Standard bike, 16” rear fit?

I’ve seen plenty of parts swapping mod threads and pics but can’t find any examples of anybody putting a 16” Special rear wheel on a Standard frame custom.
With a “very accurate” tape measure comparing distances on both examples of frames it is clear that there is over an inch difference in features such as;
Swingarm pivot to top shock mount.
Swingarm pivot to top frame rail.
Although a 16” rear sounds like a meaty , hot rod tire to look at, it may be that even with very long shocks the frame geometry is just a no go .
Any body seen it done ?
Thx, -RT

I think Leo may have done this on his '75 model. What you may need to do is fit the Special brake torque arm because it's dished out for tire clearance .....

Okay well that’s easy enough.
I’m just thinking that the rear end seat and fender would squat a noticeable bit. And even worse, affect handling drastically.
If not so much , we’ll it would look great lol !
Not ruling it out yet

Still measuring and thinking ..
not ever much progress here as the neighbors stop by for peanuts and everything lol.
Just rode this very powerful electric mountain bike of a neighbors.
Interesting spring loaded adjustable seat adjusts on the fly with a left lever to accommodate “mode” of riding.

That`s a nice looking squirrel. Do you feed him on a regular basis?
I wish I could have found one of those 16" alloy rims before I changed My mono shock build over to disc.

halfmile said:

That`s a nice looking squirrel. Do you feed him on a regular basis?
I wish I could have found one of those 16" alloy rims before I changed My mono shock build over to disc.

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Yes, we feed all the squirrels around here. They’ll just come in the garage and help themselves sometimes.
Stumbling on this fine 79 16” x 2.75” Aluminum rim has me wishing it is tall enough to work. I have new shocks but they are only 13.25 eye to eye.
A 130/90-16 is kinda tough looking.
I realize it would affect the nimble feel of the tall 18” rear but hey, I’m not all about performance anymore.
But yet still realistic..,

If you are talking about alloy wheels if you can find a 1980 or 81 can't remember the exact year, yamaha made an alloy wheel with drum brake that will go straight in, or the heritage wheels are drum brake so will fit

79 SPII has the 16" 2.50 Alloy drum rear.
The OD of a 130/90/16 tire is within 1/4"? of the 110/90/18 so other than width there shouldn't be any major issues installing the 16.
Like 5 twins sez the brake stay, And I think the special chain guards have a slight "dent" to clear the tire.
The special frame's shock mount is further forward but also lower on the frame so shock length is very close if not identical.

gggGary said:

79 SPII has the 16" 2.50 Alloy drum rear.
The OD of a 130/90/16 tire is within 1/4"? of the 110/90/18

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gggGary said:

Like 5 twins sez the brake stay, And I think the special chain guards have a slight "dent" to clear the tire.

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gggGary said:

The special frame's shock mount is further forward but also lower on the frame so shock length is very close if not identical.

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Gary, this is all good news.
A 79 “SII” 16” Aluminum rear rim is actually 2.75” wide. It weighs in at more than a pound lighter than my 78E Standard 18” rim.
Using “Dennis Kirk” tire website. My only source to determine tire diameters, and those site stats do vary, ? I was convinced the overall dia of a 130/90-16 was more than an inch smaller than a 110/90-18 tire.
If these two sizes come out to be only say .25” then there is not much stopping this modification idea.
I have a Special chain guard already on there.
I could use some tire diameter “proof” comparisons anybody ?
Still thinking Continental Go’s
Thank you- Randy

