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Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

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Old 04-13-2014, 07:27 PM   #1
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Hello from SoCal!

Hi Folks:

I just picked up this 'new to me' 2005 Dodge 2500 HD 4x4 with the Cummins Turbo Diesel. As far as I know, it is stock with the exception of lift (don't know what type), and 305's instead of stock tires. I got the build sheet from Dodge, and this thing came loaded. It had the 3.73 gears; don't know how the larger tires will affect it.

I didn't get it because it was particularly fuel efficient, but I needed something to pull my 25' toy hauler. I joined this site so I could keep an eye on my fuel economy, and see if there are ways I can improve it. Currently, my best is about 14.7, with 12.5 being the average with mixed driving, including some towing. I obey the posted limit (55 in California) when towing both for economy, and the fact that I'm a new tow driver. I'm going to drive the truck as is for now, probably doing an ahead of schedule oil change before our cross country trip this summer.

That's all for now..
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Old 04-14-2014, 05:48 AM   #2
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Welcome.

Going back to stock tires and lift will help with fuel economy. Taller means more frontal area and more air going under the truck. Both are bad for aerodynamics.
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Old 04-14-2014, 06:20 AM   #3
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With different-size tires and no adjustment made, the odometer and speedometer (and any onboard MPG display, if equipped) are reading wrong. The speedometer effect has a secondary effect of possibly throwing an automatic transmission's shift calculations slightly out of whack.

Can you give us the entire size of the current tires, and of the original ones? All you've told us is width. It will look like 305/75-17, may say LT305/75R17, etc. With both complete sizes you can use a tire size calculator to see exactly how the circumference differs, and therefore how your gearing and speedometer/odometer/fuel economy calculation are affected.

Bigger tires have more load capacity at the same pressure. Smaller tires give you shorter gearing which is generally preferred for towing, though your diesel probably laughs it off.

To what lengths are you interested in going for fuel economy? Aerodynamic modifications are going to be your big gains, but could get visually unattractive if taken to extremes.

Tangent: For towing safety, please make sure:
- all tires are inflated as recommended or to their maximum, checked daily
- you are using the recommended hitch, including spring bars if a weight-distributing hitch is recommended
- your electric brakes are properly adjusted and you know how they operate, and you test them daily
- you have sufficient mirrors -- and when not towing, fold/telescope them back in to their non-towing position
- weight is distributed well; this is probably tough with a toy hauler
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Old 04-14-2014, 07:05 AM   #4
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Hello from SoCal

Hello and thanks to all who responded. I do know that the lift and bigger tires aren't helpful with mpg. However, that is the way I purchased the truck, and I have neither the skills or resources to return it to stock height and tires. Frankly, I like the aggressive appearance, and know I'm sacrificing for cosmetics. Additionally, the weight distribution hitch was set up for the trucks' current height. Stock height/tires may be a consideration in the future, as we are both short (under 5'5) and somewhat busted up females, so getting in and out is an adventure. We're already joking we may need a ladder/ramp for both us and the dogs, LOL!

Now to respond as to tire size. Currently, it has 305/65/17; the build sheet shows 265/70/17 as stock.

I have a question about daily check of trailer electric brakes. It is parked in our driveway on an incline with X-chocks. How would I check brakes on it daily? As far as function, I have a brake controller in the truck with the appropriate 7-pin connection. Is there anything else I need to know? I know I can increase or decrease brake from the controller. Yes, I have the proper tow setup. A WD hitch with stabilizing bars and sway control were professionally installed, so I'm comfortable with that.

As to the speedometer, I use my GPS to monitor my speed, and I'm going to guess that the previous owner had the speedo calibrated for the larger tires, because it seems accurate. I'm doing some highway driving today, so I'll check it again. What I've learned from this forum and others is that the greatest effect on mpg is your driving habits. That means I'm going to have to adjust mine to 'granny' level (since I am one). That will be difficult, as I like to step on it a bit; I don't like frequent fuel stops though. So $$ will force me to slow down.

That's it for this installment, and thanks again to everyone!
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Old 04-14-2014, 09:01 AM   #5
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Ok, the tire circumference is only 2% different. That's a good thing. I wouldn't worry about changing back to stock size for such a small difference. Wider tires are nice, especially for towing. They're wider but not really taller...we're talking 1.7mph difference at 55mph.

By "daily", I really meant every day that you drive it. No need to check the trailer's brakes while it's parked for days at a time. When you tow it, before you go far, press the button on the brake controller while rolling at 20mph (or whatever speed) and see if it slows/stops the rig.

That reminds me, though: Check the breakaway brake system periodically too by pulling the pin and seeing if your truck has a harder time dragging the trailer.

