Backdrafts are good cars! My Backdraft autocross buddy and I have swapped cars at events and have come to the same conclusion; his car with a Coyote has more power than my mildly built 325-350ish HP EFI 5.0 Windsor but mine has more grip. When we compete against each other it's a darn near even back and forth; sometimes he's faster and some times I am. Different ways of getting to the same end
Jeff
Jeff,
Do you know what rear gears your Coyote buddy is running?
20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.
Seriously guys, you know how valuable this information is to people looking to do autocross? I’m just trying to stay out of the way so the information can by laid down for posterity.
JR, I’ll be hanging on to this information for when I get my own alignment tools - next up will be a four post lift. Thanks too for relating the real-world experience and stories, they are valuable for context and entertaining.
Jeff, yes thats Exactly why I elected to install PS. I had ASBs on my order with FFR but swapped it at the last minute for the power steering rack after a conversation with Paul (EdwardB) about steering geometry.
I did count my steps on the slaloms and they were equally spaced, this time. However, while working the course the guys next to me, resetting the slalom cones put them back on some X’d out chalk boxes. That made for some confused and frustrated drivers for a little bit.
CraigS, thanks for any help you can offer on alignment equipment setup. I took my roadster to a speed shop this last time and they tried to hit me with $240 for an alignment, but came down to $180 after my jaw hit the floor. Definitely worth the investment in equipment and knowledge if I want to go back and fourth from street to track alignment settings.
Last edited by GTBradley; 05-01-2021 at 04:22 PM.
Bradley
Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.
The distance between "finished" and finished is literally infinite.
Alignment tools;
Caster/camber; for a long long time I just had one. Last year I bought a second one so things can move a little more quickly. https://www.longacreracing.com/produ...y---NO-ADAPTER
It has a 1/4 or 5/16 threaded hole in the end so this is my adapter made from a piece of shelving from HD. I got a piece of threaded rod, locktited it into the gauge, and use a couple of hard plastic washers and a Nylock. You need to be able to twist the gauge on the stud to level it at each 20 deg turn so the plastic washers allow it to be tight to the board but still rotate. Align tool by craig stuard, on Flickr
When doing caster you need to turn the wheels 15 or 20 degrees, set the bubble and turn them the same angle to the other side. The outer ends of the gauge are machined to this angle. To make it easier to see when you have the turn correct I velcro these to the gauge and eyeball so they are parallel to the side pipes. 20180606_134740 by craig stuard, on Flickr
Toein; I have for years been using a self welded up version of this. https://www.longacreracing.com/produ...etitle=Toe-Bar
but a couple months ago I got these. https://www.longacreracing.com/produ...Magnets-(pair)
They both give the same result but the plates are a lot less$. With IRS you need to get the toe correct but also need it centered on the car. IE you could have the toe correct but both wheels are pointed off to one side. I use a laser and a self made scale for this. This I lay down, slide under the car just behind the front wheel, stand it up and pull til the pvc hits the inside of the main 4 inch frame tube. IMG_20170419_160800746 by craig stuard, on Flickr IMG_20170419_160647869 by craig stuard, on Flickr
For many years I had just one caster/camber gauge, one laser, one scale. Last winter I decided to upgrade some so I bought another gauge and laser, and built another scale. This is the current setup. 20210501_093241 by craig stuard, on Flickr
The laser has a magnet in it so I got a small piece of steel sheet and screwed it to the board. It is a very nice piece from HD but it's $60. Harbor Freight has one for $25. For anyone reading through this understand that doing alignments is not that difficult. But it does take time. Starting from scratch on a newly assembled FFR you can easily spend 4-6 hours. So the key is make the time work into your life and it can be very rewarding. But what happens w/ most of the specs is you have the reading, jack up the car, make an adjustment a guessed amount, drop the car, roll it and bounce it, and take a new reading. Hopefully each time you get closer to the desired spec but I manage to turn something the wrong way at least once every alignment. When you have spent an hour adjusting caster and camber and are still a 1/4 to 1/2 deg off side to side, if you are worrying about time that 1/4 deg difference may look to be good enough. If it's caster, it probably is good enough. If it's camber, it is not.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
Craig, This pangs of scientific! Kudos.
