Switching Argosy 20' MH to 16" rims?

[ViewRVs]

Any suggestions/advice on switching the P-30 chassis rims to 16"?

The 16" tires are less expensive and more readily available.

(The standard rim for the Argosy 20 is 16.5")

[idroba]

The people who have the GMC motorhomes built from '73 to '78 have an Alcoa wheel which they recommend to make that 16.5 to 16" conversion, but I have no idea if it will fit the P30 chassis of the Airstream.

I made the conversion on my own GMC motorhome and it worked well, but the details are fuzzy in my mind as it was sold maybe 10 years ago.

You might join the GMC motorhome forum and ask the question there, someone could tell you I am sure.

[martin300662]

I have the 16" rims on my 20ft (with the 8 x 6.5" bolt pattern), they were on it when I got it but appear to be a straight swap.

However I am considering going up to 17" as the 16" truck tires are getting harder to find (GMC switched to 17" with the same bolt pattern and used that size up to around 2004/5).

The 19.5" rims on my 28ft donor, also has the same bolt pattern so I plan to give them a try (at least see if they fit), my thinking being they will actual in crease the tire diameter by 20%, increasing the drive ratio.

[mayco]

Martin, those 8r19.5 tires are getting a bit hard to find in certain brands. Just a heads up. Especially when trying to get a set with date stamps under a year old.

[martin300662]

Understood mayco, and I wouldn't bother apart from the fact I have the rims to try.

I think the 17" are the way forward (because they were used for so long on so many trucks) but it means investing in a set of wheels and tires just to try, and I have been searching local Craigslist sites looking for a used set but so far nothing has come up.

[kidjedi]

So what did everybody do?

It's time to buy 6 tires, but it looks like the Firestone Transforce is the only option for 8.75R16.5. Should I be looking at changing my rims out as well (for easier tire replacement in the future)?

[bkahler]

Originally Posted by kidjedi

So what did everybody do?

It's time to buy 6 tires, but it looks like the Firestone Transforce is the only option for 8.75R16.5. Should I be looking at changing my rims out as well (for easier tire replacement in the future)?

Martin and I each bought a set of these aluminum wheels for our Argosies. If you go this route you will need two 16" steel dually wheels for the rear inner duallies.

16" aluminum front wheels

16" aluminum rear wheels

Like everything else the prices seem to have gone up but I didn't really take the time to look for the cheapest price before posting these links. There may be other sellers on Amazon that have these and you could also check eBay.


Brad

[kidjedi]

Thanks, Brad. Those are some good looking wheels.

I think I'm going to have to put them on "the list" for now though, as I don't have that kind of extra cash at the moment (curse this pandemic).

So to get to *safe* asap, I guess I'll do the Firestone Transforce at the original 16.5 size for now, and upgrade (downsize) when it becomes more possible.

Thanks again for the info and links!

[kidjedi]

Another question... other than the speedometer no longer being correct (not really an issue considering GPS will tell you your speed), has anyone switched to the larger wheels like the Airstream 310's and 345's? It doesn't seem like there would be any issue for the power plant (all the vehicles use the same Chevy 454) and they are also on the same P30 chassis (not sure how different the drivetrains are).

I realize there could be a million other reasons why it wouldn't work (especially in regard to the drivetrain and suspension), but I'm just curious, especially considering how much empty space is in the wheel wells (these Argosies look like giant twinkies on roller skate wheels).

[martin300662]

Originally Posted by kidjedi

Another question... other than the speedometer no longer being correct (not really an issue considering GPS will tell you your speed), has anyone switched to the larger wheels like the Airstream 310's and 345's? It doesn't seem like there would be any issue for the power plant (all the vehicles use the same Chevy 454) and they are also on the same P30 chassis (not sure how different the drivetrains are).

I realize there could be a million other reasons why it wouldn't work (especially in regard to the drivetrain and suspension), but I'm just curious, especially considering how much empty space is in the wheel wells (these Argosies look like giant twinkies on roller skate wheels).

It is not just the wheel size, there are a plethora of different stud patterns/even number of studs.

You can buy truck wheels with the same stud pattern in 17 and 19in dia, but you will not be able to use LT tires (only low profile car tires) as the 'space' is not in terms of dia, but because they are too far 'in board' (ie the track is too narrow for the width of the body).

JB8 (disc/drum) brake options use the 16.5 (16in) wheels (even the much newer 250)

JB9 (disc/disc) use the larger wheels to give clearance for the calipers at the rear.

Even LT235/85R16 tires rubbed the frame on Bella and I had to swap to LT225/85R16 to allow them to turn freely.

[GWallace]

I have been through this conversion on two 1977 Argosy Motorhomes in recent years.

1. I first considered replacing my tires with new 16.5 tires. Over the years I discovered that even though I could order 16.5” tires, they may have been stored in a warehouse somewhere and already be several years old. Calendar age is a problem with these motorhome tires as they age even with lots of tread, the summer heat can cause blow outs with old tires. Away from major metropolitan areas 16.5 tires are often not available. Several years ago, I experienced a tire loss and was not able to replace it until returning home. Since the P30 chassis was shipped from Chevrolet in the 1980’s with 16” wheels, I decided that 16.5” were out and I would change to 16”.
2. At first I considered all new 16” steel wheels and uncovered the next problem. The 16.5” wheels are rated to carry a maximum of 2750lbs and the 16” wheels are rated at 2450 lbs. The problem is the 1977 Argosy loading on the front axle is 5000 lbs. putting the max load just over the 16” wheel max. With this I decided to go with aluminum wheels that have a higher load rating.
3. Therefore in 2015 with my 1977 20, I purchased four 16” ALCOA aluminum wheels and three 16” steel wheels to convert my Argosy 20. The seventh wheel is the spare mounted on the rear spare tire carrier. The seven tires are Michelin LT225/75R16 and these tires have the same outside diameter as the original 8.75/16.5 tires. The speedometer is right on the money as checked against a GPS unit. This keeps the speedometer and odometer accurate.
4. This past winter I went through this same conversion on my mom’s 1977 Argosy 24 with 8.75/16.5 tires. I discovered that ALCOA no longer makes the Chevy wheel in aluminum and the only ones available were the ION wheels that Brad listed above. I purchased some from Summit Racing. The front ION wheel is different from the rear ION wheel, so a set is 2 front and 2 rear wheels. I also purchased three 16” steel wheels. The inside rear wheels must be only steel wheels not aluminum. (See 6. Below)
5. With these wheels the conversion works just fine. Here in the Southwest US, the 16” tires are generally available and the weight margins along with physical clearance dimensions work out well. The profile of the LT225/75R16 tires is such that the dual tires in the rear don’t touch each other and clear the wheel well without issues. On my Argosy 20, I have been happy with the conversion and have not had any problems.
6. The last point is these hubs and wheels are “hub” centric rather than “lug” centric wheels. Hub centric means that the weight of the vehicle is carried on the hub instead of the lugs. The controlled dimension of the rear hub diameter is such that an aluminum wheel on the rear inside “pushes” the rear outer wheel to where the weight of the outer wheel is not fully carried on the hub. Hence the rear inner wheel must be a “thinner” steel wheel.

By the way I'm not an expert, but this is just my experience.
Good Luck!
Gregg

[kidjedi]

Martin:
Thanks for the "width of vehicle, not diameter inside wheel well" explanation.

Regarding JB8 vs. JB9 disc and drums brakes. I thought I had read about people converting to disc brakes in the rear (maybe I'm just imagining that?). Does this then involve changing the wheel size? If so, how does that work with the 16" vs 19" conundrum (being able to use a 19" wheel for rear disc brakes)?

Gregg:
Wow. That is some good information (and a lot of it). Hopefully it will help not only me, but many others that find this thread in the future.

Your "point one" is something that I had become aware of, and I definitely plan on checking the "date stamp" before making a purchase. I have also heard/read that Firestone doesn't hold anything in stock that has a date older than six months, but I wonder if that holds true for the Transforce 16.5" tires (since they are used much less frequently). It's definitely something that I had planned on asking specifically at my local Firestone before ordering (can I be sure the tires I receive will be "fresh").

Unfortunately the rubber alone will be $900 (not including mounting and all the other extras). Adding a new set of wheels (unless I get lucky on Craigslist or a junk yard) will be around $1,100 additional dollars, and unfortunately I just can't swing that right now, so hopefully I can find "fresh" 16.5" tires and then make the wheel/tire upgrade a little further down the road.

Another (and maybe stupid) question, but what happens if you put 16" wheels/tires on the front and leave the 16.5's in the rear? It sounds like the Michelins Gregg is using have the exact same outside diameter, so is it effectively like running all 16.5's? I'm wondering about upgrading the front now and doing the rear a little later. Obviously I wouldn't be able to rotate the front and back with this situation, but it sounds like these tires need to be replaced because of age long before the tread becomes an issue, so maybe rotation is not something to worry as much about?

While I am at it... I would like to post the exact wheel/lug pattern for our Argosies for those who come looking in the future. Am I correct in stating that the wheel needs to be 16"x6" with 8 lugs at 165.1mm? The other measurement that should be posted is the inner/outer offset for the front, rear outside, and rear inside.

Finally, if I try to find a used set of Alcoa's (since I'll be biding my time), what similar vehicle am I searching for (what vehicle do our wheels match)? For instance, I see these Chevy duallies on eBay, but I assume the inner/outer offset is an issue. So what vehicle (dually truck or van) can I put in on a wheel site to find the correct wheels for our Argosies?

It's unbelievable how much information has to go into the search for simply getting new tires! This has (by far) been the most difficult thing to figure out on the Argosy. Everything else has been straightforward and relatively simple.

Thanks to all!

p.s. There were quite a few people giving a lot of love to Centramatic balancers for their 310's and 345's with the 19.5" wheels. Is anyone in the Argosy clan using them on their 16" wheels?

[martin300662]

Unfortunately you are trying to generalize a subject that cannot be generalized, at least for the Argosy, because they were parts bin specials.

For example in 1976 some motorhomes came with 8 stud 6.5in PCD using 9/16" bolts, others came with 10 stud rear wheels/5 stud fronts 5/8" bolts. The simple guide is "go look in the owners manual".

Another example is the 'rear disc' conversion, yes folks have done it but it isn't a case of installing the JB9 parts, it uses an aftermarket kit (El Dorado discs/calipers, weld on caliper bracket, new combination valve (to give the correct brake bias)) however in general this gives better braking but a longer travel on the brake pedal - one of the weak points of the Argosy already.

As for Centramatics - yes, and unlike the larger wheels they are standard part numbers/always available.

[CapriRacer]

In case anyone finds this thread and is puzzling over the conversion, I did a webpage on converting from 16.5" tires to 16" tires:

http://barrystiretech.com/165tires.html

[kidjedi]

Originally Posted by martin300662

Unfortunately you are trying to generalize a subject that cannot be generalized, at least for the Argosy, because they were parts bin specials.

For example in 1976 some motorhomes came with 8 stud 6.5in PCD using 9/16" bolts, others came with 10 stud rear wheels/5 stud fronts 5/8" bolts.

But the measurements for the 16.5" 8 stud wheel will at least be the same for all Argosy 8 stud wheels, won't it? So why not make that information easier to find by posting it here? If someone has 10 stud wheels, their wheels are different and will have different measurements (which would also be nice to have posted here, so the information is in the same location when people are searching for it in the future).

Originally Posted by martin300662

The simple guide is "go look in the owners manual".

The manual states only that I should use an 8.75-16.5 tire and that the lugs are 9/16" and there are 8 of them. The manual doesn't give me any indication whatsoever of the inside/outside (tracking) offset of the wheel so that I can go buy replacements. There is no information that I can find in the owners manual that would let me know what wheels are acceptable replacements for the wheels that came with the vehicle.

Originally Posted by martin300662

As for Centramatics - yes, and unlike the larger wheels they are standard part numbers/always available.

I assume by that you mean as long as I order the Centramatics for 16.5" 8 stud with 6.5 (165.1mm) spacing, it will fit the wheel correctly. Same would go for a 16" wheel, as long as I select the correct bolt pattern.

As always, thanks for the information and clarification. I just want to get it right the first time!

[bkahler]

Originally Posted by kidjedi

But the measurements for the 16.5" 8 stud wheel will at least be the same for all Argosy 8 stud wheels, won't it?

Yes, the 16 and 16.5 wheel pattern is the same.

The manual states only that I should use an 8.75-16.5 tire and that the lugs are 9/16" and there are 8 of them. The manual doesn't give me any indication whatsoever of the inside/outside (tracking) offset of the wheel so that I can go buy replacements. There is no information that I can find in the owners manual that would let me know what wheels are acceptable replacements for the wheels that came with the vehicle.

As far as I know it is just the diameter change.

I would verify with Peter to certain but I believe the same Centramatic is used for either wheel size. However the front and back Centramatics are not the same.

[kidjedi]

Still looking, but wanted to post that for the ION wheels that Brad posted and Brad, Martin, and Gregg's mom are using, the offset on the front wheels is 102mm and the offset on the rear outside wheels is -125mm. So if someone is trying to replace their 16.5" wheels with 16's, these are the offset numbers you will need when searching.

[kidjedi]

Also, the "search by vehicle" that seems to work for me is Chevy Silverado 3500 dually or GMC Sierra 3500 dually from 2001-2010 (that seems to give the correct bolt pattern and offset). I am also finding some 17" options with the correct offset, so wondering if a 17" wheel is worth trying.

In addition to the previously mentioned IONs, the most common wheels are Vision 181, American Racing Baja dually, Ultra 002 Modular Dually, and Rockstar XD775.

And for the record, even though these would fit, even if I had $1,000 to spend on EACH WHEEL, I would never, ever, ever install these hideous monsters...


edit: MotoMetal MO963 may also work (17")?

[martin300662]

Originally Posted by kidjedi

Also, the "search by vehicle" that seems to work for me is Chevy Silverado 3500 dually or GMC Sierra 3500 dually from 2001-2010 (that seems to give the correct bolt pattern and offset). I am also finding some 17" options with the correct offset, so wondering if a 17" wheel is worth trying.

In addition to the previously mentioned IONs, the most common wheels are Vision 181, American Racing Baja dually, Ultra 002 Modular Dually, and Rockstar XD775.

And for the record, even though these would fit, even if I had $1,000 to spend on EACH WHEEL, I would never, ever, ever install these hideous monsters...


edit: MotoMetal MO963 may also work (17")?

17" wheels may fit as long as you don't install any tires, or if you can find light truck tires with less than 45% profile, as even 85% tires on 16" wheels foul the wheel wells.

The wheels are only part of the equation there is also a maximum diameter (wheel and tire) and width (to stop the duallies 'kissing').

[Boom Sounds]

You can certainly pick up the tyres relatively easily and cheaply. Hankook and Nokian readily available at decent prices. Michelin are available, but costly. I run Michelin/Hankook on the fronts and Nexen Rodian on the rears.

https://www.tyres-outlet.co.uk/produ...5-r16/r-137233

In my opinion 235/85 R16s are just too wide for the rears. Weirdly, the chassis manual does seem to permit these but I can testify to the fact there is not enough clearance on the dualies....which is why I moved to the narrower wheel.

The stock is 7.50 R16s which are available and I might switch back. They give you a higher ride height than the 235/85 R16s and avoid any kissing on the rears. You would need to separate out the tubeless ones. https://www.bigtyres.co.uk/7-50r16-k...-121-120m.html