SAU Circuit Times

[Scotsman]

Now that's just boring Bris... Nice essay.

It's pretty hard to estimate distance, but the kind of brake fade I was getting was causing me to brake about 10m earlier than I would have liked on turn 8, 20m earlier on 10 and 30m earlier on turn 1.

=60m. So what does that equal in time lost over deacceleration + plus lost acceleration?

[Roy]

It equals not enough talent.

Watching your footage, it did the 1:06 far too easy. I wouls say with brakes fixed, new semi slicks and a good lap, the thng will do high 1:04s. Its friggin amazing how much time you pull at the slow left hander up to the quick right hander on the back straight!!!!!. It seems the baby GTSS equiv Garretts are thge turbo to have around Wakefield along with cheating transfer case and front diff.

[Snowman]

It equals not enough talent.

Watching your footage, it did the 1:06 far too easy. I wouls say with brakes fixed, new semi slicks and a good lap, the thng will do high 1:04s. Its friggin amazing how much time you pull at the slow left hander up to the quick right hander on the back straight!!!!!. It seems the baby GTSS equiv Garretts are thge turbo to have around Wakefield along with cheating transfer case and front diff.

What? You're giving him basically 2s based upon slightly better rubber (there was nothing wrong with the other stuff) and better brakes. No Way.

I don't see him cracking into the 1.05's. Plus even if he does go back there with better brakes you know he'll just end up trying to hard and will go and find a cone or something to hit.

[Roy]

LOL…watching the footage shut me up. LOL…get him to post the footage with Fermi…the lap looks a long way from being good let alone perfect. If Scotchfinger could drive then the lap would have been a ripper. I don’t think the brakes were hurting him a whole lot. But the driving and grip seemed a big problem. I will bet money he can do 1:05s.

[Scotsman]

Hehe - got you talking now.

Come to the club meeting and I will reveal the footage.

When I went back to cabin to capture the footage on my laptop, I was amazed at how bad a lap that actually was. But I think if you drive eratically and past the point of smooth grip at wakkie it is actually quicker.

I think a 1.05 will be relativly easy on new rubber. You have to remember it was also slightly damp too.

[Roy]

My first reaction was that someone had grabbed his lap timer and shortened the track, so when he replayed it for like the 3rd time, i was paying attention to when the timer reset...it looks like a straight up, messy and fark, lcrappy mid corner speed, crossed up on corner entry lap that somehow bagged him a 1:06.7?!?!?!?!

Fix your front diff Snowdaddy

[djr81]

Well depends on what you mean by not being able to brake 100%? Firstly, if i want to be a dill, i doubt you should even be braking 100% every brake application. Its a recipe for locking brakes, missing apexes, carrying a bit too much speed on corner entry and in turn hurting corner exits etc etc. You need to brake as late and quickly as possible, but you need to be able to do it consistantly over a lap which to me means i always need to keep a little up my sleeve when braking.

For almost all of this year i have had trouble stopping the car...in my case because my car used to pitch so much under brakes the car would wobble everywhere. So i wasnt braking 100% because of a stability problem, more then a brake fade thing. Is it the same outcome/result? Depends on how bad the fade is i guess, but it did hurt braking a lot

Then going back a few years i had a problem with bad pad knock off so i did a day at the track where i was left foot braking and forever pumping up the pedal as i had a really soft pedal....wasnt nice but i think i still did a 1:56 or something (remember the day you and i had a woopsie at Honda/PI...the car still stopped fine even though going by the pedal it was horrible) Then a few weeks later had the same knock off problem at Sandown but still did a 1:24. That was my first time there in the dry so dont know if it was costing me time.

But you are right, generally i have never really driven too many cars that struggle for brakes. Even when my car smoke the std 280mm rotors it was still stopping fine.

But here is the thing. Im not saying i am 100% right, or even partly right. Just sounding off on some thoughts from what i have experienced, what i have read and what the data logger tells me. if your experiences tell you different then go with that.

I have read (???? i have never had to qualify / race so i would not know???) that braking is the easiest place to lose time and the hardest place to make time. Also, the feel of what your brakes are doing, or not doing greatly impacts on your perception of how the car is actually stopping. Because you dont have the retardation that you expect you think you are losing time, reality is you are actually walking up to the corner quicker...ok you tend to jump on the brakes to wipe off speed a little earlier which counters this. But its a trade off. What feels fast is not always fast, what feels slow is not always slow,

Case in point is when you sit back and look at the info i get from my data logger. Its surprising how small the improvements are when you brake later. You see over the day as i brake later and later the times dont really improve. What helps the times is when my corner speed improves. With me driving braking later doesnt automatically mean better corner speeds. So for me (my driving style) the data tells me that braking later does little for my lap times.

