H&R Anti Roll Bar Settings

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Gazza
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

Mine are set on the hard setting ?, outermost hole.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

Not sure hence the ? :wink:
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

I'll let you have a play with that :D
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Re: H&R Anti Roll Bar Settings

Post by Deano1712 »

Soft setting for me (holes at the end). Never tried the firmer setting but it seems fine as-is to me.
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Yes softest obviously at the end holes.

I've currently got mine stiff front soft rear, seems fine.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

I'll check mine to be certain, the memory isn't what it once was :lol:

I will say that whatever setting the rear is on, it has torn the floor mount away from the floor and recently torn the lower mounting from the trailing arm, both requiring welding.
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Re: H&R Anti Roll Bar Settings

Post by Z3cade »

I didn't even know they were adjustable! Have no idea what mine are set as.. Where abouts are the holes on the bars?
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

At the ends where they attach to the droplinks
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Re: H&R Anti Roll Bar Settings

Post by siwilson »

Good thread on the Coupe board about this. See page 2 or 3 for photos.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

Zedonist wrote:You must do some extreme driving Gary, did it actually rip the sheet metal, or did the fasteners break?
Not really, just been installed about 5 years now and I was expecting it as the ARB's are soooooo much stiffer. The trailing arm bracket failure has been documented by others so that was expected at some point but I didn't expect the floor mount to fail. No tearing of the sheet metal, just the welds failed.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

The thread that Si has linked shows the bracket and reasons for failure
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

I'm not saying it's flimsy, just that the extra thickness of the H&R bars induces much more stress in the mount.
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Re: H&R Anti Roll Bar Settings

Post by siwilson »

Gazza wrote:I'm not saying it's flimsy, just that the extra thickness of the H&R bars induces much more stress in the mount.
+1, the H&R are about 2x as stiff as the standard and the standard mounts were just not designed to handle the extra stress. No fault of BMW, just a reality.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

Zedonist wrote:It should actually reduce stress, the body is not rolling as much, hence reduced flex, hence less leverage on the joints, it is the weight of the body that adds the stress, the thicker bar would keep it in check, if welds are breaking then the joint is going into shear, and it is not designed this way, the only thing that could put the joint into shear would be for it to be loose and then it would pull side ways as well as the designed back and forth (up / down) movement. Its like the difference between trying to pull a piece of paper in two and tearing a piece of paper in two, tearing places it in shear and takes much less stress to put into two pieces.

In actual fact had to much tenslie force been applied the fasteners would have broken first,

Only a point of view........
I'm not an Engineer but I know what and why it happened to my car. Like I have said previously, it is suggested to uprate the trailing arm mounts to prevent failure, mine took 5 years to fail (unmodified). I was also advised to get uprated front droplinks (which I did) due to early failure of the OEM droplinks, I suppose due to the extra torsional ridgidity due to the increase in size of the ARB. Uprating part of the system must have an adverse affect on the other parts.
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Re: H&R Anti Roll Bar Settings

Post by siwilson »

Zedonist wrote:It should actually reduce stress, the body is not rolling as much, hence reduced flex, hence less leverage on the joints, it is the weight of the body that adds the stress, the thicker bar would keep it in check, if welds are breaking then the joint is going into shear, and it is not designed this way, the only thing that could put the joint into shear would be for it to be loose and then it would pull side ways as well as the designed back and forth (up / down) movement. Its like the difference between trying to pull a piece of paper in two and tearing a piece of paper in two, tearing places it in shear and takes much less stress to put into two pieces.

In actual fact had to much tenslie force been applied the fasteners would have broken first,

Only a point of view........
No, You got it totally wrong. The body is not rolling as much because the bar and the mounts are stopping it. Think what happens when you turn hard with no anti-roll bar. One wheel goes up and the other goes down as the car rolls around the central axis. The anti roll bar checks this roll by restricting the unloaded side of the suspension from extending. Each time you turn, the mounts at one end of the bar are being push upwards and the other pulled downwards by the torsion in the bar. Stiffen the bar and you increase the stress on the mounts. They flex a little, then more and eventually over time brake due to fatigue.

Search around and you'll find it quite common with the H&R ARBs. Gazza's died more quickly than most since he has his on the stiffer setting. Stiffer bar = more stress on mounts = earlier failure.

