Swaybar stiffness comparisons to stock ITR rear (22mm)

+17% - Whiteline (24mm - soft)
+19% - JDM ITR (23mm)
+42% - Mugen (24mm)
+74% - Whiteline (24mm - stiff)
+95% - Mugen (26mm)

Takeaways
The Mugen 26mm was the clear winner, being the stiffest of all, almost 100% stiffer than stock. The Whiteline was slightly off the Mugen.

Going a step further and evaluating wheel rates, I determined the difference in rear spring rate required for say the Whiteline (full stiff) to equal that of the Mugen 26mm was <60lbs. So for a racer on a budget, running a touch more spring on the rear with the Whiteline can be an economical alternative match the stiffness of the Mugen 26mm. Hopefully someone will find this as interesting as I did

Method
I saw a posting for calculating sway bar rates on the Evolution Forums (Yahoo Groups). So I used the template, went out and made the measurements on my ITR, OEM rear bar, and Whiteline (2 position) bar to come up with the following results. I estimated the Mugen saying it's configuring (shape) mirrored the stock bar, only the diameter was greater. Plotted the bar stiffness/wheel rates and determined % differences from stock.

 

Interesting. So explain to the newb, how stiffness of the sway bar affects performance.

 

To say the Mugen bar is 95% stiffer than OEM...wouldn't the Mugen bar then have to be twice as thick? Also the alternative you posted for a racer on a budget...it may equal the same % as you figured but the geometry would be completely different.

 

95% stiffer than the stock rear sway bar? i find it hard to believe. check ur caluculations!

 

From what I have found you have to take in account:
1) Sway bar rate
2) Center width
3) Length
4) Arm Length
5) Wire O.D.
6) Tube I.D.

 

thanks for the info!

p.s. - his calculations are absolutely correct. the "stiffness" is directly related to the diameter to the 4th power.

example:
% increase in "stiffness" = (larger bar diameter/smaller bar diameter)^4

mugen 26mm
oem itr 22mm

(26/22)^4 = 1.95xxx --> 95% increase

the calculation will get a little more hairy when analyzing a hollow bar such as the whiteline.

kepani

 

Wow, this information is exceptionally helpful. But I heard the Mugen 26mm has be discontinued.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RisforTypeR &raquo;</TD></TR><TR><TD CLASS="quote">Interesting. So explain to the newb, how stiffness of the sway bar affects performance.</TD></TR></TABLE>

To put it in overly simple terms: stiffer rear bar/rear springs will increase the tendency of the car to oversteer.

 

can putting a Mugen 26mm rear sway bar on an ITR do damage to the rear subframe overtime?

 

Not that I've ever heard of. The ITR subframe is a pretty stout design, not so cheesy like the EGs.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RisforTypeR &raquo;</TD></TR><TR><TD CLASS="quote">Wow, this information is exceptionally helpful. But I heard the Mugen 26mm has be discontinued. </TD></TR></TABLE>

Yes it has. If you find one get one for me too

Great post BTW

 

How badly do you guys want one?
Won't consider bids below $500.

BTW -- I've got a front 26mm Mugen bar to go with that as well (above price would be for the rear only, front is extra).

 

Remember, you just don't want to slap on a big bar for oversteer. There are many factors in tuning the car for your liking. I like the idea of keeping the suspension as independent as possible. Therefore, in my car setup, I am running a JDM bar and higher spring rates (about 900 to 1000lbs in the rear...obviously a track only car) in the rear. Therefore, if the right rear wheel hits something it doesn't affect the left wheel. A sway bar basically connects the suspension together.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haleiwa-Brando &raquo;</TD></TR><TR><TD CLASS="quote">To say the Mugen bar is 95% stiffer than OEM...wouldn't the Mugen bar then have to be twice as thick?
</TD></TR></TABLE>

No.

(thicker bar diameter) ^4 / (thinner bar diameter) ^4.... or the way Jay put it above is right also (didn't see it when i posted)

The mugen, jdm, and usdm are the same shape and very similar material.

