Kart Chassis Tubing Diameter\Durability Discussion (From Pro Tour Discussion)

Yeah, I was watching the SKUSA Pro shifter pretty closely this weekend. As with most modern karts it seems like they all can win, just comes down to driver and tuning.

Did you go with a 32mm (801RR?) chassis? OTK seems to be the only manufacturer offering an all 30mm chassis. With as violent as shifters are (all things being equal) it seems like a 30mm chassis is going to wear out much faster than a 32mm.

I already have issues popping seat mounting tubes constantly on an OTK running TAG classes. Feel like I’ll tear them off in my first season running shifter.

Most of the pro shifter field was on 30mm equipment. Masters had a heavier mix of 32mm (or American equivalent for Factory Kart and HMG), but I believe the CRG’s on the grid were mostly 30mm (KT4?).

The current Race Factory KZ chassis is all 30mm.

Factory and HMG shifter karts for the 2022 season are 31 mm.

Can’t decide? Build something yourself inbetween the two…

…or a mixed tube! On the wear topic…I don’t think it’s all about diameter. Diameter is just one of the factors,whereas rumors seem to always align around Tony-derived chassis being noodles and CRG-derived super stiff, which is probably a rumor that will never go away, despite any hard evidence.

I’ve run back to back Aluminos RS1 (32mm), RIO (32mm), Factory (31.75mm), FormulaK Fighter (mixed 30/32…it’s basically a 30mm with front hoop and diagonal 32mm) and Birel CRY30-S12 which is 30mm allround. As a tall/heavy guy I can tell you 32mm is not always the good choice, even from a frame longevity standpoint. The Birel as an example, despite being a 30mm, it felt surprisingly rigid, it’s the whole geometry, thickness, hardness of the metal etc. that makes the magic happen.

Same thing for the Formula, which has few quirks so you can’t just go by 30 vs 32…at the end you need a chassis that works and flexes in the right way for you, the tires and engine package and has brakes that you feel good with. My advice is to throw away pre-conceived notions, test them and go with what you get more support for, parts and advice locally or on the net as you can tweak things around.

They can all be competitive and last, as long as you don’t jump/takeoff on curbs like no tomorrow. One more thing: Birel has a 30mm and a 32mm chassis and very few drivers, including masters, opt for the 32mm.


1.25”, so 31.75 mm :wink:


The Birel 32mm is a special order from italy, at least here in Australia. The local importer doesn’t even bring them in.

I worry about the longevity of the 30mm in KZ, but winning is more important than longevity at the highest level.
From my outsiders view national Chassis only need to last the season and are then on sold for a new chassis the year after.
Which I think is somewhat overlooked in some of these discussions. National level competition is different to the vast majority of competitors at local events who will be hanging onto a chassis for multiple seasons or until it wears out.

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I’d really like to see some actual data on chassis durability as it relates to tube diameter and wall thickness. Measure deformation, spring and damping before and after. Understanding the class weight would be good too and of course they would have to undergo a similar amount of laps and abuse.

It’ll probably never happen unless I (Or someone equally silly) do it though :laughing:

Anyone want to sponsor it? “We tested these chassis and the results will surprise you”

For now I’m playing with my dyno.


Would be nice to collect some tubing from junk karts at the end of the weekend and run tests.

SuperNats usually has a fair selection of junked frames sitting in trash bins at the end of the day.


mmh that depends. I don’t think they use them for that long (one season is a lot of wear and tear). I won’t comment on the US scene, but I’ll tell you the bigger teams in EU use them for one event only, then they sell the complete chassis, which at that point is semi-new. Many people jump to conclusions and think they do that because the chassis all of a sudden becomes significantly slower when in reality it’s just a business model at play. Say you are a big team that gets them at about 40% discount or a big manufacturer that leases the new chassis out on a per-event basis to those teams. Once you are done with the event and get it back, you are much better off cleaning it up quickly and selling it at 20/30% discount to a retail customer or a distributor for even less and break even, instead of paying $100+/hr (fully burdened rate) for a technician to overhaul it completely, wasting time, money and real estate with all the hidden risks that may pop up at next event…simply not worth it.

That of course does not translate at all to the local scene, but there’s no scientific way to prove durability, they all have their pitfalls but generally speaking, all solid quality nowadays. Once you cut through the data without any bias, you’ll see that Tony chassis had a lot of breakage exactly when everybody was running them, and mostly on used and abused units. Same with CRG breaking under the C’s…lots of failures…when everybody was on them so I guess on a % basis, it would be leveled but of course you only hear the complaints.

Apologies for the long post, I guess it’s a topic I’m passionate about :person_shrugging:

We are essentially in agreement except for time frame, which would vary from country to country.
I was trying to point out the difference between worn out at the National level and worn out at a club level, as they are completely different. At the highest level the last tenth matters more then the cost of the chassis sometimes.

A big team doesn’t pay MSRP. Selling race-old or 3-race-old karts is how they stay in the good graces of the manufacturer/importer.

If a new chassis retails for $4995, and a big team is getting chassis for $37500 for ten, spending $300 in labor each to build them, and they try selling new unassembled chassis out the door for $4400, the manufacturer will soon send them a nastygram pointing out that their special deal includes not undercutting all of their dealers. Instead, if they assemble them, race them, and sell them out the door for $4000 afterwards, it’s costing them $50 per kart to have a new chassis at every race. This does not have to be reflected in what they are charging their drivers!

Its not chassis to chassis but talks to material selection amongst other parameters.



I feel like I opened a can of worms on tubing diameter… :sweat_smile:

Has anyone back to back a 30mm vs 32mm chassis from the same brand? Was it really that noticeable? X hopped in the corners or was really free versus Y. Was it a blind test to rule out placebo?

From that report it seems like the FIA and Kart manufacturers need to be told that karts should be made from a cheaper and longer lasting material…

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I ran the 28/30, 30, and 30/32 Haase in the same season in juniors, the all 32, 30/32, and 28/30 Merlin in the same season, and the 28 and 30 OTKs in the same season and yes, all drove very differently and felt very different.


I have quite a bit of time on both the 30mm and 32mm shifter chassis by CompKart. Both were fast, and could be made to work, but ran completely different setups, and also drove quite differently. The 30mm kart made more grip from being noticeably softer, and we generally used the 32mm frame for larger drivers. It was quite a bit stiffer, and very front-positive, but seemed like it had a little bit narrower window to find the ideal balance between the front and the rear.

To your last question- this was not a blind test, though I have hundreds of laps on each, and with a range of setups.

Most brands these days seem to favor one or the other. CRG is really the only one these days that has multiple models in regular circulation.

Archived a copy of this in case it goes missing…

Go_Kart_Chassis-Rethinking_go_kart_chassis_materials-min.pdf (1.3 MB)

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To my knowledge these are the 4 shifter chassis for 2022 that currently have both options:
-Birel: CRY30/CRY32 (with the 32 being very uncommon)
-Parolin Invader/LeMans (mixed)
-IPK Fighter: 30 and 32 (but the 32 option is a mixed 30/32)

CRG is probably the one having the biggest numbers in both configurations though

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