Yeah, in an urban setting with lots of cars, the alerts are almost useless since you have to always ride as if there are cars approaching from behind. But the variable flashing (which the Trek unit apparently lacks) is a good safety feature.

The new interface works vastly better with the 840 touch-screen than the 540 button set. I have the 530 and decided not to get the 540 as it apparently is worse (DC Rainmaker review). I got the 840 for one of the kids. Why? Because I bought him the radar, and he decided he needed a head unit, not just a watch.

Given that they are the same price, what made you pick the Trek over the Garmin 515? I would have thought the Garmin was a safer bet given it’s relatively long proven history (a 3rd gen product).

The second paragraph doesn't follow from the first (the first paragraph doesn't explain anything). We still have no idea why [MENTION=568881]spclark[/MENTION] picked the Trek.

The Trek Carback isn't a "midrange" competitor (implying cheaper with less functions, I guess). It's (pretty much) equivalent to the Garmin 515 in price and function. The RVR315 and RCT715 are quite different products (though one could consider the RVR315 as a "lower range" competitor).

In any case, Trek should be an OK thing to try (even with it not having a long history).

Little more than that I've used other Garmin products in the past, to varying degrees of satisfaction. From what I'd read here in earlier posts I expect it to serve my modest needs. Even with hearing aids my hearing's not so good anymore so having something that provides a sense of what's coming up behind me (when I venture out onto the narrow bike lanes aside the two-lane paved highways when necessary) ought to provide a degree of safety I've been missing. I just got back 'into' biking a year ago in an area that's vastly different from what I'd experienced before moving here ten years ago. Topography's different, roads are different, there are more trucks here than cars, and fewer dedicated bike paths close by home.

​​​​​​​So I chose Trek's CB device over its competitors.

An update on the testing of the Carback versus the Varia ...

Wow, that’s a lengthy review to say that the range is on a par with the Varia and the seatpost mount is poor!

One thing I like with the Varia is the red alert warning tone when a vehicle approaches at high speed. The CarBack doesn’t appear to have that feature. On my local roads (narrow, fast, no shoulder) it quickly tells me if an approaching vehicle is slowing down, which is a good sign that they have spotted me.

Spot on Pete!

That's an audio signal or with the red side shading when using a Garmin device as a monitor?

I haven't yet had a chance to ride with the CB I bought but I did do a MacGuyver on the cheap rubber mount. Pulled out the hard plastic bit with its brass threaded insert, cobbled up a Cestbon bayonet-type aluminum+plastic Garmin mount so the 5mm FH machine screw works with the CB attachment clip. Much more solid mounting to my seat Selle Royale seat's rails that hung from a rubber band off the seat post below.

Sunday's supposed to be 78°F here, sunny with some SW wind gusts to 24 mph so I fully expect to be riding once again for this year! Will report on whether the CB adds to the experience.

Red side shading on my Garmin and an audible alarm warning when a vehicle is bearing down fast. Orange shading and a more subtle audio beep for slower vehicles. Maybe Trek will add something similar in future updates. But I expect you will find your CB useful. I would really miss having that rear traffic awareness now. I ride mostly in rural locations where it is invaluable, especially on descents when wind noise is high and I don't want to be looking over my shoulder.

So, compared to the Varia, the Trek Carback:
--Lacks adaptive flashing as the vehicle approaches
--Lacks the warning for a fast(er) approaching vehicle
--Has a lousy mount

Given that there is no price advantage for the Carback, it seems like the choice is still easy.

Exactly what I'm looking to gain with this device. A bar-end RVM just doesn't cut it.

i wonder who'll embed haptic feedback that not only is at the computer, but sends it to the phone/watch/ring if it's capable?

I'm thinking Garmin would be first as they deal with smart watches...

You get if you pair a Varia with a Garmin watch. (At least with a Fenix 7 watch.)

I'm not sure how haptic feedback would help (or even work) with a cycle computer.

the feedback would rattle the sloppy BB, causing the rider to look downward & as they go to look down they'll see the alert of traffic.

How many Garmin Edge users are riding with smart watches?

The other issue is that each type of smartwatch would require different support.

Supporting their own watches is easier to manage.

It’s possible but might not be worth doing generally (for non-Garmin watches).

I ride while wearing an Instinct 2 Solar. I use the watch for kayaking and swimming. The watch noticeably vibrates with assorted warnings like texts or emails received on my phone. I wonder if a warning generated on a Varia can be set to vibrate the watch. That would be useful as I am unlikely to hear the audible alarms on my 1040.

Note that I didn’t say it wouldn’t be useful.

But your one example doesn’t do much to show that there are enough people to justify the effort (which is what my question was about).

The Varia sends info to the head unit or an app. And those generate the warning (or display stuff).

Do know about the Varia smartphone app?

https://www.garmin.com/en-US/p/716691

There are many more people with smartphones than smartwatches. So, the effort for the app might be much more worthwhile than supporting smartwatches.

The Apple Watch is (probably) much more popular than Garmin watches but it would weird to support those over Garmin devices and, again, it’s not clear if there are enough people who would find it useful. Supporting other smartwatches makes even less sense.

All true

I might be buying a Varia early next week, when I do I’ll find out how and if it interfaces with a Garmin watch

As I mentioned a few posts above, the Varia DOES provide haptic feedback to my Garmin Fenix 7 watch.

I don't know if that capability is available with all Garmin watches.