Tire Size (not rim): Is Bigger Better????

10 replies to this topic
  • thecirque

Posted August 02, 2004 - 06:02 PM


I'm putting some new MT-21's on my trusty steed. The tire size I'm replacing is a 110/100-18. Pirelli doesn't make this exact size. Do I settle for a 120/90-18? 130/90-18? Is bigger always better(as long as it fits) or is that just the testosterone talking?

  • smashinz2002

Posted August 02, 2004 - 06:32 PM


Bigger is not better, the stock size is good, and already pretty meaty. Bigger rear tire will drag the mud flap even worse, and possibly the swingarm too, and change the handling negatively.


Posted August 02, 2004 - 07:46 PM


I agree with the previous post. I have the 650L and have tried numerous rear tire sizes. I came back to the 110/100-18. This is a subjective opinion though. There is a reason why there are so many tire size selections. I did not have any problems with the 120 tires fitting FWIW. I just get good strait line traction with the 110 and good corner traction (when throttle finesse is applied) The closer for me was when I dug through some old dirt mags and checked Scott Summers specs on his race bike (circa 95' or 96' I think) and he also ran 110/100 on his XR 600. :thumbsup:

  • Dutch

Posted August 03, 2004 - 04:22 AM


I've run that tire on my "Betty" and the 140 rear works great.
If I was putting them on "Ronnie" it would be the 120.

  • SaltyWalrus

Posted August 03, 2004 - 07:02 AM


I ran the MT-21 on my 650R and the 140 fit fine without eating anything. Worked ok in dirt and tar. Just doesn't like mud.

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  • BWB63

Posted August 03, 2004 - 08:10 AM


The Pirelli MT21 140/80 is better in the sand and loose stuff. As the ground gets harder you need the tire to be thinner to dig down. The 130/90 was a good coise for all around use. So, it depends on what your using the tire for.

  • qadsan

Posted August 03, 2004 - 01:12 PM


I'm putting some new MT-21's on my trusty steed.

I hope you didn't get those tires at Craparral :thumbsup:

OK, I seen your earlier post. I haven't had the best experiences dealing with them either and spend my money elsewhere, but its fun to window shop there if you get the chance.

  • mikekay

Posted August 03, 2004 - 01:55 PM


For sure the tire size issue can be looked at different ways-

---there is traction--and different tire sizes will deliver different traction in different types of ground. Thats tread pattern, rubber compound, footprint.

---there is handling--and different tire sizes will contirbute differently to handling. Unsprung weight, side wall height, footprint width, etc. all are changed with larger tires--in some ways its better, in other ways with adverse results. Dont forget too the bike handles a lot better with the rear tire as far forward as possible. To me thats a big problem with the 130's and 140's. The wheelbase is longer--affecting turning, etc.

---there is wear including chunking-in general bigger knobs tend to chunk easier.

---there is cost

---there is ease of mounting--both initial fit (clearence)and trail side fixability.

Are bigger tires better? In sand dunes and swamps probably yes. On hard surfaces probably not. Ask any Harley dude with a huge 280 rear and a skinny little front tire. Overall -- its really hard to say one way or another.
I think its interesting that Team Honda races baja with the 2.15 rim and with the 120 rear. That allows a taller, deeper footprint than say a 130 rear with a 2.5 rear rim. It would be nice to know what Scott Summers ran in the muddy mid west gunk. Smaller also means less unsprung weight, less gyroscopic forces, a tighter footprint vs. running the larger tire.

Bigger is better? I dunno.

  • BWB63

Posted August 03, 2004 - 02:37 PM


With the MT-21 it's a good tire for the guy that runs the freeway and the dirt. I think it's better then the 606. The bigger tire makes up for what it lacks in traction. 120-130-and 140 are all about the same hight. A kenda 771 120/100 is 115mm tall on the rim, should be 120mm a Pirelli 140/80 should be 112mm from the rim it's 95mm tall. The terra flex is a 140/80 and is 118 from the rim. The tires are all different width also. The mt21 140/80 ready to ride on the rim is right at 130mm not 140 and it's so round that it's hard to get the side knobs to bite on any thing hard. The Tera Flex is 146mm wide. The Michelin Baja 140/80 is 138mm wide 102mm tall. So, the numbers are miss leading. I have a bunch of numbers on the real numbers and there are 110/100's that are just as tall and close to just as wide as the MT-21 130/90 and just as tall as the 140.

  • mikekay

Posted August 03, 2004 - 03:29 PM


Yeah for sure the numbers are all over the place.
In general the larger tires need the larger 2.5 rim to get within spec. Profile changes considerably when ya go from 2.15 to 2.5
I still cant figure out which size i prefer--but i lean toward the 2.15 with 120 tires for Baja.

Your right about the Michelin Desert having a very low profile. I have always assumed that is to prevent chunking, but not sure.

  • BWB63

Posted August 03, 2004 - 06:56 PM


I was going to go with the 2.5 when I got the Excels but, at the last minute I stayed with the 2.15. It depends on the riding I am doing on the width of tire I go with. I use the 140 for mostly sand or for a duel sport tire.

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