Mad Bull - MC8 wheel hub worn out (splined hex drives)

[Tony Sutton 8]

Hey all,

Currently own a Mad Bull

Went for a bash this morning. After a while, the wheel stopped moving. Motor ran fine. Assumed gears.

So, took apart the rear section and found that the MC8 wheel hub (splined hex drives?) has worn out! Is this common? I assume so because this seems to be made of aluminium rather than metal, is that right?

Is there a steel version of this? In the meanwhile, I have ordered a new set plus new m4 locking nuts as a short term.

[berman 5315]

That was common on King Cabs and Monster Racers back in the day. New lock nuts are a necessity. Just be aware, some aftermarket lock nuts don't have as good a nylon as the Tamiya ones. I have purchased coloured 3 racing or yeah racing (cannot remember which) and they kept coming undone.

Don't think there is a steel replacement. You can either buy new alloy hexes, or convert the axles to the pin style with appropriate plastic hexes.

[TurnipJF 9192]

Those splined hexes can last for decades if the wheel nuts are kept tight, or wear out in minutes if they are allowed to become loose while running. Fortunately, since the hexes are made of a softer metal than the axles, it is almost always the splines on the hexes that give way, and it is easier to pop on a new set of hexes than it is to install a new set of axles.

Fresh locknuts are a good move as @berman says. I find that the serrated ones tend to stay tight for longer than the flat-flanged ones, but they do leave marks on the wheels.

[Tony Sutton 8]

Thanks. When I looked at the rear wheel, I did notice the nut was loose so this might be the contributing factor. 

I've ordered new nut locking set and also thread lock so this should help, hopefully. 

It's a shame there is no steel version, would have been good. 

Unfortunately, the MC8 wheel hub is pretty much out of stock everywhere however I have one on back order that is due to arrive 29th/30th July which seems to have the same date as other Tamiya parts. (Tamia supply issue?)

[Carmine A 2046]

Ran into the same problem with my King Cab, many years ago.... 

My PERMANENT fix, is these Clamping 12mm Anodized Aluminium Wheel Hexes.

They're also sold in sets of two at almost any Hobby Shop, Online or Brick and Mortar. Pretty cheap too! 😉 Also, because your Axles are Splined, these will REALLY grip tight.

I really abused mine with spins, full throttle jumps, full speed braking... Never ONCE came loose! 

Just cheap insurance. 😉 Like @TurnipJF said, with a good, solid set of Wheel Nuts and new Stock Hexes, it WILL last. 

This is just a HD option.

[Tony Sutton 8]

@Carmine A That looks good, but would it mean I have to drill into the axle to fit the pin in? Or am I misreading to how it works?

[Tony Sutton 8]

Anyone else know the answer to my question above?

Thanks.

[taffer 948]

Normally these alloy hexes are pinched closed with the grub screw (which when overtightened can break) but the picture seems to suggest they are just tightened against the shaft.

When I had this issue on my rising fighter, I just bought multiple parts bags and / or the wheel hex's when listed under rising fighter, much cheaper then.

[slimleeroy 241]

I think due to these locking with a grub screw the pin would not be required

[Tony Sutton 8]

10 minutes ago, taffer said:

the picture seems to suggest they are just tightened against the shaft.

Yep, and I think that will work well for me. But been searching yesterday and today, all I could find was the pinched version of the nut.

Hopefully @Carmine A will respond soon to where I can get it from.

[berman 5315]

Just get some new spline hexes #9805337 and install new 4mm flange lock nuts. Otherwise, you have to get lunchbox axles for the pin hole, pins, and hex adapters. 

[Tony Sutton 8]

2 minutes ago, berman said:

Just get some new spline hexes #9805337 and install new 4mm flange lock nuts.

That's what I have ordered at the moment, but I'm keen to know about the one that Carmine suggested - it would give this longer life & more secure.

[berman 5315]

The lock nuts will only come loose if the wheels are repeatedly undone. 

While I don't doubt those hexes work screwing them into the spline on the axle, I would prefer to use the proper axle with the hole and pin, and then tighten the grub screw. The pin is designed to take the centrifugal force, not the grub screw. Completely up to you.

I have had 4 king cabs/monster racers, and 5 tractor trucks/trailers (low turn torquey motors + added weight) that use the spline and alloy nut design, if the nuts are tight, and the nylon on them is in good condition, they don't strip. 🙂

[Tony Sutton 8]

Thanks for your comment, @berman - that does make sense.

I'll wait for my order to arrive then give it a go with tightening them as much as I can and see how I get on. 

[Carmine A 2046]

On 7/19/2020 at 2:01 AM, Tony Sutton said:

@Carmine A That looks good, but would it mean I have to drill into the axle to fit the pin in? Or am I misreading to how it works?

You would only have to drill for a Pin if you wanted to... The clamping force would be more than enough to be secure. 

As for where, completely depends on where you live... But these types of Hubs are available everywhere, an pretty cheap too! 

Depending on which Hubs you get, the worst thing you'll have to do is to file down the splines on the Axles to provide clearance. 😉

[Carmine A 2046]

7 hours ago, berman said:

Just get some new spline hexes #9805337 and install new 4mm flange lock nuts. Otherwise, you have to get lunchbox axles for the pin hole, pins, and hex adapters. 

This would also be a great solution, if you wanted to go that route. The pins do help immensely with torque loads. 

The Hexes I suggested work great, unless you're going with crazy brushless power. They worked on my King Cab, for 2 Racing Seasons. They work because the aluminium is a bit softer, and if tapped onto the splines, the steel splines actually "bite in" to the Hexes just a little.

Either solution should work great! 👍👍