Lower profile rear tire

[Pawl]

Now that we are deep into winter, I am starting to forge ahead on the ole 82 xs400 hack & slash project. I took some pictures of the progress. It was only then that I noticed that the rear tire is awful tall since I did a rake job on the front and moved the lower shock mount back over the axle. Right now it has Brigestone Spitfires on both : Front is 100/90-18, and the Rear is 130/90-16.
I would like to bring the rear tire height to be roughly equal height as the front (indicated by the green line) and keep the same rear tire width. I will be making a new seat and cutting everything south of the top shock mounts, and I am considering affixing a rear fender (of some sort) to the swing arm, I realize now that the rear tire height will determine where I would locate the fender. I looked on the net at some tire dimension charts, . . and Whew! . . they don't make it simple, that aspect ratio makes it hard to visualize. Anyone know what size would work?

 

[lhaolpa]

Go to a cycle shop and ask them to explain the sizes to you,and tell them your problem,asking them about mounting fees so they think you're going to have them mounted there.They'll tell you what the most expensive type cost,then go to motorcycle superstore and buy your tires cheap. lha

 

[eric123]

Run a 110\90-18 on the front or an 130\80-16 on the back...

 

[Reaper]

Personally I think it looks cool, reminds me of the hot rod big and little tire setup. I don't know if you want it to sit level when parked but when riding it it should level out with your weight. That's my 2 cents.....1.24 cents after tax.

 

[XSLeo]

Put air in that flat front tire and it just might be ok.
A 100/90-18 tire stands about 25.09 inches tall. A 130/90-16 is 25.21 inches tall. Less than 1/4 inch difference
If you uses a 130/80-16 it will be 24.19 inches tall.
Leo

 

[Pawl]

Put air in that flat front tire and it just might be ok.
Leo

Yeah really! Doh!, here I'll try again (now with added high mount rear fender I found at the dump a couple years ago in case I can't acheive a swingarm mount)

Thanks guys you are a great help! Your insight has helped me to avoid rushing into ordering new tires that may, or may not work. Our 2 motorcycle shops here are a waste of time and charge double from what I can order online (the closest big City is Edmonton, Alberta, 1000 miles due south). I dunno? I don't get it, maybe I have an optical illusion here, but when I get down and actually eyeball measure both tires, Leo is right, the rear looks to be only about 1/2" bigger hmmm? . . . What I am aiming for is something like in the pic below (with a cafe style seat and a fender mounted to the swingarm). I think the wheels on this 650 are 19" front, and 18" rear ( 1" diff.), and on my 400: 18" front - 16" rear (2" diff.). I'm kinda thinkin' Dual Sports on the 400 would look nice and agressive.

 

[XSLeo]

The stock front wheel on the XS650 was a 19 inch wheel. With either an 18 inch or 16 inch rear. That mag in your pic on the XS650 is a 16 inch wheel. All the mags used on XS650's were 16 inch, some disc, some drum brakes. One year they used a non flanged 16 inch 36 spoked wheel. The later spoked rears had a 48 spoked wheel with 64 spoked fronts.
I have a chart I found that lists the height of Bridgestone Spitfire tires. In my other post I figured out the height mathematically. The formula is width x Aspect ratio x 2 divided by 25.4 to convert from metric to inches + the wheel size.
As in 100 x 90% = 90 x 2 =180 divided by 25.4 = 7.08 +18 = 25.08 inches tall.
The chart list these sizes as this tall.
A 100/90-18 is 25.2 inches
A 100/90-19 is 26.2 inches
A 130/90-16 is 25.4 inches
If you want a taller front tire, I'm pretty sure the XS650 front wheel will fit your front forks. May need a bearing swap if the axles are different sizes.
Leo

 

[nitrofish1]

that last bike pic, that bike must be LOUD. i see megaphones on the darn thing

 

[XSLeo]

Yea, but with the exhaust empting out there will keep your butt warm on cold days.

 

[Pawl]

This bike, I think is my all time favorite build. The Shinya Kimura Knucklehead, (most of his bikes are in my top 10) Say what ya' want about the manifold/pipe but it is unique & cool!
It has the tire height balance, as well as a whole host of other design elements I'm striving for in my XS400 build . . . fuggin' thing looks like it's going 150 mph. just sittin' there. . .

 

[xschris]

Thats cool

 

[bcware]

I'm not a huge fan of the symmetrical tire sizes; it will hurt the handling on the bike. If you're just riding around town at low speeds it's probably ok though.

 

[XSLeo]

That Knuck has 16 inch tires front and back, Probably 5.00 16's both ends.
As far as Handling, bikes have used the same size on both ends about as long as there have been motorcycles.
Even with different size rims the overall height is very close.
Leo

 

[OleDoc]

i love the zero engineering look

 

[Leivur]

The wheelbase on that bike looks insane. Looks like somthing built to only run in a straight line like on the bonneville salts flats