Here is a decent guide showing some measurements - http://www.bethania-garage.com/guide.htm
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I know there are, figuratively, a million threads on roll bars and clearance. However, I think it'd help to see it in person.
I have an NA with a Kirkey sitting on the floor (it does have around an inch of padding so I could get a little lower). With a hardtop, putting the bar as high and far back as possible would put the bar directly overhead which seems far from ideal. This is 2-3 inches in front of the back glass, rearward of this the top slopes down pretty quickly which would make the bar too low. The seat back is more or less lined up with the front edge of the back glass. So, even if I do remove the seat padding, the bar will still be directly overhead. To avoid that I'd have to move the bar back which would put it directly under the glass, and too low. I could move the seat forward a bunch but I'd rather not be that uncomfortable. The seat does have a modest amount of 'layback' which helps in dealing with an old back injury. I'm not sure I could stand it up enough to make a difference anyway.
I can't see how this will work and still have a top, that's why I'm hoping someone here has something that works that can be copied. Anyone have such a setup I could check out? I'm planning on going the custom roll bar route, but I'd be happy to see any solution, off the shelf or otherwise.
Here is a decent guide showing some measurements - http://www.bethania-garage.com/guide.htm
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At 6', you shouldn't need the seat that far back unless you're just trying to be more comfortable in daily driving. A good driving position for track/autox is fairly upright, elbows bent (steering wheel close enough to rest your forearms on the top just behind the wrist without stretching), and the left foot able to brace yourself against the dead pedal without straightening your leg. I'm 5'10" with very long arms, and I have several inches behind the seat when in proper driving position.
The risk of a head injury from roll bar contact in street accidents should be your foremost concern, much more than track rollovers. I'd advise you to position the seat so that head-to-rollbar contact is not possible. A shorter than ideal rollbar is still a life-saver on the track, as it prevents the car from collapsing on you. If you are taller, you can run a 3 point belt or a harness with loose-fitting shoulder straps to avoid being suspended upside down in a way that puts your head at risk (you need to be able to duck or lean sideways if your rollbar isn't tall enough to guarantee zero helmet-to-ground contact.
I've seen a few customized roll bars that have a bolt-on upper hoop that extends the roll bar height when the top is removed, which might be worth looking into if you are that concerned. Again, at 6', you shouldn't need to go to those extremes to have a road/track-safe setup.
Polished Turd Racing
Mick wrote: "I think Jerrett is the best autocrosser I have ever seen naked."
Thanks for the link. Don't know how I missed that all this time. I can mock those measurements up and see what that'll get me.
The car gets driven on the street primarily to the track. Maybe once or twice a year on the street farting around for thirty minutes or so. It doesn't get driven much at all street or track. My primary focus is on the track. My wheel position was not good but I moved it back several inches and now it's pretty nice. I'll have to double check the dead pedal but since my clutch requires the pedal to be fully depressed to disengage, and I can do that without locking my knee, I should be good on that.
I appreciate the pointers. I know I don't want my head hitting a roll bar, especially helmetless. That's why I'm looking to find someone with a setup that works for them at a similar height that I could have a sit in and see how it fits and feels.
Some high-quality roll bar padding could allow you to bring the bar a bit closer to the head safely. Since you are not DD the car, the risk of hitting a helmetless head is much lower.
Polished Turd Racing
Mick wrote: "I think Jerrett is the best autocrosser I have ever seen naked."