I have built resto-rod chassis from scratch and from wrecks. I adopted lasers and digital angle gages to get dimensions correct and chassis square. By default I started with what I had on hand, and a gun sight laser still is valuable, I find the dot resolution is finer than construction lasers. OTOH the construction laser can provide a reference plane under the chassis. If I align one end suspension mounts to the laser plane, I can measure for twist on the other end suspension mounts. I was surprised to find error in a professionally straightened chassis. This lead to my measuring alignment, but I accept that my alignment is "ball park" and defer to professional machines.
BTW my measuring "kit" also includes four plumb bobs. Gravity is my friend.
When we raced the EVO we did measure and adjust at the track, including weight distribution at all four corners.
We used a stack of floor tiles to level the car at static ride height. The tiles were stacked under each tire and leveled by spirit or digital laser. The tiles had some lubricity to allow steering and the tires to displace laterally as the suspension settled. We also used a string alignment system which was fore and aft frames attached to the car, extending to the side at a level with the wheel centers. A string wrapped around the car on the frames and provided a reference to set toe, front and rear. Of course the vehicle centerline had to be identified.
I like the string on dedicated frames technique. I have seen a couple that used electrical conduit attached to the quickjacks. Strings attached to jack stands suck.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
My method for measuring caster is using a digital level between the upper and lower ball. I have a price of metal machined to fit between the ball joint studs and the level fits on the flat edge. Always within a tenth of a degree from what a hunter alignment machine reads. Easy and works.
My method for measuring caster is using a digital level between the upper and lower ball. I have a price of metal machined to fit between the ball joint studs and the level fits on the flat edge. Always within a tenth of a degree from what a hunter alignment machine reads. Easy and works.
Jim1855, As you can see in this thread, there are differences and in the case of AX there is a possibility of compromise for street performance.
There is also the influence of vehicle type and driver preference.
As sagely stated "The successful racing car is the best combination of compromises".
The stakes for track racing justify tuning at a higher level. For instance a road course within an oval like Daytona will demand weight jacking for the high bank.
LaCarrera Pan America will justify more robust parts, increased static height and lighter operating loads.
In either case the car can be tuned for maximum speed on the straight, but a second gear course is quite different from 165 to 185MPH. If nothing else the aerodynamic downforce and stability will influence set-up.
jim
Racing a Shelby GT350 and Boss 302 in SCCA we had four differentials set-up for top speed at 7000RPM. The extremes were Blackhawk Farms, 4.56 and 110MPH to Brainerd or Elkhart 3.89 and 145MPH or 3.50 and 164MPH (289 vs 351)
The unlimited Studebaker 1953 Lowey coupes ran 185MPH across the LCPA Mexico desert.
I have seen Forum videos of 818Rs at VIR running the 2 minute challenge at what looked like 160MPH. https://thefactoryfiveforum.com/cont...Two-Under-2-00!
jim
I have run 4 seasons of SCCA regionals but it was a long time ago and in way different cars so my thoughts are definitely not definitive. I 'think' the main difference between AX and road course settings might be toe in or out. Sometimes for AX, people run zero or slight toe out in the front for quicker response at corner turn in. They may also run closer to zero in the rear. There is only so much trouble one can get into at 60mph in a parking lot, so going toward instability to get quicker response is not very dangerous. There might be some difference in shock and/or spring rates and their effect on acceleration squat. 3000rpm in 2nd (AX) gives harder accel than 3000rpm in 3rd and higher gears(road course). So an AX setup might have a bit more rear spring or shock rate which would also move the overall balance toward oversteer which is generally good for AX.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
I tried that a long time ago and couldn't make it work repeatably. My problem was that I couldn't figure a way to hold my little jig in line w/ the car if looking at it from the top. With both caster and SAI angles working at it, the slightest jig rotation changed the reading a bunch. BTW there is a formula where you turn the wheel 15-20 deg and measure camber. Then turn it 15-20 deg the other way and measure camber again. Plug in the two #s and out comes caster. Found it.
This equation allows you to use any angle so if you can't turn 20 degrees each way because the bar hits something, you can use 15 degrees or other.
Jim1855, There are differences beyond alignment as you would expect, and they used to be fewer and simpler. Think power.
