Sunline RV Forum
Sunline User Photos

Go Back   Sunline Coach Owner's Club > Technical Forums > Towing and Tow Vehicles
Click Here to Login

Join Sunline Club Forums Today


Reply
 
Thread Tools Search this Thread Display Modes
Old 08-22-2012, 10:22 PM   #21
Moderator
 
JohnB's Avatar
 
Join Date: Nov 2006
Location: Ohio
Posts: 10,340
SUN #89
JohnB is on a distinguished road
Mark,

Your tongue weight is:

TV GVW hitched with no WD – TV alone GVW = tongue weight

Filling in the numbers:
From Weight 2: (3,240 + 4,000) - From Weight 1: (3,580 + 2,700) = 960# tongue weight

How did you arrive at 700? I rechecked my math 3 times and still come up 960# Just checking I did not mix it up.

Your camper GVW is: GCW with no WD – TV only = TT GVW.
Filling in the numbers:
From Weight 2: 11,560 – From Weight 1: 6,280# = 5,280# GW of TT

960/5280 * 100 = 18.2% loaded tongue weight. It should tow stably.

Now to your WD adjustments. I need to type some more on this and I’m out of time tonight. I’m not a fan over overdriving the front end down 120# and I want to explain why but I’m out of time.

If you called Equal-I-zer and they told you it was OK to over drive the front end of the TV by 120#, well they changed their tune again….ERRRR. That is their old thinking from years ago of equal drop front and rear and not what they preach today following the new SAE towing guidelines. Or what many new truck manufactures recommend. I wanted to explain this so folks following along can see where I’m coming from and why, jsut need a little more time.

Do this for me, look up in your Toyota manual for towing with a WD hitch and see what they say about the front end. Toyota pulled their manuals from the open web unless you have a VIN so I cannot look it up for you.


Tell me what they recommend on the adjustment. It should be in the towing section. Copy the exact words they state, if they state anything. Not all brands actually tell you how to adjust the WD. Ford, GM and Dodge do now a days. They did not allows though.

Here see the top of page 18 of a new Equal-I-zer hitch. http://www.equalizerhitch.com/pdf/eq...anual_0111.pdf

They talk about being above unhitched height, not below it. They use to preach adjusting below unhitched height and that created havoc with some truck front ends, some truck receivers and oversteer. Understeer and oversteer - Wikipedia, the free encyclopedia

Be back on Thursday.

Thanks

John
__________________

__________________
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

Google Custom Search For Sunline Owners Club
JohnB is offline   Reply With Quote
Old 08-23-2012, 05:18 AM   #22
Senior Member
 
markbrit's Avatar
 
Join Date: May 2009
Posts: 124
SUN #856
markbrit is an unknown quantity at this point
Hi John,

I had a weird calculation on tongue weight, it was a guess by deducting trailer weight from WD and non WD slips. Was not sure how to calculate.

Wow 960 seems a bit heavy but it does tow nice. I guess trailers with kitchen in the front just weigh more in the front?

Both equalizer manual and Toyota manual suggest matching the unhitched weight on front axle. I too was concerned when crunching the numbers and that is why I called them. But 120 lbs is only about 3.5% of additional weight and axle is rated for 4k lbs. They felt it was within the tolerance.

When driving, truck does feel a bit more grippy to the ground but not feel pressed down into the road. I have a short road trip with the camper on Saturday and will test again.

I do have another weight slip and with less tension on spring arms get the following reading. So if needed I will adjust.

Ticket #4 - revised setup truck & trailer with WD hitch hooked up:
Steer Axle - 3,560 lbs
Drive Axle - 3,480 lbs
Trailer Axle - 4,500 lbs
Gross Weight - 11,540 lbs


Thanks for caring!
__________________

__________________
1997 Sunline Solaris 2653
2012 Toyota Tundra 5.7L Dbl Cab 8' Bed 4x4
markbrit is offline   Reply With Quote
Old 08-23-2012, 10:06 PM   #23
Moderator
 
JohnB's Avatar
 
Join Date: Nov 2006
Location: Ohio
Posts: 10,340
SUN #89
JohnB is on a distinguished road
Hi Mark,

Years ago it was thought that “equal squat” on the front and rear of the TV was the correct way to adjust WD. This concept on purpose drove the front end down below unhitched height and weight.

Tests by RVIA and SAE have since shown this is not a good thing to do any more. Actually back in the 70’s the NHTSA hads a towing study done pulling TT’s by TV’s of the time. The firm who did the study for NHSTA reported the same thing now that SAE has concluded. If you want, I can find that NHTSA study on line and link it here. I printed it off a few years ago and I still have the 1” thick report down in the basement.

To summarize this, the concerns are oversteer in the TV. Understeer and oversteer - Wikipedia, the free encyclopedia

When the front end of the truck is heavier then unhitched it creates more grip to the road. While this may sound like a good thing, it can be a really bad thing when towing a TT. The concern is the front end will “bite in” so to speak in a sharp turn and rather then sliding some like normal, it does not and sends the truck into jack knife. While this was known in the early 70’s by that NHTSA report, it never made it to a formal recommendation until a few years ago. This directly conflicted with the equal squat theory.

