First Autocross

[mike223]

Wife is quiet for a minute or so, then makes a couple of comments, and ends up saying, how the he11 did you do that? I guess decades of AXs have paid off haven't they.

Classic story.

The car control I learned from autocrossing a Vega GT a few years in the early 1980s has served me very well over the years in very similar ways.



Interesting you couldn't find a way to get it settled down @ 335x315


I was pretty comfortable in my gokart on 315x315 V710s (after going to stiffer front springs).


Of course I probably should add I prefer them a little loose too.

[J R Jones]

Old Bull teaches young bulls? Yeah with experience there is also wisdom. At 73 I recognize my physiology is not what it was, and neither is my invincibility. However, when it comes to driving and/or flying, naturals exist.
If this thread has devolved into bench racing, read on.
In high school, the class I excelled in was drivers ed. One of my first on-road lessons was in January on snow covered WI roads in a 1964 Chevy Biscayne four door sedan, six cylinder and three on the tree. Two students in back; Mr McFarlane in the passenger seat. I was just into third and pressing for speed when the rear tires broke and swung to the right. Feather throttle, counter steer, recovery, all before Mr M could comment. Unlike my father he was cool about it.

Four years later I am just returned from a USAF tour in Asia and enjoyed Christmas leave at my folks WI home with a TX buddy Hector Rocha. We have to be at Selfridge AFB by morning. "There are 300 miles to Mt Clemons, we have a full tank of gas, half a pack of cigarettes, it's snowing and we're wearing sunglasses." No problem, this is a '66 Shelby GT350 and I am invincible.
There is a phenomenon at the base of Lk Michigan called "lake effect". The snow can be and was, wet, heavy and deep. On I-94 there are no snow plows in sight.
Following an 18 wheeler at 60MPH the pavement is wet strips with a snow berm under the car and snow berms between lanes. The tire spray is filthy and annoying, I go for a pass and traverse the berms into the left lane. Accelerating on the wet I pass the truck and attempt a lateral back into the right lane. The front tires are deflected to the right by the center berm and the rear comes around to the left. Hector and I stare out the right window at a huge chrome radiator shell with KW at the top. I hear "Hail Mary Full Of Grace". Both axles are now on the wet paths as I steer left with the throttle feathered, but not closed. Simultaneously the front went left and the rear fell in line. Other than profanities, I do not remember much discussion.

As mentioned earlier in this thread, that Shelby was later autocrossed, but not always on pavement. Ice racing is popular in WI and the SCCA had a winter event on Browns Lake near Burlington. That was a treat given the course length and speed. The main straight paralleled an island. With four snow tires I saw triple digits, when I could focus on the heaving speedometer. jim

[Avalanche325]

a Vega GT

If that won't make a Ford man out you, nothing will. My first TWO cars were Vegas.

I'm surprised that there is a mention or high oil / water temps during autocross. I have never seen anything past normal street temps. Even on a road course autocross. I live in northern FL. I run a little hotter on the track of course.

One thing, for both autocross and track, warm the water / oil up before your session. That includes if you take a break and have an afternoon session.

I am also in the loose is better than tight camp. You can get the car to do either depending on the situation. I find that the car is pretty easy to adjust with the throttle, but you have to be smooth with it. Everything happens faster with a short wheelbase.

I highly recommend autocross before open track. You want to exceed the limit and spin or plow straight through a turn with cones, not concrete and armco. I always always try to drill through my head not to go over 9/10s on the track. 10/10s is for autocross only.

SCCA Track night in America is a good way to get on track for the first time. Inexpensive, and not too many sessions for the first time. Like stated, it will wear you out the first time. Not just muscles, but 110% concentration makes you tired.

[mike223]

If that won't make a Ford man out you, nothing will. My first TWO cars were Vegas.

They actually worked pretty well, I was usually beating all the Corvettes.

It was all fun + games until you scuff an aluminum cylinder wall.

Early eighties I was buying them (cheap) just for the engine - when I could find one that didn't smoke...

