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GregTas

How to make in cabin adjustable anti roll bar?

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Hi,

I have an adjustable front anti roll bar on my car and it works well. It has three holes on the end of the arm each side. No rear bar.

The issue is I adjust it to balance the over/understeer and have it set up for the day, but some time later when I go to the track set the is not right. Was out yesterday and car had a lot of oversteer. Could be more front grip, or rear tyres worn down. Car has quite a bit of power so rear tyres tend to wear quite quickly. So I come into pits and stiffen the front bar a little, car now balanced.

Pain in the but is I can tell a lap in what I need to do, but can't do it from in the car.

So has anyone made or bought and adjustable in cabin front anti roll bar for their car?

Greg

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Sounds like you have a really good setup Greg for it to be so sensitive to adjustment, that's real pro stuff. Have never heard of anyone using a in cabin adjustable ARB in a S30, of course there are generic ones around or there were last time I checked so it sounds like it's a DIY job.

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No don't think it's that great. It always has a lot of oversteer out of corners under power, it's just when it tries to point me into the wall out of every corner it gets a bit much.

Car has about 280 kw at wheels and I'm running on 225 tyres. So application of power out of corners is a real balancing act. Predictable, but not a friendly.

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ARB's are for fine tuning of suspension - once everything else is developed.
From what you've described Greg, I suggest that in-cabin adjustable ARB's are the last thing you should be thinking about...

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2 hours ago, C.A.F. said:

ARB's are for fine tuning of suspension - once everything else is developed.
From what you've described Greg, I suggest that in-cabin adjustable ARB's are the last thing you should be thinking about...

I totally agree. With new tyres on the car it's pretty good. Just sick of adjusting ARB to compensate for rear tyre wear.

I've done 59s at my local track (Baskerville) using Nankang AR-1 tyres. In the GT class here, which is an unrestricted class. The  faster cars are doing 57s and 58s and they all run A050s. Skylines with 400+ kw and 255 tyres! So I feel my times are very respectable for my 50 year old car working with what I have. I might even have quickest time for a 240 at my track (Depending on what Shane Bond got down too).

My problem is being limited to a max rear tyre width of 225 (std guards), basically tyres are just too small. So the car will always have over steer under power, it's just trying to minimise it so it's manageable.The problem is the wear rate of the rear tyres changes the balance. This year I've done 6 race days and a few practice days and gone through 10 tyres for the year. :( Even with cheap tyres it gets expensive when you go through them. I can't afford new tyres every meet, so I need to be able to compensate for the wear.

If there's a better way to manage handling variability due to tyre wear, I'm happy for the advice. Perhaps sticky, hard wearing tyres :D

Edited by GregTas

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Going on your additional info Greg I still think that your present setup is pretty good, any improvements are only going to give you very small gains. What LSD do you have? OS Giken seem to be the best, not all LSD's are created equal.

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LSD? Old school LSD......... R180 Weldy ;D  Very predictably and definitely equal drive to both wheels :)

I was going to go R200, possibly S/N Skyline if it broke, but it has held up ok. This is where small tyres and less grip is good, because if the wheels can slip you're less likely to break something in the drive train.  

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9 hours ago, GregTas said:

LSD? Old school LSD......... R180 Weldy ;D  Very predictably and definitely equal drive to both wheels :)

I was going to go R200, possibly S/N Skyline if it broke, but it has held up ok. This is where small tyres and less grip is good, because if the wheels can slip you're less likely to break something in the drive train.  

There's at least part of your problem,  I'd bet that you would love an OSG, all plate type LSD'd proportion drive in corners for better grip and less push but the OSG does that best.

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No problem running with a CIG locker, I did for many years with no problems. I just made sure my set up took that into account.

Hopefully this post gives you a bit of a comparison and where you may head to in setting your car up.

It seems like there is an inherent balance problem with the car that needs to be resolved first before you go looking at ARB adjustment. As Lurch stated, adjusting roll bars is the last step after everything has been sorted. I would be going back to basics and looking at the simple things, spring rates, dampers, wheel alignment and even bushes being used. 

It's been a long time since I had the green monster but here was the suspension set up it had from memory:

  • Koni adjustable dampers
  • Car 240Z built to CAMS 2B rules, track only running 18"x8" wheels with full slicks.
  • Standard struts with spring perches dropped 2 inches to lower static height of car whilst retaining full spring and shock length.
  • Rates - front 450lb/inch,  rear 420lb/inch

The front arms and location were standard, but the rear was played around with a little to try to get some anti-squat and anti-dive happening. 

