I am an ex-shoe salesman & actually sent from Cdn to a special training for people with feet problems in Chicago USA.
Also in our sport shop we fitted Wardens from Banff & Jasper Alberta National Park here in Cdn with not only climbing boots, but ski boots. Same with special trained RCMP constables from all over B.C. & Alberta when it come to rescue work, climbing & skiing. Meaning climbing & ski boots & other products. Believe me the Wardens & RCMP had BIG feet with 15.5 being a few of them.
Also the above often had to be in said footwear for a week plus & mountaineering requires a lot of tricky footwork.
Problem with m/c boots is that in so many cases it is hard to find anything over 13 & yes we have riders crying out for size 15. The other factor is WIDTH & if you have something like an EEEE in width & you should be with a size D which is even narrower then you usually end up with a size or two shorter, twisting the foot, so the foot will not flop around inside. Many m/c boot people do NOT say the width.
Personally if I wanted a proper fit of a top grade oxfor like Dack, Hart, or Florsheim with size 10.5 & C width these & good other makes would fit with perfection. Still with a climbing boot, ski boot, or such & the fact I will be wearing a heavy sock or a light sock & a heavier one-------to absorb the moisture from the foot & cushion the strain of walking in not normal conditions which also jives with m/cing THAT is when I go for a size 11 in length & D width.
So I use a Danner 'Fort Lewis' boot that has been purchased for military use even in France. Try www.danner.com
if you want to look at what they offer.
I have had mine since around 13 or 14 yrs & they still feel as if I was in my slippers but lots of strength, warm in cold weather & waterproof if you treat them properly as I do then some people have assumed they were probably new said year they looked at them.
True they will NOT save the twist of the ankle & though I have twisted my ankle to even breaking one in 59 yrs of riding which includes 42 yrs of competition. Not with the said Danner boot.
I have purchased some boots from Europe for competition to find the partial steel shank was only a bit of wood & broke when I stood on the footrests during MXing & another pair that also gave out when incompetition in Observed Trials. Along with some that were to large in width & so way to sloppy. Said Danner one could use for a week of walking all forms of terrain.
Of interest they advertised them in SOF magazine as no need to be broken in, no sore spots, no blisters & waterproof. So one of the top men in SOF purchased a pair & after a 5 day of testing them in pretty well any thing including a bit of footwork in the Mtns, streams, & glaciers. Said they were 100% correct in what they claimed. Reason I bought my pair & again they were true.
Remember so many do NOT need a road racing boot & in so many cases shops are selling pull on boots for riding. So take a look at Danner & also give some thought for good hunting boots & believe me hunting boots are put to the test.
Think of what I ride & possibly my Yamaha YZF600r, Honda 929 & 954 might be a bit more then what you ride. By the time you start to aim at tough riding on bikes like I ride I feel that by this time the m/c boot people will have vastly improved their boots & sizes. After all they have improved a lot over the past few yrs & in the late 70s I had to buy from Europe as nothing in the m/c shops other then pull-on boots like Wellingtons or cheap copies of Engineers boots.