333pg333

So are there any downsides to floating rotors? Do you have to replace all the hardware when replacing rotors?

Lastly, a question about ABS. I have felt my ABS activate when I am coming to a hard and fast dead stop in our versions of Auto X. So I know my unit works. However should I be able to feel it on the track? There's a hairpin corner at our track where you are coming into it pretty hard in top gear. I shift from 5th into 3rd and sometimes into 2nd. Hard on the anchors but no discernible feeling of ABS kicking in. Am I missing something? Am I just a *****? Should I be feeling ABS?

Here's a fairly typical mid week pratice/open track day. Feel like I'm driving ok but at no stage do I feel like I'm hitting ABS at all. Fighting a bit of understeer but we all have to deal with 'stuff'.

My dilemma is whether to spend a bit of money having it retrofitted to an older car that doesn't have it. There are so many schools of thought or opinions. Some say learn without ABS and I'm sure I can drive without, but if it's faster with why should I?

http://www.youtube.com/watch?v=TS1paBN8yko

SundayDriver

Floating rotors solve a couple of problems. So if you are having those problems, they may be worth doing. No problem, then why bother?

Pad knockback - I you are experiencing this problem, the floating rotors will help. This is where the brake pads get pushed back under cornering loads (or loads over curbs). When you step on the brakes, you have a long pedal, but the brakes come back after one pump. Usually happens very consistently at the same places on the track. This is often caused by worn bearings or other worn suspension parts, so you should always start there, rather than jump to floating rotors. Knockback can also be solved, in some cases, with a residual pressure valve which is a lot cheaper than floating rotors.

Pulsing - Some people claim that floating rotors help in this area. Maybe. Most pulsing is caused by uneven pad deposits on the rotor and floating rotors will not help, in this case. If pulsing is caused by slight warpage or out of 'true' conditions, then it will help a bit. But if it is warped rotors, they will just get worse and worse and should be replaced.

IMO - Use floating rotors if you are fighting pad knockback and the residual valve won't fix it.

cobrien

My opinion, for what it's worth (very little!): I've had one piece and two piece rotors (both fixed and floating). One of the main advantages to the two piece design is that you can replace the disc but re-use the hat, which in theory saves some money. They're also typically lighter because the hat is generally made of aluminum, which is nice, particularly since it's unsprung weight.

I don't know if your track car is also a street car, but if so one thing to keep in mind about floating rotors is that they're noisy. They clank and clatter over bumps and uneven pavement, which can get annoying (at least to me ). But as SundayDriver said, they definitely solve the knockback problem. So if you have that issue, floating rotors are the way to go. If not, personally I'd opt for a fixed 2-piece or one-piece rotor.

There are lots of opinions on ABS. In my experience, cars stop better if you stay out of ABS. In an ABS-equipped car on track, my goal is to brake right at the edge of ABS. If I feel it engage, I immediately ease off a little on the brakes to get the car out of it. That said, I race with several guys who intentionally use ABS all the time, and they do pretty well. But staying out of ABS results in better braking, and also seems to go through pads much less quickly.

One advantage of ABS, though, is that you obviously don't have to worry about flat-spotting a tire, since the system won't let a wheel lock up. So from that standpoint it's nice to have in cases where you screw up and are too heavy on the pedal.

333pg333

Thanks for those answers guys. That does help. I have not actually seen or used the term Knockback before but some of the symptoms Mark describes are what I've experienced. Occasional bouts of long pedal and the ensuing pumping of pedal-fix. In fact I have a habit of pre pumping my brakes quite often and I think this is due to long travel and also older cars that responded to this. I think this is actually a bit of a bad habit of mine and makes my first application of brakes not exactly as I'd like.

For us, the cost of hats and rotors out of the US is not much more than some OEM pricing so I am going to give these a go. My only slight concern is the thought of being wed to this company's rotors due to the hats probably not fitting any other brand of rotor.

