Tid Bit. When making changes to your GMC. Does that change differ from proven automotive engineering practices.

Excuse my ignorance to this topic but I am green to the GMC motorhome commu=
nity. I=E2=80=99ve learned a few things in the short amount of time we=
=E2=80=99ve owned one but this topic of which front end to run always seems=
to be a hot topic. Again I apologize if these questions sound dumb. But wh=
y is it that there are only 2 options to solve any of the above named probl=
ems with our front ends. With the amount of builders out there and suspensi=
on =E2=80=9Cexperts=E2=80=9D there should be more options. Heavy duty contr=
ol arms are abundant not just relegated to the one ton gm ones that people =
are using. Along with aftermarket suspension components that can accommodat=
e any number of scenarios. Again I=E2=80=99m learning as I go and have had =
the opportunity to build a few suspension systems in custom cars and trucks=
but nothing on the scale of our rigs. Maybe some day when we park ours I=
=E2=80=99ll have a chance to dive in but until then I=E2=80=99ll differ to =
the guys that have tried and experimented with any number of components. =
Sent from my iPhone > On May 15, 2018, at 12:10 PM, Fred > The traction thing is a function of how much weight there is on the d=
rive >> wheels. In a front wheel drive car, the front wheels have more we=
ight than >> the rear unless you have a heavy load. Front wheel drive car=
s have better >> traction characteristics than rear wheel drive. We have=
about 4k of 12k >> lbs on the front axle. If we changed the system to on=
ly drive the center >> wheels like we had a tag axle we would have the sa=
me problem. Tag axle >> systems get away with driving the axle with the m=
ost load and in most cases >> can unload the tag. Have 1/3 of the load on=
the drive wheels puts this MH >> to a disadvantage compared to on with 2=
/3. >> There may be other factors but these are the ones I see. > > =
> many other factors. but the incorrect geometry of the 1-ton would seem=
to make an already traction challenged front drive even worse. > > bu=
t can the 1-ton geometry be corrected with ball joint relocation by modifyi=
ng one or both control arms is my biggest question. if the geometry cant =
> be correct, Im not interested and wont be considering coaches that have t=
he 1-ton front. > > see, when the camber changes, it moves the tire la=
terally and that starts the loss of traction then it gets continued by the =
drive forces. once the > traction is 'broke' its nearly impossible to get=
it back. > > I would really like to have one without the difficult wh=
eel bearings but Id rather have one that can negotiate difficult paved surf=
aces and minor > offroad the best. drive traction is obviously an issue b=
efore any incorrect geometry. > > > _______________________________=
________________ > GMCnet mailing list > Unsubscribe or Change List Opt=
ions: > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org=
 
> Whaddya mean, "traction problems"?
> Just because it won't move on wet grass if the grass is slightly longer
> under the front wheels???

some say front wheel drives have a traction advantage but all my real world experiences tell me otherwise. Ive refused to own one as a personal driver
upto now but the GMC is such an exceptional machine that Im willing to finally own a front wheel drive (I almost puked writing that)

the only traction advantage any front wheel drive has would be going in reverse and if the control arms are not even on any front wheel drive it would
be less than optimal. optimal and front wheel drive dont even go together.. LOL!

the only GMC Ive actually driven so far was on a test drive. it was mostly original and had really old tires but it broke traction on dry, level
pavement very easily. like less than half throttle. it had been sitting for a while so Im not sure if it had brakes dragging or something though.

Ive been told there is a guy locally with over 600hp in his and it will do 50mph rolling burnouts which usually would be impressive (if RWD or AWD)
but being front wheel drive, it doesnt surprise or impress me.
 
John
Nope they should not lock up at the same time. ( non racing applications )
Agreed that Lockup is not desirable but can happen, and is pretty hard to do on a stock-ish system

Good luck getting the middle to lockup first, and again it shouldn't, the front should lock first.
If the backs lock first you will swap ends and loose control, if the front locks first you will plow a little until you release the pedal
________________________________
From: Gmclist on behalf of John Phillips
Sent: Tuesday, May 15, 2018 12:58 PM
To: gmclist
Subject: Re: [GMCnet] Tid Bit. When making changes to your GMC. Does that change differ from proven automotive engineering practices.

