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Old 12-06-2021, 01:36 PM   #1
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DIY Caster Adjustment

Our motorhome is on a 2003 E350 chassis. The only issue with the handling is a significant bump steer. My previous motorhome was on a 2013 F53 chassis with a short wheelbase and a long rear overhang so I may not be as sensitive to other issues.

An alignment sheet provided by the previous owner shows:

Camber Left +1/4 degrees, Right -1/4 degrees
Caster Left + 3-1/2 degrees, Right + 3-3/4 degrees
Toe Left 0 degrees, Right +1/32 degrees

I'm thinking an increase of 2 degrees caster to both sides will fix the bump steer. I plan to purchase the Specialty Products Company part number 23188 https://www.spcalignment.com/index.p...tion&pid=23188 bushings and install them with the slots facing the rear of the motorhome. This corresponds to position number 3 on the installation chart.

Is there any reason I can't do this myself? Is there any reason for any of the other alignment parameters to change after the bushing is installed? The job seems too simple to pay someone $300 to do.
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Old 12-06-2021, 01:55 PM   #2
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No particular reason you couldn't do this, depends on your skillset and tools.

I would add though that you need to know first what bushings you already have installed, if it is a 3 degree and you replace it with a 2 degree then you are going backwards. If it is the factory bushings then I suspect that they are zero or close to zero so the one you linked to may be fine. Keep in mind, that you should get an alignment after installation although if you don't touch the toe in or out then all you have to deal with is the camber (other than your caster change) which you may be able to keep the same.

I would suggest this one instead (x2) and take it to the alignment shop and have them install and align the front end. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 12-06-2021, 05:09 PM   #3
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Ford ships all E350/E450 cut aways with identical fixed, non adjustable
caster/camber sleeves, "one size fits all". You can recognize these sleeves because they are keyed and cannot be rotated. They are marked "F8UA-AA 0+.25" on the passenger side and "E97A-CA +0-0" on the drivers side.

The passenger side marking is 0 Degrees Camber and +0.25 Caster.
The drivers side marking is 0 Degrees Camber and 0 Degrees Caster.

The actual runtime caster depends on the nose up/down attitude of the chassis.

The typical nose attitude is about 1 degree nose down which results in the runtime caster of about +3.5 degrees (the 2 degree caster collar will give you about +5.5 degrees runtime caster).

Changing the caster DOES change the TOE.

If you can change a front tire then you can install the new caster collar. Use all of the 2 degrees for caster and let the camber be whatever it was when you started. But you must set the toe, a tape measure will do the job.


https://www.rvforum.net/threads/e350...-caster.40337/
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Old 12-06-2021, 07:29 PM   #4
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Your best bet is to take it a good truck alignment shop and get the right cams installed and set, but only with the RV fully loaded as you normally travel. Aligning the Ford Twin I-Beam is part science and part art and experience. Not every alignment shop can align a Ford Twin I-Beam shop.

Ken
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Old 12-06-2021, 07:56 PM   #5
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I did the driveway bushing replacement and alignment on my used E450 RV. I certainly was not the first or the last but I will share some of my experiences. You are correct is stating the actual bushing replacement is pretty straight forward.

FYI, After adding + caster I still had a steering issue. Most notably on curves or with gentle body rolls. It felt almost as if you could not hold a constant arcing turn. (Your bump steer???) It was corrected by replacing the steering radius bushings. The bushings were not OEM and found to visibly misaligned and more oval than round. Possibly misaligned by previous installer.

IMO, A toe adjustment will be required after an alignment bushing change.

I used the fully adjustable bushings. Ie, inner and outer sleeves that rotates independently.
My final adjustment was;
DS has a Moog 4 deg bushing set at GH/C, original OEM was +0, -1/4 installed at 8 o’clock position, This bushing had a finer adjustment that made it easier to achieve the cross camber and cross caster readings that I could live with.
PS has Ingalls 594 install at T/A, original OEM was +1/4,+1/4 installed at 2 o’clock position
Camber/ caster readings were taken after a digital magnetic level on the frame just behind the cab indicated level, 0 deg. Nose up or nose down will affect the indicated readings.
After readings,
Camber caster
DS +1/4 deg 6 1/2 deg
PS +3/8 deg 6 3/4 deg

My problem was I found differing information on which was caster and which is camber on the OEM bushings markings, This required for me that I would need to figure out how to measure Caster/Camber before I could proceed.

The adjustable bushing manufactures recommended installation and check with a 0,0 bushing to determine the as built condition prior to installing the adjustable bushing. If you could determine the as built (0.0) caster/camber values from reading the installed bushings and some simple math, I believe you could proceed as you have speculated with likely only a Toe reset. I can post a few pics of the tools I used to check/verify my alignment if you would like.

This is the misaligned radius bushing.

Good luck, your results may vary.
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Old 12-07-2021, 06:51 AM   #6
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Quote:
Originally Posted by Harvard View Post
Ford ships all E350/E450 cut aways with identical fixed, non adjustable
caster/camber sleeves, "one size fits all". You can recognize these sleeves because they are keyed and cannot be rotated. They are marked "F8UA-AA 0+.25" on the passenger side and "E97A-CA +0-0" on the drivers side.

The passenger side marking is 0 Degrees Camber and +0.25 Caster.
The drivers side marking is 0 Degrees Camber and 0 Degrees Caster.

