Gen4 geometry thread is great, hoping to learn here.
Not suspention expert, but have tested several settings on racing Gen4.
Experts say (and they are correct) that there are 20, 50 or 100 "issues" and parameters all connected and affecting sportbike handling.
To name few: rider preference, riding style, tyres, level, weight. This all can set certail numbers to one or other extreme.
But I like numbers and what those "ballpark" numbers are, for example for average trackday frend.
These are few basics to think with Gen4:
*Shimming shock.
Good swingarm angle somewhere at 12 degrees. If it is too flat then rear compresses too much with acceleration.
If too much angle then shock extends "locks up", rear wheel wants to drive under engine.
At an optimal angle the rear suspention works midstroke (or upper mid) under acceleration, follows road and gives good contact and grip.
Measure your aftermarket shock length and spring preload before shiming as these measurements affect shimming directly.
Tyre sizes, front position, axle position affect this angle too somewhat.
*Wheelbase.
Longer wheelbase gives stability, but Gen4 has enough wheelbase and stability (due to much trail at front).
Tried to run axle almost all the way back with additional chain link and did not like it: made steering harder, numb and felt like I needed more lean angle to make same corner at same speed.
*Trail.
Gen4 has big trail number making it very stabile.
To go fast on race track you need to twist bars with much more muscle force than with CBR1000R or S1000RR having trail on other end of spectrum.
Shimming shock and dropping front reduces trail, but you get pretty quick to point where other problems surface.
This may win some 5mm trail, but cannot get to 100mm trail number this way.
I think that the only way TO TRY to make Gen4 nimble is with adjustable offset triple clamps, as this affect trail directly without spoiling other parameters too much.
Numbers: With race tyre, stock 26mm clamp and 25deg rake the trail is somewhere at 110mm.
Ducatis (like 1098, 1199) have similar big 24.5 rake, but triple offset of 36deg and popular mod was put 30mm clamps.
Early S1000RR had trail somewhere at 90mm (twichy) with steep rake and 32mm!! offset and benefited from offset at 28mm.
I'm not sure what adjustable offset camps will do to Gen4, but I will definetly try them this summer.
And clamps that will allow at least 30mm.
*Weight distribution.
Several problems when front or back too low or too high.
Rider body position and moving on the bike, training is important.
Besides maybe there is something special about Gen4 center of mass (engine position) that makes it get away with big trail, wheelbase and still steering reasonable, I dont know.
*Dynamic action.
Things like compressing suspetion too much, too little or moving rates way off.
If bike geometry is ok and you have problems at corner entry then its mostly fork problem and at exit shock problem.
Sping rates, preloads, rebound, compression are realated to eachother and without little experience bad settings are often seen.
Have help from profeesional if thinking to go fast on track. This saves tyre money, makes predictabel handling, safer and faster.
There is long Dave Moss video in Youtube (Suspension Tuning - Dave Moss Masterclass) explaings all the basics.
Not suspention expert, but have tested several settings on racing Gen4.
Experts say (and they are correct) that there are 20, 50 or 100 "issues" and parameters all connected and affecting sportbike handling.
To name few: rider preference, riding style, tyres, level, weight. This all can set certail numbers to one or other extreme.
But I like numbers and what those "ballpark" numbers are, for example for average trackday frend.
These are few basics to think with Gen4:
*Shimming shock.
Good swingarm angle somewhere at 12 degrees. If it is too flat then rear compresses too much with acceleration.
If too much angle then shock extends "locks up", rear wheel wants to drive under engine.
At an optimal angle the rear suspention works midstroke (or upper mid) under acceleration, follows road and gives good contact and grip.
Measure your aftermarket shock length and spring preload before shiming as these measurements affect shimming directly.
Tyre sizes, front position, axle position affect this angle too somewhat.
*Wheelbase.
Longer wheelbase gives stability, but Gen4 has enough wheelbase and stability (due to much trail at front).
Tried to run axle almost all the way back with additional chain link and did not like it: made steering harder, numb and felt like I needed more lean angle to make same corner at same speed.
*Trail.
Gen4 has big trail number making it very stabile.
To go fast on race track you need to twist bars with much more muscle force than with CBR1000R or S1000RR having trail on other end of spectrum.
Shimming shock and dropping front reduces trail, but you get pretty quick to point where other problems surface.
This may win some 5mm trail, but cannot get to 100mm trail number this way.
I think that the only way TO TRY to make Gen4 nimble is with adjustable offset triple clamps, as this affect trail directly without spoiling other parameters too much.
Numbers: With race tyre, stock 26mm clamp and 25deg rake the trail is somewhere at 110mm.
Ducatis (like 1098, 1199) have similar big 24.5 rake, but triple offset of 36deg and popular mod was put 30mm clamps.
Early S1000RR had trail somewhere at 90mm (twichy) with steep rake and 32mm!! offset and benefited from offset at 28mm.
I'm not sure what adjustable offset camps will do to Gen4, but I will definetly try them this summer.
And clamps that will allow at least 30mm.
*Weight distribution.
Several problems when front or back too low or too high.
Rider body position and moving on the bike, training is important.
Besides maybe there is something special about Gen4 center of mass (engine position) that makes it get away with big trail, wheelbase and still steering reasonable, I dont know.
*Dynamic action.
Things like compressing suspetion too much, too little or moving rates way off.
If bike geometry is ok and you have problems at corner entry then its mostly fork problem and at exit shock problem.
Sping rates, preloads, rebound, compression are realated to eachother and without little experience bad settings are often seen.
Have help from profeesional if thinking to go fast on track. This saves tyre money, makes predictabel handling, safer and faster.
There is long Dave Moss video in Youtube (Suspension Tuning - Dave Moss Masterclass) explaings all the basics.