Keith,
The key is if they are balanced they should all lock up at the same time.
There is no way to get them that balanced. The key is you do not lock them
up at all. Locked up is not good practice but only a test to see if you can
do it. Max brake is just before lockup. Ideally the center then the front
and last the back axle. I did state the middle should lockup before the
back wheels

On Tue, May 15, 2018 at 10:46 AM, John Phillips
wrote:

> The traction thing is a function of how much weight there is on the drive
> wheels. In a front wheel drive car, the front wheels have more weight than
> the rear unless you have a heavy load. Front wheel drive cars have better
> traction characteristics than rear wheel drive. We have about 4k of 12k
> lbs on the front axle. If we changed the system to only drive the center
> wheels like we had a tag axle we would have the same problem. Tag axle
> systems get away with driving the axle with the most load and in most cases
> can unload the tag. Have 1/3 of the load on the drive wheels puts this MH
> to a disadvantage compared to on with 2/3.
> There may be other factors but these are the ones I see.
>
>
> On Tue, May 15, 2018 at 10:22 AM, John Phillips

>
>> I am more concerned with front wheel bearing life. Do we really have to
>> service the front bearings at 3500 miles? I do not remember ever having a
>> vehicle that needed repacking less than 50k miles.
>> As for locking up all 6 wheels, the fact that you can lock them all up is
>> one thing but the real key is they should all lock up at the same time. The
>> pole-vault effect is one thing but the real problem is that it unloads the
>> back wheels. Replacing the back wheel cylinder with a smaller one that
>> locks it up just after the center axel locks up would be a more
>> cost-effective solution. The key is balance between braking and traction,
>> where traction is proportional to the dynamic loading while braking. With
>> the long wheelbase, we do not get as much load transfer as a car would get.
>> The main transfer we get is from the back to the center wheels.
>>
>> 75 Avion
>> Sacramento CA
>>
>>
>>

>>
>>> 12,000 pound, 6 wheels down, underpowered front wheel drive, high center
>>> of balance motorhomes do not handle even remotely like a 1250 pound mid
>>> engined rear wheel drive race car with 700 horsepower. All that
>>> hypothetical crap about a-arms must be perpendicular to the racing
>>> surface
>>> goes out the window.
>>> The average 60+ year old driver of motor homes cares about wind
>>> steer,
>>> tire tread life, driver comfort, etc. They like straight line braking to
>>> be
>>> comparable to modern autos that they share the road with. Just my
>>> opinion.
>>> Your might vary.
>>> Jim Hupy
>>> Salem, Or
>>> 78 GMC ROYALE 403
>>>

>>>

>>> > > It means camber will increase (slightly) with jounce,
>>> >
>>> >
>>> > negative or positive camber? and by using the word 'jounce' do you mean
>>> > upward motion?
>>> >
>>> > if negative camber increases with upward motion, it wouldnt be as bad
>>> as
>>> > positive camber increasing with upward motion IMO but if it is a
>>> drastic
>>> > change eitherway (more than one degree) it would upset traction.
>>> actually
>>> > any change will upset traction but a minor amount might be acceptable.
>>> >
>>> > does anyone know how much difference there is and if one of the ball
>>> > joints could be relocated to correct it?
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > GMCnet mailing list
>>> > Unsubscribe or Change List Options:
>>> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>> >
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>>
>>
>>
>> --
>>
>> *John Phillips*
>>
>
>
>
> --
>
> *John Phillips*
>

--

*John Phillips*
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
I have owned VW Rabbits, one with a 16valve GTI option, and two PT
cruisers. One 5 speed stick normally aspirated, and one high performance
turbocharged dream cruiser with performance handling package. I still have
that one. Turn off the traction control, power brake it a bit to spool up
the turbo, and whoa baby, hang on. Ya gotta pay attention to it. Front
wheel drive cars are way different than rear wheel drive.
Jim Hupy
Salem, Or

