Bad Ideas: the hidden nipple

Roval hidden nipple 1.jpg

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p> One of the things I hate is the proliferation of wheels with spoke nipples hidden inside the rim, rather than having wrench flats exposed outside the rim. There are 3 halfway plausible reasons to do this:

1) The smaller whole at the rim may have better fatigue behavior compared to the larger hole of a traditional drilling. However, hole size probably isn’t the most significant factor in fatigue behavior, and you’ll notice none of the manufacturers are toting this idea.

2) Aerodynamics. However, you’ll notice that the 2 wheel makers who probably spend more time in windtunnels than everyone else combined, Zipp and Hed, both use external nipples on their top-of-the-line wheels. And it’s stupid to talk about improving the aerodynamics via hidden nipples on wheels like Campagnolo’s Neutron when it’s box-section rim is patently rubbish for cutting the wind.

3) The structural portion of rim is capped by an aerodynamic fairing which blocks access to the nipples from direction of the hub, so that access from the tire is necessary.

I’ll won’t complain about the hidden nipples on Hed Jet-series wheels of the Mavic Cosmic Carbone wheels. Both of these wheels use a carbon fairing bonded to an aluminium rim. Since the carbon is not structural, the nipple must connect to the aluminium portion of the rim. Thus the raison d’être for the hidden nipples is structural rather than aerodynamic. But on most of the wheels with hidden nipples, traditional nipples could have been easily spec’ed. It’s like the designers went out of their way to sacrifice serviceability for the pretense of aerodynamics. A rim that is less than 30mm is not going to be aero, and hidden nipples ain’t gonna change that.

Curiously, pro riders and especially team mechanics probably have resisted the spread of hidden nipples. Pro team mechanics HATE hidden nipples, especially since they’d have to pull and re-glue tubular race tires in order to true wheels.

Hidden nipples suck because I have to pull the tire, tube, and rim strip just to access the nipples. What really sucks is when I do all that just to discover none of my wrenches fit the now revealed nipples, like with these Roval (Specialized) wheels. Whatever size nipple they use, my 5mm and 5.5mm sockets won’t fit it. Okay, let me just use my dial caliper to measure the width of the hex nut nipple…oh, wait, I can’t….because the nipple is bleeding recessed in the rim. Lovely.

roval hidden nipple 2.jpg

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I fully realize that this subject just begs for some off-colour innuendo…maybe something about bikinis and bike wheels….but I’m just too tired to go for it right now.

blah, blah, blah…get out them nipples….whatever



3 Comments

Agreed on all points.  Personally, I think it’s an entirely aesthetic choice by the engineers….

I had a set of Neutrons though and I only had to true them once and thats because I busted the rear dérailleur and the chain jumped the inside of the cassette and damaged the spokes (see, pie plates aren’t totally useless).  I rode them exceptionally hard until the rims finally wore out.  Very nice general, was quite happy with them even with the internal spokes.

I have Shimano wheels with the nipples at the hub.  At least one can argue that they reduce turning mass, but you have to buy a special wrench to reach and adjust them.  Big pain.

oh yeah, i already bitched about Shimano’s design in a previous post. rumour has it that professional teams had a special hatred for that design…a hatred that i share as well.

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