Originally Posted by
Designmindz
I'm about to pull the trigger on a steel bike (when the damn bike shop opens again), so as long as its 4130 I'm good, right? I mean is there different grades of 4130 etc?
I'm looking at Marin Muirwoods with a lifetime warranty on the frame.
4130 refers to a joint SAE/AISI standard (that is, SAE AISI 4130) which is also is referred to under the SAE's Unified Numbering System as UNS41300. Steels specified as 4130 should all conform to the standards for chemical makeup and physical properties. I'm sure, though, that different steel manufacturing and tube drawing plants have differing quality levels. It used to be that is a European, Japanese, or Americal mill went to the trouble of making such a high-strength alloy, they'd usually do it right. Today, we seem to have a race to the bottom in terms of price, which likely leads to lower quality.
So, all 4130 should meet a minimum standard which is much better than low alloy carbon steel. Some companies make a superior quality (more uniform, better tube drawing, better swaging processes for makeing butted tubes) product.
Steel has an interesting property. It's modulus of elasticity (springiness) is the same for almost all varieties of steel. Two tubes of identical thickness will flex almost exactly the same. Cheaply-made 4130 and a premium brand? Same flexiness. 4130 and 853? Ditto. For low end bikes of generic 4130, you probably get a bit thicker tube. This addresses issues like nonuniformity in alloy, and in poorly drawn tubing. That bike will ride a bit more stiffly than a bike where the mfr. trusts and takes advantage of the specified strength of the steel, and has used thinner wall tubing as/where appropriate. This should give you a strong frame that has a bit better ride. And tubing like 853, which has a higher tensile and yield strength, can be made even thinner if needed.
There's a huge variability in fabrication quality as well. I suspect that most (maybe not all) companies that are using a higher quality "Name Brand" tubeset (IIRC, Reynolds 525 and 725?, Trek CRMO) do higher quality welding/brazing/heat treatment.
So yes, all 4130 meets the same basic requirements. Differing levels of quality in metallurgy, tube drawing and swaging, and fabrication will likely make for differing levels of durability, comfort, responsiveness and weight.
Sorry to answer with a "it depends". But it does depend on other factors.
I went the same route as CAT7RDR and bought an old Lemond 853 frame.
On edit, I wanted to say that DMC707's note was very interesting. "A&P" means that he's a rated Airframe and Powerplant mechanic. That is the government lets him work on airplanes. That's good enough qualification for me. I found his comments useful/informative.