Setting up a C900 for the Track

THE place for technical discussions concering the construction and preparation of SAABs for all forms of motorsport, Rally, Road Racing, Auto-X etc....
User avatar
Jordan
Site Admin
Posts: 4057
Joined: Fri Oct 13, 2006 2:38 pm
Number of Saabs currently owned: 6
Location: Vernon, CT
Contact:

Setting up a C900 for the Track

Postby Jordan » Sat Aug 30, 2014 4:28 pm

So now that the initial build is over. I'm looking to do some development in the road handling department. Initial research indicates...more research is needed. So many conflicting theories, anecdotes and science is making my head spin.


Do you guys have any insight from experience with the C900 you want to share?

My inclination is to keep things relatively stock. Not too low, not too stiff, and let the geometry work as it should.

I've done a few things that I'm hoping will optimize the car for road racing.

- Run a reverse staggered 225/205 tire set. The thought is that with the extra weight in the front 205s seemed to get overloaded fairly easily. The wider tire will reduce the slip angles, heat and load better. The rear is just along for the ride

- Dropped the car probably 1.5 inches and used 375in/lb springs in the front. I'd have to calculate the rears, but they are probably 1.5 coils off stock.

- Bilsteins with some complementary valving.

- Increased negative camber. Currently , the car sits with about -2.5* which I think might be a bit excessive as it doesn't allow the tires to sit flat because of the camber curve AND combination of relatively low spring rate. Zero Toe. Caster is unknown, but the steering effort feels good even without power steering and wide tires.

- Front and Rear stock sway bars

- 9000 Quaiffe? Shhhhh.....


I took some rough measurements (rough because it was the best I could do myself with a tape measure)

I entered the data into this online suspension tool I found:

http://www.vsusp.com/#0.8%26project_nam ... _camber%7D


Weights:

Currently with a half tank of gas and no driver they are:

LF:733lb
RF:702lb
LR:400lb
RR:378lb

So pretty equal left/right (without 200lb drivers)
64.8% Front/Rear
2215lb total

Optimization would be for mid to high speed corning (left AND right)

What are the theories you use? What would you look at next?

User avatar
SwedeSport
Posts: 3026
Joined: Mon Jun 15, 2009 9:52 am
Number of Saabs currently owned: 5
Location: Pottstown, PA
Contact:

Re: Setting up a C900 for the Track

Postby SwedeSport » Sun Aug 31, 2014 8:11 am

I had a long discussion with Jack Lawrence a while back. His theory was that best suspension geometry was achieved when the front lower control arms were parallel to the ground.

I agree that 205's are a bit smallish. Fitting 225's is the way to go, but I would put them on all 4 corners.

A stock suspension with good springs, shocks, and sway bars is a great setup. I'd mess with spring rates the most.

Box the arms to stiffen it up.

I would play around with the rear spoiler a bit. Rake it back more, or remove it all together, and you may pick up a few mph down the straights.

Seems to me that for an endurance racing situation, a simple stockish approach is best.
Swedesport Motors, Apparel and Accessories for SAAB Junkies.
Http://Facebook.com/swedesportmotors
Swedesportmotors@gmail.com

User avatar
Jordan
Site Admin
Posts: 4057
Joined: Fri Oct 13, 2006 2:38 pm
Number of Saabs currently owned: 6
Location: Vernon, CT
Contact:

Re: Setting up a C900 for the Track

Postby Jordan » Sun Aug 31, 2014 1:09 pm

Yes, for endurance racing the "ideal" setup probably going to amount to winning or losing because of it, unless it adds stability and driveability (which I'm not ignoring). I posted this more as an exercise in education and the ability to test out some theories. I haven't seen a very good development of a c900 written anywhere, so I thought I might start the discussion.

Funny thing you mention Jack Lawrence. I did find an article he wrote from his Sonett racing dev which I'm sure most can carry over to the 99/900. The Sonett seems like it has an even worse weight distribution although everything about it is lighter.

SUSPENSION: Standard control arms and mounting points on the chassis are used although the amount of elasticity in the inner bearing mounts is limited by replacing the standard bushing with press in steel jacketed bearings containing much less rubber. The reduced elasticity restricts detrimental geometry changes during cornering G forces, brake, and power application. Suspension components are magnafluxed and shotpeaned when first installed and periodically magnafluxed along with complete disassembly and inspection after about 10 races. The critical parts are all painted with a thin coating of light colored paint to make on car inspection easier.

