Take heart, Warren; I'm sure we can solve the problem -- or at least identify it -- through collective effort.
Another couple threads you might find helpful if you haven't seen them already are here:
http://www.thorncycles.co.uk/forums/index.php?topic=4025.0http://www.thorncycles.co.uk/forums/index.php?topic=3563.01) First question, so we know for sure what we're dealing with --
*Are your Rigida Grizzly rims CSS or plain?*
From the sound of it, I would guess they have the Carbide SuperSonic sidewall treatment, but we need to know for sure.
2) The Rigida Andra rim has the same substrate (alloy) but is a different extrusion and weighs more because there is more material (it is intended for heavier-duty use). The Andra also uses no rim eyelets -- instead, it has a center-rib as part of the extrusion, and this rib has cupped nipple seats that work with the nipple to provide a ball-and-socket effect so the spokes take a more direct route to the hub. So far as I have seen, the Rigida Andra and Grizzly have the same sidewall surface, depending of course on whether they are plain or CSS-treated.
An illustration of the Andra in cross-section is here:
http://www.jejamescycles.co.uk/product-images-large/rigida-andra-30-mtb-rim-black-51412.jpgThe Grizzly is shown here:
http://www.jejamescycles.co.uk/product-images-large/rigida-grizzly-700c-se-road-rim-black-51469.jpg3) Rigida (the company) has been through a number of changes recently, and they aren't done yet. Please see a thread I contributed to here:
http://www.thorncycles.co.uk/forums/index.php?topic=3571.0 The upshot of it is, some people have noticed variations in their rims depending on where and when they were made. This is referenced nicely in the CTC link Erudin provided earlier, here:
http://www.thorncycles.co.uk/forums/index.php?topic=3571.04) Mavic's "UB Control machine sidewalls" is their term meaning the rim sidewalls have been lathe-turned to provide a consistently level surface and parallel sidewalls (or, as they put it, "Usiné Brut Control. The braking surfaces are milled to improve braking friction and eliminate shuddering". "Usiné Brut" is French for "Gross machined"). The process is not unique to Mavic, and the two sets of Rigida Andras currently in my possession all have similarly machined sidewalls. Same with a pair of Alex Adventurers in 700C size (and those are very poor stoppers; go figure). Grant Petersen of Rivendell has written about machined versus plain rim sidewalls here:
http://www.rivbike.com/kb_results.asp?ID=52The topic is discussed further here:
http://www.thechainlink.org/forum/topics/machined-vs-nonmachined?commentId=2211490%3AComment%3A164858http://bostonfixed.us/forum/comments.php?DiscussionID=1961http://www.bikeforums.net/showthread.php/346535-Brakes-w-Non-machined-RimsMavic's
ceramic-coated offerings (as distinct from Rigida's Carbide coatings) tend to fare less well than Rigida's CSS in the wet, and there have been reports on other forums of very poor wet-weather braking and the occasional cracking aroound the spoke nipples or of cracks through the ceramic on Mavic sidewalls.
5) The issue with building light rims with heavy spokes relates to distortion around the spoke holes. Light rims built with heavy spokes show evidence of this with continued braking -- those wheels develop a dot-and-dash pattern on the sidewalls below each spoke hole where the extrusion has bulged from the greater localized tension. This eventually wears even, but can be an issue at first, especially when braking in the wet. Generally -- unless there is some special need -- I prefer to match the spoke gauge to the rim to prevent such problems. So do most wheelbuilders.
I so hope something in this post will help. It is a frustrating problem that interferes with the pleasure of riding and yes, it does appear to be the rim that is contributing directly.
Best,
Dan.
