By "straight fork" I mean the one with 1 1/8" head tube. The more slack head tube angle is the more stress on the fork. So what is the safe angle when you can still use straight and not tapered fork?
I am asking about steel frame and fork.
asked Jan 4, 2023 at 16:59
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1What kind of riding are you doing?– Paul HCommented Jan 4, 2023 at 20:47
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@PaulH Gravel adventure/touring. There is something around 100kg (me+stuff) on the steel gravel bike, and I ride asphalt, gravel, ground, sand. And more through more potholes that I wish :-) Currently I have handlebar bag and bags on the fork (as the fork is concerned here). In the future it could be more, on front rack. przypadkopis.files.wordpress.com/2022/08/…– greenoldmanCommented Jan 4, 2023 at 20:53
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let's work this backwards -- what head angle do you (want to) have?– Paul HCommented Jan 4, 2023 at 21:09
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@PaulH I am considering going less than 89 which seems like a barrier of this type of bike/riding, slacker head tubes do exist of course but in MTB domain.– greenoldmanCommented Jan 5, 2023 at 5:59
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89º? Surely you mean 69º? Plenty of non-MTB frames with slacker head angles– Paul HCommented Jan 5, 2023 at 15:48
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1 Answer
Safety is not a direct result of a tapered head tube. The head area is so safety critical no reasonable manufacturer would engineer a frame/fork that had an avoidable risk of catastrophic failure. The tapered head tube is stiffer, and spreads loads more, so with less concentrated loads, forks and frames can be built with lighter materials. The crown can be larger and therefore stronger, allowing the likes of downhill forks to move to single crown, where in the past they required a double crown (although this is about stiffness and weight more than safety). Frames and forks using straight steerers are only weaker (or stronger) than frames and forks with tapered steerers because the designer made them that way.
Given you are asking about steel frame and fork, and steels general resilience and strength, any reasonably rideable head tube angle will be perfectly safe on a straight steerer. If you are looking at extreme head tube angles, it might be prudent to check with the fork manufacturer. (It is reasonable to presume the frame builder has built the frame to be safe at the head tube angle.)
