Page 2 of 2 FirstFirst 12
Results 26 to 36 of 36

Thread: Autocross Setup - using math to get me in the right neighborhood

  1. #26
    Join Date
    Feb 2005
    Location
    Bloomington, Illinois
    Posts
    6,184
    My Cars
    2011 E92 M3, 2007 335i
    Quote Originally Posted by JoshS View Post
    I'll just say -- have fun with this.

    I've been "racing" (autocross, road racing, hill climbs) cars since the '80s. Being a techie myself, I started this way, studying the math.

    Here's what the math leaves out of the equation -- "easy to drive fast." You can make a car that's theoretically, as in, by the book faster, but it's only faster if the driver is capable of driving it at the limit, consistently.

    Softer cars are easier to drive fast. They might not be as 100% capable as a stiffer, by-the-book car, but 99.99% of the time, they will get a faster lap time because the driver is more confident.

    Throw out the book. Do what the fast people do. It's better.
    Don't know why I checked in today for the first time in a long time but this thread really brings back some memories. I tried every rate combo from 400# Front all the way to #750 rear with AST DA shocks that could handle it. By the end of my time in the Z, I was sitting on #550F with H&R sway on soft/#700 rear using stock RSB. The rear of the car really was better when the spring/shock/RSB tuning de-emphasized the rear trailing arm tendencies to dislike fast transitions.
    Now in E92 M3 ZCP -- Absolute beast

  2. #27
    Join Date
    Aug 2013
    Location
    Chicago, IL
    Posts
    198
    My Cars
    2001 M Coupe
    I called up TC a few weeks ago and ordered the 300F/700R combo, and will be installing this weekend. TC gave me a hard time about ordering such a large disparity in spring rates, but had no comment on the motion ratios, wheel rates, or ride frequencies. I know the guy has been around a lot, but not sure if he was on the same page here. I did get a few interesting things out of him though:

    - he told me that back in the day they ran 400F on Hoosiers, finding that to be the fastest setup. Yeah, RE71R's are the cheater tire, but they're no Hoosiers. So if I can't generate the same grip levels, why would I need that much spring? One more data point to confirm my 300F choice.
    - he told me stock springs were something like 160F/350R. Double each of those numbers and what do you get? About 300F/700R, preserving the stock wheel rate split front/rear. Then square up the tires and remove the rear bar, and you dial out the stock understeer without taking away grip from either end. At least that's my hypothesis.

    I'll be spending the coming weekend in the garage. Here's my current plan:

    Rear suspension
    - Poly bushings
    - 700#
    - Remove bar

    Front suspension
    - Condor UHMW FCABs
    - 300#
    - Stock bar
    - Adjustable end links

    Rake
    - 0.5 inches

    Alignment
    - camber: ~-2* rear, ~-3* front
    - toe: in a little rear, out a little front
    - caster: ~stock

    Also picked up a set of scales for a corner balance.

    Hoping to have time to do a valve adjustment and fix my leaking CPV valve too.

  3. #28
    Join Date
    Aug 2013
    Location
    Chicago, IL
    Posts
    198
    My Cars
    2001 M Coupe
    Quote Originally Posted by z3papa View Post
    Don't know why I checked in today for the first time in a long time but this thread really brings back some memories. I tried every rate combo from 400# Front all the way to #750 rear with AST DA shocks that could handle it. By the end of my time in the Z, I was sitting on #550F with H&R sway on soft/#700 rear using stock RSB. The rear of the car really was better when the spring/shock/RSB tuning de-emphasized the rear trailing arm tendencies to dislike fast transitions.
    Good to hear from you Clark. I'll be at the CCSCC Test and Tune on the 8th to start sorting this all out. Where do people hang out these days now that CICEnet is dead?

    I know you thought that these cars had a lot of potential in STR back in the day, and if I'm not mistaken that was before the S54 cars were part of the class. It's still going to take me a while to get to full prep, but I see the potential here too. The biggest hurdle for the S54 is headers since the cats need to stay within 6". But if that can be figured out...fully prepped with headers-back exhaust, CSL airbox (can't believe that that's class legal!), tune, 25lb. seats, battery...all of a sudden we're talking -250lb. and +50hp.

  4. #29
    Join Date
    Feb 2005
    Location
    Bloomington, Illinois
    Posts
    6,184
    My Cars
    2011 E92 M3, 2007 335i
    I won't be at the CCSCC event as I just had knee surgery today. The advanced TNT is a great event for dialing in your car. You've have plenty of time to pull the car and make adjustments. There has been no replacement for CICENET as far as I know. I honestly think Robin has a good shot if he ever went to an event to trophy in STR but it will be really tough, especially now that the ND has been developed but it's a sharp knife in a gun fight. I would not waste the time on modifying the header to move the CAT as power in the S54 won't be its achilles heal. The Bimmerworld 3.5" single exhaust would be a consideration back from the CAT. The airbox is legal and supposedly really produces results. Weight reduction is key as tire to weight ratio is what dictates more than hp. The seats are a huge reduction but there is a proposal to change that which just came out increasing it to 35 lbs a side. Battery saves a ton.
    Now in E92 M3 ZCP -- Absolute beast

