What Is The Deal With The Ultra-stiff Anti Roll Bars?

[Guest Pär Hansson]

It seems to be a dogma on this forum that a stiff rear ARB is the way to go, even along with stock torsion bars.

 

I don't argue this statement, but I wonder...

 

Since we all lift the inner rear wheel at least mid turn, all added roll bar stiffness adds unsprung weight to the outer, loaded, wheel.

 

A 30 mm ARB is, in comparison, almost infinately stiff to a 23 mm TB. Therefore it tries to replicate the outer wheel movements to the air-borne inner wheel and, hence, almost double the unsprung weight of the load bearing rear wheel. We're mostly saved by the inner dampers, though.

 

Then considering the wheel rates in the rear suspension (Rod diameter vs wheel spring rate):

 

 

...I believe that you should first double the wheel rate at the front (installed rate x 0.90-0.95) and then adjust balance of the car by means of ARB:s, tyre pressures and so on.

 

I've chosen 25 mm both ARB and TB rear along with 550 lb/in wheel rate and stock GTI16 ARB in the front. That is a slightly soft front suspension in comparison to the rear which sholld render a slight over-steer.

 

I also have 20 and 17 mm ARB:s to install as well as a complete stock 309 GTI rear assembly in case of wet conditions along with 300 lb/in front springs and the option to disconnect the front ARB.

 

I don't say, but I believe that you should push the boundaries a bit and go for a far stiffer springing in front (where it's also relatively cheap) to reduce roll and maybe let go of the ideas of ultra-stiff rear ARB:s?

Edited October 31, 2008 by Pär Hansson

[Baz 421]

It depends what you're doing no?

 

The idea with stiffer rear ARB's, well the main benefit is the added turn-in, it dials out a little understeer, if making it a little less stable whilst cornering at speed. As far is i can work out & understand anyway.

[Guest Pär Hansson]

It depends what you're doing no?

 

The idea with stiffer rear ARB's, well the main benefit is the added turn-in, it dials out a little understeer, if making it a little less stable whilst cornering at speed. As far is i can work out & understand anyway.

You can achieve the same with front roll stiffness adjustments as long as you lift the inner wheel more than a hair thick.

 

I did not mention this, but turn in and track out behaviours are also determined by the dampers. But let us concentrate on the sprng related balance.

[taylorspug 7]

Are you talking about track or road cars here? As the two differ wildly in both setup and money people spend (or are willing to spend).

 

Firstly not everyone wants to go ultra stiff spring-wise, especially for UK backroads which are massively bumpy. As this forum is mainly UK based that is probably why you dont see people running big rate springs and bars, along with the cost. The stiffer rear ARBs are a cheap basic upgrade that work extremely well in dialling out understeer. In all honesty i was expecting the 24mm one to make my car choppy over bumpy roads, but ive not had a single ill-effect so far, in fact its the most dramatic and beneficial handling change my car has had.

 

Im personally not even running a front ARB now, as i found the car behaved alot better with it disconnected. It also has had very little if any effect on roll, leading me to believe that even with the 175lb springs ive been running up until now its not really been doing alot!

[Sandy 191]

I'm not a fan of upgrading the rear ARB, I feel it takes the feel out of the chassis and makes the transition into oversteer harder to modulate compared to getting the spring rates right and/or widening the front but keeping the rear width standard. I don't run front ARBs on my Peugeots at all now. There's a slight reduction on the apparent turn on response, but the mid corner balance and traction is much better.

[taylorspug 7]

I'm not a fan of upgrading the rear ARB, I feel it takes the feel out of the chassis and makes the transition into oversteer harder to modulate compared to getting the spring rates right and/or widening the front but keeping the rear width standard. I don't run front ARBs on my Peugeots at all now. There's a slight reduction on the apparent turn on response, but the mid corner balance and traction is much better.

 

Exactly the same thing i found regarding the front ARB, the car settles much nicer mid corner.