[mike223]

I'm surprised that there is a mention or high oil / water temps during autocross. I have never seen anything past normal street temps. Even on a road course autocross. I live in northern FL. I run a little hotter on the track of course.

I'd say I run autocross 9/10s - maybe 10/10s on the last couple of runs.

I rarely get oil temp up to water temp out on the road, but by the second 50-60 second autocross run it will be 10 degrees (F) above water temp, which I consider Ok.


I put an oil temp gauge on a Pinto (2300cc) I had in the Navy. It rarely got oil temp up to water temp - took at least 30-40 minutes of interstate driving to get there on a warm day.

Driving back east from the west coast it cooked the oil pulling up the continental divide (approaching 300F) - had to pull over and give it a rest around 5500', and again somewhere around 65-6700'.

A lot of people say oil temp is rpm based - I say it's load based.


I have no need for an oil cooler for autocross - but I'd be watching it like a hawk if I was driving 7/10s for 20 minutes on a road course.

[Avalanche325]

One thing is that it seems like every car is different when it comes to cooling. Some guys with a 347 complain that the overflow tank is too small. It has been fine for me. Others seem to want to overheat. I haven't had an issue. So, definitely keep an eye on it to see what your setup needs.

What I have for autocross / track is an idiot light that does dual duty high oil temp / low oil pressure. There is zero time to look at gauges during autocross.

Vega - mine got so bad (pitting around the top of the cylinders - open deck design) that when I started the car, it would pump water out of the exhaust before starting. Then take about 10 minutes to get all four cylinders firing leaving a trail of steam down the road. I used to keep 5 gallons of water in the trunk. If you revved it, you could shoot water about 6ft out of the radiator with the cap off.

[J R Jones]

Engine oil is most efficient when it is warm/hot/thin. OEM oil recommendations have been getting thinner. The oil must get to 220F to burn-off water vapor and deposits. The upper range for engine oil is 230 to 260F. Mineral oil will start breaking down at 275F, synthetics will go to 300F.
jim

[AdamIsAdam]

I converted over to Evan's Waterless Coolant. Jay Leno converted me. The stuff boils at 375*! And it doesn't expand nearly as much and the system is almost under no pressure. They suggest replacing your radiator cap with a lower PSI cap. I like the comfort of knowing my old style engines won't blow a hose if I get stuck in traffic in the summer. As for the FFR overflow tank, it likes to be about empty when cold. When I first got the car I added some and it puked it out. So I let it stay where it settled. That was before converting to Evan's. So with the less-expanding Evan's I'm sure my overflow size tank is fine now.

[GTBradley]

My 2nd autocross is tomorrow and I have made a plan on how to approach it. I’m taking input from the technique approach offered on the first page of this thread and will leave equipment changes and alignment settings for later. I’ll report back on my results.

Autocross notes

• Get to 2nd gear soon after leaving the starting gate and stay there - this reduces abrupt inputs and deceleration braking caused by 1st gear, which are resulting in snap oversteer.
• No sudden inputs on brakes, fuel, steering. This will reduce the rate of weight transfer.
• Left foot braking - this allows for more control on turn in and coming out of a turn. I expect this to be disastrous at first, but I need to learn it early.
• I have installed a heel stop in front of the gas pedal - I’m hoping this will help with throttle control - it certainly has on the street.
• I’m going to try 20 psi on the tires and use chalk on the sidewalls to see what the contact area is at that pressure.
• Accelerate all the way to braking, no coasting.
• Be tidy, not fast and get closer to the cones.
• Practice with knowing where the tires are on my 45 minute drive to the course, i.e., touching the rumble strip on the shoulder of the highway.
• Make notes.
• Have fun!

[AdamIsAdam]

HAVE FUN! looking forward to your next post.

[Jeff Kleiner]

My 2nd autocross is tomorrow and I have made a plan on how to approach it. I’m taking input from the technique approach offered on the first page of this thread and will leave equipment changes and alignment settings for later. I’ll report back on my results.

