Dave wrote: You are absolutely correct that the steering geometry (and
suspension
geometry) will be changed and this is a major concern. For example, the
ball
joints and A-arm bushings will see higher loading in the plane parallel to
the ground. I mentioned before that the torsion bar will receive higher
torsional stress. Torque steer will probably become more noticeable and
there
is a host of other effects that will have to be looked at and maybe the
conclusion will be that it is just not worth it.
Even if we conclude that a change may be beneficial, chances are that
there
is not a wheel available with the offset we need. But at least we will know
something. Either the factory offset is optimal or it isn't. Whether we can
do something about it or not is another subject.
Dave, (and now Brent), I think that you have it basically correct here. I
have no expertise in the theoretical pro's and con's of this issue but I do
have a bit of experience. There are at least a half dozen people who have
run a fair number of miles on the wide rims. Mike Mayo in Colorado has (I
think) around 20,000 miles on his coach (I tried to call him to confirm the
mileage but he was out). Jim Robertson in Los Osos has over 10,000 miles
(his coach was the one recently noted in a posting for sale with the
Cadillac 500 engine - there was a picture of it with the wheels). My belief
is that the front bearings can indeed handle the stresses. This assumes
that people keep their bearings well greased and change them out at 25,000
miles. Whether they weaken the ability of the front end to handle a severe
bump at high speed . . . who knows?
The wheels to use are Alcoa 16 x 7's designed for Ford trucks. They get
the fronts very close to the widths of the back wheels. They are NOT hub
centering. Some people have used them this way but I chose to purchase a
centering hub from Aptos Tool Co in Aptos, CA for $95. This hub is made by
a GMC owner who owns a machine shop and made a set for himself (I don't
know how many miles he has on his own wheels).
I had the wheels and hub/spacers on the coach for a relatively short
time to test the setup. I think that there is no doubt that they help the
rut stability problem. However, they do indeed change the geometry of the
front end. Torque steer is definitely an issue. They clearly accentuated a
left to left-right-left (or is it right-left-right) front drive wiggle upon
starting out. I talked about with this with Mike Mayo, and he felt that
this was the only significant negative to the wide wheels. I found the ride
to be harsher and I felt the bumps more extremely. This may have been my
coach or it may be the offset. Likely it is something that can be adjusted
out of the coach with some creative alignment work. I took them off the
coach because I will be doing a lot of work on the front end and wanted to
be sure that any problems are not related to the wide rims. My intention is
to try them again once everything is overhauled - bearings, hubs etc.
My suggestion for the perfect set up is to widen the frame at the front,
which is in agreement with Brent's most recent posting. This would mean not
only changing the frame, but getting custom sway bars, axles etc. It would
probably work superbly though.
If anyone would like to seriously experiment with my rims on their
coach, then please get in touch.
Vic Marks
Vancouver, BC
75 transmode
------------------------------
Date: Mon, 14 Feb 2000 21:04:05 EST
From: GMC77PB
Subject: Re: GMC: tow ins.
In a message dated 02/14/2000 2:22:12 PM Central Standard Time,
>
Have a tow bar welded under the front of your GMC so you won't have to worry
about towing. Not expensive, Not hard to make. If you want dimensions, write
me direct.
Justin
suspension
geometry) will be changed and this is a major concern. For example, the
ball
joints and A-arm bushings will see higher loading in the plane parallel to
the ground. I mentioned before that the torsion bar will receive higher
torsional stress. Torque steer will probably become more noticeable and
there
is a host of other effects that will have to be looked at and maybe the
conclusion will be that it is just not worth it.
Even if we conclude that a change may be beneficial, chances are that
there
is not a wheel available with the offset we need. But at least we will know
something. Either the factory offset is optimal or it isn't. Whether we can
do something about it or not is another subject.
Dave, (and now Brent), I think that you have it basically correct here. I
have no expertise in the theoretical pro's and con's of this issue but I do
have a bit of experience. There are at least a half dozen people who have
run a fair number of miles on the wide rims. Mike Mayo in Colorado has (I
think) around 20,000 miles on his coach (I tried to call him to confirm the
mileage but he was out). Jim Robertson in Los Osos has over 10,000 miles
(his coach was the one recently noted in a posting for sale with the
Cadillac 500 engine - there was a picture of it with the wheels). My belief
is that the front bearings can indeed handle the stresses. This assumes
that people keep their bearings well greased and change them out at 25,000
miles. Whether they weaken the ability of the front end to handle a severe
bump at high speed . . . who knows?
The wheels to use are Alcoa 16 x 7's designed for Ford trucks. They get
the fronts very close to the widths of the back wheels. They are NOT hub
centering. Some people have used them this way but I chose to purchase a
centering hub from Aptos Tool Co in Aptos, CA for $95. This hub is made by
a GMC owner who owns a machine shop and made a set for himself (I don't
know how many miles he has on his own wheels).
I had the wheels and hub/spacers on the coach for a relatively short
time to test the setup. I think that there is no doubt that they help the
rut stability problem. However, they do indeed change the geometry of the
front end. Torque steer is definitely an issue. They clearly accentuated a
left to left-right-left (or is it right-left-right) front drive wiggle upon
starting out. I talked about with this with Mike Mayo, and he felt that
this was the only significant negative to the wide wheels. I found the ride
to be harsher and I felt the bumps more extremely. This may have been my
coach or it may be the offset. Likely it is something that can be adjusted
out of the coach with some creative alignment work. I took them off the
coach because I will be doing a lot of work on the front end and wanted to
be sure that any problems are not related to the wide rims. My intention is
to try them again once everything is overhauled - bearings, hubs etc.
My suggestion for the perfect set up is to widen the frame at the front,
which is in agreement with Brent's most recent posting. This would mean not
only changing the frame, but getting custom sway bars, axles etc. It would
probably work superbly though.
If anyone would like to seriously experiment with my rims on their
coach, then please get in touch.
Vic Marks
Vancouver, BC
75 transmode
------------------------------
Date: Mon, 14 Feb 2000 21:04:05 EST
From: GMC77PB
Subject: Re: GMC: tow ins.
In a message dated 02/14/2000 2:22:12 PM Central Standard Time,
>
Have a tow bar welded under the front of your GMC so you won't have to worry
about towing. Not expensive, Not hard to make. If you want dimensions, write
me direct.
Justin
