70 replies to this topic

[ArticMonkey]

Do you really want to book in with Matt again Hark? Get it all done at once. An over draft is there for a reason.

[Scuffers]

 

Disclaimer: I don't know anything about suspension setup. But, I thought increasing the front arb stiffness and not increasing rear spring rate would change the balance towards more understeer? Could someone explain why increasing the front arb is a good thing without matching it with other changes?

 

There should be a balance between front and rear roll. With no ARB and just the springs, roll will most likely differ front/rear and usually quite a lot. With the ARB you can balance that. So yes, in theory when you change springs, you should also change the ARB. The question is what to change it to. Having said that, the standard ARB doesn't do a lot, the rating is about equivalent to 50 lbs/inch. Which is probably OK for the standard springs. Same ARB, same inside and outside diameter I mean, but with a series of holes and using the hole with the least leverage (closest to the bar), it's about 90 lbs/inch. The 1" bar is considerably more going from over 150 at the lowest setting to over 250 lbs/inch at the highest. Going from the OEM bar to the 1" bar, you will for sure notice the difference. Even on the lowest setting.

 

out of interest, how have you arrived at those numbers?

[alexb]

Made a rig on my workbench emulating the ARB attach points. Fixed one side of the ARB and attached a steel wire with a device to tension it and a force meter in between. Then measured how much it moves with increasing force in steps of 10 kg. I used the original rubber bushes and put some pressure on them to emulate how they're fixed on the car. Would have been better to use the original brackets, but I'm using the car, so that was not an option. Borrowed some ARBs just to see what the difference was between them.

 

Did that just because I was curious and couldn't find anything about the actual rates of ARB's. And it doesn't take a lot of time to do the measurements. And I'm an anal retentive measure muppet. BTW, using the proper formula (the one that takes into account that the arms are not perpendicular to the main bar) you get results that are approximately the same.

[Scuffers]

Blimey!

 

kind of impressed...

 

(only issue with that method is that the bar when mounted to the chassis is not quite the same as the chassis mounts move a little under ARB load)

 

if you would not mind sharing, would like a copy of all your tests? (PM if you wish?)

[alexb]

Don't mind sharing, I'll PM you. No reason to be impressed, not even kind of. It's all very simple stuff. Yes, chassis mounts will move a little, but I think the bushes move more tbh. More important is using the right grease for the bushes. I used the wrong one (actually trying about 10 before asking someone and finding out the only silicon grease works well with rubber) for the first ARB and it just seizes. In that case the ARB effectively turns into a spring and is not able to transfer force from one side to the other. As with most greases the seizing only starts after a while, I really wonder how many people drive around with an ARB that's not an ARB anymore. I would if I hadn't check proper rotation some hours later.

[Zoobeef]

Don't mind sharing, I'll PM you. No reason to be impressed, not even kind of. It's all very simple stuff. Yes, chassis mounts will move a little, but I think the bushes move more tbh. More important is using the right grease for the bushes. I used the wrong one (actually trying about 10 before asking someone and finding out the only silicon grease works well with rubber) for the first ARB and it just seizes. In that case the ARB effectively turns into a spring and is not able to transfer force from one side to the other. As with most greases the seizing only starts after a while, I really wonder how many people drive around with an ARB that's not an ARB anymore. I would if I hadn't check proper rotation some hours later.

Do you know if ones like the elise parts ones come with the 'right' grease.

[Scuffers]

 

Do you know if ones like the elise parts ones come with the 'right' grease.

 

not sure they supply one with rubber? (certainly the 7/8" & 1" come with Nylatron bushes)

[Zoobeef]

 Do you know if ones like the elise parts ones come with the 'right' grease.  

not sure they supply one with rubber? (certainly the 7/8" & 1" come with Nylatron bushes)

That is a good point.

[Scuffers]

sure I have posted this before, but this is a std ARB (actually on an S2 but the same as a VX one)

[Hark]

Do you really want to book in with Matt again Hark? Get it all done at once. An over draft is there for a reason.

You might have a point there Stu...

