After Market Sway Bars?

[djr81]

Fit the harder sway bars. For my ten cents worth it makes the car much nicer to drive if there is a good balance between stiffness in terms of spring rates & stiffness in terms of anti roll.

[Beer Baron]

i say try them and see what you think. it wont cost you anything if you have to switch back.

i ran the following config:

bilstein coil-overs (eibach springs) (all factory allignment parts)

bilstein coil-overs with adjustable castor rods, and upper control arms

bilstein coil-overs with the above AND whiteline bars front and rear (rear on hard, front on medium or soft - I forget which).

at each step the on track handling improved. I didn't notice much from the upper control arms. I did notice a lot from the castor, I also noticed improvement from some toe out at the front, and noticed improvement with the bars.

I'm now about to switch it Nismo/Ohlins coil-overs with seperate bump and rebound adjustment. They have much higher spring rates than my old stuff, (10Kfront. 8K rear). I will try them with the whiteline bars, and if no good will try with the stock bars I kept. If still no good I will try some lighter springs (the only option of those that will cost me $$).

I'm thinking the nismo/ohlins stuff will work well with the stock bars, but maybe no so well with the uprated WL bars. but the bilstein eibach combo was very good with the WL bars.

[Roy]

Grip, handling etc are not all related, s djr81 points out. And its a good thing to remember.

But i dont think my thing can be hurting for grip. In a short event that only went for 18 seconds and was a launch a few bends/turns i came 14th out of 90 odd cars. Every car that beat me was 4wd so the 6/10 i was off 1st could very well have been the launch as i still had the std box and open wheeling diff.

So my car has to have a fair bit of grip to keep up with AWD cars on semis, many with cages, lightened and more power if i could get so close through a 90deg right hander then a 180degree left hander that is flat in 2nd up into 3rd over a crest thru a 2nd gear slalom then back up to 3rd before the garage.

Mind you 6/10 on such a short event is daylight

[nuffsaid]

And if it is a purely street driven car? still worth a try?

[Roy]

I think so.

[salad]

As for transient (ie damper) issues - these are different from steady state spring (& rollbar) issues. But you mate is right - low speed bump does have an effect, particularly on turn in.

yeah, he did say later it more suited his driving style of being able to just yank the wheel and have the car (s15 GT-P race carturn. and then mentioned that he did get a little mid corner understeer, but was then able to get on the throttle earlier and have a faster corner exit compared with using swaybars.

i would think that if using a high low speed bump and a relatively low high speed bump (for compliance) cornering performance would get worse and worse through the corner, so corner exit wouldnt be too good, but he says he was able to get on the throttle much earlier with a lighter bar and stiffer valving

is this right? it doesnt sound right to me

and beerbaron: what spring rates did your bilsteins have? and what size whiteline bars?

Edited October 31, 2006 by salad

[Beer Baron]

the springs in the bilsteins were relatively light (well compared to my ohlins). not sure on the exact rate though. the whiteline bars, i cant remember the size, but they are they heavy duty adjustable bars for 32 GTR.

[djr81]

The only problem with the Whiteline bars is that they are a solid bar. Which is a pretty stupid way of building sway bars, but there isn't much choice out there.

[Sydneykid]

Time for me to weigh into this discussion.

In Production Car racing we are not allowed to change the stabiliser bars. So we use the shocks to limit the roll. It would be better to use larger stabiliser bars, but we can’t, so we do what we legally can.

We could limit the roll with high spring rates (like the Japs do) but then the springs would be too stiff to absorb the bumps. So we use spring to do their REAL job, that being to hold the car up and absorb the bumps. This is why excessive low frequency bump valving is the chosen band aid. But it is still a BAND AID, it would be technically superior if we could upgrade the anti roll and leave the shocks to do their REAL job. Dampening the spring and chassis oscillations

It is overly simplistic to suggest that stabiliser bars reduce grip. In fact it’s 100% rubbish when you look at both ends of the car at the same time. Let’s use the GTR example, they understeer in mid corner because they transfer excessive weight (which they have lots of) onto the outside front tyre. If I use a largish rear stabiliser bar I lessen the amount of weight transfer onto that outside front tyre. The reduced roll means the inside front tyre has more weight on it, hence more traction and therefore less understeer. The larger rear stabiliser bar has not REDUCED the rear grip, it has INCREASED the front grip.

Sure you can go too far with stabiliser bars and reduce the grip at that end. But if you are increasing the grip at the other end by more, then the total grip is increased. Hence you get higher cornering speeds. Which is what improving handling is all about.

Almost all race cars, even up to F1 level, use driver adjustable stabiliser bars. Why? Because they are the most effective method of changing the handling balance.

Stabiliser bars are the best bang for buck suspension upgrade you can make for improved handling. Road or track. That’s a fact.

cheers

[djr81]

Time for me to weigh into this discussion.

In Production Car racing we are not allowed to change the stabiliser bars. So we use the shocks to limit the roll. It would be better to use larger stabiliser bars, but we can’t, so we do what we legally can.

We could limit the roll with high spring rates (like the Japs do) but then the springs would be too stiff to absorb the bumps. So we use spring to do their REAL job, that being to hold the car up and absorb the bumps. This is why excessive low frequency bump valving is the chosen band aid. But it is still a BAND AID, it would be technically superior if we could upgrade the anti roll and leave the shocks to do their REAL job. Dampening the spring and chassis oscillations

It is overly simplistic to suggest that stabiliser bars reduce grip. In fact it’s 100% rubbish when you look at both ends of the car at the same time. Let’s use the GTR example, they understeer in mid corner because they transfer excessive weight (which they have lots of) onto the outside front tyre. If I use a largish rear stabiliser bar I lessen the amount of weight transfer onto that outside front tyre. The reduced roll means the inside front tyre has more weight on it, hence more traction and therefore less understeer. The larger rear stabiliser bar has not REDUCED the rear grip, it has INCREASED the front grip.

