Kolchek

I'm looking at buying some Michelin Pilot Sport tyres online & I was wondering if anyone knows how accurately Michelin label their tyre sizes. I bought a pair of 32mm Continental Top Contacts a while ago & when mounted they were waaay narrower than the 32mm Bontrager Race-Lites they were supposed to replace.

The Race-lites measure exactly 32mm mounted. The Pilot Sports come in 28, 32 & 35 apparently.

Thanks.

Retro Grouch 

Depends on your rims. If you install that same tire onto a wider or narrower rim, you'll get a different width measurement.

FBinNY 

+1 Different manufacturers use different rim widths in determining their nominal widths, so there's no way to predict the true width (except with tubulars).

Then there's also a bit of rounding when converting true size to nominal size. No one wants to pioneer selling 24mm, 26mm, 27mm or 29mm tires so they tend to round to the nearest 1/8" (3mm or so) sticking with the common nominal sizes. One company's 28mm might really be 27mm while an other's might be 29mm.

Tire sizing is like shoe sizing, it's a good, but rough guide, but you never know until you try them on.

gyozadude

There is an ISO standard for tire widths, and it is based on standards for measurement such as ratios of rim inner width to ISO tire width. This assures you that for most rim/tire applications, if you follow the ISO width, you'll be close. For example, if a tire maker states they have ISO 32x622 size, then it's for a 700C wheel and the tire width was measure for a rim that was something over 16mm ISO (inner) width, probably more like 20mm. It's some ratio between 1.x - 2.0 for tire width to rim width. Can't remember off the top of my head what that ratio was, but it assures the end users and buyers of the actual profile of the tire. Maybe Sheldon Brown has some tips on tire sizing and measurement.

I haven't ridden Conti's in a long time. I don't know if they're still advertising 32C tires that run narrow by 5mm. But in the late 80's and early 90's, every maker practically did advertise tires that ran too narrow in reality - and that was to sell lighter tires than a competitor who might be honestly advertising the true width. I do recall that Michelin has been pretty good about honest sizing. And recent 32x622 for my 700c ran 32 1/2 mm wide on an old Mavic-MA40. Not sure if this is true of all their tires and can't remember the model name. But that's good enough for me.

Kolchek

The Race-lites are labelled 32 & measure exactly 32 mounted on my rims so I thought I had a good generic starting point. Oh well, I'll take an "edukaterd" guess.

Thanks everyone.