Forum Discussion

pianotuna's avatar
pianotuna
Nomad III
Nov 16, 2019

first report new springs with a surprize result

Hi,

I replaced the springs and had a leaf added on each side.

There were air bags that may have been improperly installed from the get go--7 inch bags in a 5 inch space, so the brackets torn away from the frame.

The air bags have been replaced with timbrens, which do not touch the frame--but might if I had full water tanks (66 gallons).


I put on new monro shocks at the rear.

Results (big surprize).

The RV rides 2.5 inches higher at the rear.

Ride is improved

And now the shock. It appears from early results that gas mileage has gone up by about 1.5 to 2 mpg. I've asked one mechanic and he is totally puzzled.

Anyone care to offer an explanation?
  • jjrbus's avatar
    jjrbus
    Explorer
    Nov 17, 2019
    pianotuna wrote:
    The wheels had been aligned less than 1000 miles ago.


    Again, not a mechanic. Cannot help but wonder if a vehicle with worn springs can be aligned properly. Guess it is better now, so enjoy the extra mpg.
  • time2roll's avatar
    time2roll
    Nomad
    Nov 17, 2019
    Just take it and don't look back. Sometimes you wonder why you waited so long.
  • JaxDad's avatar
    JaxDad
    Explorer III
    Nov 16, 2019
    As a pilot with a degree in aerospace engineering I can tell you that “parasitic losses” can manifest themselves in many weird and wonderful ways. Likewise the gains created by eliminating them, witness the little air tabs (originally designed for aircraft) that can measurably increase fuel mileage on a coach.

    In this case, I’d say an overloaded suspension created excessive (even if you weren’t aware of it, the slow creep is imperceptible) motion which created the losses you’re now recouping.
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Nov 16, 2019
    My E150 started sagging at about 5-7 years, especially when I hooked up my pop up to it (NO WDH). Added a leaf, What a difference ! It does sit a bit high when empty, but I would rather have that.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Nov 16, 2019
    Thanks for the replies so far. I'll know in about 2 weeks if the bump up in mileages was a wind effect--because by then I'll have about 2700 miles and several fuel fill ups.
  • Chris_Bryant's avatar
    Chris_Bryant
    Explorer II
    Nov 16, 2019
    You were going uphill before :)
    Seriously, I would bet aerodynamics relating to the underside of the coach.
  • jjrbus's avatar
    jjrbus
    Explorer
    Nov 16, 2019
    NOt a mechanic but have spent a lot of time on the forums over the years. One thing that is common and often reported is noticeable mpg improvement after wheel alignment. Did the bad springs contribute to poor alignment? But 1.5-2 that is a 20% improvement for most, far beyond anything I have heard. Start with checking your math LOL
  • MrWizard's avatar
    MrWizard
    Moderator
    Nov 16, 2019
    Weigh the axles/ wheel weight
    And compare to previous
    I think the center of gravity has moved
    Putting more weigh forward and less on the rear drive wheels
  • Terryallan's avatar
    Terryallan
    Explorer II
    Nov 16, 2019
    Could raising the rear have lowered the front, OR changed the angle of the wind over the front? would be my wild guess.

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