944 Race Alignment for Daytona - Need Help
03-22-2005, 04:21 PM
#17
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Jim et al,
I've experienced exactly the same problem. Reason: too much ride height and too much spring in the rear. I agree with most of the comments above, and would make a few adjustments:
Rear toe - limit the toe-in to about 1/16". Reason? When you use power (down the straight), it increases toe in. The rear wheels, under power, toe in naturally. This increases drag and tire wear. Aluminum bushings minimize this effect. I experimented with 0 toe in the rear and it sucked, the car was not fun to drive. 1/16" seems about right. Toe out is a nightmare from what I hear.
Rear sway bar - get an adjustable.
Ride height: Yes, lower height = better handling, but more important is the angle of the front a-arms. When I set my car up, I use three criteria (in order):
1. front a-arms horizontal to the ground
2. ride height at rear 1/8"-1/4" lower than the front (measured at the seam in the kick plate)
3. 5" ride height (for SCCA)
Then corner balancre. The car rode like a dream. The logic for these:
1. This makes sure that you get the desired camber change on the inside tire under cornering (i.e. goes more positive). Likewise, if the car is too hight, the outside tire will go posotive before going more negtaive under cornering.
2. More weight in back = better rotation. I have really weak (28mm) rear t-bars so this is especially important (Vaughan - 32mm on the way!!!).
3. needs no explanation.
You shoudl not need to re-valve the rear brakes. I had no more problems once I took out the rear helper springs in my car (which subsequently lowered it).
I run Hoosiers, so I don't know about camber. However I think your caster is way too high. Factory setting is 2.0 for the 944. More caster changes the camber under cornering and again accelereates wear and increases drag.
A lot of this info i learned from Appalachian tire and Joe Cogbill.
I hope to go to Daytona - look for ITS #17, dark blue.
Timo
I've experienced exactly the same problem. Reason: too much ride height and too much spring in the rear. I agree with most of the comments above, and would make a few adjustments:
Rear toe - limit the toe-in to about 1/16". Reason? When you use power (down the straight), it increases toe in. The rear wheels, under power, toe in naturally. This increases drag and tire wear. Aluminum bushings minimize this effect. I experimented with 0 toe in the rear and it sucked, the car was not fun to drive. 1/16" seems about right. Toe out is a nightmare from what I hear.
Rear sway bar - get an adjustable.
Ride height: Yes, lower height = better handling, but more important is the angle of the front a-arms. When I set my car up, I use three criteria (in order):
1. front a-arms horizontal to the ground
2. ride height at rear 1/8"-1/4" lower than the front (measured at the seam in the kick plate)
3. 5" ride height (for SCCA)
Then corner balancre. The car rode like a dream. The logic for these:
1. This makes sure that you get the desired camber change on the inside tire under cornering (i.e. goes more positive). Likewise, if the car is too hight, the outside tire will go posotive before going more negtaive under cornering.
2. More weight in back = better rotation. I have really weak (28mm) rear t-bars so this is especially important (Vaughan - 32mm on the way!!!).
3. needs no explanation.
You shoudl not need to re-valve the rear brakes. I had no more problems once I took out the rear helper springs in my car (which subsequently lowered it).
I run Hoosiers, so I don't know about camber. However I think your caster is way too high. Factory setting is 2.0 for the 944. More caster changes the camber under cornering and again accelereates wear and increases drag.
A lot of this info i learned from Appalachian tire and Joe Cogbill.
I hope to go to Daytona - look for ITS #17, dark blue.
Timo
03-22-2005, 04:34 PM
#18
Addict
Rennlist Member
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I agree 100% with the comments on the brakes - I run KFP's from Paragon all the way round, and LOVE them. Never had any brake issues, kinda disgusting. 
Yes, I've got a stinky lot of caster... was advised to get as much as I could swing by a former occasional crewmember who spent some time as a race engineer with Arrows in F1 once upon a time... best described as free camber in the corners only. So 4-4.5 was as much as I could dial in evenly - kinda like cheating, leaning the tires into the corner. As I said, it's worked great for me.
FWIW, my car usually weighs in about 2% tail-heavy. Drive it like a rear-driver!
I like playing with the suspension much more than the engine, even if it can be so much more of a PITA. At least when you screw it up, you don't experience that sickening feeling in the pit of your wallet when you let the smoke out of a fresh engine...
