Racing a Suzuki X7 against 3 other X7s I could not only feel the frame flexing I could see the others flexing too, it was a harmonic thing in the steering head.I can recall early Japanese bikes with frames you could feel flexing under you. Not to mention US bikes apparently made of cast iron by the weight and a remarkable aversion to going around corners. Russian motorcycle tyres were so, um, 'durable' that Czech ones were a vast improvement. Or the MZ motorcycles with superb engineering but shifting cores in the aluminium brake drums that either gave you 'retarding devices' instead of brakes or 'on/off' switch brakes. Excellent when fettled and with Avon tyres.
However, we digress.