Turbo anti roll bar dangerous on track?

[Chown]

Hi all,

I've track day'd my Mk1 for a couple of years now and this weekend i fitted a mk2 Turbo rear anti roll bar as I'd read it was a big improvement.

I tested it on the road and yes i got the sharper turn in and no understeer but on the track this turned into being down right dangerous! Power-on oversteer, trailing throttle over steer, bump induced oversteer. The only way to stop the thing oversteering was to slow down and stay below the grip level.

It seems to me that the whole balance of the car has been destroyed which was one of things i most enjoy about these cars

The car is no race machine admittedly but it runs KYB Excel G's, sports springs, R888's etc etc and was an extremely predictable and capable track day before today!

Anybody any thoughts?

[kherseth]

Just some thoughts, i have no experience myself.

You say you have been driving on trackdays for year, could it be just something to get used to?

Adjustable dampers? If so that would of course require readjustment.

[Lauren]

What's your geo settings for toe front and rear?

You can temper the oversteer a bit with more toe-in.

[cartledge_uk]

Sounds just right to me

As Lauren says, you will need to adjust geometry, and get it set up square.

[elbon50]

Fitted a Whiteline rear ARB recently Chown

Have used it in sprint competitions first on the soft setting then the harder one

Nothing negative to report. All good

Understand that the turbo bar does much the same job

Wonder if combination of stiffer bar & the 888s doesn't agree ?

Peter

[Chown]

Thanks for replies all,

I've had my struts slotted and run about 2.5deg camber and zero toe in on the front and about 2deg and only a touch of toe in on the back. The car does sit fairly low and does have a fair amount of stiffness already but it was fine like this beforehand

I like oversteer as much as anyone and I'd read so much good about the turbo arb but surely not at the expense of predictablility and chuckability.

The car is normally pretty fantastic, I like braking deep and modulating the throttle to kill the small understeer and point it where i wanted. The car always attracts people wanting to know whats special about it but its just that it was so telepathic!

I think if i introduced a bit more stiffness to the front it might tip the balance. Is there a suitable uprated front arb?

Does everyone feel confident that they can lift gently with this arb without introducing bucket fulls of opposite lock?

Thanks again

[Lauren]

Increasing the toe in at the back to something like (IIRC it's been years) 3.2mm which I think is the TRD setting, really ought to help make the back end feel more planted.

So, I'd say put a bit more toe in on the rear.

Parallel toe at the front should be fine but obviously will make the car feel pointy (which I like to be fair) and help the achilles heel of a MK1, turn in.

[PW@Woodsport]

Honestly never heard of anyone having any negative handling effects with the turbo ARB before, and there's a lot of cars out there being tracked with them fitted.

[Chown]

Maybe I'm becoming a wuss then!

I've ordered an adjustable Whiteline front ARB so hopefully i can balance the 2 together

I was at an airfield track called Keevil and the one corner in particular was off camber in the second half and changed surfaces. Everyone was suffering with understeer. I think my car is just way too stiff on the rear. But then on all the other corners it felt nervous and twitchy.

Thanks for all your replies

RIP Simoncelli

[PW@Woodsport]

No, what i would say is that there are far too many variables involved to be able to pin it solely on the turbo ARB, but if you can switch bars on the same day, same conditions/tyres etc i'd be interested in your comparisons.

[Chown]

Yeah i'll try that next weekend. It was so bad that the only solution was to disconnect it and run the day no ARB at all, hello body roll and understeer!

There's only one other thing i can't quantify at the mo. I loaned my car to a mate for 3 weeks for the inevitable welding for the MOT. When i had it back the front tracking was slightly out. I couldn't see any kerb marks but i obviously had it set straight before the track day. I know its unlikely but maybe the rear got a nudge too. Surely that'd only affect corning in one direction tho.

Plenty to try!

Thanks

[PW@Woodsport]

Based on that new info i'd definately have your geometry checked before changing the ARB, i've run a turbo ARB on Mk1's for many years and never had any handling issues.

[LimeyMk1]

Surely with all the suspension mods (hard shocks, springs and stiff ARB) all your suspension movement in the rear has almost been eliminated, which is going to make the car very sensitive to surface variability?

[Chown]

I'm booking the car in today to have its geo checked. The toe in should be set at the TRD settings so we will see!

Thats part of my question tho, is my car now so stiff on the rear that it has become too sensitive. Do any of you run cars this stiff on the track or have i gone too far? I'm hoping with the whiteline ARB on the front i can have the neutral balance back and the extra grip afforded by the lack of body roll.

Geo first as suggested tho

[cartledge_uk]

I'm booking the car in today to have its geo checked. The toe in should be set at the TRD settings so we will see!

Thats part of my question tho, is my car now so stiff on the rear that it has become too sensitive. Do any of you run cars this stiff on the track or have i gone too far? I'm hoping with the whiteline ARB on the front i can have the neutral balance back and the extra grip afforded by the lack of body roll.

Geo first as suggested tho

yes, I ran my race car stiffer (with whiteline ARBs) and it handled like a bag of crap until the geo was set.

[HighwayStar]

Why not just remove it and refit the original?

R

[Chown]

Hi all,

Just had garage check geo:

Front: Zero toe in, 2deg negative camber (rounded to nearest 0.5)

Rear: 2mm toe in total, 3deg negative camber (rounded to nearest 0.5)

I've left the fronts alone and had the rear set to the following:

3.5mm toe in, 1.5deg negative camber

I'm guessing that the original aggressive rear set up (was more like guess work when i first made my camber gauge!) was just fine with the less stiff rear ARB. ie extra camber worked with more body roll and the only slight toe in made the rear active enough to kill any supposed understeer.

Hopefully the more realistic set up will suit the turbo ARB! I've just received my Whiteline front ARB too

Any thoughts anyone?

Thanks

[Lauren]

Sounds alright, give it a go, let us all know how you get on.

[Chown]

Hi all,

I know its not good practice to have 2 change at once but new "safer" geo and new whiteline ARB at max stiffness fitted today.

Not possible to test car properly yet but its certainly a lot more balanced. It still has a decent turn in and you are no longer scared of lifting gently for fear of huge opposite lock!

Hoping it will be a lot more composed on the track

Thanks for everybody's input

Chown