Anyone using stiffer anti-roll bars?

I've just noticed that Whiteline sell front and rear ARB's for my decrepid old Mk3 Only £80 each as well, pretty reasonable for about four feet of bent metal

They're about 50-60% stiffer than the stock ones I believe, and I was wondering if someone could tell me what to expect from the handling if I fitted them? Currently my suspension is completely stock - I like the comfort factor and (more importantly) the fact that I don't ground out over speedbumps and trying to get up the driveway. The car's a daily driver, I can't be arsed with slammin' it to the deck or anything. Also running on stock 16" wheels (well, J-spec 16's but they're pretty close to stock).

The main thing that bugs me with the handling is the excessive bodyroll as you load it up in a corner, there's plenty of grip there once it settles but you tend to get seasick if you have to go through a fast S-bend. It seems to me that stiffer ARB's would prevent the body roll, while still giving me good ride quality etc. But surely it can't be as simple as that can it?

Other future suspension mods I'm thinking of include Koni adjustable dampers, and possibly a full poly bushing set which is being prototyped at the moment. Would I do better putting those items on first, or is the ARB kit a good place to start?

Adam...

This is something I've thought about as TRD and Whitline do 'em for the MKIV.

As I understand it...ARB's are not wanted on the perfect chassis/suspension setup...but what they do do is make up for imperfect chassis stiffness and girlie damper/spring combinations.

but I might have that hidiously wrong.

Having said that I don't know what the trade off is for uprating your ARB's on stock suspension. Ride harshness over undulating (read crap UK) roads, with the car falling down potholes rather than flowing over them. But the benefit should be sharper handling...

IMO only worth while doing if you do it at the same time as the Poly bushes, and some tougher progressive springs.

This is my understanding of things and I'd love to know if I'm in the ball park, so please someone in the know pick my post apart!!

ARB'S:

Ride Quality: Over an undulation or full width of car ridge an ARB will not affect ride quality, but when a SINGLE wheel hits a pothole or other hole or hump affecting just one side of the car, then the added stiffness will make the ride a lot harsher. The shocks will be unable to adequately damp the added wheel rate in single wheel bump and rebound, adding to the degeneration in ride quailty.

Handling: Assuming the chassis torsional stiffness is sufficient to allow a 60% stiffer ARB(s) to work without the chassis flexing instead, they will reduce roll and GENERALLY SPEAKING reduce grip at whichever end has the stiffer rate. So a very stiff ARB on the front will GENERALLY add understeer, BUT, BIG BUT, if the original roll was reducing the tyres contact patch through poor geometry control, then the added stiffness may well INCREASE grip and REDUCE understeer by keeping a flatter tyre contact patch. Normally it's all about lateral weight transfer with ARBs, but the above is an example of when the simplistic view goes out of the window.. Almost impossible to model without a mass of data unavailable to the public for most cars, so suck it and see is the best way forward. Big heavy cars like the Supra need big bars, almost always they are solid and weigh a ton, a percentage of them adding to unsprung weight. A (more costly) hollow bar will be almost as stiff as a solid one, and hell of lot lighter. Only the outer "skin" of a round bar in torsion does much work, hence removing the middle (a tube in other words) does little to reduce its torsional resistance, but a lot to reduce its mass. On road cars a stock bar will usually effectively gain about 20% stiffness if very stiff mounts are used to replace the stock rubber ones. Never go solid, as the chassis is way too floppy and the bar will just bind up under chassi flex (cornering) with its rate going suddenly through the roof with always BAD results

HTH.

Originally posted by Chris Wilson

ARB'S:

 

The shocks will be unable to adequately damp the added wheel rate in single wheel bump and rebound, adding to the degeneration in ride quailty.

That suggests to me that I should go with the Konis first, then think about whether I want the ARBs as well. Thanks for the post Chris, very informative.

Originally posted by Adam Wootten

That suggests to me that I should go with the Konis first, then think about whether I want the ARBs as well. Thanks for the post Chris, very informative.

Konis, maybe 1.5 turns stiffer from how they come (DO NOT turn back to the stop, they come set evenly, just INCREASE from the received datum point) will add some turn in roll stiffness. See how you like it like that, then decide on uprated bars or not.

If you can get poly bushes for the stock ARB(s) try those first, they make a surprising difference. Be aware that poly bushes in other places can be very iffy and overload suspension compenets and their mountings as they put loads into them they were designed to take, as the average poly bush only has a single effective rotational movement. A twist is usually very strongly resisted, unlike the rubber ones, and this extra load is fed places it shouldn't be fed. They can be very dangerous in so far as they can cause component cracking leading to failure. You really want uniballs, that have no compliance but articulate in all planes.

"...loads into them they were NOT designed to take...", is what I meant to type... Ooops!

Would anyone be interested in poly bushes for the stock MKIV anti-roll bars?

I have found a source and will approach them for prices on Monday, if anyone is interested I will get a group price.

I think Nathan can confirm that replacement stock bushes are only available with the complete bar.