Autocross notes

• Get to 2nd gear soon after leaving the starting gate and stay there - this reduces abrupt inputs and deceleration braking caused by 1st gear, which are resulting in snap oversteer.
• No sudden inputs on brakes, fuel, steering. This will reduce the rate of weight transfer.
• Left foot braking - this allows for more control on turn in and coming out of a turn. I expect this to be disastrous at first, but I need to learn it early.
• I have installed a heel stop in front of the gas pedal - I’m hoping this will help with throttle control - it certainly has on the street.
• I’m going to try 20 psi on the tires and use chalk on the sidewalls to see what the contact area is at that pressure.
• Accelerate all the way to braking, no coasting.
• Be tidy, not fast and get closer to the cones.
• Practice with knowing where the tires are on my 45 minute drive to the course, i.e., touching the rumble strip on the shoulder of the highway.
• Make notes.
• Have fun!

Sounds like a good plan however I might start with a little more pressure, say 22-23 and then adjust down accordingly as they heat up and you see what the car is doing...if it's loose bring the front down 1-2 or if pushing bring the rear down 1-2.

Whatever you do make sure that you fulfill that last bullet point

Jeff

[GTBradley]

RMR Porsche club autocross event #2 - video


2nd AX.jpg

Last bullet point fulfilled! We had a cool day that threatened to rain all day but never did, so it turned out perfectly. Though, I was interested to see how my tires would perform in the wet stuff as it is very common for the other drivers to have the sticky aggressive type, where I only have the Nitto 555s, which are just a performance summer tire.


The plan was stated above and I mostly stuck to it at least for half of the runs, but I altered my procedure back and forth through the day. Here are my impressions and results.

• Second gear - it is intended to be easier for throttle control, but as I found out it is very track dependent. The last AX was a fast track and 2nd gear would have helped, but this track was short legged and took a full 10 seconds longer to complete even though it was laid out in the same space. Half of my runs were in 2nd gear and half in 1st and the fastest times were all 1st gear runs.
• No sudden inputs - I did my best but this is very dependent on experience, so I’ll keep at it. My biggest issue was heavy late braking.
• Left foot braking - overall this was a wash as far as my times go, but I do consider it a success because the learning curve wasn’t as bad as I thought and it will be helpful later to shave tenths of seconds off my time. Right now I need to shave multiple seconds.
• Heel stop - I highly recommend this, it does actually stabilize my foot and throttle application.
• Tire pressure - this may have been an issue at 20.5 psi considering our ambient temperatures were in the mid 60s. I’ll probably go back to 22 next time.
• Accelerate to braking - I tried to accelerate all the way to braking but I wasn’t braking soon enough on hard turns. And I also found that sometimes it’s hard to continue accelerating or start braking yet. It still isn’t coasting but more a steady state throttle that carry’s you through the section to the next braking for a turn.
• Be tidy, not fast - I have a lot to learn, I think. It turns out my messiest runs were the fastest ones and the tidy ones were the slowest. I suspect it is a balance between the two that gets the best times?
• Being close to the cones - Cones…schmones! I’m too busy with everything else to do anything different there. However, judging from the videos I think I did alright and yes, I did tip a couple. I even hit one without knocking it over.
• Notes - check!
• Fun - check-check!

My performance improved over last time judging by my placement: 47th out of 75 this time and 48th out of 71 last time and there were a lot more first-timers last time. It’s not a major improvement, but it’s something.


I had hoped the course would be the same this time to compare, but it had roughly twice as many direction changes and that leads me to think that it favored cars with better tires and suspensions. There were no long straights this time. This is also why I think first gear was an advantage this time. RPMs topped out in the high 4000 range where last time I was in the high 5000 range, both in 1st gear, of course.


I had sloppy runs on my fast times with major understeer brought on by late braking. I could have saved significant time had I not done that on a number of turns. I didn’t include the tidy runs in the video, just the fastest ones with the most mistakes. The second video is a bad one as the video camera is tilted down, but there are things to see there and it is the fastest run, but I tipped a cone so it doesn’t count.


