Sway bars vs understeer
09-06-2007, 11:53 AM
#31
I also seem to recall someone posting a thread about this with pictures, but doing a quick search turned up nothing.
Adding the KLA front sway bar support kit and delrin inner bushings, with all else remaining the same, would place even more stress on the frame rail mounting holes because there would be less absorption of energy through movement. However, it now sounds like you are considering upgrading the front springs which IMO is a good thing.
You asked about the stock front spring rate. I 'think' it's 180-something pounds, hopefully someone will chime in with the correct figure.
It sounds like you are on the right track though Norm.
09-06-2007, 03:01 PM
#32
Three Wheelin'
You are probably right that I will decide new springs are also needed. If I had added stiffer front springs and front sway bars while doing nothing to the back, I would have had lots of understeer. Buying used springs does not sound too interesting. I have used springs. If I get new springs I will know what I am getting. I would not want the stiffest springs available and stock height seems best. I have no idea what the rating of the stock springs was when they were new. Weltmeister makes 220 Lb stock height springs. How do these compare with mine when new? Is this a reasonable choice? Any suggestions?
The Weltmeister 22 mm rear sway bar will likely be able to balance out this understeer. Based on my eperience with balanced spring rates, the Welt 22 mm rear bar was too stiff even on full soft for a 30 mm 968 M030 front sway bar, let alone a stock 968 26.8 mm bar. It should have no problem balancing out your mismatched spring rates. I agree that it is a compromise that is not as good as going with balanced spring rates, but it should work. Changing out rear torsion bars to match the front spring rates would be better, but changing torsion bars is not for the faint-hearted.
09-06-2007, 09:27 PM
#33
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I am not going to risk cracked frame rails. I need new front springs. Thanks for not letting me learn this the hard (cracked) way. You have already given me some good input on what to get. Any additional input would be greatly appreciated. My parts manual says there were three different springs, up to 1988. Mine have two yellow dots, which they say means 3118-3202 N when compressed to 251 MM. Does this translate into 125 Lbs?
Thanks,
Norm
Thanks,
Norm
Last edited by Norm Swanberg; 09-07-2007 at 12:35 AM.
09-08-2007, 03:50 AM
#34
Three Wheelin'
gives the spring rate as 21.8 N/mm. 21.8 N/mm / 9.81 m/s^2 = 2.22 kg/mm x 2.212 lb/kg = 4.91 lb/mm x 25.4 mm/in = 125 lb/in.Uncompressed spring length is given by FSM as 396 mm. Compressed length = 251 mm so the spring is compressed 396 mm - 251 mm = 145 mm. Tolerance group spring force is listed as 3118 N to 3202 N for two yellow dots. 3118 N / 145 mm = 21.5 N/mm. 3202 N / 145 mm = 22.1 N/mm. Therefore the spring rate for tolerance group 2 (2 yellow dots) is approximately 21.8 N/mm +/- 0.3 N/mm = 125 lb/in +/- 4.3 lb/in = 121 lb/in to 129 lb/in.
HTH.
Don
09-08-2007, 08:39 AM
#35
Yes. The FSM gives the spring rate as 21.8 N/mm. 21.8 N/mm / 9.81 m/s^2 = 2.22 kg/mm x 2.212 lb/kg = 4.91 lb/mm x 25.4 mm/in = 125 lb/in.
Uncompressed spring length is given by FSM as 396 mm. Compressed length = 251 mm so the spring is compressed 396 mm - 251 mm = 145 mm. Tolerance group spring force is listed as 3118 N to 3202 N for two yellow dots. 3118 N / 145 mm = 21.5 N/mm. 3202 N / 145 mm = 22.1 N/mm. Therefore the spring rate for tolerance group 2 (2 yellow dots) is approximately 21.8 N/mm +/- 0.3 N/mm = 125 lb/in +/- 4.3 lb/in = 121 lb/in to 129 lb/in.
