Closed Thread
 
Thread Tools Search this Thread Display Modes
 
Old 01-02-2015, 07:18 AM   #29
Rivet Master
 
andreasduess's Avatar
 
1984 34' International
Toronto , Ontario
Join Date: Jul 2012
Posts: 1,496
Images: 5
Blog Entries: 1
The brakes of a heavy truck don't come with additional "just in case" stopping power built in, they are designed to stop the vehicle plus load - but that's it, as is the case for any vehicle.

The BMW has a top speed of around 130mph and weighs around 6000lbs loaded. If we fall back onto our high school physics knowledge for a moment, then momentum is mass x velocity (weight x speed), which for the BMW means that top momentum is p=780,000.

The brakes of the BMW are designed to safely deal with this, these are normal operating conditions. They do this by changing kinetic energy into heat energy, which means the biggest issue brakes face is heat dissipation.

Now, in a towing situation, let's assume the towing speed is 60mph and the total weight of the rig is 6000lbs for the car plus 7500lbs for the trailer, a total of 13500 lbs.

This changes the momentum equation to 13,500 x 60 with p now being 810,000.

While this number is higher, 810,000 vs 780,000, it is far from alarming and the BMW will still bring tow vehicle and trailer to a safe stop because far from being overburdened, as you suggest, the BMW's brakes are perfectly capable of dealing with the momentum in question.

Keep in mind that momentum dissipation is only one element of successful towing, albeit an important one and also keep in mind that the above example assumes a catastrophic trailer brake failure, with zero brake contribution from the trailer.

The rig will need a longer stopping distance in these circumstances, but so will any rig, with any tow vehicle.

A truck, which we know needs more than thirty additional feet to come to a stop even under ideal circumstances than the BMW, does not just ignore the 7500lbs in weight.
__________________

__________________
andreasduess is offline  
Old 01-02-2015, 07:46 AM   #30
Rivet Master
 
tjdonahoe's Avatar
 
2013 31' Classic
billings , Montana
Join Date: Feb 2010
Posts: 1,844
Think I will try the wife's toyota Venza out, it has 185 hp at 5000 rpm, with big brakes and weighs probably 1/2 what the 31 ' classic does. All we need to do is build a hitch for it, if I can find something to attach it to..???
__________________

__________________
tjdonahoe is offline  
Old 01-02-2015, 08:01 AM   #31
Rivet Master
 
Road Ruler's Avatar
 
Currently Looking...
St. Catharines , South Western Ontario
Join Date: Aug 2002
Posts: 2,364
Images: 39
Quote:
Originally Posted by tjdonahoe View Post
Think I will try the wife's toyota Venza out, it
Sounds good tj... Sounds like it would be a lot more comfortable to travel with than your 2007 dodge 6.7 diesel.
__________________
Airstreams..... The best towing trailers on the planet!
Road Ruler is offline  
Old 01-02-2015, 08:01 AM   #32
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Quote:
Originally Posted by tjdonahoe View Post
Think I will try the wife's toyota Venza out, it has 185 hp at 5000 rpm, with big brakes and weighs probably 1/2 what the 31 ' classic does. All we need to do is build a hitch for it, if I can find something to attach it to..???
Good idea TJ, my wife has a Chevy Equinox. Maybe I'll put a hitch on it and get rid of my big smok'in, chok'in, Diesel truck, and save some money!
__________________
Regards,
Steve
SteveH is offline  
Old 01-02-2015, 08:33 AM   #33
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Just checked and the Equinox has a whopping 182HP, and 172lb ft of torque. I don't know, that might be a tad light for a 11,500GVW trailer.

Didn't even check weight or towing specs, because we all know those automotive engineers don't know diddly squat about what they are doing.

But hey, I also checked and it has independent rear suspension, so that's all that matters, right?
__________________
Regards,
Steve
SteveH is offline  
Old 01-02-2015, 08:34 AM   #34
Rivet Master
 
tjdonahoe's Avatar
 
2013 31' Classic
billings , Montana
Join Date: Feb 2010
Posts: 1,844
We all might be able to make it to the near by wallmart . Mine is 2 miles down hill,might make it.Then we could pull out the bud lite and talk about how good the wife's mini van is, gas mileage,tire costs handling,and my special hitch, gosh I sure hope I can make it.. The smaller the better,how long would the engine last at 5000 rpm....
__________________
tjdonahoe is offline  
Old 01-02-2015, 08:37 AM   #35
Rivet Master
 
Vintage Kin Owner
N/A , N/A
Join Date: Sep 2012
Posts: 995
Images: 1
Quote:
Originally Posted by andreasduess View Post
A truck, which we know needs more than thirty additional feet to come to a stop even under ideal circumstances than the BMW, does not just ignore the 7500lbs in weight.
The BMW has a payload capacity of ~1100# (per door sticker on driver side B pillar). The tongue weight of a loaded 25 ft trailer is ~1000#. Add a driver and a passenger and it will be overloaded. When a vehicle is overloaded, the braking, cornering, handling all will deteriorate. You did not include this major point in your analysis. The truck, on the other hand, won't be overloaded and will not have a significant performance degradation.

Also, I have seen you mention several times that trailer brakes take care of stopping the trailer and if this is not the case then there must be something wrong with the set up. Just wondering, do you get the same stopping distance when you slam on the brake at 60 MPH with AND without your 8000# trailer in tow?

