The pivot point near the bottom bracket (very common problem)
Here's another photo of this issue (not my bike)
The pivot point where the seatstay attaches to the chainstay (have only seen this once - my V10 frame!)
Cause:
I believe both problems are caused by overtightening of the bolts in those locations. The Diamondback XSL frame, which closely resembles the V-bike frames, does not have the bolts at the bottom bracket pivot point. I have not closely examined the XSL, but I assume this bushing is held in place with screws on the frame, just like the V-bike frame, but without the additional (unnecessary?) screws on the chainstay. More to come.
Bottom line is there's clearly a design issue here with regard to the chainstay, but I suspect it only manifests itself as a failure because torque specs are no longer readily available. Based on a phone call to customer service, DB currently does not have this info. Perhaps someone working at a bike shop might have old service info?
How did I find out these problems were common and how common are they?
I originally became aware of the cracking problem through a fellow enthusiast's site (click for link). After that, I checked and found the crack on my V-Link 3.2 frame around November 2004. I don't think it was there when I bought my bike used. If it was, then I rode it a lot that way before I noticed the crack.
Once I found the crack, I started shopping for a replacement frame or swingarm. Knowing the problem seemed to be common, I checked with Ebay sellers and had them inspect their frames and send me photos of the swingarm pivot. I've since had several Ebay sellers either tell me they found cracks or send me photos that showed cracks. I estimate about half the frames I've asked about have had cracks (probably about 6 out of 12). If I recall correctly, this includes 5 chainstay cracks and 1 seatstay crack.
Since I set up my DBR site, I have also received several messages from fellow owners who have had frames crack. I estimate another ten have sent me info on their cracks, with about 7 being chainstay problems and the rest seatstays. One managed to have bracing welded on and reported success based on a couple weeks riding that way. I don't have details on how this was done.
What bikes are affected by these issues?
I've only seen these problems on 1997 and 1998 V-Links and V-Bikes (V6, V8, V10). I'm not aware of any frame problems on the carbon bikes (1997 V-Link Pro and 1998 V6 Team); but I suspect they use the same rear triangle, so lack of reported issues may reflect production volume rather than likelihood of occurance. I have never heard of issues on 1996 V-Links (first year of the frame) nor on later X-bikes or XSLs. From what I can tell from photos, the 1996 V-Link had a different chainstay pivot arrangement. Perhaps it is not so prone to cracking?
How do the cracks affect riding?
I rode my bike regularly with the chainstay crack with no problems for about 5 months, including on technical terrain (Rock-It at Aliso-Wood, Chutes at Santiago Oaks, etc. for those who know SOCAL); but I did check on it frequently. In retrospect, riding it that way was proabably risky, but it never did crack the opposite side from additional stress or anything like that and never did anything to cause a wreck (only noise).
What did I do about the problem?
I eventually got lucky and found a V10 frame for sale - with lots of nice parts - locally on Craigslist. I held off on replacing the chainstay for awhile until I heard a really bad creaking. When I took apart the V10 rear triangle to put it on my V-Link, I found the seatstay crack. So...I used the V-Link seatstay and the V10 chainstay. My bike's been this way since May 2005 and I've had no troubles. NOTE THAT I NEVER RODE ON THE SEATSTAY CRACK, so I can't comment on that. I also later bought a used V6 and never had problems with it. Maybe its bolts were never overtightened??
Repairs:
I have heard from many sources that you cannot reliably weld aluminum bike frames. As mentioned before, I have received one email indicating this has been done, but I don't have details.
Replacement:
A Diamondback customer service representative told me on the phone that they have no data, decals or parts for any frames made before Derby (Raliegh) purchased Diamondback.
Note: In no way do I mean for this page to be anti-Diamondback, anti-Derby or anti-V-Link. I personally think these bikes represent a great ride and amazing value. I just want people to know what to look for when they're in the market so that there will be more happy V-Link riders/customers.
To my DBR site
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