MM Chassis Drives Like A Hunting Dog

[GaryKD]

I'm looking for those having a Spartan Mountain Master chassis (IFS front end) and are required to provide input to the steering wheel almost 100% of the time at highway speeds (above 50 mph).

Is there anyone else out there who must do this or am I the only one? What have you done to eliminate the requirement for constant steering wheel input?

My coach is:
2005 Newmar KSDP 3910
39 Ft. long
Spartan MM chassis
Cummins ISC 330 HP
12K miles on the coach and this has been a problem from day 1.

Over 50 mph this coach is the worst of all that I have owned (first was in 1978). It drives like a beagle hunting for rabbits. If the road is well paved, level and there is no wind everything is fine. Very little steering wheel input is needed. Unfortunately, these circumstances do not happen very often. When there is pavement imperfections, side wind (trucks or mother nature) or anything that allows the weight of the coach to shift, considerable and almost constant correction is needed to keep the coach straight. I have already:
1. Cummins authorized Service center (twice) nothing out of spec found. Nothing loose or worn.
2. Selling dealer (twice) adjusted ride height (very minor)
3. Michelin (3 times) front tires replaced and all 6 tires spin balenced. The ride is now very smooth, but this did not help the tracking problem.
4. Front end aligned 2 times, by different alignment shops 1500 miles apart. Both techs drove the coach and said it was "squirly" (my words, their words could not be posted here)
5. Front end alignment checked (3rd time) and no adjustments were necessary. All alignment specs are dead center of the specification.
6. Fully loaded for travel, the coach's four corners were weighted by Florida DOT. The coash is almost dead even balanced. 50 lbs more on the left front and 150 lbs more on the right read. (congrats to Newmar). 1650 lbs under GAWR on the front and 1350 lbs under GAWR on the rear.

I finally bought my way out of the problem, by making the pilgrimage to San Antonio, Texas. There I had the Howard Precision Steering System installed. This is the only steering system I could find available for IFS front ends and to the public. The Howard Steering System is the end of my story. It works better than advertised. The coach now drives better than my previous coaches.

After 26 years of driving coaches, I have a feeling I am covering up the problem. Has anybody else found the solution?
thanks

[GaryKD]

I'm looking for those having a Spartan Mountain Master chassis (IFS front end) and are required to provide input to the steering wheel almost 100% of the time at highway speeds (above 50 mph).

Is there anyone else out there who must do this or am I the only one? What have you done to eliminate the requirement for constant steering wheel input?

My coach is:
2005 Newmar KSDP 3910
39 Ft. long
Spartan MM chassis
Cummins ISC 330 HP
12K miles on the coach and this has been a problem from day 1.

Over 50 mph this coach is the worst of all that I have owned (first was in 1978). It drives like a beagle hunting for rabbits. If the road is well paved, level and there is no wind everything is fine. Very little steering wheel input is needed. Unfortunately, these circumstances do not happen very often. When there is pavement imperfections, side wind (trucks or mother nature) or anything that allows the weight of the coach to shift, considerable and almost constant correction is needed to keep the coach straight. I have already:
1. Cummins authorized Service center (twice) nothing out of spec found. Nothing loose or worn.
2. Selling dealer (twice) adjusted ride height (very minor)
3. Michelin (3 times) front tires replaced and all 6 tires spin balenced. The ride is now very smooth, but this did not help the tracking problem.
4. Front end aligned 2 times, by different alignment shops 1500 miles apart. Both techs drove the coach and said it was "squirly" (my words, their words could not be posted here)
5. Front end alignment checked (3rd time) and no adjustments were necessary. All alignment specs are dead center of the specification.
6. Fully loaded for travel, the coach's four corners were weighted by Florida DOT. The coash is almost dead even balanced. 50 lbs more on the left front and 150 lbs more on the right read. (congrats to Newmar). 1650 lbs under GAWR on the front and 1350 lbs under GAWR on the rear.

I finally bought my way out of the problem, by making the pilgrimage to San Antonio, Texas. There I had the Howard Precision Steering System installed. This is the only steering system I could find available for IFS front ends and to the public. The Howard Steering System is the end of my story. It works better than advertised. The coach now drives better than my previous coaches.

After 26 years of driving coaches, I have a feeling I am covering up the problem. Has anybody else found the solution?
thanks

[rebelsbeach]

Gary,

I recently traded an '06 Winnebago Vectra with the IFS on a Freightliner Chassis for the '07 Essex with TRW's Comfort Drive.
Not my point, but I can assure you the Comfort Drive (real TRW name is Column Drive) is a great ride....
Where yours has a dial and an on/off switch, mine is fully automatic which may be the distinct difference.

What I do want to make you aware of is that fellow iRV2 member John Canfield added the Howard Precision Center Steer to his '04
Horizon within the past few months and is extremely happy with it.
Do a search for the Howard product or check out janeandjohn.org for his rv page,to see his review experiences with it.

