It is very common. I will say that Winters rears seem to do it more than any other brand.

There are many theories as to why it happens. Some feel that the rears aren't "breathing" well enough and the vacuum is causing it. Others feel dirt is the problem. Oversized axles another.

I can honestly say that I have seen it in many different situations and that vacuum and dirt do not seem to be the cause. We have some customers who have the problem and others who never have and they run the same rears in the same application in the same way.

I have only had one rear that the axle grooves caused it to leak. There is the fear that the grooves cause the axle to weaken and make it vulnerable to breaking. I have never personally seen an axle in my shop or the track in which I felt that was the case. I'm not saying it isn't possible, but I haven't seen it.

BR sells a sleeve for that application. I'm sure it is a sleeve that can be picked up at a bearing house. Some people call them speedi-sleeves. I haven't used one.

One suggestion we where given was to put grease inside the seal portion before assembly. It doesn't seem to help, but it isn't a bad idea.