RADBUL: Balancing Form With Function
Shock & Awe

It might only be a few weeks since our last Project RADBUL update, but with lots going on since Mad Mike Whiddett dropped a major bombshell, you can bet I’m making more frequent visits out to Townsend Brotherz Racing’s (TBR) Metal House Compound to keep up to date with the build’s progress.

So let’s catch up on what’s been happening at a small workshop – where big things are going down – in Auckland, New Zealand…


In case you missed it, that bombshell was the decision to switch from a single turbo three-rotor 20B engine package, to a custom four-rotor 26B with two turbos burning octane-rich E85. This new engine should be good for somewhere in the vicinity of 1,200hp on low boost.


High boost? We’ll have to wait and see… But Kaz is making rapid progress, and loading the completed chassis on a trailer and pointing it in the direction of Pulse Performance Race Engineering (PPRE) where some insane power will be added, is now only weeks away.

In this update however, we’re going to touch on two of the most critical aspects of the build: suspension and steering. After all, a four figure power output isn’t much use if the car its stuffed in hasn’t got the handling attributes to back it up – something more important than ever when you’re dealing with a little NC Mazda MX-5 with a 90.2-inch wheelbase and a projected race weight of just 1,000kg.


Given what we’ve seen over the course of the project, there’s been absolutely no compromise made on quality. So on my last visit out to the TBR workshop a couple of days ago, I wasn’t at all surprised to see this special delivery from KW Suspension‘s specialist Race department added to RADBUL’s ever-growing parts supply.


It doesn’t get much better than custom-made purple and yellow coilovers at all four corners, and the 3A Competition based kit that KW’s technicians pieced together for the Mazda is proven pro drift hardware.


Similar to the race-specific units built for the Toyota 86-X driven by Mike’s fellow Speedhunters team driver Fredric Aasbø, the 3As feature a mono-tube construction with three-way damper adjustability on top of adjustable ride height.


That’s rebound adjustment through the piston rod tops, and both bump/compression adjustment and high and low-speed valving adjustment through the separate reservoir canisters. In practice, this means the ability to fine tune the setup depending on the track type and surface. On a high-speed course for instance, upping the compression and rebound will increase stability.


As you would expect though, the KWs aren’t the only non-factory part in the greater suspension setup. Here we see TBR’s custom-made adjustable A-arms, and the makings of a not-so-factory-looking knuckle…



Like in any race car build, performance is key when it comes to the steering system. Running off the suede-wrapped Sparco wheel is a modified FD3S RX-7 collapsable inner steering shaft housed within a TBR outer.


A PG Hydraulics modified rack with a few tricks going on inside is used too… But it’s the amount of steering angle that largely determines how sideways you can get. Therefore, when it comes to competition drifting, it’s all about the steering lock.


In both Mike’s RX-7 and RX-8, extra lock has been achieved through modifications made to the factory steering knuckles. This is a common upgrade that works well, but it doesn’t come without compromises – specifically an overabundance of caster and KPI (kingpin inclination) at full lock, which has a negative effect on handling.


The solution? Custom made knuckles of course – calculated on the required geometry, then designed in-house by Kaz using CAD software. Many of RADBUL’s parts have been fashioned this way, which goes to show the extent of this build.


This is TBR’s Prototype V1.0 knuckle in its tacked-up state. It’s got some cool design details, including notches in each individual laser-cut piece that allow it to simply clip together prior to welding. More importantly, the design also includes a 45mm drop, which essentially lifts the wheel and tyre higher up into the bodywork, effectively lowering the chassis by the same amount. So the car will sit low – a non-negotiable prerequisite from Mike – but still maintain the correct suspension geometry.


And then there’s the lock. Lots of it. With all that power and this much angle, well… I’ll let you draw your own conclusion.


On top of the knuckle welding there’s still a little bit of finishing work to be done, but for the most part this is how the front end will look in its completed state. As you can see, the lower control arm is a custom-fabricated (and adjustable of course) TBR component as well.

Back-End With Bite

In the last update I showed you the Winters Performance quick-change diff assembly that had been pieced together by Autosport Dynamics (ASD) in the USA before being shipped down to New Zealand. Here it is, now adapted into the MX-5 factory rear subframe and sitting up underneath the car. It’s an impressive sight.


I also mentioned the axles, or more precisely these heavy duty units from The Driveshaft Shop. Built from aerospace-grade material, the bars feature large splines, long through-bolts from ARP and Porsche-style CV cups. Supplied with hubs to suit, there should be no trouble putting all the power to ground.


Early on in the build it was discovered that the many of the aftermarket suspension parts that Mike uses in the RX-8 were a straight bolt-up in the MX-5. With a modified hub carrier in the mix, fitting out the rear end is a pretty straightforward proposition.


Kaz comes from a speedway background and before he launched TBR he spent the better part of a decade building championship-winning midget and sprint cars for local and international teams. Over the past two years he’s applied a lot of that setup know-how to Mike’s other cars, and the results pretty much speak for themselves. You can have the best parts money can buy, but if they’re not working in unison at their maximum potential, there’s little point, right?


The two main factors Kaz is concentrating on at this end of the car are side and forward ‘bite’ – something that can be achieved through fine tuning of the KW coilovers and a full course of adjustable Megan Racing arms. With wide and sticky Nittos tyres fitted up, RADBUL should have plenty of grip.


Before the the bare shell is sent away to be painted, there’s still plenty of work to be done, including a lot of the fiddly, time-consuming stuff. Solid progress is being made on a daily basis though, and only two days on from this visit, I’m already due back out at TBR for the next one.

