Should the front pads have a radiused piece cut out of the bottom of the pads? I just noticed some pads are flat across the bottom and some have a radius cut away. The rotors on the front of my 93 have a raised circular strip at the inner edge of the brake sweep area, so I assume the radius cut out pads are preferred? But is it OK to use pads that are just flat across the bottom?

Dan

Here is a picture that may help you understand my question better. You can see the radius that is being worn at the bottom of the Pads. These Pads are flat across the bottom. The issue is causing uneven wear from top to bottom of the pads.

Dan

Dan,

Whose pads are those?


--
Art Benstein near Baltimore

Acupuncture is a jab well done.

I don't really know, either PBR or Axxis. I have some that are flat like this and some that have the cut out like your pic shows from Volvo. I never noticed the difference until yesterday. To me I need to use pads with the cut out but vendors don't seem to know there is a difference. I just got some Axiss pads on ebay and they are flat with no cut out.
Dan

I matched up a new Volvo pad's outer radius with a worn-out rotor. The rust ridge on the inside of the rotor fits where the inner radius of the pad meets. A new rotor is machined all the way to the hat, so perhaps if the pads without a cut there were used since the new rotor began its life, there would be no problem using them.

Alternatively, one could get older rotors trimmed I suppose, but it looks as though cars get used to the notch Volvo put in. Maybe it is there for clearance when displacing water or some reason like that? Certainly not planned obsolescence!


--
Art Benstein near Baltimore

When an actress saw her first strands of gray hair she thought she'd dye.

The installed rotors have a strip that is not machined to the hat, I don't think it is a result of wear? Something else to be aware of on these old cars with who nows what parts have been installed over the years!

I have some new rotors buried on a shelf I need to check.
Dan

Yes, the new rotors are machined clear to the hat. But, instead of providing space for water exit, I thought about how the wear would be uneven there if a new rotor was mated with a new pad not having that inner cut; the amount of friction material available at the pad surface, beginning at that inner radius, decreases from the full amount to zero as it approaches the hat.

So - pads not cut = bad idea for multiple uses of the rotor.
--
Art Benstein near Baltimore

The man who fell into an upholstery machine is fully recovered.

How many miles had been done on the pads shown in the OP? They appear to only worn across a narrow central band so not much actual braking going on there. The pad material could be ground back with a Dremel but a new set of the Volvo pads shown by Art will give you longer life and better braking. Higher cost, but better value for money in the long run.

I'm not sure the mileage on them they were from a salvaged car and just placed on mine a few months earlier. They had good contact above and below the center strip of my car but when I saw the odd wear I took them off and replaced them. My question is related to the use of pads that are cut out verses ones that are flat.

I have never noticed this before so will need to be sure to match rotors and pads better from now on.

I have used Volvo pads but the problem I have with them is how dusty they are.

I don't want to dremel a notch in new pads so I need to buy the ones I need.

Thanks
Dan

Hi there,

I have a set of rotors showing up with that groove around that "hat" (:-) or hub on my '91. I even get a ridge on the outside diameter too as the pads are too low or the rotor is too large.
I suspect they were not originals as I got the car Eleven years ago with 182K.
The pads I use have the radius so they are short enough to not reach past the width of surface.

I am a little late to this post but I think you should just take an angle grinder, that has about a four inch wheel and cut down the material on the pad almost to the backing plate.
Leave the amount of material that is allowed as the minimum thickness to change the pads out on there. The roundness of the grinding wheels edge will leave a fillet curve of about that thickness. This will support surrounding material along the backplate. Basically it will not harm the pad at all.

Just to keep symmetry in check, You can lay another pad that has the radius on top of the wider pad and trace the same curvature. This will decrease surface area of the pad so it will be the same as any other pad as a set.
Making these cuts will allow the bottom edge to wear more slightly. It will seat better and wear more evenly.
I can say this because, the smaller diameter area of the rotor passes less square inches of surface area under the pad there. This is Comparing areas top to bottom of what spins under the edges of the pad.

In my opinion, You will continue to run into these rotors from vendors with this problem in the future, for all types of cars giving machinist skills or automatic equipment quotas, no matter what country of origin. They might be discounted a little in the aftermarket realm for this.
That is probably why some pad manufacturers "IN THE KNOW" have revised their pads with the radius to alleviate the issues in the field coming at them.

I believe this all starts with the cast iron castings having variances in thicknesses and lengths between batch runs. Machine operators are not catching subtle changes between them on the pallets.
Casting cores shift and sand compaction varies. Some metals shrink more or less and gassing causing holes and sand pits.
With these issue outstanding, machinists are using "canned" program routines, running on start points off a fixture and they are not adjusting the "z" axis for just a cleanup. They have excess material but it must be lost correctly when roughing.
The setups Depend on fixtures and proper turning step sequences.
I can see two possible ways to start this job off to make rough cuts to get "a proof" for a good casting to run off.
This is done before any true or finishing cuts are done. If not good, they are to kick it back to the foundry.

Without proper "Z" Compensation, for batch changes, one program can or will "over cut" the other towards the middle, the pad/caliper location diameter.
Turning and or boring the hat or hubs cut can "Possibly" leave a groove under the outboard brake pad surface.
Because the cycle would run out its length of "Z" and then move out in "X" a little bit and then back away. This is to either go back to a home position or rough cut pass on the outboard brake pad surface establishing one side of the large diameter with a rough cut width.
On the opposite end another setup and a different "canned" cycle with an adjusted "Z" axis would be cut or faced from the hubs inner surface. A dimension or "stand off or to the caliper offset" to the inboard brake pad surface.
The top or open end length of the "hat" dimension, where the Tire or wheel rim surfaces meet are not as critical. Even the bolt pattern web thickness is a fairly open tolerance but a cleanup is crucial for sales appeal and wheel security.
Both sides have to be cut with their relationships all leading back to the vented rotor.
All surfaces need a cut on them for best balancing that gets done later on and when it's "out in the wind" you will see even more spiraling tool cut feed lines.

On the finish cut pass, it is this inside hub surface, the one mounted on the cars spindle, that has to be the true for the final pad finishing operation. I would guess, its even the second or even a third setup operation where both pad surfaces are cut or ground to final size. This gets things all in parallel and to the largest under the pads dimension right with good metal showing.

Anyway that my late take on the situation! Look for grooves or radius pads on the inner side.

Phil

PS
My wife found this on the web for a thought.

William Golding, British Novelist
1911-1993

I think women are foolish to pretend they are equal to men. They are far superior and always have been. Whatever you give a woman, she will make it greater. If you give her sperm, she will give you a baby. If you give her a house, she will give you a home. If you give her groceries, she will give you a meal. If you give her a smile, she will give you her heart. She multiplies and enlarged what is given to her. So, if you give her crap, be ready to receive a ton of shit!

I'd rather have good braking with pads that dust a bit than very hard ones which glaze over and reduce the efficiency. I'm in the light braking/only when necessary braking school, so soft material pads are my preference. Discs are really service items, but using genuine Volvo discs should be considered if you are a high miler, as their life on a cost/mile basis will be better than the cheap, sometimes very cheap, options available.
You can get dust shields that fit behind the wheels. These do reduce the dust build up with alloy wheels but if you keep your wheels well waxed the dust comes off easily if you clean them reasonably regularly. Twice a year won't do!