Oh, and he is a complete hooligan as well :D
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Re: H&R Anti Roll Bar Settings

Post by c_w »

I think it's quite obvious how the H&R bars put more load on the brackets of both the body and the trailing arms and why they are more likely to break. The easiest way of thinking about it is if there was no arb fitted at all = no load on the connections at all. The body is not that well made underneath (fixing points etc), increase the bar stiffness and it's a recipe for failure as the thin metal uses can't contain the strength of the bar that is resisting roll. If one side is pushing up the other is pull down, the trailing arms are the first to go as they do flex and that fatigue can easily snap them off.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

Doesn't matter how thick or which setting the ARB is on it won't stop the car sliding in the wet.

The principals of your argument may well be correct but in practice a thicker ARB does in fact punish the OEM mounts. Surely you can see that the extra torsional strength in a thicker bar must impose extra loading on the mounts, Force and Effect and all that stuff from my school days.
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Re: H&R Anti Roll Bar Settings

Post by c_w »

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Rear arb bracket snapped off with H&R roll bar. Of course the thicker bars stress the mounts more :lol: An anti roll bar is trying to resist the body rolling!! You can't fit these "wrong". These brackets are FLIMSY, especially the trailing arm, much like a lot of the rear end, just about enough for factory stuff but if you uprate them then the stress often overcomes the strength of the welds/metal.
Zedonist wrote: Ergo, based on this and the principles applicable on planet earth, the thicker bar did not cause the failure. As said before it will be down to poor process, components, fitting or driving the vehicle beyond its limits.
Eh?? So the bracket snaps but it's not because the stress the roll bar put on it? It just fell off of its own accord? Would it have still fallen off had there been no ARB fitted at all as in my previous suggestion? How the bracket fails [weld or bolt snapping] is completely irrelevant. The main reason the rear ends fail is from metal fatigue as it's NOT thick enough for the job. Fatter roll bars just accelerate this, not every car will suffer due to age/miles/rust/usage/luck.



In theory the stiffer settings give less grip, I've got mine stiff front and soft rear - handling is quite good but I do keep meaning to put the rear a bit stiffer but don't want to lose traction.
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Zedonist wrote:No I am saying the bracket failed because of an issue to do with the application of course there is a load applied but as stated the stress applied is less due to the cross sectional area of the bar, looking at your failure picture, the weld has failed, the rear weld would have been gone before you fitted the bars, i would say therefore that this was the root cause, a poor weld, the bracket is fine. Based on other panel weld issues on the Z3 such as the boot welds, this was probably caused by the same fault, either process or equipment it will be a time, temperature, power issue, the bracket is obviously more than man enough for the job. Plus you got to factor how many people have not had this issue with the bars fitted, and it points away from the bars, if everyone who had fitted them had the problem then you could lean in that direction.
Yes the weld has failed, it's the weakest part on the body brackets, not to say the bracket itself is particularly strong, especially the way the clamp only just clips in. The whole rear end is flimsy and how the car is driven and state of the roads will obviously influence when/if it fails. Obviously fitting H&R bars does not immediately break mounts, if you drive on smooth roads the shock loading is not nearly as bad as potholed roads for example. On my A3 everything is sized up, much thicker metals, all the ARB bolts are 18mm for example. Nothing is ever going to break on that in that department.

"the stress applied is less due to the cross sectional area of the bar"

What do you mean by this?
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Not following your logic at all.

With a larger roll bar it is the diameter that grows, it's not like a footprint. The forces are at the contact points of the body and trailing arm brackets. The bigger roll bar is contained within a bush that is essentially the same size that fits in the same bracket, not that that would make any difference anyway. The connection at the trailing arm is the same, except more force is put on it by the thicker roll bar!

For every 1mm increase in diameter the roll bar is considerable stiffer yet the diameter is "only" 1mm thicker. Ie it's strength increase is disproportionate to it's "area" in your logic by a factor of 4 which makes the stress = force/area nonsense as the 1mm thicker bar is significantly stiffer for it's size.

If there's less load applied through the axle then where has the load disappeared to?
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Re: H&R Anti Roll Bar Settings

Post by Deano1712 »

What a fun read. More carbon = higher modulus. Where did you get that one from? I wish that was indeed the case; it would help a lot in engineering.

Theory and practice both show loads increased with the bigger bar, and hence chance of failure. Simples.

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Re: H&R Anti Roll Bar Settings

Post by c_w »

So what happens, as I have said before if there is no roll bar at all, where does this "constant" load go?

