I’m not taking you to task with this statement, I’ve heard the same thing many, many times. Does anybody actually think that a 5 grand+ chassis that needs replacing after 6 months is acceptable? Personally I think it’s ludicrous.
What’s considered frequently?
Honestly I’ve yet to see any empirical evidence of a chassis needing to be replaced unless it’s badly ground away at the waist, has left rail sag or has been badly bent in some way.
I hear the term “flexed out” but it doesn’t line up with our general understanding of metallurgy either.
In short, best I can tell the need to replace chassis is more from a war of arms/psychological advantage than anything actually related to performance. “This racer replaces chassis every race so I have to as well”.
I’m not saying a chassis lasts forever, but I think it’s worth noting the connections/affiliations of folks that advocate for regular chassis replacement.
And yet my limited experience has been failure after about 8 race weekends followed by weld which lasted another 2 weekends followed by giving up. So that’s consistent with “get a new frame every season”.
To clarify: y’all that don’t need welding of bits that get rattled loose… I agree. Ride it till it breaks. But, it seems to me once it starts breaking… you get 2 welds or so before it’s time.
Again, I was on a 2016 OTK with 2 seasons of national racing on it, replaced it back-to-back with a new 2018 and it was the same speed.
We had to dial positive camber into the front of the 2016 because it was sagging in the middle. Still was just as fast as new.
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Was it sagging at the waist or across the front most bar?
My understanding is this; American chassis are made mainly of 4130 condition N chrome Molly, while European chassis are made from 1018 seamless drawn over mandrel mild steel. They both have the same, I want to say stress resistance, but it’s something else. In any case, the chrome Molly frame will last for just about ever, a mild steel frame fatigues, for lack of a better name. That’s why you hear the stories about replacing the frame after every race. It’s my understanding that, in European racing, you’re only it allowed 2 frames per race weekend. I personally have seen a driver I was helping, who had a European frame, find that the front of the frame was worn through because apparently it was sagging at the bend. Right behind the front frame member. That’s my only personal experience, the rest is mostly hearsay.
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If my understanding of metal fatigue is correct, chassis “fatigue” should be a someone reversible condition with heat treatment, and annealing. right?
Without verifiable evidence I can’t say anything for definite, but I run a 1989 kali in historic racing and she’s still going strong. 
I tend towards the theory that the chassis’s ultimate performance might not drop off significantly with use. However, if you are racing at the highest levels it’s a variable you don’t really want to be chasing. Chassis themselves can be considered ‘set up’ changes if your income allows a chassis to be considered a consumable. But if you are happy with a consistent chassis product it’s better to be as fresh as possible. Otherwise you might be chasing set up to achieve the performance you desire as the chassis sags or gets tweaked.
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Little bit of a side note, but I still hang out with the DR Kart guys at some of their events, including Vegas. Out there, they’ll bring in Maximillian Paul, their DR KZ factory driver from Europe. They will have 3 different frames for him set up, an all 30mm tube, 30/32 hybrid, and an all 32mm frame. He’ll start on the all 30 and switch before practice is even over sometimes.
However, the moment something gets even slightly tweaked, he (or more specifically Danilo) will put a whole new frame out. They get so specific with their frames and flexing and whatnot that a mm bend is enough to throw out an entire frame. I’m pretty sure I’ve bent a frame more than that just driving a track that had curbs you needed to be more aggressive on.
I wouldn’t say that a new frame is that necessary for everyone here, but the consistency can definitely be affected after a lot of time on the track.
This topic interests me a lot though, I might have one of my friends that is still in engineering school see if he has any ideas about this.
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I noticed a big difference in my 2017 frame after I broke my 2018 (compkart) . Maybe tweaked design but they drive different. Maybe age.
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I’m no metallurgists, but it’s my understanding you can’t he treat 1018 steel without adding something to the steel. Now if you heat treated a chrome Molly chassis, then I believe you would be right, but don’t listen to me, I’m no expert on the subject.
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On the other end of the spectrum…
The driver’s name escapes me, but he worked his way up the field to podium in the supernats with the front of the frame and spindle pretty messed up.
I think in Europe it’s more crucial because tire management is of more importance.
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Welcome Al !
I’ve read and heard this numerous times and I think the idea that all US manufacturers use just one type of metal, and all euros another is fanciful and over simplified. Especially when some US brands are/were non homologated European chassis.
I’ve also see the myth that “euro chassis are made from (cheap) mild steel and therefore are only good for a handful of races” being passed around a lot. Yet chassis with good miles on them end up front… we just have to look for them.
You have to consider the sources of these paddock myths and who might stand to gain from them 
If I see some sort of emperical evidence that I’m wrong, I’m happy to adjust my stance.
Who works as a metallurgist? Maybe I can find one in linkedin.
I never thought of that. They’re so used to running the CIK soft compounds that I have never seen in America that smaller changes probably have greater effects on the kart with those tires.
I would love to know who this driver you’re thinking of is, sounds like a good story. It reminds me of I think it was TJ mentioning something about a guy at like a Rotax Championship Final race and he bought some worn out OTK on site and won the World Ticket with it?
That might be @JordonMusser
Yeah I can’t think of the other driver nor can I remember who told me the story and it irks me.
Stepanova Nekeel. If I recall correctly, he was on a new kart of X brand and after practice he bought a used OTK for less than $1000 there ended up driving to the podium.
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I drove most of this season on a 2014 kart, pace wasn’t a problem (we won 3 rounds of the 6), tire wear was, it just ripped up the fronts by midway through Sunday (in a two day meeting).
When I switched to a 2019 kart the problem went away, different brand but I really don’t think brand was the source of the problem.
@Aaron_Hachmeister_13, Danilo has always been a perfectionist, plus he’s selling the kart lol.
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No difference in geometry or spindle rake?
Of course there are chassis difference but I’ve been doing this for a while now and set the handling very similar.
I get that. All I’m saying is that the age/year isn’t the only variable.
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