[GaryKD]

Bob,
Thanks for the quick reply. John and I have traded information on this problem and I got my Howard System about a month after he got his. A short story on this is that I was making my appointment, with Iron Horse RV, at the time John was in having his installed. After mine was installed (it took a week, custom build) the guy from Howard said he thought John's installation was hard until he did mine!

[tmitchell]

I have a 2004 DSDP 3807 on a Spartan chassis with IFS. I have weighed all 4 corners and keep 110 psi in the front tires and 90 psi in the rear, per the Michelin tire chart for my 275/70R22.5 tires.
I have put a little over 27,000 miles on, of which 3 of the trips averaged around 5,000 miles a piece. On my long trips I put in fairly long driving days. I would put my MH up against any comparable model as far as handling and tracking. The only complaint I have is the harsh ride I get on some of the rough road surfaces in the northeast states.
I went to the dealer last Mon.to complain about the harsh ride and told them I would probably go to 275/80s on the front to help the ride. They suggested I have them check the ride height and reset as necessary. They said this should allevelate some of the harshness.
I had the ride height set to spec. The front was 5/16" too low and the rear was 1/4" too high. I couldn't tell any difference in the ride on the 30 mile trip home, but it always has a good ride on the FL highways.

[GaryKD]

Tom,
Your right, Florida roads are very smooth and we who live here are spoiled. I have always carried 95 in the front and 85 in the rear. This is per Michelin web tire charts and a call to Michelin confirm (the rear at 85 seemed low to me). I have 275X70X22.5 tires and load range J. My ride is very smooth. No complaints on the ride. My problem is with the tracking. It is solved now, with the Howard system. I am trying to see if anybody has come up with another solution.

[tmitchell]

Gary,
Glad to read that the Howard system cured your problem.
I wish I could run just 95 psi in the front tires, instead of the 110 psi. Even when I up size to the 275/80s, I will still need 100 psi in the front. I wonder why your KSDP weighs that much lighter on the front axle than my DSDP?
Both MHs are on the same chassis. Does yours have IFS? Has your ride height been checked?
As I mentioned earlier, Mon. I had my ride height checked and set to spec.
I kept my old ride height measurements. If my handling degrades at all because of resetting to spec. I will not hesitate to go back to the old settings.
Tom

[GaryKD]

Tom,
Per my OP, my chassis is IFS (my first IFS front end) and ride height has been checked by the dealer (twice).

Are your tires load range J? If not, that may be the difference in tire pressure. Some of the following may be redundant, but this is the complete tire information.

Tires and weights are as follows:
Front = Michelin XZE2+ 275X70X22.5 LRJ.
Front GAWR 12000
Left = 5200
Right = 5150

Rear = Michelin XZA1 275X70X22.5 LRJ
Rear GAWR 20000
Left = 9250
Right = 9400

Per Michelin pressure charts and confirmed with a call to Michelin, I carry 95 lbs in the front and 85 lbs in the rear tires. The coach rides very smooth.

[GaryKD]

This is an update. Spartan looked at my coach chassis at the Essex Junction Rally. They confirmed there is nothing visibly wrong. I have been scheduled for Charlotte later this month. I feel better since they seemed to thoroughly understand what the problem is and I am not the only one. My hopes are high. I will keep everyone posted via this thread.

[GaryKD]

I was at Spartan Motors on October 26 and 27th. The quick summary is the driveability of the coach is the best Spartan can make it. While I am not jumping with joy, the coach is now better than before the appointment. Now I can drive the coach without the Howard Precision Steering System turned on. Before the appointment, I could not do this at highway speeds and considered the coach a safety hazzard. It still requires more driver input than I like. With the Howard System the coach is solid.

The Spartan techs took a lot of time and went over all the chassis adjustments. Caster, camber, toe and ride height were adjusted slightly. What seemed to make the biggest difference was the thrust angle degree and air bag pressure adjustments.

The coach was found with all the above mentioned adjustments within Spartan specifications. It was the factory technicians tweaking all the adjustments so they come together and make the coach the best it can be that seems to have made the difference. I am not sure this skill is found anywhere but at Spartan.

The air bags were carrying about 100 lbs and they now carry about 130 lbs of pressure. With my guages, it is difficult to be accurate. From start to finish, the Spartan people were very friendly, knowledgeable and professional.

After the final test ride, it was explained that the IFS front end has considerably more flex in it than the straight axle front ends, I am used to. When the coach is pushed (from any force) the IFS front end is going to flex and follow the direction the coach is pushed. While straight axle coaches do the same thing, they are much more rigid. They will flex less and will have less tendency to follow where the coach is being pushed.

On a side note, if you get a chance, attend the Spartan plant floor tour. Mike was our tour guide. Mike and the tour are outstanding. Newmar could learn on how to conduct a tour from watching how Spartan does their tours.

Spartan provides 20 spaces for customers having service work done at the Spartan facility. Look in the Campground Section of this iRV2 site for my comments on what to expect.