Anyone using the RDR sway bar.

They have an ad in the Feb issue of GRM, on page 107.

Their bar is a 7/8" bar, (approx 22mm) and three settings. The price is 235.00.

Just curious if anyone is using it and how they like it.

John

 

Gadzuuks!! 22mm?!?! The stock bar is 16mm and the Madness and Mini-Mania bars are 19mm. I can't imagine a need for a thicker bar than 19mm unless you have a gutted race MINI...maybe not even then either though. And it's a good $50 over the Madness bar...but it has 3 settings? Hmmm...curious to see a picture of that. I've got my Madness bar on the firmer of the two settings and there is barely any room between the swar bar and the drop link...aka, there's no room to go "firmer" than what the Madness/MINI-Mania bars currently provide. This bar must have a "stock-like" setting, and then the two other settings the current bars on the market provide.

R

 

How are you liking the Madness bar? Is it solid or hollow? I'm looking into getting this soon so your thoughts are appreciated.

 

>>Gadzuuks!! 22mm?!?! The stock bar is 16mm and the Madness and Mini-Mania bars are 19mm.

...BTW, near as I can tell, the Sport+ bars on the Coopers are 17mm ...

 

the torsion stiffness is proprotional to the fouth power of the bar radius, whereas the stiffness setting differences are proportional to the lever arm length. There is a much larger stiffness difference between a 19mm and 22 mm bar than could be made up in lever arm lengths.

If they are using a hollow tube instead of a bar, it's a different situation (H-Sport uses a hollow tube)

 

I have been extremely happy with the 19mm bar. The car is well balanced, and if you went any stiffer, the car wouldn't be.

If the bar is hollow such as the one that we'll be testing soon, the effective diameter is smaller - roughly 20.5 for a 22 bar. That's still awfully big.

The H-Sport bar is the one I'll be testing, and that is hollow. Then I'll be able to supply a bar for those who want the handling, but don't want to pay a whol lot - as well as people who absolutely must have the lightest stuff available, and don't care how much it costs.

Honestly, if all you want is for the car to turn-in and handle more neutral, the Madness bar is the best investment you can make. I have one on my car and have tested it extensively. I'm very happy with it, and so are all of the customers who have one on their cars.

Hope that helps.

Randy

 

>>Gadzuuks!! 22mm?!?! The stock bar is 16mm and the Madness and Mini-Mania bars are 19mm. I can't imagine a need for a thicker bar than 19mm unless you have a gutted race MINI...maybe not even then either though. And it's a good $50 over the Madness bar...but it has 3 settings? Hmmm...curious to see a picture of that. I've got my Madness bar on the firmer of the two settings and there is barely any room between the swar bar and the drop link...aka, there's no room to go "firmer" than what the Madness/MINI-Mania bars currently provide. This bar must have a "stock-like" setting, and then the two other settings the current bars on the market provide.
>>
>>R

I am certainly a novice in this area, that is the reason for the post.

If you get Grassroots Motorsports magazine the ad for the RDR bar is on page 107 in the Feb issue. The first step on the RDR bar is 35% stiffer than stock.

I asked RDR what the next two steps are in relation to stock, and haven't gotten a reply yet. Does anyone know what the two settings for Madness bar are in relation to stock??

RDR says that most of his customers run their bar on the 2nd setting. So I am guessing, the 2nd setting is close to the firm setting for the Madness bar.

The RDR is $50.00 more, but if it gives more adjustment, particularly for those that may AutoX their cars, it might be a better choice.

 

Here's a link to some photos of the RDR bar.

http://www.mini2.com/forum/showthrea...threadid=22647

 

John,

Here's some math to ponder about the swaybar torsional stiffness.

I just measured the stock bar.

stock = 0.625" diameter
Radius = 0.3125"
stock r^4 = 0.0095

Madness = 0.750" diameter
Radius = 0.375"
Madness r^4 = 0.0198

Madness r^4
--------------- = 0.0198 / 0.0095 = 2.1
stock r^4

the moment of inertia is a function of r^4, so even though the difference in diameter is only 1/8", the result is that the MINI Madness bar is twice as stiff in bending, compared to the stock bar. That is even before you start to really take advantage of the bar's adjustability.

When the drop link is in the rearward position on the MINI Madness bar (essentially the stock geometry, but with the stiffer bar), the MINI Madness bar is approximately twice as resistant to twist as the stock bar (see calculation above), assuming both bars have the same modulus.