HTH. Don
gives the spring rate as 21.8 N/mm. 21.8 N/mm / 9.81 m/s^2 = 2.22 kg/mm x 2.212 lb/kg = 4.91 lb/mm x 25.4 mm/in = 125 lb/in.Uncompressed spring length is given by FSM as 396 mm. Compressed length = 251 mm so the spring is compressed 396 mm - 251 mm = 145 mm. Tolerance group spring force is listed as 3118 N to 3202 N for two yellow dots. 3118 N / 145 mm = 21.5 N/mm. 3202 N / 145 mm = 22.1 N/mm. Therefore the spring rate for tolerance group 2 (2 yellow dots) is approximately 21.8 N/mm +/- 0.3 N/mm = 125 lb/in +/- 4.3 lb/in = 121 lb/in to 129 lb/in.
HTH.
Don
You owe me two aspirin.
09-22-2007, 09:29 PM
#36
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I took it to the track yesterday. It now has the 26.8 front and Weltmeister rear sway bars and 220lb front springs. It does not rub and I was able to adjust it to neutral.
Thanks for your input.
Norm
Thanks for your input.
Norm
09-22-2007, 09:42 PM
#37
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The problem as I see it with Norm just adding a larger sway is that he is asking the sway bar to do what the spring is intended to do. Sway bars are for fine tuning, not for holding up the car. If the tires are rubbing the top of the fender liners then the springs need upgrading.
A couple problems that I could foresee are 1) balljoints binding from too much suspension travel, and 2) additional forces on the sway bar inner mounting points could cause them to crack.
If you wanna play, you gotta play. Cheaping out when tracking your car is just asking for trouble.
I came away from a track day yesterday at Watkins Glen with a real bad taste in my mouth from people doing stupid things, two incidents of which came real close to wrecking me...too damn close.
I apologize in advance if I sound harsh or patronizing, but please make sure your car is track worthy before putting yourself and others at risk. Not saying you are, but just to think long and hard about what you are doing.
A couple problems that I could foresee are 1) balljoints binding from too much suspension travel, and 2) additional forces on the sway bar inner mounting points could cause them to crack.
If you wanna play, you gotta play. Cheaping out when tracking your car is just asking for trouble.
I came away from a track day yesterday at Watkins Glen with a real bad taste in my mouth from people doing stupid things, two incidents of which came real close to wrecking me...too damn close.
I apologize in advance if I sound harsh or patronizing, but please make sure your car is track worthy before putting yourself and others at risk. Not saying you are, but just to think long and hard about what you are doing.
I have done 1 DE at the Fest last year and I totally agree with Shiners!!! That cars the fest last year were good but I REALLY got me thinking about other peoples car's out there. I know how I take care of my car and what not but I don't have personal experience with others car like suspension or BRAKES! That was one that kind of made me worry when you really think about it, you are at the end of the back straight at a high speed when "BOOM" you are spinning around and off the track because someone's brakes went out and went right into you.
09-22-2007, 10:28 PM
#38
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09-22-2007, 10:39 PM
#39
Three Wheelin'
Yes. The FSM gives the spring rate as 21.8 N/mm. 21.8 N/mm / 9.81 m/s^2 = 2.22 kg/mm x 2.212 lb/kg = 4.91 lb/mm x 25.4 mm/in = 125 lb/in.
Uncompressed spring length is given by FSM as 396 mm. Compressed length = 251 mm so the spring is compressed 396 mm - 251 mm = 145 mm. Tolerance group spring force is listed as 3118 N to 3202 N for two yellow dots. 3118 N / 145 mm = 21.5 N/mm. 3202 N / 145 mm = 22.1 N/mm. Therefore the spring rate for tolerance group 2 (2 yellow dots) is approximately 21.8 N/mm +/- 0.3 N/mm = 125 lb/in +/- 4.3 lb/in = 121 lb/in to 129 lb/in.