Sure you can go too far with stabiliser bars and reduce the grip at that end. But if you are increasing the grip at the other end by more, then the total grip is increased. Hence you get higher cornering speeds. Which is what improving handling is all about.

Almost all race cars, even up to F1 level, use driver adjustable stabiliser bars. Why? Because they are the most effective method of changing the handling balance.

Stabiliser bars are the best bang for buck suspension upgrade you can make for improved handling. Road or track. That’s a fact.

cheers

In an ideal world you would be able to separate your damping resistance in roll from that in bump & compression. Unfortunately the list of active suspension options for the GT-R are rather limited at zero. Maybe Frank Williams to help out. You sort of have to start looking at anti roll bars as undamped springs to a degree as they don't come with their own dampers & rely on the coil spring dampers.

SK, your are correct in saying that when looked at in conjunction with one another the effects of anti roll bars can be counter to that when looked at in a single axle situation. Unfortunately explaining it to people is difficult because one effect is opposite to the other & the importance of them changes depending on the chassis under discussion & the tyre & the suspension geometry & a million other things.

I remember Tyrrell using the ultimate anti roll arrangement. One spring & dmper unit for the front end. Don't have to muck about with sway bars then....

[hrd-hr30]

race cars use in-car adjustable bars to trim the car during long stints with changing fuel loads and tyre condition. its the most simple way to change balance quickly within the car, not necessarily the best way to setup the balance of the car!

conventional race car setup is to use springs primarily to control the car's behaviour. sway bars then used to fine tune the balance. shocks affect mainly transitional state handling - ie initial braking, turn in or change of direction, and transition to applying power out of the corner, by mid corner, you are relying on springs and bar to provide the handling balance.

this whole soft spring hard bar setup approach comes from categories trying to maximise the effect of their aerodynamic freedoms, and requires quite sophisticated shock tuning and dynamic control of roll centres. I think its a bit of a mistake trying to apply it to a car with no real aero to speak of, and production cars where dynamic roll centre geometry is likely to be far from ideal.

[Roy]

LOL...you are all making this all far too hard!

Mass produced chassis that flexes like one of those chest expansion machines on late night tv when you jack your car, let alone hammer through corners. So getting techincal about undamped springs etc. Hell most ppl dont even have the cars corner weighed, and when they do they normally forget to install the 90kg nut behind the wheel during the exercise.

My thoughts, and its one of the few things i think is pretty clear...

For a road car, weekend play car, swaybars were the best money i ever spent on my car. There is not a downside!

With my car still rolling around too much for my liking...i went to a bigger set of bars again and on the surface of it, again seems to be fine despite my springs and shocks are pretty wimpy off the shelf items.

For the dollars it cant be too bad. The old thing actually won its class at several events and placed top 20 overall in a few events at the Dutton...though the Dutton Rally is hardly a serious rally event, there are cars that i had no right in beating. I beat every single M3 at Winton and Sandown, won my class at Winton and came 2nd at Sandown, (Behind a2JZ Celica with iver dble my power) Again, i got nothing under the bonnet compared to these cars, so while the suspension is a long way from ideal it mus tbe working ok

[Roy]

oops

[djr81]

race cars use in-car adjustable bars to trim the car during long stints with changing fuel loads and tyre condition. its the most simple way to change balance quickly within the car, not necessarily the best way to setup the balance of the car!

conventional race car setup is to use springs primarily to control the car's behaviour. sway bars then used to fine tune the balance. shocks affect mainly transitional state handling - ie initial braking, turn in or change of direction, and transition to applying power out of the corner, by mid corner, you are relying on springs and bar to provide the handling balance.

this whole soft spring hard bar setup approach comes from categories trying to maximise the effect of their aerodynamic freedoms, and requires quite sophisticated shock tuning and dynamic control of roll centres. I think its a bit of a mistake trying to apply it to a car with no real aero to speak of, and production cars where dynamic roll centre geometry is likely to be far from ideal.

The soft springs hard sway bars also helps (along with some damper settings) in those kerb hopping moments, relative to a stiffer spring/softer sway bar.

For my 10 cents I found that stiffer sway bars were a good improvement, but nowhere near as good as new dampers.

[Roy]

I found the 3k i saved by not buying new springs and dampers really handy when i was at the strippers. Nothing worse then running out of tipping dollars

[Beer Baron]

yes, all that technical stuff aside. I agree. bang for buck sway bars are a good upgrade, even just purely as a learning excercise.

[djr81]

What about the strippers as a learning exercise. Or is that a yearning exercise.

The thing to remember (As far as sweeping generalisations go) is that balance is as important as total cornering grip.

By the way, does anyone have a torsional rigidity number for the R32 R?

[Roy]

Yeh, flacid

[hrd-hr30]

fair enough. swaybars are a good upgrade for a road car. I was responding more to the suggestion that springs are only there to hold a car up! I think its become a more interesting topic than "should I get swaybars?". besides, he's got some opinions on that question already.

The soft springs hard sway bars also helps (along with some damper settings) in those kerb hopping moments, relative to a stiffer spring/softer sway bar.

that's arguable! a swaybar links both sides of the car and applies equal and opposite forces at both ends, if you hit a curb hard while cornering and the inside wheel moves up, you get a change of spring force at the other end - ie the outside wheel will temporarily see a softer spring rate, and that corner could also dip lower too depending on spring and shock setup. this will change the balance of the car mid corner and could very well unsettle it. the more you are relying on bar in your setup, the larger the effect it will have.

Edited October 31, 2006 by hrd-hr30

[djr81]

Think about it in a transient rather than steady state mode.

Then factor in your high speed damping effects.