King Pin to Nose Cone Measurement - 388M

[RJTimmer]

Hoping someone would be able to take a quick measurement for me.

I am wondering if you would be able to provide the swing radius dimension of the nose cone to the king pin on a 388M. I am setting up the B&W RVK3500 hitch in out truck this weekend, in anticipation of taking delivery of our newly ordered 388m next week Wednesday. I would like to not have to make adjustments to the hitch once i have it assembled.

Thank you for your assistance.

 

[Dave and Monica]

Just a suggestion but as you're installing a B&W hitch with 4" of fore/aft adjustment, why not set it closest to the tailgate as long as you're not behind the rear axle centreline. That'll give you the most clearance possible between the front cap and truck cab and tailgate to front storage compartment. That's where mine is on a B&W Patriot hitch.

Dave

 

[RJTimmer]

while that would work with out question, it would be detrimental to MPG by allowing more air to impact the nose cone causing more wind resistance thus less fuel mileage and power load placed on the engine.

I have a long box crew cab, so most likely i can go as far forward as the hitch will allow, with out issue, but I would rather know, than guess.


just trying to get a leg up on the set up, versus having to do all of at the dealer on delivery day...

 

[C&H Conner]

I suspect with a long bed you won't have any issues if you use mid or forward position. On the 380th I am using highest height setting in middle position right above the axle. Working well with a B&W with plenty of turn radius and rail room. Trailer sits level nose to rear.

Edit: thinking about mpg with different settings I can't imagine that much difference. Conceptually, there could be an mpg loss/gain but in real life situations with head or side winds I don't see it. I would love to see some hard numbers that shows if there are any gains made by moving kingpin forward. We are only talking about a few inches on a combination vehicle that is extremely lacking in aerodynamics.
Just my .02.

 

[RamGunner]

I'd recommend that you call B&W directly. I'm pretty sure they will recommend the forward position with a cc/lb. That will provide the greatest stability and load distribution.

 

[RJTimmer]

I know the mpg difference should be minimal, and the load difference while towing into head wind shouldn't be that noticeable..... However with my old truck (f350 ecsb) & RV (2004 32' Coachman Chapparel) I could feel the difference between the 3 positions on the slider hitch. And had a noticeable mpg difference over long distances at highway speeds. Nearly .7mpg at 65mph.

My goose pin is 51" from there cab, and 3" in front of the axle centerline. So if I set up the hitch to be 1" ahead of the axle center line I should be able to turn 90 degrees, with little concern. that leaves allot of space between the truck and nose cone, and most often I don't need or want to turn 90.... Seeing the hitch up as far forward and as low as possible also reduces the amount of chucking during gear changes and on less than good road surfaces.

Sent from my Nexus 6P using Tapatalk

 

[C&H Conner]

.7 mpg would run around 7-8% which is pretty significant. Agree with more chucking/axle bounce the further back you set the kingpin.

Have known several peeps that have tried an airfoil on the cab of the truck to improve fuel mileage while towing. Most remove it after seeing minimal gains in mpg.

 

[RJTimmer]

Our 7.3 was load temperamental for sure. It pulled the RV fine, but got very thirsty when asked to make more than 18psi of boost. If it had to maintained that psi or above, it would lose 1 to 2 mpg no matter the load being pulled.

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[Alaska]

RJ, did you ever get an answer to this? I have the same Q pretty much. Same RV. I'm trying to mount a Superglide in a 6 1/2' bed and want to know how far forward I can go to get some Wt off the rear axle. Tks

 

[Dub1417]

I am wondering the same. I just finished up my B&W 3500 and set it all the way forward/ highest position. With a long bed, I am more worried about the trailer riding level. We shall see this Friday after picking it up...

 

[RJTimmer]

Sorry for the late response.

As for our hitch set up, we have the BW Companion 35xx farthest forward (1" ahead of axle) , mid height is what we have ours set at. this provides a good bit of clearance to the cab, bed rail, and bed corner clearance for normal traveling. however, when we loaded up and went to the Johnson Valley desert last month with the TH loaded with the jeep, 2 weeks of supplies, and expecting at least 5 miles of offroad driving to get to our camping spot, I reset the hitch to be on center of the axle, and the highest setting. i'm glad i did. we came very close to bed rail contact at times while traversing the desert, and likely would have had contact if i hadn't raised the hitch. i did not like how it drove on teh highway though, and once we were out on flat ground, i reset the hitch to the 1" ahead and mid height position for the ride home. with it centered over the axle, and high we felt a considerable amount more porposing and bucking. it also felt less stable behind the truck, more affected by strong head winds and side winds, as well as a bit less stable when meeting semi's. If your wondering, we were only 500 lbs lighter on the way home than we were on the way down, and it was evenly distributed between the truck and trailer.


all in all, we had a great trip, averaged 8.9mpg traveling south from Fernley NV to Johnson Valley, and 8.7 on the way back north both ways at 70-75 mph. yes even in cali....but not while pulling up hill. my clutch decided to give up the ghost on the way home and severely limited the amount of power the truck would out put, which impacted speeds and gear selection on upgrades. it also may have been the reason we lost .2 mpg on the way home....

 

[RT1149]

Hi RJ, I have also just installed a Companion hitch in our truck prior to getting the call about our 350m is ready for pickup. My question for you is did you install a 7 pin trailer electrical socket somewhere in the bed or do you have enough length on the RV trailer wiring harness? If so, forward or aft of the wheelwell?

 

[RJTimmer]

Our ram has a 7 way in the box, left side behind the wheel well. I believe you can buy a patch cable and connector set that just plugs into your trucks wiring harness. You can plug in it at the bumper without any issues too.

 

[MitterMoe]

I went middle/middle on forward/back and up/down, rides great front axle weight only changed 20# empty to loaded per the axle scale at the truck stop, even did ok with the infernal wind storm across I40 this week and last 1000 mi of cross winds 20-40 and +gusts each way.