Yes, I've got a stinky lot of caster... was advised to get as much as I could swing by a former occasional crewmember who spent some time as a race engineer with Arrows in F1 once upon a time... best described as free camber in the corners only. So 4-4.5 was as much as I could dial in evenly - kinda like cheating, leaning the tires into the corner. As I said, it's worked great for me.
FWIW, my car usually weighs in about 2% tail-heavy. Drive it like a rear-driver!
I like playing with the suspension much more than the engine, even if it can be so much more of a PITA. At least when you screw it up, you don't experience that sickening feeling in the pit of your wallet when you let the smoke out of a fresh engine...
03-22-2005, 09:27 PM
#19
Three Wheelin'
Jim
On my early 944, I have 450 lb front springs and Koni Yellows, 30 mm rear Torsion bars with Koni Yellows there too. 2.5 degrees camber all round, stock caster, no toe on rear, and 1/16 toe out on front. All that ain't no big deal at Daytona. The thing that will help you the most is having a .83 fifth gear, instead of the 87's .73 gear. Of course 10.2 Compression ratio, instead of the 9.6 would help too. Daytone is a top speed track.
I picked up 6 seconds on the gear ratio change alone. Yes, you read that right, 6 seconds. With the .73 gear, my car pooped out at about 124 mph on the banking. When I changed to the .83 gear (I put in a 1987 924S trans in.) the top speed on the banking went up to 144 mph. There is a lot of top speed running at Daytone, and changing the gearing, or adding more hp will do you the most good.
944 Transmissions from 1983 through 1987 have a .73 fifth gear ratio , the 1988-89 944's have the .83 gear. Both the 1987 and 88 924S have the .83
What happens is that with the .73, the 944 engine can't push the car through the air, and achieve much more than 4700 rpm. But eith the lower geared .83 fifth, the car will go right to red line, which on my speedo is about 144 mph. Though, speedos on different cars do differ.
Anyway, I have the timing sheets on the two times I was there, and was 6 full seconds faster with the .83 gear, and that was the only change. Though, obviously, I was a few more laps experienced, but I doubt that made much difference.
Bill Seifert
1987 944S Race Car
I still have the old car too.
On my early 944, I have 450 lb front springs and Koni Yellows, 30 mm rear Torsion bars with Koni Yellows there too. 2.5 degrees camber all round, stock caster, no toe on rear, and 1/16 toe out on front. All that ain't no big deal at Daytona. The thing that will help you the most is having a .83 fifth gear, instead of the 87's .73 gear. Of course 10.2 Compression ratio, instead of the 9.6 would help too. Daytone is a top speed track.
I picked up 6 seconds on the gear ratio change alone. Yes, you read that right, 6 seconds. With the .73 gear, my car pooped out at about 124 mph on the banking. When I changed to the .83 gear (I put in a 1987 924S trans in.) the top speed on the banking went up to 144 mph. There is a lot of top speed running at Daytone, and changing the gearing, or adding more hp will do you the most good.
944 Transmissions from 1983 through 1987 have a .73 fifth gear ratio , the 1988-89 944's have the .83 gear. Both the 1987 and 88 924S have the .83
What happens is that with the .73, the 944 engine can't push the car through the air, and achieve much more than 4700 rpm. But eith the lower geared .83 fifth, the car will go right to red line, which on my speedo is about 144 mph. Though, speedos on different cars do differ.
Anyway, I have the timing sheets on the two times I was there, and was 6 full seconds faster with the .83 gear, and that was the only change. Though, obviously, I was a few more laps experienced, but I doubt that made much difference.
Bill Seifert
1987 944S Race Car
I still have the old car too.
03-23-2005, 07:20 PM
#20
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Bill - what wheel/tire combo are you using? I run an 88 transmission and last year was only able to get abotu 140mph on the odometer. I am using 225/45/15. Was wondering if taller wheel/tires make all that much difference?
Timo
Timo
03-24-2005, 01:00 PM
#21
Three Wheelin'
Timo
I was using Hoosier 225-45-15 also. I would guess the difference is in the speedometers themselves. I broke my speedo in 1993, so I bought a used one from Automobile Atlanta, and I know it read 5 mph different than the old one at Memphis Motorsports Park. I'll bet our cars have about the same top end.
Bill
I was using Hoosier 225-45-15 also. I would guess the difference is in the speedometers themselves. I broke my speedo in 1993, so I bought a used one from Automobile Atlanta, and I know it read 5 mph different than the old one at Memphis Motorsports Park. I'll bet our cars have about the same top end.
Bill