Why/how is the force constant?
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Would be interested to know why it doesn't dignify an answer. The only time the load is constant is when it's at rest (and that's ZERO load). Under cornering lateral acceleration increases load on the outer wheel, with no ARB there is no load through it, with a very thin arb only a smaller load can be transferred (the twist limited within the suspension travel), with a big roll bar more load is transferred across the axle and within a smaller movement. The more cornering load the more force on the ARB. The more force on the connecting elements of the ARB (remember without an ARB there is no force on the moutning points as there's no bar there!), and hence why most tuners sell re-inforcement kits for cars with uprated roll bars.

The sheet metal breaks off the trailing arm due to the constant up and down loads being placed on the trailing arm from the swaybar. Problems increase when larger sway bars are used.
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Re: H&R Anti Roll Bar Settings

Post by Deano1712 »

Zedonist wrote:
Deano1712 wrote:What a fun read. More carbon = higher modulus. Where did you get that one from? I wish that was indeed the case; it would help a lot in engineering.

Theory and practice both show loads increased with the bigger bar, and hence chance of failure. Simples.

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Deano, I suppose being a qualified Metallurgist allows me to make such a claim, i was going to post the Iron Carbon Diagram and give you a lecture, but i feel it would be wasted. Search the internet for information on steel and the alloying effects of carbon, and then look at heat treatment of carbon steels.

However as a taster i will tell you that Carbon is one of the main alloying elements that gives steel its strength, the more carbon you add the stronger it gets during heat treatment, until it becomes saturated and produces carbides and becomes brittle at about 0.8% - 1.0% Carbon then you need other alloying elements such as Nickel and Chromium to stabilise the structure during heat treatment. At 2% carbon it is no longer a steel but a grey or a white cast iron. Mild steel has less than 0.08% Carbon in it is soft and low on strength used on body panels, An automotive alloy steel such as SAE 8620 has about 0.2% Carbon plus alloying elements is tough, responds well top carburising treatments and hence i stronger and harder and used on things such as cam shafts and other gears/shafts in your gear box. A Grade 12.9 plain carbon steel fastener will have 0.43% Carbon where a grade 4.8 fastener will have around 0.08 - 0.12% Carbon, The 12.9 is used to hold your wheels and chassis together and the 4.8 your sun visor. And yes it helps a lot in Engineering as you can see from my examples.

Examine the facts do a bit of research and get to root cause and stop looking at the symptoms, it really is as easy as the Physics and Metallurgy, or if not please tell me where the increased load has come from to create the extra stress? have you added more weight to the body of your car? No so the load is a constant, therefore you can only change its effect by changing to a thicker bar, that effect is reduced stress. Like a said earlier the failure in the pictures has happened before the point of load on the ARB Bar, It really is that simples eek!

P.S. The world is not Flat
When you reply to a post you need to read it first. You stated that higher carbon makes the steel stiffer. It doesnt. What point are you making about carbon inclusion? Impact on mechanical strength? Or impact on Youngs Modulus? The former is massively impacted but the latter hardly at all. You need to substantiate your earlier claim that higher carbon makes the bar stiffer. It doesnt and you are factually incorrect. In any case why would you assume the H&R bar is made from a higher grade of steel than the OEM version? I expect they are both going to be similar.

Dont patronise me (or others) with your answer. I have probably forgotten more about engineering than you know.
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Re: H&R Anti Roll Bar Settings

Post by siwilson »

I think we're being baited there.
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Re: H&R Anti Roll Bar Settings

Post by Jonttt »

I want to know why the earth is not flat ?

Seriously I find this an interesting discussion do hope it does not get personal. I have H&R ARBs and would like to know if they mean the car needs strengthening because of them specifically or due a potential inherent problem in the welds as per the boot floor ? I guess if the welds go with OEM ARBs in the same ratio to the number fitted that would confirm the problem is not the updated ARBs ?
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Zedonist wrote:Ok, without the roll bar the full load applies on one side of the axle one wheel will lift and depending on speed in the turn the car will flip over.

In reality the original ARB is already risisting some of this load, ergo on simple terms a thicker stiffer bar resists more of the load and keeps both wheels on the ground longer.

A constant is something that does not change, in this scenario taking the equation stress = force / Area the force part is the weight of the body of the car, this does not change when you change the size of the ARB bar, therefore it is a constant, now do the full equation and hey presto stress reduces when size of the bar is increased.

