General: help with sizing of SIDI MTB clipless shoes

This is a tough one. I never order shoes from the internet unless I try them first. Go to a high end road or MTB shop and act like your interested. Try some on and leave!

Different brands size differently. And within one brand, road shoes and mountain shoes may size differently as well.

I think part of the problem is that you're using Van's to establish your normal US size. To the best of my knowledge, everything Van's makes fits under the description of what us oldies call "sneakers" - canvas casual shoes that are designed to flex with the motions of the wearer's foot. But cleated bike shoes really aren't like that; their purpose is to hold your foot in the optimum position on the pedal, so your pedaling effort isn't wasted. Flexibility means that you're squandering calories wiggling your feet around, instead of putting the hammer down.

A better shoe for establishing a benchmark size would be a regular leather business shoe: A go-to-a-job-interview laceup. Since these shoes are mostly made overseas, they're often sold with both US and Euro sizing marked. And always try on leather-ish shoes in the afternoon, when your feet have swelled up to their maximum size.

The bigger problem is that every shoe manufacturer has a different idea of what each size is, so the "standard sizes" are only standard in that they're all using Arabic numbers to describe them. On top of that, a lot of the everywhere-else to US conversions are made to some imaginary ideal body/foot size. As with cycling clothes, which are all designed for skinny little Italian guys, cycling shoes tend to run small by US standards. US shoes are typically made on a wider last than most European (i.e., non-UK) shoes, so we Americans often need to size up to squeeze into the silly things, or get wider shoes.

I wear a US 10 (UK 9) in street shoes. I have a pair of old SIDI Dominators (leather, in a sort of medium blue, where the instep side flaps over the outside - Dominator 2?) in a size 44 that fit with breathing room with regular bike socks, and snug with thicko wool socks. That makes sense, since SIDI's conversion has 44 at slightly under US 10. By comparison, I also have a pair of Shimano M152s, also size 44. These are designed on a wider last, have a more generous fit, and are wider in the instep.

I can't get my foot into a SIDI Genius (the high-end road shoe) in a size 44, no matter what time of day or what socks I'm wearing. I own a pair of Genius 4s in 44.5, and I can just barely get into them. My understanding of road fitting vs. mountain fitting is that road shoes are supposed to be as tight as tolerable, so that you don't slide around and get blisters. Mountain shoes assume that you're going to be walking/running, as in cyclocross; accordingly, there needs to be more space to handle a wider range of movement. I suspect that I'd be more comfortable walking around in a pair of 45s (or possibly the wider 44.5 Mega), but walking around isn't what road shoes are for.

I've tried Pearl Izumi mountain shoes in 44, and they're too small to strap up, although they claim about the same conversion as SIDI and Shimano. I'm guessing that I'd have to go to a 45 at minimum, and possibly a 46.

According to SIDI, both road and mountain shoes are available in x.5 sizes throughout their size range. SIDIs are also available in three widths. But it's a safe bet that most retailers only carry whole sizes, since European whole sizes are closer together than US whole sizes; US 8-11 is 4 whole + 3 half-sizes, while the same US 8-11 covers 4 whole + 4 x.5 sizes. Since Euro sizes are between US whole and half-sizes, I suspect a lot of retailers split the difference to save on inventory and storage.

If you have a full-on SIDI dealer in your area, that'll be your best bet to check out a half-size. SIDI has a list of their authorized fit centers and magnet centers, which keep a wider range of stuff in stock.

...from the horse's mouth:

SIDI sizing

Pearl Izumi 2009 sizing

Shimano sizing

When I first started looking for SIDIs (the Dominators came used from eBay, and the Geniuses came used from Craigslist; I'm a cheapskate), I went into an LBS and tried on several pairs of shiny-new shoes, figuring that they'd be tighter and truer to size than used ones. That's when I established that a 44 Dominator fit okay - and they do loosen up a little as you wear them. It took a few experiments to find that 44 Genius didn't fit, and I needed to size up to 44.5/45.

I also got spooked the first time I couldn't get SIDI's cinch strap clasp open, to get out of the shoes; but that's another story...

If I had to do a chart of relative size interpretations, I'd say that Pearl Izumi and Nike tend to run narrower than most. SIDI and Adidas (recently sold to Mavic) are in the middle, and Shimano's standard size seems to be the widest. Fortunately, you and I are in the 'normal dude's feet' size range, so we get the best selection; we just don't get the heavily discounted leftovers that people on the large and small end get.

Assuming my experience is evidence of a general condition, I'd guess that if a 42.5 SIDI road fits, that a 42 SIDI Dominator will be right. If your LBS is ordering it for you, make sure that you won't get hit with a restocking fee if it doesn't fit right - they shouldn't be selling you pricy shoes that don't fit, and 42 is a shoe they'll be able to sell. I'm a little surprised they don't have one already; my LBSes have tons of 42s. If you're ordering it from an online retailer, check into their return policy - any operation that's selling footwear by mail order ought to be willing to take back anything that doesn't fit, especially since you have no way to test them before purchase. Wearing shoes that don't fit well makes your whole universe sad.

Good hunting!

So, didja get the Dominators yet? How do they fit?