Bushes were a mix of nolathane and rubber front and rear to tighten up the suspension on general, but let it move where it needed.

Front bar was from memory one size up from standard, but hazy on that, and with no rear bar. 

Slicks were 240/640/18, it also ran 225/50/15 Toyo RA1's as wets or hillclimb tyres on the same set up.

In the wet on the circuit it still worked very well, but you could overpower the rear tyres pretty easy. For hill climbs, I could light up the rears for first and second if I showed no symapthy, but a dry hill climb run was pretty predictable

Power was 200rwhp and plenty of torque, 210 or so ftlb. The motor was a lazy truck motor, so didn;t rev hard, but pulled better than a 14 year old.

In a car with a proper LSD it would be very oversteery, as it was set up to try to remove the understeer inherent with a locker.

You could induce oversteer with hamfisted use of the throttle at corner exit, or if you jumped on the throttle too quick would induce understeer as the diff tried to push you straight ahead.

Once we had the damper adjustments sorted and a preferred wheel alignment, basically as much castor as we could and as much front neg. camber we mainly played with front and rear toe, and I can't remember what we ended up with, but it was checked a couple of times a year and that was it, never touched it once we had it sorted.

This picture shows the car at full suspension travel (droop on the front right, compression on the front left and just starting to apply throttle taking a very late apex for the run down the hill) at Eastern Loop at Lakeside. It was very stiff compared to most zeds when it was built.561182120_zedlakesideeasternloop.thumb.jpg.e413ce901169504ac53d9854b4276fe5.jpg

 

Edited by PZG302

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Thanks for all the information and time you've put in.

So I get the impression people feel that when rear tyres are wearing down and far more so than front,  the car should still have similar balance same as when they were new. Therefore it's something wrong with my set up. Where as I had thought worn rear tyres equals less rear grip, which is why I was getting all the oversteer when rear tyres are worn and car is much better behaved with new tyres front and rear. So perhaps my belief was wrong.

So in comparison. My car:

Car has weld steel cage and is also seam welded.

Koni adjustables. I know some don't like them, but spring rates not that high so can't see why they wouldn't work ok.

Standard struts sectioned 25mm.

Springs 2 1/2" Front springs 330 lbs, rear 280 lbs. Springs are a lot softer, but I'm on treaded tyres, not slicks and my tyres are narrower. Now Shane Bond used to run a turboed 240 at my track and does quick times. I originally owned this car with the L28 Turbo and set the suspension up in it. I asked him what springs he was running now. I was expecting in all the racing he would have made some changes, but said he had the same springs as when I sold it to him and hadn't really done anything to suspension. That car had 330 lb/280 lb when sold and so I went the same. I think it feels good. If I went harder, especially in rear I feel the rear grip would be less under power and oversteer worse, but could be wrong. Happy for people thoughts on springs.

LCA mounts moved up higher. Camber from adjustable LCA and strut tops. Camber set up via temperature (even across tyre) and wear. Would be about 3.5 deg left and 4 deg right.. Track is mainly left hand corners so left tyre runs hot on inside if camber not reduced. Also scrubs out.

Toe 0

All bushes nolathanes

Castor rods Tech Toy rose jointed adjustable. A bit more castor, but not heaps on as guards not chopped.

Front ARB .22mm. 3 holes each side. With new tyres run centre hole both sides. With more worn rear tyres, on one side of the ARB the link mount is moved forward (stiffer) one hole. So only slightly stiffer. Oversteer reduced and can get power down better and feel more similar to when rear tyres were new..

No rear ARB.

Tyres 225x45x16 AR-1 treaded, semi slick. So smaller with less grip.

My engine 373 rwhp (at 6800 rpm) and 260 ft lbs torque (at 4600 rpm) Max torque of 280 ft lbs (380 Nm) at 6800rpm. So more torque and possibly quite a bit more lower down due to turbo. 

So in comparison I feel big difference is I'm running with softer springs and more power/torque and less grip. I don't think my softer rear springs would be resulting in less grip under power, quite the opposite.

What it is has made me think about is the rear toe. I have not checked it. The rear arms are stock and so it's the one part not adjustable. I could check that and possibly see about some toe in.  Perhaps buy some adjustable arms or make some. I still feel the oversteer will increase as the rears get down, but perhaps more manageable with some rear toe in.