In the sixties/seventies the Pro cars (Formula and Sport Racer) were sophisticated and driving required exceptional skill. The drivers like Jones, Revson, Donohue, Posey, Savage were enlisted to pilot pony cars in Trans Am. The elite drivers called them "taxis" but they loved them. The cars were comparatively crude production-based and driven with what looked like abandon. It was brakes, power and guts. In a steel cage there was a faux perception of invulnerability. The SCCA club classes were similarly specified. The downside was fragility. The racing loads fatigued and yielded parts and challenged fasteners. Managing deterioration was routine. Real race cars were task-designed, more durable and more sophisticated.
Real race car parts and designs have trickled down into production based cars resulting in complex adjustments and fine settings.
I seperated from the USAF with a 1966 Shelby GT350. Surveying the WI autocross scene I found the Tri-State organization and the AMX team was very competitive. I joined to find FTD was usually the AMX team and specifically Chauncie Martin in his 289 powered Austin Healey 3000. After a year I sold my Shelby and bought an SCCA prepared GT350 to go Club racing. After my first (fall) driver's school I rebuilt the car and was late for my second school in the spring. I ran the more amature MidWest Council races through the summer. Chauncie was paying attention and prepped the Healey for racing. His first event was Blackhawk Farms, 1.9 miles, flat and ~110MPH straight. A good production car lap was 1:15. Chauncie qualified mid-pack but he disappeared when the green flag dropped. Post race he told me "I never thought I would not have enough power". I never saw him at the track again.
I find that era cars are more numerous at the vintage race events than they were back in the day. Not only is my race Shelby still out there, my street car is now a vintage racer. The displacement and power now is 20% to 30% more than I raced, but the lap times are similar or greater. The difference is it is a power event, passing on the straights, but not contesting corners. A great time is had by all.
Kit cars are something else. They too have "trickle-down" engineering and parts, making sophisticated chassis tuning possible for AX and/or track events. That 818/VIR video looked more stable than my Shelby was. Not a "taxi". jim
It's threads like this that encourage me to get my build completed. I've been lagging for too long, just didn't care. But now I really want to get moving and will.
For GT Bradley, there was an earlier comment about getting out of first gear, a wise recommendation. I run road tracks in 3rd & 4th, plenty of power, still a need to be mindful of power delivery but nothing like the lower gears. First gear is for leaving stop lights and lighting up the tires.
I wish more people ran some form of track events, it's the only way to find out just what the car will do. Can't get close to it on the street, at least not w/o threat of arrest. I did my first track event at Gingerman in 2004 just 6 weeks after putting my first Superformance on the road. It was "eye opening" to find out just how fast it was and how fast I could get into serious trouble. BTW, I've never been on a road track that I haven't fallen off of. There's just something special about agricultural excursions beyond how dirty a car can get.
Thanks Jim and yeah doing it in 2nd is going to change things big time, but I gotta say, with a Coyote, that RPM range between 4000 and 6000 is ultra-fun. It maybe better left for drifting? Anyway, I totally agree, the track is the way to enjoy the car to it’s fullest. I had no idea what I was missing until now. It helps too that autocross doesn’t generally risk damaging the car either.
Bradley
Bradley
Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.
The distance between "finished" and finished is literally infinite.
Bradley,
I too am just getting started with the auto cross thing and have really enjoyed the discussions on the thread. I’ve posted a link here http://thscc.com/track-program/nonht...%20Driving.pdf that I have also found to be very informative. While the article is focused on HPDE and closed course oriented I think a lot of the concepts would transfer to AX. IE: keeping your head outside of the car, smooth inputs, and situational awareness.
BTW, like you I also picked up the heel stop kit from Breeze and hope to get it installed this week. I also found some knurled bar stock for the clutch side but need to find a band saw to split it prior to bolting it into the floor. I’ll let you know how it goes once I get it them into the car.
Cheers,
Jeff
When I took my GT350 to the auto-x I tried it in first gear. With an 8,250 redline, I figured let's give it a shot. Well, as mentioned above, the drifting was fun but the times were no better, maybe even worse.
My Cobra's 347 has so much torque and it starts basically just off idle that I get it right into 2nd when I went. In fact, watch this video of that day. It was a nice day for Nov in NY, but it was Nov in NY so the tires never got really warmed up. It may sound like I'm riding the clutch and playing as I leave, but really that's tire spin. The clutch was engaged fully immediately.
