Reply
 
Thread Tools Search this Thread Display Modes
 
Old 07-18-2014, 04:11 PM   #29
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
Quote:
Originally Posted by dkottum View Post
The best hitch you can buy is a fraction of the cost of trying to solve handling issues by trading trucks.
Fully agree.

I would go further and say that trading trucks doesn't necessarily solve handling issues, sometimes it just masks them (until you get to the point where it doesn't, and then you are in deep).
__________________

__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 04:20 PM   #30
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
Quote:
Originally Posted by kscherzi View Post
Wouldn't a one ton dually be more stable? Four tires instead of two to keep things on track.
The wider track could make it more resistant to tipping over, if that is the concern. It would be a factor if the load was tall, certainly, as with a heavy slide in camper.

I would think that dual rear wheels could add lateral stability, depending on the tires of course.

One concern would be the truck squirming around on the tires. Duals means higher profile and narrower tires, so more squirm. And since the fronts are the same as the rear (common spare tire for both axles) that means potential degradation in steering responses. And in braking, due to weight transfer off the duals onto the narrower (by comparison) front tires.

Another concern is unsprung weight. Duals will be heavier. Every time you go over a dip in the road or a pothole, the springs push the tire/wheel/axle combination down into that depression to maintain contact and adhesion. More mass there means slower response, and thus less traction on anything but a completely smooth and level surface.

It would be interesting to see real data on how these various factors compare to each other.

Jeff
__________________

__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 04:28 PM   #31
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,402
Images: 5
Nonetheless, More contact patch, whether a dually or a semi, is ALWAYS a benefit in any scenario. It is THE only thing hooking you to planet earth.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Old 07-18-2014, 04:32 PM   #32
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
Quote:
Originally Posted by rostam View Post
Intuitively, it makes sense to have a TV that weighs about the same as the camper. Its the law in some European countries, as I've read.
Do you have a source for that?

I lived in the UK in the past, and was aware of a % limit of tow vehicle and caravan weight, but that was for unbraked trailers. There wasn't a limit with braked trailers, and all trailers over a certain GVWR needed brakes anyway. Certainly anything in the Airstream class needed brakes.

Same rule exists in Alberta, but it is for very light unbraked trailers.

Since European countries don't use weight distributing hitches, the relevance of such a regulation may be moot.
__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 04:37 PM   #33
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
Quote:
Originally Posted by dznf0g View Post
Nonetheless, More contact patch, whether a dually or a semi, is ALWAYS a benefit in any scenario. It is THE only thing hooking you to planet earth.
To get more contact patch for a given vehicle, wouldn't you need to increase the load in the vehicle or reduce the tire pressure? It doesn't depend on the tire size or configuration, apart from details around sidewall construction and tread pattern.
__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 04:41 PM   #34
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,402
Images: 5
Quote:
Originally Posted by jcl View Post
To get more contact patch for a given vehicle, wouldn't you need to increase the load in the vehicle or reduce the tire pressure? It doesn't depend on the tire size or configuration, apart from details around sidewall construction and tread pattern.

Adjusting pressure, etc. doesn't change things much. More tires = more contact patch. You can cheat on the friction with rubber compound and down force, etc. on a race car, but it is still all about those few dozen square inches, where the "rubber meets the road".

A lot of that is moot for us here, but still, everything we do is still about contact patch.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Old 07-18-2014, 04:48 PM   #35
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
Quote:
Originally Posted by dznf0g View Post
Adjusting pressure, etc. doesn't change things much. More tires = more contact patch. You can cheat on the friction with rubber compound and down force, etc. on a race car, but it is still all about those few dozen square inches, where the "rubber meets the road".

A lot of that is moot for us here, but still, everything we do is still about contact patch.
Maybe it is just semantics, but if you have 8000 lbs of truck, and tires inflated to 80 psi, you have 100 square inches of contact path, no matter how many tires you spread it out over.

We can change the number and shape of those contact patches, but adding tires doesn't make the total bigger. Single wheels with wide profile tires would have more of a wide and short contact patch per corner, while duals would have two narrow and long contact patches. But with the same amount of contact. Until you add load, or reduce pressure (neither of which is advisable, just illustrating the math).
__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 04:52 PM   #36
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,402
Images: 5
True, JCL, but I think you are assuming a dually single tire contact patch is half of single rear wheel one ton. I don't think that's the case.

Also, with the semi example, you have 10 contact patches on the tractor.

I re-read....there's something wrong with your math vs, definition of contact patch.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Old 07-18-2014, 05:00 PM   #37
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
Quote:
Originally Posted by dznf0g View Post
True, JCL, but I think you are assuming a dually single tire contact patch is half of single rear wheel one ton. I don't think that's the case.

