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Thread: Autocross advice

  1. #1
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    Autocross advice

    Been a while since Iíve been posting couldnít get on my old account johno250
    I have been enjoying my roadster since 07 and itís getting and got some updates along with a much needed dynotune. Finally got the opportunity to autocross and well letís just say thereís plenty of room for improvement. It plows like a John Deere in the turns
    The engine is great 248 rwhp and a torque curve that varies by 35lbs From a tweeked SOHC with Toyota reliability.
    Hereís my question how much rubber can I get on for autocross without rubbing that I could swap for my road wheels
    In the past Iíve had 295/50/15 rear 235/60/15 front on 10Ē & 7Ē wheels but had rubbing occasionally
    But now run 275/50/15 and 225/60/15 finding good rubber in these sizes is tough so a switch to 17 at least is in order for autocross.
    I have FFR lower control arms and sn95 front spindles in the rear an 87-93 rear with northís axles brake calipers are 02 GT all around
    Iím thinking maybe 245-5 up front on 17x 9Ē and the rears Iím not sure Iíve had 295 on 10s with slight rubbing issues. I think I would have a similar problem with 315 that comes in some wheel packages
    Going to freshen the steering system with breeze offsets and a fresh rack flushing hydroboost fluid and adding an inline filter and going to DOT 3-4 back from DOT 5 in brake fluid.
    And whatís the story with anti roll bars on these. Who has them are they worth it
    Any rubber and tire recommendations appreciated

  2. #2
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    I suggest. Contacting ET Wheels and use their measurement procedure to determine the offset (front and rear) that will result in optimum clearance between chassis components and fenders. This may lead to the additional cost of custom offset wheels or confirm that an off the shelf version will work. Doing this will enable you to run the 315 rear/275 front combination provided you have reasonably firm suspension.(sometimes the use of wheel spacers will enable use of non custom wheel or just fine tune tire clearance).
    358 SBC, Winters QC, Sweet mfg, Coleman, AP Racing, ARS, TKO 600, Fuel Safe

  3. #3
    FFR Maven Logan's Avatar
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    First things first you’re going to need at least 17” or preferably 18” wheels to get great autocross tire choices and performance. Take all your measurements to figure out what the perfect offset would be for your car. Then look for off-the-shelf wheels that are close to that or could be brought close with the use of a spacer. If nothing is available, custom offset wheels are made regularly and you can have a set in a few weeks.

    You’re doing the right thing by looking at tires first. In the meantime, get as much seat time as you can autocrossing. Your driving ability will grow tremendously even though the car understeers (or so you think). As your driving improves, you will begin to realize the handling of the chassis, or perhaps learn to drive differently to make your current tires work better. This is some of the most fun you can have in a car and it’s reasonably inexpensive to participate. Notice I separated the participation in autocrossing (cheap) from the car one might build for autocrossing (expensive).
    Logan

    FFR Fanatic Since 1995
    2017 Mustang GT PP #95
    Gen3 Type 65-R: Ordered 4/32/19, delivered 6/29/19

  4. #4
    Senior Member Mike N's Avatar
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    When Ted Falk first talked me into Auto X'ing the FFR more than 15 years go I struggled a lot. The group I ran with back then had a number of nationals level drivers who were very helpful. I talked one well known driver into driving my car with me as passenger so that I could get some feedback on my car and also some driving tips. He drove the car about 100 yards from where it was parked to the start and promptly ran more than 2 seconds faster than I had run that day on his first lap with no experience at all in the car. He made 2 more runs and ended up about 3.5 seconds faster. Yes he had some recommendations for things to change on the car but quite obviously he biggest potential 'upgrade' was the driver. His two biggest recommendations may surprise you. A seat with decent lateral support and a gas pedal with better 'feel'. No mention of tires or suspension as I expected.
    Mike............

    FFR2100 - 331 with KB supercharger - T5 - 5 link rear 3.08's and T2 Torsen.

