Finding actual tire width specs?

[80GS850GBob]

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.

The best for last today...lol
A} I asked about actual widths...don't believe I ever said I was gonna run anything yet...still trying to figure out intended tire widths compared to what I know I have to work with.
B}...was that a 140-150 radial tire or biased? I'm already in my comfy chair...you should be too...

 

[Steve]

Ah...that's the angle I was getting at! Radials need a wider rim. I can only, easily, fit a 3.5 rim back there and there's no intermediate size other than a 4.25 next {sucks}.

At least a 3.5 rim is better than the stock 2.5.

Over on the Goldwing forums, there is a lot of talk about going "darkside" by putting a car tire on the back of the bike. That is mostly on the 1800 Wings, starting with the 2001 models. The rear tire is a 180/60-16, I don't remember what the rim width is. I was curious about trying that with my 1500 Wing, but there was very little discussion on that. Finally found a few threads and gathered information on what tires they were running. The stock tire on the 1500 Wings is a 160/80-16. Note the difference. Narrower and taller than the 1800 tires. The rim on the 1500 is also about an inch narrower. Well, I tried it. found a tire that was narrow enough to fit my narrow rim. It has an incredible weight rating and is designed for light commercial use (London taxi), so it might work. It is a bit taller than a stock tire. I have to run maximum air in the shocks ALL the time, or the tire rubs on the inside of the fender, especially if I am carrying a passenger that is large enough to cast a shadow.

The really sad part, and the point of this post, is that I have to increase the air pressure in the tire to get any kind of stability. You would think that with a larger carrying capacity, I would not need to add as much air to carry the same load, but the rear end of the bike felt like it was riding on Jell-o. I have to run the pressure near the max of 55 psi, and it still feels squirrelly. Mostly because the rim is not wide enough to properly support the radial tire.

That tire should have given me 40-50,000 miles of service. I think I have about 3,000 on it, I will be changing it before doing much riding on it next season.

.

 

[80GS850GBob]

Ah...there's the rub...terrible pun, sorry.
While a given tire has the capability to run on, say, three different rims...it's usually going to best suited on only one. That is also indicative of what cycle its on as well...depending om what clearances "that" bike has for said tire. A lot of variables to consider.

On a correct rim, brand A runs a few mm skinnier than width spec while brand B runs a few mm over width spec...brand C could distort terribly on the same rim since their tire chart is waaay off.

You'll laugh at this comment, and that's fine...but just because you can do something to a motorcycle doesn't mean you should {or could}.
...and I'm not fully convinced that rear shocks one inch longer would tear up the uni because of the slightly added new angle - but untill someone tries it and confirms...who knows more than random speculation...

 

[Steve]

...and I'm not fully convinced that rear shocks one inch longer would tear up the uni because of the slightly added new angle - but untill someone tries it and confirms...who knows more than random speculation...

I am hoping that one inch doesn't make much of a difference, but we are doing it in the other direction. We got shocks one inch SHORTER for my wife's 850L. I figure that it's no worse than stock-length shocks with sacked springs and riding 2-up, the ride height will be the same.

I have not analyzed the actual driveshaft angle to see where it is perfectly inline with the secondary drive and how far it swings on either side of that straight line. My guess is that it might be straight with stock shocks compressed about an inch of their 4-inch travel. That way, when the suspension moves, it will stay relatively straight. For the occasional times you have the load of a passenger, the additional angle should still be within allowable limits. Using longer shocks will probably keep the same angle, but in the other direction, which shouldn't be a problem.

And, if you really get down and analyze the situation, it might not be the u-joint that fails. The whole reason this issue exists is because the u-joint is a simple, single joint. As the angle of the driven shaft increases away from straight, its rotational velocity changes twice in each rotation, due to the action of the yokes in the joint. The u-joint is at one end of the shaft, but the gears in the final drive are at the other end. What's to say that THEY won't be the ones to fail first? :-k In fact, maybe the ring and pinion actually hold up quite well, and transmit those speed variations to the SPLINES, causing THEM to wear? :-k

Something to think about.