However, if you move the drop link to the forward position, the moment arm is cut by what appears to be about 20%. The result of just the change in geometry is a 25% increase in stiffness. Calculated by: 1/(1-.2) = 1.25

So, with the MINI Madness bar (twice the stiffness of the stock bar) at the forward position (approximately 25% stiffer than the rear setting), the result would be a 250% increase (2 X 1.25 = 2.5) in torsional stiffness compared to the stock rear sway.

So you can see that once you involve math, that 35% that RDR is claiming really needs to be quantified.

This math was done by a certified and genuine engineer - don't try this at home! Smoke starts coming out of your ears!

Randy

 

Ok Randy,

You did it! You confused the old guy. I wanted to be able to compare apples to apples, but now I have an apple and a watermelon.

So help me out here. I don't want to spend $50.00 more to get the same thing or less.

The RDR bar is 20.79mm per a dealer in them. You being the math wizz, engineer, assuming that the first position on the RDR bar is 35% stiffer than stock, can you make a comparison with that info???

Thanks,

John

 

Randy, I take that you are working under the idea that they are all made form the same material. Is it true that they are? The arm legth is also a factor, correct?

B

 

ghille:

That math up above is mine from another post. I do assume each bar is made from the materials with the same modulus. The modulus would effect the stiffness if it were different.

That said, there are two fundimental principles at work here that are important to understand.

Angle of Twist is dependent on two major factors related to geometry (as opposed to materials):

Moment of Inertia
The angle that the bar can be twisted through is related to the moment of inertia which is a function of the radius raised to fourth power. Thus if a the radius were doubled, the bar would be 16 times stiffer.

Moment Arm
In the forward position, it takes more force to induce the same amount of rotation in the bar, since the lever arm is shorter. This is why "cheater bars" work so well. They give you more leverage. In the stiff setting the MINI Madness bar would require 25% more force to induce the same twist.

Here's the catch

RDR's bar may make the car 35% more resistant to roll, but the bar itself is going to be much more than 35%. The thing is the bar is not the only component that resists roll. The spring rates are important too.

To simplify things (or further confuse them ), this is not a system where items are in series. Thus 250% stiffer bar does not make the system 250% stiffer. The suspension is more like a system of parallel, thus making the sway stiffer does make the system as a whole stiffer, but they only change the bias the system to be more dependant on the sway to resist roll, but springs are now softer in relative terms to the bar.

 

I told you guys not to try it at home

Was that smoke I saw coming from your ears John?

Dave is scary when you start him on mathematical issues. He gets this look in his eye, and an evil grin - you don't want to be a part of it.

 

[devilish laugh] Muhahahahahahahahaha [/devilish laugh]


_________________
dave@northamericanmotoring.com 300 paper cranes

 

Clear as mud guys,,,,clear as mud!!!

 

maybe this will help:

the main length of the sway bar is connected to the body; as the body rolls, this length lifts on one end and drops on the other. the bar ends are connect to the wheels and unless the wheels lift, don't change their position. the result is a twist in the bar. that's the easy part.

imagine that your bar is so stiff it cannot twist. when you corner and transfer weight to the outside wheel, that side of the body wants to drop because the center of gravity is above the ground, but because your bar is so stiff, it cannot twist, so the body cannot roll unless you lift the inside wheel. what is preventing the inside wheel from lifting is the inside wheel spring, so what you have done is used the opposite spring to assist the outside spring. the body rolls until the weight transfer equals the sum of the outside spring and inside spring compression forces.

if you had a zero stiffness bar, the amount of assistance of the inside spring would be nothing and the body would roll until the outside spring compression force equaled the weight transfer. (more compression than above=more roll)

so the in between stiffness bar actually deforms (it twists), absorbing some of the coupling force and letting the body roll some while coupling some of the inside spring force to the outside. the resulting roll stiffness is a combination of twist and spring forces

the trade off is that the stiffer the bar, the more the springs act in unison, so for straight line driving, if one wheel hits a bump, both wheels tend to react and you lose some of the independent suspension.

 

>>the trade off is that the stiffer the bar, the more the springs act in unison, so for straight line driving, if one wheel hits a bump, both wheels tend to react and you lose some of the independent suspension.

Novice alert! OK, that said, I used to race R/C cars for a number of years. When we changed to a stiffer swaybar, we used to put in softer springs to abosrb bumps better. So the above coincides with the logic used when R/C car racing. Now taking that knowledge passed down from one R/C racer to another, does this apply to full size cars, or am I on drugs with this one? Install a stiffer sway bar then need to get lighter spings?

 

jlm,

Thanks for the explaination. I do understand what a sway bar does, and you did a fine job of explaining.

All the math is what confused me......I just want a way to compare the RDR bar to Madness bar to see if there is any difference and if there is, is it worth 50.00.