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    Agree with what has been said but one thing not to loose site of if what Class you will be or more importantly what to race in. Many times when you get into more aggressive tires it may put you into a higher more competitive class. Again, find your class and stick to the rules. Enjoy!

  6. #6
    Not a waxer Jeff Kleiner's Avatar
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    As Mike said, seat time, seat time, seat time! I have often said when instructing "don't prop yourself up with tires...learn to drive first because you'll still have the bad habits but just be doing them faster". Now, to contradict myself, just about any 15" tire you can put on these cars will perform poorly and do so by an order of magnitude if they are old and hard (harder ). BUT, you can learn on 'em. What pressures are you running? Should be no more than about 24. These cars with the factory spring setup do push and that will be exacerbated by abrupt, large steering inputs. Concentrate on turning in smoothly and gently rather than trying to "manhandle" it with fast and jerky movements.

    Being that you mention hydroboost I assume you have power steering. What are your settings? PS will allow you to go to 8 degrees positive caster which will improve camber gain when cornering. Combine this with about 1.5 degrees negative camber and it will help front bite. Going to zero toe or even 1/16" toe out will help bite at initial turn in BUT BE AWARE that it can cause the car to become darty and less stable on the highway.

    Sway bars? If you add one to the front without a corresponding change to the rear roll stiffness it will plow even worse.

    Is this a Mk3? If so you should clear 315/35-17 in the rear and 255/40-17 in front on the common 9" and 10.5" SN95 rims. At that point your tire choice will be dictated by how serious you want to get as well as what you're willing to give up to get it.

    Do you really mean this?
    Quote Originally Posted by johno250 View Post
    DOT 3-4 back from DOT 5 in brake fluid.
    DOT5 is not compatible with 3, 4 or 5.1 and if that's what is in it currently you'll need to do a lot of flushing with denatured alcohol followed by a couple quarts of glycol based fluid before refilling. And I definitely do not recommend keeping the DOT 5 in it.

    Good luck!

    Jeff

  7. #7
    Senior Member BEAR-AvHistory's Avatar
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    Quote Originally Posted by ricobrafan View Post
    Agree with what has been said but one thing not to loose site of if what Class you will be or more importantly what to race in. Many times when you get into more aggressive tires it may put you into a higher more competitive class. Again, find your class and stick to the rules. Enjoy!
    I just run occasionally with THSSC for fun no dreams of glory. That said my normal 100 treadwear tires put me in the XP class. Same car with more street oriented 200-300 treadware tires would drop it into a normal street class.
    Kevin
    MKIV #8234
    Coyote '13/TKO-600/3-Link 3:55 Rear
    Delivered 2/7/14 - Plate "COYOTE NC1965" 3/25/15

  8. #8
    FFR Maven Logan's Avatar
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    Quote Originally Posted by BEAR-AvHistory View Post
    my normal 100 treadwear tires put me in the XP class. Same car with more street oriented 200-300 treadware tires would drop it into a normal street class.
    What is the “Normal Street Class” for a FFR? From what I know currently, we have only two classes to choose from: CAM-S if using 200+ treadwear tires, and XP for <200TW tires. CAM has other rules such as minimum weight, restricted aero, interior finish, etc. In the other corner, XP is virtually unrestricted.

    Is there any other class besides CAM-S or XP that a Factory Five would be eligible for?
    Logan

    FFR Fanatic Since 1995
    2017 Mustang GT PP #95
    Gen3 Type 65-R: Ordered 4/32/19, delivered 6/29/19

  9. #9
    Not a waxer Jeff Kleiner's Avatar
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    Quote Originally Posted by Logan View Post
    What is the “Normal Street Class” for a FFR? From what I know currently, we have only two classes to choose from: CAM-S if using 200+ treadwear tires, and XP for <200TW tires. CAM has other rules such as minimum weight, restricted aero, interior finish, etc. In the other corner, XP is virtually unrestricted.

