custom 650b cx for mi'lady (geo help appreciated)

my gf has 48 x 48 650c orlowski as her daily bike. She'd like to have a road /cx bike but somehow always chickens out at the last minute when she plans buying a proper bike

I though that if I give her a frameset we might finally be able to go on proper rides together :-)

what do you guys (and especially gals) think of this?

currently the fork I've specced that with is a typical 395mm a2c 45mm rake aliexpress, but I just noticed that there is also cx forks with 57mm rake, which would be better -> less trail

I think I've got the geometry dialed in pretty much except for fine tuning the steering aspects = minimum required amount of front center to keep the steering lively and ridable

e. v1 and v2 geometrys included

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the spec would be:

44mm headtube
1x11
disc brakes
68mm bsa bb
alu (most likely mielec)
aliexprs carbon fork
650b wheel size

this is her current bike

Interesting project. Not tempted to go back to orlowski for matchy matchy?

Id go 26inch for this really. Will be a lot more in proportion, and tyres/tubes/rims are widely available at every bike shop

the 26" is an interesting option, been thinking about that. Right now the geo as quite on the extreme side as it is being limited by the front-center

Arguably better for touring as shops will definitely carry 26 inch spares but might not carry 650b spares. Would allow a slightly larger headtube too. Not sure what youd go for on forks, is there a mid length china carbon with ~285 a to c? Is that even correct for a rigid 26er?

did some calculations. She hasnt complained about toe overlap with her current

• 650c, 165mm chainset, spd / straps & cages and 537mm front center.
  
  

from this with the magic of mathematics we get:

• With 23mm 650c tyre the distance from bb to tyre is 227mm
  
• my v1 cad drawing of a 650b cx bike leaves us with 236mm
  
  

so maybe that 570mm front - centre isnt set on stone. I should be able to shorten the bike a bit. It still has some unwanted features of mini bike geo'ness.

edit added geo 2.0:

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lines of communication with the polish alu masters are open

they quoted me 240e + 30 shipping

sounds pretty ok to me!

Not tempted to go back to orlowski for matchy matchy?

would be pretty but I'm kind of interested in ordering from mielec for a change. mostly to keep the cost relatively low (as I am paying this myself without her knowledge, xmas present) but also to keep the weight low and frame stiff (although I do not doubt steel wouldnt be stiff enough for a 45kg lady)

I dont know what stem length you have planned for, but what about keeping the front-center distance, steepen the headtube angle ~1 degree (and make top tube/reach slightly longer) and then use a shorter stem.
Gets the trail down a bit (but doesn't change weight on front wheel + reach to bars)?

70-80 perhaps. She havent got a proper road bike or anything but her sister's xs canyon with 80 is a tad bit long (550 stack 368 reach iirc)

I know 71 is quite lazy even for a cross bike (i got 72,5 on my orlowski, which i love)

edit: 71 deg, 45 rake, 41mm (knard) 650b cross tyre gives 68mm trail, which is quite ok for a cross bike. I know the 71/45 combination might seem quite extreme at first but remember that this is 650b bike not 700c (with 700c that would be 75 trail, which would be too lazy)

I know but anything over 57mm is lazy :)

Toe overlap vs trail. I really would not like to make the bike any longer

Yes, well then you can later try the third option you suggested:

also cx forks with 57mm rake,

Yah would solve both things.

custom steel fork from jacek? small bike would already be light enough, go 26inch and have complete freedom over fork rake and length

I am with @Turkish on custom (steel) fork .. my missus is shorter than yours and to make sure there was minimal/no toe overlap Matt played with the HT angle while keeping the WB and trail according to the target.

http://talbotframeworks.co.uk/2016/01/vineetas-custom-prommuter-with-talbot-maximum-gains-fork/

Also kinda want to say 26" the only thing holding back is not many good 'road' wheel options having said that you can get Kojak in 26" they are 460g in 2" with latex tube and right pressure they will fly on road too. Given its disc you can always go 26" later if you want I guess.

You can make 26" road cool on instagram. Poor man's WTB Road Plus ;)

Tiny 26" (all)road bikes are awesome

@Hulsroy and I have been discussing SPG bikes (Short People Geometry) for a while as I am vertically challenged (his way of trying to be polite).
26" is the way to go in combination with a custom steel fork. That means full custom and gives you a frame not currently on the market.
There's no fucking around trying to make compromises with the geometry, wheels are lighter and 2" kojaks will handle all of her road, gravel and touring demands. One tyre to rule them all.
To be honest, Amey's GF bike is a very good example of a bike that is built around wheels that are too big. It would have looked much more balanced and well proportioned with smaller wheels.

Tldr: Smaller wheels, custom fork and steeper HT angle

hmm, rly good points! I am sort of convinced my v2 would turn out to be pretty ok, but I do understand the benefits of 26", as I spent a lot of time convincing her 650c would be the way to go for her single speed.

65-68mm trail (30mm - 42mm tyre), especially in combination with light front end + short stem, aint anything unheard of / unridable in terms of cx/gravel/bikepacking rig.

I'll spend few hours in the bikecad before I wire my hard earned Euros southwards

I agree that it is possible to get a good result, I am just challenging the conventional thinking of always using bigger wheels.

Here's a link to a bike with Short People Geometry.
https://www.lfgss.com/comments/13190411/
650c track bike, very well proportioned. Wouldn't have been if it were 700c :)

I am sort of convinced my v2 would turn out to be pretty ok, but I do understand the benefits of 26", as I spent a lot of time convincing her 650c would be the way to go for her single speed.

Am i crazy or is 26 closer to 650c than 650b? 26 makes allot more sense

26" = 559 mm

+12mm

650c = 571mm

+13mm

650B = 584mm

+38mm

700c/29" = 622mm

26 will still be larger than 650c in this case due to larger tyre sizes

ye of course 650c, especially with 23mm tyres, is a lot smaller in diameter, as 650c in itself is smaller than 650b.

this is her fixed gear

that looks so much more balanced than her previous xs 700c :-)

Any progress on this? :)