I note that Whiteline list an adjustable rear ARB for the Golf V GTi but not the Octavia II VRS. Now, I thought these two cars were built on the same platform with same suspension? This begs the question, has anyone put Whiteline's Golf GTi rear ARB on the Octavia VRS?

I have previously had good experience of Whiteline products on Subarus, so would be keen to use again.

I note that Whiteline list an adjustable rear ARB for the Golf V GTi but not the Octavia II VRS. Now, I thought these two cars were built on the same platform with same suspension? This begs the question, has anyone put Whiteline's Golf GTi rear ARB on the Octavia VRS?

I have previously had good experience of Whiteline products on Subarus, so would be keen to use again.

It is probably quite safe to say that any anti-roll bar listed for the Golf V with fit the Octavia II vRS (and others) as they are the same basic floorpan and suspension.

Have a read of this thread;- http://briskoda.net/octavia-ii/taking-rs-next-level/83115/ that has a lot of info about ARBs and this one;- http://briskoda.net/octavia-ii/whiteline-arb-rs-whish-setting-best/135451/ for more specific info on fitting a Whiteline ARB.

For me; yesterday afternoon I swapped my Neuspeed 25mm rear arb for a new (only recently released and first one sold by Awesome GTI) APR Tuning 27mm rear arb, details here;- APR - High Performance Development for Volkswagen Vehicles

A little early to say what changes/improvement have been made to the handling but I'm sure something good has happened.

I have a whiteline ARB on my RS CR. Its the same as the MKV GTi and it really tightened up the front end. If you get one put it to its stiffest setting with the heavier tdi engine it needs to be stiffer.

JC

For me; yesterday afternoon I swapped my Neuspeed 25mm rear arb for a new (only recently released and first one sold by Awesome GTI) APR Tuning 27mm rear arb, details here;- APR - High Performance Development for Volkswagen Vehicles

A little early to say what changes/improvement have been made to the handling but I'm sure something good has happened.

That's interesting. However I note the APR bar is tubular whilst the Neuspeed is solid isn't it? For a given diameter a solid bar is a fair bit stiffer than a tube, so the APR might be no stiffer than the Neuspeed. Is their any data on the actual stiffness of these bars, rather than simply the diameter (which is not a accurate guide to stiffness).

I have a whiteline ARB on my RS CR. Its the same as the MKV GTi and it really tightened up the front end. If you get one put it to its stiffest setting with the heavier tdi engine it needs to be stiffer.

JC

Thanks. Mine's a TFSI. The stock handling is pretty good so I want only a small increase in rear lateral stiffness. The car is actually my wife's and I know from long experience that going over-stiff at the rear can lead to twitchy and erratic handling, especially on greasy roads. It want the can to stay as an 'understeerer' in extremis, I don't want her turning at around on a wet roundabout.

Hmm interesting.

The outside of the bar is where the stiffness is, as you go towards the centre of the cylinder the material has less and less effect on the "stiffness". How much however depends on the material and I suppose the thickness of the tube.

I found this http://python.rice.edu/~arb/Courses/615_sway_bar.pdf

However it doesn't say how thick the tube is.

id bet that most RARBs for the vRS were probably initially designed for the Golf MKV(much bigger market). Also the vRS has much more body roll than the gti in standard guise.

and with the rear end of the octavia being much bigger than the golf, i think it would need the RARB to be set to a stiffer position to get the same benefits.

Hmm interesting.

The outside of the bar is where the stiffness is, as you go towards the centre of the cylinder the material has less and less effect on the "stiffness". How much however depends on the material and I suppose the thickness of the tube.

I found this http://python.rice.edu/~arb/Courses/615_sway_bar.pdf

However it doesn't say how thick the tube is.

Thats sorts a previous discussion about which is stiffer, Solid or tubular bars, But you still need to take into account what constructionmaterials are used and the methods of making them. Manufacturers should state the increase in stiffness via a percentage

Thats sorts a previous discussion about which is stiffer, Solid or tubular bars, But you still need to take into account what constructionmaterials are used and the methods of making them. Manufacturers should state the increase in stiffness via a percentage

Agreed. I think with a lot of them though it's going to be down to trial and error.

Hmm interesting.