Whe i first started reading the data this puzzled me a little, and wondered why this is the case and started to think aboutsimple motion euqations, v=u+at. V is final speed, u is initial speed, t is time and a is acceleration (-ve as we are decelerating, this is all greatly simplified as it assumes acceleration is linear, which it is not, doesnt take into consideration a whole bunch of things but still makes a point)

So say your car decelerates/brakes at about 6m/s2. And you brake a full 1 second earlier. That braking 1 second earlier increases your braking distance by a huge amount since say at the end of Sandown you are travelling about 65mtrs per second. Now as far as elapsed time is concerned....braking 1 second earlier means you have lost 1 sec of acceleration and say you are now travelling at 198km/h rather then the 230km/h since you have been braking for 1 second already. So that 32km/h equates to about 8mtrs per second. So the time you have lost is the increase in time it took you to cover that 65mtrs whilst braking from 230 to 198km/h rather then reavelling at 230km/h. I had a spreadsheet on my old lap top playing with some basic equations / plotte dgraphs then the more complex braking equations. But...like i said, its all theory mixed in with a little practice but of course you lose time by braking early, but the old watching the cars at the end of the drag strip help reinforce the point. A car that is only 5/10s of a second quicker over the quarter mile passes the lines many car lenghts ahead of the slower car, yet it is only 0.5 seconds slower. Now can you imagine braking that distance later to try and make up 0.5 seconds? Even over a number of corners?

But, that all said, no doubt that if the brakign performance of the car is suffering then there is to be an improvement with a brake upgrade. Im just yet to be convinced that it is in the magnitude of seconds, all other things being equal:spam:

So, welcome the thoughts of others.... im happy to be proven wrong if it means i end up with the facts

Some randon, um ramblings about brakes:

Of the three parameters, corner speed, acceleration & braking as they relate to lap times braking is the least important. This is fairly self evident. Corner speed is the most important because you gain time in the corner & then all the way down the following straight.

Acceleration is the next most important because you gain an advantage for the length of any straights.

Braking is the least important because the distance travelled under brakes & time spent is usually the least of these three parameters.

But.

The but is that most people suck badly at braking. So whilst it is the least important thing it is also the thing people do least well.

Most Skylines without brake upgrades but on R compounds will not lock their brakes unless the car is doing something else, eg cornering, unweighting wheels over bumps.

So from that perspective you need to use all of the brakes capability. If you are only doing a 3 lap run there is no reason not to punish them as hard as you can.

With regard to technique it is here that people come unstuck. Common problems are:

Not braking hard enough at the start of the stop. It is much harder to lock a brake at high speed than at low speed, so you should mash the pedal at the start of the stop.

Ineffective brake modulation, particularly during heel/toe downchanges. Check you data log - how much of the brakes capacity do you use over the whole of the stop?

Poor modulation at the point of turn in. This upsets the car & your corner speed.

What annoys me greatly is when people claim that with a change to one component of their car they will make large gains in lap speed. Tyres are the most influential but people tend to over estimate even this. Rest assured that if some clown is claiming his fully sick carbon fibre wang extender will make the difference the most probable result is that it wont.

On the flip side, poor driving can easilly lose large lumps of time. Consider this. An average Australian circuit is 2.4 kms (1.5 miles) and can be lapped in of the order of 1 minute. Which equates to 90MPH (144kmh). A 59 second lap is 146.4km/h. So a miserable 2.4km/h is worth a second. So yes, you may only be going a small amount slower than you might otherwise, but that is all it takes to drop lap times from winning to trying hard in the midfield. If anyone has any experience of the former, please let me know because I spend my time doing the latter.

If you have a logger you can use the equation listed in Roys essay to estimate changes in lap times. Just use the data in each cell rather than averages which can be misleading. Also in terms of distance, not time it can be expressed as v squared = u squared +2*a*s where a is the acceleration & S is the distanc travelled.

Here is some logged data showing the braking gess of two different set ups. No prizes for guessing which of the two had the brakes behaving badly. None the less even the better one has plenty of room for improvement. No where near 100% of the capacity as was said.

brake_gees.PDF

[Roy]

Most Skylines without brake upgrades but on R compounds will not lock their brakes unless the car is doing something else, eg cornering, unweighting wheels over bumps.

