Specialized Crux: Choosing size

[Daveke]

Hi guys,

I'm about to bite the bullet on a new build being a CX bike.
Decided it has to be the Specialized S Works Crux

I am trying to determine what frame size (and stem length) I need to pick for it, but cant really see what I should do best.
This will be a race-only bike (and maybe some short training rounds) as I have a Cervelo Aspero for longer offroad rides

As a reference; I ride a 2019 Venge (stack 581 and Reach 405) with a 1 cm spacer and a 110mm Stem.

The 56 cm Crux has a stack of 582 and a reach of 388
The 58 cm Crux has a stack of 597 and a reach of 395

Usually I would think, pick the 58 cm, as most of my frames are 58's, pair it with a 100 mm stem and slam the stem.
But: Could I also go for the 56 and put say a 110 mm stem on it, and use like a 1 cm spacer again? Stack and reach-wise it would almost come up the same, and being a race-bike wouldnt you want a smaller frame vs a larger one?

If someone can shed some light, it would be greatly appreciated!

[jmfreeman535]

What's your saddle to bar drop on your venge? If it's pretty aggressive, then I'd say go with the 58 Crux to allow yourself a more up right position for better weight balance/control...long and low is great on the road, but not necessarily the best off it.

[AJS914]

How tall are you? I'm 6 ft. (183cm) and ride a 56cm. From what you describe I'd rather have the 56 with a 1cm spacer. Personally I wouldn't want a slammed 58 if it has to be with a short stem. Here is my 56 with an 11cm stem and a 5mm spacer above and below the stem.



On a 58 I'd have trouble getting my stem low enough.

[Nefarious86]

Bigger frame is less about stem lengths and more about the fundamental geo changes.
7mm less toe overlap with the 58
Trail goes from 65mm to 72mm
Wheelbase changes from 1026mm to 1034mm

58cm Crux 130mm-10° stem slammed with Aeronova handlebar. 105mm drop.
58cm Tarmac with 130mm-17° stem with a 5mm spacer. 115mm drop.

[Daveke]

Sounds logical Nefarious. Assuming that my Cervelo Aspero has a stack and reach of 605 and 406 mm I guess I would go for the 58 and work with a 100mm stem. Thanks for pointing it out with the toe overlap.

[singletracknick]

From the info you provided I'd definitely go for a 58 crux (which is what I ride). As a general rule of thumb I run my cx race bikes about 10mm shorter and taller than my road bikes.

For reference I'm 185cm tall. My road and cx geo is:
Cannondale Supersix reach 393 with 110mm stem, Stack 567 with ~25mm spacers
Crux reach 395 with 90mm stem (I might move to a 100mm stem), stack 582 with ~10-15mm spacer

I think a 56 would end up to short unless you ran a really long stem. I prefer shorter stems to speed up handling.