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Traction question [message #276958]

Wed, 29 April 2015 06:30

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

We've all heard of folks who were not able to climb a wet driveway or get going on an uphill at a wet intersection, etc. While I have not experienced it personally, I have been stuck in the yard.

At the recent GMCMI rally in Patterson, LA, during Ken Henderson's seminar on wheel alignment, the subject of effects of ride height came up. Someone (could have been Ken) said that if you are ever in a low traction situation, raise the right rear and it will transfer weight to the left front (drive wheel).

Ding ding ding...lights flashed...ding ding ding. Now that is a nugget of information I'd never considered.

Unless someone KNOWS how much additional weight is transferred when the right rear is raised to max height, the next time I'm with someone weighing coaches, this is something I'd like to know.

So assuming that some additional weight is transferred, here is a question for the engineers among us. If the drive tire has 2000 lbs on a typical LT225_75R16. What kind of improvement in wet traction on pavement would an additional 500 lbs have? I realize there are a ton of variables from road surface, tire tread, and on and on, but I'm just wondering if it is significant enough improvement to matter...traction wise.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Traction question [message #276959 is a reply to message #276958]

Wed, 29 April 2015 06:36

appie

Messages: 902
Registered: April 2013
Location: denmark

Karma: 2

Senior Member

Well yes , in teorie

When Olga failed to climb the whet cobblestones in portugal last month the tail was up all the way. 120 psi. I always do that on inclines så I wont loose the black tube😨😨.

I think reversing up the hill will do the trick if you realy have to go there

Appie eleganza 76 "Olga" now sadly sold 6 wheel discbrake Quadrabags Springfield stage 2 462 olds Manny tranny ( pictures at http://www.gmcmhphotos.com/photos/g6489-olga.html Fulltiming in Europe july 2014 til july 2016 Denmark

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Re: Traction question [message #276960 is a reply to message #276958]

Wed, 29 April 2015 07:02

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

Appie, the trick was raising only the RIGHT rear. I'm sure there is weight transfer from raising both rears...another thing to test.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: [GMCnet] Traction question [message #276963 is a reply to message #276958]

Wed, 29 April 2015 07:05

Tim Hart

Messages: 12
Registered: April 2015

Karma: 0

Junior Member

Kerry, where in North Alabama are you located. I am in N. Georgia.
Not this weekend but the following I will be going up to pick up Liberty from
Teri Gregg.
Tim Hart

Sent from my iPad

> On Apr 29, 2015, at 7:30 AM, Kerry Pinkerton wrote:
>
> We've all heard of folks who were not able to climb a wet driveway or get going on an uphill at a wet intersection, etc. While I have not experienced
> it personally, I have been stuck in the yard.
>
> At the recent GMCMI rally in Patterson, LA, during Ken Henderson's seminar on wheel alignment, the subject of effects of ride height came up. Someone
> (could have been Ken) said that if you are ever in a low traction situation, raise the right rear and it will transfer weight to the left front (drive
> wheel).
>
> Ding ding ding...lights flashed...ding ding ding. Now that is a nugget of information I'd never considered.
>
> Unless someone KNOWS how much additional weight is transferred when the right rear is raised to max height, the next time I'm with someone weighing
> coaches, this is something I'd like to know.
>
> So assuming that some additional weight is transferred, here is a question for the engineers among us. If the drive tire has 2000 lbs on a typical
> LT225_75R16. What kind of improvement in wet traction on pavement would an additional 500 lbs have? I realize there are a ton of variables from
> road surface, tire tread, and on and on, but I'm just wondering if it is significant enough improvement to matter...traction wise.
> --
> Kerry Pinkerton
>
> North Alabama
>
> 77 Eleganza II, 403CI, Manny Brakes, 1 ton, tranny, lots of aluminum goodies.
>
> 77 Kingsley by Buskirk. Rear twins/dry bath, EFI Caddy.
>
> Also a 76 Eleganza to be re-bodied as an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Re: Traction question [message #276966 is a reply to message #276960]

Wed, 29 April 2015 07:40

thesmith

Messages: 589
Registered: February 2015
Location: Cary, NC

Karma: 6

Senior Member

kerry pinkerton wrote on Wed, 29 April 2015 07:02

Appie, the trick was raising only the RIGHT rear. I'm sure there is weight transfer from raising both rears...another thing to test.

I assume that is because its always the left front wheel that looses grip first? I doubt there is much, if any, transfer by raising both.

What we need are electric hub motors in the rear wheels....6x6 baby!

Pete

Cary, NC 1978 Center Kitchen Royale.

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Re: Traction question [message #276968 is a reply to message #276966]

Wed, 29 April 2015 08:16

Jp Benson

Messages: 649
Registered: October 2011
Location: Fla

Karma: 2

Senior Member

thesmith wrote on Wed, 29 April 2015 07:40

kerry pinkerton wrote on Wed, 29 April 2015 07:02
Appie, the trick was raising only the RIGHT rear. I'm sure there is weight transfer from raising both rears...another thing to test.

I assume that is because its always the left front wheel that looses grip first? I doubt there is much, if any, transfer by raising both.

