod by undoing the lock nut and turning the rod with mole grips.
It will make sense when you have a look.
OR:
You will require a long socket extension bar to remove
the lower 2 bulkhead nuts.
You could do it the other way but the bottom nut of the four on the servo is a
bitch to get on to...
Feedback from Matthew Allott
Hello, I read your article on servo assisted brakes with some bemusement. It seems quite obvious that you have no understanding of the way servos work. It is true that servos add nothing to actual baraking efficiency, this all comes down to pad size/ material, disc size/material, cylinder bores heat etc. What a servo does is reduce the amount of effort required by the driver wether he is applying 10% or 100% of his/her effort.If you don't believe me then get in your car, pump the brake pedal a few times to release the depression inside the servo, then press the pedal as hard as you can. This would be your max braking without a servo. Now start the engine, you will now feel the pedal sink a little more as the servo assists you. If you were a proper mechanic you would surely know this simple way of testing a servo to see if the diaphragm is ok. May i suggest a little more research into your articles before publication, so that readers with little technical knowledge are not mislead.
Regards Matthew Allott
NB The IME are not certain if his comments relate to this article or a post on the MINILIST
07 May 2003
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