> > Whaddya mean, "traction problems"?
> > Just because it won't move on wet grass if the grass is slightly longer
> > under the front wheels???
>
>
>
> some say front wheel drives have a traction advantage but all my real
> world experiences tell me otherwise. Ive refused to own one as a personal
> driver
> upto now but the GMC is such an exceptional machine that Im willing to
> finally own a front wheel drive (I almost puked writing that)
>
> the only traction advantage any front wheel drive has would be going in
> reverse and if the control arms are not even on any front wheel drive it
> would
> be less than optimal. optimal and front wheel drive dont even go
> together.. LOL!
>
> the only GMC Ive actually driven so far was on a test drive. it was mostly
> original and had really old tires but it broke traction on dry, level
> pavement very easily. like less than half throttle. it had been sitting
> for a while so Im not sure if it had brakes dragging or something though.
>
> Ive been told there is a guy locally with over 600hp in his and it will do
> 50mph rolling burnouts which usually would be impressive (if RWD or AWD)
> but being front wheel drive, it doesnt surprise or impress me.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I have driven both front an rear wheel drive vehicles in snow and Ice. Many
winter trips over Donor Pass and Teton pass. The front wheel drive has
always been better for me than the rear wheel drive. When a rear wheel
drive brakes traction it has a tendency to get going sideways. Most cars
have close to 2/3 of the weigh on the front wheels with only the driver
onboard. The amount of weight transfer in accelertion is insignificant
under normanl conditions. We are not acclerating like a dragster which does
get significant weight transfer. We are not pulling heavy loads. Our
problem is when the friction coeffishent aprochas 0, we would like to have
all weigh on the drive wheels. In the winter time my father would put 400
lbs of coal up agenst the tailgate of our 1/2 ton pickup. It was rear wheel
drive but without the added weight on the rear drive wheels it would get
stuck real easy. Weight on the drive wheels * friction coeffishent
determins maximum thrust.
Some of our old truck tires have a lower friction coeffishent than our cars
do so the wheels spin easier than car tires. We tipicly do not put mud and
snow rated tires on our MH.

> > Whaddya mean, "traction problems"?
> > Just because it won't move on wet grass if the grass is slightly longer
> > under the front wheels???
>
>
>
> some say front wheel drives have a traction advantage but all my real
> world experiences tell me otherwise. Ive refused to own one as a personal
> driver
> upto now but the GMC is such an exceptional machine that Im willing to
> finally own a front wheel drive (I almost puked writing that)
>
> the only traction advantage any front wheel drive has would be going in
> reverse and if the control arms are not even on any front wheel drive it
> would
> be less than optimal. optimal and front wheel drive dont even go
> together.. LOL!
>
> the only GMC Ive actually driven so far was on a test drive. it was mostly
> original and had really old tires but it broke traction on dry, level
> pavement very easily. like less than half throttle. it had been sitting
> for a while so Im not sure if it had brakes dragging or something though.
>
> Ive been told there is a guy locally with over 600hp in his and it will do
> 50mph rolling burnouts which usually would be impressive (if RWD or AWD)
> but being front wheel drive, it doesnt surprise or impress me.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*
 
Matt,

Your note below reminded me that I DO have a heavier (Caspro) front sway
bar on Tweety=Bird. Perhaps that explains my
total satisfaction with the 1-Ton. I swapped that bar with the X-PB my son
now has in an effort to make it possible to level that one. Only removing
the rear two sway bars accomplished that end. :-)

Ken H.

> ​...
> It had a 1-ton mod and it did have nice brakes, but it also had a
> different handling issue when pushed into a
> corner. I knew from experience that it was caused by adverse camber.
> This might be mitigated if one was to install a much heavier sway (really
> it is
> an anti-roll) bar in the front so there is less differential change in any
> cornering situation.
>
>
 
Attaching the motor to the wheel that steers might be one reason.

But I agree that for competition with skilled drivers rear drive is better.
That’s not what we have with the GMC, of course. Wet grass is often the
problem, and a 12,000-pound vehicle with 4000 of that on the drive wheels
is the issue. There is more weight transfer than people realize.

