I think my rear springs are to big (the car was built for drifting)... what rates are you Fox chasis guys running????
Printable View
I think my rear springs are to big (the car was built for drifting)... what rates are you Fox chasis guys running????
FYI - 225lb and 275lb depending on the upcoming track event.
All depends on the other suspension parts though. One combination might not net the same or desired results as another one on a different Stang.
Spring rubbers can be the ticket also...especially during testing sessions.
you need to give some front rate info. the springs need to be matched front to rear. for example, the 4th gens like a 3:1 ratio. that means if you have a 900 front rate, the rear needs to be around one 3rd of that (300). things that will affect that ratio are things like, rear sway bar size, rod ended or poly bushing rear control arms (changes roll rate), rear downforce, and personal driving ability and driving style. tire age is also a big factor in how well the car works. old tires make the car feel as if it has too much spring rate - it feels like it has no grip.
but even if you stick w/in, for example, the 3:1 ratio a 4th gen f-body likes, too much spring rate is a bad thing. your better off w/ too soft than too stiff.
so, unless you fill us in on what front rates you have that your trying to balance the rear rates too, there is no correct answer. i know guys running 1300 lb all the way down to 600 lb fronts on a 4th gen and 325 lb to 175 lb rear rates. getting the car to balance and be nuetral is what is key here.
push = too much rear grip. drop front rates or increase rear rates
overly loose = too much front grip drop rear rates or increase front rates.
dont exclude wheel spacers when tuning your set-up. they can be added to soften a given rate, removed to stiffen a given rate.
so, what is a good ratio w/ a Fox? i do not know. i'm sure the same rules apply and there is one. what is a good rear rate for a Fox? same again, who knows w/out front rate info.
mmmmmmmkkkkaaaaayyyy? :wink:
Don't those things use a single pigtail 5.5" just like the f-cars in the rear?
Try the cheap streetstock dirt track springs from Day Motorsports online.
They come in 25# increments and are only like $45 each.
Come in 11 and 12 inch lengths.
http://www.daymotorsports.com/
jb
From the H&R website:
http://www.hrsprings.com/site/about/manufacturing.html
Another issue that adds to the debate between "Linear" and "Progressive" rate springs, is that when most spring manufacturers say that their springs are progressive they are not! Springs may be wound progressively, but that does not mean that they function progressively. Some suspension springs are wound progressively but function as a linear spring. These springs can be called "dual-stage" coils, but are generally referred to as springs with "dead" or "inactive" coils. Dead or inactive coils are coils that are in contact with adjacent coils at loaded height.
Inactive coils do nothing but give the spring enough free-length to stay tight in the spring perches at full rebound (when the tires and wheels are hanging in the air like when the car is on a lift). A spring that is wound with inactive coils and no progressive coils that are active, is actually working as a linear-rate spring. This is why when you call a spring manufacturer for spring rates for your application you must ask, "What is the actual working spring rate?" This ensures that you do not just get numbers quoted from a design sheet.
For example: A design sheet may have rates of 69lbs. per inch, to 160lbs. per inch, to 220lbs. per inch. When the actual rate is 170lbs. per inch to 220lbs. per inch. As you can see, getting the correct information is important in making a true comparison.
[EV] Read the entire article to get you going and it has a lot of information in it. A lot factors come into play when addressing the Fox body suspension. Besides springs, struts, shocks, chassis stiffness and other geometrical parts, don't forget the TIRES! They are the secondary set of springs on the car!! Set the pressue too high and you just made a nice susupension setup into garbage. Set the pressure too low and it will be more than a handful! Keep this in mind....all the time.
you shouldnt use a progressive rate spring in a racing application.
although some progressive rate springs will use up all its progressive section from just the weight of the car alone. in that case, they are o.k., but i would avoid them if at all possible.
stick to a linear spring.
