944 S2 DE/Track suspension settings
10-18-2005, 07:28 PM
#16
Race Director
the 8v cars came with 23.5 mm units, but the S2 had bigger bar. 24 mm or 24.5 mm I think.
I did my work with a tape measure and it worked out fine. I did use like 3 floor jacks to hold the unit on the floor steady.
Here is pic
I did my work with a tape measure and it worked out fine. I did use like 3 floor jacks to hold the unit on the floor steady.
Here is pic
10-18-2005, 07:29 PM
#17
Race Car
Rob S - i don't know what your goal for the car is (racing or straight DE), but i would strongly suggest some lightweight track seats to keep you in place. i have inexpensive sparcos, and they are a definite improvement over stock seats for keeping me firmly planted. keeps your attention off the seats and on the line you're trying to achieve.
10-18-2005, 08:48 PM
#18
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No, I wasn't confused;
Most top Club Race guys are running somewhere around 600-650 all around, and it is fairly well known that if you go past 300 rear effective rate, you should have all your driving chops well learned, as the cars get more demanding. If you like that sort of setup, you are either slower than you think, or I applaud your car control skills!
Most top Club Race guys are running somewhere around 600-650 all around, and it is fairly well known that if you go past 300 rear effective rate, you should have all your driving chops well learned, as the cars get more demanding. If you like that sort of setup, you are either slower than you think, or I applaud your car control skills!
10-18-2005, 10:50 PM
#19
Pro
Thread Starter
Joseph,
I agree that some racing seats would be a good idea for this car; my goal is not true wheel-to-wheel racing, but the principles of comfort and support are the same either way. Those stock seats are pretty worthless for lateral stability on a racetrack. But it's been an evolutionary process with this car (and its owner); I've been resisting taking it away from stock configuration for reasons of legality in SCCA Solo II, which this car was originally set up for. (This car was the BS National Champ for three years in a row, 95-97, with Jeff Reitmeir driving). Despite its history, my now-waning desire to autocross at that level has been replaced by the quest for a better track performer, and I hope, a car that won't eat tires quite so fast. Hence, my Viagra job to the suspension. Racing seats are not allowed in Solo II stock classes either -- which I clung to as a reason for keeping the stock seats up until now. But now that I've disemboweled and reconfigured the suspension, it would be so distasteful to return it stock form that I have little excuse (except for the cost) to delay in getting some better seats.
John,
I'm not sure I understand the logic for optimum spring rates. If top racers are running 650 all around, then why wouldn't a 350 or so, all around (or in my case, 375 F and 330 R), be equivalent in terms of balance, but just at a lower overall stiffness level? Why would I need hundreds more pounds of stiffness up front to "balance" the 330 lb in the rear? Does it have to do with the effectiveness of torsion bars compared to coil overs?
I have another odd question. I have stock sway bar links on my new 968 adjustable rear bar. When I installed the bar with the original drop links, I tightened the bolts at each end of the drop links. What I found later was that this had the effect of "binding" the rear sway bar -- the bar effectively became much stiffer. So, I loosened each bolt just a tad so it could pivot about each point. The bolts have self locking nuts, so I figured they'd be okay. But today the shop that aligned the car tightened the bolts and told me I had left them loose. What's the best way to deal with this? Should they be absolutely tight, or slightly loose?
I agree that some racing seats would be a good idea for this car; my goal is not true wheel-to-wheel racing, but the principles of comfort and support are the same either way. Those stock seats are pretty worthless for lateral stability on a racetrack. But it's been an evolutionary process with this car (and its owner); I've been resisting taking it away from stock configuration for reasons of legality in SCCA Solo II, which this car was originally set up for. (This car was the BS National Champ for three years in a row, 95-97, with Jeff Reitmeir driving). Despite its history, my now-waning desire to autocross at that level has been replaced by the quest for a better track performer, and I hope, a car that won't eat tires quite so fast. Hence, my Viagra job to the suspension. Racing seats are not allowed in Solo II stock classes either -- which I clung to as a reason for keeping the stock seats up until now. But now that I've disemboweled and reconfigured the suspension, it would be so distasteful to return it stock form that I have little excuse (except for the cost) to delay in getting some better seats.
