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Re: Circle Track suspension and steering advice
[Re: MadMez]
#1285793
08/19/12 11:32 AM
08/19/12 11:32 AM
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Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
TC@HP2
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master
Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
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Okay, found one of my set up sheets from my GM days on a high banked oval.
I found the following set up
rf lf
850 1100
lr rr
250 200
Front sway bars sizes varied between 1, 1.125, and 1.25 That we used to tune depending on track conditions. Shocks were the big variable that I never really got dialed in. Initial class rules prohibited racing shocks. The last year I ran this class they allowed fixed valving racing units. Because I spent so much on tires, I wasn't able to spend as much on shocks as I wanted and never really got it right. I did make steady improvements and managed to win a bunch of heat races and was leading a main before being crashed out and destroying the car. Therein lies a problem with car set ups, when they are fast, you are on a thin line of balance and a slight nudge can upset that balance.
Why didn't I run a mopar? Budgets were always a concern and by the early 90s when I ran the GM, mopar parts were hard to find and easily 3x as much in cost. I did run a mopar 10 years earlier on a 3/8 flatter banked oval. I was not as dialed in on suspensions back then and never really was much of a contendor and didn't attend races regularly. It was more of a fun effort. See the sticky at the top of the forum for pics of my oval track mopars. I've thought about running one since, but again, cost is always an issue and these days, time and effort are also factors for me. Oval track cars get torn up, regularly. I just don't want to rebuild one weekly anymore so I've been turning more towards autox and open track days.
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Re: Circle Track suspension and steering advice
[Re: TC@HP2]
#1285794
08/19/12 03:55 PM
08/19/12 03:55 PM
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Joined: Jan 2003
Posts: 27,480
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,480
So Cal
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Quote:
Okay, found one of my set up sheets from my GM days on a high banked oval.
I found the following set up
rf lf
850 1100
lr rr
250 200
Front sway bars sizes varied between 1, 1.125, and 1.25 That we used to tune depending on track conditions. Shocks were the big variable that I never really got dialed in. Initial class rules prohibited racing shocks. The last year I ran this class they allowed fixed valving racing units. Because I spent so much on tires, I wasn't able to spend as much on shocks as I wanted and never really got it right. I did make steady improvements and managed to win a bunch of heat races and was leading a main before being crashed out and destroying the car. Therein lies a problem with car set ups, when they are fast, you are on a thin line of balance and a slight nudge can upset that balance.
Why didn't I run a mopar? Budgets were always a concern and by the early 90s when I ran the GM, mopar parts were hard to find and easily 3x as much in cost. I did run a mopar 10 years earlier on a 3/8 flatter banked oval. I was not as dialed in on suspensions back then and never really was much of a contendor and didn't attend races regularly. It was more of a fun effort. See the sticky at the top of the forum for pics of my oval track mopars. I've thought about running one since, but again, cost is always an issue and these days, time and effort are also factors for me. Oval track cars get torn up, regularly. I just don't want to rebuild one weekly anymore so I've been turning more towards autox and open track days.
Was that a 1/4 mile extremely banked oval?
We run a 1/2 mile high banked oval. We run way less than HALF those spring rates with a modern type big swaybar, big shock setup. Bumpstops (shock bumpers) were made illegal in our class. We did run them sucessfully, but track thought they were increasing the cost of the class.
Now we went to Stockton 1/4 mile last week and had to run the front springs of to about 400 lbs. Probably need more. They redid the track since the last time we ran a year ago. We ran stock caliper (vs alum) and giving up 40-50 HP per our home tracks rules. Still came in second.
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Re: Circle Track suspension and steering advice
[Re: TC@HP2]
#1285796
08/20/12 12:17 AM
08/20/12 12:17 AM
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Joined: Jan 2003
Posts: 27,480
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,480
So Cal
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Quote:
Well, banking on I25 Speedway is 33*, so I'd say it was pretty steep. This is the same banking that exists on Slinger Speedway.
