Using the Garmin Varia RCT715 Bike Radar When You Can’t Install it On Your Seatpost

The Garmin Varia RCT715 (and other Garmin Varia radar units) are great for improving safety -- or at least your feeling of it -- on the road. However, they're designed to be installed on your seatpost. What if your bike setup doesn't allow for that? Here are some possible solutions.

By: Cheryl

On: February 9, 2024

Last Updated: February 9, 2024

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If, like me, you’ve tried using bike radar, you might find that you don’t want to ride without it. But if, like me, you get a new bike or modify your existing bike so that you find that you can no longer readily use your radar unit on your seatpost, what do you do? This post is about a couple of creative ways I’ve used for installing Garmin Varia RCT715 when I could not install it on my seatpost.

The Garmin Varia radar units come with bands for installation on your seatpost. But what if, for instance, you decide to install a dropper post? And what if, perhaps, you also like to carry stuff on top of a rear bike rack that obscures your Varia unit?

If you’re interested in this post, you might also want to check out our posts on whether you need bike radar and our review of the Garmin Varia RCT715.

Garmin Varia RCT715
This is, at the time of this writing, the best Garmin Varia radar device. But being that it has a video camera in there, it’s pretty bulky and heavy AND it uses a different type of mount than the other Varia devices.

The instructions for these units also specify a minimum height from the ground for them to be effective and that they need to be installed straight-on rather than at an angle.

Of course, there are workarounds for these obstacles, and it took some time to figure out what would work for my bikes.

Mounting options for Garmin Varia bike radar units

The Garmin RTL515 unit- the one without the additional video camera- uses the same quarter-turn mount as the Garmin Edge cycling computers and is, additionally, a much lighter-weight device. As such, there are several alternate mounting options, including saddlebag clip-on mounts and saddle mounts.

However, I went all-out and got the Garmin RCT715. This is a larger, heavier unit because it includes a video camera. I suppose in case someone kills you, at least there will be a video of the accident. Very reassuring. And it uses a different mount than the smaller units.

The issues

My e-bike was the first to get the Varia. But there were issues.

If I used my Po Campo Vernon trunk bag, which I love, the unit would be obscured. And with the dropper post and the size of my rack, anyway, it didn’t work. If I strapped the unit at the bottom of my dropper post, the rack obscured it, at least partially. And I couldn’t connect it to the stanchion of my dropper post for obvious reasons. I use a Brooks saddle. Connecting the unit to the saddle also didn’t work well, and it was still obscured if I used the trunk bag.

A bad photo of my Po Campo vernon trunk bag behind my e-bike saddle.

In the photo above, you can see that if the bag were fully loaded, it would block a Varia in any seatpost or saddle mount. Mounting a Varia on the stanchion just wouldn’t work, and there’s no room to mount it below that, as the e-bike battery blocks it.

Note that I did try out the Varia on another bike without a rack by mounting it with the straps around the dropper post collar, and that did work. What you can’t see in this photo is that, in the back, the bike has a wired rear light taking up the 50mm taillight bolt holes on the rack. As I don’t want to disconnect that, installing it there wasn’t an option.

So what to do? It took some creativity.

Let’s look at my solution for installing my RCT715 and some alternate connectors for the other Garmin Varia units.

What the Garmin RCT715 comes with out of the box

Out of the box, the Garmin Varia RCT715 only comes with some collars to attach it to a seat post and some silicone straps to hook those on. (The photo below includes a plate I detached so I could install it using the method below as well.)

Installing Garmin Varia RCT715 a few mounting parts.
Here are a few seatpost mounts (minus a few of the silicone straps) that come with the Garmin Varia to mount it on your seatpost, along with a BUP labs saddle mount that did not work for me due to the width.

Alternate connectors for the Garmin RCT715

When finding alternate connectors for installing Garmin Varia RCT715, the choices on Amazon are limited. They have a seat post mount and a saddle mount.

The best solutions I could find to tweak the unit’s installation were from BUP Labs.

They make a variety of mounts, including some for installing Garmin Varia RCT715. These, combined with some GoPro mounts and arms, finally did the trick. I experimented with 3D printing some RCT715 adapters. However, they were too weak for my comfort if printed with PLA. It wasn’t worth printing with a new material when I could buy a mount from BUP.

Be careful when ordering a mount from BUP. In most cases, you’ll need to get two pieces: the mounting base and the mounting arm. However, with my bike, I ended up not using their mounting baseplate. For my purposes, I just needed the Garmin RCT715 mounting arm so that it would connect with GoPro connectors.

