| One ton spacer debate answered [message #338064] |
Mon, 22 October 2018 10:26  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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There is much concern regarding the spacer used on the one ton front end.
GM/chev used the same front hub for both single wheel and dual wheel pickups. The rim offset for the single wheel pickup rims was either 13mm or 17mm (my investigation shows both but 4mm = 0.15" so it is immaterial) The rim offset for the dual wheels was 127mm. So to bring the dual wheel back to the same position on the hub as a single wheel rim you need a spacer.
127mm - 13mm = 114mm which is 4.48". So a spacer of ~4.5" puts the dual wheel rim at the same position as the single wheel rim on the front hubs. This is why GMC/Chev used a spacer on their dual wheel pickups. Otherwise they would have needed a different front hub for the single vs dual wheel pickups. Or they could have used 13mm (single wheel) offset hubs on the front meaning you would have different hubs for the front and the dually backs.
As far as the change in position of the upper control arm, yes it's true the upper control arm's mounting point on the one ton hub is higher than OEM. However unlike that of a pickup truck or an automobile, the loading of the motorhome's front suspension changes very little in real world use, . Therefore the front suspension position moves very little, maybe +/- 1". Therefore the front wheel geometry will not change very much in real world use.
I guess the ideal solution would be if new knuckles could be cast with the upper control arm mounting point in the same position as the OEM.
Just my farmboy shade-tree engineer/mechanic way of seeing things. Please note I am not an engineer or mechanic nor have any claim to any expertise about anything.
I'm very happy with my one ton installed in 2010 and I'm not going back.
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
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| Re: One ton spacer debate answered [message #338089 is a reply to message #338064] |
Wed, 24 October 2018 09:50  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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The only time I feel some torque steer is when one tire spins under acceleration from stop on wet pavement etc. But all my front wheel drive cars do that too. I don't feel any pull to either side under heavy braking.
I'm away so I can't measure the size of my spacer, but in Karen's one-ton installation instructions she says it is 4.25" I suppose the spacer depth could be reduced a bit, limited by the clearance to the brake caliper.
There are ten's if not hundred's of thousands of GM and Chev 1 ton trucks out there for the past 30 years running this configuration, so it can't be that bad.
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
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