I started using a cygolite from about 15 years ago mounted on my helmet. But the light is heavy and the weight is causing me neck pain. I want get a handlebar mount but I do not know if my old light will still fit the newer mounts. Are they the same?

https://cygolite.square.site/shop/headlight-mounts/3

They have lots of different ones.

I don't know of any lights heavy enough that they would cause someone neck pain, so I cannot guess which one you have.

I have three that I believe I bought around 2010. One says Metro and two say Expillion. They are all heavy. I contacted Cygolite support and sent pictures.

Looking at the link I posted and the model names you listed, they all use this one

https://cygolite.square.site/product...&category_id=3

(which is also the mount I have). I've never had a light mounted on a helmet, so I really don't know. They all seem light enough in the hand.

When I first started using it I felt it in my neck, then it seemed to go away. It does not take much extra weight cause a problem. It's like wearing a coal miner's helmet on the bike. They are great lights and people can really see me coming which is important in the traffic around here. No biggie. I'll just put it on the bike. According to my research the bar diameter on my Cannondale Super Six is 31.8 mm so I ordered a metro bracket that goes from 24-35mm. That should do it. I hope.

I was able to get the helmet mount to work on my handlebar while I wait for the new mount I ordered. My bar is 31.8mm and the recommended replacement is rated for 32mm. I have a wrap on my handlebar which will affect sizing so I ordered a replacement mount that can accommodate a bar width that goes from 24 to 35 mm. My neck feels better today. I am fairly sure the culprit was the light on top of my head. I have three of those lights that I got in 2010 and they are a very good product. I may even ride after dark again this year. By the way, I ride 300 miles a week.

Their tail lights are outstanding.

It can't weigh more than my fiberglass motorcycle helmets weighed when I used to commute to work wearing a helmet. How much does that light weigh that it causes a problem with your neck? Highway wind speeds with a motorcycle helmet gave me good neck muscles years ago.

But if you sprained something in your neck, might take a few months of light duty to heal. I am not questioning what you need to do to heal.

My neck issues have cleared up. I rotated the base 180 degrees on the helmet mounting bracket and used the strap to attach it to the handlebars. I took a piece of electrical tape and wrapped it around the excess strap. I bought another Cygolite mounting bracket online for my other bike. I bought one with a larger range of sizes because tape on the bars increases the width. I am all set now.