All in all, a good day, but I did find that I was frustrated that I couldn’t change my time significantly throughout the day. I did only have one DNF, so that’s an improvement. I can’t help but feel that the tires and possibly the anti-sway bar would have made a big difference on this track and I’m leaning toward doing one or both of those improvements sooner rather than later now.


Let me know what you think.

[D02G]

Very cool

[Jeff Kleiner]

I still say it's pushin'

Jeff

[J R Jones]

Brad, I feel bad that perhaps you had information overload. In an effort to maximize effect maybe you initiated too much at once.
Among things I am not is an educator, but a suggestion is a list of techniques to learn and a series of steps. Tape one or two steps to the dash as priority on that run.
Yes if a prior step becomes a natural response, fine, but focus on one or two things per run.
It looks like you are running in fast company.
jim

[GTBradley]

I still say it's pushin'

Jeff

I agree. And you suggest more seat time, right?

[GTBradley]

Jim, I just chose the things I wanted to focus on. It wasn’t really more than left foot braking, accelerate to braking and smooth inputs. I’m not good at those things yet but I did feel I improved some.

It is some fast company. The guy with the best time was in a 2020 718 Porsche GT4.

[AdamIsAdam]

Glad you had fun. Sounds like the course was very tight.

I hear more seat time can help 😁

[CraigS]

That is a shame the course was so tight. I hope they get another designer for the next one. I think you have diagnosed your driving quite well. Being king of the late brakers doesn't work so well as you found out. Long ago a friend made this point. On any given turn you have to give it up somewhere. In autocross, slightly erring on the side of going in too slow is always better than going in too fast because the center of the turn will be faster and so will the exit. What makes it so hard is the sound at full throttle is sooooo good. Here is another concept, trail braking. For me what this means is you don't fully release the brakes until a little later. IE; you don't go from 100% brake to 0% brake. You come off the brake pedal more like 100%, 75%, 50%, 25%, 0%. Why does it work? A tire has a certain amount of traction. There is a slight difference but, for the sake of discussion, let's say that traction is available in all directions. On corner entry you will transition from full brake traction to mid corner full cornering traction. So in the above listing of %s, more detail would be 100%B (brake) has 0% C (cornering). 75%B = 25%C, 50%B = 50%C, 25%B = 75%C, 0%B - 100%C. It's is similar but opposite to adding throttle on corner exit. You can't just slam down the gas pedal, you have to squeeze it on.
Trail braking is quite hard to get right, but when it happens it is magic. The next time you go in too fast, instead of coming off the brake all at once, hold partial brake for an additional 30-40 ft. One more thought. Better tires will get you better times but can actually be detrimental to building skill. I would experiment w/ bars or springs before going for better tires.

[Jeff Kleiner]

RE: Craig's education on trail braking (which is excellent)---this is where left foot braking comes in because you can work throttle and brake against one another as sort of a "buffer". I bet if you watch some of the fast guys you'll see their brake lights are on even when they're coming out of turns and accelerating. There is a learning curve...I resisted for a long time but as soon as I got serious about doing it there was a "Where have you been all my life" moment!

Here's another explaination of the "Traction Circle" Craig is talking about:



Jeff

[J R Jones]

Brad, After sleeping on this:
The "friction circle" was first described by Mark Donohue in the seventies. Maybe the method was used before then, intuitively.

This course adversely affected your strategy which suggests a pre-race effort was appropriate to formulate a "game day plan". We discussed previously the optimization of corners to take advantage of the the straights. In the absence of straights, the strategy changes. You attack chicanes differently than corners coupled to straights. Your course description suggests this was a series of chicanes and slaloms. Perhaps the key on this course was maintaining and modulating a somewhat constant speed and throttle/brake control vs accelerating from corner to corner. Visualize minimized pitching with optimized rolling from corner to corner. Less drama, more control.