This also was in the 1992 season, long before the advent of the big bar/soft spring set ups that are so popular now. Does such a set up lends its self to high banking? I suppose since they run them at Daytona and Talledega. However, those also are much, much longer tracks and I have been out of the scene for some time, so I can't say what exactly is the hottest set up for a short track these days.
Madmez has found out that cars in his class are running 7500-1000# springs, so I'd say high rate springs are still some what popular for that level of banking and those classes.
Yes, that's a TON of banking on a 1/4 mi. Sort of a unique track.
That 1/4 mi Stockton99 track is only 17 and 14 degrees banking.
And we are running a full tube chassis glass bodied car. Not like a stock based Street Stock type car the O.P. is working with.
If you have nothing to go off of, you sort of gotta start with what the competitors seem to be telling you. That will get you started.
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Re: Circle Track suspension and steering advice
[Re: TC@HP2]
#1285797
08/20/12 12:18 AM
08/20/12 12:18 AM
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Joined: Mar 2012
Posts: 168
Washington State, USA
Winchester 73
member
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member
Joined: Mar 2012
Posts: 168
Washington State, USA
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Quote:
I'd have to go back and try to find my notes on my set ups, but I seem to recall that the GM arms I used were either just shy or just over a 50% motion ratio for the springs. I'd imagine metric chassis are similar, but may not be exactly the same as the earlier F and X body stuff I was using. 50% is a close enough ball park to say a 800# GM spring is a 400# wheel rate.
I know a 1.22 41" B body bar is 400#. Not sure what a 1.22 37" A body bar would be, but it would be higher. Of course, with a 3200# minimum weight requirement, this would give the nod to an A body potentially being more competitive than a B body.
When you say coil over, I assume you are talking about a clamp on coil overload assist and not an actual coil over racing shock/spring combo. The former is a band aid for loads, the latter a component specifically outlawed by the rules requiring stock, make to make suspensions utilizing OEM pick up points. Yes, you could clamp one of those overload units in place, however, the shock tower is not designed for that amount of loading so eventually you will bend something. I also assume they do not provide rates on any of those so it is a swag on what amount it will help. There is a motion ratio involved with the shock mounting locations, so if they claim a 500# load capacity per inch, it may only provide an effective rate increase of 50# at the tire contact patch. Will that be enough to help, maybe. However, you still have tech inspection and rules compatibility to deal with and if the overload spring is the crutch that makes you competitive, I'll put money on it being made illegal after your first main event win.
Turning a sway bar into a torsion bar is an interesting trick that could be effective. The mounting would present certain challenges since you cannot clamp a round bar tight enough to provide a consistent spring action. The hex ends on FJM cars was huge to absorb the leverage produced. I suppose a hex mount inside the K frame to match the t-bars hex would work, but then you would need to bend the opposing end to simulate a sway bar and mount in a manner that won't deflect. That might work for a while. I'm also not sure how that would impact roll couple percentages since you could then radically alter it from side to side. Eventually, someone will figure it out and again, likely outlaw it.
also remember you would get a HECK a lot more spring rate for the same amount of metal becose the mountong poit isnt on the fulcrum like a torsion bar.thaqts the whole achilies heal of a torsion bar-coil springs that are nowere near as fat as our tbars push down harder becose they are pushing out clost to the wheel.and for that matter volare bars look so much like t bars i bet u could use those bars and mounts tucked into the k frame and no body would notice.
have we come to a point where we are comfortable as mopar peaple to admit how much t bars blow? 
i always get this wierd feeling when i hear guys talking about thier new rist thichness t bars that at some point they are using thier lower control arms as springs  anyone have a calculator to figure the spring rate of a lower control arm?
