Proper Bilstein 5100 Pre-Load?

[mrseth]

Hey guys and gals,

Awhile ago I upgraded from a Rancho 2.5" Quicklift to the Bilstein 5100s. I kept the springs that came with the Rancho kit and am using them on my Bilsteins. My question is- how can you tell or feel what proper pre-load is? When I hit ditches going 30-40, I smack my bumpstops pretty hard and the truck nose dives a bit under hard braking- should I go up a tier and increase my preload?

Thanks in advance!

 

[Daryl 32]

Pre-Load? not sure what you mean by this?

Do you have adjust able shock mounts?

5100 are not adjustable to my knowledge.

You either have the correct length stock for the suspension or you do not.

What I call droop is the ride height of the vehicle. To know how long a shock you need, you need to know:

Distance of top shock mount (chassis) to axle mount at full compression

And the distance of same point at full extension.

To protect the shock it should have about 1/2" more compression then the first measurement and about 1/2" to 3/4" more full extension length then the second. Most vehiches have bump stops for both direction of travel in the suspension, to protect the shock do not let it become either.

Where the shock travel sits at ride height will be based on the spring rates and weight of the vehicle.

There is no way to preload a shock as the dampening is what it is set by the manufacturer.

If you vehicle is bottoming out then I have say your springs may be not strong enough.

 

[smritte]

Adding to what @Daryl 32 said. Preload applies to springs. If you measure your spring, uninstalled and say its 18 inch's long. You install it and measure it with the weight on it and now its 15 inch, you have 3 inch of preload or tension.
The purpose of a shock is to control the speed of the suspension travel, the spring supports the weight.

When building a vehicle, you need to calculate how much shock you need based on suspension weight (unsprung weight). The shock converts this weight/speed ( kinetic energy) into heat. The shock not only needs to be able to control this energy but when the energy is converted to heat, it has to be able to dissipate the heat without overheating (boiling).
Unfortunately there is no perfect out of the box shock. The manufactures try to guess what your doing and valve the shock accordingly. Based on your description, you need stiffer shocks or more travel to allow the shock enough time to slow down everything.
Ideally we all should be running tune able shocks. Buy the size you need and spend a day tearing down and re valving. On my desert trucks that was what I did, on my Cruiser i found an out of the box, non tune able shock that works well with my weight and driving style.

 

[The other Sean]

So....

with an OEM style shock and OEM bumpstops, maybe don't be hitting ditches at 30-40mph?