Anti Roll Bars

[Willie]

Only problem with ARBs for LCR is they are not cheap, if you upgrade and are not happy you are seriously out of pocket
For a LCR i would go R32 23mm or maybe 25mm neuspeed,etc. with rear to match
Much easier to play with the rear to balance and fine tune once the front is upto scratch
After feeling a good reasonably stiff ARB setup i doubt you will want to downgrade to softer stuff

But there's a good second hand market for them

 

[D.K]

If you get the R32 one is it worth upgradeing the bush's to poly bush's or do they come with them ???

 

[Dyscontinued]

I had the local National Tyre garage fit mine.

 

[Ronin225]

The rear bar is an easy DIY job if you have some ramps or similar but the front is more complicated
You have to drop the front subframe so unless you are confident and know what you are doing i would leave it to a garage
I had my front and rear bars fitted for 80 quid, so not bad

 

[Willie]

If you get the R32 one is it worth upgradeing the bush's to poly bush's or do they come with them ???

I just used the R32 ones bought with the bar

 

[speedsix]

There is quite a lot of confusion regarding ARBs and how they work. ARBs affect chassis balance as discussed, i.e the tendency to over/understeer. The key thing which some people don't grasp is, it's the relative thickness front to rear which defines balance and not the individual thickness of each bar. Saying something like 'a 25mm front bar will give massive understeer' is meaningless if you don't know the size of the rear bar. A standard LCR has a larger front bar than rear I believe so increasing the thickness of both, but much more so at the rear (say 25/28mm) will decrease understeer/increase oversteer considerably.

Thickening one end pushes grip to the other end, it doesn't remove or add grip, just moves it (this is important to remember) The net thickness of the bars (how thick they are combined) purely determines roll resistance, which in terms of actual out-and-out handling performance matters little but does give considerably more confidence to the driver when pushing on at the detriment of ride comfort.

 

[lordgibbness]

Been doing a bit more research and came across a discussion between two drivers about setting up a car - not an overly-technical discussion but they did both notice that adding overly stiff sway bars did cause that end of the car to lose some traction.

http://insideracingtechnology.com/disccosmo.htm

The stiffer the bar, the less grip in that end of the car. Why? I really don't know why.

What are the benefits and tradeoffs of using an anti-roll bar? Benefits or tradeoffs of using an anti-roll bar as opposed to...what? Not using one or changing something else in the car? I'd say a benefit is less roll! The more level the car stays during weight transfer the better. Why, I'm not really sure. You can stiffen the front bar to control most of the cars roll and reduce wheel spin, but risk losing grip in front. You can stiffen the rear to get a car to rotate but risk gaining wheel spin at the same time.

Now, thought I'd take a quick look at some technical theory regarding ARBs and the wiki article is quite a good place to start.

http://en.wikipedia.org/wiki/Sway_bar

Good read, starting with the obvious that they reduce roll (which isn't a nice sensation when driving fast, and gone unchecked a car could roll off the road), but the article also states the downsides.

Although Anti-roll bars reduce body lean, this comes at the expense of increased load transfer at the end it is applied to. To keep the body level in cornering, the bar pulls up on the inside tire (therefore under loading it) and pushes on the outside wheel (over loading it). Anti-roll bars therefore reduce overall grip at the end they are installed to.

It also goes on to mention an overly stiff bar will increase side-to-side body motions; how different bars can be used to dial in understeer or oversteer; and that they effectively allow a soft suspension setup to remain comfortable while reducing roll.

From reading these and other articles it appears to me that to get the best handling possible would require a proper suspension (springs & shocks) upgrade, which will improve cornering body roll without decreasing grip levels. However, at this moment in time this is not something that I am considering as it is a daily driver that I want to remain quite comfortable and also I am not dissatisfied with grip levels as it stands currently.

My car handles nicely - I think it's quite neutral - more towards understeer than oversteer, but quite fun to drive. It's mainly when on some tightening motorway slip roads that I notice body roll and it would be nice to reduce this slightly. I'm therefore now thinking that an ARB upgrade should not be to an overly-stiff setup, but to increase the front bar slightly to perhaps 22 or 23mm and a rear ARB to match. I think 25 or 28mm might be too much - and in actual fact I'm wondering if it is better to have the rear softer or the same as the front (as you know, stock setup has softer rear).

I don't want to lose too much grip in the trade-off for less body roll. For these reasons I'm thinking of either the Neuspeed 22mm or R32 23mm front, and Whiteline 22mm rear (as Neuspeed don't appear to offer this). Has anyone got a setup with the front and rear ARBs matching or the rear being slightly softer than the front?

Laslty, I know Rudd mentioned only Neuspeed bars fit with the OEM exhaust on the LCR - is this definately the case?

Thanks again - this thread has been very useful so far.