Equal-I-zer is now on board with “not” overdriving the front end below unhitched. In fact the actual directions state the front end should be above unhitched. On page 17 and 18 http://www.equalizerhitch.com/pdf/eq...anual_0111.pdf Equal-I-zer states the front end to be higher than unhitched.

Here is a link to what an RV member has claimed Equal-I-zer wrote him. The verbiage used and technical nature of the content suggests it is factual. It also matches page 17 and 18 of the Equal_I-zer manual.
RV.Net Open Roads Forum: Towing: Advice on setting up Equalizer Hithch...

Ford has also got on board with this same type of recommendation for WD adjustments. Here is right out of a 2012 F150. See page 276 under weight distribution hitches
http://www.motorcraftservice.com/pubs/content/~WOCF12/~MUS~LEN/36/12f12og3e.pdf

GM, is still stating to return the front end to unhitched height as this time.

The days of overdriving the front end are gone or going quickly.

There is also steering geometry involved. If you adjust the WD hitch to return to unhitched height or weight to slightly above, the steering geometry and tire wear is normal as your truck is riding around unhitched. Now there is another realization about a WD hitch. The WD on the front of the truck is changing as you tow. If you always towed on perfectly flat land then the WD would stay the same. The reality is, we go up RR track crossings, down steep hills, up over bumps, hard banked turns, any type of turn where the TT is on a different level of ground then the TV in a turn etc. When the truck and TT are at and angle to each other WD changes. The front end gets driven down or up pending which way the angle was between the TV and TT.

So if you are 120# heavy on purpose now, when you go up a quick hill like some RR track crossings, the WD bar loads up more and that 120# over drive can turn into 240# or higher over drive. Now you are really biting in if this is a turn as well. We cannot stop this shifting of WD, it just happens however we can control to not make it worse than it already is by not overdriving the front end.

Then there is the rear of the truck breaking free of traction in wet and or slippery conditions when the camper is pushing the truck. When this conditions happens, that extra weights on the rear axle helps more prevent a lose of traction then having extra weight on the front axle.

The truck receiver is in the middle of this too. If Toyota declares the front end to be returned to unhitch height and you have an OEM receiver, they may have designed that receiver to match up with the WD recommendation in the owner’s manual. They know a WD hitch takes a lot of ups and downs and make it heavy enough to take that. However they may not make to extra heavy to over drive the front end plus the normal towing dips and hills.

Toyota on the older Tacoma’s had a 750# rated WD receiver. I helped a few RV’ers with that truck after they bent their receiver up in the air. In this case one of them was using 1,000# WD bars on a 750# receiver. When these back flexes happen the receiver has to take it or permanently bend and his did. The other buddy had a Reese round bar head and a DC. He had a double whammy. The Reese round bar head has very little rear tilt. And his older Taco receiver really flexed. Basically with 750# WD bars he could not get his front end anywhere close to unhitched height on a 700# tongue weight. He was way high. He bought an aftermarket receiver and now all is OK.

I’m not saying your new receiver has the issues of the older ones, just don’t on purpose overdrive the front end for the reasons listed above.

Your spare weight set # 4 is a lot better. Basically with are back to unhitched weight on the front end. I would go with that setup.

Ticket #1 - truck with no trailer: (truck had full tank of gas, 400 lbs of passengers and 75 lbs of tools/spare tire.)
Steer Axle - 3,580 lbs
Drive Axle - 2,700 lbs


Front 120# heavy
Ticket #3 - truck & trailer with WD hitch hooked up:
Steer Axle - 3,700 lbs
Drive Axle - 3,280 lbs


Front 20# heavy
Ticket #4 - revised setup truck & trailer with WD hitch hooked up:
Steer Axle - 3,560 lbs
Drive Axle - 3,480 lbs


Hope this helps

John
__________________
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

Google Custom Search For Sunline Owners Club
JohnB is offline   Reply With Quote
Old 08-24-2012, 09:39 PM   #24
Senior Member
 
markbrit's Avatar
 
Join Date: May 2009
Posts: 124
SUN #856
markbrit is an unknown quantity at this point
OK John will switch it up to #4 and go 20 lbs lighter in the front end. Good info, thanks.
__________________

__________________
1997 Sunline Solaris 2653
2012 Toyota Tundra 5.7L Dbl Cab 8' Bed 4x4
markbrit is offline   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
Very neat, "low-cost" alternative to a "Bed Saver" EMD_Driver Sunline 5th Wheels 0 11-26-2011 05:20 PM
Can I upgrade to 14" tires from 13" tires? bdichristina Repairs and Maintenance 6 08-29-2011 12:04 PM
Sunline "SR" "Slide Room" and "Solaris" Decals EMD_Driver Accessories, Parts, Etc. For Sale 7 05-09-2011 08:53 PM
Sunline "SR" "Slide Room" Decal Availabl frank Accessories, Parts, Etc. For Sale 16 11-18-2009 04:09 PM
Larger Tires on the 15" Rims emam Modifications 15 06-12-2008 02:50 PM


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Sunline RV or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 03:52 AM.


×