ARB: Why wouldn't I

[Johno]

Change the existing 19mm rear ARB for a 22mm thicker bar, effectively stiffening up the rear end.

I'm not interested in not running one, I've done both with this car and it feels better with an ARB rather than without.

I'm forced to replace so it's only a debate on whether to change to a 22 rather than a standard 19, as hitting a high drain in the South of France in September ripped off the n/s bracket, it dropped, evidently the hit re-arrange the bar's profile. The wishbones and plates are fine as the bar distorted and then the SH drop links snapped ;( (to be expected and no comment of Steve's fine product at all, rather the annoyance of more bit's to buy)

[spend]

I don't think its really a suitable topic for gleaning others experiences, the contribution that the ARB makes to the dampers means it is very difficult to predict what you need or want? IYSWIM.

I must confess to having often pondered how to change the design to make the roll bar an adjustable stiffness?? drill and plate with stiffeners? a blade arrangement seemed a bit too complex to engineer in IMHO...

[Johno]

I agree completely Spend, but it's always worth asking the masses. Personally I'm sold on the idea and have been considering for a while what's the best way forward. For me it's about trying to improve the consistency of the rear suspension and reducing the weight transfer, without over doing it and trying to turn it into a track day special.

I'd like to change the crud brackets and poly bushes for a billet bracket so that the transition is more linear and the action isn't just lost in loads of twist.

In fairness though the chassis bracket are such an after thought I think you'd run into issue with the strength of the plates depending on what use you were putting it through. I considered a blade arrangement, but the blades would be at quite an angle to the central bar, where I would have though that ideally you'd want them to be more at 45 degrees?

Edited by Johno on Sunday 24th January 19:46

[Johno]

Quinny said:

Mmmmm.. My view would be to stick with what you know...

Also you mention that the original 19mm bar bent in the impact.. In my mind this is a good thing, and may have saved the wishbone..

If the same thing were to happen again a 22mm bar, could be a bit too strong and transfer any impact forces into other parts of the chassis..

Jeez Quinny . . . If we all did that we wanted have different dampers, springs, wheels, tyres, engine, induction . . . . . . .

It's what we do, further trying to enhance our beast's

What i don't want to do is ruin it and a 10-15% increase in diameter, assuming diameter is linear with stiffness (big assumption I know) it's not such a huge jump . .

[deeen]

I think stiffness is proportonal to cross-sectional area, i.e. square of diameter.

All other things being equal, if you stiffen the rear in relation to the front, i believe it will sharpen turn-in / increase oversteer / feel more twitchy (3 sides of the same coin?).

Might be worth considering increasing front roll stiffness by the same amount, to maintain balance?

imho disclaimer etc

[Johno]

Quinny said:

You know exactly how the 19mm bar performs, and was (I guess) reasonably happy with it..

Think of the extra weight man

Well that's kinda the point, on the basis I'd already been considering the change, now it's forced my hand. I've been considering for a while what the effect of a stiffer bar may be.

As for extra weight, there's one thing to over come additional weight . . . POWER upgrades to that department to follow . ..

[Johno]

I can honestly say having a bar and not having a bar made a difference on my car. Perhaps it was the enforced back to back testing. 2500 miles through France and the Alps with it fitted an working, then another 1500 miles without an ARB (or at least connected to the car versus in a bin bag in the boot )

Brackets are buggered as that's what took the blow, so I've got to buy brackets and a bar. . . .

I agree more than most on more is not necessarily better . .

[haircutmike]

IMO, the standard springs are too soft and the ARB should be left alone.

I have kept the ARB standard, increased the spring rate and adjusted the dampers accordingly.

The car now rolls very little and is much more composed.

P.



Damn, I'm on the chest hair circus again !

[Johno]

Nitrons all round with higher rate springs . .. Poly bushed throughout . . Steve Gugliemi set up etc ..

I think I would need to stiffen the front at the same time as highlighted and this provides more issues in terms of sourcing one ..

I think I shall re-do the springs the first and then consider my options again as I've only got a couple of days to make my mind up . ..

Edited by Johno on Sunday 24th January 20:50

[jeremyc]

Johno said:

I can honestly say having a bar and not having a bar made a difference on my car.

What difference did you notice without the bar compared to with?

Did it increase or decrease the tendancy to understeer?

[haircutmike]

Johno said:

Nitrons all round with higher rate springs . .. Poly bushed throughout . . Steve Gugliemi set up etc ..

I think I would need to stiffen the front at the same time as highlighted and this provides more issues in terms of sourcing one ..

I think I shall re-do the springs the first and then consider my options again as I've only got a couple of days to make my mind up . ..

Edited by Johno on Sunday 24th January 20:50

My first standard + 20% was an improvement but still too soft.

I am now running 450F & 400R with Pro-tech dampers.

With the heavier springs, I can run softer damping.

Before with the softer springs, I had to wind up the dampers to compensate.

P.

[Johno]

jeremyc said:

Johno said:

I can honestly say having a bar and not having a bar made a difference on my car.

What difference did you notice without the bar compared to with?

Did it increase or decrease the tendancy to understeer?

It'll be different to different drivers I am sure and let it be clear that we weren't on a track and did have a boot full of kit for 2 weeks touring including tent etc . .. not the ideal comparative environment, but it was the same for with and without.

However, when pushing on it did feel it under steered a little, turn in didn't feel as sharp, but the key difference was the sense the opposing rear wheels were not connected. Which is what I expected, you could distinctly feel each wheel working more independently if you see what I mean.

[Johno]

haircutmike said:

With the heavier springs, I can run softer damping.

Before with the softer springs, I had to wind up the dampers to compensate.

That's exactly the point I want to get to with the set up. At the moment to stiffen up the roll I have to wind up the dampers, which then compromises ride. It's that trick of finding a balance that keeps the ride acceptable for the majority of driving and when we enter the Alps and Italy this year for the twisty bits to sharpen up the over roll dynamics.

[Ballistic Banana]

Isn't there some stronger wishbones out there too that have a better/stronger bracket for the ARBs?? might be worth a look if you do go larger..

BB

[haircutmike]

Johno said:

haircutmike said:

With the heavier springs, I can run softer damping.

Before with the softer springs, I had to wind up the dampers to compensate.

That's exactly the point I want to get to with the set up. At the moment to stiffen up the roll I have to wind up the dampers, which then compromises ride. It's that trick of finding a balance that keeps the ride acceptable for the majority of driving and when we enter the Alps and Italy this year for the twisty bits to sharpen up the over roll dynamics.

Exactly!


With the present set up I thought the ride would be really harsh, far from it it's really compliant.

P.

[dnb]

I have a 22mm rear ARB on my car. As far as I know it was the one TVR fitted in the factory.

It allows me to run softer suspension without worrying too much about the downsides - The IOW roads are very bumpy, so compliance in suspension is necessary, but also limiting roll is a good thing.

Deeen is right. Stiffness is proportional to the square of the diameter. So chances are you'll break mounts, links and wishbones more than before. Mine's broken lots of things related to the ARB in the past.

Why not give it a go and see what happens.

[Johno]

The 22mm was the factory 'sports' upgrade . . . what diameter is your front one ?

[dnb]

26 or 28mm. I don't remember off hand - it's been at least 2 years since I changed the bushes on it. It all fits with it being the factory sports upgrade.