RSR Sway Bars

[chris_seven]

We have been looking for 18mm diameter (with 20mm square ends) RSR style through body sway bars for some time.

They are being re-manufactured in Germany and are available in the UK but the bars are tubular and the ends are square plugs with a spigot that is pressed in and then welded. The weld is then machined to make the bar look presentable.

We don't really want bars which are welded.

We have decided to make a batch of one piece bars with upset ends and they should be available in about 6 weeks.

Once we ahve finished the 18mm bars we will make a few 20 and 22mm bars as well.

We are making them from 300M so they should have good yield and fatigue strength.

[sp_cs]

who is 'we'?

[proffighter]

Originally Posted by sp_cs

who is 'we'?

1+

[Flieger]

"we" = Fenn Lane Motorsport (they are in England).

[DG624]

Are these bars adjustable or do you buy more than one? Also what is the rate?

[Flieger]

I think they are going to have 3 or 4 holes in the levers so that they are adjustable. That is what other "RSR" style bars have.

[winders]

Originally Posted by Flieger

I think they are going to have 3 or 4 holes in the levers so that they are adjustable. That is what other "RSR" style bars have.

3 or 4 holes? That many??

If you want RSR style anti-roll bars, I would look at Tarrett. Their RSR bars have 6 holes for adjustment front and rear.

Scott

[Flieger]

I don't remember how many holes. But what I do know from the thread on the Early 911S Registry is he wants these to be exact replicas of RSR antiroll bars. He does FIA vintage racing and those guys want very original parts.

[Flieger]

RSR Sway Bars

OK, looks like 5 holes.

[DG624]

I heard that about 25% of the spring rate should be from the sway bars...does this soud right? Also is there a way of calculating the increase in bar strength from each adjustment?

[Flieger]

You don't actually need antiroll bars if you have your main springs correct to start with and the track width and weight distribution are well matched.

[winders]

Originally Posted by DG624

I heard that about 25% of the spring rate should be from the sway bars...does this soud right?

Originally Posted by Flieger

You don't actually need antiroll bars if you have your main springs correct to start with and the track width and weight distribution are well matched.

True...but in the real world you probably want at least one anti-roll bar so you can adjust chassis balance.

Scott

[proffighter]

Originally Posted by Flieger

You don't actually need antiroll bars if you have your main springs correct to start with and the track width and weight distribution are well matched.

I do not agree. Sway bars do a lot for a good ride:

Reduce force on the outer wheel spring and add force to the inner, which reduce tendency to flip over and loose grip, avoid over- or understeer.

Further it reduce the roll steer effect. Just take a fast car and compare it's behaviour on high speed on a straight, when a bump hit's one wheel. the Sway bar add a lot of drive stability. I drove my turbo once without bars just for testing purposes and it was really scaring me...

See here too:

Sway bar - Wikipedia, the free encyclopedia

[chris_seven]

As Max says we are trying to accurately replicate the original RSR Sway Bars with 18mm, 20mm and 22mm diameters. All three bars have 20mm square ends.

The RSR drop link levers used to have 5 holes and the change in stiffness of the bar is relatively straight forward to calculate.

Looking at the 2.8 and 3.0 RSR Parts Lists the same Drop Link Levers were used front and rear and the Sway Bars were identical.

It is possible to buy RSR Replica Bars from Germany but they use a tubular bar with a MIG welded square end.

I would agree that the Tarrett Bars are sensible but we do want to make 'faithful' replicas as we have a small market for these parts.

[winders]

Originally Posted by proffighter

I do not agree.

Take a look at this thread and the articles referenced within:

BIG Sways?

You will see where Flieger is coming from.

Scott

[Flieger]

Originally Posted by proffighter

I do not agree. Sway bars do a lot for a good ride:

Reduce force on the outer wheel spring and add force to the inner, which reduce tendency to flip over and loose grip, avoid over- or understeer.

Further it reduce the roll steer effect. Just take a fast car and compare it's behaviour on high speed on a straight, when a bump hit's one wheel. the Sway bar add a lot of drive stability. I drove my turbo once without bars just for testing purposes and it was really scaring me...

See here too:

Sway bar - Wikipedia, the free encyclopedia

You mention the benefits of reducing roll, but that can be done without antiroll bars.
Anti-sway bars are primarily a tool to tune the roll couple distribution without affecting the pitch characteristics of the car (which are controlled by main springs and any heave springs). You can, however, reduce the roll angle with the normal springs just as effectively as with an antiroll bar.

