Modern tires and wheels

[rokcrlr]

I am gathering parts to build my bike. I have a 79 xs and have picked up a 99 gxsr750 inverted front end for it, I want to run the wider wheels and tires that are used on street bikes. My son tracks a R6 and has a plentyful source for used race tires at a good price, LOTS of meat left for street guys. Any how, I know I may have to move my chain over a bit. I also have a RM350-PE250 rear aluminum swing arm that I'm going to try and use. It is 1" wide thru the fork area than a XS is so i'm sure I have room for the tires. . Just wonder what other guys have done so they can run modern type tires. I saw in Motor cyclist this month where a guy in San Diego builds street trackers" MULE" and he has someone out there that can widen mag wheels for modern tires. I'm just trying to get a discussioin going on doing this . Lets hear some ideas people.

 

[gggGary]

There's a guy that custom welds offset front sprockets and LH cover spacers.

http://www.650motorcycles.com/OffsetSprockets.html

 

[jd750ace]

Using race tires on the street will land you in the hurt locker. Not an opinion, but a fact. You cannot ride hard enough on the street to get enough heat into them for the compounds to come in and grip correctly when they are new, much less used. Even if they are "D.O.T. RACE" tires, they are cooked after a race, Everything that makes them pliable and good tires is expended, and they just become harsh riding and non-gripping and will not work correctly to use up that middle.
Seen a few people trash some nice bikes like this buying club racing "pull-offs out at Cresson after the CMRA races. REALLY bad idea in my opinion.

Mule's trackers are beautiful works of art and fine machines, but way out of my league.

Here's a quote from Richard Pollock, owner, operator, and builder at Mule motorcycles from the Mule web site:

You can expect an XS650 Yamaha-based bike to start at approximately $23,000, and the Harley-based bikes to start in the $31,000 range. The Harleys tend to cost more due to the added complexity of the build.

START at 23K. I own 3 bikes, and the combined MSRP does not add up to 23K. Didn't even pay that much for my car when it was new.

If you have the funds to build something on the order of a Mule, then knock your self out and post pics, but if your budget includes used track tires, those widened wheels are gonna hurt your feelings. You would probably spend more money on widened wheels and getting them fit onto the bike than the average person here bought their bike for.

Just a few pennies worth. Good luck with your endeavor.

 

[rokcrlr]

jdrace, I'll have to disagree with you. Race tires build heat faster than DOT tires, My son has used them for quit awhile now. And has no issues with them not working. street tires have harder compounds than race tires for mileage. Yes they are DOT race tires, By what your saying ,The people who only do track days with their bikes need to be putting new tires on their bikes everytime they go on the track I have been involved in some sort of racing for years , We have tires that are 1-2yrs old and still perform,tho we do grind off the top layer. Next opion.This discusion is for running wider rims and modern tires, not argueing to point on whether you can run the old race tires .

 

[gggGary]

Note the issues with overloading the output shaft bearing with "large" sprocket offsets.
IMHO Going "too far" with sport bike components doesn't fit in with the basic concept of a light "low powered" vertical twin motorcycle but it's a big tent and there is lots of fun to be had wandering off into the wilderness of home engineering. Seriously.
Packaging is tight under that LH cover, pay heed to the needs of the clutch release mechanism. My own "mod" thoughts stop at about a 130 140 rear tire. the chain runs inside the frame so there is a limit to how wide you can go before you start fighting that.
Then you get into the issue of the small diameter rear sprockets needed for reasonable gearing on an XS. get a low profile 17 rear rim/tire and it's a big issue. Not much fun having a bike gearing limited to 45MPH!

 

[jd750ace]

Good luck.

 

[rokcrlr]

Good luck.

Did a little more checking on what you posted. Back in the days,yes race tires would heat cycle then be junk. Modern race tire technaligy has made those things old wives tales. Theres no "good luck" to it. DOT race tire will work fine on the street, of course will depend on the compound, but will get you far less miles than a street tire will. My son has 1000's of street miles on dot race tires along with several of his friends he help supplies.

 

[rokcrlr]

his is the look I'm sort of trying for.Images 8,9 and 10
http://mulemotorcycles.net/XS650-yamahas-1.html

 

[jd750ace]

Did a little more checking on what you posted. Back in the days,yes race tires would heat cycle then be junk. Modern race tire technaligy has made those things old wives tales. Theres no "good luck" to it. DOT race tire will work fine on the street, of course will depend on the compound, but will get you far less miles than a street tire will. My son has 1000's of street miles on dot race tires along with several of his friends he help supplies.[/QUOTE

http://www.sportrider.com/tech/tires/146_0002_street_vs_race_tires/

Andrew Trevitt has about a half a million miles on street and track in the past 15 years, and has been a certified mechanic for 20. I don't think he's anyone's old wife. There's a reason the pros use tire warmers before a race, and we don't before we commute.

BTW, here's an extra sharp street tracker I shot a couple years back at the Dallas Cycle World show. I like the Mule Shell bike myself, but the guy IS an artist.

 

[rokcrlr]

Chain only has to be offset about the thickness of the spocket, and I think it will still clear everything. As far as gearing goes, Sport bike tires run in the 26.5" dia. while the tire on the XS is 23. About a 15% differance in gearing so a 39-40 even a 42 wouldn't be that far off. I picked up a supermoto rear wheel setup to see what it will do. 4.25" wide wheel and will take a 160 in tire. Hub is off an XR650 honda so a 40 tooth rear spocket is available. I'm using a RM250 aluminum swingarm which is 1" wider between the fork of it. Have friends with machine shop, plus my own lathe and another one that is an iron worker for welding. I'm going to replace the swingarm pivet with another tube that will take the xs bolt . A little fabing , but should work out fine.I have plenty of spare parts and several drive spokets, so I'm sure that can be solved also

 

[XSLeo]

If you are running the standard's 18 inch rear the tires stand about 26 inches tall. The later Specials ran a 130/90-16 that stands about 25.5 inches tall. I wonder where you found a 23 inch tall tire on any XS.
If you did run that short a tire you would need an even smaller than stock rear sprocket not a larger one.
Leo

 

[rokcrlr]

I measure the 180/55/17 tire on my sons R6 track bike, Then I measured the 130 and the 150 tires on my 2 Xs650's

 

[XSLeo]

A 130/90-16 is about 25.5 tall. A 150, if an 80 aspect ratio, -16 is about 25.5 tall.
A 180/55-17 is about 24.75. Still none at 23 inches.
All these sizes will require the same size sprockets as stock or smaller to get decent highway speeds. Going with a 40 tooth will give tremendous accelleration but highway cruising won't be fun.
Most of what you have said sounds good. There are many modern tires out there that fit the stock wheels.
Leo

 

[rokcrlr]

Leo , not trying to argue with you, but I measured these myself with a wheel stagger gauge, Very accurate, maybe it depends on brand of tire. But there is a 15% differant in the diameters from one to the other and it comes to running 39 tooth sprocket on the back, to make up the differance, I won't be highway riding with the 650, not enough motor for my taste for comfortable highway cruising.. On a side note, Mule motorcycle does this all the time and has built dozens of bike. If I have to get a custom rear sprocket made so be it.

 

[Scrambled]

Big sprockets = big vibrations . I tried a 36 tooth on a well tuned XS650 (mine) and I took it off right away. 17 /34 works well, got nice bottom and mid range and as much top end as I need .