RB Front bar fitted

adamjp · Postby **adamjp** » Sat Jun 02, 2007 11:05 am

Some comparison photographs for those who wonder just how much thicker this bar really is.

Superimposed, RB over stock

Difference in Bushes

Unsurprisingly, the handling is much flatter.

StanTheMan · Postby **StanTheMan** » Sat Jun 02, 2007 11:25 am

OMG

are you getting any feedback at all?

thats seriously phat
is the original 19mm?

Brad · Postby **Brad** » Sat Jun 02, 2007 11:45 am

Picking mine up from Kula in a few hours, hopefully have it fitted tomorrow. Any special fitting advice?

adamjp · Postby **adamjp** » Sat Jun 02, 2007 11:54 am

OE is 19.12mm dia. The RB bar is more like 28.5mm.

For fitment, follow the instructions, they are quite good.

I found that the trick was to remove passenger side rubber, rotate the bar so the ends were straight down, slide the old bar out towards the drivers side and take care maneuvering the passenger end through the space between the rad fans and the block.

My AC piping was a PITA, but once you get to that, you can rotate the long section of the bar towards the front of the car and the passenger short end just kinda drops out. You have to do it to understand.

Fitting the new bar is the reverse of removing the old one, but greasier.

I used half the tube of goo on each bush. The easy way to get the goo out is to cut the end off the tube, just downstream of where it starts to narrow into the nozzle. Then insert the tube halfway into the opening (mouth) on the bush, and close the bush onto the tube. Then pull the tube out and watch the goo get squirted onto the inside of the bush. Very cathartic. Spread liberally with your pinkie so all surfaces are covered.

Rob E · Postby **Rob E** » Sat Jun 02, 2007 11:58 am

StanTheMan wrote:OMG

are you getting any feedback at all?

thats seriously phat
is the original 19mm?

Stan - these are hollow bars.....nothing like a 28mm solid!!

StanTheMan · Postby **StanTheMan** » Sat Jun 02, 2007 12:08 pm

right ....OK :lol:

adamjp · Postby **adamjp** » Sat Jun 02, 2007 1:43 pm

Stan - these are hollow bars.....nothing like a 28mm solid!!

Not so,

being hollow does not significantly reduce their mechanical effect, it simply reduces the weight. The stock bar weighs 6lb, the RB tubular weighs 5.5lb. A 28mm solid bar would weigh around 14lbs.

Since a sway bar is essentially a torsion spring, it works on the resistance of the bar to twisting. The amount of resistance to twisting is governed by the diameter of the bar, and the effectiveness of that resistance increases the closer you get to the outer edge of the bar circumference.

Think long spanner compared to short spanner.

This is wrapped up by the area moment of inertia, or second moment of area.
I = (piDxDxDxDxD)/64

And can also be expressed as the polar moment of inertia.
J = (piDxDxDxDxD)/32

Which boils down to the larger the diameter, the more inertia. If you run a comparison from 0 to 28mm, you will see that at 14mm, I is 1885, at 28mm, I is 30,171. This is 16 times more resistance. Thus the inner 50% of a torsion bar does almost nothing compared to the effect of the outer 50%.

To get the total resistance of the bar, you seek the area under the curve from 0 to 28 for a solid bar and the inner dia to the outer dia for a hollow bar. For 0-28mm, a comparitive total is 184407, for 14-28mm 180025. So for not including the inner 14mm, you get 97% of the strength.

This is why when you go up in sway bar size, the effect of a 1mm increase is a substantially larger increase in stiffness.

After regurgitating that series of basic mechanical engineering from deep in my brain, i am off for a LLD (little lie down).

Rob E · Postby **Rob E** » Sat Jun 02, 2007 2:59 pm

Yep, referring the the weight......feel is a lot better than the 25mm solid i had in a previous life.

StanTheMan · Postby **StanTheMan** » Sat Jun 02, 2007 3:33 pm

so these little babys are serious torsion bars.......whats the feedback like driving on the twisties.....Or i'd imagine these would be very suitable for the track more so than road use.?
Comment?

Rob E · Postby **Rob E** » Sat Jun 02, 2007 7:42 pm

Stan, just went for a blat, my set up is Tein Basic 7kg front , 6kg rear RB Hollow front bar, NB Mounts, and cusco front and cannon rear braces. Now i undestand why the yanks rave about this set up.This set up is freakin awesome to say the least.

A huge difference to the eibach/kings and koni set ups i am used to. Not sure what a bar of this size would be like with less spring rate (eg King or Eibach) however. The bar hasnt dulled the steering feel or feedback at all.......i do have PS though. I know exactly what you are concerned about though because on my last MX5 it came with a 25mm FM front bar and that was a real dud (i went back to stock sways to bring back the feel)

adamjp · Postby **adamjp** » Sat Jun 02, 2007 8:08 pm

I am Konis with Eibachs and the main differences are that the steering is lighter just off centre. But as you wind in lock, it loads up nicely.

No heavy, deadening, of the steering response. Happy so far.