Sorry, I'm a little late to this thread but.......

I always believed it was just the opposite. Titanium is very light, very strong, resistent to oxidation (won't rust) and very resilient to heat. I think it's also is good at disipating heat too, similar to the qualities of aluminum vs cast-iron. Some of the reasons they used it extensively in the SR-71 (Blackbird) aircraft, which had to deal with the friction heat of sustained mach 2.5 + speeds. I don't know as a fact, but I figured the reason you never saw full titanium cat-backs was due to to the cost. Titanium is relatively rare (ironically we actually bought titanium ore from the Russians to build the SR-71...a cold-war surveillance plane) and it's hard to work with. Could be wrong, but I just assumed that stainless was easier and cheaper for the bulk of a cat-back. It might have excellent qualities for a brake rotor, light and strong, but VERY expensive, ala ceramic or carbon.

 

In the SR71, titanium was chosen over aluminium, not over steel. Aluminium is no use over 250C, whereas titanium is. Steel would retain its strength at higher temperatures than aluminium (off the top of my head Ti is good for 900MPa, very high strength steels 1600MPa), but is heavier than titanium. A serious reason for not using titanium in brake rotors is that it is susceptible to galling, so you end up with poor brake life

 

Mmmm OK. But you say that like I suggested that it WAS chosen over steel. I didn't. Accepting your right about the galling issue, especially if using traditional pads. I don't even know if they make such rotors, but I could still see it working in terms of heat and weight, and given the cost, for well funded at the limits racing applications only... which was what originally prompted my post.

 

take a look at the aftermarket steel ones and some SS braided lines I love mine and the whole kit was pretty reasonably priced try rx7.com for there bonez SS set or if oyu wanna go hardcore call brembo or grex etc. whatever your preference is.

 

What is it got to do with Ti rotors??



Mave, I think Ti rotors are mainly used by drag racers who wants to loose some inertia weight. By what I been hearing from others is that Ti rotors are coated because otherwise, it doesn't stop as well as steel. And I've heard they are useless on track. But I been trying to get first hand info and so far I been un successful.

 

That is just bogus. The reason behind it is very few people could afford what true TI costs let alone the facility’s required to weld them. There is absolutely no reason one is incapable of being used as a full exhaust system what do you think race cars use????



Back to brake rotors I would suspect Ti to be to brittle, however I would much chose a ceramic rotor over Ti but at around 8k a piece they are also out of most peoples pocket range.

 

OK, that makes sense, so you use the Ti as the heat dump, and the coating as the frictional surface. Gets its OK for a few stops, just gets messy when you wear through the coating! Do you know what the coating is incidentally, or is it a nitriding?

 

What I was trying to say was, the use of Ti as a high temperature material on the SR71 doesn't mean that Ti has sufficient high temperature capabilities for use on a brake disc. Ti is sometimes regarded as some kind of super material because of its rarity, whereas in reality evern without considering cost, it's the optimum choice in only a limited number of applications.