KZ750 Tire sizes

This may or may not have been beat to death, but I'm wondering what tire sizes you guys have had good experience with.

The original size for my bike was
3.25 x 19 front
4.00 x 18 rear

The PO put 110/90 x 19 on the front, and 120/90 x 18 on the rear. The front tire he had to adjust the front fender for it to fit (it rubbed a tad prior to him fiddling with it).

Any concerns with those tire sizes? From the charts I've seen, it looks like the front should be 100/90 or 110/80, and the rear is probably fine. Any handling characteristic differences that you guys have noticed between sizes? I've only ever had manufacturer recommended sizes on my bikes.

I'd put a 100/90 19 on the front. 120/90 18 on the rear is fine. 110 is too narrow and 130 does not give any advantage because the narrow rim deforms the tire's cross section so there's no more contact patch than with the 120 (I used 130s for years on my KZ650 and switched to 120). I used Michelins and Dunlops before but now run V-rated Pirelli Sport Demons on mine and I like them a bunch! Ed

650ed wrote: I'd put a 100/90 19 on the front. 120/90 18 on the rear is fine. 110 is too narrow and 130 does not give any advantage because the narrow rim deforms the tire's cross section so there's no more contact patch than with the 120 (I used 130s for years on my KZ650 and switched to 120). I used Michelins and Dunlops before but now run V-rated Pirelli Sport Demons on mine and I like them a bunch! Ed

On the front, is there a particular handling issue you think a 110/90 would cause? It seems to handle fine and have quick handling. Granted, I've only had her up to 60mph so far. A 100 would make the tire narrower, correct? Wouldn't that just make it more twitchy?

i run a 140 on the back and a 100 on the front on stock rims

gengomerpyle wrote: i run a 140 on the back and a 100 on the front on stock rims

I won't try to convince you otherwise if you're doing it, but 140 is too wide to run on a 2.15 x 18 rim without seriously squeezing in the bead and deforming the tread cross section. Maybe check your wheel to see what size is cast into it, it's possible that it is a little wider than the older KZ650/750 rims. Ed

DivideOverflow wrote:

650ed wrote: I'd put a 100/90 19 on the front. 120/90 18 on the rear is fine. 110 is too narrow and 130 does not give any advantage because the narrow rim deforms the tire's cross section so there's no more contact patch than with the 120 (I used 130s for years on my KZ650 and switched to 120). I used Michelins and Dunlops before but now run V-rated Pirelli Sport Demons on mine and I like them a bunch! Ed

On the front, is there a particular handling issue you think a 110/90 would cause? It seems to handle fine and have quick handling. Granted, I've only had her up to 60mph so far. A 100 would make the tire narrower, correct? Wouldn't that just make it more twitchy?

100 will make the handling better. Assuming the rest of the bike is working properly it will not be twitchy. I have run my bike up to an indicated 120 mph many times and it is as steady as sitting at a desk (but there's a lot more wind :laugh: ). Ed

Take a look at the fitment guide:

www.dunlopmotorcycle.com/fitmentguide.asp

it could be a little wider im not sure, the tire was on the bike when i bought it last year.

650ed wrote:

gengomerpyle wrote: i run a 140 on the back and a 100 on the front on stock rims

I won't try to convince you otherwise if you're doing it, but 140 is too wide to run on a 2.15 x 18 rim without seriously squeezing in the bead and deforming the tread cross section. Maybe check your wheel to see what size is cast into it, it's possible that it is a little wider than the older KZ650/750 rims. Ed

DivideOverflow wrote:

650ed wrote: I'd put a 100/90 19 on the front. 120/90 18 on the rear is fine. 110 is too narrow and 130 does not give any advantage because the narrow rim deforms the tire's cross section so there's no more contact patch than with the 120 (I used 130s for years on my KZ650 and switched to 120). I used Michelins and Dunlops before but now run V-rated Pirelli Sport Demons on mine and I like them a bunch! Ed

On the front, is there a particular handling issue you think a 110/90 would cause?

Yeah, on mine the thing dragged the front fender when I got up to 50 mph.

I run 110-90-18 on the back, 100-90-19 on the front. The rear looks a shade small so you can go up to 120-90-18.

DivideOverflow wrote:

650ed wrote: I'd put a 100/90 19 on the front. 120/90 18 on the rear is fine. 110 is too narrow and 130 does not give any advantage because the narrow rim deforms the tire's cross section so there's no more contact patch than with the 120 (I used 130s for years on my KZ650 and switched to 120). I used Michelins and Dunlops before but now run V-rated Pirelli Sport Demons on mine and I like them a bunch! Ed

On the front, is there a particular handling issue you think a 110/90 would cause? It seems to handle fine and have quick handling. Granted, I've only had her up to 60mph so far. A 100 would make the tire narrower, correct? Wouldn't that just make it more twitchy?

The idea is to get the tire width that most closely matches the width the rim was designed for. That gives you the most optimal tread profile.

bountyhunter wrote:

DivideOverflow wrote:

650ed wrote: I'd put a 100/90 19 on the front. 120/90 18 on the rear is fine. 110 is too narrow and 130 does not give any advantage because the narrow rim deforms the tire's cross section so there's no more contact patch than with the 120 (I used 130s for years on my KZ650 and switched to 120). I used Michelins and Dunlops before but now run V-rated Pirelli Sport Demons on mine and I like them a bunch! Ed

On the front, is there a particular handling issue you think a 110/90 would cause?

Yeah, on mine the thing dragged the front fender when I got up to 50 mph.

I run 110-90-18 on the back, 100-90-19 on the front. The rear looks a shade small so you can go up to 120-90-18.

Did you drag the front fender trying a 110/90? Or a 100/90?

The 100/90 19 does not interfere with the fender at any speed. Ed