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Re: Circle Track suspension and steering advice
[Re: Winchester 73]
#1285798
08/20/12 01:46 PM
08/20/12 01:46 PM
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Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
TC@HP2
master
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master
Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
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Actually the torsion bar is better in that regard because the motion ratio of the stock mopar set up is 1:1. This is because the t-bar is mounted at the pivot point. There is no wasted spring rate because of leverage as there is with a coil set up. By comparison, the chevy coil spring ratio is 1:.52, so they have to add 48% more spring rate to achieve the same wheel rate, compared to the mopar design. Do lower control arms deflect, sure, to some degree. However, it is minor enough that for this level of effort, it can be construed to be zero. On top of that, you will have sidewall compliance that is a bigger facter than arm deflection. Overall weight of the GM coil spring set up is slightly higher, IIRC. I'd have to do some more digging to see if I have all the sprung/unsprung calcs still sitting around. Again, the mopar design does put that similar weight factor a bit lower since the t-bar sits in plane with the lower control arm as compared to a large spring that sits on top of the control arm. Additionally, the t-bar weight, and big t-bars are heavy, also sits closer to the center of the car compared to the coil sitting up in line with the front spark plug of the engine. Torsion bars aren't that bad. A number of sprint and midget classes use them as well as several Porsches and any number of light trucks. It is just in a classic mopar configuration, the selection of rates and the cost of those bars sucks compared to coils. A good set of T-bars will run $365. By contrast, a pair of coils is $150, maybe less at a swap meet. Quote:
Yes, that's a TON of banking on a 1/4 mi. Sort of a unique track.
Yup. That's even more than Daytona. Sure makes for some uber fast lap times. Our record is a hair over 10 flat, set in '92 and I think it stood as world's fastest until the early '00s when Anderson Speedway took the title around 9.95. Now Slinger Speedway has the title at 9.90. So its taking about ten years for these records to fall and they are only improving by a few hundreths. That's a small margin that's taking a long time to overcome.
One thing I did learn about that steep banking...after a short rain shower, you have a 3-5 race window when you can make a three wide pass on the outside and make it stick. Once you get some marbles and dust up there, you're back down to two lanes. Since we tend to get regualr thundershows between 3pm to 7pm, I'd occasionally get the luck of running on a perfectly clean track with no groove. Nothing freaks people out more than to pass em three wide in the turn...
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Re: Circle Track suspension and steering advice
[Re: MadMez]
#1285801
08/22/12 11:34 PM
08/22/12 11:34 PM
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Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
TC@HP2
master
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master
Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
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Quote:
I seem to have opened a bigger can of worms than I anticipated. After spend quite a bit of time reading about roll centers, spring, wheel and sway bar rates, the theoretical handling line, roll couple distribution, etc., etc., I realized I know way less than I thought I did. I searched previous posts and am going to pick up some of the reading material suggested and see what more I can learn.
Thanks for all the replies guys!
No doubt there is a lot going on under a car in a corner and I would never discourage you from learning more. However, I didn't know all that much when I bolted in my first cage and hit the corners. It was certainly trial by fire and the school of hard knocks. While I asked around, I often found errouneous and conflicting information. Perhaps the providers didn't know any better themselves, perhaps they were dileberatly trying to mislead me.
In any case, if you really want to run, don't spend too many seasons trying to understand it all before you jump in. Oval track racing is LOADS of fun, even if it is frustratng on occasian and sometimes tiring. I LOVE driving a car, but spending 14 hours in 100* heat, racing cars that get beat to a pulp, only to get home at 3 am, can wear you out.
You could always offer to help out a team that seems a bit understaffed to help you learn some of the intricies of your particular track. Pick a class above or below yours so you don't appear to be stealing someone's secrets. Since you are picking an entry level class, you will find manipulation of those factors you listed above to be more difficult than more purpose built cars, which is, after all, the point of entry level racing.
This is, unfortuantly, also how it becomes easy to start driving chevys. You can buy a built car for a quarter of the cost of buildng your own and immediatly be out racing and picking up tricks. The drawback is once you spend $$ on a bow tie, its more expensive to swap brands over later and give up all the parts you aquire.
In any case, post up, ask away, and yes, start reading. I'd suggest for a starting point the Steve Smith book "Building the Pro Stock Late Model Sportsman". While chevy based, it is also very good at explaning the interrelationships of all those thing relative to an oval track car.
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