There you go dignified with an answer
So a car would flip over without an anti roll bar? :lol: you do understand that some cars don't have anti roll bars at all, and it was very common to not find one on the rear of cars. I don't think you understand the force/job that the ARB is doing. In some cases the thicker the roll bar the more chance of LIFTING an inside wheel if it pushes beyond the spring strength. The force through the roll bar is NOT constant!! You're clinging on to a basic formula but not applying it properly in this scenario. Yes the weight of the car doesn't change (aero effects aside) but the total weight through the springs is constant, even though the distribution changes. The weight distribution changes though lateral acceleration/g force. When the car is driving straight on a billiard smooth road there is NO LOAD THROUGH THE ROLL BAR. When your turn slightly the load increases, if you swerve aggressively the load is much higher, therefore the load cannot be constant through the roll bar. The stiffer roll bar resists this load more but that force has to go somewhere, it can't just disappear inside the bar; it goes through the mountings/droplinks.

btw, there are significant weight differences between a 1.9 and Z3M Coupe for example, something around 200kgs, not that this matters too much.
Zedonist wrote:Sorry the reason tuners sell uprate kits is because you use solid bushes on race prepped cars made from aluminium, hence any twist goes through the bracket, hence needs to be beefier
This is quality, so now the twisting force is now in the bracket? The twisting is done by the anti roll bar as it's a torsion bar, the bushes merely maintain a fixed point for the bar. A stiffer bush will just mean slightly less tendency for the bush to deflect/squash under load tightening response up slightly.
Last edited by c_w on Tue 06 Nov, 2012 10:40, edited 3 times in total.
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Re: H&R Anti Roll Bar Settings

Post by Gazza »

I agree this is a healthy discussion and I hope it remains that way.

My history with the ///M.......

My boot welds and diff bracket show no signs of fatigue or popped welds.

I have H&R bars fitted front and rear.

My car has suffered a bracket failure on the N/S rear floor as pictured by CW

My car has suffered a bracket failure on the O/S rear trailing arm.

These failures have recently occured within a year of each other.

The H&R's have been fitted approx 5 years.

When I bought the car it had 45k miles, now 80k miles.

I don't abuse the car but it does get driven in a spirited manner whenever possible.
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Looks like the Z4s are also suffering;

http://www.zpost.com/forums/showthread.php?t=553591

This one running Ground Control bars;
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Re: H&R Anti Roll Bar Settings

Post by c_w »

So you agree the stiffer bars have contributed to the tearing?

It looks like on the Z4 it just uses captive studs in the chassis rails and these have been pulled through the metal, there's no welding as far as I can see unless the studs are tacked. A daft design as they could have just used a larger head for the studs (photo 2) on the other side might have prevented this happening.
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Re: H&R Anti Roll Bar Settings

Post by Southernboy »

IMHO the quality of welding on the Z3 is poor and is exacerbated by the poor design and designation of weld points.
I have found the spot welds between the inner and outer doorskins to be poor, and in a couple of places they have comme away from the sheet metal brackets to which the window mechanism is attached. I have drilled these and used "hot" steel rivets to re-secure the brackets together with an epoxy in the hope of staving off replacing doors. (After 3 years they are still solid, and IMO better than the original welds)
The under car issues are no different in essence. the poor quality of spot welds, and the poor design parameters set for the number of welds leads to the failures. Stresses are not correctly assessed, and if they are, the calculations are based on incorrect premises. New metal and 24 month old metal are very different animals given the movements a vehicle goes through, which apart from the up and down movements there are the twisting movements as described in the discussion above.A spot weld subjected to a "shearing" force will withstand it better than an angular twisting force. The twisting across the face of the weld is more likely to yield it weaker especially if repeated frequently in the normal process of driving etc.
I don't consider the anti-roll bar a part of the body structural integrity. The two should supplement each other, without being hugely dependent on body welds. Anti-roll should be a suspension / chassis supplement, not a preventative against shoddy spot welding.

