In the mid Seventies and into the Eighties, I tried my luck at the Bonneville Salt Flats with a Twin. The plan, originally, was to have something on the bike from all of the Series; A, B, C, D. Not much I could use from an A other than a few nuts and bolts, but I did have Bramptons and a B oil tank. To make a long story short. The Bramptons were unable to cope with anything over the mid 120's and they'd go into a speed wobble. I swapped spring rates from 140 lbs to 180 lbs, no better. I even tried a different rider, Bob Bakker (look him up in the AMA Hall of Fame) and he had the same results. This was all before they had a Vintage Class for Vincents so I was running against a 154mph record on petrol. The rules stated where the foot rests had to be and your feet had to be on them at all times. We finally agreed, those who'd gone over 125 with Bramptons had always layed on the rear fender or otherwise transfered the weight off the front. I finally replaced them with Girdraulics and on the very next run the bike handled perfectly. I think I wasted at least two years at the Salt Flats trying to make Bramptons work. Even today, there are people who are attaching hydraulic shocks to their Bramptons in an effort to make them more useable, I have one on my B. Sorry, Brampton lovers, but in stock form those forks will not only beat your arms off on a twisty back road, they are incapable of proper rebound action at high speed. They sure do look pretty though.
Cheers, John