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XR250r Tire Sizing

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I have an 2002 xr250r with numerous free to inexpensive mods with great power output to the rear wheel. However, traction seems to have become a problem. Perhaps it is the stock tire wear. Approximately 200 miles old? Anyway, does anyone know if the rear tire size is negotiable or if I should maintain the current sizing? I was considering increasing the section width from 100 to 110 or 120. All input is appreciated. Where is a good place to buy tires online?

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The Pirelli MT16 110 x 100 x 18 provides great traction for the XR2.5, it wears great also.

The 120 x 100 x 18 is too much for the XR2.5. We run that tire on our XR4.

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I just put a set of Maxxis ITs on my 250 and had the same questions as you do now. The guy at the local shop seemed to really know his stuff and said to stay with the 100x100 because of the narrow rim on the XR. The sidewalls of a wider tire on the 1.85x18 rim won't work properly, because, it would allow the tire to roll to the side in turns. If you're interested in the Maxxis SI you may want to wait until next month when the rear is suppose to be available. Can't help you with internet sales.

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I think they used the 100 width size to keep cost and claimed weight low...

On '95 and earlier XRs the stock tire was a 110/100X18 IRC VE-33 and it had the same width rim as current models (1.85).

And as a sidenote - it is an old trick to run a narrower rim in muddy conditions. The contact patch changes shape to a greater degree - Grips hard clay and flings the mud off to a greater degrees

I always ran a 130/90X18 Michelin S-12 on the rear of my old '95 XR (michelin tire sizes are measured differently and this is equivalent to a 110 dunlop/bridgestone). I may go with a 120/90X18 first time around to see how it works - the center "drive knob" used to be considerably smaller when stepping down to this size - so I wonder about wear.

-jeff

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I had the same thoughts on the tire weight/cost reasoning on a new bike, but after hearing the sidewall argument it kinda made sense. If the beads of the tire are pulled in towards each other more than they are designed to be it sounds logical that the tire would have more of a tendency to roll on the rim in turns. Given the narrow rim performance "trick" maybe that's a good thing. Could be that the type and make of individual tire could determine if it's an issue or not.

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I think they used the 100 width size to keep cost and claimed weight low...

On '95 and earlier XRs the stock tire was a 110/100X18 IRC VE-33 and it had the same width rim as current models (1.85).

And as a sidenote - it is an old trick to run a narrower rim in muddy conditions. The contact patch changes shape to a greater degree - Grips hard clay and flings the mud off to a greater degrees

I always ran a 130/90X18 Michelin S-12 on the rear of my old '95 XR (michelin tire sizes are measured differently and this is equivalent to a 110 dunlop/bridgestone). I may go with a 120/90X18 first time around to see how it works - the center "drive knob" used to be considerably smaller when stepping down to this size - so I wonder about wear.

-jeff

The S12 110/100-18 equivelent is a 130/80-18. When I started running the S12's I tried the 100/100-18 (120/90-18) but it wore extremely fast. The knob size is much smaller than on the 130/80-18. I've been running the 110/100-18 (130/80-18) ever since and am very happy with it. It does not bit quite as well as the 100/100-18 at slow speed/low rpm's but works better everywhere else.

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knowing what I know now. I have a xr400 used to have a xr250. I would not go too big on the rear tire just becuse I think the xr250 does better with the smaller tire, less weight, you can get more wheel spin when needed, higher rpm's. imo.

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I wouldnt go above a 100 IMO on a stock bike. I'm running a 110/100 and I cant get enough wheelspin when I need it. Once this tire wears out I'm going to a 100.

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I wouldnt go above a 100 IMO on a stock bike. I'm running a 110/100 and I cant get enough wheelspin when I need it. Once this tire wears out I'm going to a 100.
With the S12 on my XR250 I've found that at the lower rpm/speed when I need wheel spin to clean, the 130/80-18 (110) with much larger knobs actually gives a little more wheel spin than the 120/90-18 (100). It is a tradeoff though when I would like the backend to break loose coming out of corners sometimes (brake slide in and throttle slide out sometimes turns into brake slide in and throttle tire grabs oh shit I just shot off the trail scenario. I prefer the extra bite most of the time.

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My problem is keeping the RPMs up while climbing hills. I can chug up slowly, but if I want to charge a hill I have to keep it wound up and the wheel spinning. With this tire I just cant do it in 3rd 90% of the time and 2nd is too low to keep the momentum on big hills.

Let me say though my powerband is quite a bit different from the later bikes. The power doesnt just roll on, but rather has closer to what you'd call a hit.

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My problem is keeping the RPMs up while climbing hills. I can chug up slowly, but if I want to charge a hill I have to keep it wound up and the wheel spinning. With this tire I just cant do it in 3rd 90% of the time and 2nd is too low to keep the momentum on big hills.

Let me say though my powerband is quite a bit different from the later bikes. The power doesnt just roll on, but rather has closer to what you'd call a hit.

What gearing are you running? I've been running 12/50 since not long after I bought my 250 in '03. I decided to try 13/50 this last Saturday (new sprockets and chain so I threw on a new 13t front I had and decided to give it a run). I found that 1st was useless (too high for real slow crawling and too low for actual trail riding), 2nd was too low and 3rd was too high (mostly tight singletrack with lots of hills, roots, etc.) I put the 12t front back on and found that 4th was not much higher than 3rd with the 13t, 3rd was usable from slow to too fast for the conditions most of the time, and 2nd became a usable slower gear. Instead of a constant 2nd/3rd with the 13t I am able to use 2nd/3rd/4th and I even pop into 5th once in a while. I'm not going back. I've seriously considered going to a 13/52 but 12/50 works so well I'm afraid to mess with it. I still only use 6th on open roads and in our area it tops out as fast as I'm wanting to go. Any thoughts?

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I'm running 13/50 now. I'm in 2nd or 3rd for singletrack and 4th on faster stuff. 1st is okay for technical sections though. I'll look into where 3rd will be with a 12/50 compared to where it is now.

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