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18in vs 19in rear for mx?

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read a few times that their horrible for mx...was wonderin what some of you guys think about the differences.....i know they used to all be 18 even in professional sx/mx.....my xcf came with an 18 and i immediatly thought of putting a 19 on it, but after riding it for a bit now i actually think it hooks up a little better than a 9 and offers a much plusher ride especially over square edge chop......i dont notice it much in corners maybe a hair more wallowy on lean in but not by much....my black rims also dont seem to get worn from the bead like i used to.......flat loamy corners seem to be easier, more stable and better traction, also pinch flats should be far less often......i am novice level so maybe some of the faults come out with faster riders....thought i would hate it but i actually kinda like it though its prolly a little heavier.......i do occasional gp's so i am sure its a good choice for those and all the worcs guys run em, some of the experts chime in..

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I recall MXAction remarking a few years ago that the 18 was a better choice for most local racers in MX, I think it was a SXF vs XCF 450 or 505 shootout and the XCF won it for MX and all around use for all but pro riders.

I notice differences between my 530EXC and 450SXF but the wheel diameter I doubt I could pin down. My youngest is on a 18 rear on his WR125 and has no issues on MX track or trails. He can't notice a difference either.

I read there is a weight difference but I never actually saw a number put to it with similar tires.

Maybe it was a different mag? I only found this,

http://motocrossactionmag.com/KTM/News/2009-KTM-505XC-Suspension-Settings-Jetting-Specs-L-6395.aspx

and they swapped a 19 on but said the 18 hooked up better in many spots and on a natural terrain MX track isn't much of an issue. SX and big jump tracks they said it mattered more.

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I use to hate 18" tires. I thought they were partially responsible for a bouncy feel on my CR 500s, where the KX 500 with it's 19" felt more planted. I also use to run too much air in my 18"s. I don't know if it's the fact that suspension is better now, fourstrokes are just less bouncy, that I run less air in my 18s now, I'm older and run less M/X, or maybe the tires themselves are better, but now I can't really feel a difference and probably prefer the 18"s. I've really never felt the rolling effect in turns that they said made the 19's better. I have a set of wheels for sand/mud/M/X (19" rear off a 2011 with a soft/Int tires) and the stock wheels for my KTM 505 with a Hard/Int tire for most XC races (ie rocks and roots), practice or dry hard M/X tracks. I think the 18"s work better if there’s any trail junk, and more often than not, those are the tires I ride on now.

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All bikes had 18s in 88 and in 89 the MX bikes came out with 19s. The pros/factories had done tresting in 88 and found about 1/2 sec faster lap times with the 19s. So 1/2 sec a lap adds up, all the amatuers thot they had to be like the pros so marketing made the change. Thats the history of it.

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if your interested I would swap you a 19 from a 09 450sxf if your interested I ride only woods.

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An 18´tire is easier to change. More room for your hands inside it since the outer diam 18 vs 19 is roughly the same. The 18 has higher profile too and thus offers some extra "cushion" but an 18 wheel (with a tire) weighs more than the comparable 19 wheel. Just a remark for those weight conscious... It´s extra un-suspended weight on the outside diam. of the wheel.

Some guys say they get better traction with an 18 since the foot print is supposedly larger. Some say ,like already mentioned , the 18 bounces around more in comparison to 19 incher.

I don´t care since all my wheels are 19´and will stay that way.

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An 18´tire is easier to change. More room for your hands inside it since the outer diam 18 vs 19 is roughly the same. The 18 has higher profile too and thus offers some extra "cushion" but an 18 wheel (with a tire) weighs more than the comparable 19 wheel. Just a remark for those weight conscious... It´s extra un-suspended weight on the outside diam. of the wheel.

Some guys say they get better traction with an 18 since the foot print is supposedly larger. Some say ,like already mentioned , the 18 bounces around more in comparison to 19 incher.

I don´t care since all my wheels are 19´and will stay that way.

yeah, definetly has more cushion.....i dont notice the bouncing around...i am not fast enough to notice........if the pros were only saving a 1/2 sec a lap during their testing to warrant a 19 in than for an average rider it is not an issue...i do notice the traction being better and sweeper corners being much more controlled and the bike stays more planted with less stepping out.......overall i am pretty happy with it and i ride only moto........if my bike came with a 19 than like ville i wouldnt change it but mine came with a 18..........funny how all of us copy what the pro's do and since they dont use em most riders think that it will hurt their times too...it actually might be a better choice for average riders.....also alot of the worcs guys use em and they practice moto, i see em all time at out local tracks and it doesnt seem to effect them, they haul ass.......i also like the fact that it will protect my rim better and reduce flats in my gp's.

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Keep the 18". They ride better and on an unprepared track they have more traction.

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Not sure what it's like where you ride, but the dealers here don't stock a lot of 19'' Enduro tyres or many 18'' MX tyres. Worth considering maybe....

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Not sure what it's like where you ride, but the dealers here don't stock a lot of 19'' Enduro tyres or many 18'' MX tyres. Worth considering maybe....

yeah i hear ya, but i dont care what the dealer stocks, i dont get parts from them and cant remember the last time i was in one for parts.........all the mx tires i use come in a 18in, prolly cause the worcs, gncc, etc guys use em

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