Once again, we’ll wrap this update up with another freshly brewed episode of The Making of RADBUL from Red Bull. More on this crazy build coming very soon!

Brad Lord



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Damn that differential looks beast and belongs on this wild ride. 
Again all that horsepower and small body, the suspension choice was spot on and now all you need is some fighter jet harnesses to really keep you strapped in. 
Lovin the progress here and awaiting the final stage.


Can't wait to see the final result Mike. Hopefully you'll be using a stock facelift bumper, just to have that "grinning face" while the car goes sideways. That would cause a lot of laughter to the audience. :D


Woah ! I love that steering knuckle , it looks so simple yet it's effective (I think) ! I really love the fact that , the knuckle is just a few piece of cut-out steel plate & weld together afterwards , instead of CNC a whole thing from a block of material !

JMax Paint Garage LLC

Never fails to impress me. Gosh I wish I had all that equippement to build fun things like that! (;___ ;)


With a power to weight ratio of about 0.55 this MX-5 is going to be very, very fast! Can't wait to see the smiling, grinning beast soon Mike. Keep up the epic work with the rotary cars and epic drift cars! ;)


I've got the Weirdest boner right now!


0 compromises. Gonna be a ridiculously competitive rig.


PandaSpeed Hi there Kevin, we're very sorry to hear about this, and obviously there's no way you should be waiting that amount of time for your product to arrive. Please resend all the details to  and CC our Community Manager, taryn@speedhunters.com and we will get this sorted for you immediately. Thank-you


I don't get it, why is a supposedly professional grade build using a spherical rod end in bending on the fabricated lower control arm? It is generally considered a serious "no no" in vehicle suspension.
I would be interested if the guys involved in the design could explain or justify this decision.


@Guy 2nd'd.


awesome, a complete new rebuilt. just like christmas =)


@Guy Thank you.  They are all over the place.


@Guy I'm not involved in the build in any way at all, but I'll answer the question as to why sometimes rod ends are used in bending configurations. If, and only if, a fabricator or designer can guarantee that the range of motion on the rod end will not be exceeded during the cycling of the construct (in this case the suspension) then it's OK to use it this way. Likely the suspension bump and droop stops will dictate this range. It's not uncommon to see formula cars with rod ends configured in the same manner.
This is my .02 FWIW.


This is nucking futs............. love it :)


insane build.. absolutely nuts.. my main problems is that really fucking annoying auto-playing video at the bottom of the page.. please disable the autoplay or at least have it muted.. if i want to watch the video i can press play myself thank you very much


marshalljung I don't think Guy was referring to the range of motion of the rod end dude; the resulting force system on the lower control arm due to the reactions of the wheel and coilover will literally want to bend the rod end at the point where the thread enters the arm and it will eventually fail because the root of the thread acts as a stress raiser. This guy has amazing fabrication skills but being a good fabricator doesn't make you a good engineer.


@Guy While it is preferred for a-arm tubes to be straight such that load transfer takes a linear path from the upright into the chassis and your stresses are then tensile and compressive only, sometimes packaging constraints force you into another solution.  Looks like the factory pick-up points are being used on the chassis and are not wide enough for the a-arm tubes to take a straight path around the dampers.  That being said, this looks to be the upper control arm which sees much lower stresses compared to the lower control arm.  Provided the tubes in the upper control arm have enough material wall thickness, a 'bent' design can be adequate enough to handle the expected loads - .  Although not as efficient as a straight load path, the only compromise here is a heavier upper control arm then what might otherwise be possible.  Plus the designers can feel good as the upper control arm is not as critical a component as the lower control arm with respect to load transfer from the tire contact patch.  No free lunch in suspension design!



Time to BURN SOME RUBBER.........................................

"nough said".


i predict in 5 years Mad Mike will own all 4-rotor motors in existence.


No one is talking about the upper arm. 
the lower pick up on the upright is a rod end. It is convention to use a ball joint or enclosed spherical bearing.
Some amateur racers use rods ends in this position. And they often break.

@Guy   All i can think of is that they are using the rod end because the geometry they are trying to achieve is causing a packaging issue.

I.E Mad Mike loves low/negative offset wheels, so to reduce the scrub radius they need the pivot "inside" the wheel, 
no idea though why they cant just use a ball joint in single sheer like everyone else.
OR just change to strut which seems like a much better arrangement for a drift car.
Everything else looks sounds/awesome, but this is really strange. I mean i'm sure they can just replace them each meeting but i don't need the reason.


Awesome build. I'm not a huge fan of the rotary but I can definitely still appreciate it. Looking at a 4-rotor engine reminds me of an old steam locomotive. Cool to see all of the custom parts made too.




@Brent marshalljung I understand the reaction forces in x,y,z on the outboard lower control arm-hub mount. There are various ways of doing this attachment, some better than others. Here is some of Mad Mike's potential competition:

It is this better? MacPherson car, but still...single shear with a nice moment arm...
I'm just saying that there are good and bad ways of mounting this point, and a rod end with a thick enough diameter of appropriate material in double shear is probably OK on a lightweight car.


And then a mazda2 for rallycross! The xbul or something like that, please!


Speedhunters Confirmation received, Post deleted.


marshalljung No, if anything that BRZ is worse, not only is the outer lower control arm spherical in bending but the front inner control arm sherical is now also in bending under any lateral loading or brake reaction force loading.
It's not about double or single shear on the bolt going through the spherical, its about bending the threaded shank of the spherical rod end itself. The threaded part should not be in bending.


Megan's come a long way from using poor kids as testers for its products.


Now THIS is a build! Why doesn't SH post more articles like these? I'm sure most people, including myself are getting tired of non-functional stance and Rocket Bunny-type builds.