76 KZ900 A4 Largest tire to fit rear wire spoke rim?

I would like o keep the wire spoke rims on this build but I am curious how big a tire I can get on the rear stock wire rim with the drum brake. I will extend the swingarm 6 to 8 inches. I got a 150 on my LTD no problem with plenty of room left but this rim looks smaller.

Don't go bigger than the recommended size.
Tyre wall flex will ruin the handling.

wrote:

Don't go bigger than the recommended size.
Tyre wall flex will ruin the handling.

+100, not to mention a 6-8 inch longer swingarm....

wrote:

wrote:

Don't go bigger than the recommended size.
Tyre wall flex will ruin the handling.

+100, not to mention a 6-8 inch longer swingarm....
 

If OP was worried about handling, they wouldn't be putting on the largest tyre they can and extending the swingarm would they

I believe 4.00-18 is the stock size, which is slightly wider than a modern 100/100-18. A 130 should fit, a 140 may fit. A 130/80-18 tyre is probably the best 'safe' tyre size that keeps the close to the original final drive ratio (only about a 4% increase which will keep gearing close to the same).

I personally wouldn't make these mods either (I'd stick to 110, maybe 120), but it's your bike.

Assuming the rim is 2.15 like many other KZ's, I'd limit the width to 120.  Even that size is pushing the acceptable limit by most tire manufacturers standards, but Kawasaki used that size, so you can too.

I agree with the previous posts.  The stock size is roughly 110.  I currently run a 120 and that's as wide as I will go personally.  I have run a 130 and it chewed a slot in my chain guard, and the sidewall was clearly distorted.  But technically it did "work".

The tire manufacturers generally lists a recommended rim and rim width range.

For Avon Roadrider Mk2 (the tires I'm using), the widest they recommend for use on a 2.15" wheels is 110/90-18  (recommended for 2.15-3.00" rim).  The 120/90-18 and 130/80-18 recommend a rim range of 2.5-3.5", which is kind of close to 2.15"?  As I said, I'm running a 120 and it seems ok.
Interestingly, the 120/90-18 lists the actual width as 129mm wide (closer to a 130), and 130/80-18 shows a width of 137mm wide (closer to a 140).  That Avon 130/80-18 is probably the widest tire you could put on a 2.15" rim.

www.avontyres.com/en-us/tyres/roadrider-mkii

For comparison, the Bridgestone BT46 130/80-18 also gives a rim range of 2.5 to 3.5", but the listed tread width is 128mm, about the same width as the Avon 120/90-18.

www.bridgestone.com/products/motorcycle_...oducts/detail/pr176/
 

Also worth mentioning - if extra rubber on the ground is what you're after, you won't get it by going for a larger tyre. It sounds counter-intuitive I know, but the rim width isn't changing, so when you go wider, much of that width is being pulled back by the rim pinching the sides in. The tyre may well be wider, but the pointy profile caused by the narrow rim will result in a smaller contact patch.

My 77-kz has a 3.5 inch rim laced to the stock hub with a 150/70-ZR 18 tubed tire. The swing arm is stock. I did have to notch the chain guard for fitment. 

Would you happen to have pics?

I have a 150 on my 78 LTD so I was hoping for something similar on the wire spoke for the 76, I really want to keep the drum brake set up
 

Seeing your extending swingarm. Don't go too long! (It's not a BUSA on cycledrag!) You need a wider rim, just for looks? Make it easy and go with a Suzuki GS 1100 and a 3.5 rim. They show up on ebay from Oink or JJ Copper would have one.Unless you can spoke and true it yourself. Try and find a person to lace and true a spoke rim nowadays!I added 4" to a stock swingarm with a 4" x 16" hog rim with a 150 tire. using 3/8" offset with a 630 chain.Then this bike just sold, GS Szuk had a 3.5 with a 5.5 slick. I shimmed it for a stock front sprocket. Tear it apart! Start building stuff! Then it will sit for 12 years like me!     Crusty Old Bastard that I am! I have built a few!
Plus I put a Harley hubbed parts with 530 chain with a 5.5" x 18" with a 180 tire. couldn't find finished pic, that had a 5/8" plate and offset. And a fiberglass Beasly fender. Sold it to a guy who wanted the shocks kept. I wanted struts. But it was his money.
Just do it!

Marty in Buffalo

Back then, (the 80s), I got the Akront rim and spoke kit from Kosman Specialties and had them lace it up also. Never had any problems with clearance or handling.  R.I.P to Sandy Kosman who passed away this year.  Interesting piece on him here. Good luck on your build.   www.dragbike.com/top-fuel-motorcycle-legend-sanford-kosman/