    Is there any other class besides CAM-S or XP that a Factory Five would be eligible for?
    X Prepared---any tire including full race slicks with a minimum weight without driver of 1,600# + 100#/liter + 20#/liter for >51% of vehicle weight on the rear wheels which when doing the math means that a 5.0 liter roadster must weigh greater than 2,200 pounds but in no case would be required to be over 2,300 pounds before adding the 20#/liter adjustment

    E Modified---any tire including full race slicks with a minimum weight including the driver of 1,700 pounds

    Classic American Muscle Sport (CAM-S)--->200 treadwear tires with a minimum weight without the driver of 2,500 pounds (add 150 pounds for no or lexan windshield)

    In the end we really only fit into XP. Our roadsters are seriously out gunned by the lightweights in EM and unless the car is especially heavy don't make minimum weight for CAM-S without adding approximately 250-300 pounds of ballast.

    Jeff

  10. #10
    Senior Member Avalanche325's Avatar
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    I agree with Jeff across the board.

    If you are just starting autocross, just run what you have to start. Unless you have a very specific problem, the only thing you need for the first full season is air pressure adjustments.
    If you are going to stick with it, the first purchase should be your own helmet, so you don't have to put on a loaner sweatbox.
    Tires are the single most important suspension component. And the best bang for the buck suspension improvement. You will learn faster on crappy tires though.
    I have a MKIV with a 3-link and really enjoyed the improvement and adjustability that sway bars gave me. I did not get them until I had two full seasons under my belt. They did really flatten the car out. After seeing pictures on a really tight course, I was surprised at how much body roll I had without them.

    If you are pushing in, make sure all of your braking is done in a COMPLTELY straight line. Brake, Off, turn. You could be turning in quite a bit while braking and not even know it
    If you are pushing out, make sure you are not picking up the throttle too quickly or early. Roll in smoothly. If you suddenly unload the fronts, it will wash out.

    The SCCA class for FFRs is XP (Extreme Prepared). XP is pretty much anything goes race car with slicks or any other bit of insanity that exceeds every other class. I have literally run against a NASCAR Cup car, and a couple other not street legal track weapons. The PAX is absolutely horrible. A top 10 Raw can get you 30th+ in PAX. So, if you want to get competitive, buy a Miata and run in street classes.
    What the guys around here run is CAM-S. We technically are under weight, but it's not nationals so no one cares if we don't add ballast. (I do tend to have passengers 90% of the time. People line up for a ride in a Cobra, so there is my ballast - LOL) It is only FFRs and the occasional Corvette. 200TW tires are the lowest you can do.
    In SCCA, there is no street class for FFRs. Other associations may be different, but most use SCCA classes.

    I am running the FFR 17" Halibrands. I run Nitto NT-05s. They are a good sticky tire that gives you some decent mileage on the street. I get about 10k miles out of them. Monthly autocross, occasional track day, and the rest on the street.
    If you are going to stay in XP, you could run NT-01s. They won't last long, but will grip even better.
    Last edited by Avalanche325; 09-09-2019 at 01:11 PM.

  11. #11
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    If you get sticky tires - NT05 and anything stickier - you really need a road race oil pan.

    With the wings + the diamond shaped baffle + trap doors + pickup properly positioned.

    Or you'll be replacing bearings + polishing your crank before long (at best).

  12. #12
    Senior Member rich grsc's Avatar
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    Quote Originally Posted by Jeff Kleiner View Post
    As Mike said, seat time, seat time, seat time! I have often said when instructing "don't prop yourself up with tires...learn to drive first because you'll still have the bad habits but just be doing them faster". Now, to contradict myself, just about any 15" tire you can put on these cars will perform poorly and do so by an order of magnitude if they are old and hard (harder ). BUT, you can learn on 'em. What pressures are you running? Should be no more than about 24. These cars with the factory spring setup do push and that will be exacerbated by abrupt, large steering inputs. Concentrate on turning in smoothly and gently rather than trying to "manhandle" it with fast and jerky movements.


