My M/S Challenger certs. to 7.50??? Only difference between 8.50 to 7.50 is a "kidney bar" and cross member within 18" of the mid plate. There may be a "butt" bar or something I'm forgetting but it has always cert. to 7.50 since 2007. I'm ready to cut this one up as well or sell the chassis and build a CM.

Is it really so? I have bended both with a manual bender, and it definitely felt like the moly needed at least the double force to bend.

That is BS, just check the actual spec manual for both 25.4 and 25.5 and it's clear that mild steel is permitted.
I know of several 7.50 cert cars constructed with 100% mild steel, some 25.4 and some 25.5, not recommending it, but it is certainly doable

If you are upgrading from a 10 point, and grudge racing, then I would recommend C/M. It will help keep additional weight to a minimum, maybe even lighter, and as stated, helps resale value.

I thought you can go 7.50 with mild steel...

I totally understand CM is the only choice for a light drag car. The funny thing to me is NASCAR are all MS. There isn't an issue with weight for them given how much they have to weigh. Still if CM were better at impact, they'd build from that, and hang weight I think.

Land Speed racing does not care for Moly either. Again, weight isn't a issue, but they feel mild steel is safer.

For a light car, CM obviously saves weight, but at what cost per lb. saved?

I buy steel by the pound.. X length per pound..
yes moly is a bit more than mild but a moly cage
is one of the easiest ways to loose weight.. and
for the cost difference it not bad.. like anything
else.. look around for pricing... I finally found
a place that has good pricing.. but I pick it up..
and I was buying 24' sticks of it

I think the main safety issue for Nascar is MS/welds are much more forgiving with multiple impact loads, something Nascar has to contend with at 200 mph speeds on a walled race track with 40? other nearby cars on the track, besides the cost and ease of repair.

Being that they have to weigh 3450 min its much
easier to get NEAR that weight.. and all the side
bars that they have.. it gets them closer to the
weight but still allows for weight to be put in
where they need added weight.. plus the fact that
they do get hit on a regular basis its easier and
cheaper to rebuild any part of the car.. I use to
fix some of the local roundy round cars near me...
some guys use to fix their cars right at the track
since its migged and could be fixed quickly

NASCAR stuff is DOM tubing, 1.75-inch diameter, .090-in. wall - usually center-less ground - not cheap stuff either. The reason I have always been told is "it has always been that way" and two it is much easier to make repairs to a twisted up chassis

As stated always best to go that way. Also mild steel is only good to 25.4 and 7.50 cert. One reason the Cuda is gone, mild steel car. Also as stated Nascar uses DOM steel, way stronger and heavier than std mild steel.

From my experience 1 5/8'' .120 wall DOM is usually very close in cost to 1 5/8" .083 Chromoly so for me that's a easy decision!

Drag racing vs. stock cars vs. land speed racing = apples, oranges and tangerines.

Both may be called "mild steel" but there is a big difference between 1010ERW and 1020DOM.

25.4 and 25.5 (8.49 to 7.50 spec) can use mild steel of the correct thickness and ASTM requirements. Why anyone would is the question. 25.1 or anything quicker than 7.50 has to be 4130 or Docol

Mild steel has it's place. A person who wants to build their own 11 or 10 second car in their home shop, on a budget, with a MIG machine, should be able to do that. Beyond that, using MS makes less sense.

Road racing specs have all but banned CM in the heavier cars because of the possibilities present in that environment. CM has a tendency to Crack and break and when the possibility of of being hit in the driver's door is high that is unacceptable. DOM absorbs more.

I bent a test 90% 120 wall dom mild steel last nite, thought I was going to have a hernia. Bent some CM later and much easier to bend, both 1 5/8. I think I'm going to invest in the hyd add on to my bender, I ain't getting any younger.

us mopar guys need chrome molly we are going for 7.50 et and faster . hahahaha

Why bother?

Increasing the diameter of the tube is more effective at increasing strength than increasing the thickness.
Design of the chassis, (proper placement of bars and use of diagonals) is the most important aspect of a safe car, not what it's made of.
Given 2 cars that are considered to be equally safe, however that is determined, I will always chose the lighter option.