What are the benefits of loose, rolling axles?

redlinederby Friday, 2/14/2020
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Hot Wheels come with loose axles that roll with the wheels when the cars are moving. The wheels roll, the axles (often) roll.

The common practice when modding cars is to glue down the axles so there's one less moving part in your car, which means less friction, which means more speed. I get it. Science!

But I'm not looking to debate "to fix or not to fix" your axles, I'm looking to learn what are the benefits of loose axles...are there any? 

I mean, I feel like Mattel chose to make the axles loose for a reason. It seems like they could just as easily have clamped the axles down, so I don't feel like having loose axles is just a bi-product of the manufacturing process, it was a choice which means there's reason...no?

And I admit I haven't done any of my own research on this physics question at all. Google probably has all the answers but it's more fun to put our heads together.


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WorpeX 2/14/20

My only guess on this is that it allows for a bit of a rudementery suspension system. So, if the track isn't as clean and straight as it should be it'll allow for an ability to roll over obsticles.

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redlinederby 2/17/20
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I posted this late last week so giving it a bump it to see if anyone has any more insight about loose axles and their benefits. Bueller?

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Mattman213 2/17/20

My wheel test rig keeps the axles loose and itll run heads up (with a good set of wheels) with the exact same vehicle thats in the modding process that has its axles mounted solid.  Im sure if you have perfect wheels and really really good slick axles then locking them down will provide benefits such as alignment and allowing the wheels to not be bothered by each other etc but some castings it might not be as necessary.  That said, I dont know that Ill ever leave a set of axles loose on any of my mods.  When you add weight to my test vehicle and the one that has set axles, the set axle car picks up more than the loose axle.  I might test that further when the Mod gets closer to completion, would be fun to see what happens!


  • I think my biggest issue with keeping them loose is I have no idea how to keep them loose on a standard casting! I usually break the prongs to get axels in and out and without those they'll be TOO loose. Unless the casting is prebuilt to be able to support loose axels (like the shadow jet) it doesn't seem feasible. — WorpeX
  • yeah my test rig has the interior posts that keep the front and rear axles from falling out. Some casting have it, others dont. Im workin on a Speed Seeker/Machine that wont allow it and I had to secure them. — Mattman213

they did it that way bc reasons... & cheaper. don't question science just glue them.

  • But we ARE the scientists of this field and isnt that our job? LOL. I have never considered anything other than securing the axles on my Mods, even simple rebuilds for the kid to play with BUT if I were ever to find out that a certain build ripped considerably better with the free, I would go with it just the same — Mattman213

I recently took apart an F40 and it’s axels are loose. I was always curious about this question too. If a casting has loose axels, when modding, do you leave it loose or glue em down. I’ve been leaving them how they came, but not sure which is actually faster?

The main function of setting the axels is to get the car to run straight...the straighter it runs the faster it can go...that's why Wheel Farming and having 4 good wheels is also key...more than just one factor when Building speed.

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SpyDude 4/4/21

This discussion just came up in the Facebook group, as well.  Some people are running loose axles, others swear by gluing them down.  Obviously, there are benefits to both approaches.


I only tend to glue mine in place for two reasons, one I broke the damn tabs off when removing the axles, or the casting seems to wobble about when racing due to the axle being too loose, so gluing it in place stops it swaying about.

Of course, I also made those new axle holders (in a previous thread) where it clamps a pin in place and that is working really well - it's on Five-0 in the Canyon Outlaws, the current #1 on the list.

To me, it feels that the looser axle also allows for some axle rotation, so if the hole in the wheel isn't perfect or the axle isn't either, it then allows for a little extra leeway and speed, but if you lock the axle down and the wheel/axles aren't perfectly symetrical then you're more likely to slow the casting down.

I've had cars get measurably slower after the axles were glued in place.  My theory is the small degree of freedom helps absorb some vibrations. I usually only glue if I've gone all the way to brass tubes.

  • While logic sometimes suggests otherwise, I think I'm more in this camp as well. — redlinederby

I've been wanting to do some in depth tests and videos for a while just to show the differences between some various modifications you can do. But ya can't deny Science. 

If you have never seen it. Mark Rober has an awesome video about Pinewood Derby cars and some of the optimal mod's you can do to them. A lot of these mods also apply to Diecast; but the video is geared towards drag racing. 

With Open track, more luck comes into play because of so much randomness with the track, other competitors, etc. I think the key with open track is build for both speed and stabilty. and then cross your fingers that you get lucky in the race lol. 


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redlinederby 4/6/21
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Good video, I also posted it with some other info a while ago, still good stuff. Less about axles, more about weight, folks.

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DXPRacing 4/6/21

It just seems to me, and I could be completely wrong, that with loose axles the chances of wheel/chassis friction would come into play more.  If your axles are smooth then tying them down should not be an issue as long as your wheels roll good.  Straight axles that line up with the other set seems to be more crucial for a fast car.  The extra play would in my mind be counterproductive.  But I could be wrong. 

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