PS. A hot rivet - as per my application - is a mild steel nut and bolt heted white with a gas torch, inserted, the nut fitted, tightened, and allowed to cool. The contraction is immense and the bolt cannot be undone without re-heating.
In the case of my door, the option of welding wasn't possible, since the thickness of the sheeting is so thin, that the arc simply blows the metal away.
I note that with some members where they have had the diff / boot welding issue, they have opted for additional metal to support the original sheet, I reckon this is the result of a poor choice of materials in the design stage..a heavier guage sheet should have been used in those critical areas which would naturally be subjected to the "twisting" forces.
As I said....IMHO.
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Re: H&R Anti Roll Bar Settings

Post by Del »

Slightly expanding this topic, it is possible to simply drill out “bad” spot welds in say the boot area and replace with strong grade 8 nut/bolts?
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Re: H&R Anti Roll Bar Settings

Post by Southernboy »

Problem with simple nut and bolt is that one can't tighten a bolt enough to prevent movement..Hence heating it first so that it is expanded, and once tightened while hot, then allowed to cool, the contraction makes it extremely tight.
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Re: H&R Anti Roll Bar Settings

Post by c_w »

Of course the welds are the weakest link in most cases, mainly though a mixture of weld failure/corrosion and metal fatigue due to the thin gauge. In some case welds haven't failed but diff brackets have just cracked completely. With the ARBs the brackets and droplink joints have obviously been designed within a tight working envelope and with OEM bars in mind; uprated roll bars weren't on their agenda and these do stress the joints more :wink:
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peteslag
Joined: Thu 04 Aug, 2011 07:50
Posts: 145

  Z3 roadster 3.0i
Location: wolverhampton

Re: H&R Anti Roll Bar Settings

Post by peteslag »

Sorry to interupt the engineering debate but I have questions regarding the ARB kit. Since owning my Z3 3.0 I've always felt the general handling was OK but certain elements needed to be improved. First the ride height bothered me so I put it on Eibach lowering springs. Things got better but then I felt the car was a bit bouncy in the corners so got some Bilstein B8's. Things got better but now I find the car leans a bit too much in the tight twisties so my next obvious mod is a H&R ARB kit.

My question is, WHERE DOES IT ALL END????? Does this kit make a big difference? Will I unearth another handling issue that bothers me on my next track day?
Z3 3.0, Ford ST220, Jaguar XK8, Mr2 GT Turbo, Fiat Bravo HGT, Cavalier, Astra convertible, MK1 Astra GTE, XR3i, E21 323i, XR3, Cavalier, VW Jetta, Rover SDi, Capri 2.0S, Audi 80 GTE, another Cavalier, brown Astra van, Citroen GS Club (we all had to start somewhere).
swamper
Joined: Thu 13 May, 2010 17:14
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  M roadster S50
Location: Mossley

Re: H&R Anti Roll Bar Settings

Post by swamper »

the next Pete will be struts and or bushes...then top mounts...sub frame inserts on and on mate :?
the badness makes me do it...!

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Gazza
Joined: Tue 04 Oct, 2005 20:58
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  M roadster S54
Location: Romford Essex

Re: H&R Anti Roll Bar Settings

Post by Gazza »

The H&R kit will stop the lean.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

Z3 S54 M roadster Image, BMW Z1, BMW M3 CSL, Z4M Coupe
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Z3cade
Joined: Sat 09 Jan, 2010 18:18
Posts: 2634

  M roadster S50
Location: Peterborough

Re: H&R Anti Roll Bar Settings

Post by Z3cade »

Gazza wrote:The H&R kit will stop the lean.
Yep..
Mines on B8s -20-30mm springs and HnR roll bars.. Sits like a flat bed round corners :wink:
///M Roadster - Evolve Stage 3
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peteslag
Joined: Thu 04 Aug, 2011 07:50
Posts: 145

  Z3 roadster 3.0i
Location: wolverhampton

Re: H&R Anti Roll Bar Settings

Post by peteslag »

I am conflicted. I like the idea that after a track day i can jump in the car and go home in relative comfort, plus the Z3 in it's current setup makes a superb car for cruises. BUT, i could buy an old car for penuts and strip it out. This has risks though, what if it turns out to be a dog, it will also need mods/maintenance, how am I going to transport it, the list goes on........

Thanks for the feedback on the H&R kit, I think i'll buy it and have it fitted for my next track day. I can't see there being any more major issues with the handling. After all, I'm not looking for perfection, I just want something that can give me the thrill of the odd track day now and then. The Z3 was never designed for track use AND it looks great so I think the old girl should be forgiven for the odd indiscretion. Cheers :D
Z3 3.0, Ford ST220, Jaguar XK8, Mr2 GT Turbo, Fiat Bravo HGT, Cavalier, Astra convertible, MK1 Astra GTE, XR3i, E21 323i, XR3, Cavalier, VW Jetta, Rover SDi, Capri 2.0S, Audi 80 GTE, another Cavalier, brown Astra van, Citroen GS Club (we all had to start somewhere).
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