As I said before, I love exploring the limits of the Cobra safely at the auto-x, but it stinks to be there all day for 10 minutes of driving.
.
Adam
____________________
I finally caught a snake!
MKIV, 347, T5, 3.55. `93 Cobra R brakes, heated seats, PS and lots of custom touches.
For track setup it really depends on how serious you want to be. Autocross too for that matter. Some guys come in on a trailer, keep log books, take temperatures, spray down the tires with ice water between runs, etc. Real deal racecars will even run different settings on each side of the car to fit the particular track. They also change shocks, springs and rear end gears for each track. If I were getting that serious, I would be getting a car with a full cage.
For HPDE track days, I leave it the same as my autocross / street setup. I am running 1/8" toe in. -2.5* camber, and -7* caster. I have a solid rear. One thing is that I do not run any rake. I pulled that 1/4" extra height out of the rear for more grip. I run 200TW tires which are a good do it all range and you can squeak 9-10k miles with an autocross a month and a couple track days a year. By the time I get some inside wear the tires are pretty much used up grip-wise anyway.
Bradley,
I too am just getting started with the auto cross thing and have really enjoyed the discussions on the thread. I’ve posted a link here http://thscc.com/track-program/nonht...%20Driving.pdf that I have also found to be very informative. While the article is focused on HPDE and closed course oriented I think a lot of the concepts would transfer to AX. IE: keeping your head outside of the car, smooth inputs, and situational awareness.
BTW, like you I also picked up the heel stop kit from Breeze and hope to get it installed this week. I also found some knurled bar stock for the clutch side but need to find a band saw to split it prior to bolting it into the floor. I’ll let you know how it goes once I get it them into the car.
Cheers,
Jeff
I got that heel stop installed, actually re-installed as the angle was wrong the first time. I love the position reference it provides already. My foot was moving around so much that on bumps it would cause a little surge on the gas. Thanks for the reading material.
Bradley
Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.
The distance between "finished" and finished is literally infinite.
When I took my GT350 to the auto-x I tried it in first gear. With an 8,250 redline, I figured let's give it a shot. Well, as mentioned above, the drifting was fun but the times were no better, maybe even worse.
My Cobra's 347 has so much torque and it starts basically just off idle that I get it right into 2nd when I went. In fact, watch this video of that day. It was a nice day for Nov in NY, but it was Nov in NY so the tires never got really warmed up. It may sound like I'm riding the clutch and playing as I leave, but really that's tire spin. The clutch was engaged fully immediately.
As I said before, I love exploring the limits of the Cobra safely at the auto-x, but it stinks to be there all day for 10 minutes of driving.
Yeah, I figure if the Miatas don't need a lot of power to get good times I certainly don't need to be running at max HP/TQ. Nice video! I remember seeing this back when you originally posted it and it helped motivate me to the course. That fast run did look the smoothest and the car looks very flat in the turns, I'm guessing you have at least the front anti-sway bar?
Last edited by GTBradley; 05-03-2021 at 09:00 PM.
Bradley
Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.
The distance between "finished" and finished is literally infinite.
For track setup it really depends on how serious you want to be. Autocross too for that matter. Some guys come in on a trailer, keep log books, take temperatures, spray down the tires with ice water between runs, etc. Real deal racecars will even run different settings on each side of the car to fit the particular track. They also change shocks, springs and rear end gears for each track. If I were getting that serious, I would be getting a car with a full cage.
For HPDE track days, I leave it the same as my autocross / street setup. I am running 1/8" toe in. -2.5* camber, and -7* caster. I have a solid rear. One thing is that I do not run any rake. I pulled that 1/4" extra height out of the rear for more grip. I run 200TW tires which are a good do it all range and you can squeak 9-10k miles with an autocross a month and a couple track days a year. By the time I get some inside wear the tires are pretty much used up grip-wise anyway.
I saw some of that crazy stuff going on with some of the guys driving really high performance cars, I didn't know what they were doing, but it made me realize I'm not going to go that far. I'm just going to see how quick I can get with technique and with what equipment I have and eventually with better tires, alignment changes and possibly an anti-sway bar.
Just guessing here, but you mean 7˚ caster not -7˚, yes?
Bradley
Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.
The distance between "finished" and finished is literally infinite.
