Originally Posted by
Iride01
Anything that tells you to use the rear brake on downhills you need to realize that they aren't telling you to lock up the back wheel. As you go downhill, weight is already shifted off the rear somewhat. Braking shifts that weight off the back wheel even more. So it becomes easier to lock it up. For a while, many mfrs have been putting smaller disc's on the rear and I think that is why. So they won't tend to lock up so easy.
I find that my rear is easier to lock on my road bike (140mm), where on my gravel bikes it requires a lot of deliberate action (160mm). YMMV, but I find the smaller discs have a much narrower modulation threshold. I think the smaller discs are for weight saving, because some people think saving 20 grams (less than 1 oz) matters.