• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

Tire question

  • Thread starter Thread starter Kyle M.
  • Start date Start date
K

Kyle M.

Guest
78 GS750, stock rims. What is the widest rear tire I can run? Stock is a 120/90 18 right? I want a lower profile tire and wide, like a sport bike tire.
 
Last edited:
Unlike more primitive four-wheeled forms of transport, wider is NOT better with motorcycle tires.

On a motorcycle, the curvature of the tread makes a big difference in handling. Stuff a wider tire on there, and it goofs up the tire profile and makes your bike handle like a turd.

4.00-18 translates to 110/90-18 in more modern tire sizes, although 120/90-18 might be OK too.

There are some who have invested great sums of money and time grafting later model sportybike swingarms, forks, and wheels onto their elderly bikes in search of that phat tire look.

Basically, if you want to go wider, your options are to either buy a sportbike or find a buddy with a machine shop and graft on sportbike suspension and wheels.

Or, and I know this is CRAZY talk, how about this... mount up the correct size tires and ride the snot out of your timeless classic motorcycle. You can get very modern, very sticky rubber (Avon AM26 RoadRider or Pirelli Sport Demon) in the correct sizes.

Stir in a bit of suspension work, learn to ride, and believe me, these old Suzukis will handle. Pay attention to your riding skills and you'll have no trouble staying ahead of or keeping up with the squids in the twisties.
 
The 130 will probably fit.
The 80 profile will keep it about the same diameter as the 120.
Do you care at all how the bike handles, or do you just want "the look"?
A wider tire on a narrow rim will not have the stability that it really needs for proper handling.
If you really have to have that really wide tire, you are going to have to do something to get a wider wheel in there, too.

.
 
I ran a 130 rear on my 79 750E for the 40k miles I had the bike and had no problems with it. Use a sticky tire though, not a touring type. Anything bigger will not fit between the swingarm anyhow.

Earl
 
bwringer said:
....or find a buddy with a machine shop and graft on sportbike suspension and wheels.
Click to expand...

I have no idea what you're talking about. :p :D

Seriously though, performance bias Pirelli Sport Demons or Avon Roadriders in a max 130 rear can make your GS handle quite well.

Michelin Pilot Power, Bridgestone BT002 RS or Pirelli Diablo Corsa 3 radials with the right suspension components and steering geometry can make your GS handle even better, but that's a whole different story.
 
earlfor said:
I ran a 130 rear on my 79 750E for the 40k miles I had the bike and had no problems with it. Use a sticky tire though, not a touring type. Anything bigger will not fit between the swingarm anyhow.

Earl
Click to expand...

There you have it folks.

Earl, was that a 130/90-18 or a 130/80-18?
 
I guess I will just get the 120/90/18 for the rear and a 100/90/19 for the front...sound good?
 
Sounds good to me.

There have been MAJOR advances in tire compounds since these bikes were made, and the current batch of tires might even be better than the racing rubber that was available at that time. Get the right size tires, then "ride the snot" out of them as suggested.

.
 
comparing 120/90 and 130/80, the 130 tyre will not be any wider than 120!
if you want the widest look possible you want a 130/90 tyre
 
What size rear rim is on the 750? The 850/1000/1100 bikes have a 2.5" rear wheel which accepts a 130 quite nicely - in fact, it's the GSR defacto standard tires size for those bikes. 120 is fine but I'd go 130 if the rim is wide enough.
 
And I'll post it again...

http://www.steelthundercc.com/tiresizes.html

Here is a tire conversion chart that will give you the measurements for each tire.
I went from a 120/90-16 to a 130/90-16. There is very little difference in the handling with that small of a change...but these guys are right. The wider the tire, the slower the handling. Start with a quality tire and a small size increase.

Measure the clearance from every angle. Not only do you have to worry about the swingarm rubbing, you've got the chain also.
 
psyguy said:
comparing 120/90 and 130/80, the 130 tyre will not be any wider than 120!
if you want the widest look possible you want a 130/90 tyre
Click to expand...

Actually, a 130 tire of any aspect ratio (the 90/80/70 part of the size) should be the same width, 130mm. The 90 aspect ratio tire will have taller sidewalls, roughly 90% of the width. The 80 aspect ratio will be roughly 80% as tall as it is wide, and so on. In actuality, the lower aspect ratio tires tend to be wider than the same width tire with a higher aspect ratio but that's what the numbers were meant to designate.

Thanks,
Joe
 
120/90 is 4.50 to 4.75 inches wide.

130/90 is 5.00 to 5.10 inches wide.
 
Milimeters are too small for me to read on the ruler. Besides, this is the U.S.A...we haven't converted to the metric system yet.
 
psyguy said:
comparing 120/90 and 130/80, the 130 tyre will not be any wider than 120!
if you want the widest look possible you want a 130/90 tyre
Click to expand...


Considering the 120 is 4.75 wide and the 130 is 5.120 wide, I think the 130 is wider. The over heights will stay near the same. The 130/80 and 130/90 will be the same width, just the 130/90 will be taller.

Edit:I am too slow for this forum....you guys are quick!
 
Like I said, I went from the 120/90 to the 130/90. I actually like it...and I can't tell you exactly why. The bike just feels a little better going straight and only slightly more steering effort.

Make sure you check the clearances. On paper there is little dfference...installed you'll be suprised at the difference.

The big thing is to buy a good quality tire. The size won't matter if the tire won't grip the road.
 
not disputing anything said above...
however:
130/80 tyre (due to its lower profile sidewal) is going to be so squeezed on the 2.50 rim that WHEN MOUNTED is not going to be 10mm wider than the 120/90 tyre and is going to overall appear smaller/narrower than the 120/90 tyre

just try it if you dont believe it :p
 
You must log in or register to reply here.
Back
Top