Winter Cycling - Poll - How many sizes do I go up?

I am looking to obtain a cheaper pair of MTN shoes for those really, really cold rides. Normal summer shoe size is 40. Should I go up to 41 or 43??? The shoe deal I am looking at only currently has odd sizes. I plan on wearing a gore tex sock and some wool socks

Is the shoe in question the same brand as the 40? It matters cause sizing is different brand to brand.

Is the shoe in question the same brand as the 40? It matters cause sizing is different brand to brand.
Yes it is the same brand and my foot is a little wide

Zero, I did that 1 size higher or 1/2 inch so I could wear extra socks but you'll peel off your skin at the ankle/heel area where you rub against the shoes and it's extremely painful. maybe get a bootie or try a snowboard boots.

I am looking to obtain a cheaper pair of MTN shoes for those really, really cold rides. Normal summer shoe size is 40. Should I go up to 41 or 43??? The shoe deal I am looking at only currently has odd sizes. I plan on wearing a gore tex sock and some wool socks

Normal mountain bike shoes won't be well suited to REALLY cold rides. Most are designed to ventilate and keep the foot dry/cool. It likely won't matter how large you go. There are other clipless winter options out there but most involve spending money and there are questions as to how low of temps they can be worn in.

Go with the 43's and get some breathable wind resistant booties to cover them. Unless you need waterproof, then go neoprene. That will be good for pretty cold. You've got to block the wind or the extra insulation won't help you all that much.

Zero, I did that 1 size higher or 1/2 inch so I could wear extra socks but you'll peel off your skin at the ankle/heel area where you rub against the shoes and it's extremely painful. maybe get a bootie or try a snowboard boots.

One of those neoprene ankle wraps will fix that, basically you add a bit more padding to the region.

On my Answer Kashmir I went up from a 43 to a 45 and haven't had any issues. I'm running two pairs of woolies.

Normal mountain bike shoes won't be well suited to REALLY cold rides. Most are designed to ventilate and keep the foot dry/cool. It likely won't matter how large you go. There are other clipless winter options out there but most involve spending money and there are questions as to how low of temps they can be worn in.

No they aren't made for really cold rides but that's why you use a shoe cover over them when the temperature gets to xx degrees. What that temperature is depends on the individual. For me it start around 40 F. I know people who can go much lower and others who have to cover their feet at much higher temperatures.

For covers, just go with the neoprene, Skuda25. They don't breathe but they do insulate. Your feet get a little sweaty but just don't think about it. For size, I go at least one size larger and then use a thick sock.