Ive been doing alot of fabrication on a friends RX8 the last few months. It's already been converted to a 13b and Currently working on putting a winters quick change in a modified subframe. I have already converted the front lower a-arm to sperical bearings, modified for steering angle and boxed for strength. We are trying to eliminate some of the limitations of the factory parts. Has any one else played with suspension geometry front or rear? We moved the rack to improve bump steer and ackerman, but the rear end needs more work. I do not have a Mazda background so i am not familiar with other modified RX8's. Any help would be appreciated. I have alot more fabrication that has been done to steering if anyone has any questions.

modified A-arm


aluminum bushing that i machined and welded in to accept spherical bearing


welded in


coilover top hat also converted to spherical bearing


installed

Quick change in rear subframe... work in progress


rear subframe bushing i made to replace the sloppy mazdaspeed bushings


rear subframe, the begining of the new structure for the Winters quick change


hanging in

 

Hopefully you send those arms out to be heat treated, which will mean punching out the shock bushing. Surprised you didn't to also make it a heim or delrin instead. I was also surprised that you would use the steel shock top rather than welding or bolting a cup to an aluminum plate. You are eating up compression travel with that setup as well as not minimizing weight. Otherwise your work is nice.

 

Yes heat treating would be nice, but the balljoint is not removable so it can't be heated. All the aluminum i used to brace was 6061-0 or non heat treated so when welded it hardens to a somewhat treated level. They have seen some pretty seriuos abuse, and no problems yet.... but i agree heat treating would would great. As for using delrin... you can't do that because it has to be a bearing. That point does not just pivot up and down, it rotates at a different angle everytime you change caster. I thought of using a heim but i would have had to make a fixture to place them in the arm, with the uniball i just made a bushing and dropped it in the factory hole so it aligns itself. I used the steel top hat because they don't make a uniball housing out of aluminum so i would have had to make yet another part... and we are a Mazda sponsored team, so mazda parts are free, and we have spares of everything. Also weight is not an issue on the car, we are right at the minimum weight. I'm not eating up any bumptravel with this set up. The tires bottom out in the wheel tub with at leat 3/4'' level on the shock shaft. We actually had the opposite problem with the car not having enough droop. I used that aluminum spacer you see on the top of the hat, and the misalignment bushing to move then entire shock down and get about 1'' more droop in the car.

 

Put alittle more work in the subframe today. 4130 gussets

 

Awesome. What type of racing will this 8 be used for?

 

road racing and drifting........ and before you say it, yea drifting it a bit lame sometimes, but the car is mean. Over 500hp to the wheels, 13b, jerico 4 speed, 2500 pounds and fully built.

 

Cool, drifting is not a favorite of mine, but anything cool and fast is awesome in my book.

 

Yea, i'm a rally and roadrace guy myself. Not to mention i'm a piston fan as well, but its always fun to work on nice cars with all the good stuff inside.

 

I'm assuming you still intend to tie the lower rear subframe points back together if even with a bolt-on brace?

 

Yea, that and alot more. Rulebook says diff mounting is free, so i will use that to my advantage to brace the whole subframe. You would not belive how much a stock subframe will flex and shift underpower. The stock subframe last year would flex enough that the pinion yoke would rub with underside of the car underpower, but sitting still had at least 3/8'' gap. I also have go pro footage of at least 1/2'' bump steer per side on full bump travel.