Is that right? I know my car can easily lock brakes when i first jump on the pedal coming off the straights of Calder and Sandown etc. You are doing well over 20km/h in each case... though i dont have ABS. Even after doing my susp upgrade i still need to show the pedal a lot of respect with the Endless pads i currently run. They are brilliant lap after lap..though they do seem to be killing rotors

[djr81]

Is that right? I know my car can easily lock brakes when i first jump on the pedal coming off the straights of Calder and Sandown etc. You are doing well over 290km/h in each case... though i dont have ABS. Even after doing my susp upgrade i still need to show the pedal a lot of respect with the Endless pads i currently run. They are brilliant lap after lap..though they do seem to be killing rotors

Um I dunno then. Mine certainly won't. There is no chance that if I fire over the hill at Wanneroo & plant the middle pedal the anchors will lock. No chance at all. That is with 0.5 mu friction coefficient pads in it. There again you thing is probably lighter than my lard arse GT-R. Sure it is not the bumps at Calder?

I routinely brutalise the brakes in my car & the only flat spot I get is on the ball of my foot.

So who knows any more?

[Roy]

LOL...anyone else? Thikning back i have probably bought about 7 or 8 sets of semi slicks over the years and only my old Dunlops survided their whole life without beign flat spotted. My car i always have to be careful not to lock brakes...with racey pads its so easy if i jump on them instead of squeeze

[JAGR33]

Interesting discussion with some very useful information.

I can say that I have had the ABS kick in at Calder, I'm doing about 255km/h before mashing the pedal at the 200m mark.

I have the Alcon kit front and rear with Ferodo DS3000 pads, so I'm not surprised.

And Roy, you get to 290km/h at Calder and Sandown???? DAAAAMNNNN THAT'S FLYING!!!!!

[Duncan]

no I don't lock the brakes in the race car either, ABS has almost *never* kicked in on that car (although the 32 abs was pretty generous). I've never routinely triggered it. Used to be able to brake right to lock up/abs on the gtst though.

[Roy]

And Roy, you get to 290km/h at Calder and Sandown???? DAAAAMNNNN THAT'S FLYING!!!!!

LOL, typo, was meant to be 190km/h

[Ant97GTR]

Interesting discussion indeed.....all I can add is that I feel like I do not hit the brake pedal as hard as I could at first. I only seem to trigger abs 1/2 through a hard brake and this only happens at 2-3 circuits I have been two. Whether this is attributed to lack of talent by not modulating the brakes enough or bumps etc on the track I am not sure.

Oh and Troy thanks for updating the times but you missed my last winton and wakefield time posted on page 36/37

[Scotsman]

I'm pretty sure I can lock the standard brakes on mine at high speed if I want to with brand new 245/40/18" RE55's with the following setup:

Cusco master cylinder stopper

Braided lines

Motul 5.1 fluid - I bleed one bottle through before every track day

DBA 5000 slotted fronts (Standard 324mm)

Ferodo DS3000's

V-spec rubber brake ducts

Removed backing plates

Even on a good surface. But I do need to jump on them very hard. Which is exactly what I do at Sandown.

I'd also like to say that it's my experience that the GTR standard brembo's are great until you reach 300+kw and then they don't seem to be able to cope with the higher speeds i'm approaching braking points at. I could do laps of Sandown/Winton all day with 260kw and never have a brake fade and still get 21's and 35's respectivly.

I'm only now feel I have reached the limits of the standard caliper and disk size.

[ferni]

I think it's worth trying some fancy ducting/cooling on the standard brakes. Even if it doesn't work, it will still be beneficial when you do upgrade brakes.

[Roy]

Wah, wah, wah...enough crying from the VIC GTR boys already! Not having enough brakes? Serves you right for building NASA space shuttles then forgetting the parachutes

[Scotsman]

Yeah that's the next plan Ferni as you know. Because lets face it i've done everything else.

Shut up bris. At least i've gone to edge and found the limit, rather than just going out and buying a full package because I might be running out of brakes soon. And now I can share that information with other track users. "GTR brembo's = good for under 300kw car." You know I like to see what the limit of things are just like you. I believe we also found the limit of the stock turbo's around Sandown and Winton...

Next we can see how far brakes will last with a spacer and a bigger disc.

[Roy]

Next we can see how far brakes will last with a spacer and a bigger disc.

Dont forget the wing nut...or was that tighten the loose nut? :laughing-smiley-014:

You have done well with your car and been good to watch it get punted with the gear its had on it. Has been a good yardstick for std gear vs mods. No matter who it is driving and what car it is driving i think it gets crazy expensive the minute stop watches come out

[fatz]

well kids im finally back to causeing trouble at the track

wakefield 4th december im excited!!!!!!!!!!!

so i can you all camp again

and soft at breaking!