As a fellow newbie to the motorsport arena one thing I did find (I too was looking for more track time per day than autox was providing) is HPDE or open track days. They provide a much larger amount of time on track (think 6 20-minute periods instead of a few 1-minute runs). You lose the competitive component/timing which stinks (unless you go time trials which is currently out of my league) but there is a bit more flow to the day overall as you repeatedly see the same corners over and over during a session and can adjust accordingly to learn how the car behaves. Downsides are increased costs, increased speeds, and increased wear and tear on the car.
Just a thought - I still attend and enjoy both styles.
Yeah, I figure if the Miatas don't need a lot of power to get good times I certainly don't need to be running at max HP/TQ. Nice video! I remember seeing this back when you originally posted it and it helped motivate me to the course. That fast run did look the smoothest and the car looks very flat in the turns, I'm guessing you have at least the front anti-sway bar?
No sway bars. Very stiff springs which I actually changed for softer ones this winter because of our crappy NY roads. I can't wait to see how that changes the handling on the course.
Originally Posted by BrewCityCobra
As a fellow newbie to the motorsport arena one thing I did find (I too was looking for more track time per day than autox was providing) is HPDE or open track days. They provide a much larger amount of time on track (think 6 20-minute periods instead of a few 1-minute runs). You lose the competitive component/timing which stinks (unless you go time trials which is currently out of my league) but there is a bit more flow to the day overall as you repeatedly see the same corners over and over during a session and can adjust accordingly to learn how the car behaves. Downsides are increased costs, increased speeds, and increased wear and tear on the car.
Just a thought - I still attend and enjoy both styles.
I've done HPDE in many cars but won't do it in my cobra. A little too dangerous for me and also too far to travel without a tow vehicle and trailer. But you're right, SO much track time, it's great!
In addition to being significantly more dangerous, 20 min on a road course is a whole other world for your car as far as oil and water and brake cooling.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
In addition to being significantly more dangerous, 20 min on a road course is a whole other world for your car as far as oil and water and brake cooling.
Not to mention the wear & tear on you. 20 minute sessions of driving takes a toll. This isn't intended to diminish the bodily stress of the instantaneous changes in autoX.
On the street it's water temps in slow traffic. On a road track it's oil pressure and oil temps, you'll figure out quickly why coolers are necessary. And brakes - cherry red is pretty.
While I'm not an autocrosser, I'd guess that water and oil temps barely get to the normal range. Oil pressures may vary depending on time in a corner and pushing the oil to the ends of the pan. At 1G of cornering, which is fairly easy to do, the oil won't care if it's in the pan or valve cover.
It's all great fun, dangerous perhaps, but then so's sex, doesn't mean people are going to stop doing it. Whatever you choose you'll quickly figure out why the cars are so cool.
As a fellow newbie to the motorsport arena one thing I did find (I too was looking for more track time per day than autox was providing) is HPDE or open track days. They provide a much larger amount of time on track (think 6 20-minute periods instead of a few 1-minute runs). You lose the competitive component/timing which stinks (unless you go time trials which is currently out of my league) but there is a bit more flow to the day overall as you repeatedly see the same corners over and over during a session and can adjust accordingly to learn how the car behaves. Downsides are increased costs, increased speeds, and increased wear and tear on the car.
Just a thought - I still attend and enjoy both styles.
YES! I did the Charlotte SCCA Track night at CMS, highly recommend. The car performed amazingly, except for FF brakes. Wilwoods on the way and have another track night scheduled for June 5. As you said, not competitive but allows you to open it up to see what the car can actually do. I'll probably try Auto-x but I really don't get too excited about it, that may change one I try?
On a road track it's oil pressure and oil temps, you'll figure out quickly why coolers are necessary. And brakes - cherry red is pretty.
While I'm not an autocrosser, I'd guess that water and oil temps barely get to the normal range. Oil pressures may vary depending on time in a corner and pushing the oil to the ends of the pan. At 1G of cornering, which is fairly easy to do, the oil won't care if it's in the pan or valve cover.
Regarding the track, I recall reading somewhere that Shelby American's policy for differential oil coolers was any race over two hours - I can't imagine a transmission oil cooler would be very different.
Autocross is the only place I've gotten my oil temp all the way past water temp - met a guy a couple years ago (in another FFR roadster) who was using a carpet drying fan between runs to cool his oil pan.
