Honda Motorcycles - FireBlades.org banner

1 - 6 of 6 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter #1
I just learned @ school that spring preload doesn't effect the stiffness of the spring, only the ride-height. I'm still a little confused, even after my instructor tried to explain it to me. It seems to me that if you compress a spring and hold it there, it will be stiffer to movement. Any thouhts on this, those of you with technical knowledge?
 

·
Premium Member
Joined
·
6,731 Posts
Yup, what G-force said. The preload adjustment on your bike is used to set sag, which is how much the bike sags when you sit on it. That's oversimplifying; if you want to know how to set the sag, do a search or ask and we'll go into that. If your spring is too soft for your weight, it will sag too much, even if preload is maxed out. Conversely, if the spring is too stiff for your weight, you won't be able to get the bike to sag enough, even with preload on the softest setting. The sag on the front should be around 35 mm and the rear should be around 28 mm.
 

·
Registered
Joined
·
1,524 Posts
Once you have the correct rate spring in the bike (for rider/bike weight) you the set sag, usually 1.25 in. either end. Then you can change ride height (move forks up/down, legnthen shock, =/- washers etc) They are totally different.

Spring rate is what it is. If it's 100 lb/in that means to compress it 1 in. you push 100lbs on it, 2in, 200 lbs etc. It feels harder once its pushed in but the rate is the same. Progressive springs are wound to have at least 2 rates. i.e. 80lb/in for 1st 1in and 105lb/in thereafter. So riding around town gives a softer 'feel' and once you load up the spring (like brake/accelerate hard) it stacks the coils in the lighter area and now works on the heavier area. Sounds good dosen't it? Problem is there is no soloution to every situation for weight/riding style etc with these springs. Best way to set up is the correct straight rate spring for your weight/bike, set correct sag then then set the damping to your preference.
 

·
Registered
Joined
·
441 Posts
To give an example of how the spring rate works. Take a car that weights 2000 lbs. Manufactures put 100 lb springs on it to hold it up. Now if the springs were just long enough to fit the shock, the car would slam into the ground. But they preload them with a spring compressor 3 inches so that they hold 300 lbs before it's even put on the ground. When it's on the ground it compresses another 2 inches(kinda like sag). Now the springs are at 500 lbs each, 2000 total, but it only takes another 100 per corner to make it drop another inch. It makes for a nice soft ride.
 

·
Registered
Joined
·
44 Posts
Discussion Starter #6
OK, I understand more now, it might 'feel' a little stiffer, but the spring rate is the same. I found that my fork springs are too soft for my chunky American ass, need to upgrade to get correct sag. I set my rear spring at about 33mm of sag for street duty, but front is at least 40mm with preload maxed out.
 
1 - 6 of 6 Posts
Top