 

My main point with the rear ARB is that for the money it is a very effective upgrade. It may not be perfect, but not everyone has the time and money to devote to make things perfect to the n'th degree. Also on my car i didnt particularly notice a lack of feel, although at the end of the day every setup is different.

Edited November 1, 2008 by taylorspug

[Cameron 16]

I think the general consensus with stiffer ARBs is that it's cheap and easy to do, fulfilling the two main criteria for most 205 owners.

 

You're right though, an ARB works by reducing load on the inside wheel - effectively reducing grip so all they should be used for is balancing the chassis. Since 205s are front wheel drive and nose heavy it tends to be the front that will let go first, so a stiffer rear ARB will balance that out by reducing rear end grip. Which is exactly the problem, you shouldn't be reducing grip to balance a chassis, you should be seeking to increase it. But that's too much work and too much expense for your average 205 owner so f*** it, just whack a stiffer bar in.

[AdamP 0]

I think the general consensus with stiffer ARBs is that it's cheap and easy to do, fulfilling the two main criteria for most 205 owners.

 

You're right though, an ARB works by reducing load on the inside wheel - effectively reducing grip so all they should be used for is balancing the chassis. Since 205s are front wheel drive and nose heavy it tends to be the front that will let go first, so a stiffer rear ARB will balance that out by reducing rear end grip. Which is exactly the problem, you shouldn't be reducing grip to balance a chassis, you should be seeking to increase it. But that's too much work and too much expense for your average 205 owner so f*** it, just whack a stiffer bar in.

 

Whack a stiffer bar in there and run stickier tyres. Problem solved!

[Guest Pär Hansson]

Sorry for the delay in nurturing my thread...

 

However, the main intent with my post was to point out that stiffening up the springing of the front might be a cheaper and more fun way to go than beefing up the rear ARB. I've been outrun by one lunatic with 1200 lb/in in the front and stock stuff in the rear, while I ran the "right" setup with 23/25 bars and 600 lb/in front.

 

Tire pressures, "noisy blocks"... There are lots of things to learn from you guys! I might also have a thing or two in contribution...

[24seven 104]

Never use ARB's as a first choice as a means of combating roll. they're a secondary measure which are supposed to offer a compromise between soft suspension comfort, and hard suspension body roll suppression. If you want to eliminate roll, stiffen the springs/torsion bars first, then balance the front/rear with the ARB's.

 

 

That's how I've always considered it anyway. though I can't back it up with personal experience, to advice comes from sources that can and I trust.

[Rippthrough 98]

I think if you tried 1200lb/in springs on our roads you'd end up orbiting the moon.

[taylorspug 7]

Lol!

[Guest Pär Hansson]

 

However... 600 lb/in is't that harsh?

[projectpug 0]

Blimey and i thought 300 was hard! I think it depends on the engine fitted and the weight of the car i.e stripped or extremely lightened.

I'm tempted to test it without the front anti roll bar i could also run more negative camber on the front with my RJ arms.

[Rippthrough 98]

 

However... 600 lb/in is't that harsh?

 

I'd love to have your roads then!

Even our rally cars don't run much more than 450-ish.

 

It's not a matter of being harsh, more that you wouldn't have enough suspension travel to keep the tyres in contact with the road surface!

Edited November 16, 2008 by Rippthrough

[Guest Pär Hansson]

Blimey and i thought 300 was hard! I think it depends on the engine fitted and the weight of the car i.e stripped or extremely lightened.

I'm tempted to test it without the front anti roll bar i could also run more negative camber on the front with my RJ arms.

300 is fairly balanced with a stock rear with the flexible silent blocks still fitted.

 

I ran A48 loading just 2.5 degrees negative camber, but have heard of up to -5 degrees running R888:s.

Edited November 16, 2008 by Pär Hansson

[Guest Pär Hansson]

OK, a new angle on balancing then. What is the opinion on rear drop stops?

 

I've ran drop stops without really comprehending it. The dampers bottomed out "negatively", lifted the inner back wheel and...