Seemed to be working pretty well, but mine was only approaching the point where I would consider dragging all that around.
By the end of the second autocross run my oil temp will be well beyond water temp - I manually run the electric radiator fan on for 30-90 seconds after shutdown and preceding startup to keep it under control - but heat is definitely an issue in autocross.
And agreed - you need a good road race oil pan - because that quickly becomes a factor too - I had to polish the crank + replace all the bearings after the first season (high G oil pressure loss / no baffles in oil pan / etc).
Here's one I forgot to ask about and Jeff K just reminded me of on another thread: what about front tire size? I'm using a 255/40 but I've seen up to 275 used up front. Would wider be better?
Last edited by GTBradley; 05-05-2021 at 10:46 AM.
Bradley
Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.
The distance between "finished" and finished is literally infinite.
Good question. Here are my thoughts on that topic. It depends on the tire and your car. Some cars may have clearance issues if they go too wide. Some tires have a different diameter with different widths also. A wider tire will be harder to turn if you have manual steering, so you will feel the difference after a long day at the track. It also takes a little longer to heat up a wider tire if you're doing autocross. So there can be tradeoffs to be made when considering which width to run.
MkII: 408 Dart block dry sump, 750cfm carb, G-Force T-5, 8.8 rear with 3.55 gears, 3-link, Kirkey seats, black ceramic coated twister mufflers with shields and adjustable turn down tips, passenger roll bar, front and rear roll bars. 2020 GT500 Magnetic metallic, with white and lime green stripes.
275/315 has been the standard setup for a long time. When FFR re-did the body for the MkIVs they made the front fender flares slightly smaller and added that 1/2 inch wide lip that extends toward the center of the car. This is when the 245s and 255s became more popular. Trimming that lip to zero helps a lot. Also the most common point of tire fender contact is at the front of the tire rather than at the top as one might expect. So just a little extra removed from the front of the flare fixes the problem. You can see how close the tire gets by turning the steering while sitting in the garage. On the left front tire look at about 9 to 10 oclock.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
If the car tends to oversteer, and if steering responsiveness is very good, is there a need to go to a wider front tire? I have 245's and the steering is so quick I would assume going to 275 would only make that worse. (rears are 315's). 17".
(I used the word "assume" on purpose since I'm just speculating, so, ya know. lol)
.
Adam
____________________
I finally caught a snake!
MKIV, 347, T5, 3.55. `93 Cobra R brakes, heated seats, PS and lots of custom touches.
If the car tends to oversteer, and if steering responsiveness is very good, is there a need to go to a wider front tire? I have 245's and the steering is so quick I would assume going to 275 would only make that worse. (rears are 315's). 17".
(I used the word "assume" on purpose since I'm just speculating, so, ya know. lol)
Is the car easily balanced with throttle position in a steady state corner?
Where you can get in the corner, straighten the front wheels, and essentially guide yourself through the remaining turn with throttle position?
Not a power slide - tire slip angles.
This is the balance I am looking for first in one of these cars on the autocross course.
You should be able to get there on 315x245 or 315x275, but it may require different settings - starting with tire pressure.
You should also be able to get there with 315x315, but that's almost certain to require a change in spring rates (softer back or harder front / probably rearrange all the way around).
Is the car easily balanced with throttle position in a steady state corner?
Where you can get in the corner, straighten the front wheels, and essentially guide yourself through the remaining turn with throttle position?
Not a power slide - tire slip angles.
This is the balance I am looking for first in one of these cars on the autocross course.
You should be able to get there on 315x245 or 315x275, but it may require different settings - starting with tire pressure.
You should also be able to get there with 315x315, but that's almost certain to require a change in spring rates (softer back or harder front / probably rearrange all the way around).
I dunno yet. I only auto-x'd the car once and it wasn't really warm enough to get the tires fully heated up. All I can say is every time I got on the gas the back tires spun pretty easily. The video I posted above doesn't really show just how loose the rear felt to me (except when I spun out ). And when I spun out that was a fantastic lesson for me as I get to know this car. I went into a decreasing radius turn too fast, lifted, and was instantly facing the wrong way! Wahoo! And THAT'S why I went there, to learn stuff like that. I had no idea that the Cobra handles like an old 911.
