CrMo vs Hi-tens -- advantages? disadvantages?

[Katzenjammer]

Why did builders go from hi-tens to crmo, apart from for the sake of advertising?

(I honestly don't know. Is it lighter, cheaper, easier to work, something else? I've looked at Sheldon's site, but the info he shows boils down to "531 et al. are better than hi-tens". But he doesn't say in what way/ways they're better. Is the answer even well-defined at the level of framebuilding? Or is it one of those things that "everybody knows" is better without being able to say why in a clear way? )

[Peterpan1]

What is it, never heard of it?

[Walter]

Hi-ten steels have relatively low strength to weight ratios. To make the tubing strong enough for a bicycle frame it must be fairly thick walled tubing.

Cro-Moly and other alloys are considerably stronger alloys hence thinner walled tubing. Less weight and overall livelier feel in the frame as it interacts with the road and the rider.

A metallurgist can define terms more precisely but essentially that's it.


:beer:

[Peterpan1]

So what are we talking like 1080?

[Falanx]

Stop! Halt! Cease! Desist!

Hi-Tens is a horribly misleading term, used primarily to confuse customers. It's almost certainly ERWed SAE1060 (080M60 for those of us in the UK), which means it's not even real tubing, it's been welded shut from a plate bent round a mandrel. It's not a good tubing for welding, as its carbon content is too high and its toughness in both the as-rolled and welded conditions is dire. It's the cheapest of the cheap thats strong enough to make bike frames.

Almost any specifically alloyed steel is superior. But this is not, as most people mistakenly believe, because the alloying elements in some way mamke the steel intrinsically stronger. Steel isn't alloyed for that reason excepting rare circumstances. It's alloyed to force certain microstructures during production processes.

Your 'chromolys' or other alloys are superior materials primarily because they behave themselves during welding. The recent BS concerning 'thermophilic' (WTC?) steels and other such fripperies is only a distraction to slightly better steels. The cost of the alloying provides a reason to spend more money in improving the fit-for-purpose aspects of the steel tubeset, such as exotic butting and heat-treatment. But the single biggest advantage of alloyed steels is their response to heat - and therefore welding phenomenon.

[Katzenjammer]

Thanks for the replies, but I have to say I'm still feeling puzzled. Would it be fair to say that the tradeoff is weight vs durability? Perhaps I'm misunderstanding something, but from my reading it looks as though the doped-steel tubes are made to beer-can thickness, which would seem to imply that they're highly fragile and not very durable over time. Yes? No?

[Nessism]

There is a wide range of tubing used to build bike frames and Hi-ten is pretty far down the list in terms of strength. As the others have said, to get enough strength given the lower material strength the tubes need to be quite thick. The thick tubes will help ward off denting but it will also lead to a pretty rough riding frame unless the tubes are of small diameter (think Schwin Varsity). In terms of durability I think the thick walled jobs are going to last a long time, but so what? Who wants a frame that rides like a truck?

[mikeoverly]

I still regularly ride a HiTen bike road bike that I've had for over 25 years now. Riding it back-to-back with thinner-walled cro-mo bikes it does feel just *slightly* like pedaling a board, but I don't think there's anything undesireable about it. As others have said, the tube walls are thicker (and very unlikely to dent) and the frame is heavier -- not by a lot in the case of mine, which is built up at 23 pounds with clinchers.

I also have a HiTen "mountain" bike -- straight out of one of those dissed discount stores. It's the plushest of all of my bikes, and pretty responsive for a 32-pound beast. All of that "plush" is in the tires & suspension fork, of course.

HiTen is nothing special, but nothing terrible IMO.

[Peterpan1]

How thick is the walls in the stuff under discussion?

ERW is pretty nice tubing (your right about what it really is, but the folks that use it refer to it as tubing. pipe in this crowd is unfinished on the outside if you really want to see somethign pretty repulsive). It's great for motorcycles, though DOM seems to be prefered. I think most of it is low 10s really. You can harden 1060.

[Thylacine]

Thanks for the replies, but I have to say I'm still feeling puzzled. Would it be fair to say that the tradeoff is weight vs durability? Perhaps I'm misunderstanding something, but from my reading it looks as though the doped-steel tubes are made to beer-can thickness, which would seem to imply that they're highly fragile and not very durable over time. Yes? No?

Err....if you make something stronger - and specifically stronger at the weld zones which is where frames break - you can also make it lighter because you don't need as much of it to make a frame strong enough to stand up to the rigors of a bike frame.

To keep it simple......

Weaker tubing = need more of it to make it strong.

Stronger tubing = need less of it to make it strong.

That's why a 1600g frame made from Columbus Foco is more than likely stronger than a 2500g 1060 frame.