Rear tire shredding :(

The original rear tire size was 4.00H-18 The closest size in metric is the 110/90. I have that on now, but have used 120/90. I like the 110 better, the bike feels easier to handle, lighter feeling. About the same as the 120 I guess.

I wouldn't use a 130, it seems too wide for the narrow rim, and actually the 120 is at the max size but a lot of guys use them without issues. The data sticker under my seat says MN90 for the rear, which is equivalent to the 4.00H and the 110/90.

I think there are still places that sell the inch size tires, doesn't Ron find them for his 650's?

OKC_Kent wrote: The original rear tire size was 4.00H-18 The closest size in metric is the 110/90. I have that on now, but have used 120/90. I like the 110 better, the bike feels easier to handle, lighter feeling. About the same as the 120 I guess.

I wouldn't use a 130, it seems too wide for the narrow rim, and actually the 120 is at the max size but a lot of guys use them without issues. The data sticker under my seat says MN90 for the rear, which is equivalent to the 4.00H and the 110/90.

I think there are still places that sell the inch size tires, doesn't Ron find them for his 650's?

We must use different references. According to mine, the metric closest equivalent to the stock 4.00 tire is the 120/90 tire (see table below), and the 110/90 is equivalent to the 3.50 tire.

I have used 130/90-18 on rear but as you point out the rim is narrow for that size and actually deforms the cross section of the tire so there is no more tread on the ground than on a 120/90-18. Having run the original several tire brands on my KZ650 in the past 35 years in 4.00-18 and 120/90-18 and 130/90-18 my experience has been that of the 3 sizes the 120/90-18 works the best.

AS far as his original issue, the tire rubbing on the fender, none of the tire sizes listed above would do that if the suspension was working properly. I believe those replacement shocks on his bike are not the correct size or type for the KZ650 or the tire would not rub no matter how much weight was applied or how big a bump was hit because the shocks would bottom out before the tire hit the fender. Ed

Tire Sizes
There are basically three different systems of tire description: Inch system (You are probably familiar with it as tire size readings like 5.00 - 16 or 4.50/S/18), the Alphanumeric System (for example: MT 90-16) and the Metric System (for example: 130/90 - 16). The last numbers are to describe the rim size. Before that number there is generally a dash or one of the letters S, H or V. This is key to speed range: (S) tires are up to 112 mph, (H) tires are admissible for speeds up to 130 mph, and (V) tires for 150 mph and up. Alphanumeric System and Series 80 are describing low-profile tires, which means the height is small than the width and the proportions to the width is fixed. Only in the Standard Inch-System can we find tires with equal width and height which is then a "square-profile".

Metric Alphanumeric Inch-System (Series 90) Inch-System (Series 82)
80/90 ---- 2.75 ----
90/90 MH 90 3.00/3.25 ----
100/90 MJ 90 3.25 3.60
110/90 ML 90 3.50 4.10
120/90 MN90/MP90/MR 90 4.00/4.25 4.25/82/4.40
130/90 MT 90 5.0 5.10
140/90 MU 90 ---- ----

Ed, those tables only consider circumference, which is important for gearing and speedo accuracy. But rim width is much more important to consider than circumference. 4.00 = 102 mm, although most tyres listed in inches tend to be wider than they should be in theory. So a 110/90 will be the closest you will get to a 4.00 on average, although actual sizes will vary from brand to brand and model to model.

If you take a look here www.avontyres.com/motorcycle/roadrider you will see that a 4.00 can be used on rims between 2.15 in (like the KZ650 use) and 3.00 (like the UniTrack GPz750 use). A 120/90 fits rims between 2.50 and 3.00 in and is hence too wide. Sure, it will work on a 2.15 in rim, but will not be able to retain its profile in a manner the maker intended. A 110/90 fits the same rims as the 4.00. The perfect match for the 2.15 in rim is a 90/90.

There are 120/90 tyres available that will suit also a 2.15 in rim if you search around enough as different brands and different models will be targeted towards different segments, but more often than not they will be made for a 2.50 rim.

EDIT: My bike came with this in size 4.25 on the rear and it seems to fit and work surprisingly well powersport-superstore.amazonwebstore.com...BLK/M/B000GRN11M.htm

Another method, without needing to remember a bunch of numbers, is to see whether the tire bulges over the rim like a fat guy's belly when wearing pants with a too tight waistline. :ohmy:

Good Fortune!

But then you will not know until after you bought it

Patton wrote: Another method, without needing to remember a bunch of numbers, is to see whether the tire bulges over the rim like a fat guy's belly when wearing pants with a too tight waistline. :ohmy:

Good Fortune!

Henceforward referred to as "Patton's belt mod"

faffi wrote: Ed, those tables only consider circumference, which is important for gearing and speedo accuracy. But rim width is much more important to consider than circumference. 4.00 = 102 mm, although most tyres listed in inches tend to be wider than they should be in theory. So a 110/90 will be the closest you will get to a 4.00 on average, although actual sizes will vary from brand to brand and model to model.

If you take a look here www.avontyres.com/motorcycle/roadrider you will see that a 4.00 can be used on rims between 2.15 in (like the KZ650 use) and 3.00 (like the UniTrack GPz750 use). A 120/90 fits rims between 2.50 and 3.00 in and is hence too wide. Sure, it will work on a 2.15 in rim, but will not be able to retain its profile in a manner the maker intended. A 110/90 fits the same rims as the 4.00. The perfect match for the 2.15 in rim is a 90/90.

There are 120/90 tyres available that will suit also a 2.15 in rim if you search around enough as different brands and different models will be targeted towards different segments, but more often than not they will be made for a 2.50 rim.

EDIT: My bike came with this in size 4.25 on the rear and it seems to fit and work surprisingly well powersport-superstore.amazonwebstore.com...BLK/M/B000GRN11M.htm

While AVON (and I'm sure some others) recommend the 110 size not all tire manufacturers do. Continental (and I'm sure some others) recommend the 120 size tire for the KZ650 (see table below). Apparently either size will work; personally, I'll continue to opt for a little more tread rather than a little less.

As I mentioned, you will find 120/90 tyres made for 2.15 in rims, also because virtually every bike made before 1983 used a 2.15 in rear rim (or narrower) so there is a market for it. A narrower tyre will, all things else being equal, handle better, however. Although I will admit that a 120/90 do look better from behind than a 4.00

I ordered in a 110/90 and it looks good on the rim. I havent been able to take it for a ride yet.