Finding actual tire width specs?

[Guest]

I've got a questions folks...still planning on 17" hoops for my G model, but I'm stuck at the stage of figuring out what the max hoop width could be for my shaft drive bike. Adding to that constraint is the additional tire width issue - all needs to clear the shaft drive side of the swing arm which is the tight side. Since the oem cast rim is 17" with a larger tire {but skinny rim} my choice of an 18" is still an option as well to move the whole mass farther out to the shaft drive inside cut out/dent that's there.
So, my question is are there actual tire width specs available for tires, as in installed on a correct width rim, and what to expect for real time width side to side?...not as bead, width wise, on the rim.
Sounds dumb, but I need to figure this all out before committing to a hoop width. For me, I figured that the width ratio aspect spec was for sidewall but sans any added flaring to tread.


...then I can attempt to reconfigure new rim/hoop offset and both spoke lengths...good thing I love puzzles.

[Steve]

First things first, ... where are you going to find an 18" rear wheel?

Check with the various tire manufacturers for actual tire specs, but I can tell you that a 140/90-17 tire (don't remember which brand) would hold a quarter against the swingarm. 130 is pretty much the widest tire you can stuff in there and leave at least a bit of clearance. The width of the wheel won't change the width of the tire much, if any, unless you get out past 4 or 5 inches (stock is less than 2.5). Even then, I don't think the sidewalls will be pushed out past the edge of the tread. If you somehow manage to find an 18" wheel, the overall tire will be taller, unless you go with a lower aspect ratio, but your widest point of the tire will be pushed farther away from the axle, which is deeper into the taper on the swingarm. You would have to measure rather carefully to make sure nothing hits there.

What is the incentive for an 18" wheel?

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[80GS850GBob]

First things first, ... where are you going to find an 18" rear wheel?

Check with the various tire manufacturers for actual tire specs, but I can tell you that a 140/90-17 tire (don't remember which brand) would hold a quarter against the swingarm. 130 is pretty much the widest tire you can stuff in there and leave at least a bit of clearance. The width of the wheel won't change the width of the tire much, if any, unless you get out past 4 or 5 inches (stock is less than 2.5). Even then, I don't think the sidewalls will be pushed out past the edge of the tread. If you somehow manage to find an 18" wheel, the overall tire will be taller, unless you go with a lower aspect ratio, but your widest point of the tire will be pushed farther away from the axle, which is deeper into the taper on the swingarm. You would have to measure rather carefully to make sure nothing hits there.

What is the incentive for an 18" wheel?

.

Take a look at one of your G models with oem cast rims...note the indent on the inside of the drive side of the swing arm...that's the sweet spot to land a tire as it was intended to be with a biased tire.
Oem 17" cast rim/wheel with a higher ratio tire will put the widest part of the tire right there in that indent....for me though, wanting to run a radial tire with a lower ratio will pull that width in towards the axle more - unless I run an 18" hoop that pushes it back out.
There are some 18" hoops for the spoke guys to play with, but tire choices are better for running 17" hoops.
Sorry, I suppose I should've stated that I was shooting for radial tires....

[80GS850GBob]

Btw- I'm thinking a rear max of 3.50 hoop width...4.25 would be great but likely a pipe dream with the oem "shaft drive" swing arm.

[sharpy]

The whole back end is made for a 130 tyre. where you slide the tyre in between the diff and swingarm isnt much room left when u have a 130. You say u want 18" radial, once again u struggle with a 140 and even then the profile be only 70% of witdh so the whole bike would squat in the rear limiting ground clearence. And where you finding spoke wheels unless ure paying for expensive custom hub? Have you priced the cost of hub, spokes and a 3.5 x 18 rim? Be worth more than what u buy a average 850 for.

[thebrandonbeezy]

There's plenty of room to notch the swing arm more if need be

[thebrandonbeezy]

We've gotten the hub part figured out

[Steve]

There's plenty of room to notch the swing arm more if need be

One thing to remember when you start notching that swingarm, ... there is a driveshaft spinning inside it.

.

[Steve]

What is the incentive for an 18" wheel?