Claims such as this (or that some hitches "eliminate" sway) sure will make Sir Isaac Newton roll in his grave.
__________________
rostam is offline  
Old 01-02-2015, 08:46 AM   #36
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Quote:
Originally Posted by rostam View Post
The BMW has a payload capacity of ~1100# (per door sticker on driver side B pillar). The tongue weight of a loaded 25 ft trailer is ~1000#. Add a driver and a passenger and it will be overloaded. When a vehicle is overloaded, the braking, cornering, handling all will deteriorate. You did not include this major point in your analysis. The truck, on the other hand, won't be overloaded and will not have a significant performance degradation.

Also, I have seen you mention several times that trailer brakes take care of stopping the trailer and if this is not the case then there must be something wrong with the set up. Just wondering, do you get the same stopping distance when you slam on the brake at 60 MPH with AND without your 8000# trailer in tow?

Claims such as this (or that some hitches "eliminate" sway) sure will make Sir Isaac Newton roll in his grave.
Just so you understand, Rostam, we never pay ANY attention to weight ratings of tow vehicles here because we ALL know that those stupid automotive engineers know absolutely NOTHING about what they are doing. We also never figure the loaded weight of a vehicle when stopping, because that might be detrimental to "our" argument.
__________________
Regards,
Steve
SteveH is offline  
Old 01-02-2015, 08:52 AM   #37
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
Quote:
Originally Posted by dkottum View Post
This is not the best place to ask for towing opinions, it's always the same set of warnings and bets with little or no experience towing a medium-sized Airstream with a BMW X5.
And so it goes . . .
__________________
Doug and Cheryl
2012 FC RB, Michelin 16, ProPride 1400
2016 Ram 1500 Laramie Crew Cab 4X4 Ecodiesel 3.92 axles

The Truth is More Important Than the Facts
dkottum is offline  
Old 01-02-2015, 09:00 AM   #38
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Quote:
Originally Posted by dkottum View Post
And so it goes . . .
Definitely, and from BOTH directions, for sure.

Doug, please tell us how many miles you have driven towing your Airstream with a BMW.
__________________
Regards,
Steve
SteveH is offline  
Old 01-02-2015, 09:08 AM   #39
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
None, Steve. That's why I haven't told him he can't do it, but to work with Can-Am who set up his BMW in the first place and does this work routinely.

I did advise him on the only thing he asked about, a hitch. I recommended the Hensley/ProPride design because I have used it as well as other hitches on the same vehicle and it is a remarkable device, to say the least.
__________________
Doug and Cheryl
2012 FC RB, Michelin 16, ProPride 1400
2016 Ram 1500 Laramie Crew Cab 4X4 Ecodiesel 3.92 axles

The Truth is More Important Than the Facts
dkottum is offline  
Old 01-02-2015, 09:15 AM   #40
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Understand, Doug, and if you look back in the thread, no where have I told him not to do it either, or that it wouldn't work. I simply recommended an alternative hitch to him because he didn't want to "break the bank", and told him I didn't think he would like towing with the BMW. I've been on the underpowered side with a tow vehicle and know what it's like, and have seen many people thru the years with the same situation upgrading to a more powerful and capable tow vehicle.

I definitely agree with you about the PPP hitches, they are remarkable. But that's not to say they do not have their "issues". I don't believe there is a "perfect" hitch for every situation, and if there were, very shortly there would only be that one hitch manufactured. Almost every situation is a little different.
__________________
Regards,
Steve
SteveH is offline  
Old 01-02-2015, 09:33 AM   #41
Rivet Master
 
dkottum's Avatar
 
2012 25' Flying Cloud
Battle Lake , Minnesota
Join Date: Jun 2009
Posts: 7,716
No problem Steve.

Do you really think he's underpowered with some 400 ft lbs of (diesel) torque at a low rpm? He asking about a 25' Airstream, same model I tow.
__________________
Doug and Cheryl
2012 FC RB, Michelin 16, ProPride 1400
2016 Ram 1500 Laramie Crew Cab 4X4 Ecodiesel 3.92 axles

The Truth is More Important Than the Facts
dkottum is offline  
Old 01-02-2015, 09:43 AM   #42
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
In a lot of circumstances, yes. And do you know that he has the Diesel version, or is it gas. I don't remember that being stated.

And as we all know, there's a lot more to it than power. I was totally dissatisfied with my 5.3L GMC 1/2 ton pickup when I went from a vintage 23' to a later model 25' wide body. But, maybe I'm harder to please. I also keep going back to M. Stephen's experiment with a smaller car as a tow vehicle in the real world of Southern California in the summer. I don't want to be restricted to the weather, or altitude that I tow in, within reason.

Edit: Just looked back, and yes it is the "d" version, so that should be good for power, if things like the cooling system is up to it.
__________________

__________________
Regards,
Steve
SteveH is offline  
Closed Thread


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
BMW X5d and Weight Distributing Hitch OrangeKid Towing, Tow Vehicles & Hitches 130 04-16-2016 11:34 AM
Air Safe Air Hitch and WD hitch combo Uptightto Hitches, Couplers & Balls 18 12-22-2014 04:38 PM
Evergreen recreational vehicles, 2012 ever-lite 25rb; airstream eBay Watch Airstreams on eBay 0 10-23-2011 05:20 PM
BMW X5d, Mercedes GL350Blutec, Toureg TDI for 23’ Flying Cloud?? GreyLens Tow Vehicles 41 08-10-2010 11:01 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 09:33 AM.


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.