Quote:
Originally Posted by Juanro
Outer diameter of the 130/90/15 is about the same of the 130/70/17, perhaphs a couple milimeters of diference. I don't think rear tyre size change made a difference in bike's handling.
On the other hand, a couple members here myself included had in fact changed tyre size, either back with a higher profile, or the front, I have a 19', Spud a 21', and I don't think I noted that much of a change in handling either.
The RX3 was always surpisingly stable, not only for a bike relatively tall, but even in absolute terms.
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Yes, it would be very difficult to equal the RX3's handling potential, even stock, for the same investment in any other bike. When everything is right, it is a very comfortable bike for buzzing the back roads at somewhat sporty velocities. Perhaps a little short suspended for rough offroad, but that isn't why I bought it. I have other bikes more suited to that type of riding. Also, the seat sucks, but the accessory seat is significantly better.
All else being the same, rolling radius of a 130/90-15 isn't much less than a 130/70-17. However, when people change rims, they also usually change tire brands, types, models, etc. It's all those other changes that affect rolling radius that very few riders ever take into account. For instance, I've seen dozens of posts advocating narrower but taller rims and tires for improved handling, but virtually every one includes a significantly more aggressive tread pattern, so how can size differences be tested if other significant factors are not controlled? Very bad science. All else must be the same for a comparison to be valid.
Anywho, I've dealt with several RX3s that had high speed handling issues. A few just needed the tires properly inflated. A couple needed a bit of tightening of the triple tree. A couple needed both. All had stock 17/18 wheels except mine, which is fitted with a 19 on the front. Only a couple still had the OEM tires as several OEM tires were ruined prematurely from bad brake rotors. Mine suffered all three problems. Shame on me.
Replacement tires ranged from classic trials, universal, and rib treads to modern sport, touring, adventure, and knobbies. Tires were NEVER an issue unless worn spots from bad brakes or improperly inflated. What I did learn was the more aggressive the tread, the pickier the front end was about inflation when it came to hard surface/highway riding at speed. A few pounds of rear tire pressure didn't seem to make any difference. Therefore, I'd have to recommend first, check air pressure, second check triple tree tightness, then check tires for uneven wear from warped rotors.
Speaking of 19-inch fronts, I can't find any adventure tires (similar to stock) in 110/90-19. Lots of cruiser and rear knobby treads, but very little in the middle. I'm thinking of Duro's 4.00-19 trials or universal treads (OEM on Urals, so should stay available a while), 6-plies that should easily handle any load tossed on an RX3.
Not much available cheap (I go through lots of tires) in 130/70-17 other than cruiser treads. Tons of good choices in 130/80-17, though. No need to worry about messing with geometry with an 80 cross section rear with a 4.00-19 front, there will be plenty of rake for stability.
130/90-17 sees the Kenda K760 Trak Master II, one of the best ever DOT legal full knobbies that won't get you a ticket from some nasty ol' cop--says "DOT" right on the sidewall. 130 tires are about 5 inches wide, so that 20% difference in cross section will add an inch or so to the rolling radius over stock. Then, knobs are a lot thicker than stock treads, and I have no idea how much difference that will add. A matching front tire on a 19-inch rim would likely make a good companion. Same tire is available in 110/90-19 that might fit between the front forks, and 100/90-19 that will fit for sure, but it is a rear tread pattern that will probably wobble at speed on pavement without the weight of your hand on the bar (doesn't take much).
I've run the K760 rears on the front of other bikes and they never let me down off road. Amazing low traction performance on either end, just don't expect super straight line stability on hard surfaces. Just ignore the wiggles at speed and enjoy the glue in the mud, sand, and snow. Do not grab a hand full of brakes with someone following close behind. A fat K760 on the front makes grown men hitting the brakes in mud, sand, or gravel giggle like little girls. They are that good on the front offroad. If I ever take a RX3 on boonie rides, I'll have the K760s on both ends. I won't even consider any other tires. They are that good off road, and I've run 84mph with them on pavement, they were well behaved, and I still live! When the RX4 is available I'll get one off the first container, and K760s will go on my current RX3, no question.
The Pirelli MT21 is available in 130/90-17, if you want a top-of-the-line European tire with better street manners than the K760. Unfortunately, there is no appropriate size available to match the odd tread pattern on the front. Still a great tire, though.
The Shinko 705 (what I'm running now on the rear) is an adventure tread tire and works pretty well. It is nowhere near the K760 or MT-21 in the dirt, though, but is a very nice tire for paved and dirt roads. If I only rode pavement, I'd shop for real street tires, probably on the sporty side because I tend to go a little faster than legal on back roads.
Hope that helps with your next tire shopping experience.