"Drilling" factory sway bar.
 

I recall reading a few posts concerning the possibility of redrilling the factory sway bar for slightly stiffer settings. I would like to try this to experiment with stiffer sways as opposed to buying a new set up and perhaps not liking the end result.

Can anybody provide some insight on the outcome and process?

I haven't done this myself, but all you are doing is reducing the moment arm (lever length) of the bar. The change in stiffness will be the ratio of the original lever length divided by the new length.

I even remember seeing a post by Team RX8 where the tip of the bar was put in a press to increase the flat area in order to reduce the lever length even more.

Found it:

https://www.rx8club.com/rx-8-racing-...-139848/page2/

I've done it to the rear and might do it to the front for some more flexibility. I never bothered to calculate the effect (you can't just look at the bar stiffness % change, need to include springs, motion ratios, and roll center) but it was one thing I did to turn a very pushy car to slightly loose.

Very easy and worthwhile mod. Be careful with the chassis-side studs. All of mine snapped so I replaced them with bolts/nuts.

I stated that the change in stiffness for the bar is related to the lever arm lenth change, which is accurate (assuming same size bar OD/ID). I wasn't talking about oversteer/understeer ratio with takes into account the front and rear roll stiffness (which is a combined stiffness of anti-sway bars, springs, and chassis rigidity). The percent change in stiffness that I am talking about is just for the bar. Changing the hole location for the factory bar will only have about a 15%-20% change in bar stiffness. Not saying that it isn't noticeable, but it is a very small change in comparison to almost all aftermarket bars. For example, the Racing Beat anti-sways have a 117% increase in stiffness for the front and a 166% increase in stiffness for the rear.

maybe thats all thats needed? When i was speaking to NYC DriftKing, he said he returned to stock bars because the back end of the car would keep kicking out while doing mountain runs.

i dont know, that was what he said, just providing some input here.

That may have been true for his setup, but you can't make that generalization across the board for everyone. When talking about oversteer/understeer ratio, there are many things that will cause an effect (tires, staggered wheels, front/rear spring stiffness, front/rear anti-sway bar stiffness, alignment, etc.). Without knowing NYC's setup, that statement shouldn't be made.


If you like the way the car currently drives/handles (regarding oversteer/understeer ratio), then keep the front to rear roll stiffness ratio the same. If you want more understeer then increase front roll stiffness or decrease rear stiffness. Opposite if you want to increase oversteer.

Just remember that too much roll stiffness compared to vertical spring stiffness will cause you to lift a wheel in a hard corner. 4 tires will always get better traction than 3. Increasing roll stiffness (via anti-sway bars), without increasing spring stiffness, should be considered carefully.

^Exactly. Omar is just a crazy driver :lol:

With my setup (Stance coilovers, Progress Tech sways, and same rim and tire size all the way around), car is planted and actually understeers a bit which is most likely due to my rear sway on full soft rather than full stiff.

So it depends on your setup and you're driving style.

Yes, driving style and personnel preference also has a lot to do with it.

This brings back memory of introduction to engineering dynamics/statics :rofl: . Would love to see a stock bar in SolidWorks with new hole locations.

Thanks for the provided link. I should have searched harder.

I only meant to say that I never bothered to calculate the total stiffness effect. For all I know, the roll stiffness distribution could have moved <<1%. You are correct and you mentioned the chassis stiffness, which I failed to include in my statement.

just giving someones point of view on swaybars, not applying to everyone of course :)

No worries, I hope I didn't come off as demeaning. That wasn't my intention.

I can provide a custom modified one if you're interested. I flattened the tubular end some more in a brake press and then installed two sets of stiffer end link position holes with a drill press. Most people do it redneck style with a hand drill and that looks close enough eye ball approach ...

I got access to a brake press and a drill press. Shouldn't be too hard to do. Thanks for the offer though.

Hey, I resemble that comment.

Has anyone applied this to the R3 sway bars?

Resemble? Resent perhaps?

you're definitely an engineer.

I haven't applied this to any RX-8 (have aftermarket anti sways), and I don't even own a R3 (wish I did though), but you should be able to drill the second hole. However, I do not think you can flatten the end of the bar since it is filled with urethane.

Your head is more likely filled with urethane than the swaybar

I eyeballed it with a drill press...you could even do it on the car if you're lazy. Just remember to put the endlink in the new hole when you're done.

Not recommended based on personal experience :wallbash:, but taking the thing off the car is no fun at all, so if you're going to bother, I'd recommend spending a few bucks to get the bar you want.

It's easy if you drop the lower radiator brackets and drop it out the bottom rather than fish it out the side, though I won't admit how many times I did it the wrong way ...

I drilled mine on the car with a hand drill. It's a good free mod but ultimately I bought stiffer adjustable bars.