 

[lordgibbness]

There is quite a lot of confusion regarding ARBs and how they work. ARBs affect chassis balance as discussed, i.e the tendency to over/understeer. The key thing which some people don't grasp is, it's the relative thickness front to rear which defines balance and not the individual thickness of each bar. Saying something like 'a 25mm front bar will give massive understeer' is meaningless if you don't know the size of the rear bar. A standard LCR has a larger front bar than rear I believe so increasing the thickness of both, but much more so at the rear (say 25/28mm) will decrease understeer/increase oversteer considerably.

Thickening one end pushes grip to the other end, it doesn't remove or add grip, just moves it (this is important to remember) The net thickness of the bars (how thick they are combined) purely determines roll resistance, which in terms of actual out-and-out handling performance matters little but does give considerably more confidence to the driver when pushing on at the detriment of ride comfort.

From what I have been reading, due to an ARB underloading one tyre and overloading the other it does actually reduce grip to some degree. But you're right - ARBs have to be thought of in the whole setup, not individually. For example, if you have very stiff springs/shocks then smaller ARBs will be needed. Again, for a lighter car smaller ARBs can be used. And they can be used for balancing the front and rear, but I think it is true that the bar will affect the grip on that axel...

 

[speedsix]

From what I have been reading, due to an ARB underloading one tyre and overloading the other it does actually reduce grip to some degree. But you're right - ARBs have to be thought of in the whole setup, not individually. For example, if you have very stiff springs/shocks then smaller ARBs will be needed. Again, for a lighter car smaller ARBs can be used. And they can be used for balancing the front and rear, but I think it is true that the bar will affect the grip on that axel...

They do reduce grip at the end that is being stiffened but that grip is not lost, it's just moved to the other end.

Imagine a model car sitting on a road of plastacine, the car has a rod sticking vertically up from the roof which you use to simulate weight transfer, pushing it side to side. Now imagine an extreme example of this car having completely solid springs on the front and very soft springs on the rear. If you then pushed the rod to say the right side as if the car was cornering hard left. If you removed the car and looked at the imprint, you'd notice the front right tyre would make a big indent in the plastacine, the rear right nowhere near as much.

The key factor here is the difference in the indents across each axle, the fronts would be a big difference left to right (with a deep indent on the right) the rears would create almost identical depth indents. This matters because, as you may know, pushing harder down on a tyre increases the traction it has with the road surface, but the important thing to note is a loaded wheel gains less traction than an unloaded one loses So working with that you can deduce that weight transfer causes a net loss of grip along each axle and increasing spring/ARB rate just moves weight transfer to that end.

NOTE you cannot decrease overall weight transfer (well, not without changing your centre of gravity/weight etc.) merely move it around from end to end. Suspension components like stiffer springs/arbs don't reduce weight transfer, they just re-distribute it, thus affecting balance. Also, you still have weight transfer without body movement, a go-kart for example with no suspension still has weight transfer.

ARBs are basically just springs which only work during cornering.

 

[lordgibbness]

They do reduce grip at the end that is being stiffened but that grip is not lost, it's just moved to the other end.

I'm not 100% convinced with your explanation of this. I don't think a car has a fixed amount of grip that you are just moving from front to back with ARBs. I think that what the ARB does, by reducing body roll, is putting additional pressure on one suspension strut and this actually reduces the level on grip on that tyre.

I think it's a trade-off, as all things are with a road car. The reduction in body roll will reduce grip, but we are probably talking about very small levels. Conversely, the reduction in body roll will mean the centre of gravity is much more of a constant (due to less weight transfer) and will therefore result in faster cornering.

I think the examples you are describing are more to do with comparing soft and hard springs.

 

[lordgibbness]

Quite a good discussion on this site: http://www.mini2.com/forum/first-ge...-stiffer-rear-sway-bar-reduce-understeer.html

 

[ManOnTheMoor]

I'm confused now (might be the being up since 0300) but the H&R kit listed for the 1.9 tdi FR is 26mm front, 22mm rear.

I was looking to get this kit, but this discusson appears to have the larger bar at the rear ?

Has anyone else got this kit, what difference would this setup make - i note Eibach is 25/25

cheers

 

[lordgibbness]

This matrix gives an idea of percentage increases in stiffness between ARB sizes (of the same design)

http://www.balancemotorsport.co.uk/sitepage/Whiteline.html

 

[lordgibbness]

I'm confused now (might be the being up since 0300) but the H&R kit listed for the 1.9 tdi FR is 26mm front, 22mm rear.

I was looking to get this kit, but this discusson appears to have the larger bar at the rear ?

Has anyone else got this kit, what difference would this setup make - i note Eibach is 25/25

cheers

From everything that I've been reading so far (and it's been quite a lot of information), ARBs should really be used to finalise a setup. Once you have your springs and dampers setup as you want, then you can use ARBs to fine tune to reduce body roll and keep the handling neutral etc. I agree with you that it seems a little strange that some of the aftermarket ARBs are larger at the rear when this goes in the opposite direction to the OE setup.

