Mazda Talk Forums

I already have chassis bracing in my car, which was a big improvement in feel. I want to stiffen up the car some more but I'm not willing to go to a cage just yet since this is my street/weekend car. There are two styles of bar for sale with potential stiffening.

Bolt in petty bar:
http://www.good-win-racing.com/Mazda-Pe ... 0412P.html

Rear supports:
http://www.good-win-racing.com/Mazda-Pe ... -0488.html

Which one will work better? Or should I just get a standard rollbar and have two "door bars" welded in to each footwell?

I can't help you with which bar stiffens more. I can tell you that the single hoop with removable struts stiffens the car quite noticeably.

AutoX photos with Hoosier A6 show what is probably close to an inch of body torque prior to the bar install. With the bar install nearly zero.
I believe the added rigidity transmitted a considerable amount of the front sway roll control to the rear which resulted the rear being considerably looser.
I have gone from the yellow RX8 front bar to the Hotchkis on the middle setting but haven't raced on it yet.

Report above is common with the rear support choices, customers often report that rear suspension suddenly much more effective and they sometimes need to make similar adjustments (less rear bar, or more front, etc). The Petty bar does not give quite as much of that, it ties bar location to the front better but effect noted above not quite as obvious in my experience.

twowheeled wrote: Rear supports:
http://www.good-win-racing.com/Mazda-Pe ... -0488.html

and what about this:

http://www.good-win-racing.com/Mazda-Pe ... -0393.html

Which one is better? Whuch one makes the chassis stiffer? Which one better in an accident?
I know hard to answer exactly, but what do you guess?

Too close to call.....both rear support models same height, same bar diameter, same supports. Thus, expect similar performance.

Brian- can you make me the single hoop with diagonal and rear supports? Or perhaps sell the single hoop with supports raw so I can take it to my welder?

Also I don't understand what you mean when you say the Hard dog will reuse the factory cross member and be less stiff? This one looks a bit better designed than the AWR with single diagonal. Correct me if I'm wrong...

http://www.good-win-racing.com/Mazda-Pe ... -0631.html

Sorry, not going to make any additional designs at this time.

Above the point of those lower supports in that design what keeps it from bending forward or back in a roll over? Answer: not near as much as you get with the AWR with supports that connect at the top. Distributing load from the low point is helpful, but not as effective. The Harddog is great for the price, it makes a smart recycled use of the factory cross brace in several versions, as explained in the directions: "If your bar does NOT have a harness bar you will need to cut the stock cross bar to fit the brackets on the roll bar. After the factory cross bar is cut attach it to the roll bar using the screws supplied. Put the cross bar in place, drill a 1/8" hole and install the screws. If your bar is equipped with a harness bar you do not need to cut the stock cross bar."