2nd that one for sure.Quote:
Originally Posted by GlennCMC70
Too much rear spring in the back can be very bad. Well more correctly put an improper front to rear suspension stiffness ratio is bad. Too stiff in the rear can give the undesireable snap "oversteer" that sent me off of Hallet #1. That was with the H&R Race spring set. The rear was way too stiff. I ended up keeping the H&R Race springs in the front and use a set of Eibach street (10% stiffer than stock) in the rear as well as a stock GT front and rear sway bar setup. So many factors go into this as Glenn has stated. I think that my H&R problem was linked to the fact that the car is a stripped down race car with a lot less weight on the rear than a street car. My street/track car with full interior and spare tire in place never had any problems running a very similar suspension setup with H&R Race Springs but it still has a lot of weight on the rear. That's my theory anyway.
You're doing the right thing by asking. Keep asking and also trying different things. Just go conservative on rear rate. And remember, the Camaros don't have anywhere near the rear suspension bind that the Mustangs do. This will change the 3:1 ratio that Glenn stated. Crappy Mustang rear suspension!!!!!
Best of Luck. Call if you want to talk more - early evenings and weekends are best.
David: I am currently running linear springs at 900 lb front and 200 lb rear. Not sure if they are right or wrong but that's what it came with and now that the front end is a couple inches wider and the rear is not slapping 1" side to side, it feels pretty good. I was loose on exit @ TWS and RP suggested I remove the rear sway bar which worked well.
Hopefully this summer will lend some time to test other combinations.
Rob: I've got a rotor for you. Thanks.
Boudy
i've heard Robs means of setting up spring rates all too often. you guys are aware that jumping up and down just 25lbs in the rear rate is a considerable move, right? by limiting yourself to H&R, or Eibach, or MM springs, your moving all over the map in front or rear rates.
why do you guys not get what you need from the dirt track shops in specific rates? we sell off what we dont need at almost zero loss so there is no major risk to doing this.
just wondering.
Thanks guys!! I think the springs I have are around 400lbs which would explain the loose condition... I'll check the fronts and look at the 3:1 ratios... may not be able to correct before Hallett but all this info will help my decisions in the near future... Check out other issues on other posts... Thanks again you guys are great... you might be kicking you own butts when Jason passes you in 2008......... :twisted:
Last November I got a note in my e-mail box that pitstopusa.com was reducing their spring inventory and was selling AFCO 5.5" pigtail x 11" springs for $29 each in rates starting at 125 lbs and going to 350 lbs in 25 lb increments.
So, I bought several pairs in increasing rates
David, I have a pair of 250s and 275s I would sell you pretty cheap if you'd like them.
Some great information is to be had in this thread. One note of caution - if you work on getting rear grip and make changes to do so, the outcome with a sticky rear will be a Mustang that pushes and plows through a corner. It's a fine balance between having enough or too much rear grip when matching it up with the front. I tend to like a slightly loose condition which can be driven through during corner exit. A push will result in having to lift on exit which will slow ya down... a lot!
Don't forgot the front when changing the rear.
Testing: being consistent enough on corner entrance, apex and exit to know whether or not chang "A" made more of a difference than change "B" is paramount.
I'm always available to help test setups if the price is right. You know.. big glass of ice tea or lemonade. :D
Most definitely ... testing has to remove as many variables as possible. Be consistent on air pressure, shock settings, fuel load, etc. It all adds up.
And sometimes, you will find that a 25lb change is too much of a change and going back isn't just right either.
There are CMC legal ways to split hairs, like with bushing material or wheel spacers.
David, remember, i used the 3:1 ratio as an example for what works w/ the 4th gen f-body. due to differences in suspension design and geometry i'm sure thats not the correct ratio for a fox ford. yours could be a 2:1 or a 5:1, i just do not know.Quote:
Originally Posted by David Love AI27
Roberts cars set-up shows about a 4.25:1 ratio. he is also the only one who has posted front and rear rates.
