Review - Zen Racing 1/12th Positive Lock Diff Hub Kit

As mentioned in my previous review of the Xenon front suspension for my Tamiya RM01X, multiple World Champion David Spashett has joined the company. This new diff hub kit is one of the new innovations he has developed, and hopefully more will follow.

The basic design for a 1/12th diff hub has been around for many years in its current state, since the introduction of three bolt wheels. There have been minor variations to save weight or add strength on the non drive side, and the diff side has become narrower to balance brushless motors, but nothing major has changed. Even the Yokomo type are just a longer version of the same basic design to accommodate the Yokomo wheel. The Zen Racing team have taken a good look at what is required of the hub components and come up with some innovative detail changes that make the components stand out. The parts are available as a kit for the diff hub components, with a full spare set of screws, or individually. The thrust race assembly is a separate item.

Diff hub first. This is of the now common narrow design to fit the current crop of Lipo cars. The first and most obvious change you will notice is that there are 3 lugs where the bolt holes are normally located. These are tapped out to accept a 2.6mm bolt. The philosophy is that the wheel locates positively on to these lugs allowing perfect alignment of the wheel every time. No more wobbly wheels due to slack around the bolt holes. The bolts require a 2mm or 5/64" Allen driver to fit, which is now one of the most commonly used drivers since the majority of manufacturers went metric. If you are running one of these cars, or plan to, you no longer require that 3/32" driver that was reserved just for the wheel bolts. One other advantage of the lugs is that it is now difficult to overtighten the bolts and distort the wheel. This could result in binding of the diff if the plastic distorts and clamps the wheel bearing.

I have run a Slapmaster thrust race on my diff for years to give consistent performance. This removes the side load on the outer diff ballrace which was not designed to take a side load. This ballrace would eventually deteriorate and the diff would become rough. The Slapmaster came with a plastic spacer shown above (left). The Zen hub is slightly shorter than the IRS hub I have been running, so the Slapmaster spacer would not fit. The spacer on the right is longer from the Zen Racing thrust race kit, and is machined alloy. This fitted perfectly. It actually gave a lighter diff action too as I did not have to tighten the diff so much to overcome any compression in the plastic Slapmaster spacer.

The non-drive hub also has been altered form the commonly seen IRS and Associated design. The amount of material in the clamping area is significantly larger. This will reduce the chances of the clamp material cracking resulting in the hub slipping on the axle. This is welcome news as I have retired on a number of occasions due to this. The clamping bolt runs down really freely with no binding, and the hub clamps up very easily. Much nicer than any previous hub I have used. There is also a spider assembly, shown fitted below. The idea behind this is to help balance the weight of the rear axle resulting in equal drive from both rear wheels. It also makes fitting the bolts a lot easier as you just drop the spider in fully loaded with the bolts, and run them down.

Now, the big question is will this instantly make you a winner? My opinion? No. But will it stop you being a loser from having an unbalanced car as your wheel is wobbling as you've bolted it up off centre, or your axle has pulled out of the hub. A big fat YES. And to have the best chance of winning you need to be in the race at the end and have a car built with the least amount of errors. Zen Racing say it themselves - the aggregation of marginal gains.

You can buy this from Zen Racing here