A Question for You

[antijam]

Which results in more or less spring load and suspension travel.

Sorry, I guess we have to disagree. The bearing load is reacted in the hub which in turn is reacted back at the caliper where where the braking force was originally generated. None of the braking forces generated at the caliper are transmitted to the suspension.

 

[Vetman]

Then please explain how anti-dive is achieved by calliper positioning only.

 

[antijam]

Dive results from the moment derived from the deceleration of the mass of the car and the position of its centre of gravity relative to the suspension anchorage. This moment is independent of the brake caliper position. Moments do not result in spring compression, only forces do that. On cars with independent front suspension - double wishbone for example - dive under braking is often reduced by inclining the wishbone axis so that, if extrapolated, it passes through or near the position of the cars centre of gravity. If you imagine the extreme case of a car decelerating with its brakes locked the position of the caliper is immaterial to the resultant dive.

 

[Vetman]

I do enjoy a good debate. Some of what you say is correct but Isaac Newton is on my team. Every action has an equal and opposite reaction. The couple or torque generated by calliper and axle forces are reacted through the upper and lower control arms and into the chassis. The chassis sits on the suspension springs. The load in the springs front and back changes to react the calliper induce torque. The reaction force between tyre and road is unchanged because the calliper and axle vertical forces are equal and opposite. These overall tyre forces are only determined by car weight, wheelbase, height of car CoG, kinetic energy due to velocity, and retardation force applied.

 

[antijam]

...... The load in the springs front and back changes to react the calliper induce torque......

I (and I'm fairly sure, Newton) totally agree, but my point is that the induced torque and therefore the load reacted at the springs is independent of caliper position. Braking loads at the caliper are not transmitted to the springs, it is the loads resulting from reacting deceleration moments that compress or extend the springs.

 

[Vetman]

Correct but the position of the callipers modifies the internal forces within the vehicle, including spring compression. Without changing the external reactions.

 

[antijam]

Correct but the position of the callipers modifies the internal forces within the vehicle, including spring compression. Without changing the external reactions.

Not sure I follow that entirely, but if what you're saying is that caliper position affects the cars moment of inertia in pitch then I agree - it's a pretty minimal effect though given that the mass of the caliper is a very small percentage of the mass of the vehicle. It doesn't alter my contention that there are no loads transmitted to the springs solely in reacting braking torque. Any change in spring loading results from reacting the inertial moment due to deceleration.

 

[Vetman]

One last attempt to win you over.

The reaction between road and tyre comprises spring load, weight of the wheel and tyre, and any reaction caused by the calliper/axle torque. For a drum brake or double calliper this component would be zero. As the overall reaction cannot change then a downward calliper induced force due to its offset position must cause a reduction in the spring force.

If still not convinced then Google anti dive braking.

 

[antijam]

One last attempt to win you over.

The reaction between road and tyre comprises spring load, weight of the wheel and tyre, and any reaction caused by the calliper/axle torque. For a drum brake or double calliper this component would be zero. As the overall reaction cannot change then a downward calliper induced force due to its offset position must cause a reduction in the spring force.

If still not convinced then Google anti dive braking.

OK - one last denial. Regardless of the position or number of brake calipers the application and direction of torque is the same. That that torque induces a moment at the car chassis promoting dive I agree. However the braking load produced at the caliper is reacted entirely within the hub assembly. As said before the position of the caliper does affect the load on the axle bearing but this is reacted back to the caliper and does not result in a load on the spring.

I suspect we have flogged this subject to death and I can find nothing on the internet that convinces me of your contention, but do post a link to any supporting documentation.

 

[Vetman]

Ok, until the next bone of contention.

 

[antijam]

Ok, until the next bone of contention.

 

[Roscobbc]

Jeez - I thought this was going to end up as 'moment arms' at dawn..........

 

[antijam]

W

Jeez - I thought this was going to end up as 'moment arms' at dawn..........

Well, it's just nice to find a forum these days where you can air an honest difference of opinion in intelligent discussion without being subject to ridicule or personal insults.

 

[Roscobbc]

Anyway C3 brakes are still crap compared with current offerings on the most basic vehicles..........

 

[kentvette]

Anyway C3 brakes are still crap compared with current offerings on the most basic vehicles..........

That's another "bone of contention" Ross! I think you have non power brakes? I've always maintained that there is nothing wrong with properly set up C3 brakes, particularly if they have O-Rings, which eliminates the "air-induction" issue. I have always felt as secure in our '78 as I have in most other car's I've driven, except maybe a C6 GS!

 

[Vetman]

I find with my C3 brakes that in an emergency stop there is always a ‘heart in the mouth’ moment before they bite. Whereas my Toyota has you testing the seat belts immediately.

 

[Roscobbc]

That's another "bone of contention" Ross! I think you have non power brakes? I've always maintained that there is nothing wrong with properly set up C3 brakes, particularly if they have O-Rings, which eliminates the "air-induction" issue. I have always felt as secure in our '78 as I have in most other car's I've driven, except maybe a C6 GS!

And I'm sure you are 100% correct - and ordinarily I would agree...........with a stock vehicle. Yes, I'm using 'o' ring seals - yes, the brakes are in good condition, - yes, using good pads (Hawk HP Plus) However with 50% more of 'everything' braking inadequacy (certainly for me) is still an issue. I remain to be convinced that some of the aftermarket 'big' brake options on the market are a significant and worthwhile improvement. Even in the 'States the best you will get from anyone who has used ab altermative is "great brakes, work well bla, bla, bla". No one individual or company has actually measured and compared stopping distances etc. I'm certainly not prepared to shell-out 3 or 4 £K in an attempt to significantly improve my brakes based on comment like "great brakes, work well" etc etc

 

[kentvette]

I find with my C3 brakes that in an emergency stop there is always a ‘heart in the mouth’ moment before they bite. Whereas my Toyota has you testing the seat belts immediately.

Never had that problem, even before the O-Ring seals went in.

 

[Oneball]

I find with my C3 brakes that in an emergency stop there is always a ‘heart in the mouth’ moment before they bite. Whereas my Toyota has you testing the seat belts immediately.

Id check the runout of the discs, sounds like the pads are standing off.

 

[Vetman]

Will do. Any cyclic noise caused?