Tried doing a search but couldn't find much beyond "631 is better". I'd like to know why.

higher tensile strength = less material, same strength.

more significantly, 'air hardening'...which is a not exactly obvious term for 'welded areas are stronger'. the intense heat of TIG welding weakens standard chromoly, making it more brittle and likely to crack in the heat affected area. even seen a frame fail mid-tube? it's always near a joint. according to reynolds, the alloy used in 631 is actually strengthened by the welding process.

Reynolds 631 tubing is lighter and stronger than 4130 CrMo tubing. While 4130 is a generic categorization of steel meeting a certain range of alloy requirements, 631 is a specific formulation and process to Reynolds.

hmm this is an interesting thread. What about other kinds of steel? Columbus? Reynolds 531? What about Tange Prestige? i have always wondered about this and just assumed that the nicer/more expensive steel was lighter and stronger, but I was never sure. I have an old, '88 Bianchi. I assume it's made w/ Columbus steel, how is that stuff?

While the alloy composition of many expensive tubing sets is stronger on a per ounce basis, the issue of durability (against abuse) has to do with more than just composition and tempering.

Reynolds 531 is a weaker alloy than 853 or 953. The durability issue that comes into play is the draw of the tubing. 531 tubes are thicker walled than 853/953. You're less likely to dent a 531 or even 4130 frame by leaning it hard against a railing than if you did the same with a bike built with 953 tubing because of how thin the draw of 953 is.

While a 953 bike is going to be light and strong and unlikely to suffer damage during routine riding, it's not designed to take the punishment that say, a courier bike will get from consistent harsh lockups.

(I don't know comparisons between brands, so I can't help ya with Tange and Columbus tube sets.)

This seems like it would be a good thread. So youre saying that even the the higher quality metals would be lighter and stronger, it'll be easier to dent because the tubing is thinner? So what if I choose to make the tubing oversized? Would it compensate and still be lighter?

We tend to assign value to the various bicycle tubing steels on the basis of strength to weight ratio and price.

We think of expensive as better.

However, all of the grades of steel tubing have virtues that make them desireable in a bike, depending on the purpose of the bike.

Some years ago I corresponded with someone at Mercian Cycles, and he (or she) told me to not think of the frame as a place to save weight, but, rather, as a place to fine tune ride, handling, and other factors, such as longevity.

Modern 4130 makes a great frame when chosen by a quality frame fabricator.

Surly has all of its frames made out of 4130 by some big Southeast Asian frame builder, and I don't think a better frame exists in that price range.

Bianchi makes a few frames, still, out of 631, and Bianchi makes the Pista out of Reynolds 520.

Or, I should say, Bianchi pays someone to make frames out of these steels.

The Pista has very sophisticated tubing and, until this year, very sophisticated geometry.

Reynolds 520 served well in this application, producing a very tough and resiliant frame that works well on the "mean streets."

Reynolds 631 represents the toughest air-hardening steel Reynolds makes, even though it has a low strength to weight ratio.

Despite its low strength to weight ratio, 631 has other qualities that enable it to take huge amounts of repeated abuse, and it often gets used outside of the main triangle to "tune" the ride.

A frame made out of a combination of 853 and 631 would make a lot of sense in certain applications.

If I planned a long tour in a location where I could not expect much support, I would choose a frame made out of 4130 or 631 over a high strength to weight ratio steel such as 853; or, I might still choose 853 for the main triangle but specify heavy tubes (tubes in a given steel come in various thicknesses, weights and shapes) for their extra strength and not for their strength to weight ratio.

I have a custom frame on order from Realm Cycles, and Warren has suggested a main triangle of True Temper Ox Plat (which corresponds to Reynolds 853), not to save weight but to add strength (I weigh 225lbs).

He has told me to expect this frame to weigh as much as, or only slightly less than, the frame on my Bianchi Pista.

Reynolds 631 and 4130 make good frames, regardless of weight.

UBI in Ashland Oregon uses Kaisei CrMo 4130 as their primary steel; the same tubing used by the most prestigious Keiren frame builders in Japan:

"We are pleased to be carrying steel tubing from Kaisei. Kaisei tubing is made to the highest possible standards, with the best possible raw materials, by the people who once made the best riding Cromoly tubing at Ishiwata! 4130 CrMo tube sets are available in standard or oversize diameters, double or quad-butted, in a variety of gauges."

https://www.bikeschool.com/store/inde...c=Steel_Tubing

Yes, 4130.

Whats the deal with the Kaisei 8630? Nickel Plated? Oh man seeing all these tubes makes me wanna make my own bike

The makers of 8630 melted some nickel into the mix along with chrome and molybdenum in order to give 8630 specific qualities.

Kaisei describes this steel as "heat-treated," and this could mean many things.

Apparently, Keirin frame makers use 8630 for their high end frames.

A few years ago I visited the United Bicycle Institute in Ashland, Oregon.

I highy recommend UBI to anyone interested in learning how to make a bicycle frame.

https://www.bikeschool.com/

Unless somebody's got evidence to the contrary, everything I've found points to Reynolds 520 just being Reynolds badged 4130 tubing. Quite possibly from the same Taiwanese production line which cranks out the tubes for Surly and countless others.

Ken Cox is right. All of the different tubing is used for different applications, just because some bike is made out of exotic tubing doesn't mean it's better. And reynolds 520 is just reynolds branding of 4130, you are correct Clifton. For the most part, steel is steel. All of these different types of tubing correspond to very minute differences in alloy percentages. The only way to make a big difference on a frame's weight is to use a different material altogether- aluminum, cf, titanium, etc

So if you mix and match the kaisei tubing what would be good for what purpose? Oversized? Quad Butted? This has interested me alot since I'm disappointed in how the tear dropped leader came out and I noticed this tubing has a aero down tube tubing . but my main question is what would be good to make this frame out of? A mix and match of 8630 as the main triangle and then 4130 as the extremities? which version 17 19 22 etc? from what i can tell 19 oversized with quad butted should be a tank?

People are way overthinking this steel stuff. If you want a durable, smooth riding bike, go steel. If you want a smooth riding, light bike go Carbon. If you want a light, cheap bike, go Al.

u forgot if u also want super expensive and super light, go Ti

How is Reynolds 753 compared to other tubes? My frame is made with a mix of Columbus and Reynolds 753.