Another issue....it is easier to identify your acceleration point from steady state, than it is from acceleration, simpler dynamics. You did not mention apex. Perhaps you should prioritize transitioning from throttle to brake to nail your apex under control, then identify enough stability to accelerate. Too much entry speed?

You write: "understeer brought on by late braking". I do not understand, the tires slid after you initiated braking? Is that brake proportion? Weight transfer to the front loads the front tire treads. Do you have ABS?
Maybe you just exceeded the traction with too much braking and steering at the same time (friction circle) but realize this was caused by too much corner entry speed.

Consider optimizing you ability to control and maybe adjust this configuration before you modify it with anti-roll bars. That will make evaluating the changes more valid. Setting up the car is a higher priority, and not the same thing as modifying it.
jim

[J R Jones]

I could not previously view the video, I just found a way. One video is worth....Jeff is right it sounds like the fronts are screeching often, even steady state turning. I feel the tire pressure is low. The front end seems unresponsive.
What kind of power steering is that? Is there feedback? What is the steering ratio? What is the source, Mustang?
10 - 2 steering discipline! Don't let your wrists cross.
Why do you not have a front A/R bar? Is that the default build? WT?
Is your brake proportioning optimized?
I do not like the roll bar video, is that on a gimbal? I can not relate to that perspective.
My cars are very different from this.

[GTBradley]

That is a shame the course was so tight. I hope they get another designer for the next one. I think you have diagnosed your driving quite well. Being king of the late brakers doesn't work so well as you found out. Long ago a friend made this point. On any given turn you have to give it up somewhere. In autocross, slightly erring on the side of going in too slow is always better than going in too fast because the center of the turn will be faster and so will the exit. What makes it so hard is the sound at full throttle is sooooo good. Here is another concept, trail braking. For me what this means is you don't fully release the brakes until a little later. IE; you don't go from 100% brake to 0% brake. You come off the brake pedal more like 100%, 75%, 50%, 25%, 0%. Why does it work? A tire has a certain amount of traction. There is a slight difference but, for the sake of discussion, let's say that traction is available in all directions. On corner entry you will transition from full brake traction to mid corner full cornering traction. So in the above listing of %s, more detail would be 100%B (brake) has 0% C (cornering). 75%B = 25%C, 50%B = 50%C, 25%B = 75%C, 0%B - 100%C. It's is similar but opposite to adding throttle on corner exit. You can't just slam down the gas pedal, you have to squeeze it on.
Trail braking is quite hard to get right, but when it happens it is magic. The next time you go in too fast, instead of coming off the brake all at once, hold partial brake for an additional 30-40 ft. One more thought. Better tires will get you better times but can actually be detrimental to building skill. I would experiment w/ bars or springs before going for better tires.

This makes total sense to me as we use the same concept in flight, as in, you can't have it all. In level flight you get all the lift but in a bank you share the lift with the turn, i.e., horizontal coefficient of lift. I'll simplify this one to brake sooner and don't come off the throttle suddenly, when it's time to start accelerating don't come off the brake suddenly.

[GTBradley]

In the video where he says, "you can't go right back to the static frictional coefficient" [by backing off a little], is so true and what I was doing was causing the unstick condition with heavy, late braking and starting the turn. I knew this, but as was mentioned by Craig, the throttle sounds sooo good, and truthfully the aggressive approach was lowering my times but limiting my improvement by wasting time trying to regain traction. This is where you start to rationalize that better tires would be so helpful, but this discussion makes it more clear to me that less sticky tires will help me understand the dynamics I'm dealing with.

I'm getting a lot of, "you're doing really well for not having ASBs" from other drivers at the track. And it sounds like they might be the first improvement to make to the car, so would it hurt to add those now? It sounds to me like the car could benefit from the back one to help with the "push"condition. Would it be detrimental to learn these braking concept with the ASB installed?

Edit: I just found this late 2017 discussion on suspension setup. Jeff, I just realized you aren't using anti-sway bars, or is that still true?