John,
I'm not sure I understand the logic for optimum spring rates. If top racers are running 650 all around, then why wouldn't a 350 or so, all around (or in my case, 375 F and 330 R), be equivalent in terms of balance, but just at a lower overall stiffness level? Why would I need hundreds more pounds of stiffness up front to "balance" the 330 lb in the rear? Does it have to do with the effectiveness of torsion bars compared to coil overs?
I have another odd question. I have stock sway bar links on my new 968 adjustable rear bar. When I installed the bar with the original drop links, I tightened the bolts at each end of the drop links. What I found later was that this had the effect of "binding" the rear sway bar -- the bar effectively became much stiffer. So, I loosened each bolt just a tad so it could pivot about each point. The bolts have self locking nuts, so I figured they'd be okay. But today the shop that aligned the car tightened the bolts and told me I had left them loose. What's the best way to deal with this? Should they be absolutely tight, or slightly loose?
10-18-2005, 10:56 PM
#20
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John, I think the confusion was in the usage of "Effective rate".
To get an effective rate of 300 rear would require a 525-550lb actual spring rate with a coilover or a 29mm t-bar. I think most people refer to their actual spring rate not the effective. Referring to "effective" is probably more effective.
What John is suggesting is about 600 effective front and 300 effective rear.
To get an effective rate of 300 rear would require a 525-550lb actual spring rate with a coilover or a 29mm t-bar. I think most people refer to their actual spring rate not the effective. Referring to "effective" is probably more effective.
What John is suggesting is about 600 effective front and 300 effective rear.
10-18-2005, 11:26 PM
#21
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Indeed, Max.
A t-bar is loaded at the pivot, where a coil-over spring is placed 56% of the way down the arm, and thus subject to a "leverage loss." In actuality, there is also a slight loss due to the angle of the shock and the front strut as well, but it is relatively miniscule.
In any event, a 30mm t-bar gives you about 335lbs. Using the above formula, it takes a 600lb coil to roughly equal that. That is its effective rate once losses are accounted for.
"Conventional wisdom" says that a rear effective rate of somwhere in the neighborhood of 250 is very driveable; giving good performance and reasonable control. Pushing that up 100lbs certainly does not make the car undriveable, but perhaps a bit less forgiving than the average guy wants to deal with. Many may never notice unless they push beyond their subconscious comfort zone. The faster driver (like Joe) will notice right off, but will have the skill to anticipate and control the tail, and use it to his advantage.
I'm just saying go in with you eyes open and your hands ready!
Rob, you've made an astute observation with the sway. The bushings are indeed adding to the bar rate. I doubt whether it is enough to matter, and you cannot always trust those "dome lock" nuts to stay on. Best to have them snugged down. I saw a guy fight his bushings when he tightened the pivot bolts before hooking up the ball joints!!!
A t-bar is loaded at the pivot, where a coil-over spring is placed 56% of the way down the arm, and thus subject to a "leverage loss." In actuality, there is also a slight loss due to the angle of the shock and the front strut as well, but it is relatively miniscule.
In any event, a 30mm t-bar gives you about 335lbs. Using the above formula, it takes a 600lb coil to roughly equal that. That is its effective rate once losses are accounted for.
"Conventional wisdom" says that a rear effective rate of somwhere in the neighborhood of 250 is very driveable; giving good performance and reasonable control. Pushing that up 100lbs certainly does not make the car undriveable, but perhaps a bit less forgiving than the average guy wants to deal with. Many may never notice unless they push beyond their subconscious comfort zone. The faster driver (like Joe) will notice right off, but will have the skill to anticipate and control the tail, and use it to his advantage.
I'm just saying go in with you eyes open and your hands ready!
Rob, you've made an astute observation with the sway. The bushings are indeed adding to the bar rate. I doubt whether it is enough to matter, and you cannot always trust those "dome lock" nuts to stay on. Best to have them snugged down. I saw a guy fight his bushings when he tightened the pivot bolts before hooking up the ball joints!!!
