Can I change from 17.5" wheels/rims to 16"?

[olhillbilly31]

Sent: 5/21/2008

Ok i just got a 1979 Southwind. I know its not a Winnie, but i haven't found one yet. but i can now go camping..lol..
Ok my question is this.  I have 17.5 rims and tires on my 26 or 27 foot MH. Can i change them out to 16's or since it weighs 12,000 empty is it to heavy for 16's.

Trying to make it so if i blow a tire in the middle of no where i can find another tire with out to much trouble..

I will have more questions as i go about the dodge part of it, and i knew that you guys are the dodge guru's..   Other than the tires on it being weather checked bad, there is nothing really wrong with the coach. Well other than the valve cover gaskets leaking bad, and the right exhaust donut gasket being blown out.  Everything else works perfect.

billy

[denisondc]

Sent: 5/21/2008
        12:35 PM
If the 16" rims will fit over the brake calipers in front and over the brake drums in the rear, the issue would be whether there tires available that had at least the same 'maximum load' as was stamped on the sidewalls of your 17.5's. If it was designed for 17.5's, then the brake parts might not allow the smaller diameter wheels to fit. And you dont want the wheels to be so close to the calipers that they would rub on corners or during hard stopping, when the wheel may distort slightly.
I would kind of think that a 16" Light Truck tire that had a high enough load range to replace a 17.5, might be just as hard to find on-the-shelf in tire stores.
Since my tires 7.50-17 load range D are something that has to be ordered in (no one stocks them anymore), I used to carry two spare tires. Now I carry one spare, plus an extra un-mounted tire.

[4winds]

Sent: 5/21/2008

Have the same problem on my '78 Itasca and found a set of 16" wheels. They fit the back but will not clear the calipers on the front. So back to the drawing board!! Ed

[henryblair]

Sent: 5/21/2008

How many lugs do you have?

Henry

[olhillbilly31]

Sent: 5/21/2008

they are a 8 lug wheel, i figure since its a dodge chassis a 1 ton rim might fit. i know about making sure they clear the brakes...i can get 10 ply in 16 inch tires. i might round up a rim from a friend and see if they work.. not sure yet..tires are 182.00 to 199.00 where i live so getting the on-line doesn't save any money...
billy

[The_Handier_Man1]

Sent: 5/21/2008

If I had to change wheels I would go to the 19.5" wheels.  Now if I could find the right UPS truck setting around, they could just deliver the wheels to me and forget the package's, lol.  The larger wheels would give me lower RPM's on the highway,  Les

[Slantsixness]

Sent: 5/21/2008

If you can find a set cheap, any 8 lug Ford or Dodge dually offset rim will work. Due to the age of your rig, you have disc brakes. since it's an RM350, yes... your brakes are exactly like a 1 ton pickup truck... soy they will fit and clear the calipers and rotors.

I have Denman 17.5 bias ply tires, they're now 4 years old, not checked at all. But I paid $89 a piece and $10 each for mounting and balancing. At the time, I thought the $135 Yokos were highway robbery... but I wish I had gone with radials, for the ride, not the handling. Mine handles very nicely with the bias ply, but the "feel" of the bias ply's working the flat spots out is annoying for the first 5-15 miles.

Try Denman. Decent tires (made in Mexico...but they've held up pretty well). But if it's radials and the radial ride you want, change the rims to 16's... or fork out the cash for the radials.. (you did check yokohama at Tire Rack for pricing, didn't you?)

[olhillbilly31]

Sent: 5/22/2008

for some reason these on-line tire places are kicking my butt..i will keep trying to figure it out. may have to have the ol lady figure it out.. i know i will have to take it in and have the speedo recalibrate to work with the tires, but one tire shop here in town said that if i got the right size 16's they would be real close to the same size as the 17.5's. i will have to think on it.  to bad chevy rims wouldn't fit, i would pull the aluminum rims off my dually and put them on the MH..
billy

[Slantsixness]

Sent: 5/22/2008

http://www.tirerack.com/tires/Compare1.jsp?width=8&ratio=0&diameter=17.5&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All&x=59&y=5

There you go. Wish they were cheaper.

there are dozens of threads about the 17.5" tires here. use the message search to find them.

At the moment, Tire rack is out of the Y785's, but if you calll them, they'll tell you just how soon they can have them.

