threadless headset spacer placement hmm???
 

would it be possible to take a headset spacer and put it between your headtube and fork crown in order to move the front tire away from the downtube so you could do barspins?

nope. look a little closer and you'll see why.

they do sell this though:
http://www.serotta.com/Merchant2/mer...ory_Code=SSAMP
press it into the bottom of the headtube, then press the headset into it. used to be ti, now it's aluminum (not sure why i typed that).

hmm thanks spooki. that looks like just the ticket. if only it werent so big. like a quarter of an inch would be good i think.

That is the most contradictory part description i've ever read. I think my head just exploded.

Just run over the fork with your car to increase the rake.

serotta's 'heads up' is *not* intended for the underside of the headtube.

Yeah, just take the for off, remove the wheel, face it arch side up on the floor, get a 2x4, lay it across the center of the fork arms and jump on it a bit :) Voila! Barspins.

uh yeah, id rather not risk busting my fork when i cant afford a new one.

and would that not weaken it as well?

but im actually thinking about doing it...

get a smaller wheel.

that doesnt look safe at all

Cane Creek makes a headset that effectively extends the bottom of the headtube by 5mm. It's designed to keep suspension fork crowns from smacking the downtube, but if that's all the length you need, it might work.
http://www.canecreek.com/s-3-plus-5-headset.html

http://chrisking.com/parts/baseplates

bigger crown races.

these might/probablydon't/definitelywon't work with other headsets.

it wasn't intended for it, but lots of people use it for the underside. i didn't even know they existed until i bought it for the underside...
risers weren't intended for track bikes, but that doesn't mean they don't work.

i could wipe my ass with my hand too...but i don't. just because it 'works' doesn't mean it's an appropriate solution, or clever, or even safe.

were it me, i'd ask serotta if they thought it was ok. also, consider that you are slackening both head and seat tube angles and altering the intended geometry of your frame.

OP wants to do barspinz - I hardly think they're too terribly worried about the frames intended geometry.

so you've never held one, mounted one or ridden one, but you somehow know they aren't appropriate or safe?

describe how they fail, please.

Then again, anyone with an ounce of mechanical aptitude would be able to evaluate the setup and determine that it would indeed perform the task.

in fact i have installed several for customers, all on top of the headtube as intended, where they are quite appropriate and safe. what i am questioning, and what i have no experience with, is the suggested jury-rigging of installing them upside-down.

my first ounce of mechanical aptitude agrees...sure, it would 'perform the task' (as would the hand in my previous example). once again, possible and appropriate can be worlds apart.

but my next and far more thoughtful ounce says, no way do i want a 1/2" deep press fit joint (one side of which is aluminum) taking all of the forces perpendicular to the headtube generated by 175lb of bodyweight and amplified by the 15" lever we call a fork. notice the trend in oversized lower headset cups? there is a lot of load there. ask a framebuilder what they think about your proposed setup...i can hear the laughter already.

how do they fail? i hope you never know. i would imagine that it wouldn't be catastrophic, but that it would ovalize either itself or the headtube and get loose. then again, if it did fail suddenly (aluminum after all) the front end of your bike would collapse an inch or so, and probably not at a very opportune time.

i'm just trying to keep you kids from hurting yourselves. but y'all seem to know better, so carry on...

I have several of the Heads Up adaptors, they are for the TOP of headtubes only.


Please post pictures after the crash. Make sure to start the story this way: " I was just riding along, when my headtube and fork broke and I landed on my_____"

the 15" lever isn't going anywhere. it's pressing (in 306 degrees) against the walls of a pressed headset (at the top) which is pressing (in 360 degrees) against the headtube-- all with 0 play. at the bottom, it's pressing (in 360 degrees) against the part in question which is again pressing (360 degrees) against the headtube-- also with 0 play. unless you're saying that any sort of jumping on a bicycle ovalizes an aluminum headset + headtube over time, there's no physical way that the steertube is all of a sudden able to rip through an upper headset cup + headtube + this thing (either 1/8" of aluminum or titanium). you say you've installed one, but it appears you weren't paying close attention to what was actually happening... any pressure applied to the lower headset cup means essentially that your steertube bent enough to bypass the top headset+headtube and the heads-up + headtube. in other words, your fork's steerer snapped -- and not at the crown, the fork's weakest point. if you were to put the above scenereo into a physics simulator, i'd bet $5 grand that the steertube and crown separates before the steertube snaps 1000 times out of 1000. if you're telling people not to ride tricks in the street, this should be why-- not because you think the steertube is going to magically snap or bend at one of its strongest points (as far as leverage is concerned... this might be plausible if you were talking about the middle of a steertube, but we already went over how that's not possible either).

also: the oversized lower headset cup doesn't come into play with what you're saying. the lever acting on the bearings or anything apart from the walls of the headset inside the head tube has zero to do with what we're talking about. the thickness of this material hasn't changed for decades (ever?), and is exactly the same on road cycles as it is on mountain and bmx bicycles.

honestly, just because something looks different or unfamiliar doesn't mean you should be scared of it. until you test something (or at least spend a few minutes actually thinking about how it works), you shouldn't voice so matter of factly an opinion on it.

i'd be willing to bet that as recently as five years ago, you were one of the guys saying "carbon breaks too easily, it's not safe."

one more thing:
i'm pretty sure they don't make bicycles for 350lb gorillas... or are we talking about unicycles here?

people have been riding the heads-up on the bottom of y-foils since about 2001. i've never heard of a single one breaking. why? because it works.

on the contrary...it has everything to do with what *i'm* (finished) talking about. i suggest you take those few minutes to think again.

ah.

watch out everybody-- installing a heads-up is going to break your bearings.

oh brother... i really hope people don't come to you for mechanical advice.

LOL ,are you guys, the same guys that say " wheel spacers and low offset backspacing wheels , will ruin your wheel bearings " ? ... :)

BTW : The answer for the OP, is on the sheldon brown site. :) x2



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