headtube extension vs spacers?

[Climb01742]

eddie's aesthetic post got me thinking. is there an engineering difference between using a headtube extension (or simply a taller headtube) vs using spacers? is the difference purely aesthetic or is there a physical/performance/structural difference?

i don't know enough to know where the line is between a valid aesthetic choice and an invalid design decision. i ask this not to fight, but to learn. thanks.

[Jeff N.]

I've always liked a little of both. Jeff N.

[Bill Bove]

I'm sure others, both qualified and not may disagree with me but, it would seem to me that a taller headtube would be a stronger/stiffer front end than the same amount of spacers put between the stem and headset. It's also my opinion that a toptube that slopes up to the headtube extension, thus elimenating the ugly, IMO, headtube extension and then slopes down to meet a lowered seattube to give you back the standover that you lost by sloping up in the first place looks better than a headtube extension on a level toptube. JMO.

[musgravecycles]

Especially with today's carbon steerer tubes a taller HT is more rigid than a bunch of carbon spacers on a carbon steerer.

IMO there has to be a balance between the two. You don't want to have a 20mm extension with 3mm spacer (at least I wouldn't), nor would you want 5mm of HT above the TT with 35mm spacers...

[Smiley]

Billy and Musgrave have it right .

[Ken Robb]

I know from experience that one big (custom made from aluminum tubing)spacer was noticeably stiffer than a bunch of little spacers stacked to the same height. I forget the exact stack height but it was to use an uncut Ouzo Comp on a 59cm Litespeed. I could feel the stack of small ones shifting in my fingers under side load testing but felt no shift with the one big spacer.

[92degrees]

I was going to post earlier in the '05 Catalog/Steel thread that it occured to me that in the '03 and '04 catalogs the bikes, in general, seemed to have 1.5cm HTEs (plus a healthy stack of spacers) while in the '05 catalog the bikes tend to have smaller HTEs. Is this a trend or a change in philosophy? My new bike was designed with 1.5cm HTE and I actually prefer the smaller extensions -- a similar extension above the HT and below the DT. Oh well, I think it was the right solution for me...

[hypnospin]

yes, it would seem clear that with the taller headtube a better platform is provided than piling on the spacers. when these spacers are excessive it compromises rigidity and is unsafe as things can snap off more readily.

also many are riding more spacers than is spec'd by the mfg. as many bikes are setup by shops this way, and these spec's are for safety and mfg. liabilty.

but you will not be able to lower the stem below a certain point with the headtube extension. this may not be a big deal if your position is appropriately dialed in for you.

but if you are adapting to cycling and will gravitate over time toward lower with miles, fitness and form you may well be stuck too high to position the stem optimally with the headtube extension.

in this case one is better off without the extension.

I'm sure others, both qualified and not may disagree with me but, it would seem to me that a taller headtube would be a stronger/stiffer front end than the same amount of spacers put between the stem and headset. It's also my opinion that a toptube that slopes up to the headtube extension, thus elimenating the ugly, IMO, headtube extension and then slopes down to meet a lowered seattube to give you back the standover that you lost by sloping up in the first place looks better than a headtube extension on a level toptube. JMO.