[GTBradley]

I could not previously view the video, I just found a way. One video is worth....Jeff is right it sounds like the fronts are screeching often, even steady state turning. I feel the tire pressure is low. The front end seems unresponsive.
What kind of power steering is that? Is there feedback? What is the steering ratio? What is the source, Mustang?
10 - 2 steering discipline! Don't let your wrists cross.
Why do you not have a front A/R bar? Is that the default build? WT?
Is your brake proportioning optimized?
I do not like the roll bar video, is that on a gimbal? I can not relate to that perspective.
My cars are very different from this.

I have the FFR supplied mustang power steering rack and don't know the ratio. I have installed the lowest boost valve that KRC offers for their PS pump. There is feedback but the steering is sensitive. No front or rear ARBs as I din't opt for that option until I could feel the car out without them. I am leaning towards installing them and leaving the front or back disconnected alternately to discover the benefits individually. Brake bias is to the front in my opinion and I do have the balance bar adjuster knob installed but haven't played with that much yet - thanks for reminding me. The gimbal was my head. I won't do the helmet cam again as it only works if you don't bump it bringing the shoulder harness overhead. I now have a suction mounted stalk on the rear deck.

[CraigS]

Yep good F to R brake balance is another of the finer points of autocross. My method; 40mph on a level road (watch for the crown) hit the brakes. Keep adding one more click of rear brake until you get rear lockup. The first time it happens you will understand why I say 40mph and no faster. It is actually sometimes hard to feel because the diff tends to try to keep both rear wheels going the same speed. When the rears lock you may feel the engine being stopped for an instant. So when the rears lock first go one click to the front and maybe one more. The good thing about bias adjustment is you set it for good optimum dry conditions. In any less conditions, you can't brake as hard, so less weight transfers to the front so the fronts will tend to lock first. Fronts locking first is what you want on the street because it is stable. You may even change adjustment by a click or two for AX and then back for the ride home. In a way though this proper adjustment is not really about locking the brakes, it is for braking at 98%. Testing when they lock is just a technique we can use. The real benefit is to use the brakes to rotate the car. Like trail braking, when you get it right, it is a wonderful thing.

[Mike N]

On any given turn you have to give it up somewhere.

If you can find out who the course designer is they can often give you good insight into where you need to 'give it up'. The course designer in the NNJ group I used to run with would often tempt you to run fast into a series of gates where in reality it would yield a faster time to give it up going into the first gate to get a much better line through the series. All part of the fun of Auto X.

[RoadRacer]

Yep good F to R brake balance is another of the finer points of autocross. My method; 40mph on a level road (watch for the crown) hit the brakes. Keep adding one more click of rear brake until you get rear lockup. The first time it happens you will understand why I say 40mph and no faster. It is actually sometimes hard to feel because the diff tends to try to keep both rear wheels going the same speed. When the rears lock you may feel the engine being stopped for an instant. So when the rears lock first go one click to the front and maybe one more. The good thing about bias adjustment is you set it for good optimum dry conditions. In any less conditions, you can't brake as hard, so less weight transfers to the front so the fronts will tend to lock first. Fronts locking first is what you want on the street because it is stable. You may even change adjustment by a click or two for AX and then back for the ride home. In a way though this proper adjustment is not really about locking the brakes, it is for braking at 98%. Testing when they lock is just a technique we can use. The real benefit is to use the brakes to rotate the car. Like trail braking, when you get it right, it is a wonderful thing.

Craig, thanks for this. I'm chatting about balance bar in another thread but since I'm doing my own first AX in 3 weeks I'll post to this thread too since it's relevant. How easy is it to lock brakes? I just rebled my car, and tried at 35 and 65mph and although the car seemed to stop very quickly, there was no lockup. I could have pushed harder or more violently but that doesn't sound a great idea . But if it should be easy to do, then maybe I need to get out and bleed some more. How does width and stickiness of tires factor into this? Seems it would be easier to lock up thin tires, but I'm not sure I understand the interplay between brakes and tires.

