17.5 to 19.5 wheel swap on M400 is it doable?

[basicfish]

have a 1975 Sportscoach a 25 ft rear bath, on a Dodge M400, (I think) chassis. It has the dual piston front calipers and Hydro Vac boosters, 2 of them mounted to the frame. it has the 17.5 eight lug wheels.
My Question is has any one swapped to a 19.5 wheel or maybe added spacers or a centric adapter to the hub so a different wheel size can be mounted.
If I could figure out the doner RV I would change the Hubs ( or even both axles) out to the GM ones to solve the tire issue.

If you have done this I could use some help, it is a neat old solid RV I would like to keep it on the road.

Thanks

[cosmic]

On my 75 Brave. it came with 17.5 R8 and it was a option to get 19.5's so I cant see why they would not bolt right on and away you go.

[joev]

are your 19.5 eight bolt  if they are shouldn't be a problem  i just bought new 17.5 for my winnie paid $205 each for my tires  thery are double coin 8R17.5s so for 7 tires installed balanced and tire eviromental fee was about $1700 

[dirtfan85]

Ok What is a coined wheel?

[LJ-TJ]

In stead of being flat. They are coined so the dualys will line up.

[JDxeper]

Your rims on the Winnebago are lug centric, that is centered by the lug type and pattern.  Some rims are hub centric, that is the center of the hub lines up the wheel to the hub.  Now that probably really adds to the confusion!
The hub on the Winnebago is designed to accept the alternating lug pattern of the rims. No wobble.
Also search cone or coined rims for more in formation.

[DaveVA78Chieftain]

Dodge 17.5" rims are 8 bolt
Dodge 19.5" rims are 5 bolt
Would require converting both front and rear axles to a M500 configuration.

Dave

[LJ-TJ]

Hey Dave, I was wondering. I had 17.5 tires on mine originally and dropped down to 16's for ease of getting tires and to have them changed out if something happened on the road and to get away from split rims. She runs just fine but seems to rev higher than I would like not a big deal but if I could I'd like to drop the rev's down a bit at highway speed and maybe pick up a mile or two one the fuel mileage. So I was thinking of going to a 19.5 wheel. In my owners manual it say that there was a 19.5 option. What do you thing? i?? Here's a trick question. Is there such a thing as a 17.5 tire with the same circumference as the 19.5 tire.

[DaveVA78Chieftain]

Far as I know the 19.5" option would have been moving up to a M500 chassis.  Dodge service manual does not show a 19.5" rim for a M300 or M400 chassis.  So it becomes an issue of locating a 19.5", 8 bolt (6.5" circle dia.), rim with the proper 5.25" width and offset.   Then you would have to see if you can select tires (http://www.ricksontruckwheels.com/tires-195-truck.php) with a diameter close to the original 17.5" tires.  Do not forget load rating also.

Dave

[Reid]

Howdy,

  I too have a D21 M300 but a 73 Brave.  I just bought 16" Ford Rims from a Salvage Yard Today.  It looked like the Hub 4 7/8 Inches and lug hole spacing 6.5 Inches will line up.   I am hoping they will work on my Coach.  Did you have any Problems with your Change to the 16" Rims?  I don't think these Rims I bought are "Coined" only flat I wonder if this will be an issue with the Rears running true?   I thank you for your input.

Reid
Tucson, AZ

[Chief Crazy Canoe]

Dodge 17.5" rims are 8 bolt
Dodge 19.5" rims are 5 bolt
Would require converting both front and rear axles to a M500 configuration.

Dave-

On my 72 Chieftain (still thinking its an M375 )-a data tag shows M400 though.....it came the 5-lug 17" split Budd wheels originally & 7.50X17 That was around a 31" tire.  Stepping up to a 19.5 would be an 8R19.5 and end up around 34" in tire diameter.  Thats a large increase in tire height.  Will tha even physically fit under the wheel wells?  - the increased diameter will definitely result in a power loss up hills.

Is it worth it in the end?

[DaveVA78Chieftain]

If it has  5-lug 17" split Budd wheels then it is a M375, period, end of that discussion. The M375 was the last one to use them.  Original tires were Bias Ply. I have no clue if the clearance is there though you are talking about changing out the complete front and rear axle assemblies most likely with springs.  Will the spring perches line up?  I have no clue.  I never dug into the tire swap out subject myself.  I can still get 8R17.5 tires so that's what I did over the last few years.  Coker tire still lists 7.5 x 17 Bias Ply tires (Military/Truck Section) which may be your only choice short of installing a complete new suspension from a 74 or later M400 doner RV.   I do not know if that would work.

