140mm disk on 1" steel fork: strong enough?
Moderator: robbosmans
I'm planning a new custom frameset. Would a straight steel road fork (375mm) with 1" headtube be strong enough to cope with a 140mm disk brake for daily commuting or should I go for 1 1/8" anyway?
And if I ever meet an aardvark, I'm going to step on its damn protruding nasal implement until it couldn't suck up an insect if its life depended on it.
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They say it is strong enough but have not built a 1" disk fork before (only 1 1/8" with curved blades). I just wondered because a straight 1" one aesthetically goes best with the rest of the frame but don't want a bike with a risky fork.
And if I ever meet an aardvark, I'm going to step on its damn protruding nasal implement until it couldn't suck up an insect if its life depended on it.
BTW, it is not some thin walled hi-end steel, just simple entry level to go with a Deda ZeroUno frame. Guess that also makes a difference in this design
And if I ever meet an aardvark, I'm going to step on its damn protruding nasal implement until it couldn't suck up an insect if its life depended on it.
Timo wrote:They say it is strong enough but have not built a 1" disk fork before (only 1 1/8" with curved blades). I just wondered because a straight 1" one aesthetically goes best with the rest of the frame but don't want a bike with a risky fork.
To be blunt: if the guys who are making the damn thing don't even have any real world experience with it what exactly are you expecting from a much of random guys on the interwebs? Who is going to be able to tell you about the characteristics of a fork that doesn't exist yet?
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random guys on the interwebs
Plenty of engineers and frame builders on this forum.
Stems and headsets are not the problem (Syntace F99 with shim and 1" Campagnolo aheadset on all my bikes) and I prefer the sleek looks of a 1" headtube but not at a risk. Like Andrew said: looking for input from engineers, frame builders and other experienced forum members. My frame builder has 69 years of experience (in the family firm that is) so I tend to believe his when he says that strength is not the issue - but want to be absolutely sure
Last edited by Timo on Tue Mar 15, 2016 7:43 pm, edited 1 time in total.
And if I ever meet an aardvark, I'm going to step on its damn protruding nasal implement until it couldn't suck up an insect if its life depended on it.
How could the steerer tube size come into play?
Non-engineer over-simplification:
- Slam on the brakes with disk brake, forces transfer hard to the fork blade.
- Slam on the brakes with rim brake, forces transfer hard to the fork at joint of steerer/blades (brake mount).
From there on... either setup transfer forces as they are going to do, but once those forces head up the steerer, who cares where the brake is mounted?
Are you thinking that you can generate MORE force with the disk brakes than you might with rim? (HINT: you can lock up the tire with either system).
Non-engineer over-simplification:
- Slam on the brakes with disk brake, forces transfer hard to the fork blade.
- Slam on the brakes with rim brake, forces transfer hard to the fork at joint of steerer/blades (brake mount).
From there on... either setup transfer forces as they are going to do, but once those forces head up the steerer, who cares where the brake is mounted?
Are you thinking that you can generate MORE force with the disk brakes than you might with rim? (HINT: you can lock up the tire with either system).
Almost engineer (got 1 year to go) explanation:
Braking generates a force, disc brakes generate this force at a much further distance from the headset than rim brakes do. This force acts over the longer distance, creating a longer lever arm (technical term: moment) and produces a huge force that the headtube/steerer must resist. Stress is defined as force÷area and a 1" headset will have less area to distribute this force over than 1 1/8" so it will see higher stresses. Given that you are using this bike for commuting I'd be inclined to go with 1 1/8" since it will see less stress it is likely to have a longer life.
Braking generates a force, disc brakes generate this force at a much further distance from the headset than rim brakes do. This force acts over the longer distance, creating a longer lever arm (technical term: moment) and produces a huge force that the headtube/steerer must resist. Stress is defined as force÷area and a 1" headset will have less area to distribute this force over than 1 1/8" so it will see higher stresses. Given that you are using this bike for commuting I'd be inclined to go with 1 1/8" since it will see less stress it is likely to have a longer life.
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Persoanlly I would not use a 1" steerer for disc brakes in the short term you will be fine but 5 years down the road? Also 140mm rotor in the front is the other thing I would not do but that is another matter.
mattyNorm wrote:Almost engineer (got 1 year to go) explanation:
Braking generates a force, disc brakes generate this force at a much further distance from the headset than rim brakes do. This force acts over the longer distance, creating a longer lever arm (technical term: moment) and produces a huge force that the headtube/steerer must resist. Stress is defined as force÷area and a 1" headset will have less area to distribute this force over than 1 1/8" so it will see higher stresses. Given that you are using this bike for commuting I'd be inclined to go with 1 1/8" since it will see less stress it is likely to have a longer life.
As above. It's also worth considering that a 1" fork has a (marginally) lower surface area of weld between the steerer and crown, due to the (marginally) lower circumference.
But that's just being pedantic.
Thanks all for your help. I've changed the design to 1 1/8"
And if I ever meet an aardvark, I'm going to step on its damn protruding nasal implement until it couldn't suck up an insect if its life depended on it.
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