Correct tire size for 1976 kz 900

Could someone please advise me of the correct, from the factory, tire size for the rear of my 1976 kz 900.

I had a 130/90/18 on there until last night when it went flat on me 15 miles from home. Had to limp it home on the flat so pretty much destroyed the tire.

I have a 140/90/18 in the garage with plenty of tread on it but, if I use it, I'm increasing the rolling diameter by 0.7". Not much I know but just curious as to the "correct" size. Thanks.

I believe that the correct size is 110/80-18" or a 4.00-18". You'll most likely not get the 140 on the rim and if you do you'll most likely end up hitting the swingarm with the tire anyways.

Put a 110 or a 120 on there and you'll be OK. The wider the tire on a stock rim the less contact patch you have since the bead has to be sqeezed to fit the narrower rim and in return the tire "rounds" over more.

Later, Doug

I had a 130/90 18 Conti on the back of my 900 then switched to the "correct" size of 110/90 18. The 130 was 1" taller overall than the 110. That dropped my fuel mileage from 127 miles to a tank to 90 miles to a tank. When the 110 wore out I put a 120 on it. The 110 didn't look right either,looks too small.

Post edited by: KZJohn, at: 2007/06/13 14:54

Actually a 110/90-18 is not the correct size, nor is a 120/90-18. A 4.00-18 is the right size. That's not to say either of those other tires won't work, they are just not the right size. The difference comes in that a 4.00-18 is a 100% aspect tire meaning the same height as width, where the /90 tires are a 90 aspect ratio meaning a lower profile. Running a 110/90-18 will give you about the right width, but lower profile so more rpms going down the road than a 4.00-18. A 120/90-18 will be wider than a 4.00-18 but with the 90% aspect ratio, the diameter works out pretty good. If you look, several tires are still made in 4.00-18 including Avon, Metzler, Continental and most the budget brands like IRC, Chen Shin ect. I'd either run a 4.00-18 or a 120/90-18 if you want a little wider tire.

Thanks for all the input guys. The tire I destroyed yesterday was a 130/90/18 Bridgestone Spitfire which actually fitted with a little room to spare. the "old" tire I took off when I fitted the Spitfire was a Hi Max 140/90/18 and it too JUST fitted.

I'm going to put the Hi Max back on for right now as it has some good tread left on it but will likely go back with another 130/90/18 Spitfire when I can better afford it.

Anyone have any "favorite" places to buy tires?

Thanks again for all the great responses.

Not to sound biased but I'd buy a tire from a motorcycle shop. (Of course I worked at one for 5 1/2 yrs) But I've heard several Sale Reps say that normally a tire manufacturer will sell higher grade tires to big distributors like Tucker Rocker, Part Unlimited, Motorcycle Stuff, KK, Western PowerSports, etc, and lower grade tires to mail order distributor like Dennis Kirk, Competition Accessories, etc.

I've seen tires that were mail ordered need over 2 oz of weights to balance them. And I just recently put on a Dunlop D208 rear tire (my 2nd one from KK) that was perfectly balanced without adding any weight.

I've installed quite a few tires in those 5 1/2 years and never had to put more than 1.5oz on tires that WEREN'T mail ordered.

I'd pony up a little more $$ for better quality. BUt that's my $0.02.

Later, Doug

Got my old 25% used 140/90/18 Hi Max I had in the garage fitted on the rim last night by local Honda of Coolsprings store here in Franklin, Tn. I can highly recomened them. They did it whilst I waited (25 mins) took their time and were very carefull. Took 3/4oz to balance. Total cost $ 26.46, including a new rubber spoke/wheel band to go between the tube and the wheel.

Got it all back on the bike last night and rode the bike to the office this morning. All good.

FYI, for those who care, the 140 Hi Max has clearance of approx 4mm either side. So, 140 just works but a 150 wouldn't.

I think when it comes time to bin the Hi Max, I'll probably go with a 140/80/18 for a slightly lower profile (just over 1/2" lower).

Thanks again everyones input on this

Man I thought my 130 Spitfire was tight.
That's what I call a TIGHT FIT.
Glad it worked for you~ Pat

Yup, purdy much fills up the space in thar. Thanks again everyone's input on this.

But I've heard several Sale Reps say that normally a tire manufacturer will sell higher grade tires to big distributors like Tucker Rocker, Part Unlimited, Motorcycle Stuff, KK, Western PowerSports, etc, and lower grade tires to mail order distributor like Dennis Kirk, Competition Accessories, etc.

Where do you think Dennis Kirk gets their tires?

Every tire that I have bought from Dennis kirk (10-12) has had a Drag Specialties tag on it, and Drag Specialties is an awful large distributor, not as big as Parts Unlimited (the largest I think), but still pretty big.

I have heard it said by people in the industry, that Dennis Kirk is the retail outlet division of Parts Unlimited. I don't have any personal knowledge of the matter though.

I've never bought from Dennis Kirk but I do know that Drag Specialties is the "American" side of Parts Unlimited and that PU is the "Metric" side of DS.

The rep we had for PU/DS was Ed Bardoe (sp.?) and I never heard anything like that from him.

I guess it doesn't matter since Barne is sticking with the Hi-Max.

Later, Doug

BARNEYHYPHEN wrote:

Anyone have any "favorite" places to buy tires?

I just found these folks from a link in another thread:

www.americanmototire.com/

I just ordered some Dunlop GT501s from there, and their price was $30 cheaper (with shipping) than what I was able to find elsewhere.

I already called my local Kawi shop and confirmed they would mount them for me--$20 ea.