IMHO 900lb front springs are too much. Then again, it all depends on the other 101 things involved when setting up the suspension.
700/225 seemed really close - but again, it all goes along with everything else as a whole.
Example: MSRC 700/225 the car had a huge push and nothing could be done at the time - even with tire pressure. Next MSRC event. Went with the 700/275 setup and the car was wicked loose (no changes to front suspension). With a change to the front suspension, it went from loose to slight oversteer.
Factors involved:
Tire pressure(s)
Front/rear swaybar and bushings
Strut/shock rebound rate
Weight distribution
Chassis flex
Big factor - driver's ability to hit all marks consistently
.02
Just my .02
I would never make changes to the wrong end of the car.
If the front is doing something undesirable, make changes at the front.
Don't take away grip you have at one end just because the other end has less.
jb
Harmony is that elusive pot-o-gold.
that is true for a car that is almost balanced or is balanced. but if you are just way way off (soft) on rear rates and the front is spot on, the car will still push. softening the front will make the push go way, but the car should be faster if you were to stiffen the rear. overall, you have to work the problem. sounds to me like David has way to stiff of a spring on the rear and no idea whats on the front. but guessing from the rears, i would think 900-1000 is what he will find.Quote:
Originally Posted by jeffburch
Davids best bet for now is the copy another drivers set-up and then work it from there.
Ah but which driver to copy? :lol:
It seems to be common perception that some guys are fast thanks to their cars..but my experience is that its just as likely to be that some guys are fast in spite of their cars. Some guys just aint fast. 8)
My point is, Glenn is right, find some basline from which to start and then experiment from there. There is no "right" answer, and what is fast for you might not be fast for someone else. I've driven some cars that I thought were awful but their owner liked it, knew it, and ran fast with it. I've also driven a few that I thought were fabulous who'se owners thought were completely off the mark.
The driver "MUST" know what is going on in order to have any idea of what to change or adjust. Thinking that the car is pushing due to an incorrect suspension setup when actually they are driving into a corner waaay too fast leads to nowhere.
A car + 2 seats = priceless
you have to be confident in the car before you are willing to drive it fast.
Instructed many green students? hehe :DQuote:
Originally Posted by GlennCMC70
seafoam green to be exact.
My car just received a second seat for that very reason. :wink:Quote:
Originally Posted by SmackDaddy
Boudy
Me too.
<licks chops>
jb
Guys,
Remember when people start talking about front/rear ratios, the actual wheel rate of the setup may be vastly different.
Since the Mustang front spring is set so far inboard from the wheel and strut, it takes a huge front spring to act the same as what would be on a 4th gen Camaro or AI Mustang which has coilovers.
The same holds true in the rear. The closer to the axle (or behind) you get the spring, the less lb-in rate you will need to get the same effective wheel rate.
Mustang Front Motion Ratio
Conventional = .25
Coil-over = .9
Mustang Rear Motion Ratio
Conventional = .49
Coil-over = 1.1
CMC Mustang with H&R “Race (Red)” springs
Front: 750 lb-in (at spring) = 188 lb-in (wheel rate)
Rear: 260 lb-in (at spring) = 132 lb-in (wheel rate)
= 1.42/1 Front/Rear split
AI Mustang with coilovers and T/A
Front: 450 lb-in (at spring) = 405 lb-in (wheel rate)
Rear: 350 lb-in (at spring) = 385 lb-in (wheel rate)
= 1.05/1 Front/Rear split
As shown above, if you are running a T/A car (AI or Cambird) your front/rear split will be much less than a CMC Mustang which has a bunch of "built in" bind with the 4-link design. The T/A cars need less split (more rear spring rate) due to less rear bind (geometrical and bushings) which will now need to be accounted for by a higher spring rate.
Good info, Marshall.
You are correct in your thoughts about "effective" rate which is dependent upon a lot of differing factors, like wheel offset, bushing material and even air pressure in the tires, which changes dramatically during a 20 minute race.
