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The casing on the Michelin AC-10 100/100-18 is ...drumroll.... 100 mm. Over the knobbies (widest) about 123 mm.
I just took delivery of my 2019 KLX 250 on Wednesday last week and put it into action over the weekend at the Wild Bear Safari in a very "sandy" Ocala National Forest. As is normally the case, here in Florida we have to replace whatever the OE tires on new dirt oriented bikes to something more suitable to deep sand and mud. I normally use Dunlop D606 or MT21, but for the first set on the KLX I decided to give the Michelin AC10s a try. I just couldn't get them in time for the rally. In making my size choice I got a little wrapped up in this whole issue with the AC10. The sizes that I purchased were 80/100-21 and 110/100-18.
As you know, the OE D605s come in what I'll call the old school sizing of 3.00-21 front and 4.60-18 rear. The actual measurements on the widest point of that tread in inches is 3.35" front and 4.69" rear. That equates to 85mm and 119mm, respectively. The sidewall widths are 74mm and 94mm, respectively. The total sidewall (floor to bead) measure 79mm and 102mm, respectively. Using a simple conversion to the closest metric size, those measurements seem to come out to 90/90-21 and 120/90-18.
In the AC10, I chose the 80/90-21 and 110/100-18. I could not find the spec sizes on Michelins website, but they explicitly say that the first number is the width at the widest point. Good enough for me. So, I thought I was getting a narrower front and rear by 10mm each. Nope...ran into the same issue on the rear as was the case of the very dated discussion in this thread. The actual measurements of the 110/100-18 AC10 are 130mm wide and 100mm in total sidewall (floor to bead). It would seem to me that these measurements would make this tire a 130/90-18. The actual measurements of the 80/90-21 are 85mm wide and 80mm total sidewall; close enough as I was trying to get the narrower 80mm width and wound up somewhere in between.
Well, I'm a little bummed about the rear, but it should fit...I measure a 163mm of available clearance for a 100mm total sidewall...and, as was made clear in the reviews of the AC10, I'm prolly going to burn this thing flat by march and need to replace it anyway. So, overall, I guess bringing this old thread back to life is a reminder that this issue is still out there. Also, just for the record, although I took it easy on my new bike, the D605s (clearly a 50/50 dualsport tire) got me through the 180 mile rally fine. I really don't think they're a bad performing tire at all.
Thanks for the definitive dimensional info on the tires.
Did you get into deap sand & how did it do with that?
Maybe you found a hill? ~
The speed needed to be backed down quite a bit to make the D605s work in deep sand, of which there was a lot. That makes it hard to keep up with the pack if you're in a fast group and why I need to move to the sandies. I don't necessarily need to go fast; I just want to keep up. Otherwise the D605s handle sandy surfaces and gravel fairly well.
As hard as it is to find a hill in Flatistan here, there was this ridiculously wicked ditch in the Ocala National Forest (ONF)...but I took the bypass. As you can see, others rolled down there to take a look and made a hasty retreat to the rear. I'm back in ONF with another rally in early January. I would try that with the KLX with the AC10s. My riding partners just may need to come help me drag the bike and my butt out of there.
Thanks,
With all the tires I have tried since getting my 07, none have worked very good in deep sand. I think it is the bike. Right now I'm running Michlen StarCross5 medium and really pleased with the service in rocks & dirt.
I called Michelin. There's no balancing indicator. On the strange sizing, they continued to believe that the width is measured at the widest point, but directed me to their catalog that lists two types of width. Static Width is mounted and aired. In-Use Width is a heated tire from road use. Below is a screen shot of the section of the manual that provides the width for all AC10 sizes.
Screenshot Michelin Catalog
The measurement that I didn't provide in my original post was the sidewall width, because Michelin's website said width was measured at the widest point and that wasn't the widest point. However, the sidewall width, mounted and aired, is 110 mm; pretty close to the static width.
One thing I will add is that I found the AC10s very soft/flexible and super easy to spoon on. Way easier than the D606s that I've been using regularly for a number of years now. Looking forward to doing some trail riding later this week and see how they work in the sandbox.
