What is a hub dyno and why use one?
The roller or chassis dyno, whatever you want to call it is maybe the more traditional one, but why should you consider switching to hub dyno and why are they becoming more and more common these days?
The big thing is that the cars are getting more and more powerful and the power measuring limits of a roller dyno is the grip. Even with a knurled roller, good tires and proper strapping there is always some tire slippage and it becomes a problem somewhere around 600hp per axle.
But even though you are tuning only low hp cars there are a few things to consider.
In the hub dyno, the car’s wheels are being removed. The dyno is bolted to the wheel hubs using bolt pattern adapters.
This makes the hub dynos safer to operate as there is no risk for a blown tire or a snapped strap.
The driving speed on the dyno can be really high and not all the tires are rated for that. And with some racing tires it is even impossible to drive on the rollers, so bolting to the hubs is the only option with those cars.
“The accuracy of a hub dyno can be really high”
In a hub dyno there is significantly less inertia so it is possible to make the brake control very precise. It also enables the dyno to be sensitive to spot tiny changes in the engine like possible misfires.
Of course it sets higher requirements for the dyno controller as there is no inertia smoothing and filtering the measurements but when done well the data you get out is more informative.
Hub dyno does not require any permanent fitting or mounting so the initialization is easier.
The first thing in mind you might have is that it is time-consuming to connect the car to the hub dyno. In some cases, it might be faster to use the roller dyno, but with a hub dyno you don’t have to strap the car. It is bolted to the hubs and needs no strapping. (except some really powerful drag racing cars might need a frontal strap to prevent wheelie).
With a roller dyno you might also need to jack up the car and change tires before the run if it is a race car that uses some sort of special tires (like a rally car gravel tires or so) and with chiptuning up in the North where there are winter tires being used.
So in the end, if you tune a car or two in a day, there is really no difference in the use of time when connecting the car to roller dyno vs hub dyno.