On my 75 I did swap in a 16 disc brake alloy wheel. I did it to get the disc rear brake. It not a swap I would recommend. A lot of work. It did slightly improve the brakes.
It does effect handling. The wider tire does slow turn in when cornering. The difference isn't that much for street riding. Racing it could make a more noticeable difference.
On ride height it doesn't make much difference.
To calculate a tires overall height you need to understand what the tires size on the sidewall means. A 110/90-18 means the tires width is 110 mm wide. The 90 is the aspect ratio. This is the ratio of the tires height from bead to tread to the width.
The 90 is the percentage of the tires width. As in the height is 90 percent of the width.
So 110mm X 90% = 99mm. Now seeing as there is tire above and below the wheel you have to double this amount. As in 99mm X 2 = 198mm. Now you need to convert this to inches. 25.4 mm to the inch.
So 198mm divided by 25.4 = 7.79 inches. Now add this to the wheel diameter. As in 7.79 + 18 = 25.79.
So a 110/90-18 tire stands about 25.79 inches tall. This is a nominal spec. Different manufactures as well as types or styles of tire does effect these specs. Some may in actual measurement bit more or less than that.
Now lets do a 130/90-16.
130 x 90% = 117
117 x 2 = 234
234 divided by 25.4 = 9.21.
9.21 + 16 = 25,21
25.79 - 25.21 = .58 inches difference.
Again this a calculated diameter, actual measurements may vary.
A friend had am MU 16 tire he gave me. An MU tire is about 140/90-16
This was a bit taller and wider than the stock 139/90-16. On a tire there is a scrub rail built into the sidewall where the tread meets the sidewall. This is built in so if you scrub up along a curb or something like that your tires sidewall will not be damaged. This scrub rail rubbed on the chain guard and brake strut just a bit. I put it up on the center stand, idling in first gear and used my angle grinder to grind a bit of this scrub rail off so it cleared the chain guard and brake strut. I ran it this way till I wore out that tire.
I think I have pics somewhere of my 75 with the 16 inch wheel some where. I" look around to find them.
Leo

XSLeo said:

On my 75 I did swap in a 16 disc brake alloy wheel.

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XSLeo, glad you found and chimed in on this wheel swap thread.
I do feel very reassured today that this idea isn’t just too crazy.
My old 78E that has been parked for a few years now just keeps on getting better as parts and bits from other bikes and projects get set back there in the “top shelf” 78E zone.
I’m thinking the fat nice 16” wheel Ive found will really look sharp !
Making unexpected progress here
-RT

I found a few old pics. I looks a bit different now.
I can't find any with the stock 18 inch wheel.
I had a crash years ago and lost a lot of my pics.
a few more things about measuring tires. A tire on a narrower rim will measure narrower than when mounted on a wider rim. The marking on the tire are when mounted on a certain width of rim. What the rim widths a manufacturer uses to calculate tires sizes is anybodies guess.
Leo

That unflanged alloy 16 wheel is a hard thing to find. I've only seen one in my life. It was on a bike I spotted in the parking lot of a construction company.
If I could find a laced 18 inch wheel with a disc brake hub that was an easy bolt in or even a 16 I would do it. It looks a bit funny with the alloy on back and the laced wheel up front.
A lot of other bikes of that era used laced disc brake wheel. Most had a cush drive. These are not an easy bolt in.
I have thought that I could cut the hub out of a alloy wheel, then find some one that could turn it down so a set of flanges drilled for spokes could be mounted to the hub would be a start.
Getting a disc brake hub built that was a straight up bolt in then lacing it to a flanged alloy rim might be something that could sell. I just don't have a lathe or the skills to do such a project.
Leo

A wander 'round the shed with a tape measure and straight edge found 16" inflated tires at about 24 1/4 18" at 25 1/4, special shocks 12 3/4 standard (early) 12"
Leo; an early GS750 or 1000 spoke wheel hub isn't a bad project.
gggGary's latest XS project "madness"

If money's no object https://cognitomoto.com/products/xs650-rear-hub-disc-brake-conversion?variant=21382173377

XSLeo said:

That unflanged alloy 16 wheel is a hard thing to find. I've only seen one in my life.

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Only saw photos myself until this parts hunting adventure. “Offer Up” site had a 72ish front end with a cast wheel in the pic ? So I asked “what else” do you have ? I got pics back of quite a few junk wheels and this 79 was there in the grass too. $100 was his price.
The front match is on his “project bike”
in the driveway.
I’m gonna get that front somehow lol

When you start tire shopping, I think you're going to find 130-16's cost a bit more than 110-18's. Now that I have a Special, I've actually been able to live with a 16" rear rather than just an occasional ride on one. It's not that bad, not as different as I thought it would be as far handling goes.

I think for most street riders they won't find much difference. The difference is most noticeable if you ride one the jump right on the other for a ride.
If you wait a day or two you won't notice it as much.
Leo

After several attempts to purchase the matching front 79 Special II Aluminum rim I saw where I located my nice 16” rear, it’s seems to be a dead end.
So planning just back to stock 78E high shoulder rims again.. darn it !

Swapping the brake stay and chainguard will have you prepared for the if and when, I changed mine out some years ago.

nj1639 said:

Swapping the brake stay and chainguard will have you prepared for the if and when, I changed mine out some years ago.

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When you did, was the rear end noticeably lower ? Any pics ?