| My thoughts on the rear ride height [message #359175] |
Sun, 04 October 2020 07:38  |
 |
RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma:
|
Senior Member |
|
|
The GMC ride heights are set so the rear sits about an inch lower than the front. This is my take on why this is so.
I don't believe it has anything to do with getting maximum caster. An inch change in the rear height only changes the front caster by 1/3 degree. This isn't up for debate, its simple math. Caster recommendations are all over the place, but most agree more caster the better up to about 4 degrees or so.
My thoughts are the rear height has to do with stability of the rear bogie arms. When the rear is set to the recommended ride height, the rear axles (if I am allowed to call them axles) sit about an inch higher than the bogie pins. I'm thinking with the bogie pins sitting lower than the wheel axles, the bogie arms are more directionally stable, like laying in a hammock. The bogie pins carry the rear weight of the coach. My senses tell me that the rear suspension is more stable when the bogie pins are below the wheel axles.
When you raise the rear, the bogie pins become level or above the wheel axles. Once the bogie pins are close to level or above the wheel axles, the bogie arms (especially the front arm) become directionally unstable which makes the rear of the coach squirrely. The higher the bogie pins are above the wheel axles, the more directionally unstable the bogie arms become (to a certain point).
If one was to mount the bogies lower on the frame (with the necessary frame work), you could raise the rear of the coach while maintaining the lower bogie pin configuration and maintain the desired stability.
Just my farmboy mechanic way of seeing things.
What say yeh?
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