With the ABS issue I think I must be too soft on my brakes and am not getting into the ABS, or being a very old version of the Bosch ABS ('89 951) maybe it's calibration just doesn't respond as readily as more modern units. I suppose I could try and fit a much better unit, but I don't want to spend too much money on this road/track car. Leave it for another project. I can still have the one from my crashed '89 transplanted across to the new 951 but this takes time and time = money so that's my dilemma??

jakermc

I switched to 2 piece rotors on my 996 for a different reason - weight savings. 5 lbs per corner in the rear and 3 lbs per corner up front. A 16 lb reduction in unsprung, rotating mass is a noticeable change. Overkill for a street car perhaps, but a worthwhile upgrade for a full time race car.

67King

Yes, all positive. Prior to 944's, I was into Merkur XR4Ti's. There is almost no aftermarket for them. So I had to fabricate stuff. I used COleman for a few things, such as coil over parts. I had planned to have them make hats for me before I ended up finding out just how bad the rust was on my XR (which prompted the shift to 944's!). I have a friend who has an AI-X Mustang who has used them extensively, as well. You may also find some good stuff from Lefthander Chassis. Circle track aftermarket is a very cost effective way to get good stuff, especially if you have the ability to tweak any of it.

333pg333

Yes, the reduction in unsprung weight is a nice bonus too.

I would like to be able to purchase replacement rotors down here if they're available, but from what I can tell basically when you buy hats, you can only use those rotors as others won't fit?

ninefiveone

I agree with cobrien. Cars stop better when you're not getting into the ABS. It sounds like you're assuming that ABS braking is better then non-ABS. Just not the case. It's an easy misperception to have. Think about it this way. Which is more effective braking? Being at the threshhold of lock-up but never locking up.... or locking up-releasing the brakes-locking up-releasing the brakes?

Remember what ABS is. ABS is a safety feature, not a performance feature.

That said, I can see it being a lot easier to just lean on ABS in endurance racing. Not faster but definitely a lot easier.

333pg333

Oh sure I get the concept. My concerns are with flat spotting expensive tyres. We pay double what you guys do for the same tyre down here. Also, if ABS isn't a performance tool, then why do virtually all race cars have it and why do Bosch and other companies continue to develop it? Price one of their current raceunits and it's scary. I don't particularly want to be just leaning on ABS at all. I just wasn't sure if I would be able to feel it working at speed as opposed to coming to a dead stop. The other part of my dilemma is that I will be having two cars stripped and parts exchanged from the crashed car onto the new donor car. So obviously that would be the time to do a transfer if that's what I choose to do. From what I read here ( http://tiny.cc/7hjqW ) it's a long process that = $$ for me as I won't be doing it. So I can just leave it off and then regret it as I flat spot a set of $1200 front R888s or go to the trouble and cost of doing it now....

Oddjob

Patrick, this is a few of my thoughts on ABS from a previous thread on the subject:

My point was that, having raced with and without, I much prefer ABS on a track car. And the 944 ABS system, as old as it is, still works ok.

333pg333

Jim, yes I knew you are an advocate of even our ABS and I would say I am also, just from the lack of flatting expensive tyres. In your opinion, how long would you estimate it would take to switch it over from one car to an other?

Larry Herman

As far as your driving, it looks nice and smooth, with some aggression. Remember, just because you have a lot of braking ability doesn't mean that you should use it at every corner. In seeing that track, I'd say that there are only 2 corners (the 2nd one after the straight, and the one before the Sidney bridge) where you should be at maximum braking. I'd try ramping up the brake pressure a little more for those corners, and if you find that you can, then move your braking point later. Everywhere else, if you over-brake or upset the car, you will be slower.

333pg333

Not quite the Sydney harbour bridge Larry but I get your point. Although I think it's the RH corner after that bridge that is the heavier braking corner? Downhill hairpin.
For some reference, into turn two I'm doing about 90-95mph at the 200mtr marker. At about the 150 space I back off the gas and at the 100m marker I'm doing 85-90mph and am then getting on the brakes. Does this seem reasonable? I can't imagine going too much deeper to then hit the anchors harder, but this is what I want to try. See if I can do it without upsetting the car too much or losing speed out of this double apex off camber hairpin.

