Frames - Steel -v- Aluminum

I absolutely loved my CRF250X - I had a 2004 that has been around the block about 10x and still handled better than any bike I have ever owned. If Honda would have added 60-90cc, and an EFI system (I mean they HAVE the EFI) I would have paid 10K for one.

No matter how much money I threw at WP, they were never as good as my little "play bike" right out of the crate.

That aluminum frame felt like brand new after 10 season of getting absolutely hammered.

On that same topic, changing a jet took 2+ hours!

The aluminum perimeter frames are great. A bit harder to work on the bikes, I agree with that and so do my buddies that own them. I have quite a few buddies that ride them myself. I try to stress to them that the Aluminum frame is pound for pound as strong as a steel frame. Thats a fact. They seem to like them even though the aluminums bulky size of everything makes for some compact packaging design tricks required to maintain them even if they can go longer between maintenance intervals.

A common place for me to make money on these frames on the CRF 450Rs and Xs is this spot under the gas tank on the left side near the radiator. Oh yaa, the right side does this also..Not a great picture but thats not what I was charging him for. I sent him this picture and told him he could just keep riding it until he felt like he needed to bring it back over for a proper weld repair.

I've seen this more than a few times on these Hondas as new as 2011 or so..This picture is of a 2008 model if I remember.

This was a case of 1 picture is worth a thousand words or in this case after all the words, out came the wallet in exchange for a bit of my argon, some electricity, turn on the old Lincoln 300/300 Tig and hand over a big bit of pocket money. Guess how fast my other friends who have these Hondas had their tanks off to look for the same cracks.

They usually get a new one every 3 or 4 years at the most anyway, so I believe this guys bike was probably cracked here before he himself bought it awhile back and the owner probably knew it.

One of my mechanic buddies finds these cracks during valve clearance checks all the time.

He's a good buddy too. His own brother and himself also ride the CRF450Rs, both of which have been converted to run lights and have heavy flywheels with upgraded stator kits for the electrics and are both plated.

I greatly prefer steel frames myself, I have worked on many alum frame bikes for friends and for that reason refuse to own one.

Rumor on the street is KTM is gradually moving to alum... they are rolling out a half and half version for the 2016 models.



Later,

I agree the steel frames are able to flex better over a longer period of time when ridden hard. They have an inherant ability to spring back and have a built in memory as most chromoly or quality steel tubing possesses. They are more foregiving. The modern day fabrication of a steel tube frame only has mildly different wall thicknesses of the tubing used throughout its construction. Except in the steering head area which can be heavily gusseted with steel reinforcement plates similar to the thickness of the tubing used for the rest of the structure. They are much more easy to repair or modify when needed.

Aluminum frames on the other hand are quite stiff in there design, don't give much flex and when forced to do so over a period of time they will work harden with age and become more brittle as time goes on. This happens to all aluminum, and in the case of motorcycle frames it will do this after any repeated flex during its life span which leads to cracks from its inherant design stiffness. Most of the time what causes these cracks to develop will usually be where the heavier castings or frames forgings are welded to the extruded tubing.

It has alot to do with the dilution rate of the parent metal by the filler rod used during the weld process. These different castings, forgings and extruded structural tubing may be a "bit off" and are just "off" enough to be considered 2 or 3 different alloys. That everso slightly, even mildly different chemical alloy make up of these components likely sourced from some outside venders from all over the place are being welded together. Then if they even bother, the frames are either mildly heat treated or stress relieved. Which would make them even more stiff and therefore brittle. Add to that the fact that they have also welded something very thick being joined to something much thinner. The cracks will usually be next to the welds on the thinner of the two components, not at the welds themselves.

Take a strip of thin aluminum sheet sometime and clamp it down to the edge of a table. Then bend it down over the edge and up back and forth a few times. You will feel it gets harder to bend after going back and forth several times. The next thing that happens is it will then break or fracture. That will explain this very quickly.

IMHO.

Aluminum frames will always be good for making cash though.

If these guys go with a fat bar design for a frame and call it a Husky, it could be a show stopper for me ... I'm 56 and don't really need to spend any more money on bikes in the future. I do need 1 or 2 more WR250cc 2 stroke Husky though and I think they will be available, in good condition, for another decade at least . You young guys can keep powering the worlds economy with new sales stuff ... I'm OK with that .. I'm sure SP does not care about us old guys also ...OK with that also.

