Rear Sway Bar or Rear Strut Bar?

[Genesis®]

hey guys,

i just fitted a front strut bar in my R32 and i noticed that it stays firm and flat whenever i do a hard corner.. however i also feel the back of my car twisting... as if one of the wheels is lifting off the ground. Should i get a rear sway bar or rear strut bar to solve this problem??

my R32 already comes with a factory-fitted rear sway bar and currently has the suspensions. The suspensions mod will be in the future but now, really wanna solve the rear problems first.

thanks in advance,

glenn

[JimX]

I would change the same thing you changed up front - ie the strut bar. If the rear feels like it's lifting off then it will only get worse if you put a stiffer sway bar on the rear. Once you upgrade the front swaybar though you should be able to more easily upgrade the rear.

[Sydneykid]

Hi Genesis., the front strut brace on an R32 attaches to the top of the shock tower which are close to the locating points of the front upper control arms. Therefore it works very well at limiting the flex. This maintains the wheel angles (camber) in relation to the chassis. It does not limit the roll.

On the other hand the rear strut brace does not locate close to the upper control arms as they are bolted to the suspension sub frame. Unlike the front shock towers, the rear tower do no locate the upper control arm inner pivot points. I strongly suggest you take a look and you will see why a rear strut brace will never be as effective as a front one on a Skyline.

A stabiliser bar, or more correctly an anti roll bar, limits the roll of the chassis in relation to the wheels. This is a totally different purpose to a strut brace.

It is not unusual to get a sensation of less roll when a strut brace is fitted, but that is more a function of the wheels staying more upright rather than less chassis roll.

The first thing I do to the rear suspension is to fit a set of "pineapples" to the rear sub frame. This limits the amount of movement of the subframe in relation to the chassis. Sort of like the strut brace does on the front.

Have a look here....

www.whiteline.com.au

they have the parts that you need.

Hope that helps

Happy New year to all

[Genesis®]

thks guys. i guess i will have to do my research on this issue then. i agree with what Sydneykid said about the rear bar becos that's the same piece of advice most of my mates gave. i will most probably proceed with getting a rear bar and see how the car behaves in corner. if the improvement is insignificant, i will consider a stiffer sway bar.

btw Sydneykid, you turbocharged your car? what sorta engine is it in a R32?

thks again

glenn

[Sydneykid]

Hi GenesisR32, we have a circuit race R32 GTST that is just about to get an RB31DET in it (RB30 forged bottom end and fully worked RB26 top end). The 170,000 k's old RB20DET has done the job for the last 2 seasons and we have sorted the brakes and handling out reasonably well. So now it is time to double the horsepower.

The first RB30DET we did had a standard RB30E bottom end and a standard RB25DE top end, with a RB20DET exhaust manifold and a GCG ball bearing hi flowed RB25DET turbo. It worked a charm and the guy who owns it now, loves it.

Really, I wouldn't bother with a rear strut brace on an R32 until you have done the other things. The difference it makes is very very small. Compared to the front brace which makes a noticeable difference.

Hope that helps some more.

[Genesis®]

is it street legal and just done up for circuit?

sounds like you did alot of track work yourself and definitely in a position to know much more about car handling...

i will balance the pros and cons... problem is.. its hard to find a rear bar for a r32

thks again Sydneykid

[Nismodified]

japanesemotorsport have quite a few R32 rear struts.

[BIGBLOCKR31COUPE]

forget the rear strut bar. If you want less body roll you should spend your money on your anti-roll bars. On a road car a rear strut bar is more of a wank than anything. If the rest of your suspension is not sorted first it it a waste of money.

[JimX]

I'm just wondering - if the rear strut bar is so useless then why do the series 2 R33's come with them?

[Sydneykid]

Hi JimX, I was advising GenesisR32 on the best bang for his buck on an R32. Basically this comes down to my experience, which has been that a rear strut brace on an R32 is not good value until you have done the other things first.

As for whether or not they are useless on an R33, I can only suggest you jack the rear of your car up and take a look at where the top inner control arm mounts are located. Then take a look at where the strut brace is mounted. That should answer your question.

If you want to know why the front strut brace is so important, then do the same at the front. The difference is obvious. While you are looking, you may also notice that the front of a Skyline is not joined together by a roof and a parcel shelf support structure like the rear is.

Hope that clarifies my previous post.

Moving on to Genesis R32's questions;

"is it street legal and just done up for circuit?"

^It's a circuit race car, although I will have a crack at a 1/4 sometime this year as I want it to be in HPI radial tyre challenge.

"sounds like you did alot of track work yourself and definitely in a position to know much more about car handling..."

^ I manage a couple of circuit race teams, run suspension diagnostic and driver training courses, design aftermarket suspension components, write the odd article for the magazines on suspension, do race car data logging and analysis and still race a bit myself. So I guess you could say I know my way around a circuit race car.

"i will balance the pros and cons... problem is.. its hard to find a rear bar for a r32"

^ I buy my bars from

www.whiteline.com.au

they have lots of good stuff for Skylines

Hope that helps

[Genesis®]

thks alot Sydneykid, you're a real champion.

Have a Happy New Year.

glenn

[Roy]

the front strut brace on an R32 attaches to the top of the shock tower which are close to the locating points of the front upper control arms. Therefore it works very well at limiting the flex. This maintains the wheel angles (camber) in relation to the chassis

Good little case study!

I have been meaning to get some front camber wound out of the front of my car for a while now, as its eating the inside of the front tyres, and didnt show any real benefit on the track...if anything it seemed to lack sharpness on turn in, so was a step in the wrong direction (not enough contact patch on the raod when combined with all the castor im running???)