As for the whiteline, no idea b/c its solid.

Chris - who questions the 'clear winner' statement of the 26mm mugen sway bar - the best bar is determined by the setup.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TypeRlove &raquo;</TD></TR><TR><TD CLASS="quote">95% stiffer than the stock rear sway bar? i find it hard to believe. check ur caluculations!</TD></TR></TABLE>

Check yours! Or did you do any?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haleiwa-Brando &raquo;</TD></TR><TR><TD CLASS="quote">From what I have found you have to take in account:
1) Sway bar rate
2) Center width
3) Length
4) Arm Length
5) Wire O.D.
6) Tube I.D.</TD></TR></TABLE>

What do you mean by 'found' ?

 

This is exactly how I calculated it. The template I mentioned has all these measurements you need to plug in. I spent a fair amount of time collecting them all to create the above results.

And there was a reference to the Whiteline being hollow. It's not, I've got one, definitely heavier than the OE bar. It differs from stock because the of mounting location. The arm lengths (#4) are 1/2" shorter than stock in stiff and 1/2" longer than stock in soft

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haleiwa-Brando &raquo;</TD></TR><TR><TD CLASS="quote">From what I have found you have to take in account:
1) Sway bar rate
2) Center width
3) Length
4) Arm Length
5) Wire O.D.
6) Tube I.D.</TD></TR></TABLE>

 

If you want more oversteer, a bigger rear bar on the stock suspension is not the way to rumble. I tried the 25.5mm (ground-control) rear bar (granted it was a tight course - summit shenandoah) and it was not the answer. The inside rear tire picked up right after corner entry and hung there till a bit past apex, effectively making the bar useless.

The bar is just one part of the puzzle for suspension tuning. But you really need to up the spring rates.

 

Does that mean that my new JDM rear bar will be 979% stiffer than my current 13mm LS rear bar?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by typer_801 &raquo;</TD></TR><TR><TD CLASS="quote">Swaybar stiffness comparisons to stock ITR rear (22mm)

+17% - Whiteline (24mm - soft)
+19% - JDM ITR (23mm)
+42% - Mugen (24mm)
+74% - Whiteline (24mm - stiff)
+95% - Mugen (26mm)
</TD></TR></TABLE>

are all these bars made of the same material? otherwise your calculations may be way off...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by igyloo &raquo;</TD></TR><TR><TD CLASS="quote">

are all these bars made of the same material? otherwise your calculations may be way off...</TD></TR></TABLE>

Its a safe assumption that they are all mild steel.

 

This post is cool. Thanks for doing all the foot (brain) work for everone

If you want, you should post your formula for everyone to use.

 

This isn't the first or tenth time this has been discussed on here...

The formula is (as stated above)
(23/22)^4 = 1.19xxxxxx

I'm just wondering where the whiteline %'ages came from, would be nice to know. I vaguely remember seeing some info on the bar's stiffness on their site a while back.

 

They came from me! I physically took all the measurements of the Whiteline bar, along with those of my stock ITR rear bar.

I then plugged the results into the swaybar rate calculator (as I explained earlier) and the effective sway bar and wheel rates plopped out. For simplicity sake I just did % differences from stock instead of showing everyone all of the rates and making this more complex than it really is.

fwiw-the Whiteline measurements are not much different from the ITR bar expect the center width is slightly smaller and the arm lengths are different (because it's adjustable), and of course the diameter.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris N &raquo;</TD></TR><TR><TD CLASS="quote">This isn't the first or tenth time this has been discussed on here...

The formula is (as stated above)
(23/22)^4 = 1.19xxxxxx

I'm just wondering where the whiteline %'ages came from, would be nice to know. I vaguely remember seeing some info on the bar's stiffness on their site a while back.</TD></TR></TABLE>

 

Ah... cool. I was unaware that they had a calc on there.

I only knew the (x/y)^4 calculation.