Geometry Review- Crooked Aero, the confused road bike

Lets start off by saying this bike a about proving a point to myself. I live in Kansas, that means a few things. First, the wind is unbearable. Second, climbs are long and gradual. Third, our gravel is basically concert with piles of gravel dividing the lanes.

I have thousands of miles of this gravel out my front door. The kicker is that our paved farm roads are also very nice. My road rides are segmented with gravel and my gravel rides are segmented with road.

I currently road ride on a 56ish MM track geo single speed with 30MM tires. I gravel ride on a 57.5MM Salsa Storm Chaser with 42MM tires but have done many miles happily on 38-40MM tires.

This leads me to the point I want to prove- The optimal “Gravel” bike in my area is closer to “Road” or “All Road” than the marketing departments want us to believe.

What I want to improve upon my current situation-

  1. Improved Aerodynamics- the Storm Chaser is a brick in our wind. I have a teardrop Down Tube and Seat Stays and will use on ovalized TT. I also want dropped seat stays because BFS sells a low geo seat tube and I think its cool :rofl:

  2. Improved comfort- The Storm Chaser also rides like a brick when you have small tires on. I have an Enve G series fork to assist on this build. Hopefully steel and carbon are better than Aluminum with a hefty fork. I also am adding 1 degree to STA because I always feel too far behind the pedal axle and I like how offset seat posts feel.

  3. This must be a good enough Road bike to toss on some light wheels and tires and ride with groups when the mountain bike trails are wet.

Anyway here is my rattle cad dimensions Let me know what you think.
-For reference, I am 6’ and have gangly arms but average Torso to leg measurements.

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Two things come to mind:

  1. TT bikes use level top tubes I’m assuming to be more aero. You could consider running a level top tube.
  2. The BB height could be lower. I usually spec a 275mm BB height for gravel bikes unless the customer likes to pedal a lot while cornering. A lower BB makes the rider lower and more aero.

Looks great, when can you build me one? Agree that BB height could be a touch lower, especially if you’re not riding loads of technical stuff (for handling as well as aero).

For improved aero, consider shorter cranks (165mm) as this will also lower your body position relative to BB. Have you had a proper bike fit done with consideration for your aero position? But TBH if you’re happy with your position and just want a slightly more aero bike, then there’s not much to be found by making minor changes to the frame. Clothing and helmet choice will give you far more benefit than a level TT or shorter cranks (and bad choices will take it all away very easily!).

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Brake caliper - SS clearance:

I would watch out for the caliper clearance. When you have a stay that is dropped that much, you need to find a solution to the SS - caliper clearance.

I can only get away with ~57deg of CS-SS angle with a paragon 1.5in dropout:

What dropout are you planning to use?

Aero position:

An aero bike is really only 20% of the total aero drag. The body produces the vast majority of drag. To me, the reach of this bike looks a bit short (we are the same height and saddle height). This may be a carryover from your salsa (which is known to have short reaches).

An aero fit tends to be longer and narrower (lower is not always better). You could consider extending the reach 10mm and using a 40cm wide bar.

Not saying the fit is right or wrong (fit is very individual) but it is something to consider.

Seat tube:


I think you are on the right track of having the SS-ST junction on the thick butt of the tube. However, in my opinion, that seat tube is going to be stiff and heavy. on your design, the 1.2mm section will need to be 200mm long?

Perhaps a reinforcement sleeve on the ST, or consider reducing the SS drop. That will also help mitigate the SS-Caliper interference.

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Now you know why I’m am learning to model a bike :rofl: I am going to make them as low as I can given the caliper interference. I won’t have the actual SS drop until I have the rear end figured out.

I may have missed the overall goal explanation. When I switched from a Kona Rove (small diameter tubes) to the Stormchaser the feeling of the frame in the wind was stark contrast.

I do most of my road riding in the winter so my clothes are a big drag anyway.

What I want to accomplish is a bike that doesn’t feel like the wind is going to blow away from under me.

I like low seat tubes for the ride quality of longer seat post. I was thinking I would cut the upper section as short as possible while placing the SS joint on the thick joint.