Tire diameter sizes do not differ between the 16.5, 17.5 and 16" wheels, so your speedo will still be accurate as it ever (never) was.
the 8.00R 16, 8.00R17.5 and 8.00R16.5 are all the same size outer diameter, which is what your speedo "sees"

Tom

[olhillbilly31]

Sent: 5/22/2008 9:37 AM

thank you very much...was hoping to get tires this week, but since it is raining for the last 2 days, might have to wait until next week... man i got the bug to go camping bad.. lol....thanks again..
billy

[olhillbilly31]

Sent: 5/24/2008

ok found tires in salt lake city at some place that sells new and used tire. new ones are 148.00
includes mounting and balancing, free rotation and free flat repair.. i don't think i can buy any and get them shipped and then mounted for that.. they are 10 ply so should stand up to the pig out front... so one problem down, who knows how many more to go..lol
billy

[The_Handier_Man1]

OK I have found new 16" 8 Lug wheels with LT235/85R-16 tires (1/4" taller than my 8X17.5 tires) for my '73 Indian with disk brakes.  One tire guy said I will notice the way it handles, like you could say our Classics "Handle".  Now I don't want to step on anyones toes, but if you have changed from 17.5's to 16's do you notice any difference in the way it drives?

[JDxeper]

I switched my 78 M-300 to 16", the biggest difference was a combination of things, steering adjustment, new shocks, new balanced tires.  It drives a lot better but how much going to 16" from the 17.5 made.  Don't know!
Dave Dension summed up things well, if they fit over the brakes front and rear, they will work.

[salplmb]

hey les,
i have a 73 indian just like yours with the disk brakes up front. i got some 16in rims off my dodge truck same lugs and everthing. the problem i have is that the rims are just barely too small. they end up hitting the calipers on the inside.
i have been wanting to do this swap for a long time but just haven't been able to figure it out. i posted about using some spacers to move the wheel out just a bit but got no responce and am not sure with the coining of the rims if this solution would work.
hope to hear if you come up with a solution or if the rims you have found are a little different. if that's the case please post the what kind of rim and what you got them off of cause i'm sure allot of us would love to get away from these old size tire limitations.
hope this helps a little and thanks.
sal

[Slantsixness]

Alrighty then....
(This corrects a statement I made years ago, above about the 1 ton brakes)
I'll give you a quick rundown on why you could, and why you can't.
If you browse through the older posts, some more details are around.. but here's the Jist:

First off.... Tire diameter size is no biggie. They make 16" tires with the same outer diameter and load rating. Plus.... the speedometer gear in the transmission is interchangeable in all year (from say 1956 to 1993 powerflite,loadflite,torqueflight mopar Rear wheel drive)  transmissions, The "speedo gear" is available in many different sizes.. some are hard to find, but available nonetheless.

So... you calipers hit your 16" rims? there's an answer for that...
You might have an RM350 or 375.... what's the catch? D300/350 16" dually rims have a smaller offset. All FORD rims have the smaller offset, and no "coins" to boot.
Almost any donor RM350/375 with 16" rims will fit ANY M300-RM350/375 From 1972 (chassis) year and up. 1967-1971 models can use Ford or any Bendix 8 lug offset (dually) Rims: they were not coined. You CAN use non coined rims on a coined Dodge truck, but please keep in mind that you only have 4 lugs on each rim that will meet the weight and load capacity. the un-coined 4 lugs with washers is dangerous.
Since the brakes are Bendix, you CAN change out the Front and rear hubs and use non coined hubs from a later year Ford chassis, but there again you will run into the calipers rubbing the wheels... (and you could use the ford calipers and the entire brakes...then the 16" rims would clear, HOWEVER...the brakes are lighter duty, so you're back to the weight/load problem again... (it would still stop though)


so unless you have a lot of cash to fork out (who does?!) You simply have rims that are incompatible, although they will fit the rear axles without issue, except for the coins and alignment pins (if the pins are still there!)

You can tell a Ford rim typically by the black plate mounted on the lug face. These are bad news on motorhomes.. they don't fit, and the original dodge lugs are too short, and a larger diameter too...so don't drill them out, return them.

Some Dodge Rims (d350) have a recess ledge just behind the lug hub. this makes them SHORTER and is why they rub the calipers. The rims you want do not have this "ledge" near the hub...