Ktm can do absolutely anything with bikes today ... Lets hope that they do not copy their rivals for 1st world bikes. What they are pimping to the 3rd world, Ok, it helps these societies greatly and not in just a recreational way.

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RD5 has a prototype 016 racer now ..Maybe we can get pic of it someday in the near future ...

I'll try to read more on what you guys have written on the technical side above about ALUM engineering.

Funny i was wikiing benefits if parimiter vs steel frames the other day, overall ally appears more ridgid, stress crackpictures are interesting, if i snap a tube on husky i would crack out my mig. No paying for anyone else re gusset it in appropriate manor.
Think thats mainly an issue for big hit mx bikes no?

Hard to work on yes i agree evil if you want the carb off on cr 250 honda mate spent ages while i was doing ring change, i finished the whole job before he got the carb free.

Weight pound for pound? Yup i agree but theres more ally per pound so bigger also 99% have two thick tubes around the top of the engine! Higher center of gravity? Even if it is light material thats a no from me.

And the common as muck i polished it an now its pitted? Well my friend you should of left the annodising on it but too late now, go polish it every time you ride get it clear coated or powder coat it pink so everyone knows your a knob.

Im a fan of the real steel frame

Yaa, No BS there. My buddies seem to polish the aluminum frames also. Quite a bit more than they ride them. One of my partners has an older Banshee Yamahaha and its like all chromed out, billet this and that, with the cut down plastics painted with candy apple red House of color paint and he won't even take it out and ride the damn thing. Its useless as a door stop.

I don't get it, if you ride the bike it will polish itself on its own just by riding it and having dirty riding gear on. Especially with all of the acrobatics they have to perform to keep up.

Last time my same buddies immaculate crf450r got loaded into my truck to go riding his bike was like brand new, absolutely spotless. 3 hours later it had both front forkseals blown out, oil all over the place and a puddle under the bike in the back of my bed liner all the way home, thats still there to this day.
30 minutes after I dropped him off I get a text with a picture of his bike ripped to pieces and already the fork legs were off and ready to be shipped off to get serviced and all the plastics came off and the polishing routine began again. My bike was still in my truck till the next afternoon. Haven't ridden with him since and that was on like January 26th. I've also texted him or called him every weekend since then and he still hasn't gone back out to ride. LOL!

Frame and suspension harmony is more important than rigidity for trail bikes .
I hate ktm suspension and ergos.
Loved my old 05/06 wr250/450 and ally Yamaha.
Just feel good, so it's more about personal gelling than tech.

A certain amount of long lasting but controlled built in flex and a forgiving design is key for what these bikes go through. Indoor SX has a totally different requirement IMO in comparison to outdoor GP MX requirements.

I must say in all my years welding, which is a bit over 40 years. I probably made way more money welding on the old Japanese steel frames back in the days before they went to the current aluminum perimeter designs than I ever will make on the Aluminum frames. But I can charge a damn sight more for each time I weld on 1 too. So I'm cool with the aluminum frames for now. They can keep on making them.

My Big Lincoln Tig has only paid for itself about 5000 times over what I paid for it back in the late 70's and it still works great and makes absolutely nothing but money.

Plus I got lots of out of town guys bringing their stuff to work for me to fix also with either of the 2 newer Squarewave Tigs I got here at 2 different locations, that ride also. When I have time I fix it for them. So it doesn't cost me nothing to fix that stuff. That's even better and I take my sweet ass time doing it. Get paid twice too. They have a donut, I have their cash. Hell, I've lost 35 lbs. during my lunch breaks, much of it under the welding hood. They usually leave me the donuts too.

I've seen RD5 pushing his bike more than once in races trying to bump start it ... Do the ktms only have estart?

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Seems like the ALUM frames were gonna be more flexible when the Japan bike makers started down this road and quit the steel frames several yrs back...

steel framed bikes have been dominating MXGP, world enduro, and have been up front in AMA comp as well....but from an Al perspective they have also been at the tip of the spear as well. Ride what you like. wait til composites and more plastic come to our little dirt bike world....more opinions will be formed. PS lots of that all ready about Al vs the new "plastic" subframes for Beta and Husky.

Maybe its the stand but that bikes sexy