Factor in lessening fuel load, head wind down force.
However, the suspension pick up points on ANY CMC platform is fixed and a known. So once one figures out where the "balance" is, chassis design plays a lesser role.
I don't know if David's head is spinning, but mine is.
To answer Glenn's question about why I mix n matched spring manufacturers. I knew I had too much rear spring, I had a set of Eibachs laying around, I called Eibach to get an idea about what rate they were, they were much softer than the H&R rears, so I tried them. Pretty scientific - huh? That got me into the gross ballpark (luckily) and now I can tune it in with adjustable shocks, tire pressure, steering strategy, throttle strategy, downshift - upshift strategy, rev limiter strategy, front sway bar end link tension, water leaking from my cool shirt cooler, overaggressive driving, etc., etc., etc.
Get someone else to ride and drive the car at a more relaxed event like TWS Motorsports Club. There is a lot of talent and experience here to help you along. My advice is to set the car up with a bit of a push and work toward the loose condition slowly.
Quote:
Originally Posted by SmackDaddy
I'M SCREWED!!! :( WHERE ARE THESE MARKS YOU SPEAK OF?!?! :shock: ONLY MARK I AM FAMILIAR WITH IS THE BIG YELLOW SQUARE BETWEEN 1 & 2 AT TWS.....
tried to hit that square going CW... didn't work too well :wink:
I kid... I understand what you are saying...
[quote="GlennCMC70Davids best bet for now is the copy another drivers set-up and then work it from there.[/quote]
Honestly... this is what I was looking for..
you all have to remember that I purchased the car from a guy who knew NOTHING about car setup... he tried to setup for drifting but didn't even know that it had a 2.73 gear, I have a 3.27 in it know and can kick the ass end around pretty good imagine what it will do with my 3.55 or a 3.75...
Guess what I'm learing about suspensions is... everyone likes something different and there are MANY ways to adjust...
Thanks again
installed 2nd seat for just that reasonQuote:
Originally Posted by SmackDaddy
Wait till you try and understand roll center .... :shock:Quote:
Originally Posted by David Love AI27
Well, I know turn 6 at TWS going CW has marks at turn in, and the apex. Both are on the left side of the track though, so even those are confusing since you "hit" one but not the other. :lol: :lol:Quote:
I'M SCREWED!!! WHERE ARE THESE MARKS YOU SPEAK OF?!?!
He needs to understand roll center if he wants to make his CMC Mustang handle!Quote:
Originally Posted by mitchntx
PM sent David - I don't want to share my secrets with all these GM guys :wink:
I'll share secrets.
10+ years ago many of the CMC folk were wrestling with this very question.
Global West was a primary sponsor for CMC at the time.
They worked closely with many of the drivers...who went the full range of linear rate springs. (Most of us were too low and too stiff, a common misconception....Suspension travel is your friend.)
The Global West "Blaine Butler Setup" was winning races at the current GM frequency in a notchback Fox. We all copied, used that baseline...and all got faster. (Much like all of our guys are now, here in Texas.)
900 front/ 200 rear (personally, I'm at 190 rear)
Koni adjustables all around and a day of testing to play with shock valving.
...and driver preference/comfort level will vary, as mentioned.
-=- Todd
PS- Where is Micah? We need some expertise on Roll Center???
Heeyyyyyyy...there was a bright yellow Mustang and a black Mustang with a white hood right in the spot where I needed to be when I got there... at the apex. Kinda had to go around! :twisted:Quote:
Originally Posted by Al Fernandez
Please explain the term "apex" as it applies to the attached photo?Quote:
Originally Posted by Todd Covini
Oh, Mitch... Stop splitting hairs. We all know that Todd uses a dynamic apex. You know, the one that shifts to fit the story being told. :lol:
Boudy
He is in management, afterall.Quote:
Originally Posted by Boudy