TimJ

I've got a couple of bikes, a trek and a univega, that simply say "chromoly" on them but no #. As I understand it 4130, ferinstance, is a designation based upon the components in the steel from the AISI like while something like 531 is a trademark.

Checking out steel grades online it looks like the AISI just lists chromoly as 41xx. So, the question is, if a bike is labled as chromoly but doesn't have any trademark or # designation, is it basically 4130? 4130 seems to be the baseline for a steel to be called chromolly. Is this correct?

TO11MTM

Not quite..... the two numbers after the 41 have to do with the carbon content.

https://en.wikipedia.org/wiki/41xx_steel <-- Wiki has a bit more info...

TimJ

Yeah, but I can't find any designations lower than 4130, so it appears 4130 is the base of what can be considered chromoly, that's what I'm wondering. I'm just curious because bike folks are familiar with "4130" and if you've got a bike that just says chromoly, can you call it 4130 and be done with it?

JanMM

4130 is the standard cromo for bike tubing. The only other numbers I've ever seen are associated with specific brands.

TimJ

Sounds good enough for me.

HillRider

It's a small point but Reynolds 531 is not is not chrome-moly. It's a manganese-moly alloy.

Cyclepath

Thanks for that. My Peugeot Success with double butted frame tubes is just decaled "CrMo" & i wondered if there was more to the story.

Any comments on combining an alu fork (Sakae Litage FX in my case) with crmo frame? I did this after a crash totaled the steel fork & the ride seems better than when it had the original steel fork.

HillRider

Sure, why not? My '96 Litespeed build kit included an SR Al fork. I rode it happily for 30,000 miles and it's still in my parts supply waiting for a suitable home.

It's not as light as current carbon forks (~500 grams with a 175 mm threaded steerer) but it was far lighter than the steel forks available then.

Slavic

You can most likely assume that it's 4130. 4140 and 4150 are the only other chromoly alloys that I've seen in any sort of mass-production bike part, and they're both generally considered too hard for frame applications.

silversmith

Of topic, but I saw my favorite ride's fork brought up.

Not only do I have the fork, I have the rest of the Sakae Litage, too.

moxfyre

Ditto. I believe that the generic alloy known as chromoly is simply another name for 4130.

moxfyre

Cool. I've always wanted to know what an aluminum road fork felt like. I had a 1990 Sakae Al fork, but sold it without ever trying it out.

silversmith

Moxfyre, I still like steel best because I trust it. Don't get me wrong, I swear the Sakae rides like it was made for the winged god Mercury. But I always think its going to end up crumpled up like a beer can.

Its far lighter than Cannondale and Trek AL bikes, and even lighter than the Vitus it resembles.

By the way, I've put those AR derailleurs you sent me to many miles of good service.

moxfyre

Yeah, the weight difference between the Al fork and a steel one was fairly astonishing. I did wonder about reliability of Al forks. I too feel most comfortable with a steel fork.

Glad to hear it!!

matimeo

OK, I'm going to jump in here and provide the opinion that just because a bike says it is Chromoly doesn't mean it is 4130. There are different qualities of chromoly steel, and I've always assumed that the ones that don't say 4130 are because it isn't as good. I've had several old bikes that were chromoly, but you wouldn't know it from the weight because it as cheaper stuff. Maybe I'm wrong, but I don't think that you can assume that all bikes that say chromoly are equal.

moxfyre

Certainly there is a lot more to the frame than the metal of which the tubes are made! But I do believe that any frame that says chromoly/4130 is made from the same basic alloy of steel, for what that's worth. (For one thing, basic chromoly has several times the tensile strength of plain hi-ten steel)