Ok...so maybe that confused you all... maybe it cleared it up a bit...
I guess the answer is "yes" you can... but only with the RIGHT 16" rims.

hope this helped.

[JDxeper]

The data I used is from tire rack, the section width for the 8r17.5 is 8.1 inches, revs per mile 668, tread width 5.4 inches, overall diam 31.3 inches.

235/85r16 sect width 9.3 in, revs per mile 659, tread width na, overall diameter 31.7 inches.  My calipers cleared the rims after bolted up tight.  Others have had the same problem with the calipers not clearing.  Again my is a 1978 m-300 dodge chassis.

[JDxeper]

BTW ,  I went through a number of used rims over 15 before finding a few that were straight enough to use. I had one rim which I bolted on to check clearance before going forward.  As Slantsixnes indicates besure of the the change before going forward.  New coined rims 8 lug 16 inch rims are available but the brakes are the problem.  Good luck.

Les, the foot print is a little wider for the 235/85 16's but not a problem for the duals. That should add just a little more control but who know's.

[The_Handier_Man1]

OK here is the update.  I let Les Schwab (no relation to me), put new 16" wheels on.  I guess they held one up to the front and thought they would fit.  So they mounted up the tires starting on the rear,  you might guess where this is going, and guess what.  The calipers hit the wheels on the front.  They did measure my old wheels first to get the right offset and tried both different offset wheels only to almost get one to fit.  But if I ever changed the brake pads they would not clear.  Now I think, yes I do that sometimes,  I have dual piston calipers.  Maybe the single piston ones would clear.  Any thoughts from someone who might know about this???  Les

[JDxeper]

About 1/2 in clearance on new 16s compared to about 21/2 on old 17.5.  I believe my brakes are single piston, but don't know for sure.had looked at them to check pads and clean rails.
  I got interested after I saw another 78 with 16".  His came off an ambulance!!

[The_Handier_Man1]

Yup JD, you have the single piston calipers.  I have a RM350 chassis.  What can I do??

[JDxeper]

Sorry I can't help much, my parts/service book show the same caliper for all the 1978 and 1979 M series 3-4-5-6 the same, but different hubs.  Dodge probably put different calipers on the heavier frames. LOL I don't know , I'm over my head already.

[DaveVA78Chieftain]

RM-300 (M-300) uses a Chrysler sliding caliper with a 3.1" diameter single piston (Dodge P/N 4032824 [RF] / 4032825 [LF]).

RM-350 (M-400)/RM-400 (M-500) Uses a Kelsey-Hayes sliding caliper with a dual 2.38" diameter pistons (Dodge P/N 3732926 [RF] / 3732927 [LF]).

Dave

[The_Handier_Man1]

Well it looks like those of us with the dual piston calipers need to get use to the 17.5 wheels and tires.  I was told that on some rigs with calipers that rub just a little, you can grind off a small area on the caliper.  Probably not a dual piston caliper.  I did try a 16.5 wheel just for fun and that would not work either.  Nothing I found works and I'm not out any money checking it out.  There are 215/75R17.5 very heavy duty (16 ply) that are used on lowboy trailers but I was told those do not fit our wheels the best.  Something about the bead being too thick. I would like to hear from someone using 215/75R17.5.

[audioguyinMI]

I successfully changed over 16" Ford Dually rims and they work very well.

'75 D23 Indian on a '74 RM350/M400 chassis.

Indeed, depending on your particular set of calipers, they will rub the inside of the front wheels.  A few minutes with a die grinder takes care of that problem. 

You always run the risk that putting the spare on will cause a problem, as we are talking about very minute casting differences that cause them to rub in the first place.  But clearance is clearance, and once they don't rub anymore, they don't rub anymore.  Been on a couple years and much improved ride due to the availability of heavy duty radials.

Best,
Bill

[yellowrecve]

I'm using 16" off a 1992 dodge dually with 215-85 tires on the rear of my 74. These tires are close to the overall diameter of the 17.5.  The front do touch the brake calipers. I was told to grind the corner off the caliper, but I'm not sure I want to take that much off. Brake wear may have a bearing on how much needs to be removed. I had a machine shop cut the center out of a 17.5 with the idea of using it as a spacer on the front, to clear the caliper. My front 17.5 are only 3 years old, so have not done any changes there. I carry the spacers to use if the need arises.