The outside of the bar is where the stiffness is, as you go towards the centre of the cylinder the material has less and less effect on the "stiffness". How much however depends on the material and I suppose the thickness of the tube.

I found this http://python.rice.edu/~arb/Courses/615_sway_bar.pdf

However it doesn't say how thick the tube is.

Many many years ago I did a degree in physics. In the first year we had to do lots of 'solid mechanics', 'dynamics' etc etc. One of the things we did was solid bars versus tubes.

The stiffness of a solid bar is proportional to its diameter raised to the 4th power (i.e. OD^4). So (back of the envelope calc) a 24mm solid ARB should be around 40-50% stiffer than the OEM 22mm bar.

In the case of a hollow bar the formula for stiffness of the bar is:

[(OD^4) - (ID^4)]^0.25

So to calculate the stiffness of the hollow bar you need to know its ID (i.e. you need the wall thickness of the tube).

In the case of the 27mm hollow bar mentioned in a post above then assuming a wall thickness of 2mm it will have an equivalent stiffness to a 22.5mm solid bar. Obviously there are other factors such as the material used.

The main reason for using hollow bars is weight saving, for a given diameter they are always less stiff and more prone to road damage.

That's interesting. However I note the APR bar is tubular whilst the Neuspeed is solid isn't it? For a given diameter a solid bar is a fair bit stiffer than a tube, so the APR might be no stiffer than the Neuspeed. Is their any data on the actual stiffness of these bars, rather than simply the diameter (which is not a accurate guide to stiffness).

Neuspeed arb is tubular as well. see here;- . ..:. Neuspeed Product Details .:.. .

Hmm interesting.

The outside of the bar is where the stiffness is, as you go towards the centre of the cylinder the material has less and less effect on the "stiffness". How much however depends on the material and I suppose the thickness of the tube.

I found this http://python.rice.edu/~arb/Courses/615_sway_bar.pdf

However it doesn't say how thick the tube is.

This all flies in the face of my experience from karting where, for a given diameter, a solid rear axle is used in the wet as it gives more 'flex' than a hollow (tubular) axle, which is used in the dry, when tighter handling is required. Also, why is it that a 'circus strongman' bends a metal bar, as opposed to a tube or pipe? .. because it (a solid bar) is easier to bend.

However; I think we'll find that all aftermarket ARBs are tubular, so the comparison is, in practice, irrelevant.

Many many years ago I did a degree in physics. In the first year we had to do lots of 'solid mechanics', 'dynamics' etc etc. One of the things we did was solid bars versus tubes.

The stiffness of a solid bar is proportional to its diameter raised to the 4th power (i.e. OD^4). So (back of the envelope calc) a 24mm solid ARB should be around 40-50% stiffer than the OEM 22mm bar.

In the case of a hollow bar the formula for stiffness of the bar is:

[(OD^4) - (ID^4)]^0.25

So to calculate the stiffness of the hollow bar you need to know its ID (i.e. you need the wall thickness of the tube).

In the case of the 27mm hollow bar mentioned in a post above then assuming a wall thickness of 2mm it will have an equivalent stiffness to a 22.5mm solid bar. Obviously there are other factors such as the material used.

The main reason for using hollow bars is weight saving, for a given diameter they are always less stiff and more prone to road damage.

However; in the light of the above; I defer and stand to be corrected.

Edited 22 February, 200917 yr by bahnstormer vrs

Neuspeed arb is tubular as well. see here;- . ..:. Neuspeed Product Details .:.. .

This all flies in the face of my experience from karting where, for a given diameter, a solid rear axle is used in the wet as it gives more 'flex' than a hollow (tubular) axle, which is used in the dry, when tighter handling is required. Also, why is it that a 'circus strongman' bends a metal bar, as opposed to a tube or pipe? .. because it (a solid bar) is easier to bend.

However; I think we'll find that all aftermarket ARBs are tubular, so the comparison is, in practice, irrelevant.

Sorry, I'm new to this forum, wasn't trying to be controversial.

You're right that the Neuspeed is tubular, my apologies.

I think most ARB's are solid, its much easier to make a solid bar (no awkward mandrel bends to worry about) and they are more robust. Also they are less likely to fail through fatigue or kinking (due to impact with debris etc). Certainly the Whiteline bars are solid (I've used them in the past 'professionally' on Subarus).