[Mr Apex]

I'm not sure that I follow all of this. Purple would be quite pretty and my blue one is rusty, but... as I understand it, body roll transfers the roll centre towards the loaded front wheel. This also unloads the inside front wheel and changes the overall suspension geometry. The ARB transfers some of the compression load caused on the outside spring back to the inside spring. Cornering flatter increases precision at the expense of feel and can lead to an understeer balance - the car will push wide if the ARB is too stiff. The car will also be less compliant under cornering loads with a stiffer ARB. The biggest benefit of a stiff front ARB must be increased traction on corner exit, as the flatter cornering stance keeps the inside rear loaded. So a stiffer ARB gives you additional precision, a tendency to understeer and less compliance, but better corner exit traction.

 

It certainly doesn't seem to be a simple case of improved performance without any downside...

[Scuffers]

Please stop reading generic books!

[Mr Apex]

Never read a book on suspension in my life. Although reading does have a reputation for enhancing knowledge an understanding, so I might be tempted to give it a go. Somewhat put off by some of the guff you can find to read on internet forums at present. Physics appears to by physics, though. The uprated ARB might be an improvement in certain cases where it is balanced against stiffer springs, but otherwise it may well screw up a pretty well sorted car.

 

I don't believe that buying a stiffer ARB will just improve the car with no compromises. I can understand that harder springs equals less compliance but more precision and a better ability to deal with high grip levels. If you go down this route, then you need a stiffer ARB. That makes sense.

[Scuffers]

Never read a book on suspension in my life. Although reading does have a reputation for enhancing knowledge an understanding, so I might be tempted to give it a go. Somewhat put off by some of the guff you can find to read on internet forums at present. Physics appears to by physics, though. The uprated ARB might be an improvement in certain cases where it is balanced against stiffer springs, but otherwise it may well screw up a pretty well sorted car.

 

I don't believe that buying a stiffer ARB will just improve the car with no compromises. I can understand that harder springs equals less compliance but more precision and a better ability to deal with high grip levels. If you go down this route, then you need a stiffer ARB. That makes sense.

the problem here is that whilst the book is right in generic terms, unless you have some metrics to go by, it's not really very helpful.

 

On ARB's, yes ultimately, if you could make one stuff enough, it would be detrimental, impacting on ride quality, straight line stability on undulating surfaces, pushing the car into understeer, etc.

 

the issue here is that so far, we have not got to that level of stiffness, I'm sure if somebody made up a 1.5" bar, (and the means to mount it!) it would be capable of being too stiff, but with the 1" ones you can get now, they just don't get to that point.

 

if you run a 1" on an otherwise std car at full stiff setting, then yes, it would have an impact on it's road feel, as it will start to transfer bumps across the 'axle' leading to some 'fidgeting', but I would suggest not enough to annoy most people, and I would also not suggest running one full stiff on the road anyway.

[Mr Apex]

Fair enough - I accept that it is all a question of degree and increasing stiffness of the ARB fitted to the VX within the scope permitted by the uprated ARB may not be enough to be too detrimental to other handling aspects. Given the low CoG if the VX anyway, roll across the front axle has never felt to be too much of a problem to me. The one thing that I would like to improve is the roll across the rear axle caused by the relatively high engine mounting. I can really feel the engine trying to lift the inside rear when trail braking on turn-in. I was looking at a Ferrari the other day and it was amazing how low the engine sat.

[Scuffers]

that's more a problem of the roll centers rather than COG

[Bootdog]

 

I have one fitted, it makes a decent difference, sharper turn in, and much less body roll. I was very surprised with how little it affected the ride on standard NA suspension. I've fitted exige suspension as well, and I found it was giving me too much understeer, so I put it to the least aggressive setting (both sides closest to the front of the car).

 

 

Ehm, you for that sure mean you have it set it to the least aggressive setting, being the farthest point from the front of the car... (longest leverage setting)

 

Just shows you what I know about suspension! I just went out to check, and its in the middle hole (of 5). I'll do a back to back test with the rearmost setting to see if it helps.

[WrightStuff]

Can someone provide me with the link to the 1" arb on the eliseparts website please, I must be having a thick day, all I can see on there is the 7/8 one ??

 

Ta,

Chris

[siztenboots]

You could phone Jez at Back-on-track as his price was better than anything I could get on a groupbuy.

[Gedi]

Can someone provide me with the link to the 1" arb on the eliseparts website please, I must be having a thick day, all I can see on there is the 7/8 one ??

 

Ta,

Chris

 

it's gone!

This used to be the link  https://www.elisepar...e-anti-roll-bar