Originally Posted by
Dan333SP
It didn't even occur to me when initially replying that I own a 2013 Madone, I'd assume the frame clearance would be similar to the 2014 5-series. I run 25mm GP5k tires on Ardennes+ rims, the internal rim width is 21mm, and I have clearance for these tires but I don't think 28s would fit.
The 28's won't fit because the Ardennes cause the tires to be way oversized for their advertised width. As I stated above, a 25c GP5K measures out to nearly 29mm on HED Plus rims. A 28c tire on your rim would come out to around 31mm wide. If OP isn't running wide rims, a 28 will fit just fine.