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 Post subject: Extreme body roll & dive
PostPosted: Sun Jul 09, 2006 9:12 pm 
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I am experiencing a great deal of understeer or push when racing. I race on an 3/8 mile semi-banked oval. I have about 5 deg neg camber on the front right and about 4 deg pos on the front left. However, check out the attached photos of the body both diving and rolling (photos below). I cannot help but think that this has a lot to do with my problem sticking to the track (too much camber change, weight transfer, high CG??).

I have stripped the car of most everything and added a roll cage. Weight is about 1740 lbs without the driver. It's just so frustrating not being able to stick and sliding up the track instead.

Typically I will enter the turn quite nice. I have given it some toe out and I think that has helped the turn in. However, at about mid-turn the Swift is sliding and I am pushing up the track and giving up the inside. What's worse is that I am having to countersteer quite far (almost full lock) due to this extreme slip angle. When I should be accelerating out of the turn I'm rather trying to get a grip from the slip.

Due to the rules I have to stay with stock or stock replacement parts. However, I can choose another "junk yard" spring and/or shock (from any other vehicle) as long as it fits like stock.

Just so that you know, this Swift is riding a little higher due to the tires that I have to run with. I had to take off the 185/60s and either run with 195/65s or 70s. I have the 65s and the ride height has definitly increased while the handling has decreased.

I have read many things in the forums about lowering and cutting springs, but does anyone have any information about spring swaps from other vehicles. I read about a Swift 95+ spring being a higher rate one, but it is also taller too, right? Am I even right to be thinking of stiffer springs in the front? And what about the rear?

I guess that I am open to shorting the springs if that will help although the rules state no modifications such as heating & cutting. While I have seen the tech guys disqualify cars for performance parts and coil-overs, I have never seen them get picky with something that looks stock. Other racers have told me this themselves, too, so I'm guessing that they have "played" around with the length of the springs as well.

Also, any help with "preloading" the anti-roll bar would be helpful (front & back, which side to load, methods).

I appreciate your feedback and patience as I am still trying to get my head wrapped around all of the intracies of suspension tuning. I am a motor head, but I've never given much thought to shocks, struts, and springs until lately.

I am open to all suggestions.


Last edited by Swift73 on Wed Jul 19, 2006 6:00 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 10, 2006 3:19 am 
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use the '95+ springs cut down a little, this will give you a much higher spring rate. replace the swaybar bushings & endlinks with polyurethane units and make sure you use LOTS of lithium grease to keep them well lubricated.
you may also want to try going to a smaller '89-'91 gti or even the '89-'94 3cyl front swaybar, I know the autocross guys often remove it entirely; this will make the car much more prone to oversteer, and if you can get the back-end to slip when you enter the corner, you can use the throttle to slip or pull you from there.

you can also get the rear end to slide earlier by running a taller tire (eg. 70 series) on the rear and a shorter tire (eg. 65 series) on the front.
not sure if it would work as well on your track as it does on gravel, but a little bit of left foot braking could get the rear end to brake free at the start of your turn as well..

not sure what they consider 'stock', but you could always try to source a jdm suzukisport lsd ;)

good luck & keep us posted.

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 Post subject:
PostPosted: Mon Jul 10, 2006 3:54 am 
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n1tr0 wrote:
use the '95+ springs cut down a little, this will give you a much higher spring rate. replace the swaybar bushings & endlinks with polyurethane units and make sure you use LOTS of lithium grease to keep them well lubricated.
you may also want to try going to a smaller '89-'91 gti or even the '89-'94 3cyl front swaybar, I know the autocross guys often remove it entirely; this will make the car much more prone to oversteer, and if you can get the back-end to slip when you enter the corner, you can use the throttle to slip or pull you from there.

you can also get the rear end to slide earlier by running a taller tire (eg. 70 series) on the rear and a shorter tire (eg. 65 series) on the front.
not sure if it would work as well on your track as it does on gravel, but a little bit of left foot braking could get the rear end to brake free at the start of your turn as well..

not sure what they consider 'stock', but you could always try to source a jdm suzukisport lsd ;)

good luck & keep us posted.
Thanks N1tro.


Last edited by Swift73 on Wed Jul 19, 2006 6:03 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 10, 2006 5:19 am 
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Have you played with the rear toe? Some toe out in the rear should help along with the stiffer springs.

