Carbon wheels on Giant Defy Advanced Pro 1
 

I was in a bike shop looking at this bike when I casually asked if I could put larger tyres than the 25s on these wheels. Despite there being plenty of room around the fork, the salesman said he advised against it. He the proceeded to lean the bike a little and exert some downward pressure and the wheel deflected to the point it was almost touching the fork. Is this normal? Is this even a valid simulation? I wasn't so keen on the carbon wheels, and now I'm even less keen.

Well, unless they changed the forks dramatically since last year.... I run 28s on my Pro 0...no problem. The factory 25s that were on it originally were actually quite comfortable for riding; just had no longevity....

BTW... why not the carbon wheels? Takes a LOT of rotating mass off of the bike...

I have a Defy AP 1 on order and should have my hands on it in a week or two.

The carbon wheels was one of the primary reasons I held out for the '17 instead of going for a leftover '16.

As to size I like the room and assumed it could take much bigger than 25's. I have 25's on my current ride and like them. I'll decide at the time but there's a good chance I'd put 28's on the Defy when the 25's wear out.

Thanks for the reply. There was plenty of room at the forks. I thought there would be no issue but what the guy in the shop said surprised me so I thought I'd question it on the forum.
As for my doubts. I was only worried from a durability standpoint. Sounds like you are very happy with them.
I'm still mulling over a few choices, the others having a little more clearance again and more suited to doing some gravel should I want to and all come with alloy rims. Should I decide that capability is less important, then the Giant looks like a really good value proposition.

As you saw, carbon rims are very stiff and therefore do not deflect at the contact point. Instead the spokes give and the whole wheel deflects. This is a different behavior from a trad wheel. The slight downside is that, going hard out of the saddle and rocking the bike, there will be some rear wheel deflection which can cause unexpected tire rub. Not easy to predict. Try it and see. I have friends who do long stretches of gravel on carbon bikes with 25s.