The difference is that if you have very stiff antiroll bars the car will be less stable over rough surfaces because the antiroll bar transfers load across an axle much quicker than would happen with a normal spring.

For maximum grip, you want to reduce load transfer so that the tires are more evenly loaded. In a "steady-state" turning situation the total load transfer is just a function of lateral acceleration, mass center height, and track with. However, the distribution of stiffness on the front and rear axles will change the understeer/oversteer balance. This roll stiffness comes from roll center height and springs- both normal and antiroll bars. This means that any of those three can be used to tune the handling and to reduce roll.

In a transient situation (slalom, turn entry) we are talking about how fast the load transfers rather than the total amount. It is in this situation where the three types of roll resistance differ.
The one that transfers load the fastest is the high roll center. In this, the vertical force on the tire increases or decreases as soon as the tire produces a lateral force. These forces are sent through the suspension linkages themselves and bypass the springs.

Slower than the roll center are the normal springs and the antiroll bar, which both require roll angle (and therefore time) to work. On a smooth track the two are equal, but on a bumpy track the large antiroll bars will be a disadvantage. This is because when one wheel encounters a bump with an antiroll bar, the other wheel very quickly feels a force from the antiroll bar since the two sides are connected with it. With independent springs, however, the other side feels nothing until the chassis is displaced, which takes longer due to the inertia of it.

Therefore, if you can achieve your desired roll couple distribution using only independent springs you should do that.

Winders is correct that one, small (relative to main springs), adjustable antiroll bar is a nice tool to have to fine-tune the handling for different circuits. But you only should need one.

911s use front and rear mainly because fitting larg enough springs to control roll is not always possible within the stock torsion tube spline dimensions.

[proffighter]

Sometimes difficult for me to articulate and understand the tiny little things here as I am not english speaking by native (or some like that)

So I found out that the thing I meant was "warp". That behaviour is much less with sways, becaus less or no rotation around the longitudinal axis when just one wheel hits a bump, especially on higher speeds and even more on fast sustained corners (my favourites)

Anyway, nice to talk shop (is this really the word for that??) with you guys

[175K911]

Originally Posted by chris_seven

As Max says we are trying to accurately replicate the original RSR Sway Bars with 18mm, 20mm and 22mm diameters. All three bars have 20mm square ends.

The RSR drop link levers used to have 5 holes and the change in stiffness of the bar is relatively straight forward to calculate.

Looking at the 2.8 and 3.0 RSR Parts Lists the same Drop Link Levers were used front and rear and the Sway Bars were identical.

It is possible to buy RSR Replica Bars from Germany but they use a tubular bar with a MIG welded square end.

I would agree that the Tarrett Bars are sensible but we do want to make 'faithful' replicas as we have a small market for these parts.

I'm sure you're up to speed on this, but be sure to check with Wayne for permission to sell products on this forum that compete with his products.

[Flieger]

Originally Posted by proffighter

Sometimes difficult for me to articulate and understand the tiny little things here as I am not english speaking by native (or some like that)

So I found out that the thing I meant was "warp". That behaviour is much less with sways, becaus less or no rotation around the longitudinal axis when just one wheel hits a bump, especially on higher speeds and even more on fast sustained corners (my favourites)

Anyway, nice to talk shop (is this really the word for that??) with you guys

To reduce warp you can use stiffer main springs-- or to reduce only warp you would need a special setup like used on the McLaren MP4-12C with hydraulic interconnections between the 4 corners such that when one wheel goes up the diagonally opposed wheel goes down.

Warp is not the same as one-wheel bump. Warp is like when you are powering out of a turn or trail braking into a turn. It results in two diagonally opposed wheels staying at the same height and the other two diagonally opposed wheels moving in opposite directions (up vs. down).

With a one-wheel bump situation you want to have the suspension be quite compliant so that the load on the tires is not changed too much too quickly.

Larger antiroll bars may reduce warp but so would stiffer main springs. I think antiroll bars may actually be worse in warp because they will want to force the two other wheels, that would normally be undisturbed, down and so lift the car up and increase any lateral load transfer.

[Racerbvd]

Picture of mine (powder coated, personal choice) to help with those trying to ID.