Custom geometry advice

AidanR

Hi all,

I was wondering if I could pick brains more experienced than mine to see if a couple of frame geometries seem sensible.

I'm mulling over getting a custom frame for XACD, well 2 actually - one for me and one for the girlfriend. We're both a shade under 5'9", and I've got a shortish body, and she's pretty average for a female.

Her bike is to be a road bike, but with handling more like a sportive or light tourer, or in her words "more like a mountain bike", which I'm taking to mean more stable and neutral than the Saracen Tourmalet she currently rides. It's going to take cantis and 700x32c tires. I appreciate that it's impossible to tell whether it'll fit properly from behind a computer screen, but does this geometry seem sensible:

Effective top tube - 540mm
Seat tube (C-T) - 520mm
Wheel base - 995mm
Chain stay - 430mm
Head tube length - 135mm (non-integrated)
Head tube angle - 72.5deg
Seat tube angle - 72deg
BB drop - 75mm
Fork Offset - 45mm
Trail - 61mm (with 700x32c tyres)
Fork axle-crown - 395mm

My bike is to be a flat barred Rohloff roadie, disc brake with room for the same tyres. I'm going for a livelier ride more akin to the old Trek 5200 I currently ride.

Effective top tube - 585mm
Seat tube (C-T) - 510mm
Wheel base - 1035mm
Chain stay - 420mm
Head tube length - 140mm
Head tube angle - 72.8deg
Seat tube angle - 74deg
BB drop - 72mm
Fork Offset - 45mm
Trail - 59mm (with 700x32c tyres)
Fork axle-crown - 398mm

Any thoughts would be greatly appreciated!

Thanks,

Aidan

Monty Dog

I'd expect your seat tube angle to be always greater or equal to the headtube angle - 72 degrees is pretty slack for a frame of that size. Rather than experiment, it's probably easiest to base your design on a proven design - particularly of that type and size. Funnily enough just in the process of Xacd to price up a new frame for me too - demountable roadie with Breakaway and BTC style couplings.

AidanR

The reason for the slack angle is it's a women's frame, and I've read that it helps achieve a better saddle position by moving the saddle further behind the BB. I'll take a look at the CAD drawing when it arrives to see if toe overlap will be an issue - I'm assuming that's the main problem or am I missing something else?