 

Edited by GregTas

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I still think that in your situation you need a good LSD and initially nothing else. Lockers cause rear wheel slip in corners, that's a mechanical fact and avoidable slip is not what you want.  One thing at a time, starting with a OSG. 

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On 12/15/2019 at 1:49 PM, GregTas said:

My problem is being limited to a max rear tyre width of 225 (std guards), basically tyres are just too small.

It's all relative, I have to run 195/60/14 tyres ;)

On 12/15/2019 at 1:49 PM, GregTas said:

If there's a better way to manage handling variability due to tyre wear, I'm happy for the advice. Perhaps sticky, hard wearing tyres :D

Try running Yokie A050 it's level of grip last very well and very consistent right down to bald.

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4 hours ago, 260DET said:

I still think that in your situation you need a good LSD and initially nothing else. Lockers cause rear wheel slip in corners, that's a mechanical fact and avoidable slip is not what you want.  One thing at a time, starting with a OSG. 

When I put the CIG in the only difference I felt was a slight understeer with turn in on low speed corners, as expected. If I had LSD then with power on out of the corner when LSD  should be locking wheels I wouldn't think it would reduce oversteer. If I went LSD then I wouldn't spend it on R180. I would do on R200 S/N. More options with S/N but quite a bit of work to get one in. So consideration to change over when if/ diff breaks. 

 

15 minutes ago, hmd said:

It's all relative, I have to run 195/60/14 tyres ;)

Try running Yokie A050 it's level of grip last very well and very consistent right down to bald.

Yes all relative . I could turn the boost down too ;D

On those tyres I had been thinking about something with more consistent grip. I wouldn't mind the Yokie but prices was about $700 per tyre  and though could get very expensive if still going through them. I will have  a think about tyres. Getting good time when newish but just wearing too quick and variable grip a s they do.

 

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2 hours ago, GregTas said:

 I wouldn't mind the Yokie but prices was about $700 per tyre  

 

Are you sure about that price? 195/60/14 is about $285 per tyre and 225/45/17 is about $470 per tyre.

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2 hours ago, hmd said:

Are you sure about that price? 195/60/14 is about $285 per tyre and 225/45/17 is about $470 per tyre.

No not sure on that price. Found price online at $695. So probably high.  I did notice my size in 16s was more expensive than 17s. I dropped into tyre shop today and they're getting a  price for me.

If I buy two more wheels I will have eight, so then I can have two set of tyres, Cheapies for testing and goods for race days. :) 

Edited by GregTas

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I get all my tyres from the UK (www.demon-tweeks.com)

Dunlop DZ03G H1 compound track tyre 225/45/17 delivered to your door is $390 each

Toyo R888R track tyre 225/45/17 delivered to your door $285 each

 

They dont list yoko A050, but can probably get them for you if requested

I find it interesting and sad that the UK can supply tyres cheaper than Australia including postage

Edited by lampy

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On 12/17/2019 at 1:37 PM, GregTas said:

If I buy two more wheels I will have eight, so then I can have two set of tyres, Cheapies for testing and goods for race days. :) 

Be careful with that, it can bite you on the arse badly.

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22 hours ago, PZG302 said:

Be careful with that, it can bite you on the arse badly.

How so? Obviously need best tyres on for suspension set up, but if sorting out other things like engine tune I see no point wearing out good tyres.

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As you said above, yes the good tyres for suspension set up, but also important for other factors as well.

Depending on levels of grip between them, you can mask other deficiencies using the cheapies that all of a sudden show up when you bolt the good tyres on and go fast for the first time. A car that was predictable as it got the edge of grip and slid nicely, may on stickier tyres hold and hold and then just snap you around.

Generally on cars as agricultural as a Zed, it probably won't be an issue, but it may be. Especially if your cheap tyres are a few seconds off the pace of the good tyres. The extra pace comes from the extra grip for higher and more sustained cornering speeds.

An exaggerated case of this, and only used here for demonstration, was the final year of the old series production and first year of Group C racing where proper race tyres (slicks) were used plus the introduction of the Falcon Coupes. The engines started to destroy themselves due to oil surge caused by the extra grip of the stickier and much wider tyres run between the old XY sedan and the new XA coupe.

Personally I also had similar issues for a while when I went from Street sedans to the old version of IPRA in a 180BSSS. The old tyres were dunlop Ducaros, a reasonable street tyre of the day and overnight I went to Bridgestone RE005 semi slicks, cue oil problems and an excuse to get a 2.2 litre L18 put in the hole..... 

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