Page 1 of 1
Drilled-Slotted Rotors & differential bore calipers
Posted: Mon May 03, 2021 5:17 pm
by j-c-c
Does using slotted and/or drilled rotors eliminate or mitigate the need for differential piston bore calipers? My question disregards in this discussion weight or cooling issues, in the thinking slots are best at "wiping" pads and holes are useful for removing pad gases/debris. And is the reverse then somewhat true, using same size caliper pistons in a 4 or more piston caliper with slotted and/or rotor holes, has few downsides?
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Tue May 04, 2021 3:51 pm
by lefty o
still need the same size calipers/pads regardless of slotting or drilling. drilling rotors is generally not a great idea as they tend to be where rotors crack when they get hot. slotting doesnt have the same issue.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Tue May 04, 2021 5:19 pm
by Rick!
Maybe look up essexparts.com and talk to Mike O’Neil.
He hangs out on an SAE forum now and then and seems to be well versed in performance braking.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Sun May 09, 2021 7:37 pm
by BOOT
From my research Slots are safe and the rotor may last longer, holes are best for weight reduction but crack. Either help with gases or wiping the pad(staggered holes).
Differential piston bore calipers never herd of em BUT I'm into acceleration more than de-acceleration. Anyways w/o knowing how they work and just giving it a bit of thought in relation to your points in your post. The rear piston would see a hotter rotor than the front, so is a larger piston used in the rear?
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Mon May 10, 2021 6:09 am
by j-c-c
Yes, if "rear" here is defined as the trailing piston in regards to rotation. Not sure how much "heat" directly plays in this solution so much as pad "debris/gas"?
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Mon May 10, 2021 11:48 am
by David Redszus
Slots are used on solid rotors to "wipe" them clean of debris and hot gases.
Drilled holes are used on vented rotors to improve the air flow through the rotor vents.
Very often, holes are drilled randomly (or incorrectly) which does not produce proper
heat distribution and then leads to cracking. With a correct hole pattern and chamfered
edges, cracking can be reduced; also by reducing rotor temperature.
Early single piston calipers used a stepped edge on the piston/pad contact interface.
This would provide a tapered force from leading edge to trailing pad surface.
With multi-piston calipers the differentiated diameter pistons now serve the same purpose.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Sun May 23, 2021 5:25 am
by BigBlockMopar
IMO I would think a hole chamfer would also need to be deep enough to be still present after the rotor has worn down a bit, otherwise it would develop sharp edges and promote cracking again.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Thu Aug 05, 2021 10:38 pm
by allencr267
This pic is NOT a mistake.
Girling 3 piston caliper, OEM on Jag, Alfa & others
Why? No fucking clue. Some engineering is trial & error, then figure out why it works.
Unless you need eye candy for sponsorship, you can skip/ignore a lot of stuff.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Mon Aug 09, 2021 12:55 pm
by David Redszus
allencr267 wrote: ↑Thu Aug 05, 2021 10:38 pm
This pic is NOT a mistake.
Girling 3 piston caliper, OEM on Jag, Alfa & others
Why? No fucking clue. Some engineering is trial & error, then figure out why it works.
Unless you need eye candy for sponsorship, you can skip/ignore a lot of stuff.
Were these clamshells clamped together to form a single caliper?
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Tue Aug 10, 2021 12:30 pm
by chimpvalet
4 x through-bolts, i believe
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Tue Aug 10, 2021 11:38 pm
by MadBill
allencr267 wrote: ↑Thu Aug 05, 2021 10:38 pm
This pic is NOT a mistake.
Girling 3 piston caliper, OEM on Jag, Alfa & others
Why? No fucking clue. Some engineering is trial & error, then figure out why it works.
Unless you need eye candy for sponsorship, you can skip/ignore a lot of stuff.
One unlikely possibility is that they wanted the customer to see a dual piston caliper through the wheel spokes but the inboard side, appearance being irrelevant, could make do with a single.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Wed Aug 11, 2021 3:37 pm
by David Redszus
Interestingly enough, the difference in piston areas is within 5%. As would be the braking forces.
How the pads fit the discs remains to be seen.
Re: Drilled-Slotted Rotors & differential bore calipers
Posted: Fri Sep 03, 2021 1:23 am
by Kevin Johnson
allencr267 wrote: ↑Thu Aug 05, 2021 10:38 pm
This pic is NOT a mistake.
Girling 3 piston caliper, OEM on Jag, Alfa & others
Why? No fucking clue. Some engineering is trial & error, then figure out why it works.
Unless you need eye candy for sponsorship, you can skip/ignore a lot of stuff.
https://patents.google.com/patent/US2951561A/en wrote:
In other arrangements there may be three angularly spaced cylinders on the one side and one or two on the other; or four on the one side, and one, two, or three on the other; or five on the one side and one, two, three or four on the other.
Whatever the number or arrangement of the cylinders the diameters or cross-sectional areas of the cylinders will be such that the forces applied to opposite sides of the disc will be substantially equal.
It will be obvious that in any arrangement in which there is a smaller number of cylinders on one side than on the other, the cylinders of smaller number will be of greater diameter than the others so that the radial dimension of the central part of the caliper limb housing the larger number of cylinders can be substantially less than the corresponding dimension of the other limb, and conversely the circumferential length of the central part of the caliper limb housing the smaller number of cylinders can be less than the corresponding dimension of the limb housing the larger number of cylinders.
This feature is of considerable advantage where the brake disc is mounted on the inboard side of a road wheel, as the caliper can be mounted with the limb housing the greater number of cylinders on the wheel side of the disc between the wheel hub and rim, the smaller circumferential length of the other limb housing the smaller number of cylinders allowing the caliper to be accommodated in the relatively restricted space between the steering and suspension components of the vehicle.