Axle length help needed

I have a new to me Birel RY30 with a 1400mm rear axle. It appears this is the original axle, or at least the original length. The hubs are 95mm and again appear to be the hubs that came with the kart. My dilemma is, with the wheels I have and the hubs on as far as they will go, this puts me at an overall rear track width a hair over 55". This leaves me no adjustability. The axle could be cut down, but there isn’t much excess to remove without affecting the keys. I could buy a different axle that is shorter or I could buy shorter rear hubs. Each option has pros and cons, but I am left scratching my head why does Birel set the karts up this way? Would like feedback on what option makes the most sense.

Are you sure your axle is 1400mm? The rules would probably dictate that 1400mm overall rear track width is the max allowed, so with a 1400mm axle that would be extremely wide.

Most axles are 1040mm or 1030mm, with shorter versions being 1000mm.

Sorry about that. My error, it is a 1040mm axle.

I’ve never made kart setup adjustments, but I’ll try and help. I think the one downside from I’ve read is that a smaller track width in the rear axle will cause more oversteer, so I don’t know the handling of your kart right now, but on conditions where you’re experiencing more understeer, this could be a potential way to go. I hear there’s people who use 1030mm rear axles and they work well, but I’m guessing it also depends on the class you’re running in.

Another thing is that longer and stiffer hubs stiffen that area in the axle, equaling more grip. If you need to soften up the axle a bit, then softer, shorter hubs can work. I think it really depends on what setup the kart needs and then go from there.

Here’s a link that talks a bit about rear end adjustments: REAR END ADJUSTMENT

One of the things that they mention in the article that was interesting and could help you decide what to do. “Use short axles for sticky high grip situations when you are experiencing understeer. Use long hubs on cold slippery days when your kart is too loose.”

If I have said anything that is incorrect, please let me know, this is from my current limited knowledge :joy:

If you’re running OTK wheels or something with a similar offset, then that’s why you’re wider than what the Birel Factory wheels would allow. The offset difference between the current BirelArt wheels and OTK is 12mm per side.

I would consider buying other wheels. If you’re in a lower HP category then a shorter axle could be worthwhile as well.

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Yeah agree with Evan, there must be a mismatch somewhere in the rear with wheels or hubs. The kart should of course have rear track adjustability.

I would try to isolate what is different (wheels are the likely source as Evan indicated) first before buying a different length axle. Changing axle length will affect the handling so I would want to address that variable before doing it.

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This is all pretty general, and not always necessarily true. Axle tuning is a very complex piece of key tuning, hence our other 8 million page topic discussing and debating it. :sweat_smile:

Ok yeah just trying to figure it out myself :joy:

I didn’t know that the tires were designed for different kart brands, but it could make sense, it would definitely make a less drastic change than changing the length or stiffness of the axle itself

So it turns out that is the case. All of my wheels are 58mm offset. I was not aware that Birel / Freeline used a different offset. If I understand you correctly the offset would be 70mm (58+12)

Is anyone aware of other brands that use the same offset?

I tune my 206 axles with a sawzall… :flushed:

Regarding @mtbikerbob and cutting into the keyway, I cut my wheel keys to right next to the first peg. It leaves me with a peg for the hole and the little bit of “overhang” on the end of the key. You don’t need a full key under your wheel hub.

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Do you want a set of Birel wheels? Fronts are 17mm spindle mount, rears are 6-hole metric.

Ummmm… so when you cut off part of the axle, you cannot go back to the original length cuz it’s gone??

Yea, once it’s short, it’s short… But if you’re cutting it, it’s for a reason and I doubt there would be a want to go back longer. My current 50mm axle is down to like 960mm.

I mean if you ever find a situation where you need that cut-off part, just super glue it back on :joy:

I would be interested in a set of wheels. I have 25mm front spindles.

I did find a brand called Techno sells 72mm offset wheels, but I can’t find anyone that sells them?

The next closest offset I’ve seen to the Freeline is the Douglas LV Mag at 67mm.

@da_sniffa32 you can space the hubs back out with spacers inside the hub. Many racers have cut down axles to 1000 and spaced back out for tuning purposes.

We personally have some from 960 to 1030.

oh ok I didn’t know that existed that would tuning easier without having to buy new axles. How do you put the spacers on the axle and the hubs, is it like an extension on the axle and then you put the hub on the spacer?

The spacers slide inside the back of the hub and will then sit against the face of the axle widening your rear track.

Below is a video explaining how to cut. You don’t need this special tool. You can use 2 50mm collars as guides or a really good blade and keep your cut straight.

Tip: put your key on the axle when cutting. It’ll be the correct size :wink:

https://kart360.com/learn/axle-basics/cutting-your-axle

This link shows you the spacers. Many shops will have these. Using your local shop is always a good idea to build a relationship. They may even help you out with cutting it down. Always good to have that local help.

https://cometkartsales.com/Kart-Master-50mm-Wheel-Hub-Aluminum-Axle-Spacer-Kit.html

I could sell you the rears. The fronts would require different spindles and depending on what class you’re running might not be the ideal setup.