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1992 Swift - Parts car (gone)
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 Post subject:
PostPosted: Mon Jul 10, 2006 5:29 am 
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KYB replacement strut info:
http://www.kyb.com/catalog/index.php?Ac ... 1&x=27&y=5


Last edited by Swift73 on Wed Jul 19, 2006 6:10 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 10, 2006 5:35 am 
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Gasoline Fumes wrote:
Have you played with the rear toe? Some toe out in the rear should help along with the stiffer springs.


No, haven't done that at all, but that's a great idea.


Last edited by Swift73 on Wed Jul 19, 2006 6:12 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 10, 2006 6:29 am 
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Due to the very short wheelbase and narrow wheeltrack these cars tend to pitch and roll quite a bit, you WILL need the +95 springs, lose the front sway bar or add a rear one if you don't have one and as Gas Fumes mentioned dial a little bit of toe out on the back, this will increase your slip angle, I think with you running bigger tyres the rear semi trailing arms sit slightly higher giving you toe in and possibly positive camber.

Think of it this way, if you make the one end stiffer then it will give you more grip at the other end and vice versa.
Softening the front end will do a similar job as stiffening the rear springs however there are always trade-offs, softening the front will increase body roll and therefore weight transfer.

I think that the 5 deg neg camber is what gives you the good initial turn in but the rear still has too much grip, I found an adjustable rear swaybar made a MASSIVE difference to my race car, I dropped almost 5 seconds off a 1:55min lap.


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 Post subject:
PostPosted: Mon Jul 10, 2006 7:26 am 
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You can get the KYB's at tirerack.com. Look under 89 swift gt/gti. They're all the same.

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 Post subject:
PostPosted: Mon Jul 10, 2006 10:16 am 
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get yourself some mk4/5 shocks while you're at it, the stock units are not gas charged so you can make yourself a set of phonis :lol:

turn them upside down
drill a small 1/8-1/4" hole roughly 3/8" from the top of the shock through the outter layer and drain out the existing oil into a measuring cup...
replace it with the same amount of motorcycle shock oil in your desired weight .. ~20w-30w depending on how stiff you want it. btw, atf ~20w
cap the hole with a bit of silicone/urethane and a really short sheet metal screw, or you could even weld it shut if you're skilled.

should do you just fine.

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 Post subject:
PostPosted: Mon Jul 10, 2006 11:28 am 
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If I remember (and it seems to make sense):

Body Roll [does not equal] Weight Transfer

Body roll is an indication of weight transfer, but it's relative to the roll stiffness (or something). Replacing the dampers with solid links will eliminate almost all the body roll, but won't reduce weight transfer.


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 Post subject:
PostPosted: Mon Jul 10, 2006 12:32 pm 
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Correct.

Weight transfer is a function of g-force and center of gravity only.

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 Post subject:
PostPosted: Tue Jul 11, 2006 3:04 pm 
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Location: burlington,ontario
n1tr0 wrote:
get yourself some mk4/5 shocks while you're at it, the stock units are not gas charged so you can make yourself a set of phonis :lol:

turn them upside down
drill a small 1/8-1/4" hole roughly 3/8" from the top of the shock through the outter layer and drain out the existing oil into a measuring cup...
replace it with the same amount of motorcycle shock oil in your desired weight .. ~20w-30w depending on how stiff you want it. btw, atf ~20w
cap the hole with a bit of silicone/urethane and a really short sheet metal screw, or you could even weld it shut if you're skilled.

should do you just fine.


will this work on mk3 shocks aswell, i have mine off the car right now changing over to some gt springs and the shocks seem shot(can move them with very little effort)


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 Post subject:
PostPosted: Tue Jul 11, 2006 3:59 pm 
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http://www.teamswift.net/viewtopic.php? ... rallycross

I wish I had seen this a little sooner.
What are you running, second gear with the taller tire?
You may want to see if you can drop lower than the stock tire size, and run up one gear. Those tall tires are probably killing you.
You should probably try to aim for about 6500-7000RPM at the end of the straight.
Apparently the later 95+ control arms are longer, as well. This will hurt your wheel rate, but will help with your camber, and handling. 5 degrees negative is alot of camber.
Get that car as low as you can get away with.

