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yeloduster · 04-22-2020, 07:10 AM

Hi everybody,

I thought I would tell y'all about the latest mod I made to my 2003 W20 Workhorse chassis. I've stated on this site several times that I think my motorhome handles pretty well for a house. However, I live in Colorado and have family in Wyoming. I often drive in high cross wind conditions. Any help is welcome.

I have the front Sumo Springs and didn't think they helped very much in normal driving and didn't like the price and installation hassle of the rear Sumo Springs for my W20 chassis.

While installing new rear tires I saw the rear bump stops. See the first picture below. That looked really familiar. Made me think I might be able to install a set of front Sumo Springs on the rear. After a little research I found that the rear Sumo Springs for a Workhorse P32 were the same dimensions as the fronts on a W series but rated for almost twice the weight. See picture 2 where the old bump stop and a P32 Sumo Spring are compared. Note that intended installation on a P32 uses a plastic spacer to increase the height.

Picture 3 shows the P32 Sumo Spring mounted on the rear of my W series with suspension hanging. I omitted the spacer. Picture 4 shows the Sumo with motorhome weight sitting on it. It is compressed about 1/2" while at rest. The 4th picture seems to show the Sumo leaning...it isn't...that was me leaning!

I removed the rear tires to do the install but it could be accomplished with the tires on. Took about an hour to do it all.

My test drive was on a section of highway with considerable construction. Lots of uneven surfaces and narrow lane alterations. My subjective opinion is that the rear Sumos had more affect than the fronts. Seemed to significantly reduce body roll on the uneven surface and on the diagonal road patches.

I'm happy! I spent about a 1/3 the money and an 1/8th the time. As slow as I am I'm sure that installation of the Sumos intended for the rear of the W20 would take me 8 hours!

Did I do this because I needed it! Or maybe....the quarantine has left me bored! Ahh! The mysteries of life!

coopcolt · 04-23-2020, 03:02 PM

I did much the same thing, I installed Firestone Air Bags.
And moved the Sumo inboard over the axle, so if the bags
were ever to fail. Helped all around, ride, sway and wind
or passing larger vehicles......coopcolt

yeloduster · 04-23-2020, 05:05 PM

Thanks for the feedback coopcolt,

Finding innovative ways to improve our home on wheels is always rewarding. I think there are MH that are so overweight (even from the factory) that the stiffer Sumo Springs designed for the rear of the W series workhorse chassis are needed. I didn't feel I needed that much and this was an easy solution.

My next and probably unneeded modification may be a rear track bar. Maybe I'll make my own!

CamJam1 · 04-23-2020, 05:30 PM

Let me be sure I understand this correctly. You put P32 rear Sumos on the back of your W-20 in the stock bump stop location?

I see the P32 rears are a lot less expensive than the W series, but they only have 2,800 lb capacity vs 5,600 for the W-22. How is that going to work?

I live in the southwest, so windy conditions are the norm for me too. Rear Sumos are the only thing I don't have now, so I'm interested in how this works out.

yeloduster · 04-23-2020, 07:47 PM

Thanks for the response CamJam1.

You asked a question. "they only have 2,800 lb capacity vs 5,600 for the W-22. How is that going to work?" Think of it like this, if you add no helper spring it has 0 lb capacity. By adding the P32 Sumo Springs to the rear of a W series you have increased the spring capacity by 2,800 lb. That is less than 5600 lb but it is 2800 lb more than 0 lb. Way I see it 2800 lb is more than 0 lb and I think for my application is enough.

Some people add air bags that are inflatable. Depending on the load they add or take away air to get the desired ride height/firmness desired. Maybe they only add 1000 lb capacity to get the desired result.

So it works well as long as you aren't so overloaded that 2800 lbs isn't enough.

In addition, I think with the Sumos the impact on the bump stop bracket is reduced when hitting a bad bump because the axle upward movement is controlled all the way up while with the stock bump stop must absorb a high velocity whack!

CamJam1 · 04-23-2020, 11:09 PM

I can see where they'd work fine most of the time. I guess I'd worry about what happens when they take a big whack. Too bad you can't use them together with the original bump stop as a sort of progressive spring.

Anyway, please keep us updated as to how they're working out for you.

vettenuts · 04-24-2020, 06:55 AM

I think it’s a great idea, would be very interested in your driving impressions once you can take it for a good run. I never did the rears because they were so much more than the fronts.

yeloduster · 04-24-2020, 07:12 AM

Maybe Governor Polis will let us out in a few weeks. I can't wait to get on the road.

We have a favorite spot that is quite secluded especially during the week. Planning on taking an ATV and do some riding on BLM and Forest land. It will be good to get out in the woods.

I'll add to this thread once I have some road time.

CamJam1 · 04-24-2020, 10:25 AM

Quote:

Originally Posted by yeloduster

Maybe Governor Polis will let us out in a few weeks. I can't wait to get on the road.

We have a favorite spot that is quite secluded especially during the week. Planning on taking an ATV and do some riding on BLM and Forest land. It will be good to get out in the woods.

I'll add to this thread once I have some road time.