Funny thing is: last week I was on some local main roads taking an exit ramp. It's wide and I typically take it pretty fast even though it's also decreasing radius. Well, as I entered the turn and was about the lift off the gas, my brain said "Hey, dummy, don't just lift while turning, remember what happened last time!" Since I didn't want to try and guide myself through it with throttle position as you said, instead I had the room to straighten the wheel and brake a bit, then get back into it and finish my turn. Much safer that way on the street. And I was very glad for the auto-X spinout! I can't wait to get back to the course as the weather gets warmer and learn some more, safely.
.
Adam
____________________
I finally caught a snake!
MKIV, 347, T5, 3.55. `93 Cobra R brakes, heated seats, PS and lots of custom touches.
Since I didn't want to try and guide myself through it with throttle position as you said, instead I had the room to straighten the wheel and brake a bit, then get back into it and finish my turn. Much safer that way on the street. And I was very glad for the auto-X spinout!
Sounds like your approach is excellent.
I think it's important to get know how these cars feel when they're approaching the ragged edge - because the nature of the (super) car makes it surprisingly easy to get there by accident (they make things happen quick).
Autocross is absolutely the safest place to learn + polish those (perishable) skills.
I ended up running 315 front and 335 rear and the car was always too loose. 800 front springs, a 1 inch Forte front bar, the front DA shocks adjusted really hard allowed me to get away w/ it for 2 seasons but my plan was to go back to a 295 fronts. I decided that the 40mm difference front to rear (275-315) had always worked and the 20mm difference (315-335) was not enough. But we moved and now autocrosses are all 2 hour drives each way so I am in a different car now. My gut is that 255 would be a little less capable but not terrible. If I had 255s and found I was too tight, I'd just crank in more front negative camber. Which reminds me, once the 315-335 was found to be too loose, I went from -3.25 (I had been running that for a long time) to -2.75.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
Mike and Adam, I could not agree more. Using an FFR to it's fullest performance can't be done anywhere but AX or track. Heck, even a Corolla driven at it's limit is way too fast for the street. Back around 2007 we were on the interstate in my wife's 2005 Accord. Came over a rise in left lane at 75 and everyone in front was nearly stopped. I hit the brakes, was looking at the mirror as well as in front, and saw the guy behind me gaining on me. So I go to the grass median to go around the guy in front of me and away from the guy behind. The guy in front had already tapped the guy in front of him and one of their plastic bumper covers was half way onto 'my' grass. So we pass 4 cars in the grass and my wife says aren't you going to stop. Heck no, this grass feels soft to me so we need momentum to keep from getting stuck. We finally ease back to the pavement, it's all behind us and fortunately it was all fender benders and no seriously shortened cars. It was all over in 30 seconds. So I pick the pace back up to normal. 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. Besides they are so much fun. I am 72 and still at it. Next one is in 9 days at an airport where I have never run. Can't wait.
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
Here's one I forgot to ask about and Jeff K just reminded me of on another thread: what about front tire size? I'm using a 255/40 but I've seen up to 275 used up front. Would wider be better?
Sorry, been away from the forum for a few days. I ran 255s for years (my original crappy Sumitomos and 2 sets each of Kumho XS and Nitto NT-01) then went to the 275 when I changed to Toyo R888R 2 years ago. I HATE a car that pushes and could could cross over from push to neutral to loose with a 2 psi front/rear split with the 255s. The 275s up front allow me to keep it a little loose (just how I like it) with even pressures f/r. Not entirely scientific since I changed to a different tire at the same tame as I upsized but it’s probably pretty safe to say that although the change isn’t dramatic there is more front grip. Same end result, just a different way of getting there.
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Originally Posted by Jeff Kleiner
Backdrafts are good cars! My Backdraft autocross buddy and I have swapped cars at events and have come to the same conclusion; his car with a Coyote has more power than my mildly built 325-350ish HP EFI 5.0 Windsor but mine has more grip. When we compete against each other it's a darn near even back and forth; sometimes he's faster and some times I am. Different ways of getting to the same end
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). And when I spun out that was a fantastic lesson for me as I get to know this car. I went into a decreasing radius turn too fast, lifted, and was instantly facing the wrong way! Wahoo! And THAT'S why I went there, to learn stuff like that. I had no idea that the Cobra handles like an old 911. 
