We have a little over 5000 miles on our Team Niobium now (purchased in January of 2006). We love the bike and I have posted some reviews of our impressions with the most recent in March at the 4400 mile mark. http://www.bikeforums.net/showthread.php?t=278514 We did have the experience of having the spokes loosening up on the rear wheel around mile 300 and at the time there was no posted spoke tensiometer reading so we were advised to make it like the front which was 23 on my Park tensiometer. That worked for a while but the rear began loosening up again and I tensioned the wheel up to 25 and eventually and it held that tension. Before the end of last year (but I forget exactly when) Santana posted that the spoke tension should be at 26 on a Park gauge and 95 on a Wheelsmith gauge. This past January, I went ahead and raised the tension from 25 to 26. All has been good until...

Two and a half weeks ago on a Friday we got flat rear tire about 2 miles from home. As I was sitting on the ground and putting the tire back on I saw a crack on the rim going out from both sides where the spoke goes into the rim. I could hardly believe it but looked around the rim and saw more.

When we got home, I held the wheel under a lighted, magnifier shop light and I could visually see cracks at 14 of the 16 spokes - depressing.

Well, there's never a good time for the bike to be out of commission (we have no spare wheels for our tandem) and my wife and I would be riding the 3 State 3 Mountain Challenge in Chattanooga in two weeks but I didn't think I wanted to keep riding on the wheel. I had no experience with cracked rims but I didn't want to learn through by having it fail on a ride. The shop saw it the next day on Saturday and would send the wheel to Santana by 2 day shipping and the repair would be covered under warranty using my existing hub with a new rim and spokes. I called Santana in the mean time on Monday to tell them it was coming and of course we wanted it back as soon as possible. (I had told my wife that I would tell Bill at Santana that I was in a big dog house if we didn't have the tandem for 3 State 3 Mountain - My wife said I wasn't in a big dog house but I was in a little dog house that had no windows - ouch!) Bill wanted to get me out of the doghouse and said that they would replace the rim and spokes there at the Santana shop and would be able to send it back in two days after getting the wheel. So that time frame sounded OK and LInda and I began riding the singles again...Linda and I have ridden 3S3M twice on singles but had our hearts set on doing it with the tandem this year having fallen in love with the tandem and knowing that we would be faster on the tandem (and we bought a disk brake for this ride - which is going to be the topic of another post soon)

In the meantime, I checked with Santana later in the week and found that Shimano had told Santana to send the wheel out for the rim replacement. So that messed up the timeline. I was feeling cramped in that little doghouse but the wheel did arrive back at the shop on a Wednesday, we picked up the bike that evening and gave it a test ride on Thursday and ran into Tandem Geek at the first rest stop on the 3 State 3 Mtn Ride (which he mentioned in his post on the recent Sweet 16 thread)

Last night, with 150 miles on the wheel I took off the tire and checked the trueness and the tension. The Park readings are all around 25 or 26 with the exception of one spoke which has a little bend in it that makes the Park tensiometer read low (because the bend allows the pointer to move - if you've used the gauge you'll understand) I hadn't seen this very slight bend until checking. If I move the gauge up to a different part of the spoke it reads 25 to 26. I'll keep my eye on it. I have a spare spoke I could just replace it.

I did talk to Bill at Santana about the rim failure and he said that he has only seen it on wheels where the spokes loosened up quite a bit and were ridden on for a while which allowed movement at the rim attachment point. I did have loose spokes and they were loose enough to make noise that I could hear from my seat before I realized what was up - but as I've written in my other reviews - I was under the 300 mile mark. Bill went on to say that the initial loosening that riders are seeing is not from inadeqate tension in the first place allowing the nipples to turn and reduce tension but instead its caused by the spoke attachment at the rim becoming fully seated during the initial miles. It sounds like a plausible hypothesis but I'll remain somewhat skeptical - I'll see how this rear wheel ages.

So, I'm giving the wheels another shot. I will be checking the tension closely - especially for these first few hundred miles

So updating my 4400 mile review. First impression of Sweet 16 great - second impression (300 miles) poor - third impression from 300 to 5000 great - 4th impression at 5000 miles not good - 5th impression cautiously optimistic. I should add, the cracks were not visible in January (but they could have been there and too small to notice) at about mile 4000 because I was up close and personal to the wheel raising the tension to 26 in the truing stand and installing a disk brake.

Below are some photos of three separate cracks