The actual runtime caster depends on the nose up/down attitude of the chassis.

The typical nose attitude is about 1 degree nose down which results in the runtime caster of about +3.5 degrees (the 2 degree caster collar will give you about +5.5 degrees runtime caster).

Changing the caster DOES change the TOE.

If you can change a front tire then you can install the new caster collar. Use all of the 2 degrees for caster and let the camber be whatever it was when you started. But you must set the toe, a tape measure will do the job.


https://www.rvforum.net/threads/e350...-caster.40337/

Great info. The existing alignment does show the passenger side has +0.25 more caster angle. So to add +2 degrees to each side I'll need the passenger side bushing to be +0.25 more caster than the driver side (so p/n 23189).



And the toe does change! Well I'll just check it before and after the bushing replacement to verify. If I have to adjust it I will go slightly negative (no more than 1/8") as it is slightly positive (toed out) now and a slight toe in really improved the handling of my previous motorhome. The tires will age out long before any excessive wear is an issue.


Also my definition of "bump steer" is when the steering wheel jerks left or right when going over a bump with one of the front wheels.
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Old 12-07-2021, 11:50 AM   #7
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Quote:
Originally Posted by TXiceman View Post
Your best bet is to take it a good truck alignment shop and get the right cams installed and set, but only with the RV fully loaded as you normally travel. Aligning the Ford Twin I-Beam is part science and part art and experience. Not every alignment shop can align a Ford Twin I-Beam shop.

Ken
This is what I did. Under $150 and an improvement in handling.
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Old 12-08-2021, 05:48 AM   #8
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I have a 2018 E450 chassis and they were able to get roughly (can't remember exactly) 6 degrees out of the OEM Caster bushings. I bought the ones you have and sent them back.

An alignment should cost around $150.00- $200.00. Mess up and you will be buying new tires for sure and paying for an alignment. JMHO
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Old 12-08-2021, 07:59 AM   #9
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Following this because our old '83 Winnebago Chieftain had a bad case of bump steer. Adding caster will promote better steering centering, but will not reduce bump steer. Per Google:

What is Bump Steer? It is the term for when your wheels steer themselves without input from the steering wheel. It is caused by bumps in the road or track interacting with improper length or angle of your suspension or steering linkages. Most car builders design their cars so that the effects of bump steer are minimal.

Bump steer can be adjusted by moving any of the front suspension components pickup points Up, down, in or out. For example: Say the inner tie rod mounting point is moved up either by moving the rack or modifying the pitman arm mounting point or arm drop. The result is the tie rod's arc will change.

Quote:
Originally Posted by emcee View Post
.....Also my definition of "bump steer" is when the steering wheel jerks left or right when going over a bump with one of the front wheels.
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Old 12-08-2021, 09:20 AM   #10
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The E450 chassis and larger class C units tend to have an issue with roll steer. The big box on the chassis has a tendency to roll from side to side. Every time it rolls to one side, you have to correct the steering as it causes a change in the front-end geometry. The results is a correction and a roll to the other side and another correction.

In my 31' Minnie Winnie, what finally fixed it was the following.
- Bilstein HD shocks on front and rear.
- air springs front and rear (now I would use Summo Springs).
- HD antiroll bars with urethane bushings, front and rear.
- Aired tires to maximum sidewall pressure.
- front end alignment with the RV loaded for normal travel.

With these corrections, the RV drove like a dream and no roll steer or bump steer.

The problem comes from the big box hung on the chassis. The Ford suspension is simply not adequate for weight. On the larger class C units, once loaded, you will be right at the chassis weight limit. For travel, we were 100# under the chassis rating with dry waste tanks and 1/4 tank of fresh water.

Ken
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Old 12-09-2021, 07:55 PM   #11
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I have done many of these adj bushing even of F series/4wd...

I Have alignment equip.

My 30 ft Minnie needs a bigger rack so the service shop let me put kits in..first, I paid his tech to finish alignment

IT IS NOT A DIY Job,, The single adjust will move camber and caster together..

The dual units will allow more range and more accurate range..

If you even moved or rotated the stock bushing,, you gonna make a mess of camber and toe.. both will move..

Change ball joints also if it has miles.. or if you have to beat out stock bushing.. beating it out will weaken ball joint possibly.. ask me why I know..
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Old 12-17-2021, 11:41 AM   #12
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Follow up

First I checked the toe in. 1/2"! yikes no wonder it tracks so good on the highway (and probably the reason why the tires are new).


Next I took off the passenger wheel and looked at the bushing installed there. It had this stamped on it:



XC25-AA 0.8 +.25


So apparently not a stock bushing. Since the toe, camber and caster have been adjusted already (so the alignment report provided by the PO wasn't the most current) I couldn't just add caster like I had planned. I put the wheel back on and ordered the bushing suggested by craigav (thanks!).


When the new bushings arrived I made an appointment with the alignment shop and decided I would replace the bushings myself and let the shop tweak them later.


It was really a simple job and took less than an hour an a half total to replace both bushings. The driver side looked stock (no discernible markings but the bushing appeared to have very little offset unlike the passenger side) and with the markings on the passenger side I set the new bushings to where I think it would only add 2 degrees caster.


It will be interesting to see the "before" numbers on the alignment report.


I'll post a final report after the alignment.
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