Old 01-25-20, 07:53 AM
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Originally Posted by dsaul View Post
As someone who builds steel gravel bike frames as a hobby, I can tell you that anything shorter than 425mm is very difficult to achieve and still have clearance for wide tires and a road crankset. At less than 425mm, there is also the possibility of the tire contacting the seat tube with a 73 degree seat tube angle and a large tire like a 700x47. A curved seat tube can solve the seat tube contact issue, but the further forward you push the tire, the less room there is between the tire and the chainrings. Titanium adds to the problem by requiring larger diameter chainstays that don't dimple easily for tire clearance.

I normally do 425mm on my frames. I go to 430mm for a larger rider that requires a slacker seat tube angle. On 650b frames I usually do 420mm stays.
thank you very much for your answer. If you don't mind I have a few more questions to you:
1. How would you rate the compliance decrease between 430 and 420 mm chainstay of a steel frame? The common notion is that the longer the chainstay the more movement it can provide so shorter, at least in theory, should also mean less comfortable, yes?
2. Why there is so little steel bikes with the seat stays connected somewhere in the middle of the seat tube (Marin Nicasio Ridge is one of the rare examples of that approach)? When carbon is considered, this lower cross-section point is considered as more comfortable than connecting seat stays with the seat tube at the top tube level.
3. Do you use a bended seat stays (like Litespeed Ultimate gravel bike has) for increased rear-end comfort or this is just a gimmick in your opinion?
4. What do you do to increase the stiffness at the bottom bracket area? My steel Jamis Renegade Exploit is very comfy but also flexes a lot when pedaling hard. Is it possible to get a comfy steel bike that will be also very power efficient?
5. Do you use different seat post diameters (for example 27,2 and 30,9) and if so, how would you rate the compliance decrease when going from 27,2 to a wider seat tube diameter?

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