Cr-Mo vs Mild Steel Roll Bar

[nightrain]

I'm putting in a roll bar (6-pt) and am wondering why so much discussion on the Cr-Mo weight savings. I tried a quick calc assuming 40' of material (1-3/4" O.D.). Using DOM steel tube of .125" thick and Cr-Mo at .083" the difference in 40' of material is 28lbs. A 3650lb car needs about 550 RWHP to run high 10's. If I assume a 10.95 ET at 3650lbs, adding 28lbs to the car slows it down to 10.98 (using simple 1/4 mile ET calculators).

For example, a Cr-Mo bar kit costs $410 from Morrison, but the DOM steel kit is $205 (8-pt prices). Is .03' ET really worth the extra $$$? Is just thinking it's lighter making people feel better about Cr-Mo? I can understand if people are concerned about the extra strength, but I see more forum traffic about the weight than strength. Just curious before I buy materials. Thanks!

 

[Eticket]

I never thought Chromoly was much weight savings, never weighed them either.

I'd rather have chromoly, but it really up to who's doing the welding. You should tig chromoly and can mig steel just fine.

 

[steve hughes]

To be nhra legal chromemoly must be tig welded.

 

[pacecarta]

cm comes out roughly 1/3 less weight than mild

for $200 youve shed about 30lbs

try shedding 30 from somewhere else on the car and see how much it wil cost you , i did once and its about $100 per 10lbs when substituting a lighter part (not counting frt bumper bcause that usually already done when going to a roll bar

thats also 30 lbs you dont have to loose so you can order the desert

on a full cage its about 50lbs saved going CM

 

[kingots2004]

you also gotta at in the extra time it takes to tig. so it costs more to have the cage installed as well

 

[thrlskr]

Chrome Moly was the same price as mild steel at the chassis shop I used. The cost for the steel is roughly the same and some guys are better/faster with TIG.

 

[qwksht]

I used chromoly in my car as well,like pacecarta said,there is a nice weight savings if you choose chromoly over mild steel...plus the tig welds look awesome!!!

 

[1of1547]

I talked to my local my chassis guy about which one to buy when I bought mine He basically told me that for a weekend warrior he would recommend a MS. Normally The extra cost of the kit and installation really doesn't warrant the the need. If you are racing on a regular basis or planning on stepping up to a 25 series car then he recommend the CM.

 

[GARY HARVEY]

Cm

End up with a safer (stronger) and lighter cage.
Damn the expense, peace of mind is worth it.

 

[gnsrule]

Chrome Moly # .083 is the same strength as Mild steel @ .133 Forgive me if im off on the thickness's. Your paying for weight gain, not strength. C/M will tweak and stay tweaked whereas MS is more forgiveing and flex back to shape. Chassis guys sometimes prefer CM because its easier to notch being thinner, takes more time to weld tho. I went CM on the 86 GN because thats what the chassie guy wanted to do and the tig welding is better IMO. The Camaro is CM cuz that what it takes for a 6.0 cert.

Craig

 

[Louie L.]

A CM cage is not safer. CM will break when pushed past its bending point. What you end up with is sharp edges to promote further injury. MS will not act this way.

 

[odell4o8]

A CM cage is not safer. CM will break when pushed past its bending point. What you end up with is sharp edges to promote further injury. MS will not act this way.

My regal that i crashed at bg, had a mild steel cage 1 3/4 od, it bowed or bent in a few places, only one weld cracked half way, it was welded with a wire welder by my son, the nhra inspector come to my house and looked at the car, he said the cage or roll bar did a dreat job procteing my a$$,
my new old car has mixture cm and mild steel[could explain it would take too long,] see you at bg,
oc,

 

[GARY HARVEY]

Whomever your sanctioning body (is), determines the material. Locally (Div 5) CM is the ticket to get on the track with the chassis's being built in this area and the last time we had this discussion, the NHRA "inspector" trumped everyone's opinion.

 

[gnsrule]

Whomever your sanctioning body (is), determines the material. Locally (Div 5) CM is the ticket to get on the track with the chassis's being built in this area and the last time we had this discussion, the NHRA "inspector" trumped everyone's opinion.

SFI specifications dictate what material to use. It IS printed in black and white and IS cut and dry. No opinions wanted, suggested or allowed.

Craig

 

[1of1547]

SFI specifications dictate what material to use. It IS printed in black and white and IS cut and dry. No opinions wanted, suggested or allowed.

Craig

25.4 and 25.5 cars can be mild steel and mig welded. And they are good down to 7.50.

 

[gnsrule]

Yea, I know. My 68 Camaro was a mild steel, but my chassie guy preferred to tig weld it. Ok by me. It was a 25.4. All CM must be tig welded tho. The 98 Camaro is 25.1E,tig welded CM mandetory, 6.0 cert.

Craig