In my case I am really happy with the current setup I have, and so if I do uprate ARBs I think I will keep the front ARBs stiffer or equal to the rear. I will also be raising most of the things discussed here with my two tuning garages to get their opinions as I always believe people are quite biased by their purchases and placebo often takes over and I like an outside view.

 

[speedsix]

I agree with you that it seems a little strange that some of the aftermarket ARBs are larger at the rear when this goes in the opposite direction to the OE setup.

This is purely to create a more understeer biased setup, just like pretty much every standard road car sold.

ARBs are just springs, adjusting spring rate will achieve the same outcome as adjusting ARB stiffness, they achieve the same function. The only difference being, ARBs do not have any effect when both wheels move in parallel (no twisting affect)


There is no voodoo to it, increasing stiffness of the rear/decreasing the front (or both) will push balance towards oversteer. In regards to losing grip, well, if you went too stiff you obviously run the risk of causing issues on bumpy surfaces but in terms of the physics of ARBs, you are not losing grip, just moving it.

I don't agree that ARBs are to be used to 'fine tune', they are a key component that adds to the overall spring rate. Obviously you need to take into consideration your spring rate before chossing ARB stiffness, your suspension kit may be tuned to give a fairly neutral balance out of the box (you would hope!) so throwing on some very rear biased ARBs may push you into considerable oversteer. A lot of people seem to do this, they buy a suspension kit and set of rear biased bars and then throw them on at the same time without testing each!

Everyone gets hung up on body roll and yes, while body roll does cause less than desireable tyre geometry, it does have a relatively small effect on actual handling performance.

Conversely, the reduction in body roll will mean the centre of gravity is much more of a constant (due to less weight transfer) and will therefore result in faster cornering.

Body roll has a negligible affect on your CoG. Any amount of weight transfer reduces your overall grip levels so minimizing it is desireable but this can only be achieved via reductions to weight/CoG/track etc. (hence why race cars are light, low and wide) and cannot be altered by suspension components. What you can do with suspension components is alter how this weight transfer is distributed and how quickly it moves around.

 

[lordgibbness]

A couple more articles to read:

http://www.houseofthud.com/cartech/swaybars.htm

http://auto.howstuffworks.com/question432.htm

 

[lordgibbness]

From what I've been reading about adjustable bars, it seems the middle setting is the equivalent to a standard non-adjustable bar. So for a 22mm adjustable ARB, the softest setting is like a 20mm bar, the middle 22mm and the hardest more like 24mm. I'm not sure if this applies to all bars, but this is what I read about the Whiteline ARBs.

 

[lordgibbness]

This is purely to create a more understeer biased setup, just like pretty much every standard road car sold.

I think this is probably better for a road car - especially a daily driver that might have more than one driver. Even a tuned/modified car will be a much nicer place if it is slightly on the understeer side of neutral, as opposed to oversteering on corners and then having to put on some opposite lock to keep in on the road.

I think it's different on a track where you might thrown it around a bit more, or a rally type setup where you actually throw the back out to get around a tight corner quickly.

In my experience, when I had the Rosso tyres prior to the Goodyears I had some lift of oversteer and the ESP would brake some of the wheels to bring it in line. It isn't a nice thing to be happening, and with ESP enabled (as it always is) you can't really have proper oversteer slides in the Leon as it will always intervene. I'd prefer a very grippy, flat cornering, neutral/understeer - which can then be tucked into the corner by reducing throttle input. This is the main reason I am thinking a smallish front arb upgrade and a smaller rear bar would work...

 

[speedsix]

I think this is probably better for a road car - especially a daily driver that might have more than one driver. Even a tuned/modified car will be a much nicer place if it is slightly on the understeer side of neutral, as opposed to oversteering on corners and then having to put on some opposite lock to keep in on the road.

I agree, the ideal setup is generally thought of to have a slight push towards understeer when reaching the limit during steady state cornering (standard setup is more than a slight push!). This doesn't mean to say that a thicker rear bar than front will not achieve this, it's all dependant on the combined rate of both your existing springs and the intented ARB.

The only way you'll get this how you want is trial and error, obviously an adjustable bar is desireable here.


I've settled on 25mm front with a 28mm rear on the stiffest setting with standard spring rate. This gives a really quite repsonsive rear end to throttle inputs.

 

[Ruddmeister]

I think we could argue theory all day and get bogged down in argument.

The most usefull information for users on the forum is recording what people have tried and how they found the balance of the car, even better if they have tried several different solutions.

As I said before the logical approach would seem to be upgrading the front and rear in rough proportion, although the slight rear bias of the 25/28mm front/rear (or similar ratio's) should be ideal IMO as the OEM LCR rolls / understeers more.