Why aren't brake calipers made from Titanium?

[freelab]

I've been looking around and doing some research, but I can't find any reason (other than cost) for not making callipers from Titanium? I would have thought with it's good thermal properties, high strength to weight and corrosion resistance, it would be an ideal material?

Would love to know why more race series and cars don't allow it to be used, although I understand the cost side of things. Just interested to know if a caliper was made from this material, what would be any disadvantages.

[sgth0mas]

my guess is because aluminum is less dense and has a much higher heat transfer coefficient, but im not 100% sure to be honest.

[hpras]

My Guess

machining aluminum = easy (in comparison)
machining titanium = a bitch

Unless there are quantifiable reasons (lap time reduction, race longevity) to go to Ti from Al, Al will be the material of choice.

[freelab]

Should the caliper be taking the heat our of the pads and discs, or is this the job of other cooling elements? Surely you would try to keep the heat away from the fluid? Which is why a lot of callipers run titanium cups on the pistons?

[Tim.Wright]

Brakes are largely designed to stiffness and thermal targets, not ultimate strength (which is where Ti is superior).

Compared to Aluminium, Ti has about the same specific modulus but much lower thermal conductivity. This means that they would be difficult to cool and also explaibs why they are used for the pistons themselves (to insulate the fluid).

There are regulations limiting the specific modulus of certain upright elements (I don't remember if this extended to the calipers too) and certain companies have developed high performance aluminium MMCs specifically to be on the limit of the specific modulus limits of the F1 regs.

[matt21]

11.2.1 All brake calipers must be made from aluminium materials with a modulus of elasticity no greater than 80Gpa.

Titanium is forbidden.

[sgth0mas]

What is the rationale behind the regulation? Cost? Safety?

[Cold Fussion]

Cost I'm pretty sure. I think those regulations were introduce after Mercedes starting making pistons out of AlBe.

[matt21]

The strength of the material determines the force you can transmit between the disc and the pad, thus limiting braking power.
For the same reason you´re only allowed one caliper with six pistons max. per wheel.

IFAIK Prost (or was it Benetton) developed a 360°-pad. But with only six pistons it was rendered useless.

[sgth0mas]

The strength of the material determines the force you can transmit between the disc and the pad, thus limiting braking power.
For the same reason you´re only allowed one caliper with six pistons max. per wheel.

IFAIK Prost (or was it Benetton) developed a 360°-pad. But with only six pistons it was rendered useless.

Sort of, force will also depend on the part geometry, which is not limited By that rule. They actually only limit modulus which places a controll on the stiffness and deflection of the material used.

using the 360deg pad for example, with an extrememly stiff material, the number of pistons has less of an effect due to almost no deflection between pistons. This will create a more consistent pressure profile between pistons. So maybe thats part of the answer...because with very stiff materials, the 6 piston limitation is less limiting.

But that still leaves the decision down to cost or safety. And i think cost has to play a big part in that.

Aluminum has a very low modulus compared to other metals.