My light 23 is better—less weight behind the rear wheels, and a higher
percentage on the front.

The problem occurs in inaved, grassy campground slots. When I am faced with
wet grass and it is level, I ease the throttle—I get more traction if I
don’t shear the ground surface. If the parking spot is a hill, I park where
I can reverse to go up the hill, or simply roll with gravity going down it.
An old trick that works is to put a partner into the toad and use it for
drive thrust.

But it’s simply never an issue on any pavement a GMC is likely to see.

In return for that occasional problem, we don’t need stairs to get into the
coach, and the center of gravity is very low. That’s a good trade off.

Rick “who has never been profoundly stuck, but who has occasionally helped
others” Denney

> ever wonder why there are no front wheel drive motorbikes?
>
>
> I dont. LOL!
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
 
I've had the one ton front end for 7 years with 2 different revisions.
The newer version of the kit has many unseen improvements, such as
better accuracy in the lower ball joint location. And the newer
axles are more precise. I also went through the hassle of relocating
the upper control arm pivots upward, using K2500 arms and ball joints.
I can definitely feel the improvement. It tracks straight. Raising
the upper control arms also reduces the load on the torsion bars.
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
So it looks like

The one ton is less expensive than a proper rebuild of the stock front end.

If you find yourself examining the corner(s) of the envelope, particularly without warning, you're likely better of in the stock setup.

If you need to stop panic style, the one - ton might be marginally better. Both benefit greatly from reaction arms.

Way more of the one - ton components - except those fabbed for the GMC - than there were originals.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Here is a front suspension simulator. Enter the parameters of your front end (OEM or 1 ton) and see what it actually does as the suspension moves.

vsusp.com

It saves your entered parameters in its URL, so once you are done save it as a favourite site in your bookmarks. To post it on the forum for others
to see, you will be best to use TinyURL.com to shorten the link for posting.

Lets see what's happening!
--
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
 
I think front wheel drive CARS have an an advantage on sloppy roads,
because the front wheels are usually pointed in the direction that you
are trying to move.

RonC

> > Whaddya mean, "traction problems"?
> > Just because it won't move on wet grass if the grass is slightly
> longer
> > under the front wheels???
>
>
>
> some say front wheel drives have a traction advantage but all my
> real world experiences tell me otherwise. Ive refused to own one as
> a personal driver
> upto now but the GMC is such an exceptional machine that Im willing
> to finally own a front wheel drive (I almost puked writing that)
>
> the only traction advantage any front wheel drive has would be going
> in reverse and if the control arms are not even on any front wheel
> drive it would
> be less than optimal. optimal and front wheel drive dont even go
> together.. LOL!
>
> the only GMC Ive actually driven so far was on a test drive. it was
> mostly original and had really old tires but it broke traction on
> dry, level
> pavement very easily. like less than half throttle. it had been
> sitting for a while so Im not sure if it had brakes dragging or
> something though.
>
> Ive been told there is a guy locally with over 600hp in his and it
> will do 50mph rolling burnouts which usually would be impressive (if
> RWD or AWD)
> but being front wheel drive, it doesnt surprise or impress me.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Bill,
Thanks for that! Now I just need to do some additional reading to figure this all out.

Anyone have a stock OEM entered into Vsusp.com, or the measurements? It would be interesting to compare.
--
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
 
Uh GMC2000, try a Rokon. It drives front and rear wheels. Won't go fast or float, but it will go anyplace else.

https://www.rokon.com/

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
I have driven both front an rear wheel drive vehicles in snow and Ice. Many
winter trips over Donor Pass and Teton pass. The front wheel drive has
always been better for me than the rear wheel drive. When a rear wheel
drive brakes traction it has a tendency to get going sideways. Most cars
have close to 2/3 of the weigh on the front wheels with only the driver
onboard. The amount of weight transfer in accelertion is insignificant
under normanl conditions. We are not acclerating like a dragster which does
get significant weight transfer. We are not pulling heavy loads. Our
problem is when the friction coeffishent aprochas 0, we would like to have
all weigh on the drive wheels. In the winter time my father would put 400
lbs of coal up agenst the tailgate of our 1/2 ton pickup. It was rear wheel
drive but without the added weight on the rear drive wheels it would get
stuck real easy. Weight on the drive wheels * friction coeffishent
determins maximum thrust.
Some of our old truck tires have a lower friction coeffishent than our cars
do so the wheels spin easier than car tires. We tipicly do not put mud and
snow rated tires on our MH.