The coil springs used front-and rear are the product of experimentation and are as low a rate as possible. Front unsprung weight is considerable, making choice of springs difficult.

The sway bars have been the product of experience also. The front bar is 3/4" (19mm) and the rear 5/811 (15.9mm), both with adjustable moment arms. Limited slip in the front allows a front sway bar diameter versus rear bar diameter much like that of a rear drive car. With no limited slip in the front the car would probably not benefit from a front bar, just a heavier rear, although there is no substitute for the limited slip combination.

Front shock absorbers are Koni gas over adjustables. Non gas filled shocks in the front will go away in less than 1/2 hour on a hot track. Rear shocks are standard adjustable Konis.


So I like the bushing idea, I know SAAB competition did something similar. His notes on the sway bars and coil springs are interesting. It is a great departure from the higher springs rates I've seen on some other track prepped cars. His note about the LSD also makes sense, but "as low as possible" is not very descriptive.

DeLorean
Posts: 1195
Joined: Sat Mar 31, 2007 9:54 pm
Number of Saabs currently owned: 9
Location: Pennsylvania, Forever!
Contact:

Re: Setting up a C900 for the Track

Postby DeLorean » Sun Aug 31, 2014 7:33 pm

Well, I just got back from the Jefferson Track trial with the 88 900, and I have a few thoughts some may or may not be useful. My car with 2 degrees negative camber, hoosier A6's and worn out bilstines is a little bit of a mess in corners. Sure, the car hangs on pretty well, but radar speeds down the straights say I should have been the fastest car in SMF today, and I was beaten by a pretty tarted up honda Civic and a pretty set up VR6 golf, they both just got around those corners better than I could. Only by about 2 seconds and 1 second respectively. I should say though, I was also the only car in the pack today without an LSD, and I still got 3rd place. Radar speeds show that I was making up a good bit in the straights and my losses were in the corners.

I think the skinny front tires DO get overloaded. They run REAL hot, and roll over, even at very high air pressures if you are getting real good grip. My fronts get so hot they would burn you if you left your hand on them for too long. Also, these cars with negative 2 degrees of camber and really grippy tires really get upset by road bumps, dips, general funnyness, and if you don't set up your braking zones right, you can get the tail right out real quick. This can be beneficial, if intentional, if unintentional it's dangerous. There was one spot on the track that when you walked it looked like nothing bit a straight flat portion of road with a light turn. When I hit it with my car doing 80 setting up for the next turn coming right up, suspension went through all of it's travel, banged the skid plate, upset the car greatly because it was in a light turn and took about a full second to settle itself, every time I hit it, it was rather un-nerving. The Honda and Golf drivers said they both handled this with ease.

Sometimes the car does this thing where you come into a corner full tilt, and a 4 wheel side slide turns into a rocking motion where the whole car almost feels like it gyrates left to right as it's sliding. This is kind of fun in an S because when you transition very quickly to the other direction, if you are at the wrong point in this weird gyration both wheels on the unloaded side of the come off the ground, sometimes WAY off the ground, and you have "a moment" where you feel like it's going over. This probably would only ever happen with race tires though.

I don't want to toot my own horn, but today at the track I was the only one out of all the Saab drivers who managed to not spin & stay on course, plus managed the fastest time of the Saabs ;) so, I might have a few ideas that make a little sense.

Optimum set up in my opinion? We probably need to about double our spring-rate, or maybe get some custom progressive springs made. The car also needs to sit low. Custom valve the shocks so they match. That alone may solve the main issues with our "smooth ride" which turns into scary time with good tires & a track event. Stock sway bars would probably be fine. We also need to get the same camber in the back axle as we have in the front A-arms. I think that's probably a good starting point and then see how it hangs with other cars at the track. These things would be a force if they could hold a corner like a set up honda civic.
Less brake more gas!

User avatar
Jordan
Site Admin
Posts: 4057
Joined: Fri Oct 13, 2006 2:38 pm
Number of Saabs currently owned: 6
Location: Vernon, CT
Contact:

Re: Setting up a C900 for the Track

Postby Jordan » Sun Aug 31, 2014 8:45 pm

So what are you currently running now for springs/shocks etc.

With slicks vs. performance tires, you're definitely going to need more spring, I'm just not sure where more is yet.

Be careful that as you lower the front of the car the instant roll center gets lower and lower to the ground which increases the forces of weight transfer (requiring even more roll stiffness).

It also seems that the LSD can make a big impact on how the car gets setup.

