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Wallonthefloor 05-04-18 12:13 AM

50 cm sizing up right
I have found a bike that has 50cm from the bottom bracket to the top of the seat tube, what would be the appropriate rider height? I hear when people say they buy a 50cm bike they are talking about the top tube length or do they mean the seat tube also..?

Brian25 05-06-18 05:49 PM

5o cm bike size is usually the seat tube length. With a lot of the newer road bikes with the slanted top tubes it gets a little complicated. The have this sizing called virtual sizing where the claim the size by where the top tube would be on a straight across plane from the top of the head tube. So, when you ask what rider size for a 50 cm seat tube, it is going to depend on if it has a flat top tube or slanted. There are other considerations with frame sizing such as top tube length and head tube size. The headtube size has to do with how upright you want to be.

Wallonthefloor 05-07-18 10:54 PM

I'm so confused because I just noticed my bikes are all slightly different sizes. The biggest bike has had a saddle that was too high for at least 6 months (oops), Ive been feeling a lot of pain since and I think I just dialed it in right today.. breaking the bolt first and had to go to the lbs to get a replacement for the seat post. Now I'm not sure what size I should be riding, as we are all different and I started with a 2008 Giant "medium" FCR, and then a Giant Bowery track frame and thats where the confusion starts as Giant frames are really sloping unlike most other bikes. The Giant Bowery measures as 50cm from the bottom bracket to the seatpost clamp and it is extremely comfortable for me with low bullhorns and fizik saddle, although it has significantly been worn down on the nose. My other bike set beside it also with 700x23 wheels is a 2014 KHS Flite 100 and it has a curvy seat tube which is slighly harder to measure, I gather 54cm. The Giant bicylce's saddle comes up only to the height rails of the saddle on this one. Lastly here to measure is 55cm for my All City Big Block singlespeed, a slightly taller looking bike.. but as the bike shop sold it to me "all city frames are generally small for their size" So they are all very different but 100% rideable for me, does that mean that not one is the wrong size? Posted in triathalon because I just ordered a 50cm Giant triathalon bike that looks like my Giant track bike :D (thats the 2008 Giant Trinity)

Wallonthefloor 05-10-18 11:43 PM
So as I can tell its a compact design so the numbers might not add up, I went with a 50 not a 55.5

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