> > Whaddya mean, "traction problems"?
> > Just because it won't move on wet grass if the grass is slightly longer
> > under the front wheels???
>
>
>
> some say front wheel drives have a traction advantage but all my real
> world experiences tell me otherwise. Ive refused to own one as a personal
> driver
> upto now but the GMC is such an exceptional machine that Im willing to
> finally own a front wheel drive (I almost puked writing that)
>
> the only traction advantage any front wheel drive has would be going in
> reverse and if the control arms are not even on any front wheel drive it
> would
> be less than optimal. optimal and front wheel drive dont even go
> together.. LOL!
>
> the only GMC Ive actually driven so far was on a test drive. it was mostly
> original and had really old tires but it broke traction on dry, level
> pavement very easily. like less than half throttle. it had been sitting
> for a while so Im not sure if it had brakes dragging or something though.
>
> Ive been told there is a guy locally with over 600hp in his and it will do
> 50mph rolling burnouts which usually would be impressive (if RWD or AWD)
> but being front wheel drive, it doesnt surprise or impress me.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*
 
> Uh GMC2000, try a Rokon. It drives front and rear wheels. Won't go fast or float, but it will go anyplace else.
>
> https://www.rokon.com/
>
> --johnny

rokons are not 'front wheel drive' though, christini makes a modern all wheel drive conversion system for the popular on/off road models now as an
assist like the old rokons but front wheel drive only would be too hazardous for a moto where loss of traction on the front could prove deadly.
 
I can?t say I ever did a skid pad comparison, but I can share some direct
experience with stock and modified coaches. Our 1977/1994 Clasco was bone
stock with a good, tight front end, stock air bag rear and well adjusted
stock brakes. Our 1978 Royale had just about everything done one could do
to ?modernize? a GMC. That included the one ton front end, six wheel
reaction arm disk brakes, etc. But, it retained the stock one air bag system
as well. Both had the same wheels and tires aired to the correct pressures
for measured weight on each wheel. Both had the wireless air system with
the ride height set to factory specs. Both were aligned properly with as
much caster as they would allow and still be the same on both sides. The
offset bushing allowed a bit more caster in the Royale than in the Clasco -
one degree difference as I recall. The Royale was heavier by a few hundred
pounds than the Clasco due mainly to the fact that it had four 6v golf cart
batteries mounted in the rear PS compartment where the Clasco had one 4D 12v
AGM and one group 31 AGM house battery bank centered in the rear.

Bottom line, both drove equally as well and we put a lot of wonderful miles
on each of them. The only difference I could ever really tell from the
drivers seat was a tendency of the Royale to shimmy a bit on low speed hard
turns going up hill under acceleration. Other than that, they both were one
hand on the steering wheel rides. I never had either one in a full lock
brake situation, never flat spotted a tire and never heated the brakes to
fade. Probably more from placebo effect than anything objective, I always
thought I preferred the brakes in the Royale even though the pedal went
further towards the floor and the bogy mount location for the reaction arms
had a tendency to come loose from time to time.

My experience with these two coaches over a number of years is that proper
ride height, proper alignment, and proper inflation of the tires made more
difference in ride and handling than all the mods put together. I never did
understand why the Royale with the six wheel reaction arm disk brakes and
the larger front rotors from the one ton front end didn?t really stop any
better than the well adjusted stock brakes on the Clasco. That might have
been because I am a very conservative driver and never put myself in a
position where I had to rely on them in an extreme emergency.

Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple
building in historic Kerby, OR

glwork
http://jerrywork.com

==============

*****************************
 
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