HTH. Don
gives the spring rate as 21.8 N/mm. 21.8 N/mm / 9.81 m/s^2 = 2.22 kg/mm x 2.212 lb/kg = 4.91 lb/mm x 25.4 mm/in = 125 lb/in.Uncompressed spring length is given by FSM as 396 mm. Compressed length = 251 mm so the spring is compressed 396 mm - 251 mm = 145 mm. Tolerance group spring force is listed as 3118 N to 3202 N for two yellow dots. 3118 N / 145 mm = 21.5 N/mm. 3202 N / 145 mm = 22.1 N/mm. Therefore the spring rate for tolerance group 2 (2 yellow dots) is approximately 21.8 N/mm +/- 0.3 N/mm = 125 lb/in +/- 4.3 lb/in = 121 lb/in to 129 lb/in.
HTH.
Don21.8 N/mm * .224809lb/N * 25.4mm/in = 125 lb/in
Better Shiners780?
09-22-2007, 11:31 PM
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Quote:
Originally Posted by Keithr726
Sorry to hijack but should my AC compressor be contacting my sway bar?
no. it shouldn't touch. One of those components is improperly installed. Check to make sure that the rear bolt is in the a/c compressor.
Back to the original topic.
Originally Posted by Keithr726
Sorry to hijack but should my AC compressor be contacting my sway bar?
no. it shouldn't touch. One of those components is improperly installed. Check to make sure that the rear bolt is in the a/c compressor.
Back to the original topic.
09-23-2007, 01:11 AM
#41
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hmmm. I only had the problem when the rear bolt was missing. Ofcourse it also could have to do with specific belt tension. As it (the belt) gets older the compressor will have to rotate farther.
09-23-2007, 09:35 PM
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In response to the comments about track safety, I think it is good to encourage others to take this seriously. I have heard many times #1 be safe, #2 have fun and #3 go faster. I think this is good advice. I have not spun in 23 track days. I feel safer on the track than I do on the highway. Combined speeds of cars going in opposite directions often exceeds track speeds. What percentage of cars on the highway have checked tire pressure or anything in the last month? I feel the drivers I have shared the track with have been sane, sober and actually paying attention to driving. This is more than you can say about alot of highway drivers. I have mostly run with Northern California Racing Club and Trackmasters. I have heard favorable comments about several other groups. I have heard some negative comments about another group. If you feel other drivers are on the wild side, perhaps another group would be better. I know nothing of groups in your area. Keep the shiny side up,
Norm
Norm
09-23-2007, 10:19 PM
#43
In response to the comments about track safety, I think it is good to encourage others to take this seriously. I have heard many times #1 be safe, #2 have fun and #3 go faster. I think this is good advice. I have not spun in 23 track days. I feel safer on the track than I do on the highway. Combined speeds of cars going in opposite directions often exceeds track speeds. What percentage of cars on the highway have checked tire pressure or anything in the last month? I feel the drivers I have shared the track with have been sane, sober and actually paying attention to driving. This is more than you can say about alot of highway drivers. I have mostly run with Northern California Racing Club and Trackmasters. I have heard favorable comments about several other groups. I have heard some negative comments about another group. If you feel other drivers are on the wild side, perhaps another group would be better. I know nothing of groups in your area. Keep the shiny side up,
Norm
Norm
Regarding choosing another group to run with...I and several others I spoke to have many track days with this group. We have never experienced this level of incompetence before. I don't know if the open track screening process needs to be tightened up or what, but we were all surprised.
Unfortunately, this was the first event I have done all season without my video camera in the car. It certainly would have made for some good commentary.
Originally Posted by kevincnc
21.8 N/mm * .224809lb/N * 25.4mm/in = 125 lb/in
Better Shiners780?
Better Shiners780?
09-24-2007, 02:26 AM
#44
Nordschleife Master
Actually the compressor is probably installed correctly. This is common on 944's. The AC compressor is not designed to fit exclusively on a 944. It is more of a universal AC compressor that can fit other cars. Because of this it has mounting tabs that are not used when mounted on a 944. The lower tab that is unused can and will rub on the 944 sway bar. This is not good, as it will rub off the paint, rust can set in and I have heard of sway bars breaking at this junction. What I do is take a sawzall and cut off the unused lower compressor bracket.
