tire size help

[tpruitt]

I am going to buy a pair of 50/50 tires for my exc The stock wheels are 21x1.6 and 18x2.15. The tires that came on the bike are a 80/100-21 front and a 110/100-18 rear. For the set of tires that i am looking at i can only get a 90/90-21 front and either a 130/80-18 or 120/90-18 for the rear. I dont have a choice on the front tire but which one should i get for the rear? I have read in a few post here that the 130/80 is basically the same thing as a 110/100 is this true?

Thanks

tpruitt

[Ud_Luz]

I assume you're talking about a KTM exc.

If it's a Michelin S or M12, run the 130 on the rear if it's a 125 or 200. You may run the 130 or 140 on the bigger bikes.

[tpruitt]

Yeah i looking at the Mefo and on their site they dont list the 120/80-18 but they list the 120/90-18. The place i was looking at buying them from listed the 120/80-18 so i dont know if they even make a 120/80-18. I have a 450exc.

[Rip Wheeler]

I am going to buy a pair of 50/50 tires for my exc The stock wheels are 21x1.6 and 18x2.15. The tires that came on the bike are a 80/100-21 front and a 110/100-18 rear. For the set of tires that i am looking at i can only get a 90/90-21 front and either a 130/80-18 or 120/90-18 for the rear. I dont have a choice on the front tire but which one should i get for the rear? I have read in a few post here that the 130/80 is basically the same thing as a 110/100 is this true?

Thanks

tpruitt

Here is the deal on tire sizes. First number is width in mm, next is the aspect ratio, ie in percentage and its reffering to the sidewall. So on a 100/100-18, its 100 mm wide, the sidewall is 100% of the width, so its the same ie 100mm high. While an 80 would be 80% of the width. I'd say a 100/100-18, if you replace it with a 110/100-18, you will not only have a tire that is 10% wider, it will be 10% taller, even though, the second number is still a 100, it means 100% of the width. Since the widht is wider, the sidewall is taller now. This can throw off gearing a bit too. While a 130/80-18 is about the same as a 100/100-18, just wider by about 30mm ie the sidewall is narrower. A narrow sidewall has good advantages. Usually, they are stiffer and can be much easier to ride out of the woods on a sidewall thats 80% instead of 100%

Both options you mentioned will replace what you have. The 2 options for the rear is just wider, assuming you have the extra room, it should be a non issue.