Road Bike, Cycling Forums banner
1 - 11 of 11 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 · (Edited)
I'm about to order Roubaix 2017 s-works frameset, and looking to get 54 frame (I usually ride size tt 54 on most of my other bikes). However, after looking closely at the geometry of the latest 2017 roubaix, I noticed some out of place number in geometry table that I want some opinions upon. Please look at my attached file to see what I referred to.


I noticed that the trail length of size 54 is actually look out of place as 61mm on the table -- see (1) in pic. Especially when you compare trail length to the other frame sizes, you can see that all other got trail length number in the order from 59 to 52, directly reverse match to frame size from 49 to 64. The reason could be that you need to dial more ability to turn (less trail length) when frame size getting bigger to retain the same riding characteristic across Roubaix line up.



However, as in this case, the 54 frame size with 61 trail length would actually feel a lot sluggish (or perhaps stable) and would turn a lot slower than any other Roubaix frame with more common 55 or 57 trail length.


It's even more interesting when both 52 and 54 frame size in the geometry table happened to have exact wheel base and head tube angle (number 2 circle on table). Should 54 size get a little bit more wheelbase than 52 to accommodate all other geometry number?

(note: Velodog pointed out later in the thread that I was incorrect on the degree of headtube it is actually half degree different -- I keep my previous incorrect statement here for the sake of discussion.)


So, my theory is that either the published trail length number for 54 size is typo, or somehow specialized frame designer decided to compromise frame design when create Roubaix line up (hectic release schedule could be one). What do your guys think? Btw, the geometry I got is the same as on Specialized web site.
 

Attachments

·
Registered
Joined
·
1,701 Posts
When you say "the geometry I got is the same as on Specialized web site." does that mean you actually measured a bike and confirmed the numbers in the Specialized chart?
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #3 · (Edited)
When you say "the geometry I got is the same as on Specialized web site." does that mean you actually measured a bike and confirmed the numbers in the Specialized chart?
No JSR, I mean that the number in my table (found from BikeRumour article) is the same as currently present on the Specialized web site.

I am thinking about order size 52 and readjust my position with stem instead of getting 54.
 

·
Registered
Joined
·
1,701 Posts
Ok, I get it now.

I suspect the chart is fouled up. I did a quick check of the Diverge chart and the numbers on that frame flow more linearly across the frame sizes. Your LBS might enjoy the opportunity to straighten out the confusion - or not!

As to choosing between 52 and 54, if you're proposing to opt for quicker handling you've just bent whole logic tree on choosing this category of bike.
 

·
Registered
Joined
·
8,791 Posts
Actually the 54's head tube angle is 1/2 degree steeper and the fork has 6mm less rake. Those numbers will lengthen the trail on the 54cm. Here's the link to the calculator.

Bicycle Steering Geometry

Going from a 50mm fork rake to a 44mm fork rake is quite significant. It looks like they changed fork rake from 50 to 44 when they went from the 52 to the 54.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #7 · (Edited)
Ok, I get it now.

I suspect the chart is fouled up. I did a quick check of the Diverge chart and the numbers on that frame flow more linearly across the frame sizes. Your LBS might enjoy the opportunity to straighten out the confusion - or not!
That's my point exactly, I also checked other Spcialized geometry like Tarmac and yes Diverge, and come to the same conclusion as yours. It suppose to be linear across the line up.

JSR said:
As to choosing between 52 and 54, if you're proposing to opt for quicker handling you've just bent whole logic tree on choosing this category of bike.
I actually try to get the handling characteristics of 2017 Roubaix the way It supposed to design for. Adding stem length to 52 would probably put my normal reach back to the way it should be and also add a bit more stability with more weight distribution over the front. Going to 56 would be a bit stretched for me. Since they seem to foul up 54 already, my choice seem to be down to one size.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #8 · (Edited)
Actually the 54's head tube angle is 1/2 degree steeper and the fork has 6mm less rake. Those numbers will lengthen the trail on the 54cm. Here's the link to the calculator.

Bicycle Steering Geometry

Going from a 50mm fork rake to a 44mm fork rake is quite significant. It looks like they changed fork rake from 50 to 44 when they went from the 52 to the 54.
Oh yes, I just look at it again, and I was wrong about the head tube angle. Thanks Velodog. It is actually half degree steeper. The reason could perhaps be that 54 is using the same wheelbase as 52, but lengthen the chain stay and top tube to make it 54?

The result put the constraint on the degree and fork rake number, since they still keep the wheelbase the same as 52. So it does mean the chart wasn't typo error.

Like you said it is significant to the point that in my opinion could perhaps render the bike handling much different than the rest of the line up. But again that is just my opinion, I should try to find the shop with both size that I could demo to see if I would feel it.

On the other note, they might probably need to use 44 fork rake from the manufacturing cost standpoint too? Sourcing fork for using with only one frame size sound costly to me.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #9 ·

·
Registered
Joined
·
6 Posts
Discussion Starter · #11 ·
1 - 11 of 11 Posts
Top