Also, with the semi example, you have 10 contact patches on the tractor.

I re-read....there's something wrong with your math vs, definition of contact patch.
I'll leave the semi out, since the math works exactly the same.

Use an 8000 lb pickup truck. Assume 50/50 weight distribution for ease of calculation. Thus 2000 lbs per corner.

A single rear wheel with 80 psi on the inside (pushing out) is pressed into the ground with 2000 lbs, spread over a variable contact patch. It works out to 25 square inches. You can put duals on there, and you will still have 25 square inches. But it is divided between two tires. Put another way, each single tire of a dual set is carrying half the weight (1000 lbs in this example). It all comes out the same.

If the tire had a very high pressure, the contact patch would be a line. But the tire deforms to create the contact patch. That is why I called it variable, it depends on pressure and load. Not on the shape of the tire.

It is like when people install wide tires and think that puts more rubber on the ground. It doesn't (if we ignore sidewall and tread pattern effects, which are minor).

For a somewhat unrelated example, dragsters want a large contact patch for obvious reasons. That is why they run ultra low pressure tires. Simply putting very large tires wouldn't give them any more contact patch. But large rear slicks at 8 psi gives them a larger contact patch.

Jeff
__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 05:09 PM   #38
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,402
Images: 5
Check this out. It doesn't work out the same.

Tire Contact Patch | Lowering Pressure Gain Traction
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Old 07-18-2014, 05:21 PM   #39
jcl
Rivet Master
 
Currently Looking...
Vancouver , British Columbia
Join Date: Oct 2012
Posts: 1,046
I've read it.

I would agree that there are lots of effects of sidewall stiffness and other factors that affect the contact patch. Also, it seems intuitive that the front and back edges don't carry the same weight, due to the tire's shape. That makes the contact patch larger than the first order estimate discussed above. For lots of reasons, it isn't a straightforward linear relationship. But at the highest level, having duals instead of single rear tires doesn't greatly increase the contact patch. It doesn't double it. It changes the location of it, and the shape of it. And it has a parallel effect on the front tires, since they are using a narrower tire in a single wheel configuration.

If we wanted to go really deep we could get into the friction based on the normal forces.

Jeff
__________________
jcl is online now   Reply With Quote
Old 07-18-2014, 05:31 PM   #40
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,402
Images: 5
No, it doesn't double it...absolutely agree, but in the real world, if you set up a inked tire test with equal weights on the ground between a one ton SRW and DRW identically wheeled and tired trucks, you would find 1.5 - 1.75 times the contact patch with a dually with varying but equal loads on the rear axle.
__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Old 07-18-2014, 05:33 PM   #41
Rivet Master
 
Vintage Kin Owner
N/A , N/A
Join Date: Sep 2012
Posts: 995
Images: 1
Quote:
Originally Posted by jcl View Post
Do you have a source for that?

I lived in the UK in the past, and was aware of a % limit of tow vehicle and caravan weight, but that was for unbraked trailers. There wasn't a limit with braked trailers, and all trailers over a certain GVWR needed brakes anyway. Certainly anything in the Airstream class needed brakes.

Same rule exists in Alberta, but it is for very light unbraked trailers.

Since European countries don't use weight distributing hitches, the relevance of such a regulation may be moot.
Should have said recommendation, rather than law.

Here is a link:

Matching Car and Caravan - The Camping and Caravanning Club

They recommend a trailer that weighs 85% of the TV for beginners, and 100% of the TV for experienced folks.
__________________
rostam is offline   Reply With Quote
Old 07-18-2014, 05:35 PM   #42
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,402
Images: 5
Quote:
Originally Posted by rostam View Post
Should have said recommendation, rather than law.

Here is a link:

Matching Car and Caravan - The Camping and Caravanning Club

They recommend a trailer that weighs 85% of the TV for beginners, and 100% of the TV for experienced folks.
Crap, I need to find a 10,000 lb pickup truck.....or heck, I'll just put 2700# of rocks in the bed.
__________________

__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is online now   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Austin, TX and its Relationship with Airstreams Frank&Mike Airstream Lifestyle 6 08-04-2013 08:10 PM
Helen Byam Schwamborn relationship to Wally? 61Overlander Airstream History 13 12-08-2007 06:36 PM
SWM "bohemian" type seeks lasting relationship with travel trailer kat Member Introductions 22 05-04-2006 12:38 AM
A/S as relationship dealbreaker? summerkid Off Topic Forum 44 09-02-2005 11:03 AM
Number relationship ? brohloff Our Community 6 06-02-2004 11:09 AM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 12:29 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.