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ride heighth strain on front suspension [message #161372] Fri, 24 February 2012 09:38 Go to next message
skip2 is currently offline  skip2   United States
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I know this has been dicussed before about too high of heighth in rear will cause undue strain on front suspension particularly TB's and sockets during braking. The standard protocal as I understand is to set the bogie centers and the wheel hubs in alignment with each other. I yet to find this and can get the factory measurement at the hole in the frame. I had an experience years ago with a man I worked for in the 70s who had a Buick Electra (land yacht) with air shocks that he ran around with back end way up in the air. Florida had auto inspection at that time and he could not get his back brakes to hardly show anything on the brake tester but he would max out the front. After alot of repair and failing 2 more test I suggested putting the car back to normal ride heigth and it passed fine. This was with front disc and rear drums. This all leads to, would it make since to run the rear bogies a little lower than the rear hubs so as to make the braking inertia move in a lateral direction instead of a downward pressure on the front end which my story demonstrates when rear ends are to high on vehicles. I think someone also actually had some pressure figures when the rear end is to high. I run P225/75R16's on Alcoa rims. Sometimes I can take a long way around to get to a point so I thank you for your patience in reading this and some possible ideals or comments.
Thanks again
Skip


74 Canyon Lands, FiTech, 3.7 FD LSD, Manny Tranny, Springfield Distributor, 2001 Chevy Tracker Ragtop Towd
Re: ride heighth strain on front suspension [message #161377 is a reply to message #161372] Fri, 24 February 2012 10:17 Go to previous messageGo to next message
bwevers is currently offline  bwevers   United States
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Skip,
This cannot be true:
"The standard protocal as I understand is to set the bogie centers and the wheel hubs in alignment with each other."

The wheel hub is 15" above the ground with a 30" diameter tire. The bogie pins are 9 to 10 inches above the ground (normal ride height). So the difference 15 minus 10 = 5 inches. Therefore the bogie arms cannot be level. They angle upward.

I believe you are correct that a lower ride height in the rear will reduce weight transfer to the front.

Regards,
Bill


Bill Wevers GMC49ers, GMC Western States 1975 Glenbrook - Manny Powerdrive, OneTon 455 F Block, G heads San Jose
Re: ride heighth strain on front suspension [message #161378 is a reply to message #161372] Fri, 24 February 2012 10:24 Go to previous messageGo to next message
skip2 is currently offline  skip2   United States
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Registered: September 2011
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The increased air pressure would raise everthing including the bogies.Skip

74 Canyon Lands, FiTech, 3.7 FD LSD, Manny Tranny, Springfield Distributor, 2001 Chevy Tracker Ragtop Towd

[Updated on: Fri, 24 February 2012 10:27]

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Re: [GMCnet] ride heighth strain on front suspension [message #161418 is a reply to message #161372] Fri, 24 February 2012 19:51 Go to previous messageGo to next message
USAussie is currently offline  USAussie   United States
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Location: Sydney, Australia
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Skip,

To set the ride height I suggest you download a copy of Maintenance Manual
X-7525 from here.

http://www.bdub.net/factory-manuals.html

Once you do that go to Section 4 - Rear Suspension / Page 4-34 - Ride Height
Adjustment. You will see Fig. 70 - Checking Vehicle Ride Height which shows
the slots in the frame and specifies "REAR RIDE HEIGHT 11 11/16"'+ 1/4."

I believe once you follow the procedures in the manual you will find that
this picture shows the alignment of the spindle and bogie pivot centers.

http://www.gmcmhphotos.com/photos/showphoto.php?photo=41971

Regards,
Rob M.


-----Original Message-----
From: Skip Hartline

I know this has been dicussed before about too high of heighth in rear will
cause undue strain on front suspension particularly TB's and sockets during
braking. The standard protocal as I understand is to set the bogie centers
and the wheel hubs in alignment with each other. I yet to find this and can
get the factory measurement at the hole in the frame. I had an experience
years ago with a man I worked for in the 70s who had a Buick Electra (land
yacht) with air shocks that he ran around with back end way up in the air.
Florida had auto inspection at that time and he could not get his back
brakes to hardly show anything on the brake tester but he would max out the
front. After alot of repair and failing 2 more test I suggested putting the
car back to normal ride heigth and it passed fine. This was with front disc
and rear drums. This all leads to, would it make since to run the rear
bogies a little lower than the rear hubs so as to make the braking inertia
move in a lateral direction instead of a downward pressure on the front end
which my story demonstrates when rear ends are to high on vehicles. I think
someone also actually had some pressure figures when the rear end is to
high. I run P225/75R16's on Alcoa rims. Sometimes I can take a long way
around to get to a point so I thank you for your patience in reading this
and some possible ideals or comments.
Thanks again
Skip

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: ride heighth strain on front suspension [message #161433 is a reply to message #161372] Fri, 24 February 2012 21:40 Go to previous message
Bob de Kruyff   United States
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
Senior Member
skip2 wrote on Fri, 24 February 2012 08:38

I know this has been dicussed before about too high of heighth in rear will cause undue strain on front suspension particularly TB's and sockets during braking. The standard protocal as I understand is to set the bogie centers and the wheel hubs in alignment with each other. I yet to find this and can get the factory measurement at the hole in the frame. I had an experience years ago with a man I worked for in the 70s who had a Buick Electra (land yacht) with air shocks that he ran around with back end way up in the air. Florida had auto inspection at that time and he could not get his back brakes to hardly show anything on the brake tester but he would max out the front. After alot of repair and failing 2 more test I suggested putting the car back to normal ride heigth and it passed fine. This was with front disc and rear drums. This all leads to, would it make since to run the rear bogies a little lower than the rear hubs so as to make the braking inertia move in a lateral direction instead of a downward pressure on the front end which my story demonstrates when rear ends are to high on vehicles. I think someone also actually had some pressure figures when the rear end is to high. I run P225/75R16's on Alcoa rims. Sometimes I can take a long way around to get to a point so I thank you for your patience in reading this and some possible ideals or comments.
Thanks again
Skip

Skip--after the dust settles, I have to say that the wheelbase on the GMC is long enough that the amount of travel you can get on the rear suspension will have minimal effect.


Bob de Kruyff
78 Eleganza
Chandler, AZ
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