[GTBradley]

If you can find out who the course designer is they can often give you good insight into where you need to 'give it up'. The course designer in the NNJ group I used to run with would often tempt you to run fast into a series of gates where in reality it would yield a faster time to give it up going into the first gate to get a much better line through the series. All part of the fun of Auto X.

Unfortunately, this was a course design contest. I don't think anyone thought it was that great and expect they will return to the more normal course in the future.

[GTBradley]

Craig will give you the straight poop on this, but I can tell you from experience with wide tires and the big, Wilwood brakes it will lock up as soon as you want it to. The typical response to someone having trouble with lockup, after you investigate other issues like bleeding the lines of course, is to change the brake pads to something more aggressive.

[J R Jones]

Sensei say "Be one with your tires Grasshopper". Not that everyone can. Like a professional your senses must detect the subtleties unknown to most; one can sense the tire contact patches individually.
As an adolescent I was trained at a dealership to evaluate cars before and after repair. I did as many as 35 per day. Tom McCahill called it "sandpaper arse".
When we raced across Mexico in La Carrera the speed stages were flat out on (closed) public roads. Like a rally you discover and experience simultaneously. At 9 or 10 tenths I could feel the contact patches loose traction as we crossed paint lines on the pavement, sweeping road edge to road edge. The sensing technique is most beneficial when you interpret it at the onset of grip loss, before control loss. In the friction circle concept, the contact patch "static frictional coefficient" is compromised by the tread going slick and the tarmac fragmenting. The tire has to roll to stability with less induced load.
Scrub angle similarly plays into friction circle grip as experienced in understeer. Then the steering angle to travel angle exceeds 6-7 degrees the contact patches slide and greater steering angle has no effect. Getting under the 6-7 degrees gives the contact patches a chance at regaining traction. Pitching weight forward with the brakes would increase load on the contact patches, but if they are sliding recovery of frictional coefficient will be delayed and braking effect is also muted. Goodbye cones.

[CraigS]

It should be relatively easy to do. Mine take more effort than my Tacoma but not a ton more. As with other physical efforts, when you get to where you are using a high % of your maximum strength, your fine control goes to he11. If it isn't, as you can see in many threads, better pads is usually the answer. I am not real familiar w/ the 33 brakes but I am sure there are others in that sub forum who are.

[J R Jones]

I have no knowledge of 33 or Cobra brake configuration, maybe there is cause to be concerned.
On my 818 the default is the Subaru donor brakes. Option is a Wilwood kit which I have. A racer in OR has had brake issues and discovered the Wilwood upgrade has been listed incorrectly content for years. They list 1.25 thick rotors, 0.81 are supplied.
Looking at my car, the previous owner installed the 12.19 dia rotors in front (as I would) and they fit the pad radius perfectly.
The other two rotors are 12.0 diameter which fail to cover the rear pad radius by about 0.19. As I see it the larger rotors should be front and rear.
More troubling are the small pistons (1.0) in the rear and 1.62 in the front when the weight proportion favors rear. The proportioning valve is plumbed to the front(?).
Again the calipers should be closer or the same front and rear. I have lots of work fitting an alternative body and cooling system. I will get to brakes later.
jim

staggered shims.jpgstaggered shims2.jpg

[Avalanche325]

I think someone new should not be left foot braking or trail braking.

Using one foot gives that 10th of a second to let weight transfer. I talked to a national champion that never left foot brakes unless he is driving an open wheel car. Leave trail braking for long sweepers and big turnarounds.

You should concentrate on braking in a straight line, coming off brakes and then turning in. That will help you find the maximum braking and the maximum turn in. Trying to combine it will slow down your learning curve. 99.9% of the time beginners are trail braking too much and costing themselves time. I went to an SCCA Starting line school years ago. We were running laps around an oval for the very purpose of learning not to turn in until you released the brakes. The instructor would hold the wheel straight until I released the brakes. I didn't realize how much I was trail braking when I shouldn't have been. If you are pushing....trail braking is going to make it worse.

