2-wheel drive dynos and their limits

A 2WD dyno only measures power through two driven wheels, using rollers under one axle. That’s fine for a front- or rear-wheel-drive car, but it simply can’t properly test an all-wheel-drive vehicle without disconnecting drivetrain components — not ideal, and not always possible.

Why 4-wheel drive dynos matter

A 4-wheel rolling road, like our in-house MAHA unit, has rollers under all four wheels, measuring power delivery exactly as it reaches the road in AWD, 4WD, FWD and RWD vehicles alike — without modification or compromise.

Why it matters here: a large share of the performance cars on South Wales roads — quattro Audis, xDrive BMWs, Golf Rs — are all-wheel drive. A 2WD-only dyno simply can’t test these properly.

Roller vs hub dynos

Roller dynos (like ours) measure power at the tyre’s contact patch, which includes drivetrain and tyre losses — a realistic, real-world figure. Hub dynos bolt directly to the wheel hub and measure closer to the drivetrain output, typically reading slightly higher. Neither is ‘wrong’, but comparing figures between the two types isn’t a fair like-for-like.

Consistency matters as much as the hardware

Beyond the dyno type, consistency between runs — same operator, same calibration, same conditions — is what makes a before/after comparison meaningful. That’s something worth asking about wherever you book a dyno session.