    Good luck!

    Jeff
    Have ya tried a set of Avons? Thought my eyes where coming out of my head.

  13. #13

    Steve >> aka: GoDadGo
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    Best Advice: Don't let me drive your car because I only know how to go straight.

  14. #14
    Senior Member Avalanche325's Avatar
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    Quote Originally Posted by GoDadGo View Post
    Best Advice: Don't let me drive your car because I only know how to go straight.
    That makes for the lowest time.....until they start adding the penalties on.


    Quote Originally Posted by rich grsc View Post
    Have ya tried a set of Avons? Thought my eyes where coming out of my head.
    I would love to try a set of Hoosier A7s. I actually considered a trailer hitch and a tire trailer at one point. Of course the street tires now are as good as the track tires were 7 - 8 years ago.
    I rode in a supercharged Lotus with Hoosiers. I literally thought, "we can't make that corner" several times, but it stuck like glue.

  15. #15
    Senior Member BEAR-AvHistory's Avatar
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    Quote Originally Posted by Logan View Post
    What is the “Normal Street Class” for a FFR? From what I know currently, we have only two classes to choose from: CAM-S if using 200+ treadwear tires, and XP for <200TW tires. CAM has other rules such as minimum weight, restricted aero, interior finish, etc. In the other corner, XP is virtually unrestricted.

    Is there any other class besides CAM-S or XP that a Factory Five would be eligible for?
    Was thinking of CAM-S as a street class since its old muscle cars including Cobra replicas. Thought I would be in the same class with an "N" the first time I went but was put into NXP because of my tires never asked about the weight. Been there ever since. Dropped the N as soon as I could.



    This one is interesting, a Corvette with no body thats sort of street legal:

    Last edited by BEAR-AvHistory; 09-10-2019 at 07:54 AM.
    Kevin
    MKIV #8234
    Coyote '13/TKO-600/3-Link 3:55 Rear
    Delivered 2/7/14 - Plate "COYOTE NC1965" 3/25/15

  16. #16
    Senior Member CraigS's Avatar
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    Tell us what Mark and what front spindles you have. w/o knowing the Mark can't help on the rear tires. W/o knowing the spindles can't help w/ the front. But for many years 275x17 on these 9s
    https://www.americanmuscle.com/buwh1-9404.html
    and 315x17 on these 10.5s
    https://www.americanmuscle.com/buwh1-9404.html
    were the standard AX tire choice and these the standard wheels for those tires.
    The fronts fit on Mk 1-3.1 but can be tight in MkIV bodies. The rears fit 3.1 and MkIV and can fit the earlier Mks w/ some work. They are a much smaller outer diameter compared 295x15s so that really helps them fit. You can scroll down to the specs for the wheels to get the backspace that works to compare to other wheels. You can also look around the American Muscle website in the 'wheels 94-04 for other styles and colors. Note that many of the 18s are only 10 inches wide vs 10.5. On driving and understeer. As avalanche said, this could be driver technique. To judge that better look at turns that have a long middle so you can separate out how the car is balanced there in the middle vs entry under braking or exit acceleration. We need info on your car and where you live.
    -Go to the top right of this screen and click 'My Profile'.
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    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  17. #17
    Senior Member Mike N's Avatar
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    Here are 275 front, 315 rear on FR500 wheels, 17x9 and 17x10.5. No rub with 500 front, 350 rear springs. This is on a Mk1 with SN95 front spindles, '89 Mustang 8.8 rear.
    IMG_6828.jpg
    Mike............

    FFR2100 - 331 with KB supercharger - T5 - 5 link rear 3.08's and T2 Torsen.

  18. #18
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    Lots of talk about tires, but nobody asked about tire pressure? I would think if you are understeering that you have too much pressure in the front tires. There are a couple of practices of using chalk marks to check on the pressure. There's also a thermal test which you need the probe for. Chalk is easy to come by.

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