Brakes!!!

[artie on edge]

I"ve seen various comments re the unsuitability of mild steel sheet for discs.... interesting.... I've used mild for many years (and on full sized machines) and have never suffered a disc failure UNTIL I started cutting cooling grooves in discs (then warpage raised its ugly head).

Mild (in fact any drawn sheet or tube) has a 'grain' structure and should warp as it gets hot and cools etc. This is why cast is such a good material as it has no grain structure being nodular (that plus its friction co-efficients and malleability), for brakes.

My question is then...what are you guys using for disc material?

A fellow over here is using stainless for his discs and he has been told (by a buggy designer/builder) that due to the nature (I can only guess they are refering to friction co-efficients) of stainless he will experience brake overheating.

I guess my point is that (at least over this side of the pacific) there is a fast developing black magic culture regarding discs on superlites.

My background is in the braking/suspension industry and unless you guys can advise me on a super material for discs I will use the KISS principle...

Yes im about to assemble my brake package for my new chassis... so this question is timely.

My stance is simple.

Friction equals heat (energy transfer), brakes must create, then absorb heat, then dissapate heat ASAP.

Lots of factors come into play here but put simply COOLING is the key. Your disc must have enough mass to be able to absorb the heat of braking, and then get rid of it to the airflow as efficiently as possible.

So lets talk about mass. Lots of folk use very thin micro discs for a variety of reasons (usually weight savings). You must be careful here, the disc MUST have enough mass to absorb the heat generated by a couple of good stops. These buggies (Hyabusa powered etc) can get real fast! They then need to brake real hard and 'cause they are so quick they are real fast again BEFORE the brakes have had time to cool so they may be called upon to absorb even more heat before they've dissapated the residual heat from the last stop.

This is a fundamental issue which (I think) some builders in OZ have overlooked. One guy (designer) is enclosing his single rear disc inside a housing completely out of the airflow. Now one of his customers who is actively racing his design is frying discs and is asking why, no surprises really is there?

My thoughts are that airflow is crucial and if you are running a single inboard disc it is even more so.

Man you gotta love brakes, we abuse the crap outta them then ask them to perform at their optimum time after time, poor little buggers......

[borris]

I'm smack in the middle of taking inventory and can't say much at a time today but YOU ARE SPOT ON in your analysis.I think you may be a bit more qualified than I from reading what you said but I couldn't agree more.I'll try to comment more on your points later.It's REALLY nice to see someone that understands braking principles. FWIW the most powerful system on a car is not the engine-it's the BRAKES.

[Admin]

Really the debate we had on mild steel that got me banned from another forum, was comparing them to a zinc plated rotor, Imo there is nothing wrong with a mild steel rotor, as long as it is pickled and oiled...

[SPEC]

[borris]

And of enough mass as Artie has pointed out.Steel is not the best choice but serves us pretty well.Cast grey iron is best but we can't easily fabricate CUSTOM rotors from it. Brembo makes a lot of small C/I rotors that would suit us very well but are not blingy enough for some even though they are relatively cheap and very durable.

[SPEC]

I'm in agreeance with borris on this one ...With so many High quality brake component manufacturers out there I was just kinda trying the reinvent the wheel...Ya it was neat to have custom made rotors...Was it worth the smoke and stench on the ride home after warping them??? NOT Plus I felt foolish

[LiveWire]

in BugPac's case, these were not for a custom app, but for a machine where a volume manufactured (EBC) brake disk was available. The mild steel rotor was a copy of the original in terms of cross holes, thickness, etc. So their was no cosmetic advantage to the mild steel ones. In fact, the zinc plated EBC ones look nicer.

[artie on edge]

I find this topic fascinating, really do, so I often think I am one sick F*&%$#. While Im not a fan of mild rotors I think the cost and ease of working factor makes then the first choice for most users.

I think I was being too cryptic though, my concerns are for those very pretty, slotted, shaped artistic rotors that have very little metal left. I had better success WITHOUT these adornments...but Bling being Bling.....

Seriously, if our rotors are so small (and they sometimes need to be so), they NEED the mass we are removing by making them pretty. Incidentally, the industry jury is still out re cooling drillings or slots through the rotor. Much more effective is the bridging fins as per your normal road car but that isnt an option for us.

Yes drilling and slotting do work (to a degree), but do they also reduce braking efficiency by firstly removing available surface area and THEN removing available storage mass? Yes to those as well.....

Finally there is one better material than nodular cast iron.. (sorry Boris) and I have a set but they aint ever goin on no buggy. And that is carbon fibre, these super discs arent drilled, they arent slotted, they ARE bridged, they are nice! And I have then sitting on the wall and I LOOK at them...they are my workshop Bling...

And dont also forget that HARD mild discs require SOFT pad material to retain a relevant friction co-efficient.

Later guys

P.s. did anyone know that rotor slotting was originally used to wipe the pad a disc surface clean of squeal inducing brake dust and wasnt through the disc but a surface indentation?

[borris]

I agree . The bridging fins on CI rotors also pump air through the rotors for cooling.Many don't realize that.Most factory rotors now are curved vanes and directional whereas replacements may be straight vanes and not provide proper cooling as the OEM designed into them with the curved vanes. Carbon/carbon are the cats meow for sure but A BIT PRICEY!  And finally I agree also that proper pad to rotor materials matchup is essential.

[Odyknuck]

Very interesting topic. I have used SS, CI and MS rotors in various applications. The CI seem to work the best and squel the least albiet not the bling we like. However lets face it do we want to stop or just look good when we miss that turn and wrap our Buggy around a tree? I do have a question about Jamar brakes. They appear to be MS. Does any one know for sure. I can not get them to stop squelling.

[borris]

Cast iron has the best vibration(squeal) dampening ability of all along with excellent heat dissipation capability.That and low cost are why automotive brakes are CI.