One of the best collections/discussions on cage design I've seen, including X-bar/NASCAR hybrid doorbars:
http://roadraceautox.com/showthread....highlight=cage

In the SE those porsches run in SPO. SPO is more heavily attended than SPU since that is the "catch all" for all the pro series sports cars, along with the PCA and BMW club cars etc.

U vs. O has to do with maximum displacement, right? I don't know where the cutoff is, but I thought SPU was under 2.0L (or whatever), and SPO was over 2.0L?

Yes, but boost is an automatic bump up to O. I think the cutoff is 2.0L. Also rotaries have a multiplier. When I ran my GrandAm Cup Miata with the SCCA I ran in SPU, but that was the same class World Challenge cars ran in - which were making ~100hp more than my Miata. I believe that most SP rules specify the car must be a fendered, production based car (since it is a Production class). That would keep out the formula cars and prototypes- but not things like x-stock cars, which run in the class here often.

Ah, I forgot about boost changing that. For sure in those more open classes the cars are not as evenly matched. GrandAm Cup Miata, when was that around? Built motors, or relatively stock?

More pictures of your GrandAm Cup Miata please. And what power level did you have?

Bob

Correct. But in Bob's case he can build the car for the class. IMO it seems like a good challenge given his fab/engineering skills and driving experience. The Miata will show up as the underdog no matter the driver or the build in SPO. ;)

Hate to disappoint but it wasn't too much more than Spec Miata. Engine mods allowed were spec'd cams (aka sunbelt cams), a retro fit of the Mazda Comp Production valve train, deck head/block to get 10:1 static compression and a header that one of Bosal/Brospeed's fabricators custom built. That with a crank triggered LINK stand-alone got us 155whp. Don't have any real build photos- spent every available moment doing something to/on the car.
https://www.miataturbo.net/attachmen...ine=1316624143
https://www.miataturbo.net/attachmen...ine=1316624143

There's me knocking lightyear's bent-type door bars, when that's what's used in current WRC: https://www.miataturbo.net/attachmen...ine=1316631625

Although I still think (goddammit!) that the bend at the rear of the uppermost bar in lightyear's cage can't be good for anything except for a way to dissipate front-impact energy.
Overall though, sorry for knocking your bent bar design, when clearly it must be the best solution.

Thats what I've been saying! Those cars are bigger though and have more room for your elbows. I"m really curious what its like having X door bars in a miata.

Another cool concept (though it wouldn't fly in the US) is this WRC greenhouse design that they talk about in the thread stinkycheezemonkey posted earlier.

https://www.miataturbo.net/attachmen...ine=1316631934

It's funny how this newest kind of WRC cage wouldn't hold up in the US (due to the lack of a main hoop, right?) as mentioned in that thread, even though they can stand being rolled off a mountain, ha.

Actually upon further research the WRC cages are back to using a main hoop now. Drivers were having to retire their cars due to roll cage damage too frequently with that design and one driver died (not sure if it ended up being related to the cage or not).

I just got pwned again. I'd better stay out of this thread, huh :P

Actually, a lot of those WRC cages are FIA-certified, which will pass in a lot of US-sanctioned organizations. The trick with that is it has to be EXACTLY to FIA specification, and may or may not need an FIA stamp (don't remember on that last bit). You see this with some imported race cars. The design isn't necessarily inferior (the lack of a main hoop I mean), just a different take. From a practical standpoint, if you're in the US stick to US-spec cages with respect to main hoop stuff.

Ok, well here is what I have been thinking. I dont want to take the car off the street but the speeds I have at the track are concerning and I want to stiffen the car. I still want to get in and out of the car on a daily basis so I am thinking of having that upper door bar removable.

Attachment 25862

The thought is to cut out the seat belt towers and use that area for the hoop giving me more room for the sholder support on these style seats and letting me push the seat all the way to the rear.

Attachment 25863

IF you could do it, I would think it would be extremely cramped. I certainly wouldnt want to test my luck with a side impact crash and x-bars.

I think a removable steering wheel is a necessity in order to get in and out with X-door-bars, even then... well lets just say I'm glad I don't dd mine. Getting in and out of an exige everyday is about the same thing imo.

This is a timely thread. Another winter cage build going on here and I'm looking at the alternatives.

X Bars are still pretty common with the TT crowd here in the Northeast. I have the Hard Dog roll bar/door bars in mine now, and they run just under the edge of my seat (RaceTech 4009W). I could live with a similar setup on the cage. Rollover protection is my top priority though, and I'll go through the X bar/mini/maxi NASCAR bar discussion with the builder. Ideal setup will have better legroom and headroom than afforded by the HDHCDD setup in there now, while adding A pillar support.

Savington - thanks for posting the earlier cage thread. Those TC Design pics will be very helpful.

I forwarded the snowboarder cage pics over to my local builder to start the process. He's done a lot of SM cages but mine will be a little different. Like the original poster in that thread, I'll still be street driving to the track for at least another year and need those photos for ammo when he wants to go all NASCAR on me.

My cage will be a bit different as I intend it to be integrated into a simi Tube frame conversion of the chassis. Not allowed in ST, IT, or Spec Miata Classes. Much of the existing structure in the Unibody will be gone. car will be prepared to the limit of the XP autocross rules to the best of my ability and I hope to be near the minimum 1760 lb limit for a boosted 2.0l while still retaining a windshield and also meeting road race rules for SPO which is basically a GT car. Problem is the only way a Miata can run in a GT class is to drop a rotory in it and it would more likely be a full tube frame.


Example GT3 miata full tube frame.
http://www.pennon.com/products/bodyw...zda/Mazda.html

Bob

A bit off-topic, but if you are going custom, I like some of the things these guys did:


http://carpentermotorsports.com/gall...serialNumber=2

http://carpentermotorsports.com/gall...serialNumber=2

http://web.archive.org/web/201110052...4c5ece2e7ff024

http://web.archive.org/web/201110052...4c5ece2e7ff024