  5. #30
    Join Date
    Dec 2014
    Location
    San Francisco, CA
    Posts
    841
    My Cars
    2001 Z3 3.0 Coupe
    Quote Originally Posted by Fumanchu282 View Post
    I called up TC a few weeks ago and ordered the 300F/700R combo, and will be installing this weekend. TC gave me a hard time about ordering such a large disparity in spring rates, but had no comment on the motion ratios, wheel rates, or ride frequencies. I know the guy has been around a lot, but not sure if he was on the same page here. I did get a few interesting things out of him though:

    - he told me that back in the day they ran 400F on Hoosiers, finding that to be the fastest setup. Yeah, RE71R's are the cheater tire, but they're no Hoosiers. So if I can't generate the same grip levels, why would I need that much spring? One more data point to confirm my 300F choice.
    - he told me stock springs were something like 160F/350R. Double each of those numbers and what do you get? About 300F/700R, preserving the stock wheel rate split front/rear. Then square up the tires and remove the rear bar, and you dial out the stock understeer without taking away grip from either end. At least that's my hypothesis.

    I'll be spending the coming weekend in the garage. Here's my current plan:

    Rear suspension
    - Poly bushings
    - 700#
    - Remove bar

    Front suspension
    - Condor UHMW FCABs
    - 300#
    - Stock bar
    - Adjustable end links

    Rake
    - 0.5 inches

    Alignment
    - camber: ~-2* rear, ~-3* front
    - toe: in a little rear, out a little front
    - caster: ~stock

    Also picked up a set of scales for a corner balance.

    Hoping to have time to do a valve adjustment and fix my leaking CPV valve too.
    Do please report back on your experience. I'll probably wait until this summer, but I do think I'm going to go to the same spring setup on my car. I'm currently at 400F/700R. If they had an 800R spring, I would go for that instead.....but they don't.
    2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT

  6. #31
    Join Date
    Aug 2013
    Location
    Chicago, IL
    Posts
    198
    My Cars
    2001 M Coupe
    Fasteners needed more heat and PB Blaster than I had anticipated, and the shock bodies were so bad that I had to cut the old lock rings and lower spring seats off, but I got most of this completed this weekend. Haven't aligned or corner balanced yet, but took it around the block to settle the springs into place. Tough to report anything yet because it was 35 degrees on tires that still had mold release...but initial results are promising.
    IMG_1996.jpgIMG_2007.jpgIMG_2016.jpgIMG_2019.jpg

  7. #32
    Join Date
    Dec 2007
    Location
    Great Dismal Swamp
    Posts
    14,417
    My Cars
    E36/7 E36/8x2 E39/2 E46
    The only thing better than greasy summer tires and cold pavement is greasy summer tires, cold pavement, and supercharger.

  8. #33
    Join Date
    Aug 2013
    Location
    Chicago, IL
    Posts
    198
    My Cars
    2001 M Coupe
    Corner balanced this weekend. Here's the results with 5/8 tank gas, 170 lb. driver, floor mats and tools removed:
    IMG_2023.jpg

  9. #34
    Join Date
    Dec 2006
    Location
    Batavia, IL
    Posts
    4,385
    My Cars
    00 M Coupe, 08 335xi
    So Matt did not have the best conditions to start for his first SCCA event o the new setup. We will see how his setup works on a better day. Maybe he will let me take a run or two. Either way, high 30's and wet was not the day for RE-71's. I was 2.5s faster then the best RE-71 shod s2000 and even 1s ahead on the 2nd place on what I would have expected was the preferred Continental "rain tire". The Bridgestone S-04's were working well for me and resulted a good result overall as well.

    My best run was 2nd fastest RAW time for the event (69 cars were brave or stupid enough to come out).

    Last edited by SunzOut; 04-18-2018 at 10:02 PM.

  10. #35
    Join Date
    Oct 2017
    Location
    Los Angeles
    Posts
    77
    My Cars
    99' ///Mcoupe
    Sweeeet!!! Love the enthusiasm!

    Good stuff man!
    Garage
    2017 F80 M3 - Silverstone ( hers )
    99' Mcoupe - Boston Green (mine )
    2017 Toyota Mirai
    15' Yamaha R6


  11. #36
    Join Date
    Dec 2006
    Location
    Batavia, IL
    Posts
    4,385
    My Cars
    00 M Coupe, 08 335xi
    Quote Originally Posted by z3m.casey View Post
    Sweeeet!!! Love the enthusiasm!

    Good stuff man!
    Of course at that point I did think I had fastest Raw time! Dam Evo in STU dropped 1.5 seconds on his last run to take it away.

Page 2 of 2 FirstFirst 12

Similar Threads

  1. Replies: 15
    Last Post: 12-11-2013, 02:47 AM
  2. Replies: 15
    Last Post: 05-06-2012, 04:01 PM
  3. About to get own3d in the mouth- any advice????
    By 99bmw740il in forum Off-Topic
    Replies: 35
    Last Post: 09-11-2003, 09:24 AM
  4. Replies: 9
    Last Post: 04-21-2003, 02:25 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •