How to round out demountable 21" rims?

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Model T Ford Forum: Forum 2016: How to round out demountable 21" rims?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Saturday, June 18, 2016 - 07:36 pm:

I mounted new tires, tubes and flaps on freshly zinc plated old rims.



Today I tried to bolt the rims up to new rebuilt wheels but found the rims surprisingly out of round. I knew they were somewhat out of round but at least they would mount up to the old wheels. Maybe the metal felloes were bent too?

Unfortunately it didn't occur to me to have the rims checked and straightened before mounting the tires, but that's that way things worked out.

I am thinking of using the rim tool to push the rims into round. Has anyone tried this? Is it an efficient way to get the rims round again or maybe just an exercise in frustration?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Zibell, Huntsville, AL on Saturday, June 18, 2016 - 09:24 pm:

I think it may work, but would require removal of the tire first. Also I'd have the rim latched prior to beginning the straightening process. How do you plan to check roundness and identify where you need to push or pull? You will need some sort of gauge or fixture to use that is round with the correct diameter. Also not introducing a twist may be difficult to avoid using the rim tool.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Sunday, June 19, 2016 - 06:59 am:

I just figured setting the rim over the wheel would be good enough. If the four mounting tabs align with the four mounting bolts that would be much better than these rims have been for a long time.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chad Marchees _____Tax Capital, NY on Sunday, June 19, 2016 - 08:40 am:

Eric, maybe this idea would help?

Pic was sourced and saved long ago from MTFCA site:


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Sunday, June 19, 2016 - 09:03 am:

I would think that using the metal felloe from a junk wheel with the spokes removed and the wheel bolts in place would give you a good reference point to true up the wheels. If you lay the rim over that and then use the rim tool and C-clamps to move it around you should be able to get it close. I have split rim clinchers on my '10 Chalmers Detroit and the wheels were very much out of round. I was able to get them pretty close doing it that way but I also made shims to keep it that way since my wheels use wedges to keep the rim on the wheel.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Sunday, June 19, 2016 - 06:15 pm:

Great pic Chad. I see some wood working in my near future! :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Stolpestad on Sunday, June 19, 2016 - 10:32 pm:

I use a turnbuckle between the rim clamp (clip) to suck in the rim enough to remover the tires. I think I got a 12 incher to do the job. Can do a tire in about 10 minutes with this method


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, June 20, 2016 - 01:51 am:

For What it is worth. Model T 21 inch rims are fairly soft steel and bend easily. That is part of why so many are badly out of round. It also makes them easy to fix.
I get a large enough piece of cardboard (nothing critical about it). Draw (compass) a nearly perfect circle or two of appropriate sizes (inside and outside of rim), and use it by simply laying the rim (ends together, latched if needed) and eyeing straight down onto the drawn circles. This can actually work well for finding the high and low areas as well as twist.
For bending the rim back toward straight, I use simple leverage (usually with my trailer tongue, and sometimes a small block of wood in the valley of the rim). First, however, unlatch or unbolt the joint between the ends of the rim. Regardless of where the tweak is needed, the rim ends need to swing a bit to get a comfortable bend. Be careful to not over bend the rim. Just enough slowly to guide it back to straight.
Ideally, When done, both ends of the split should line up almost perfectly and just barely touch without being latched. However, a bit of lax side to side, a bit wide or a bit of pressure at the split, doesn't hurt anything. As long as the rim is straight and round when latched.
The hardest part of the whole process is to latch and unlatch the rim over and over again while checking, then bending, then checking again. Most rims will be bent in more than one direction and more than one place. I can usually straighten a rim in a lot less time than it takes to clean one for painting.
If you really want a challenge? Try this with some big non-Ford car or truck rims. They don't bend so easily.
Good luck Eric!
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Monday, June 20, 2016 - 10:35 am:

Wayne, when are you coming over to Spain? After getting the rims straightened out we'll have plenty of time for sightseeing, unless you feel like continuing playing with the T that is! :-)

I appreciate all the comments and tips. They're getting me motivated!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, June 20, 2016 - 04:42 pm:

I am afraid that world travel is not among my tea leaves. Too bad. I would love to see a lot of the world from the seat of a model T and other antique/veteran automobiles! I read lots of tour and meet reports from all around the world. There are some great meets not all that far from where you are. A few of our European regulars help to keep us informed of some of these meets/raleyes. I hope that you go to see them, and take your T soon!

I think you can manage straightening your rims. Just be a bit gentle with them, and take your time checking all directions. Many years ago, I first straightened some non-Ford rims (including a friend's '25 Lincoln). The first time I went to do a Ford 21 inch rim, I almost destroyed it on my first try. I thought maybe the rim was defective (too soft). I finished it anyway, and did the next. Also very soft. After a couple more I decided it wasn't a fluke and that was just the way they were made. Every Ford 21 inch rim I have ever straightened has been that way.
Good luck!


Top of pagePrevious messageNext messageBottom of page Link to this message  By paul griesse--Granville,Ohio on Monday, June 20, 2016 - 04:56 pm:

I`ve found that round tires will straighten the demountable rims pretty well...never really bothered to attempt straightening them before mounting---your rims look pretty good to me! Mount them and get them latched properly and I`d say you`re good to go...JMO Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Longbranch,WA on Monday, June 20, 2016 - 05:54 pm:

My bit of "safety" advice on split rims - mount the rim w/tire on the wheel BEFORE airing tire up to final full pressure !


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Alexander in Albion, Maine on Monday, June 20, 2016 - 06:35 pm:

I used Chad M's picture method for my 5 wheels. It worked very well


Top of pagePrevious messageNext messageBottom of page Link to this message  By Eric Sole - Castelldefels (Spain) on Tuesday, August 16, 2016 - 05:17 am:

I made the wood forms and am just now getting around to re-rounding the rims.

Bill, you say the wood forms with the jack worked well for you. Did you do the forming with the tire mounted on the rim?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, August 16, 2016 - 08:07 am:

I would not try to bend the rim with the tire on or with the latch locked - neither by pulling in any of the four mounting lugs. Wayne's method seems most reasonable. Most of the rims I've found had damaged locking mechanisms - seems there were many types, but all of them were weak and wouldn't take much bending strain. The next most common fault on loose 21" rims I've seen has been missing lugs, so they're also easy to pull loose. Some weld on the inside may help them stay in place - seems like they're only riveted /staked in place.
With a good anvil, maybe a large vice and some cold smithing you may get them round - if you keep checking them often against the cardboard circle :-)


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