I'm test riding (only a short ride) and almost surely buying a new 54" Onix TDF tonight. I currently have a 56" TREK 1500 and an aluminum 54" Fuji Team SL which is very fast and stiff. I'll sell the TREK and keep the Fuji.
I have a couple of questions. 1. How much smoother a ride should I expect with the Onix? 2 I have Bontrager Race Light (1690 grams) wheels on the TREK, are these better than the stock wheels on the TDF?. I'm 5'9" with 30" inseam so I think 54" should be fine.
Any inputs are appreciated

I think, being a 30 in. inseam, you should consider the 51cm. Your LBS should be able to fix the right bike for you . For me, considering the ONIX (I'll buy one at the end of the summer), I'm still hesitating between the 51 and the 54, being 5'9" with a 32 in. inseam.

Good choice I think.

[QUOTE=Rix4all]I think, being a 30 in. inseam, you should consider the 51cm. Your LBS should be able to fix the right bike for you . For me, considering the ONIX (I'll buy one at the end of the summer), I'm still hesitating between the 51 and the 54, being 5'9" with a 32 in. inseam.

Thanks for the advice but I'm pretty sure a 54 is for me. The Onix 54 has an effective top tob tube length of 550. My Fuji is also 550 and my TREK is 562, I'm comfortable on both so I don't see going down to 535 on an Onix 51.

I just bought a 51 Onix 2 weeks ago. I'm 5'-9" with a 30-3/4" inseam. The 51 is plenty long for me. If anything, perhaps it's a bit too long (I was surprised at this). A 48 would have been too small and a 54 way too big. The 51 was really the only size that would work for me. Prior to my Onix, I have been riding a 58 (!) steel-framed Peugeot since 1984 so I'm used to a big bike. I agree with the previous posts. You should at least test ride a 51.

I went from a '04 TREK 1500 to a '07 ONIX TDF and it is definately a stiffer frame and overall a faster bike. I can go faster and be less tired at the end of the day. The wheels on the ONIX are the Equipe and I believe they weight around 1860grams. I like them.

Rix4all, I would say that probably you need the 51" since Orbea sizing is different than other companies and it can be deciving. My TREK 1500 was a 52" and my current Orbea is 48" and it fits me perfectly!