Note: Dodge used the RM350 designation for 73/74.  They renamed that to M400 in 75 saying it also applied to the 73/74 RM350 also.  The M4 designation in parts book used in 72/73 applies to M375 not M400 (RM350) so don't get confused.
Additionally they used the RM400 designation for 73/74. They renamed that to M500 in 75 saying it also applied to the 73/74 RM400.
Makes things real confusing in 73-75.

Dave

[khantroll]

I looked at doing the same thing, and I came to the conclusion that it would limit my turning radius, as well as requiring a two inch lift for a safe ride. If you can find a local tire shop or speed shop that deals in Coker Vintage tires, they make two or three reasonably priced tires that will fit the stock rims. Farmers' Co-Ops and tractor shops will be glad to mount your tires on the rims (if that's a problem where you live, as it is for me). Several other members have had great luck with Les Schwab tire centers. I'm chasing down parts to swap to 8 lugs myself. While I love being the look of the stock rims, practicality is more important to me at this junction then appearance or correctness.

[Jonbbrew]

If it has  5-lug 17" split Budd wheels then it is a M375, period, end of that discussion. The M375 was the last one to use them.  Original tires were Bias Ply. I have no clue if the clearance is there though you are talking about changing out the complete front and rear axle assemblies most likely with springs.  Will the spring perches line up?  I have no clue.  I never dug into the tire swap out subject myself.  I can still get 8R17.5 tires so that's what I did over the last few years.  Coker tire still lists 7.5 x 17 Bias Ply tires (Military/Truck Section) which may be your only choice short of installing a complete new suspension from a 74 or later M400 doner RV.   I do not know if that would work.

Note: Dodge used the RM350 designation for 73/74.  They renamed that to M400 in 75 saying it also applied to the 73/74 RM350 also.  The M4 designation in parts book used in 72/73 applies to M375 not M400 (RM350) so don't get confused.
Additionally they used the RM400 designation for 73/74. They renamed that to M500 in 75 saying it also applied to the 73/74 RM400.
Makes things real confusing in 73-75.

Dave

Well this could explain my issue. As i get ready for solving my brake dilemma i looked closer at my wheels/tires. The PO told me he swapped out all the split rims. Good thing right? Well, now i see he is running 19.5 tires. In looking closer i noticed that on one side there is a small rub mark showing on the sidewall. This would make sense if the rig was supposed to have 17 or 17.5 right? So how do i fix it besides go replace all the wheels and tires? Lift? Airbags? My springs appear to still be smiling so that that is good. How do i get rid of the rub? i am sure it could use new shocks but that wont help the rub much especially if its 1-1 1/2 inches closer that is should be.


Thoughts?

[Rickf1985]

What is it rubbing on? Front or back?

[Jonbbrew]

What is it rubbing on? Front or back?

Back. Outside dually.

[DaveVA78Chieftain]

I assume the 19.5" tires are also radial tires.  You do not want to go back to 17" split rims.  Only solution I can think of is a smaller width radial.

The following is a NO NO


You want it to be more like this:

[Jonbbrew]

Inside tire to tire rub is not the issue for me. Its my outside rub to the coach wheel well. I will post picture of the tire and wheel size along with the rub space on one side but not the other. Maybe a lift or ?


Maybe a way to move the well out farther but shifting the shield? dunno..puzzled.

[M & J]

Is it possible to trim the wheel well lip? The interference seems very small.

[Jonbbrew]

Is it possible to trim the wheel well lip? The interference seems very small.

Maybe...considering air bags as well. Still just not sure what to do or which kit to consider.

[Rickf1985]

Looking at where the rim is in relation to the body in your pictures it is obvious that the whole setup is farther out than original. The rim itself appears to be outside of the body side. I think trimming the wheel well is going to be the only option since even skinnier tires will still be inline with the rim.

Dave, in those pictures, on the top picture, look between the tires. What is that where there should be a wheel like in the bottom picture?

[DaveVA78Chieftain]

Not sure Rick.  Maybe a spacer?  Just a couple of pics I found on the net to demonstrate what can happen if incorrect rims and tires are used.

[Froggy1936]

Seeing it mentioned again here (I thought previous explanation had killed it but I guess not) THERE IS NO SUCH THING AS A COINED WHEEL !  A long time ago a misprint in a Dodge Factory service manual created this misinformation The proper description is CONED ! But the misprint added the I Common sense just look at the bevel @ the hole it is coned !   N:( Frank

[Jonbbrew]

Not sure Rick.  Maybe a spacer?  Just a couple of pics I found on the net to demonstrate what can happen if incorrect rims and tires are used.

Air bags would help? I will also look into seeing if I can move the well as well.

[Rickf1985]

If you use air bags to prevent suspension movement it will be a rough ride, and hard on equipment.