I don't know anything about karting but a hollow bar of given diameter is less stiff than a solid bar, that's just basic physics. I guess the reason a circus strongman bends a solid bar is that a hollow bar would simply 'kink' and fold double, which wouldn't be very entertaining!

This all flies in the face of my experience from karting where, for a given diameter, a solid rear axle is used in the wet as it gives more 'flex' than a hollow (tubular) axle, which is used in the dry, when tighter handling is required. Also, why is it that a 'circus strongman' bends a metal bar, as opposed to a tube or pipe? .. because it (a solid bar) is easier to bend.

However; I think we'll find that all aftermarket ARBs are tubular, so the comparison is, in practice, irrelevant.

That's kind of what I was saying, I suppose the PDF is irrelevent as there is too much data missing to explain the results. However if you were to deal in the same material and same diameter it should mean the solid would be stiffer but the % stiffer wouldn't be proportional to the amount of material, weight or production costs.

BTW the Whiteline RARB is solid and the Jabba bar is solid.

An ARB shouldnt bend, it is the torsion that does the trick.

And a bigger diameter should be stiffer.

Sorry, I'm new to this forum, wasn't trying to be controversial.

You're right that the Neuspeed is tubular, my apologies.

I think most ARB's are solid, its much easier to make a solid bar (no awkward mandrel bends to worry about) and they are more robust. Also they are less likely to fail through fatigue or kinking (due to impact with debris etc). Certainly the Whiteline bars are solid (I've used them in the past 'professionally' on Subarus).

I don't know anything about karting but a hollow bar of given diameter is less stiff than a solid bar, that's just basic physics. I guess the reason a circus strongman bends a solid bar is that a hollow bar would simply 'kink' and fold double, which wouldn't be very entertaining!

Thank you for preventing me (lazy fellow) from going back to those college days

Thought I ought to post some comments about my excellent APR 27mm rear ARB. Fitting was straight forward, up on the ramp Neuspeed bar off and APR bar on, ramp down; time taken 20mins.

As weather is still cooler I set it up on the medium stiffness which is +135% on an OE bar and certainly something more than my 25mm Neuspeed bar of the stiffest setting.

It really improves the car, I can feel the rear of the car being held flatter and thus the nose does not pitch forward onto the outside front wheel. Steering is noticeably more direct with no noticeable understeer. I managed to go around one of my favourite large roundabouts this morning with no traffic around and I have a wide sweeping left hander out of a roundabout on my nightly commute (taken full throttle in 4th); for both of these the car is really nicely neutral and with a gentle lift just tucks the nose in a bit; sweet!

In a few weeks time I'm going to move up the the stiffest setting, giving +200% on an OE bar and run this for the summer; should be fun.

Overall; very worthwhile and enjoyable investment - highly recommended.

Sounds good Where did you buy from?

Steve

Sounds good Where did you buy from?

Steve

I'll give you a clue;- http://briskoda.net/awesome-gti/apr-anti-roll-bars-octavia-ii/134460/

Many many years ago I did a degree in physics. In the first year we had to do lots of 'solid mechanics', 'dynamics' etc etc. One of the things we did was solid bars versus tubes.

The stiffness of a solid bar is proportional to its diameter raised to the 4th power (i.e. OD^4). So (back of the envelope calc) a 24mm solid ARB should be around 40-50% stiffer than the OEM 22mm bar.

In the case of a hollow bar the formula for stiffness of the bar is:

[(OD^4) - (ID^4)]^0.25

So to calculate the stiffness of the hollow bar you need to know its ID (i.e. you need the wall thickness of the tube).

In the case of the 27mm hollow bar mentioned in a post above then assuming a wall thickness of 2mm it will have an equivalent stiffness to a 22.5mm solid bar. Obviously there are other factors such as the material used.

The main reason for using hollow bars is weight saving, for a given diameter they are always less stiff and more prone to road damage.

What you are referring to is the "polar moment of inertia" - in laymans terms the torsional stiffness of the bar (i.e. how it resists twisting)

a simplification for your formula is (outside diameter cubed x wall thickness) - thick works best when wall thickness is 10% or less of OD.