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Unread 09-23-2013, 09:51 AM   #1
dykaar
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Default rear suspension setup question

86 951, bilstein cup suspension (progressive helper spring and stock torsion bars), stock rubber mounts on torsion bar carrier and sphericals and metal bushings on the swing arms.

tires are 335/30-18 on 13 inch rims.

Camber? factory for 86 is -25 +/- 30' and -1 degree +/- 30' for US
Toe? factory for 86 is 0' +/- 5'

The settings for >90 are slightly different. WHat changed at the back of the car?

The intended use is street/track. I'm a track weenie, a nice stable feel is what I'm after. I tried positive toe at the front and didn't like it.

Regards,

doug

86 951 (http://pcaucr.org/media/image-galler...ll&gallery=224)
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Unread 09-28-2013, 09:02 PM   #2
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Doesn't quite read right? "tires are 335/30-18 on 13 inch rims"
Pics?
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Unread 09-28-2013, 09:49 PM   #3
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Its 13, as in the wheel is 18 inches in diameter and 13 inches wide. That's the widest wheel the 335/30 will take. Takes some getting used to, I know. There's a pic of the wheel here:

http://pcaucr.org/media/image-galler...ll&gallery=224

Regards,

doug

86 951 (http://pcaucr.org/media/image-galler...ll&gallery=224)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http://forums.bimmerforums.com/forum...hp?albumid=976)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
I apparently only buy cars designated by numbers
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Unread 10-01-2013, 03:15 AM   #4
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Wow, that’s a hell of a lot of tyre Doug! Doubt you’ll ever get them up to temp in Canada!!
Nice work on the body. Getting that done in the metal is real old school craftsmanship. As for setup, it depends on what you’re doing with the car. Is it road, road/track or track only? Basically the more track oriented, the more aggressive the settings. I’m running -4 f & -3 rear but we’re going to dial that back a bit as we can see that not all the tyre is getting full contact with the track. You really have to do a bit of testing to get it right.

NB: Re read your 1st post. So you will possibly want to change the settings for the track as the car will probably move about with big rubber and track settings on the street. The widest I’ve run is 305 slicks on the rear. I can’t remember the toe settings. On rubber that wide I’m not sure that you want too much camber. Maybe start with 1.5^ and go from there. What sort of tyre? How wide on the front? I’m running 295/30x18” all round on 11.5” wheels.
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Unread 10-01-2013, 09:12 AM   #5
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Thanks for the response,

Yes, I want to drive the street, AND track it. The cup suspension (With 275/40 and 255/40-17s was a little stiff on the street and little soft on the track, a nice compromise.

The fronts are hollow spoke 11x18 with 285/30s. All 4 tires are Michelin sport series I. I tried to find 295/30s cheap but no luck. lotsa 285s out there though. I have another set of BFG T/As in 285/30 in the root cellar but no 335s to match.

On the 17 inch wheel setup I had the front set for zero toe and -1.75 camber AND marks for backing the toe to the factory +10' (what units ARE those? seconds?) and correspondingly reduced camber ~-1.5.

The factory rear toe is 0, up to MY89, then +10' (both +/- 5').

The sidewalls on a 335 street tire are pretty darn stiff. This tire was designed for the viper, so its made to carry some serious bulk that my car doesn't have.

Regards,

doug

86 951 (http://pcaucr.org/media/image-galler...ll&gallery=224)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http://forums.bimmerforums.com/forum...hp?albumid=976)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
I apparently only buy cars designated by numbers
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Unread 10-04-2013, 07:59 AM   #6
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That's what I'd be concerned about, that you're not going to get the heat into them and you will actually have less traction than with a narrower rear tyre.

I don't really deal much with the toe settings but yes they'd be in minutes and seconds. I know we ran quite different settings depending on what type of racing or road we were going to run on.
Auto X type we would go with quite a lot of front toe, but back this off for road racing or street. It's amazing how much effect the tiniest changes make in toe.

I think that running a compromise between road and track in suspension is always going to be a bit dissatisfying. Not so much close to ok for both, more like not right for either.
Not that we can always have everything as we'd like it, but as you find what you want more from the car, you will figure out which way to go. All about budget and priorities.
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Unread 02-25-2014, 01:09 AM   #7
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Doug I'm sure you're well past this point, but I just found this thread and you've really done some nice work on the car! Just in time for the repaving of Mosport.

Just to second what Patrick said, given that you've gone to poly bronze and other solid parts at the rear and have 1.5x the tire width, I think you can safely say that factory settings are out the window.

In case it helps, some notes from what I remember:
I found the rear suspension a tough compromise on my cars. I often had to include between 1/16th and 1/32nd inch of toe-in per side to keep everything equal. These were both stock, late-armed cars with stock pickup points. The result is a car that takes early power somewhat more gracefully, for what it's worth.

