Parallel Engineering

16/12/2025

A customer brought in their MK3 Commando to go through the frame/rolling chassis wheel alignment process. He was aware of serious rear wheel mis-alignment. I discovered the rim offset was approx 1/2" from where it should be and recommend a new rim with spoke hole angles drilled to suit a MK3 Commando rear hub. He took the wheel back to the Centrally located Wheel building establishment where the wheel was originally built. I was surprised when the wheel was returned with the same rim. The offset was now in the right ball park but all the drive side spokes now feature a double/s-bend. Wheel spokes are designed to work in tension and therefore must be straight along their length.You couldn't make this up.

08/06/2025

Triumph T150 after rolling chassis alignment. Note the sub-frame is not symmetrical to the frame centre line. Anyone know why? I'm assuming it's because the frame originally housed a twin engine and needed modification for the 750 triple.

09/04/2025

I have become aware that some riders think there's no benefit from precise motorcycle rolling chassis alignment because they do not ride a race bike.

It's a fact that due to the natural frequency of components and assemblies resonance can occur when in motion due to applied forces which, in the case of a motorcycle, is the cause of steering wobble which can and does lead to 'tank slappers'. This can occur at high and low speeds. Steering dampers treat the symptoms, not the cause.

11/03/2025

As promised, news of the first oil change since ditching the one-way reed valve engine breather and re-installing the Norton Mk3 breather; after 3,000 miles no detectable emulsified oil out of the crankcase or oil tank! (I was thinking of including a photo of the used oil but probably should have done a video... perhaps). At any rate I wont be fitting a check valve to any engines breather system in the future. I'm aware a few Commando owners have fitted the very expensive (approx. £300) CNW reed valve, one reason because their oil pumps let-by resulting in a crankcase full of oil. They'd be better off sorting out the cause than treating the symptoms.

23/01/2025

A short ride out in the summer.

20/01/2025

After running a one-way reed valve for several years on my Mk3 Norton Commando I noticed an increase of emulsified oil in the oil tank and sump during oil changes where there had been very little before. Being aware of the negative crankcase pressure the pistons are working against on the power and exhaust strokes, I decided to re-fit the original breather design. The breather is connected in between the oil tank and air filter. A hose connects the timing chest to the oil tank. On the inlet stroke the descending pistons push crankcase gases into the oil tank air space and at the same time create a vacuum in the air filter which draws the gases from the oil tank into the combustion chamber. As the system is open to atmospheric pressure on the compression and exhaust strokes there is no vacuum in the crankcases. A recent 400 mile round-trip to Devon has shown a slight improvement in mpg and no noticeable change in oil consumption which averages at 1000 miles/pint. I expect a reduction in emulsified oil and will post the results at the next oil change.

11/01/2025

Torque is a rotating/twisting force. A Norton Commando's rear wheel spindle is recommended to be tightened to a torque of 80lbft. You can achieve this by using a spanner 1ft in length and applying an 80lb weight at the end of the spanner. Using a spanner 2ft in length and applying a 40lb weight applies the same torque.
A motorcycle is kept upright and stable at speed by the gyroscopic forces generated by the front and rear wheels. When the rider causes the bike to lean into a corner this generates a torque along the line F-R (see diagram below) because (on a Norton Commando) F-R represents the connection between the front and rear isolastics via the cradle, which also connects to the rear wheel swing-arm and also connects to the engine.
As the bike is leaned a force is generated at the engine head steady connection T to the frame. A perpendicular line from the pivot F-R to T has a length approx. 16" and is the same in principle as when a spanner is applied to tighten or loosen the rear wheel.
Several Norton Commando owners advocate fitting an additional isolastic mount at the point marked 'New' on the diagram. A perpendicular line from the pivot F-R to 'New' has a length of approx. 8". If the torque generated along the pivot F-R has a value of e.g 200lbft, then at point T the force would be approx. 150lb (T to F-R is approx. 16"). The Force at point 'New' would be approx. 300lb as length 'New' to F-R is approx. 8".
Therefore I conclude there's no advantage whatsoever fitting an additional under gearbox iso mount. There are a bunch of idiots on AccessNorton suggesting to remove the head steady altogether which will probably lead to cracked frame tubes. The designers got it right with the original positioning of the iso's and the fact Peter Williams never incorporated an additional iso on his record breaking, TT winning Norton Monocoque racer is proof of the original concept.

Precision frame alignment service correcting manufacturing mis-alignment of classic
motorcycle frames and rolling chassis. Norton Commando specialist.

23/11/2024

First part of the alignment process is setting the frame centre line parallel to the surface table and making sure the swing-arm axis is perpendicular to the steering head axis.

17/11/2024

Getting the rear wheel central. Click on the photos for more info. www.parallelengineering.co.uk

09/11/2024

Norton Commando frame going through the first stages of the rolling chassis alignment process. Click on photos for more info. www.parallelengineering.co.uk

15/08/2021

Two photos showing the before and after of the latest bike to be in the workshop to go through the alignment process is a 1971 750 Norton Commando. There was additional engine and transmission work and generally putting things right.