building saab900 for trackdays

[ric]

ok it´s possible to make a good alignment in a press but the problem occurs when you are on a track day and want to fiddle around with the angles, a workshop press is quite heavy to put in the trunk and it takes a few minutes to dismantle and assemble the rear shaft.
Erik Carlsson "på taket" (on the roof) drove saab 93 and 96 back in the old days he did put a few sandbags in the trunk and had a nice little jump with his car to bend the rear shaft. Not a perfect procedure but it worked for him.I think if he wanted it then I want it now.
I also believe it´s important to consider the movement in the tyres compared to the rims and the shaft itself is probably twisting and turning a bit, if they where solid the 0 angle would be nice.
Many fast roadcars have a lot of camber for some reason.
I want to go fast in corners on tarmac mainly and I know I will get less grip when I brake if I have more camber at the rear.
About the front and the spacers at the rear bottom wishbone I read here and other places that the car will dive more at braking but it could be reduced by using harder front springs.I have to think a little about that.

By the way the red dots on the map at sellholms site is no dealers just big costumers.

[paulh]

I think there was some discussion before that people were lifting the inside tires... Thats the only way you can get a camber change on the rear axle.
My opinion is that if a rear tire is lifting it is representative of other problems in the chassis setup that need to be dealt with.

i had that happen with my 86 notchback, with intrax springs, and only a rear sway bar, and that car handled great, but i could see how having an entire wheel off the ground could be considered bad... i suspect the reason it isnt more common of an issue is because the hatchbacks are so floppy in the back!

Paul

[vinkel4]

Would it work to cut the rear axle in half, weld two plates with 4 holes on each end, bolt them together. When you want to change the toe in for example you put shims in at the top and lower bolt at the rear to get more toe in. For more camber you just put shims in the bottom. Hard to explain when I don´t know anymore english and can´t draw a picture.

On the Oplel Corsa rallycar I had some years ago it kind of worked that way. The axel was not cut in the middle but there was seperate shafts witch was bolted to the axel on each side. There was plates on each side of the axel in witch the "wheel bearing shafts" (?) were bolted with 4 M8 bolts. To adjust the angels you simply placed shims between the plate and the flange on the wheel bearing shaft.

( is it called wheel bearing shaft or hub shaft.... or somthing else???.)

[99Super]

To be perfectly honest, this discussion should be in the tarmac forum...

Anyway; nobody said a bent axle was a perfect solution, but it works for me and when any of you can beat me on the track, I'll start to think differently about it. Until then...

As far as flat contact patches, mine do become flat when cornering and I have little to no inner tire lift. Turn in is quick, push is nearly gone. This is (and I've said it before) at the expense of stability while braking while corning. Of course, you shouldn't be doing that anyway and it's a very good reminder of what NOT to do

It takes a bit of tuning to get the rear end of these cars to actually work. When I started Auto-Xing, the rear wheel would be half way up the cone. You can see it in the pic of my car in Grassroots. It corners very flat now.

I picked the wrong road when I gave Geoff a ride a year ago

Also, I can swap out a rear axle in under an hour if I really want to go back to 0* camber.

[TRAILINGTHROTTLE]

had i been aware that you were so much faster than me i never would have questioned your camber decisions. sorry.

[Geoff]

I picked the wrong road when I gave Geoff a ride a year ago

I had a good time! Of course I had fun riding around in the Pumpkin too!

[Hans]

I saw an adjustable idea........ I don't remember where. I think it was a 900 rear axel, It had a 1" or so flat steel strap laid along the top, welded on each end above where the trailing arms attach. At the center of the strap/axel there was a nut welded in the same plane as the strap through which a large vertical bolt could be threaded to exert downward pressure on the axel. As the bolt was tightened, the ends of the strap pulled on the ends of the axel and bowed it downward and creating a little neg camber. Seemed like a neat easy experiment for adjustability but who knows? I guess you could try the same for toe. Pics are worth a thousand words..... Ha

Image below is of a similar idea I had a while back using a truss rod on each side that went from the top of the spindle down to the center of the axle. Tighten the truss rods and they pull in, arcing the axle up and imparting a negative camber at the wheels. I mentioned it on Saabnet and Brad Schaffner @ kcsaab.com says he's been doing something like this for a while, so maybe his set-up is what you saw? He also noted that setting up their circle track cars involves much more tweaking in the rear than in the front.



Note that you would need to fab some means to allow the p-bar to move up and down, or if you are hardcore, move it from the top of the axle to the side, as the trusses otherwise occupy the same space.

[99Super]

OK, so how difficult would it be to fab a new, fully adjustable, rear axle?

[Luke]

It's kinda funny, because I was actually thinking of doing the exact opposite of that, with the rods sloping up to a tower on the middle, essentially forming a truss... to PREVENT the axle from bending

[ric]

Yes I am really sorry I realized a couple of days ago when I was reading about some one that overhauls his head and gearbox on the bare ground! that I was in the wrong place. I should be here in "general saab racing" from the beginning of course. ( among the other pavement weenies )
Thanks for moving me here !
I´m not saying that anyone is faster or slower, I guess most people here have an interest in cars.
I am only curious about how to make my car better because a good set up is worth a lot. I´m not a good driver I just drive faster than I can handle
And I see the set up of the car more important than loads of bhp.
And of course there is always someone faster no matter what you do with your car.
About the rear end it´s only that I hear so many people say the car handles so much nicer. Probably I just have to improve my driving skills instead

[Hans]

It's kinda funny, because I was actually thinking of doing the exact opposite of that, with the rods sloping up to a tower on the middle, essentially forming a truss... to PREVENT the axle from bending

Ha!

A fully adjustable axle would be sweet...

[ric]

Me and my brother was dreaming one day in the garage about putting a complete front suspension in the back ( we are not the only one I guess)
and then it comes very close to build 4wd.
But you will get all possible adjustments. I have not weight all the parts
but the rear shaft with all parts i quite heavy so maybe it´s not a big difference.

[Geoff]

I've been thinking about the front suspension in the rear for a while now. I don't know how it will affect handling but it will allow for much more adjustment so one would think you could tune it much easier. I have a front clip from a 900 at home, waiting for the conversion.

A few people have done this in the US and Canada but I think they have all put the engines back there too to create a mid-engine car. I want one of those too!

[Crazyswede]

There is a guy near Josh and I who built an iceracer/hill climb car where they basically cut the engine bay out of a 900 and welded it in the rear of another 900. They had an 8v non turbo engine and transmission installed back there along with the same front suspension setup, a welded steering rack etc. They said the car really didn't perform as good as they thought it would. However, it would probably react better if the engine wasn't in the back.

[ric]

We have a front end here in the garage as well, I used it when I did build
my downpipe and my intercooler it was very useful !
We have also tested it in the back of a saab 96 it looked GREAT !
I wish I knew how to put pictures in here, but I put them up on my page, just have to do one more album. Coming soon.