I think I should get some data for my brake cadence and tps type of thing. In my mind I'm struggling between the concept that I should be braking a little later but with a harder initial application Vs losing too much momentum by doing so. As ever, it's all about a happy medium. The old mantra of trying to be either hard on the brakes or hard on the gas rings loud, but clearly there are times when you need to modulate both. Trail braking for example to me is a more gentle application, so is some of those Left foot taps to bring the tail around. Equally when you're going through a corner that you know the limit to it and your car's adhesion, you can feather the throttle until you feel it's good to go 'Mash' and away.
Turbo cars are another thing to take into account. 2 wheel drive and old suspension design with a decent amount of boost also comes into play.

Here's another few laps on the same track having a bit of fun against one of the new GTRs. Unfortunately I was fighting a pretty severe suspension issue this day, but still had some fun!
Pity about the camera angle too. Out of turn 3 the GTR was 4 wheel drifting and it's a shame to miss that just to show that this guy wasn't hanging about.





http://www.youtube.com/watch?v=cqeqtJYf6CI

924RACR

Regarding ABS use on track, tuning, etc...

On track, I would definitely recommend staying out of ABS, just braking right at the threshold as previously mentioned. Multiple reasons for this. First and foremost, it trains you to be aware of what's going on, so that you're not totally reliant on the system, and can still deal with the situation if/when it fails. Which is apparently not all that uncommon on the older systems (like the 951), on rumble strips!

Secondly, there's the subject of smoothness. While no smoothness is needed getting on the brakes, and so ABS helps you with braking distance there (no technique needed to get the tires to locking pressure quickly and accurately), the car (brake pressures) will not IMO be very well integrated when exiting ABS, after turning-in, so the car will not be as stable as it could be - namely, if you were threshold braking. So it could really hurt your apex speed. This is decidedly more relevant for the older ABS systems; I know of a car where we spent a great deal of time dialing that in for a very linear, natural transition out of ABS back into partial braking control, specifically for the corners on the racetrack, but sorry, it's not a Porsche, it's not even German!

So, I'd be concerned about how the weight transfer and brake pressures juggling around when transitioning into and, more importantly, out of ABS control would be upsetting the car.

Finally, the issue of the age of the unit - not the physical age, but the age of the software. Sure, the fundamental problems ABS solves hasn't changed in 20-30 years, but the tires and chassis certainly have, and so has the software. It's much more refined these days, both in logic and tuning. We can get cars to do things that were almost inconceivable 20-odd years ago - consider how incredibly docile the supercars now are on the street in daily driving. Likewise, what we've done with the chassis on our track/race cars, and the tires - they've wandered far enough from stock and the hard tires that were available then, that while the system may work OK and be safe - I'd question whether or not you can really get optimal performance from the system anymore, with stock tuning.

Maybe I'm a little biased too, because not only do I get to work with the latest technology, but I also race a non-ABS car. It'd be nice to have all that technology at my fingertips for the racetrack, sure, but not necessary, and no production system is going to be as good on a modified car as I'd like it.

I'd also point out, you don't necessarily need max decel every time you go to the brakes, right? Sometimes it's also nice to leave a little on the table. After all, braking points are about the last place on the track where you're going to pick up speed - and on the order of 100ths of a second. But if you stop trying to set your hair on fire going into the corners, and focus instead on apex and exit speeds, you might well stand to gain on the order of tenths to half a second. Per corner. Much bigger returns there. (Disclaimer - I haven't watched your video specifically, this is somewhat of a general answer)

So I wouldn't worry about when you are/aren't getting into ABS, etc. I'd say if you're going to pick apart your driving to that degree, get a data system and do it in earnest.

67King

I don't think they manufacture their own rotors. They might buy unfinished ones and machine the bolt pattern or slots into them, though. Regardless, they do complete custom jobs. YOu can have them machine to whatever bolt pattern and hat height you want. If I were you, I'd pick up some rotors that you find are accessible, and then design the hat to fit that spec.