Why are 1.5" steerer tubes better?

ride_whenever

As above? Why are they better, I can undestand that you cna get more bearings into the tube, but surely a 1.125" steerer in a 1.5" headtube would allow for more bigger bearings which would be better. So are 1.5" steerers inherintly stronger?

jammieeeee

Its all about stiffness, there is much less flex with a 1.5 headtube

dave_hill

The larger the diameter of a tube, the proportionately thinner you can make the wall for a given stiffness

Example - a piece of steel tube 30mm in diameter with a 1mm wall thickness will be stiffer both laterally (resitant to bending) and torsionally (resistant to twisting) than a piece 20mm in diameter, again with a 1mm wall thickness.

The bearing thing is a bit subjective. My Giant has a 1 1/8" steerer, but a 50mm integral headset - 1.5" is only 38,1mm !

As Jamieeee says, the object of the exercise with a 1.5" steerer is to increase rigidity, not to prolong bearing life although of course a 1.5" steerer requires a special oversized headset.

ride_whenever

But how much flex do you get through a steerer? Compared to say, through the wheels etc.

dennisn

Then again it could be manufacturers just trying to sell new stuff by telling you
what a fantastic advantage you will have over all the other riders. I notice that jammieeee says there is "much less flex" in the 1.5 headtube.
I'm curious as to how he measured this "headtube flex" and what the actual readings
were from whatever instruments he used in his testing or is he just repeating hype he
read in some bike magazine or heard from a friend..

Dennis Noward

supersonic

Its the flex in the fork steerer - and this can be measured. 1.5 steerers are stiffer, lighter and stronger. In longer travel forks, where fore aft flex is more noticable, the oversized steerer is a good idea. Simple physics of oversizing tubes - we do it with aluminium frames.

nicklouse

ride_whenever wrote:

As above? Why are they better, I can undestand that you cna get more bearings into the tube, but surely a 1.125" steerer in a 1.5" headtube would allow for more bigger bearings which would be better. So are 1.5" steerers inherintly stronger?

you are confusing two things.

1.5 steerer strength and headset set strength. And then add the weight issue....

prophet_1000

They must be better, Cannondale fit them to their frames and I have a Dale which is the best bike on this forum

He waits for the replies

prophet_1000

As all above, plus there is a larger weld area for the top and down tubes to weld to with a bigger head tube

dave_s

it depends on the frame for instance if you look at a Mythic Scirocco or Mythic Morphine frame, the headtube is 1 1/8" but is immensely built and reinforced with alot more wall thickness than alot of other frames with that size headtube.

1.5" headtubes will be strong although you're more limited with fork choices.
You can get a Hope Stepdown headset or adjuster cups to allow you to run normal forks although some would say it defeats the object slightly.

Personally I don't think you need much more headtube strength on Mythic Morphine unless you're jumping off cliffs