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I have yet to own/work on a bike with a 1.5 headtube. Are all forks still 1 1/8"? Is the idea behind the headtube a larger bearing or to recess the headset cups or both?
 

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marketing

shmokinjoe said:
I have yet to own/work on a bike with a 1.5 headtube. Are all forks still 1 1/8"? Is the idea behind the headtube a larger bearing or to recess the headset cups or both?
fortunately not many are jumping on the badwagon, there is no advantage to use a 1.5" Cannondale has been doing it for ages
 

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So if I buy a bike with a 1.5 I will need a headset that will have a 1 1/8 steerer tube diameter? and If i upgrade to a 1.5 fork then I'll need a different headset, correct?
 

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Davide said:
fortunately not many are jumping on the badwagon, there is no advantage to use a 1.5" Cannondale has been doing it for ages
There is a distinct advantage to using a 1.5" headtube that manufacturers are only recently discovering, but not what you would expect. While the 1.5 steerer was originally marketed to freeriders touting greater strength, it never caught on for that reason. Dirt bikes use 1" steerers, and go 100mph and jump 100" gaps. The steerers are thick, heavy steel.

What engineers have found recently though, most notably at Rockshox, is that for a given tested target stiffness, they can make their products lighter by using a 1.5" steerer. We should not be surprised at this, given that we know how larger diameter thinwall aluminum can be made lighter than smaller diameter tubes with thicker walls. Klein, and ironically Cannondale, first showed us this in frame design many years ago.

As for the 1.5 bandwagon, Fox Racing Shox and Chris King, two of the most conservative companies in the industry, have jumped on due to large OE contracts from Santa Cruz for the pending 1.5 headtube on the Nomad. I think the question of 1.5 headtubes going away is a moot point, now that the all mountain and DH markets are searching for weight reduction. Remember, when riding off-road, light is always right. (moto saying)
 

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shmokinjoe said:
So if I buy a bike with a 1.5 I will need a headset that will have a 1 1/8 steerer tube diameter? and If i upgrade to a 1.5 fork then I'll need a different headset, correct?
Probably depends on the headset. I know with with at least some of the FSA 1.5s you just switch a couple parts and it becomes a 1.5 to 1.125 reducer headset. Nothing needs to be pressed out.

I like the 1.5 because I can run very low stack height with the right setup. I did this on my DH bike using the e13 reducer cups allowing me to steepen the HT angle about 1/2 degree.

I prefer the 1.5 standard on any bike 6" travel and up. I can't see it on XC bikes though.
 

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shmokinjoe said:
I have yet to own/work on a bike with a 1.5 headtube. Are all forks still 1 1/8"? Is the idea behind the headtube a larger bearing or to recess the headset cups or both?
It is not 1.5" headtubes, the fork steer tube is 1.5". This means the frame's HT needs to be larger to fit the larger diameter headset and fork steerer. There are headsets designed for using 1.125" steerer forks in 1.5" frames (along with the spacers others have mentioned.

The 1.5" (one point five) "idea" is have a stronger/lighter/stiffer single crown long travel fork.
 

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shiggy said:
It is not 1.5" headtubes, the fork steer tube is 1.5". This means the frame's HT needs to be larger to fit the larger diameter headset and fork steerer. There are headsets designed for using 1.125" steerer forks in 1.5" frames (along with the spacers others have mentioned.

The 1.5" (one point five) "idea" is have a stronger/lighter/stiffer single crown long travel fork.
Shiggy's right..Although in the Cdale case my steerer tube is 1.562" in diameter, and I think 1point5 on regular bikes IS 1.500"....
The OD of my HeadTUBE (in case your wondering) is 2.215" :eek:
CDT
Edit: It was late......
 

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Lighter, stiffer, stronger.. there is no downside. Then again, you could always convert your current bike back to 1" steer tubes if you're not convinced there's a difference. Let us know how that works out for you. There is no downside whatsoever, especially since there are now headsets that let you reduce a 1.5 tube down to 1 1/8.
 

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Tony, in the case of Cannondale, they have been using 1.562" steerers to accomodate the Headshok internals some 15 years ago. It turns out that the OnePointFive standard has a 1.5" steerer but both Cannondale frames and OnePointFive frames have the same internal diameter in the headtube so both a OnePointFive headset and a Cannondale SI headset fit, maybe just a coincidence, maybe the OnePointFive group decided to stick with Cannondale numbers... Since the same frame diameter handles two different steerer diameters, the difference is in the headset used, same outside diameter, different inside diameter.

Nowadays, I always think regular frames for 1.125" steerers look weird and whimpy...
 

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Manitou has all but abandoned it though. Only one model in the entire 2007 lineup uses it. While the fork steerer can be made lighter for a "target" stiffness number with the 1.5 size... all the other parts that go together (like the headset, the stem, and the frame) end up being heavier.
 

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Kracker said:
What engineers have found recently though, most notably at Rockshox, is that for a given tested target stiffness, they can make their products lighter by using a 1.5" steerer. We should not be surprised at this, given that we know how larger diameter thinwall aluminum can be made lighter than smaller diameter tubes with thicker walls. Klein, and ironically Cannondale, first showed us this in frame design many years ago.
I really doubt you will see any weight gain. There is always a little tiny problem with the "equation" larger diameter=thinner walls. The problem is that you cannot decrease wall thickness below certain limits and as a result you end up with a bigger AND heavier component. Just look at handlebars: the new 31.8 bars are heavier then the corresponding 25.4.

As you mention if you are using a double crown fork you could easily get away with a 1" steerer (like motorcycles do), and if you really want more strength for a single crown you can go stronger aluminum or steel (like Marzocchi). I don't think Marzocchi has problems with strength and I would be surprised if a 1/8" steel steerer is not stronger then a 1.5" aluminum.
 

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Davide said:
I really doubt you will see any weight gain. There is always a little tiny problem with the "equation" larger diameter=thinner walls. The problem is that you cannot decrease wall thickness below certain limits and as a result you end up with a bigger AND heavier component. Just look at handlebars: the new 31.8 bars are heavier then the corresponding 25.4.

As you mention if you are using a double crown fork you could easily get away with a 1" steerer (like motorcycles do), and if you really want more strength for a single crown you can go stronger aluminum or steel (like Marzocchi). I don't think Marzocchi has problems with strength and I would be surprised if a 1/8" steel steerer is not stronger then a 1.5" aluminum.
So if you'll reread my post, you'll see that what I'm saying is that, while you are correct that going bigger/thinner EVENTUALLY runs into a wall, we are not there yet with mtb steerers. 1.5" front ends can be made lighter than their 1 1/8" counterparts FOR A GIVEN STIFFNESS.

As for your second paragraph, I don't really know where to begin. Stiffness is not the same issue on motorcycles, as they steer from the rear, not the front. You pitch the bike with your weight and steer with the throttle. Hence all the inverted forks, which are intrinsically flexier than their conventional counterparts. So that is a non-argument. I'm not really sure what you're trying to say with your steel steerer comparison, as that would be heavier, as attested by ever fork ever made, and seeing as how we're discussing weight here, I don't your point.
 
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