As to camber, I ran as little negative as I could get at the rear (meaning as straight up and down as I could get -- about -2.25 degrees in my case on a 245 or 255 rear, as my cars were both very low) and got acceptable wear from about 80% track mileage. The stiffer the car laterally, the less negative camber you probably want, of course.

Every car and driver is different (and I don't claim to be an expert) but I had good luck with these settings and a square setup for a weekend 968 DE car, and lent it successfully to friends who really enjoyed it. I also had a pro drive it at the Glen and he affirmed that it was pretty neutral with a fresh Cup suspension ( running 350# front, 550# rear).

Front Toe: As close to 0 as possible
Front Caster: Max, both sides. Try to get them even, but get the most that you can. Adding Andy Pohlman's arms to my last car gave another couple of degrees because his blocks are taller.
Front Camber: -2.5, both sides.

Rear Toe: About 1/16" in total.
Rear Camber: -2.25, both sides.

You must be excited to get it going!
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Unread 02-25-2014, 09:54 AM   #8
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Default Rear suspension setup status

Thanks for the advive and the numbers. As of the end of last summer, I had (almost) convinced myself there was no rubbing in the rear, but dumping the throttle at low speed resulted in a "BANG" coming from the rear. I concluded the rear end was too low and I was hitting the bump stops. I had started the process of adjusting the ride height with the eccentrics on the swingarms, but with only one side in the air, everything was so loaded up I couldn't get it to move. Then it got cold and I started thinking about working on the dirtbikes in the warm basement.

In the front, I have Delrin front bushings and 968 rear bushings with Fabcar control arms. I found that if I tried max the Caster by turning the tab straight down, the control arm would just bind up, so I gave up and left it where it was still able to move.

Regards,

doug

86 951 (http://pcaucr.org/media/image-galler...ll&gallery=224)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http://forums.bimmerforums.com/forum...hp?albumid=976)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
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Unread 02-26-2014, 12:01 AM   #9
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Quote:
Originally Posted by dykaar View Post
In the front, I have Delrin front bushings and 968 rear bushings with Fabcar control arms. I found that if I tried max the Caster by turning the tab straight down, the control arm would just bind up, so I gave up and left it where it was still able to move.
Max caster isn't necessarily when you have the tabs straight down, though it may look that way. On the alignment rack, I got the max value with them a little farther around than that. The binding you're experiencing is a concern, though. If everything is loose (not aligned) anyway, it might be worth pulling out the front bolts and checking and greasing the delrin, then doing the same for the caster eccentrics while checking for wear and straightness, under the reasoning that if it's binding at one point in unloaded travel, it may also bind at other points while loaded.

If you're getting a mechanical bang under acceleration, I would have a look at the transmission mount and your axles, too. If you can easily swing the transmission around, the torque tube may be hitting the "crash hooks" on the torsion tube carrier.

I haven't checked the UCR site in a while -- what stage is the body work at these days?

Really cool project.
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Unread 06-12-2014, 08:53 PM   #10
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Update. I raised the rear ride height using the eccentrics on the swingarms. I think it was just too low, so when I mashed the throttle the rear end went squat and bottomed out. Seems to be better now.

Any comments on alignment shops? There's a local race shop that's done some Porsches, but does it with alignment plates, Vs a generic repair shop that uses a Hunter laser rig but the only Porsche they ever saw was mine. I have the eccentric tool for the swingarm, so that's not an issue.

Body-wise I think the rear wheel now actually fits without hitting anything. I hammered the fender lip flat most of the way around the leading edge.

The original torsion bar carrier seemed to be offset to the driver's side by 1/2" but that was after I wrecked, although George B. at PCA said they're all like that. The used one I got to replace it seems to be centered. Go figure.

Assuming I can get the thing aligned. I plan to drive around the rest of the summer and see if anything falls off, maybe an autocross or DE in the fall. Then see about getting it painted.

Regards,

doug

86 951 (http://pcaucr.org/media/image-galler...ll&gallery=224)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http://forums.bimmerforums.com/forum...hp?albumid=976)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
I apparently only buy cars designated by numbers
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Unread 06-16-2014, 11:02 AM   #11
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i hope nothing falls off either. You are way beyond me so I cannot add anything technical.
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Unread 06-16-2014, 11:23 AM   #12
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Cruise,

For a guy with a picture of an engine disassembled for an avatar, I doubt that.

Regards,

doug

86 951 (http://pcaucr.org/media/image-galler...ll&gallery=224)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http://forums.bimmerforums.com/forum...hp?albumid=976)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
I apparently only buy cars designated by numbers
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