What we need are electric hub motors in the rear wheels....6x6 baby!

Pete

Breaking the rule that one should never do math out loud in public places, I calculate that it's possible to shift ~4% of the rear wheel weight to the forward wheels. That assumes that I've raised the rear wheels 6 inches. Maybe one of the mechanical guys with the right software can get a better answer. That's enough weight shift to help in some circumstances as Ken and others have noted. You'll still be pulling uphill though.

I like the electric hub motor idea. Where do you get em?

JP

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Re: [GMCnet] Traction question [message #276969 is a reply to message #276963]

Wed, 29 April 2015 08:17

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

Tim Hart wrote on Wed, 29 April 2015 07:05

Kerry, where in North Alabama are you located. I am in N. Georgia.
Not this weekend but the following I will be going up to pick up Liberty from Teri Gregg.
Tim Hart

Tim, I'm near Huntsville.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: [GMCnet] Traction question [message #276972 is a reply to message #276969]

Wed, 29 April 2015 08:44

Tim Hart

Messages: 12
Registered: April 2015

Karma: 0

Junior Member

Kerry,
Here is my email address- timhart@mindspring.com
My son in law is a meteorologist, worked in Huntsville until 2years ago.
Nice area.
Tim

Sent from my iPad

> On Apr 29, 2015, at 9:17 AM, Kerry Pinkerton wrote:
>
> Tim Hart wrote on Wed, 29 April 2015 07:05
>> Kerry, where in North Alabama are you located. I am in N. Georgia.
>> Not this weekend but the following I will be going up to pick up Liberty from Teri Gregg.
>> Tim Hart
>
>
> Tim, I'm near Huntsville.
> --
> Kerry Pinkerton
>
> North Alabama
>
> 77 Eleganza II, 403CI, Manny Brakes, 1 ton, tranny, lots of aluminum goodies.
>
> 77 Kingsley by Buskirk. Rear twins/dry bath, EFI Caddy.
>
> Also a 76 Eleganza to be re-bodied as an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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Unsubscribe or Change List Options:
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Re: Traction question [message #276979 is a reply to message #276958]

Wed, 29 April 2015 10:00

midlf

Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)

Karma: 1

Senior Member

This is one of those kinds of things that are "well it can't hurt to try". Sometimes you don't need much.

In my dirt approach to the barn I have gotten stuck. I have learned how much gas to give it to not spin. Holding that throttle for a short time, less than a minute, and the GMC will start creeping. I think the forward pressure of the tire pushes down the dirt wedge at the tire and then it sloooowly starts to move. Don't add any more gas until the speed picks up. In other words, don't transition from static to dynamic friction.

And some times it's just tractor time.

Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

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Re: Traction question [message #276999 is a reply to message #276958]

Wed, 29 April 2015 13:02

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

""So assuming that some additional weight is transferred, here is a question for the engineers among us. If the drive tire has 2000 lbs on a typical LT225_75R16. What kind of improvement in wet traction on pavement would an additional 500 lbs have? I realize there are a ton of variables from road surface, tire tread, and on and on, but I'm just wondering if it is significant enough improvement to matter...traction wise.
""

Friction = normal force X coefficient of friction. Technically you would get a 25% increase in traction. The normal force is the weight on that wheel, and the co-efficient of friction isn't changed between the two scenarios.

Bob de Kruyff
78 Eleganza
Chandler, AZ

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Re: Traction question [message #277003 is a reply to message #276999]

Wed, 29 April 2015 14:27

hal kading

Messages: 642
Registered: February 2004
Location: Las Cruces NM

Karma: 4

Senior Member

Sometimes it doesn't take much additional load to get traction. We took our Buskirk stretch (15,000 #) up Manny's hill, Manny driving. I followed in our Suzuki. Tire (left front?) started spinning about 150 ft from his driveway. Manny had me (150#) get in and crouch as close to the windshield as I could get. That was all it took to make it the rest of the way.

Hal Kading 78 Buskirk Stretch Las Cruces NM

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Re: Traction question [message #277006 is a reply to message #276958]

Wed, 29 April 2015 15:38

habbyguy

Messages: 896
Registered: May 2012
Location: Mesa, AZ

Karma: 3

Senior Member

I'm sure it must have been covered here a million times (though apparently not in this thread). But the old off-roader's trick is the one that probably works the best - let some air out of the front tires. That will increase the area of the contact patch for the tires, allowing for more traction and/or more "flotation" in soft sand or dirt (a relative term, since you ain't gonna float a 12,000 pound RV in any real sense). But there have been many times when I've let air out of the drive tires on other vehicles and gained enough traction to get out of a situation they were incapable of dealing with until I did let that air out.

Just be careful that you don't let so much air out that you break a bead on the tire, and certainly air it back up before you get back on the "real road". My lawyer suggested that I add "if you try this, your RV will explode, meteors will fall on you, lightning will strike you, and the world will come to a sudden and violent end". That oughta cover the liability... Wink

Mark Hickey Mesa, AZ 1978 Royale Center Kitchen

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