.

 

[80GS850GBob]

I am hoping that one inch doesn't make much of a difference, but we are doing it in the other direction. We got shocks one inch SHORTER for my wife's 850L. I figure that it's no worse than stock-length shocks with sacked springs and riding 2-up, the ride height will be the same.

I have not analyzed the actual driveshaft angle to see where it is perfectly inline with the secondary drive and how far it swings on either side of that straight line. My guess is that it might be straight with stock shocks compressed about an inch of their 4-inch travel. That way, when the suspension moves, it will stay relatively straight. For the occasional times you have the load of a passenger, the additional angle should still be within allowable limits. Using longer shocks will probably keep the same angle, but in the other direction, which shouldn't be a problem.

And, if you really get down and analyze the situation, it might not be the u-joint that fails. The whole reason this issue exists is because the u-joint is a simple, single joint. As the angle of the driven shaft increases away from straight, its rotational velocity changes twice in each rotation, due to the action of the yokes in the joint. The u-joint is at one end of the shaft, but the gears in the final drive are at the other end. What's to say that THEY won't be the ones to fail first? :-k In fact, maybe the ring and pinion actually hold up quite well, and transmit those speed variations to the SPLINES, causing THEM to wear? :-k

Something to think about.

.

I'd be willing to bet there's a +/- 1" bit of flexibility built into the drive system...otherwise how many GS G's would be dead from touring weight/drive line issues?!
{-edit...engineered flexibility as in sustained drop with rise for dips in the road}
To reasonably assume that up to an inch of regular deflection is to be expected while riding even one up, due to road imperfections, it just has to be assumed as figured in for by the factory {see above to confirm}...the question is will long term deviation from the intended oem drive line centering be an issue...time would/will tell.

Was just tossed this tire size comparison link from another forum...pretty neat. Try it to see the difference in height between tire sizes..
https://www.tacomaworld.com/tirecalc?tires=130-70r18-130-60r21

 

[thebrandonbeezy]

I think i have the measurements on photobucket, ill check

 

[Steve]

Was just tossed this tire size comparison link from another forum...pretty neat. Try it to see the difference in height between tire sizes..
https://www.tacomaworld.com/tirecalc?tires=130-70r18-130-60r21

I don't remember which vendor it was, but one place I was shopping for tires had actual mounted dimensions for tires. It would not do much for comparing how much a tire changed by switching to a wider rim, but it was rather interestingn to see all the different dimensions for the same size tire.

Mathematically, a 130/90-17 tire should be 26.21 inches tall. I don't remember the brands involved, but one tire might have been as short as 25.5", while another might have been as tall as about 27".

There were also similar variations in the width, I just found it amusing that they all claimed to be the same size.

.

 

[80GS850GBob]

Oh yeah...MC tires are like shoes...they aren't all the same no matter how the size is listed...and add a different rim under it and you can change the profile yet again!

...just emailed the rim vendor I like for actual width specs on my two rim choices for the rear. The answer will determine which I can use as far as realtime clearance is concerned....and yes, it'll most likely be the 3.5 wide rim but there's the off {waaay off} chance the 4.25 might work. Hope springs eternal though....lol.

If I wind up with front and rear 3.5 wide rims I'll have to get two radial "front" tires since actual rear radial tires like to start at 4.00 and on...sheesh...

 

[80GS850GBob]

I think i have the measurements on photobucket, ill check

I just emailed Warp 9 for real time rim widths....I'll get an answer soon, I hope, as to which one can be used in my application. Then...the color choice begins!
Wish more companies ran 4.00 or even 3.75 rims for spokes...

 

[Steve]

If I wind up with front and rear 3.5 wide rims I'll have to get two radial "front" tires since actual rear radial tires like to start at 4.00 and on...sheesh...

If you mount a "front" tire on the rear, be sure to turn it around so it rotates the "wrong" direction.

Not sure how long a front tire will last on the rear. In the Wing world, it's more common to mount a rear tire on the front, especially for trikes.

.