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 Post subject:
PostPosted: Tue Jul 11, 2006 9:57 pm 
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I have removed the front sway bar to help eliminate the understeer, but am wondering if this is going to intensify the body roll situation that I already have.


Last edited by Swift73 on Wed Jul 19, 2006 6:15 pm, edited 2 times in total.

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 Post subject:
PostPosted: Tue Jul 11, 2006 10:25 pm 
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Dattman wrote:
Due to the very short wheelbase and narrow wheeltrack these cars tend to pitch and roll quite a bit, you WILL need the +95 springs, lose the front sway bar or add a rear one if you don't have one and as Gas Fumes mentioned dial a little bit of toe out on the back, this will increase your slip angle, I think with you running bigger tyres the rear semi trailing arms sit slightly higher giving you toe in and possibly positive camber.

Think of it this way, if you make the one end stiffer then it will give you more grip at the other end and vice versa.
Softening the front end will do a similar job as stiffening the rear springs however there are always trade-offs, softening the front will increase body roll and therefore weight transfer.

I think that the 5 deg neg camber is what gives you the good initial turn in but the rear still has too much grip, I found an adjustable rear swaybar made a MASSIVE difference to my race car, I dropped almost 5 seconds off a 1:55min lap.


I have removed the front sway bar, but I'm wondering how this is going to impact the body roll situation. I'm wondering if it will make it worse or not. I really don't know. I do see that the more that the suspension deflects from the body roll the more I will lose camber, and thus cornering ability.

I'll be sure to let you know how it works on the track. Thanks!


Last edited by Swift73 on Wed Jul 19, 2006 6:20 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 11, 2006 10:25 pm 
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suprf1y wrote:
http://www.teamswift.net/viewtopic.php?t=17990&highlight=rallycross

I wish I had seen this a little sooner.
What are you running, second gear with the taller tire?
You may want to see if you can drop lower than the stock tire size, and run up one gear. Those tall tires are probably killing you.
You should probably try to aim for about 6500-7000RPM at the end of the straight.
Apparently the later 95+ control arms are longer, as well. This will hurt your wheel rate, but will help with your camber, and handling. 5 degrees negative is alot of camber.
Get that car as low as you can get away with.


Affirmative, running in 2nd gear w/ larger circumference tire (for "effective" gearing change). I was originally running w/ 185/60-14s and car lacked power in 3rd gear, but 2nd gear was great; however, I was having to upshift along straightaway, just before arrival at turn entry/corner. This upshifting & downshifting was hurting my lap times on this short track (3/8 mile) and I couldn't keep up with the other cars. Most of them just run in 3rd gear. When I just run in 3rd the car lacks the "umph" to make any moves. I actually had better lap times just running in 2nd until the rev limiter kicked in. This was only a short-term solution for that week. I knew that I was going to have to try something else.

Making the change to the 195/70-14s allowed me to run strong from corner to corner without having to shift. But as you already know, now the CG is higher and that's killing me, as you put it. :)

I guess that I could run in 3rd gear, but I'd have to get a tire smaller than the 185/60-14 that I was running before. I wish I could get my hands on a set of 185 or 195/45-14s just to see what they would be like. I imagine that I would have to go to something around that size to consider running in 3rd gear. I could also go down to a 13" wheel and then I'd have more to choose from, but that would have a drawback, too, I guess.


Last edited by Swift73 on Wed Jul 19, 2006 6:24 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 11, 2006 11:03 pm 
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martinq wrote:
If I remember (and it seems to make sense):

Body Roll [does not equal] Weight Transfer

Body roll is an indication of weight transfer, but it's relative to the roll stiffness (or something). Replacing the dampers with solid links will eliminate almost all the body roll, but won't reduce weight transfer.

Roy Dean wrote:
Correct.

Weight transfer is a function of g-force and center of gravity only.


Okay, I see. Due to the change in velocity, specifically either the increase/decrease of speed and/or direction, the weight of the moving mass is transferred in the direction of its inertia. It's the momentum that acts upon the suspension (the function of g-force & CG), thus the "indication" of weight transfer (the visible body roll, which becomes less visible with a stiffer suspension, but nontheless is still occuring).

