Michelin AC10 Sizing

After reviewing a number of 10/90 Dual Sport Tires for my 2019 KLX 250, I selected Michelin's AC10. Reviews indicated that it was one of the most aggressive DOT Knobbies in the class and should do the job out in the sandbox.

The best prices that I found on the AC10s was Rocky Mountain ATV. The front was $79.62 and the rear was $77.43.

The tire brand and model decision was one thing. The sizing was another. I went round and round trying to figure out what the spec sizes and OE Stock sizes were to help pick the size I wanted.

For the rear I chose the AC10  110/100-18. The OE Stock Dunlop 605 was actually measured to 120mm wide and I was expecting the rear AC10 to come in at the actual 110mm stated witdth. It didn't. It's actually 130mm wide and the sidewall (from the floor to the bead) is 100mm. In my simple mind, this stated/represented 110/100-18 tire is actually a 130/80-18. Also, while the 130mm measurement is the widest point on the tire, I can not find any measurement that equals or is close to 110mm.

For the front I chose the AC10 80/100-21. The OE Stock Dunlop 605 was actually measured to 85mm wide with an 80mm sidewall. That's pretty close to 80/100-21...close enough. The front AC10 came in at the exact same measurements as the OE Stocker.

So....

My real issue is that I wanted a rear tire 10mm narrower than the stock and got a rear tire 10mm wider. That's a bummer, but it will fit (the clearance was 163mm) and I'll be burning it out in 2,000 miles anyway. So I'm not planning to return it.

For those that are using "real" numbers for their tire selection:

AC10 110/100-18

• True Width=130mm
• True Sidewall Height=100mm

AC10 100/100-18*

• True Width=123mm
• True Sidewall Height=100mm

AC10 80/100-21

• True Width=85mm
• True Sidewall Height=80mm

* I subsequently found this measurement done by a member in the KLX250 Forum. So even that tire size only gets me back to the OE Stock size when I'm trying to get something 10mm narrower.

Honestly, I really just want to ride nasty dirt roads and trails and mud bogs and sand pits. All this confusion over tire sizing seems so unnecessary. If an f'ing tire is 130mm wide at its widest point then why don't they just f'ing say that.


Update....

I've now spooned the AC10s on and reinstalled the wheels. I have sufficient clearance on the 2019 KLX250, except for some possible issues with the mud guard in the very front of the swingarm (the guard that protects the spring). I need to get it laden and rolling to look at that, as it's not hitting in an unladen state...just close.

So, I had some time to lob a call into Michelin to ask about the sizing and find out what I was missing, if anything. Essentially, what I was told was that the actual width of the tires is provided in the Company's Catalog and width is provided in two different ways...Static and In-Use. Static is mounted and aired up. In-use is that plus installed and heated up from road use.

I was linked to the catalog and here's a screen shot for the AC10 widths:

These two new measurements for my 110/100-18 AC10 are, plus my measurements are:

Static Width (Catalog) 109 mm

In-Use Width (Catalog) 120 mm

Widest Point of Tread (mounted and aired) 130 mm

Sidewall Width (mounted and aired) 110 mm

True Sidewall Height (mounted and aired) 115 mm*

* The True Sidewall Height (and all measurements) in the original post above was measured unmounted. Mounting and airing up the tire was the cause of the increase.

I suppose that it's possible that the Michelin width numbers embossed on the tire are that of the tire mounted and aired up...even though their website says that width measurements are at the widest point. Moving on...