10-19-2005, 01:22 AM
#22
Race Car
i think we are all on the same page, just different sentences here.......so a 600lb rear coilover spring equals an effective rate of about 335lb in the rear - that we all understand. if you combine that with the torsion bar rate, however, you will have more like 450-475 effective rate assuming 125-150 torsion bar rate.
rob - anecdotally, i'll add that my spring rates are 350F and about 300R (126 torsion bar plus 275lb spring), and it seems fairly well balanced. it does border on oversteer, but i think that's because of the 27/19mm sway bar balance, plus the toe out i USED to have in the rear (as john has been hounding me to adjust to toe-IN, i finally did so)
rob - anecdotally, i'll add that my spring rates are 350F and about 300R (126 torsion bar plus 275lb spring), and it seems fairly well balanced. it does border on oversteer, but i think that's because of the 27/19mm sway bar balance, plus the toe out i USED to have in the rear (as john has been hounding me to adjust to toe-IN, i finally did so
)
10-19-2005, 01:30 PM
#23
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We met the last time I was at PR. You and your friend were out there with that beautiful 968. See you this Sunday, maybe at the PCA day?
Eric
10-19-2005, 06:52 PM
#24
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All,
You're right, I was confused about effective rate -- which is now clear. I had thought that the 330 lb "effective" rate of the torsion bars already had accounted for the lever arm difference from the coil spring location. Indeed, if the goal is having equal "effective" rates front and rear, I agree that I'd need heavier front springs. (But it's still not clear to me that that should necessarily be the goal!) So I'll try this setup and hope it will be okay; it sounds like others get along fine with it. It is also my goal to have a car that isn't too harsh on the street, and 650 lb/in springs in the front sounds, well, harsh. But I'll be watchful of tail-happiness on the track. If it's a problem, fortunately, changing front springs is relatively cheap and easy now, and I won't mind dialing it in. But those torsion bars are in there to stay...
John, in one of your earlier notes, when asked about optimal Toyo tire pressures, you said this:
"Toyos don't mind being 40 hot at all. Just keep your pressure increase in a comfortable range; about 8lbs."
What did you mean by keeping the "pressure increase" to about 8 lb? How can I even control that? It seems to me that if achieving a hot running pressure (of, say, 38 psi) is the overall goal, that makes the cold inflation pressure is relatively unimportant (as well as the pressure increase). How can I even control the pressure increase? It seems like that's an outcome, not something I can manipulate in any way.
You're right, I was confused about effective rate -- which is now clear. I had thought that the 330 lb "effective" rate of the torsion bars already had accounted for the lever arm difference from the coil spring location. Indeed, if the goal is having equal "effective" rates front and rear, I agree that I'd need heavier front springs. (But it's still not clear to me that that should necessarily be the goal!) So I'll try this setup and hope it will be okay; it sounds like others get along fine with it. It is also my goal to have a car that isn't too harsh on the street, and 650 lb/in springs in the front sounds, well, harsh. But I'll be watchful of tail-happiness on the track. If it's a problem, fortunately, changing front springs is relatively cheap and easy now, and I won't mind dialing it in. But those torsion bars are in there to stay...
John, in one of your earlier notes, when asked about optimal Toyo tire pressures, you said this:
"Toyos don't mind being 40 hot at all. Just keep your pressure increase in a comfortable range; about 8lbs."
What did you mean by keeping the "pressure increase" to about 8 lb? How can I even control that? It seems to me that if achieving a hot running pressure (of, say, 38 psi) is the overall goal, that makes the cold inflation pressure is relatively unimportant (as well as the pressure increase). How can I even control the pressure increase? It seems like that's an outcome, not something I can manipulate in any way.
10-20-2005, 11:32 AM
#25
Race Director
Rob,
Couple points.
Firstly I think 375F and 30 mm t-bars are good set-up. I run 350F & 30 mm t-bars on my race car.