Got it! So my problem isn't with the weight transfer, not even with the body roll necessarily, except that the weight transfer due to the exaggerated body roll & dive is wreaking havoc with the front end geometry (the MacPherson strut compression & resulting loss of camber). In the end all of this is acting so as to not allow the tire to squarely contact the surface, and that's why I'm sliding up the track.


Last edited by Swift73 on Wed Jul 19, 2006 6:28 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 11, 2006 11:52 pm 
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you can make phoni's out of just about any non-charged shock. if the strut extends on it's own, it's got a charge, do NOT try drilling it.

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 Post subject:
PostPosted: Wed Jul 12, 2006 12:07 am 
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so id be fine to give it a try then.


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 Post subject:
PostPosted: Wed Jul 12, 2006 1:18 am 
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You need a chip so you can rev higher :D

There is a write up on the shock/oil change somewhere. I did it, and it works fine

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 Post subject:
PostPosted: Wed Jul 12, 2006 1:21 am 
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http://www.teamswift.net/viewtopic.php? ... t=fork+oil

http://www.teamswift.net/viewtopic.php? ... light=fork

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 Post subject:
PostPosted: Wed Jul 12, 2006 3:58 am 
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Gotta agree with the F1y on this one, get that car low, I use 175/60/13's at the track and it really improves my gearing, now I take all corners in 3rd except the hairpin, also the car sit's lower, less air flows under the car and it feels more stable going into fast corners.

As for understanding 'stiffening one end gives more grip to the other' think of it this way, if you make the rear springs stiffer then it is easier for the rear tires to slide, therefore the front has more grip relative to the rear.

As for go-kart handling, yes you can run really stiff springs but you need to make sure your shocks can continue to 'control' the suspension otherwise your tires won't stick to the tarmac and any little bump will cause the tires to slide, compression and rebound damping is a big subject, but firstly you need to get the balance of the car sorted, worry about damping later.

Try to get the +95 springs, cut them to get the ride height you are looking for, if the springs are no longer captive I would suggest machining down the shoulder of the shock, effectively shortening the shock just enough so the springs are captive.

Replace the front lower arm bushings with urethane, or at least the right hand side, you might be able to get dark blue ones and coat them in grease (so it looks stealth) that bushing can change your camber by half a degree or so because the rubber one flexs.

Make sure you are using a rear sway bar, very important!


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 Post subject:
PostPosted: Thu Jul 13, 2006 5:10 am 
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n1tr0 wrote:
you can make phoni's out of just about any non-charged shock. if the strut extends on it's own, it's got a charge, do NOT try drilling it.

I'm not suggesting that anyone should try it, but the procedure for disposing of used gas-charged dampers in the Geo manual is to drill a hole in them to relieve the pressure. They recommend eye protection. I tried it with one of mine, but most of the pressure was gone already. What's the worst that can happen anyway? Get sprayed with oil and/or metal shavings? :?

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1994 Metro - MPH project (getting a DOHC G13B)
1994 Metro - MPG project (getting an XFi G10)
1992 Swift - Parts car (gone)
1991 Swift - Parts car (gone)
1990 Swift - Parts car
1997 Metro - Parts car (gone)
1993 Metro - Parts car
1989 Swift GTi - Parts car
1998 Metro - Parts car


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 Post subject:
PostPosted: Fri Jul 14, 2006 11:37 pm 
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Simply put, you need to stiffen the rear up alot more. I ran limiting straps on my rear to control downward travel, MKII-MKIII lowering springs and monroe struts.

It did lean alot in the turns, but I can go fast thru the turns, and the faster I went the more throttle I could give it. Always on the balance of understeer/oversteer, conrolled by throttle.

I have set up my Toyota truck the same. Stiff in the rear but with a welded diff, to practice swinging the ass around.

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 Post subject:
PostPosted: Sun Jul 16, 2006 3:55 am 
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Metropwr wrote:
Simply put, you need to stiffen the rear up alot more. I ran limiting straps on my rear to control downward travel, MKII-MKIII lowering springs and monroe struts.

It did lean alot in the turns, but I can go fast thru the turns, and the faster I went the more throttle I could give it. Always on the balance of understeer/oversteer, conrolled by throttle.

I have set up my Toyota truck the same. Stiff in the rear but with a welded diff, to practice swinging the @ss around.


Do you care to share how you constructed/designed the limiting straps? Sounds interesting...


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