Minimum ride height/drag height?

Im driving myself nuts here. 

Trying to set the minimum ride height for my drawings for the tube frame in the amc. 

Setting on the shortest tires i plan to run. 

I know that nothing should hang lower than the edge of the rim for the case of blowing a tire so nothing digs in. 

But otherwise, what do i shoot for? Being tubes, i can set the rails/pinch welds anywhere, and optimize lca angles. 

So, what do i shoot for? 3 inches? 5? Doesn't matter cause im overthinking it as long as nothing drags on bare rims?

How much bump travel do you have/want and how much adjustment do you want on top of that?

Is this just for the front end?  I imagine you want to take the rear geometry into account as well.

The 360 had 2" at the start of the challenge.  By the end of the Autox I ran locally it had self relaxed to 1.3".   That was no enough. 

I'm resetting it to 2.5". I've heard this blown tire thing before and know some people have it in their regulations.  But it doesn't seem practical because the tire generally doesn't disappear it just goes flat.  

The MG has 3.25".  It's fine it never rubs on anything but I also don't use it to go over speed bumps.

In reply to ProDarwin :

Tear is leaf springs that will be rearched to flat, and fine tuned to height woth shackles/hangers/blocks as meeded. 

Bump travel is a good question....

Id ASSUME two inches or so based loosely on the rx8 stuff im using up front. 

Nocones: are those measurements from the lowest point? Or from framerail?

NHRA says min in front of the front axle is 3" and behind is 2" - this is so the beams work properly. I can tell you at 2.5" you can stage on the front spoiler rather easily (which is bad for times).

So, as it sits before I start cutting anything 

8 inches to the ponch weld and 5 to the lowest point of the factory subframe rails. This is on 205/70/15 tires, which are 26 inches tall. Car will be setup to run 25-27 inch tall tire range, from 15 inch wheels to 18s.

Whatever places the steering tierods flat at ride height without wicked toe changes. NHRA is 3" minimum to just beyond the back of the front wheel then 2" afterwards. That was to eliminate the potential of shortening the track length with body work vs wheel/tire.

I think my title is throwing yall off.

I meant drag as on dragging ground, not drag racing. 

Its life will be a "street" driven track car. Flat towed to events, Hillclimbs, etc

Only dragstrip is the challenge. 

Street = four inches.  Track = three inches.  There will be so many other problems that will present themselves when trying to figure this out, especially when you start pushing size limits in wheel wells.  Ideally, you'd get the engine and trans even with the bottom of the framerails (and run exhaust completely inside of them)--that would be awesome.

Why not rear of RX8 as well?

rustomatic said:

Street = four inches.  Track = three inches.  There will be so many other problems that will present themselves when trying to figure this out, especially when you start pushing size limits in wheel wells.  Ideally, you'd get the engine and trans even with the bottom of the framerails (and run exhaust completely inside of them)--that would be awesome.

Why not rear of RX8 as well?

Wheelwells are definitely going to be fabbed regardless. 

And i actually hope to be able to keep everything above rail height. Which is why im trying to figure out what that should be. Pipe dream os a flat floor the whole way back....

As far as rx8 rear goes, gearing and complexity. The thought crossed my mind more than once, but I'm sticking to a stick axle and leafs for now. 

I think I recall something in the GCR years ago about nothing dragging if both tires on one side are flat.

We set all our street cars at a minimum of 4". And these are cars that are designed to be used as daily drivers, qfter theyve been shown, so speed bumps, sloped driveways, etc are all taken into account. 

Wheelbase and overhangs  depending you may still rub, and need race ramps to get up unto a trailer, but at 4" they're perfectly streetable. 

And not having anything below the lip of the wheels rim is called scrub line. Some states will fail you on inspection if it isn't kept to, as an FYI.

Sounds like scrub line/4 inches lowest point is the way to go. 

Now, to start measuring and drawing.....

And to do that well requires more disassembly. 

As a note, scrub line they go side to side and front to back... 

And some states it's OK to have sheet metal AND exhaust cross over below the scrub line.  No hard parts  though-ie  frame, suspension / chassis related E36 M3. Like a lower shock mount, spring perch bolts, etc hanging way down.  PA for one is a HUGE stickler on that stuff. Again. Every state is different, but if you're curious the PA vehicle code spells it out pretty clearly and gives a good visual example (used to anyway)

Good example of how we do our chassis and driveline packaging. Again, 4" clearance at lowest point, which is the bottom of the frame rails in the center of car. 

Nothing hangs below the rails

 Even the mufflers are tucked up about .250" from the bottom of the rails. 

In reply to GaryC83 :

your floor has more gloss than my car