Topic: Tire Size Help Needed 16" and 18" Maximums For K4 CB750 -- Please

[RRRToolSolutions]

I need to have my tires mounted this week on my 1974 restoration 836 project. I have two wheel sets, this stock 18" wheel/spoke combo (I just laced/trued yesterday) and a nice 16" Harley rim set-up I purchased at a swap meet.

My question - what is the largest tire that will fit into the K4 CB750 without any clearance problems? I ask because my favorite upgrade tire for old bikes is the Dunlop 501's. They come only in 130/90/16" and 130/80/18". When I bought this 16" tire/rim combo, the plastic inner-fender of the donor bike had contact damage from a tire. I'm not sure it was the same, but damage all the same. The 16" tire is approx 1" smaller in outside diameter than the 18", so the 90% aspect ratio does take care of about half of the 16"/18" differences. Will the 130's fit between the fender, the chain gaurd, brake rod and brace, and the swingarm?

You guys can help me by sharing your experience with these issues. I've already purchased the 130x18 501 for the rear, but it was before I bought the 16" and saw the damage to the plastic. This is a hotrod/restoration project, so the 4.00x18 ain't happening....but what will work for me?

Thanks in advance.

Regards,
Gordon

[jaknight]

Hello Ilbikes,

....but what will work for me?  Regards,  Gordon

     I cannot tell absolutely, positively whether it will work or not; I can tell you this......

     I have a '74 CB750 K4.  I have standard rims, 19 inch up front, 18 inch on the rear.

     I put Dunlop Elite II on the rear......... 120.  It clears the brake rod and brace by perhaps 1/4 of an inch.  I have had no problems with it, but frankly, I wish I had stopped at 110 and had gone with a different tread design.  When the tires I have do get worn down and need replacing, I will be dropping down in size.

     130?  I think it is too close to go with it; you might have to do a mod job for safety clearance.
I believe tread design, footprint, size and tracking with the front setup are very critical.

     But, then again, as a very recent traveler through a car's windshield, I have now developed very prejudiced opinions about safety.......

     I suggest you search this site and look for a posting by HondaMan on the subject of tires.  HondaMan has made at least 2 postings on this subject that I am aware of......... so I suggest you don't stop after finding his "first" posting.

     At any rate, best of luck with whatever you decide to go with......

     ~ ~ ~ jaknight ~ ~ ~

[merc2dogs]

  I can say that I ran a 130/90/18 on my bike for a while, and didn't have any contact problems, unless I was riding double but I am only 145lbs, and normally ride solo.
 I did have handling issues, it altered the rake/trail enough that I didn't realy like the way the bike handled. I went to a 17" rim from a newer bike that had decent rubber on it.

ken