07 WR450 - 140/80 Tire, Rear Sprocket Compensate

I searched the forums for the information I needed in this regard. Now I want to throw out an opinion.

I took my plated 07 WR450 in for its first 20 hour service to check valves, etc. It was also time to put on a new rear tire. The original was already worn out. This bike spits out tires like nothing. It is one powerful machine. I have done all the free mods and added Q4 pipe, baja kit, jetted etc

I had the dealer put on a new Michelen Enduro 140/80 tire. I wanted to experiment vs. stock size. Mainly, I wanted more traction...a little more hook up. I currently run 13X50.

I took the bike out today and hit the technical single track, hills, and rocks in Salt Lake. It is very noticable that with the larger tire, the bike is faster, and I have to go to a lower RPM in the tight stuff, and feather the clutch more. This new tire really hooks up. Now, when I hit the gas from a slow idle in the tough stuff, the front end comes up more (I am sitting more towards/on the tank more!).

I want to keep my RPM's up a little more in the tough stuff. I was thinking of going to 13X52 to compensate for the larger tire. I know I loose a little top end, but frankly that does not matter to me. I am in first quite a bit, and would not mind using 2nd and 3rd more (beside when I am in the more open riding).

What do you think, 52" in the rear? I want to keep the front the same. I think that would make this bike perfect as I love the traction and the way it climbs with the 140/80.

Thanks for your input...good or bad.:crazy:

52 sounds about right imo. However, with a Godzilla size tire like that (I ran once IRC M5B 130) you loose stability on cornering. I hated my 130 on tight trails as the rear was ALL OVER the place. I found that having a "fresh tread" was the best way to deal with nasty hill climbs, rather than oversize tire. Additionally, I noticed that the bike felt more sluggish and that was due to the actual weight of all that rubber in the tire.

BTW: Can you even fit a 140 in a WR without loosing the side knobies due to rubbing on the chain?

13/51 would be less of a jump. You are curently at 13/50 (3.84) and 13/51 would give you 3.92. Once you get to 13/52 (4.00) you will find that it always feels like you are between gears. Good Luck. Man that's alot of rubber!

Thanks for the feedback. I did not think about the chain and side nobs. So far I have not seen any rubbing, but it is too soon to tell.

Now that you mentioned the rear being a little more jumpy, I felt that at times, but I also was able to sail over rocky sections a little easier...it felt like the bikes never sunk into some of the rocky crevices. Again, I have had only one ride. I have also never raced, and am just a weekend amateur on the bike.

You are right, the bike is a bit more sluggish. Along with what you mentioned with more rubber, I think it is also because vs. before, the bike is at lower RPM's at the same speed with the bigger tire (because it is larger). When you throttle, and with more traction, the bike seems to be more jumpy (front end comes up). If I had my RPM's up more at the same speed, the acceleration would have more control (smoother), especially when going up a hill and I am running through slow technical stuff...I feel like it barely has enough RPM and less control.

I will probably try the 51 tooth sprocket (52 might be too big a jump) and ask my technical specialist at the dealer. I can always change stuff back after I wear this rubber. It appears this tire is wearing less than my first tire. The first tire had quite a bit of wear after the first 3 hour ride in the the rocks.

Again, thanks for the opinions. I will keep you posted. One thing for sure, the 07 WR450 is a magnificent beast. It will do anything the rider wants it to do, as long as the rider has the skill to maneveur it (i.e. the only excuse is my riding (or lack of) skill!

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