DeLorean
Posts: 1195
Joined: Sat Mar 31, 2007 9:54 pm
Number of Saabs currently owned: 9
Location: Pennsylvania, Forever!
Contact:

Re: Setting up a C900 for the Track

Postby DeLorean » Sun Aug 31, 2014 9:08 pm

these are the springs that it has- http://www.skandix.de/en/spare-parts/su ... m/1013185/

Stock valved Bilstein's with over 100K, and one that is leaky. Does not fail the bounce test yet though! But that is on my list of rebuild/replace soon.
Less brake more gas!

DeLorean
Posts: 1195
Joined: Sat Mar 31, 2007 9:54 pm
Number of Saabs currently owned: 9
Location: Pennsylvania, Forever!
Contact:

Re: Setting up a C900 for the Track

Postby DeLorean » Mon Sep 01, 2014 8:17 am

The winner with the Honda last weekend said he was making 92 MPH radar speed where I was making 104 MPH, and he still won :lol: 1st, 2nd and 3rd all have our videos posted on the facebook if anyones interested 1st place was Chris Carlisle, from Saxonburg, 2nd place was Jason Ackerman from Pottstown, and 3rd was Jeff Henderson from Reading.

It's interesting to see in all 3 videos the difference in driving dynamics of the honda Vs the golf Vs the Saab. These links may or may not work

1st https://www.youtube.com/watch?v=aLzdTfn ... ture=share
2nd https://www.facebook.com/video.php?v=10 ... =2&theater
3rd https://www.facebook.com/video.php?v=10 ... =2&theater

The videos don't all start at the same place. In mine, I'm not racing till I go by the timing tent, which happens around 1.16 seconds in.
Less brake more gas!

User avatar
Jordan
Site Admin
Posts: 4057
Joined: Fri Oct 13, 2006 2:38 pm
Number of Saabs currently owned: 6
Location: Vernon, CT
Contact:

Re: Setting up a C900 for the Track

Postby Jordan » Mon Sep 01, 2014 8:53 am

Your situation with the suspension reminds me of when I drove a 900 on the track with kybs. I think you are on the right track with changing the shocks.

User avatar
SwedeSport
Posts: 3026
Joined: Mon Jun 15, 2009 9:52 am
Number of Saabs currently owned: 5
Location: Pottstown, PA
Contact:

Re: Setting up a C900 for the Track

Postby SwedeSport » Mon Sep 01, 2014 10:48 am

Jeff,

There are a few places in your video where you could wait a tad longer before turn in. I bet with some minor adjustments in your line, you could have caught Jason.
Swedesport Motors, Apparel and Accessories for SAAB Junkies.
Http://Facebook.com/swedesportmotors
Swedesportmotors@gmail.com

DeLorean
Posts: 1195
Joined: Sat Mar 31, 2007 9:54 pm
Number of Saabs currently owned: 9
Location: Pennsylvania, Forever!
Contact:

Re: Setting up a C900 for the Track

Postby DeLorean » Mon Sep 01, 2014 12:09 pm

I had been thinking about that, and I had watched that video just before run 3 was about to happen Sunday afternoon. About 10 minutes before I was going to run, a large T-storm rolled through, and.... that was that. Times were set.
Less brake more gas!

tirediron
Posts: 148
Joined: Mon Oct 08, 2012 10:22 pm
Number of Saabs currently owned: 7
Location: NH

Re: Setting up a C900 for the Track

Postby tirediron » Mon Sep 01, 2014 9:37 pm

suspension setup is probably my strongest topic, especially with these cars. although much of what I know is circle track setup, much of it is the same. the only real difference I see is that I can use cross weight changes to turn the car more or less, because I am only turning left.

obviously these cars are nose heavy, as much as you can get off the front the better. your rear weight is acutally slightly better than mine. I am currently at 2260lbs total with me in it (I weigh 180). rear weight is 34.3%. I have my fuel cell tucked as close to the axle as possible, with the idea that it is best to have the weight more central even though moving the cell farther to the bumper brings rear weight percentage up.... verdict is still out on that one, my cell is moveable so I can try different positions.

my spring setup is rather unconventional. I run no sway bars. 400lb front spring. 7-900lb rear. my theory for stiffer spring and no bars is this: fore/aft weight transfer is never really a good thing in a FWD car. we use super soft rear springs occasionally on RWD cars to get traction out of the corner. no dice with the drive wheels on the wrong end. i was running a rear bar only, but it tends to lift the inside rear tire a lot under braking and turn-in. i can generate enough front traction to make the car very loose in. removing the rear bar and raising rear spring rate allows the wheels to move independently and keeps the inside tire planted. this equals more rear traction on turn in and under braking. my theory, most don't agree but i have won plenty of races like this. keep in mind i am running less tire than most of you, 195/60R14 Dunlop direzza. open diff, ran a welded one for a while, didn't like it.

caster: pretty much as much as possible. i think i have 4 degrees or so. more caster means more camber as you turn the wheel.

run a brake proportioning valve for F/R bias that you can reach from the drivers seat. it's a band aid, but you can help with a loose or tight car under turn in without coming in the pit.