You should familiarize yourself with your brake controller by reading its manual, it's important stuff. AFAIK the most common kind has an inertia sensor in it that senses deceleration and applies the brakes accordingly. You'll want to be aware of that when descending hills, though I imagine it has a level sensor to compensate for that issue. There may be more than one adjustment, and the manual will tell you how to optimize them. Nobody likes reading manuals and usually you can get away with not doing so, but brake controller manuals are really worth reading, at least the parts describing its driving characteristics and adjustments.

I'm glad you're using a weight-distributing hitch. Make sure to tension the spring bars properly. If it's the most common design, the spring bars have chains that hook to the trailer tongue. A nice trick is to hook up the ball hitch, then use the trailer tongue jack to raise both vehicles at the hitch so the spring bar chain hooks don't require a lot of arm strength to flip.

If you have a friction-operated sway control attachment, try driving with and without it, and with it adjusted differently. Not only is the experience good, but if your rig tows perfectly steadily (even in emergency maneuvers) without it then you might be safer without it. I've never used mine because my rig is so stable, but I've heard they can make things get dicey when traction is limited (i.e. sand, snow, rain, etc).

Driving habits are the greatest effect in general, but with a trailer like that there is an opportunity for VERY effective (but as I said earlier, ugly) aerodynamic improvements (easy - cleaning up protrusions on sides and roof; ugly - topper cap on truck bed, boattail rear and similar front attachments on trailer) that could easily be worth more than any granny-driving.

I hope somebody with experience towing something boxy with a diesel and an automatic can chime in with driving tips, I don't have much that applies other than reduced speed (which you already know). I know plenty of stuff that squeezes efficiency from gas engines that wouldn't apply to diesels, and plenty of stuff you can do with a nimble car that would never work with a truck and trailer.

So, do you park anything fun in that toy hauler?
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Old 04-14-2014, 03:09 PM   #6
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Hey holy cow thanks! I didn't receive a manual for the brake controller. I'll have to see if I can find it online. You're spot on about the hitching system, and we've already been using the trick you described for the spring bars.

Now the button you're talking about on the brake controller, is that the one that decreases or increases brake tension? I was going to ask about what pin you're talking about pulling, but I presume you mean the 7-pin connector coming from the trailer, ok. What is this 'boattail rear you speak of? And there is no way I'm putting a topper on this thing...butt ugly!

No toys just yet..the combined toy hauler and truck purchase dented me just a bit. Actually, the toy hauler was a trade for the Class B van we had before, and we came out great on that! I did acquire a truck payment, but that would've been the case anyway as we were moving to some sort of towable RV. We decided on a toy hauler because we didn't want plush; the space available, and the fact that it, like us and our pets, is rough use. Pretty sure some sort of toy's gonna sit in there @ some point, even if just a couple of putt-putt scooters for a couple of old broads..hehe
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Old 04-14-2014, 05:00 PM   #7
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Hopefully you can find the brake controller's manual online.

The brake controller should have a big fat button on the front that activates the trailer brakes without requiring the truck to do any braking. It might just look like a blank panel, not a button at all, but if you press it the trailer's electric brakes will activate. It can be used for testing, advanced backing up maneuvers when you want to jacknife, emergencies, and (most importantly) ending a sway situation.

On that last point: If the trailer starts wagging like a dog's tail behind you, activating the trailer brakes while staying on the gas and not braking the truck will pull it straight. Then you pull over and change your underwear...at least you've got a shower and clean clothes right behind your truck! Also if there's insufficient traction and the trailer is coming around, again, braking the trailer without braking the truck can help pull it straight.

...ok I just looked up one of the more popular modern models, the Tekonsha Prodigy P2. Instead of a button it has a little lever. I thought they all had a big button that's easy to press in an emergency while you keep your eyes on the road.

Don't be scared, I'm just discussing emergency procedures...hopefully you NEVER need to exercise that knowledge.

The breakaway brake system pin is on the tongue and has a little cable like the one on a pen at the bank, with a hook or carabiner at the end. You clip it to your bumper, and if the trailer comes unhitched, the pin is pulled out and the trailer's brakes activate using a battery.

Its location might be like so:


and it might look like one of these:



If the topper is too ugly, the boattail will be WAY too ugly. Here's a really nicely done one (with a front piece too), and it's definitely a head-turner...


If you could make one of these, at least it would fold up nicely when parked:


Good idea getting a garage and less living space rather than a big trailer that's all living space. I bought mine ten years ago, about the same length but no garage, for just my wife and I...it's very comfortable but we use the extra beds for storage anyway. At least it has great weight distribution and tows with incredibly good stability.
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