Now, since i am still working on turbo setup and other engine bay shinanigans, i havent bothered putting my front strut bar back on, since getting new tyres and bolting on a turbo setup as i havent been doing any track work.

Now i have been keeping a careful eye on front tyre wear, and the new tyres have survived 200% better without the brace, then the last set did with the strut brace fitted.

Now the tyre compound/brands are abviously different, but how much that has impacted on the difference in wear im not sure. So before when the tyre would be thru to belts within 5-6,000kms, they are wearing almost perfectly with only a hint of additional inside wear, after about 9,000kms with what looks to be plenty of meat left.

I also noticed that without the strut brace fitted trying to open and close the drivers door when the car is jacked up isnt a great idea. The more i learn about this the more i realise why racecars go to the trouble of having %#kgs worth of cage not only as a safety initiative, but also as a chassis/suspension tuning aid.

[Sydneykid]

Hi Roy, I agree, you can have too much camber. Let me try a quick analysis of your example.....

^At the end of a straight you have just used the brakes a lot

^The front of the car is compressed

^So it has more than its static negative camber

^The inside of the tyres is thus doing all the work to slow the car down

^ The narrow amount of tread in contact with the track is overheated

^You then turn the steering wheel and, via the positive caster setting, introduce more negative camber

^This means the already hot and mushy part of the tyre is trying to turn the car as well

^Hence reluctance to turn in

Tyre wear is an altogether different issue, by not having the front strut brace, the chassis is twisting and eliminating some of your static negative camber. Hence not wearing the inside of the tyre as much.

But your example seems a bit extreme, perhaps you have excessive toe out, that really exacerbates the wear on the inside of the tyre.

Hope that helps

[Craved]

if roy had excessive toe out, wouldn't that help with the turn in and over ride the excess camber and lack of benefit on the track?

[JimX]

My car has had both excessive toe in and toe out on the front at various stages of its alignment life. The only differences I found are vague steering and sometimes a shudder under brakes. There was no improvement to handling at all.

Admittedly it was out by a couple of mm, but I can't imagine it going through a "sweet spot" of superior handling somewhere between 0 and 3mm.

Toe in on the rear I've heard can help, but I don't think it will help on the front.

[Roy]

Tyre wear is an altogether different issue, by not having the front strut brace, the chassis is twisting and eliminating some of your static negative camber. Hence not wearing the inside of the tyre as much.

Thats why i thought it was interesting that the chassis actually dulled suspension tuning by so much. Does the age of the chassis/body have much impact?

But your example seems a bit extreme, perhaps you have excessive toe out, that really exacerbates the wear on the inside of the tyre.

As per Whitelines setup when i had the kit made for my car i was running

Front

Camber , -1.5

Castor , - 6(L) & 5.5®

Toe , 0

Rear

Camber , -1.25

Toe , 0.5mm

With the swaybars fitted and adjusted to the softest settings i found the car most to my liking and had nice turn in, no tendency to under or oversteer. It was great to drive... only thing is that it lacked outtright traction.

So on go Dunlop D01Js, and after a day bashing around Eastern Creek i blistered the outside of the front right tyre

So got another wheel alignment, left everything the same except front camber which was upped -2.5. The car now had a bit of a front end push and now couldnt feather the loud pedal and balance the car mid corner (im not saying my driving technique is perfect...) if i did it understeered, nothing drastic just didnt point as nicely.

So now in hindsight, perhaps i should have perhaps left the susp geometry alone and tried to reduce the weight transfer to the tyre shoulder by tightening up the front swaybar, would this have had enough of an effect to stop the outside of the tyre from blistering.

And a strrange thing about the tyre blistering, the thing was pointing, turning and gripping like an arrow, and was comfortably on the speed limiter thru turn 1 at Eastern Creek! I would have thought the handling would have hinted at was was to come???

[KamikazeR33]

I'm just wondering - if the rear strut bar is so useless then why do the series 2 R33's come with them?

i havent seen one on mine, or am i looking in the wrong place JimX?

[JimX]

There's a factory rear strut brace on some R33's. I thought it was a series 2 thing, but it must be an option or something.

[predator]

Thats why i thought it was interesting that the chassis actually dulled suspension tuning by so much. Does the age of the chassis/body have much impact?

Note also: skylines also have a dirty big bar underneath the dash, which basically strengthens the chasis between the a-pillars and provides crash protection. A front strut brace combined with this provides an effective parallel brace in the space of less than a meter, which makes the front of the car super stiff, e.g.

------------

|..............|

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I'd say that is where the "real" effectiveness comes from a front strut.

To do the same in the rear you'd have to invest in a lot more than a simple rear bar, seeing as the parcel shelf is so flimsy (compartively). Something like a full cage or similar arrangement across where the backseats are (sans back seats) would provide a pretty rock solid rear as well i'd say.

[Sydneykid]

Hi Roy, I'm sorry but I don't have any explanation as to why the balance would go to understeer when you increased the front neg camber from 1.5 to 2.5 degrees. However I am not at all surprised that you blistered the outside of the front tyre when running 1.5 degrees neg.

I can give you a whole pile of "maybe's" but nothing definitive.

What I can say is if it happens again, I would increase the rear anti roll and try that. That will decrease the diagonal weight shift, which is more than likely the reason why it understeers. If you have too much dynamic weight going onto the outside front tyre, it causes it to scrub and pass its slip angle.

Conversely you can decrease the front anti roll, which will increase the diagonal weight shift and therefore push the tyre down onto the track harder. This works if the understeer is caused by insufficient weight on the outside front tyre.

So you can have two reasons for the understeer, too much dynamic weight or too little dynamic weight.

These are of course supplementary to the main reason which is insufficient tyre contact patch ie; not enough or too much dynamic camber. Which we covered last post.

Hope that helps.