Suspension sorted
Adam Smallman has been on a suspension set-up course. This is what he learnt…
GARETH EVANS cut his teeth as a race mechanic - Old Spice Ducati, Loctite Yamaha, Crescent Suzuki, Honda Britain - and now runs the Motorcycle Suspension School from his Reactive Suspension workshop near York. That senior people from Dunlop, BSB mechanics and an off-road KTM mechanic from Israel had showed up tells you about the man’s pedigree. These are my ten outstanding observations from the £110 day.
1 Tune the front for entry into a corner and the rear for exit. 2 Adding preload can, counter intuitively, make a rear shock softer. It’s down to the linkage ratios and the equilibrium point between rider weight and spring force. A spring preloaded 13mm with a 75kg rider onboard would hit equilibrium at 35mm of wheel travel, Gareth explains. Set preload to zero and that point moves to 63mm, where the spring rate is higher. Try it. 3 Rider sag – the amount that fully-extended suspension (wheel off the ground) is compressed when a kitted rider is in position on the bike with feet on the pegs – should be around 35mm each end. Static sag – the difference between unweighted suspension and the bike-only sitting on its suspension – should be 25mm at the forks and 10 12mm at the back. Less than 10mm on the back and you’ll rip up your tyres, more than 12mm and you’ll feel a lot of movement on exit. If you can’t get these numbers the spring is wrong for your weight.
4 Big piston forks generate damping too quickly: ‘People go for a ride and come back knackered because they’re putting the effort in and the bike isn’t doing the work,’ Gareth says. 5 Lowering kits for short riders are a disaster. The seat’s lower but damping ratios have changed too. 6 Hammering in axles can knock fork legs out of alignment. 7 Identical tyre sizes from different brands can vary by as much as 10mm in ride height. Track riders should compare fully inflated tyre circumference. 8 Many trackday riders use too much rebound damping. ‘The less rebound the better,’ Gareth says. 9 Tight spots on chains screw up suspension performance. Replace. 10 For many Doritos-fuelled riders, standard springs are too soft.
Alongside these set-up days, Gareth is launching a new specialist Race Engineering Course, 10-11 August. For £720 the two days bring together suspension, tyre and chassis experts. e-mail info@reactivesuspension.com or call 01347 811 529.