I hear ya! I've had very limited seat time since I added my front Sumos and rear sway bar. Our big trip of the year was supposed to start about ten days from now, but that's off for now.

mcroadrunner · 04-25-2020, 10:02 PM

Yeloduster rear track bar will do wonders for tail wagging. See you have ultrarv motor & trans mods listed. What did you do & we're results worth it. Power, mileage, shifting, etc?

yeloduster · 04-26-2020, 07:21 AM

Quote:

Originally Posted by mcroadrunner

Yeloduster rear track bar will do wonders for tail wagging. See you have ultrarv motor & trans mods listed. What did you do & we're results worth it. Power, mileage, shifting, etc?

It would be nice for the rest of us if you added a signature line to your profile. That way we would know more about your RV and make it easier for us to relate to you.

Thanks for the comment on track bar. I had a 1988 P32 that really had the tail wagging problem. A track bar on it was truly needed especially when towing. My current motorhome doesn't exhibit that tendency. That is why I said probably unneeded modification. I know that it will help stabilize the MH if I encounter a stiff side wind gust.

I'll answer the mileage question first. Power improvements tend to get used! If you use the extra power you use more fuel. I live in Colorado and I have LOTS of opportunity to use the extra power. I have kept precise records of my fuel economy from the first mile I drove the MH. Fuel economy did not change at all! 7.1 MPG before UltraRv tune...7.1 MPG after UltraRv tune!

Before the UltraRv tune I made two long trips without a toad. I got 8.1 MPG on both those trips. Those miles at 8.1 are part of the average. I've not driven far without a trailer or toad since. If I manipulate the mileage for those 2 trips to make it similar to the mileage before UltraRv tune then my mileage improved from 6.95 to 7.1. That is about $3.00 per tank full at $3.00 per gallon. It certainly won't pay for itself.

The combination of more power and more precise shifting resulted in overall smoother performance. The extra power allowed the MH to maintain speed without downshifting as much and made for a much quieter ride. Especially noticeable was holding overdrive longer. Before the mods it didn't take much of a grade to cause a shift out of overdrive. It hangs in there much longer before shift now without losing speed.

If you choose to do this you might consider UltraRv Grade Brake. Make this modification at the same time. I can do my own shifting to control downhill speed. I don't think I need it.

I would do the UltrRV ECM and TCM tune again.

mcroadrunner · 04-28-2020, 08:43 PM

Still learning! How to add the signature line your speaking of? Have my info under my name to tap on, but how to ?

Arch Hoagland · 04-28-2020, 09:56 PM

Quote:

Originally Posted by mcroadrunner

Still learning! How to add the signature line your speaking of? Have my info under my name to tap on, but how to ?

Here ya go:

How to make a signature for your RV so we can serve you better.

1 .Click "User CP" on left side of the screen in about the middle.
2. Click "Edit Signature" on left side 7 bars down under Your Control Panel.
3. Fill out your signature information.
4. Click "Save Signature"

yeloduster · 05-24-2020, 08:11 AM

Well, I think the guvner let us out...even if he didn't we went anyway!

This last week we made a 375 mile long round trip to our favorite spot in the mountains. It turned out to have the perfect road conditions for a test of my experiment. We had smooth road, broken pavement, pot holes, construction and 20 miles gravel/dirt with cattle guards and rocks in the road and of course...lots of wind.

Just to let you know, I thought this coach drove well without adding anything. It had 45K miles when I bought it. The original equipment shocks were shot and I replaced them with Bilsteins. But...I live in Colorado and travel in Wyoming. Driving in wind is a very common occurrence. I was interested in spending a modest amount to increase wind safety.

I previously added Sumo Springs to the front. I reported that I didn't think they were a magic handling fix but I thought they were worth what I paid for them.

Then I added the P30 rear Sumo Springs to the Rear of my W20. Here's my impression.

The added spring rate in the rear had attributes that I hadn't anticipated. Bridge seams didn't jar the back of the coach as bad as before. Pot holes, broken pavement etc were less noticeable.

Side to side sway was noticeably reduced almost as though I had added more sway bar. My experience with extra stiff sway bars is they do reduce sway on the highway but a very low speeds when coming out of driveways the extra sway bar can add a rather violent side to side rocking. The extra spring rate didn't do that. Off angle driveways were taken with aplomb!

25-30 MPH Wind gusts were pretty much ignored. I could hear 'em, I could feel 'em in the steering wheel but the coach never budged. Same with meeting large trucks. I'm sure Wyoming can throw me some wind that will make white knuckle driving but 25-30 MPH side gusts just didn't.

The dirt road had some bad washboard. In the past washboard made the rear of the coach dance around a little as the rear differential bounced on the wash board. No so much now. I could feel the vibration from the washboard but very little dish rattling and no dancing.

Cattle guards...no problem. Same experience as bridge seams but MUCH slower.

Now the down side. I drive lots of curvy roads. Practically all my trips are mountain trips. I don't know if the added resistance to lean of the springs induced me to drive a little faster in the curves or this down side is just there regardless. There was a noticeable tendency to over steer a bit. That is I could feel the rear swing out a little. Not much and it seemed limited but definitely there. Maybe I need that track bar after all!

All in all a much better investment than the front Sumos! For my application the 5600 lb rear Sumo Springs may have induced a harsh ride that I didn't experience with the 2800 lb Sumo Springs.