Secondly I also run toyo's. I shoot for hot pressure fo 38 to 39 psi. In my experience on my 2600 lbs car with driver over 41 psi the tires are just off. I like them better at 38 or 39, but if see them at 40 I don't worry. At 41 psi I will lower the starting pressure.
I typically start at 32 to 33 psi. Some of that depends on track conditions.
I hope this helps.
Couple points.
Firstly I think 375F and 30 mm t-bars are good set-up. I run 350F & 30 mm t-bars on my race car.
Secondly I also run toyo's. I shoot for hot pressure fo 38 to 39 psi. In my experience on my 2600 lbs car with driver over 41 psi the tires are just off. I like them better at 38 or 39, but if see them at 40 I don't worry. At 41 psi I will lower the starting pressure.
I typically start at 32 to 33 psi. Some of that depends on track conditions.
I hope this helps.
10-20-2005, 12:09 PM
#26
Three Wheelin'
Dumb question:
How does tire stagger affect these spring rates? Does the amount of available grip at either end affect the optimum spring rate ratio front to rear?
-Jon
How does tire stagger affect these spring rates? Does the amount of available grip at either end affect the optimum spring rate ratio front to rear?
-Jon
10-20-2005, 01:01 PM
#27
Race Director
Well in my case I run 225/50's on 15x7's at all 4 corners.
Clearly narrow front vs rear tires will change the balance. Not really sure how much. I do think that unless you have Big big hp. The 944 likes the same tire front and rear.
Do note that in PCA club racing rules are such that folks tend to run narrower front vs the rears. I believe this is driven by the allowances for wheels and some what due to space in the fender wells.
Clearly narrow front vs rear tires will change the balance. Not really sure how much. I do think that unless you have Big big hp. The 944 likes the same tire front and rear.
Do note that in PCA club racing rules are such that folks tend to run narrower front vs the rears. I believe this is driven by the allowances for wheels and some what due to space in the fender wells.
10-26-2005, 10:45 PM
#28
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Just my two cents here, and I am certainly no expert. Just about everything here is a good starting point, but your driving style ultimately determines the best set up.
I spent an entire DE weekend changing my set ups from one extreme to the other, just to figure out what would happen. Along the way, I discovered that I really don't like a car that pushes. I also found out that I like my car really stiff, when it comes to shocks (maybe a hold over from karting?).
Additionally, I found out that there was another suspension variable that I wasn't adjusting, but when I did, it changed everything. So it was back to the drawing board again. I was playing tag with another club 944 club racer and asked him to drive my car and I would drive his. He was fast in his car, but I couldn't stand his set up.....he mentioned that mine seemed off as well. I got back into my car and felt completely at ease.
I have found that the most common suspension set up discussed here is usually a safe starting point, but you will need to adjust it to discover what is best for you.
I probably just repeated everything everyone else said. Excuse me......I'll take my Ritalin now
I spent an entire DE weekend changing my set ups from one extreme to the other, just to figure out what would happen. Along the way, I discovered that I really don't like a car that pushes. I also found out that I like my car really stiff, when it comes to shocks (maybe a hold over from karting?).
Additionally, I found out that there was another suspension variable that I wasn't adjusting, but when I did, it changed everything. So it was back to the drawing board again. I was playing tag with another club 944 club racer and asked him to drive my car and I would drive his. He was fast in his car, but I couldn't stand his set up.....he mentioned that mine seemed off as well. I got back into my car and felt completely at ease.
I have found that the most common suspension set up discussed here is usually a safe starting point, but you will need to adjust it to discover what is best for you.
I probably just repeated everything everyone else said. Excuse me......I'll take my Ritalin now
10-26-2005, 10:58 PM
#29
Race Car
agreed, driving style can dictate suspension setups. i'm still learning to drive, so my setup is basic and will change over time. there are so many variables.....tire pressure, tire size, alignment, spring rate, shock stiffness, roll bar size and stiffness, body height, etc. sheesshh.....i just want to learn how to make the car go fast right now.