2 things that apply to setting up any car that have helped me the most are pretty basic and obvious, but worth mentioning. always sort out corner entry problems first. if it's loose on entry you exit is probably going to suck also.

always focus on adding traction where you don't have it rather than just neutralizing the car. running a smaller rear tire may feel better but it not necessarily faster. adding front bite with the same size tire will be faster and feel better.
-matt

User avatar
Luke
Site Admin
Posts: 3387
Joined: Tue Sep 19, 2006 11:12 pm

Re: Setting up a C900 for the Track

Postby Luke » Tue Sep 02, 2014 3:20 pm

I'll just add in that I agree with what jordan said about the roll center. Don't go too low in static height or the roll center becomes way too low and even with a very stiff spring you'll find the car wanting to lean heavily. On the rally car with coilovers I experimented with rates all the way up to 600 on the front (which was almost undriveable) and finally settled on 375 being around ideal for the front on a tarmac rally stage which shouldnt be too much different than a hill climb. Now the motion ratio was a little bit different on that car because of the custom upper a-arms so you may have to increase those rates about 20% to translate to the stock suspension geometry. I used an Addco bar on the front only. That helped a lot with body roll and also kept the car better settled during fast transitions. I prefer 0 toe. Toe is really important I've found, make sure you've got in dialed in, it can really make the SAAB unstable if it's not...
Roll center is also important in the rear too.... and you want the panhard nearly parallel at static height or you will get weight jacking there too...

tirediron
Posts: 148
Joined: Mon Oct 08, 2012 10:22 pm
Number of Saabs currently owned: 7
Location: NH

Re: Setting up a C900 for the Track

Postby tirediron » Tue Sep 02, 2014 8:45 pm

luke are the custom upper arms you mention different in length or spring placement to account for the wheel rate vs spring rate difference? I haven't run anything but stock.
-matt

User avatar
Jordan
Site Admin
Posts: 4057
Joined: Fri Oct 13, 2006 2:38 pm
Number of Saabs currently owned: 6
Location: Vernon, CT
Contact:

Re: Setting up a C900 for the Track

Postby Jordan » Thu Sep 04, 2014 5:54 pm

Luke's a-arms are modified to run a coil over with a 6?" travel and jaguar ball joints (we kept bending/breaking the stock ball joint bolts!) I'm sure you can find some photos if you look through the '73 rally car build thread, or maybe he has some handy.

So I just finished reading Carroll Smiths book "Tune To Win" (hey, I'm waiting for a baby to be born here).

It clarified many concepts for me and had some sound practical advice. I am, however, still unclear about a few things and how to approach them, at least from an academic point of view. The book was really for the most part written for optimizing an already optimal chassis of a Formula or CAN AM race car, not for a FWD Saloon.

So what I'm confused about still is the whole lateral load transfer distribution and roll stiffness concept.

I think I understand that chassis roll is a consequence of cornering force acting through a moment arm from the CoG and the roll axis. But how does roll stiffness distribution effect where load is transferred?

My understanding is that in a corner, load will be transferred from centrifugal force regardless of suspension stiffness. But this can be skewed longitudinally?

tirediron
Posts: 148
Joined: Mon Oct 08, 2012 10:22 pm
Number of Saabs currently owned: 7
Location: NH

Re: Setting up a C900 for the Track

Postby tirediron » Thu Sep 04, 2014 7:08 pm

I could be misunderstanding what you are asking, most of you are smarter than me. so bear with me.

in a very basic sense:
the car rolls, the rear suspension rolls less due to susp geometry, stiffer spring, sway bar, whatever. rear tire overloads sooner than front tire = loose car.

when the front resists rolling more than the rear = tight car.

does that help?

centrifugal force can play a part as well with front vs rear static weight distribution, but less actively.
-matt


Return to “SAAB MOTORSPORT TECH”

Who is online

Users browsing this forum: No registered users and 1 guest