Originally Posted by
crewdoglm
I've been considering a pair of chinese carbon rims for no reason in particular apart from the price. I strongly suspect that these chinese outfits offering generic rims are in fact the OEM's for expensive known brands where a set of stickers takes you up to $700+ per rim with no difference in quality. I could be wrong and I'm open to reactions at that point but my real question goes to spoke holes: How is the strength of a carbon rim affected by the number of drillings? I am thinking of building a track set with 50MM depth and 28 holes but I'm wondering if the strength of a carbon wheel would be reduced by having that many holes. Intuitively, I would think the opposite is true as with alloy but I'm not an expert on carbon. All the 20hole carbon wheels I see invites the question 'why so few holes?' Have at it guys...
First off, you really should be more careful about tension assumptions with regard to carbon rims.
While with most alloy rims today, you can assume a ballpark of 95-100 front and 110 drive side rear for 32/36 hole, it's a little more questionable for carbon rims.
For example you could pick up and old Zipp 404 and assume that it looks okay for 110 kgf - only to discover that it was actually rated for only 80 kgf.
It really is best to try to get a "word" from the source or manufacturer as to the kgf rating - better safe than sorry considering carbon rims can fail catastrophically...
Download my spoke length calculation spreadsheet at:
http://www.mrrabbit.net/wheelsbyflemingapplications.php
View the rimchart and see the notes for Enve, Zipp - and more importantly Jerry Store rims often bought off of eBay.
That'll give you some idea of what you are faced with.
=8-)