Upgrade to enjoy this feature!
Vital MX fantasy is free to play, but Premium users receive great benefits. Premium benefits include:
- View and download rider stats
- Pick trends
- Create a private league
- And more!
Only $10 for all 2026 SX, MX, and SMX series.
The 97-99 CR250 just took it's shirt off 😆
Ha, indeed. That frame was garbage and being a first year aluminum frame they really didn't know what they were doing, and went a bit overboard! Check out the design differences between a 1997 and a 2023, particularly the main spar:
Color me lost as well. DV said people in the industry didn't like his "analysis of the Paris SX and the current climate of our sport", there has to be more to it than steel vs. aluminum or horsepower.
Oh yes, night and day differences.
The Shop
Luxon 4-Post Bar Mounts
$189.95 - $239.95
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
So does anyone have any idea what he said??? or i gotta wait a few more pages?? 🤣
I must have been the only person on planet earth that didn't totally hate the 97 CR250. I swapped springs, changed the valving and rode the shit out of it. I do remember that fork height made a big difference also.
My buddy who was big and strong and very fast loved his ‘98 CR250. Liked it better than the ‘02 he had later.
We know it has plenty of power because Prado told us so.
Big fan of DV, always like when he co-hosts the Pulp show. Only time I can remember really disagreeing with him was when he said Tomac needs to stop using the scoop tire. Couple years later and it’s basically all anyone uses.
I didn't get along with that bike at all. I felt like more than it being overly harsh was how inconsistent that it was. 1 lap felt fine. The next lap you felt like you did the same thing but the bike reacted wildly different. That was my biggest issue with it.
I am probably guilty for some of the steel = flex and aluminum = harsh, talk. Growing up with bmx bikes, it just felt like if you had a 4130 chromoly race frame and then went to an aluminum frame, you could just feel how much stiffer the aluminum bike was. And it was good and bad, in different areas. So I do think the science behind it aside, between a lot of comparing mx bikes (like the 97 CR) and bmx experience, I just associate aluminum frames as more stiff than a steel counterpart, based upon feel. But I know that isn't always the case.
In general strength of materials, you are right, steel is way stronger than aluminum but, in a strength, to weight ratio aluminum has it beat. In dirt bike frames due to construction, it's a safe statement to say that aluminum is stronger even if it drives anyone who has picked up an engineering book nuts. It's like telling a machinist that something is made out of billet. I haven't been in the tool and die trade for years and I still want to punch people in the face when I hear billet. hahahaha
Yep. You were right. Engineer here. Hardness and stiffness are two very different things. Aluminum is softer than steel, but much stiffer (in general).
Think about how far you can bend aluminum before it doesn't bend back and/or snaps compared to steel.
What was said in your last sentence shouldn't irk you, as it is inherently true without additional measures taken. If steel has the right natural stiffness ("flex") for a dirtbike frame, then you will need to do things design wise with aluminum to make it mock the stiffness of steel..
Sorry, important point to make. Assuming the sectional strength of both is identical, the aluminum will be stiffer.
Shouldn't an engineer be using terms like elastic (returning to original shape) and plastic (staying permanently in bent shape) deformity? lol
Mechanical engineer here as well and if you are genuinely curious and want to compare the two materials. Google or look into the “ Young’s modulus or modulus of elasticity” of the two materials. The ductility is also what most people are referring to when each one has more flex but returns to its original position. Aluminum can move much less than steel before it can no longer go back to the original shape. Aluminum can be just as stiff with a little more material but the cost then comes into play. Just need to create performance index of your budget needs and materials needs to determine what is best. Kinda interesting to think the Japanese bikes and the Austrian bikes have a different performance index or goals to meet with their frames. I think that is the ultimate difference between the two choices of materials.
It is NOT safe to say that an aluminum frame is stronger than steel. Or vise-versa. There are a ton of variables at play here to just make a blanket statement like that. For one, strength varies wildly with alloy and heat treatment. There are aluminum alloys that are stronger than steel and there are steel alloys that are far stronger than the strongest aluminum alloys. Each alloy has various other properties to consider as well, not just the ultimate tensile strength: fatigue strength, notch sensitivity, ductility, corrosion properties, etc.
I wrote a blog post about typical structural materials used in moto parts a while back that goes over a lot of the basics, but there are a lot more details involved that are out of the scope of that post:
https://www.luxonmx.com/blog-luxon-structural-motorcycle-materials.html
If you remember, they had much less material prior but during testing they started breaking and Honda got spooked. So they made sure as heck that wouldn't happen and came out with that beast.
To the guy who liked the 98 better than the 02, I was the same, but that's probably due to the motor. They both vibrated plenty.
I can if you like. Not everyone knows what the terms mean though. They can't relate that to toughness, strength, or stiffness though. If I said think about elastic and plastic deformation of the two materials, do you think more people would understand?
Pit Row
Cool! Thanks for sharing and I will give it a read this afternoon.
No but really, what did DV say?
What gets me is when I hear of riders supposedly being able to tell the difference in flexibility of engine mounts. I couldn’t notice the difference in an engine mount if it hit me in the face.
He said all the stuff about the things, and all the people got mad because of all of the reasons. Also, metallurgy.
Would you also be concerned that if you made the alu frame to "flex" like the steel you'd create a situation when you prematurely get cracks in the alu?
TM
And he said it in French so we would all be frustrated that we didn't know what he said, which makes what he said worthless unless we can get 10 pages here to finally find out what we don't know. And by that time we'll have forgotten what started this thread. 🙃
It all depends on the design. In general, aluminum will fatigue and fail before steel will, but that depends on the stress levels and the stress levels depend on the frame design. Whether the frame is steel or aluminum is only one part of the picture. That alone doesn't tell us much of anything about how the chassis will feel.
I bet if you bench tested a KTM chassis (frame, swingarm, fork, clamps, etc., including all structural parts axle to axle) it would be nearly the same stiffness as a Honda, Kawi, Yamaha, etc. chassis tested in the same way (and not necessarily less stiff). Which is related to one of DV's comments that started this thread "It's not about the frame alloy, but about the settings, balance, and equilibrium of the motorcycle."
A good friend of mine who was a top rider once told me that "if I had to choose either good suspension or good power, I'll take the good suspension"
I’m glad DV was successful and smart enough with his money so that he doesn’t have to rely on endemic sponsors to cover anything he does. One of the few that is off basically any kind of leash and can say whatever he wants.
Just making yucks. Nerd humor.
I was saying in relation to current motorcycle frame design. Yes with FEA they can tune softness into areas of the frame that need it but in general the construction of frames today aluminum is stiffer. It's like saying Cresent wrench or Kleenex. I know you know your stuff but you could get into the weeds and confuse a lot of people. I have been known to read the Machinery's Handbook for fun and I'm sure you could confuse me. I have engineering classes and expired CAD certs but I'm not an engineer.
You mentioned that aluminium was weaker long term compared to steel if I didn’t misunderstand you.
However I’ve seen a few KTM group bikes be longer in the end of the season, when the sprinter door no longer closes against the front tire..
But I guess that’s just KTM’s steel frame being to weak, and not the steel in general? I think I remember the KTM 450 wheelbase being 15mm longer after 90 hours on this A class riders bike.
Post a reply to: Oh My, What Did "Le Cobra" Say Now???