Sorry, I suppose I should've stated that I was shooting for radial tires....

Yep, that would have explained quite a bit, but still leaves the head shaking.

Take a look at one of your G models with oem cast rims...note the indent on the inside of the drive side of the swing arm...that's the sweet spot to land a tire as it was intended to be with a biased tire.

Would the swingarm really care if it was a bias or radial tire?

Oem 17" cast rim/wheel with a higher ratio tire will put the widest part of the tire right there in that indent....for me though, wanting to run a radial tire with a lower ratio will pull that width in towards the axle more - unless I run an 18" hoop that pushes it back out.

I see your reasoning, but I'm not sure I agree with it. I will have to look at one of my bikes to see how the tire relates to the indent.

Something to keep in mind: ALL the shafties 850cc and larger use the same, exact swingarm. Some of them have 17" wheels, some have 16" wheels. Since they all have the same swingarm, the indent must work for both sizes. I think your lower profile 17" tire might split the difference on where it lands in the indent. I will go out to the shop in a few minutes to compare my 850G with a 17" wheel and my wife's 850GL with a 16" wheel to see how they compare.

.

[Steve]

OK, I have checked the two 850s out in the shop.

It is just a tad difficult to get a decent picture, but here goes.

This is my 850G with a 130/90-17 Shinko Tourmaster 230:


Here is my wife's 850GL with a 130/90-16 Shinko Tourmaster 230:



As you can see, it's still difficult to tell where the edge of the tire is, so I broke out a tape measure.
My 17" wheel:


Her 16" wheel:


It appears to me that the edge of my tire is at the 5 3/8" mark, her tire is about 5 1/4". The end of the tape is just butted up against the flange on the end of the swingarm. As mentioned in my last post, the swingarms are the same, so the reference point should be the same.

I think your concern should be focused on getting the width of the wheel correct to properly support a radial tire, I don't think you need to worry about sourcing an 18" wheel. I think the tire selection is much better with 17" rubber, too, but I don't have anything here that will support radials, so I haven't done any of that type of shopping.

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[sharpy]

OK go for it. use a 3.5 rim with a 140 or 150 tyre. Ill grab a chair and have a sit down and wait.

[thebrandonbeezy]

I ran a 150 on my red gs when i swapped to the 3.5x17 from the vx800... also with a spoke wheel he could set the rim slightly off center.. not that itd need it. There was about an 1/8 between my tire and swing arm

[limeex2]

I ran a 150 on my red gs when i swapped to the 3.5x17 from the vx800... also with a spoke wheel he could set the rim slightly off center.. not that itd need it. There was about an 1/8 between my tire and swing arm

How well will that align with the front wheel? I believe The bead area of a bias ply and radial are quite different but I suppose you could run a tube.

[thebrandonbeezy]

The difference is not noticeable while riding

[80GS850GBob]

Lets see if I can address these in somewhat order;
- Given the GSX-R front end I have for it and the intended {but yet to be determined} rear shocks, I wanted better grade radial tires to maximize the theme of "improved handling" all around...I'm not Rockefeller, but I'll throw money at what I want it to be when finished - a better handling, one off, wire spoked wheel GS shaft drive. If I wanted something else, bike wise, I'd buy something else...simple. My 1000g will be a restomod..my 850G will be stock except for the salty monk upgrade and the Windstar fairing.
-the rear "hub" is a '95 Suzuki VS800 shaft drive hub with 36 spoke holes to match the front GT750 36 spoke hole hub count....I'll loose the rear disc to a drum but make up for it on the 6 pots and blackbird 22mm offset 310mm discs up front.
-Current rear tire is a bridgestone 130/90 17" on the factory cast 2.5 wide GS mag. Tire wise, I don't intend to go much bigger than that....BUT....swapping to a radial on an inch wider rim is why I'm asking for tire and width suggestions since that's new territory for me...I hope that some here have gone a similar route on their modded GS bikes and can lend some input.
- The idea of an 18" hoop was to simply move the rim farther out, if need be, to hit the sweet spot on the swing arm indent...but 17" radial tire selections are more plentiful.