My advice from watching your video. I am not Mario Andretti, so take it for what it's worth. You are doing great by the way, so this just my idea of helping out.

Hand placement on the wheel. Your hands are constantly changing position. That doesn't allow your brain to reference steering center, where you are in the turn (wheel position-wise), or how much force is needed to turn (different leverage depending on hand position). Start at 9 and 3 and if you need to turn past 180*, do a hand cross over. Always back to 9 and 3. Never shuffle steer. Controlling a car is hugely about muscle memory. You need set reference points for that.

Look further down course. It appears to me you are sometimes running to the apex cone, then taking action. When you get to the element entrance cone, your brain should already be past the exit cone. I think that will help with a couple overshoots. I still actively work on my sight lines when I walk the course. I literally point to where I should be looking at different points on the course. Sometimes I even remember to do it when driving.

I am glad you are having fun. I just got back in a couple weeks ago after being off for a while due to isolating.

[GTBradley]

Well there is a honest difference of opinion on left foot braking. Different philosophies, I suppose. Thanks for the different take and like I said it wasn't helping or hurting my times that much, so I can go back to left foot if needed. It is quite an advanced technique. It was interesting to see that I had decent control with my left foot, but it is entirely possible that I was pressing harder on the brake than I would have with my right foot.

I was braking straight ahead before and know intuitively that you shouldn't turn while braking hard, but I was breaking loose with the front tires first and then overrunning the turn, but only on those aggressive runs. I'm suspicious that the low tire pressure and my brake bias caused part of the problem, so I'll fix that before the next event.

I was wondering about hand placement, I didn't anticipate moving my hands at all, but there were some really tight turns. I'll do the 9 and 3 position next time.

It is definitely good to be back to doing things outside and with other people. Thanks again.

[Avalanche325]

Left foot braking may work fine for you. However, for most people, it is something new that has to be learned and you are already learning a ton of new skills.

You mentioned a heel support. I read a really good article about large vs small muscles, I can't remember were it was. Basically that you should be using small muscles for car control. For instance, keeping your heel on the floor and using your smaller fine control ankle and foot muscles rather than foot in the air which uses your big sledgehammer quadriceps. Sounds like you are onto that one already.

I use the same method as CraigS for setting brake bias.

[J R Jones]

Brad, This AM I read discussion on the 33 Hot Rod thread about tire pressures. I am still skeptical about the recommendations I have read, but light street cars with fat street tires is not my expertise.
NAZ from Flagstaff is technically brilliant on many topics, and offered this video on measuring tread temperature and making data based adjustments. Well worth a look:
https://www.youtube.com/watch?v=WGm_dvrJd2E
Been there, done that.
The metrics are there for pressure, and may be relatable for camber.
jim

[Jeff Kleiner]

Measure temps if you like but after making several hundred runs I can tell you what works...Nitto NT-01 and Toyo R888R like 20-22 and Kumho XS want 18-20. Rivals are the oddball and do best at 26-30. Depending on temperature, surface and your handling preference you may end up with a 1-2 pound front/rear split.

Jeff

[GTBradley]

Thanks, Jim it’ll be interesting to see if this matches what I’m already doing.

[GTBradley]

Measure temps if you like but after making several hundred runs I can tell you what works...Nitto NT-01 and Toyo R888R like 20-22 and Kumho XS want 18-20. Rivals are the oddball and do best at 26-30. Depending on temperature, surface and your handling preference you may end up with a 1-2 pound front/rear split.

Jeff

But you guys said I can’t have those tires yet. I think I have 18 more AXs to go before I’m even worthy of sticky tires…

Seriously though, I have another reason to wait. I don’t want to throw out my 555s until I’ve gotten the wear out of them and a spare set of wheels can’t even be bought right now, or so I hear. Anyway, it’s good to have these numbers for future use.