Community Forums

LVRVLUVR · 11-23-2016, 08:27 AM

what rpms does your class c run...450-or e350 chassis..?

I have found that they seem to be geared lower than the A's for some reason
coming back croos country, I noticed that the dynamax was rinning at 3000 rpms at 70 mph... it still has the little 225-75-16's on it ...
I think it way over revs and doesn't get good use of the 5 speed...

when I take off from a light it is already in 3rd befoe I cross the street...

that has to kill the MPG...

best I got was 8 mpg running on flat at 70-75
but the rpms were around 3000....

I always change out the tires to 235-85-16's they carry more weight, ride smoother.. and lift the coach about 1.5 inches... they slow down the rpms
speedo ends up at 65mph... reads 60 mph...so the rpms also drop about 400

they pull the hills better in 4th and not over reving so much

Dave11 · 11-23-2016, 05:28 PM

On my 2009 E-450 I think I am at 2,500 at 65mph, can see 10 mpg when no head wind.

nothermark · 11-23-2016, 05:38 PM

With our E-450 I see around 2500 at 65 mph, seldom exceed 65 mph. Run around 7 mpg with or without the towed. The difference seems to be how much we down shift and slow down on hills.

radams · 11-23-2016, 05:54 PM

That's good information to have and a creative way to address it with the tire sizes. Did it throw your speedometer off by any meaningful amount?

Santara · 11-23-2016, 06:05 PM

Quote:

Originally Posted by LVRVLUVR

what rpms does your class c run...450-or e350 chassis..?

I have found that they seem to be geared lower than the A's for some reason
coming back croos country, I noticed that the dynamax was rinning at 3000 rpms at 70 mph... it still has the little 225-75-16's on it ...
I think it way over revs and doesn't get good use of the 5 speed...

when I take off from a light it is already in 3rd befoe I cross the street...

that has to kill the MPG...

best I got was 8 mpg running on flat at 70-75
but the rpms were around 3000....

I always change out the tires to 235-85-16's they carry more weight, ride smoother.. and lift the coach about 1.5 inches... they slow down the rpms
speedo ends up at 65mph... reads 60 mph...so the rpms also drop about 400

they pull the hills better in 4th and not over reving so much

thought dynamax was diesel

tderonne · 11-23-2016, 07:46 PM

An E450 with a 4.56 axle, 225/75R16 tires, 4R100 or 5R110 in top gear, will turn about 2679 RPM at 70MPH (2870 @ 75, 2488 @ 65). Maybe your tach is a bit optimistic?

An E350 with a 4.10 axle would be spinning about 2409 RPM at 70 MPH.

(My F53 4 speed, with 245/70R19.5 tires and a 5.38 axle turns 2793 RPM @ 70 MPH. New ones with different axles and the 6 speed are a bit different, but mine is close to an E450.)

KAttkisson · 11-24-2016, 03:55 AM

Be careful upsizing your tires-you have to maintain clearance between the tires when loaded. Any rubbing will build heat in a hurry.(experienced this) There are spacer rings available but then you run into things like are the studs long enough and is there exterior clearance with the coach. Also because of the physics lower rpm does not always translate to higher mpg.

beeman12 · 11-24-2016, 04:10 AM

Invest in a 5 star tuner. Make a lot of difference on 2001 e 450. Less
downshifting . RPM at 62 mph is 2275. 8.2 mpg loaded. Best was 9.5 with tail wind. Not looking for great mileage. No need to hurry got all day.

LVRVLUVR · 11-25-2016, 07:22 AM

Quote:

Originally Posted by radams

That's good information to have and a creative way to address it with the tire sizes. Did it throw your speedometer off by any meaningful amount?

at 65 it reads 60 gps....

LVRVLUVR · 11-25-2016, 07:30 AM

Quote:

Originally Posted by KAttkisson

Be careful upsizing your tires-you have to maintain clearance between the tires when loaded. Any rubbing will build heat in a hurry.(experienced this) There are spacer rings available but then you run into things like are the studs long enough and is there exterior clearance with the coach. Also because of the physics lower rpm does not always translate to higher mpg.

the big difference is the height the stock rims are designed to run 225 or 235 tires and come that way from ford in different applications...the 225 is just too small of a tire and pushes the limit to gvw... where as the 235 85 16 allows for a smoother better ride , more weight capacity, and better MPG...

just a (what I have done) to share ...some will find it helpful and something to think about...

I have found, that the although though is that the ford needs all those rpms to make power,, it's not true... the v-10 has a lot of grunt power at 2000 rpms... and to futher prove that... ford now has lowered the rpm limit to 4200

LVRVLUVR · 11-25-2016, 07:31 AM

Quote:

Originally Posted by Santara

thought dynamax was diesel

that would be a chevy motor.... the brand Dynamax uses both gas and diesel chassis'

LVRVLUVR · 11-25-2016, 07:42 AM

watch the video of this class A..v-10 pulling a loaded triple axel trailer up a small grade...it's a 2016 with a 6 speed..

https://youtu.be/UE3ADWc0kH8

Dave11 · 11-25-2016, 09:24 AM

Don't forget the V-10 in a class A is not the same as the one in a class C. Also, different transmissions, rear ends and programming.

Rvlegaleagle · 12-18-2016, 09:29 AM

So am I getting this right? You can put the 235 tires in place of the 225 on the e-450 chassis, all around, without any issues? Lets say on the new 2016 or 2017 ford e-450 cutaway chassis on a class C rig?