Floating brake caliper operation

[The Critic]

I have a question regarding the operation of a floating brake caliper. From my understanding, on a floating brake caliper, hydraulic pressure is applied to the caliper piston to activate the inner pad. As the hydraulic pressure increases, the caliper moves and the outer pad is then engaged. Therefore, is it true that the inner brake pad is responsible for more of the braking power as the caliper piston directly contacts the inner pad and more pressure is applied?

The reason I ask is that I saw a commercial for NAPA's Adaptive One Brake Pads. According to them, the inner pad is formulated to provide extra braking power compared to the outer pad. If I am understanding the principles of caliper operations, then this is a great idea as the inner pad plays a greater role than the outer pad.

Therefore, am I understanding this correctly? Is this Adaptive One concept a gimmick, or does it actually have some merit? Has anyone tried these pads before? They are awfully expensive.

 

[glennc]

I suppose if the sliders were frictionless the pressure applied would be equal. However, they are not, especially after wear takes a toll there might be enough friction to make one pad do much more work than the other.

I think if you keep the sliders well lubed it should not be an issue.

 

[XS650]

It sounds like a solution in search of a problem.

Glennc makes sense.

 

[The Critic]

Thanks. So with that said, do the Adaptive One pads actually make sense, or is it just a gimmick?

 

[XS650]

Gimmick or worse.

If everything is working like it should, the pads will wear sort of evenly.

If the pins are sticking, you will have less pressure on the far pad, so that's where you would want the extra sticky faster wearing pad to even out braking forces and wear.

It sounds like their have things backwards.

 

[The Critic]

Originally Posted By: XS650
Gimmick or worse.

If everything is working like it should, the pads will wear sort of evenly.

If the pins are sticking, you will have less pressure on the far pad, so that's where you would want the extra sticky faster wearing pad to even out braking forces and wear.

It sounds like their have things backwards.

On the G35 that I performed brake service on recently, the inboard pad was worn to 2mm, while the outboard pad had about 3.5mm remaining. This was the case with both the LR and RR. The slide pins were well-lubricated and nothing was stuck. Any idea?

 

[glennc]

Well, as you apply the brake the piston-side pad is always going to be ahead of the opposite pad on the friction curve. That will tend to twist the caliper, increasing the friction on the pins and making it harder for them to keep the pads applied evenly. Since you are seeing more wear on the inboard pad, consistent with the marketing claims, perhaps there is something to it. On the other hand, what XS650 said also seems to make sense. Do you want to even out the braking force, or the wear? Maybe the best compromise is to leave things as they are. And 1.5mm difference in wear doesn't seem like a whole lot.

I still think that if you keep everything well maintained, the brakes will work well enough that you could never tell any difference.

 

[XS650]

Originally Posted By: glennc


I still think that if you keep everything well maintained, the brakes will work well enough that you could never tell any difference.


+1.

The 1.5mm difference in pad wear isn't worth chasing unless there is a demonstratable improvement in performance and/or pad life.

 

[The Critic]

Originally Posted By: XS650
Originally Posted By: glennc


I still think that if you keep everything well maintained, the brakes will work well enough that you could never tell any difference.


+1.

The 1.5mm difference in pad wear isn't worth chasing unless there is a demonstratable improvement in performance and/or pad life.

Right, but the reason why I used the example is that 1.5mm was significant in the case of the G35. The rear pads only start out at 8.5mm, and the wear limit is 2mm.

 

[glennc]

Perhaps you could assume that they will even out the wear perfectly and in all other respects be identical to the best "other" pad you could buy. Do the math to see if it would be worth the expense in that ideal case, and if so, use that logic to justify buying them as a trial. I'd be curious to see what you'd find.

Was there any indication that the slider pins were not working well?

 

[shoz123]

Rotate the pads........

 

[crashz]

Performance may be the same or better, but I wonder about heat generation. I wonder if it equallizes the heat generated on either side of the rotor or if it causes an imbalance? A significant heat difference could really cause strange brake behavior.

 

[Gary Allan]

Quote:
Do you want to even out the braking force, or the wear?
The real point to ponder.

Quote:
Right, but the reason why I used the example is that 1.5mm was significant in the case of the G35. The rear pads only start out at 8.5mm, and the wear limit is 2mm.


Only an issue for those who don't plan their brake service and/or rely on inspections or "when they need them". Most people are into patterns of use. That person should now know that whatever mileage that wear occurred at, they need to have it performed again if they don't want to .........

..never mind ..you do major surger- I mean a complete overhaul .. I mean a 100% "must do" refit every time.

Sorry. You don't have to tell them squat. The cost is the same between good sense and no sense in brake service

 

[The Critic]

Originally Posted By: Gary Allan
..never mind ..you do major surger- I mean a complete overhaul .. I mean a 100% "must do" refit every time.

What do you mean?

Besides, the person cannot always expect the brake service to be needed again it X number of miles. The new OE pad I installed may have had a formulation change. Driving habits may chance. etc.

 

[Gary Allan]

Bla-bla-bla

Pad slap the bee-atch and send them down the road

 

[AcuraTech]

Sounds good on paper but that would mean the pads are of two different formulations. Sounds like a sketchy marketing claim as opposed to solid science. I see different wear rates on inner/outer pads quite often, but usually due to things like:

-Rust buildup on rotors or caliper brackets
-Sticky or under-greased slide pins
-Ill fitting aftermarket pads
-Improperly bled brake systems
-Stuck or almost stuck caliper pistons

Most car brake systems have at least one or more of the above issues. Having a "healthy" brake system goes a long ways toward minimizing different wear rates.

 

[AcuraTech]

Also have to mention how many times that I have to take a hammer and chisel to get the brake pads out of the caliper brackets, usually due to rust/brake dust/road grime buildup. Once the caliper is off, the brake pads should almost fall out by themselves if everything is set up right.

 

[Shannow]

Remember that on the single piston calipers, there is no seal ring to provide that tiny little amount of piston retraction.

Guess what pushes the pads away from the disk ?

I loathe single piston designs as poor engineering versus accounting practice. I've had cars with twin piston and single. Larger cars with singles, and SUVs with 4 pistons and single.

I can't seem to wear out the pads to any great extent since I turned 25.

 

[punisher]

Originally Posted By: Shannow
Remember that on the single piston calipers, there is no seal ring to provide that tiny little amount of piston retraction.


Not quite sure what you are talking about here. The seal (square o-ring) is the same as multi cylinder calipers. If you are referring to the outer pad not retracting, then you have a point. If it was a problem however, we would see a lot more outer pad wear vs inner. Usually it is the opposite.

 

[Gary Allan]

Quote:
I can't seem to wear out the pads to any great extent since I turned 25.


I think that this coincides with why, here in the States, insurance rates typically get reduced at this age too.