If you have a light mount on your rack, you can just get a GoPro-compatible rack light mount plate. BUP has one available on their website. Then, you have to get the mount arm specific to the RCT715. This part has a hole at the top to connect it to a Garmin mount. You then unscrew the default seatpost attachment from the plate that came with the Garmin and attach it to the one you received from BUP Labs. You can kind of see this in the photos below.

But I had an issue: my light plate was taken up. Any place I tried to install the Varia was blocked or would end up being at an angle or too low.

My Solutions to Installing Garmin Varia RCT715 on my bikes

Installing Garmin Varia RCT715 on my e-bike

With my e-bike, what I finally did was this: get creative.

My bike rack is hefty and I found that the GoPro bike handlebar/post-seatpost mount with the smallest rubber shim would clamp on to the back of my rear rack.

Mounting the BUP Labs mounting arm directly via a Gopro connector and short arm would have resulted in it not being place correctly, so I used some HSU GoPro arms and adapters to lengthen the placement and put the Varia device into a straight-on position. This has held up quite well, and has stayed in place during rides and even in carrying the bike on the back of my vehicle (though I always remove the Varia before transporting the bike).

The BUP Industries Garmin RCT715 Mounting arm in grey is attached to the unit, along with some GoPro mounting arms and a GoPro clamp-on handlebar mount, attached to my bike rack. I eventually relocated the installed light and installed the varia in the designated light mount. But I am unsure of that arrangement and may move it back to what you see above!
HSU Go Pro Arms
This is the type of GoPro arms I used in the photo above.

Installing Garmin Varia RCT715 on my gravel bike

At some point, I wanted to go “analog.” Soon, I was down the rabbit hole of building a bike from parts. However, I’d grown attached to traffic input from the Varia RCT715. I wanted to also use it on my new bike. In many ways, my new me-powered bike is set up like my e-bike. It sports a Brooks saddle, dropper post, and rear rack. But my new rack also has no available spot to add the mount.

However, do not believe that I will be carrying a bag atop this bike rack unless it’s camping gear. In that case, I’ll be mostly off-road, where the point of a radar device becomes moot. That opened up the possibility of installing the unit closer to the saddle.

Because this bike also has a dropper post, a seatpost mount option was out of the picture. And, again, I have a rack, so mounting it at the bottom near the dropper post collar was out. The rack would, as well, obscure it. Additionally, the dropper post I am using is a RockShox Reverb AXS XPLR. Its battery compartment takes up quite a bit of space under the saddle. Between that and the width on the outer part of the Brooks B-17 carved short saddle rails, I could not use any available saddle mounts I could find. And, no, I’m not giving up my Brooks saddle!

My Favorite Saddle: The Brooks B-17 Carved Short
Saddles are never a one-size-fits-all thing. But for much of my riding this, combined with a good chamois saves my butt.
RockShox Reverb AXS XPLR dropper post
Loved it! The advantages were that there was no installation, no cables. Worked great. But the big battery meant that it was difficult to use anything that clipped to the saddle rails.

Fortunately, Brooks saddles have those two little loops. And zip ties exist.

I used a bike rack light mount and zip-tied it to the loops on the saddle.

Yes, it dangles a bit, but so far, it’s worked fine, and the zip ties have held it securely.

Here’s a view of the BUP mounting arm for the RCT715 from the back:

Summary

If you’re struggling with installing Garmin Varia RCT715 because, like me, you like weird bike setups, don’t give up! Get creative, and you’ll find a place to put it.

Bike Radar Poll

This post was moved due to a website URL change. In the past, we had a poll here about bike radar. But unfortunately, we decided to limit the number of features on this site to help it run better.

So, we’ve recreated the poll in the format we have available. If you are registered and logged in, you can take it here. Otherwise, it seems to be view-only.

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2 responses to “Using the Garmin Varia RCT715 Bike Radar When You Can’t Install it On Your Seatpost”
  1. Cheryl Avatar

    I’m mostly posting this comment to test and style the comment form. However, I did try installing the light, for a while on the rear light plate of my rack. But for that bike, seemed a bit too low — and I also preferred that placement for my wired tail light vs the other place I had mounted that. So it’s back on the GoPro mount on my cargo bike.

    1. Cheryl Avatar

      I’m just replying to check the comment layout.

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