Do you need a bolt-on top tube bag?

With gravel and adventure cycling taking off, cyclists are always looking for optimal storage solutions for different riding terrains and journey types, whether they be day-long rides or week-long bike packing trips.  

The need to quickly and easily access nutrition and valuables has made the humble top tube bag a staple for competitive and party pace cyclists alike.  

Photo by Patrick Hendry

With the rise of gravel, top tube bags' key features and needs have also evolved.  The rocky, unstable paths have replaced smooth tarmac, and the stability of any cycling luggage has come under the spotlight.

Hence, enter the new iteration of the top tube bag - the bolt-on version.  This new feature has become ever more popular, but do you need it, and does it make sense for your riding style?  This article will help you figure out if you need a bolt-on top tube bag for your bicycle. 

What is a bolt-on top tube bag?

A top tube bag sits just behind the handlebars of your bike, on the top tube of the frame. Traditionally top tube bags are secured using a loop and strap method around the top tube (frame) and headset. 

Photo by Viktor Bystrov

However, a bolt-on top tube bag connects to the top tube using two bolts screwed through the bottom of the bag, securing it to the bike's frame. The idea behind this is to maximise the bag's stability where there is a lot of vibration and rocking, particularly during off-road riding.  You will often find that bolt-on top tube bags still have a velcro strap to attach the front of the bag to the headset for added security.

What type of bikes can you fit a bolt-on top tube bag to?

To fit a bolt-on top tube bag to your bike, you need to ensure that the frame has the required two holes to allow the screws to fasten to the top tube.  

These two holes are usually 6-7 cm apart, use 2 screws and are standardised between different bike manufacturers.  Note, however that different bike manufacturers may vary in the placement of the two holes, some closer to the stem, others more towards the rider.     

Photo from bikeforums.net

If you have an older bike, there is no point even looking for these as they are a very recent addition to the design of bike frames.  If you have a road bike already, chances are bolt-ons are not an option for you.   

However, if you have or are looking to purchase a modern gravel bike, there will likely be two bolts already in the frame (similar to how your bike looked before putting water bottle holders on), so it is easy to spot if your bike is compatible with a bolt-on top tube bag. 

Currently, bolt-on top tube fittings are mainly on Gravel and some mid/higher-end endurance road bikes. 

Can you fit a bolt-on top tube bag to a bike without holes in the frame?

No, is the short answer. 

You shouldn’t try to create holes in the top tube of the frame to allow for installing a bolt-on top tube bag, either! This is a non-starter for carbon bikes and not advisable for alloy frames.  

If you make holes in a frame that were not put there during the manufacturing process, you risk ruining the frame's integrity, and that could be a costly mistake and cause serious bodily harm if something were to happen while you were riding. 

I have holes in my frame.  Is it a given that bolt-ons are for me?

A bolt-on top tube bag will undoubtedly be more stable than a strapped-on bag, and there is no doubt that it will become more and more popular thanks to its effectiveness. 

The addition of screws into the frame means that the top tube bag is always secure, no matter how fast you go or bumpy the track is. Knowing that the top tube bag will not move or hamper your steering gives you extra confidence when riding on the more technical gravel tracks. As more and more frames come equipped with the fittings for a bolt-on top tube bag, more cyclists will benefit from the added security advantages. 

However, how many bikes you have and how much budget you have for bags is something to consider.  Do you have the budget for a dedicated bolt-on bag for your gravel bag? Or do you need to swap one bag between a bike with holes and one that does not?

Most bolt-on bags can’t be fixed on regular bikes (without holes on the top tube), and even if that is an option, they don’t work as well as a top-tube bag with straps.  

So in summary, here are the key pros and cons of bolt-on top tube bag:

Advantages:

• Secure fitting and added security
• Aerodynamic storage solution
• No straps to interfere with gear or brake cables that run under the top tube

Disadvantages:

• Generally more expensive
• Not all bikes have top tube fittings required to install them
• A bit of a faff to remove, as it needs tools (good for security, but can be inconvenient if you have more than one bike with bolt holes and one without)

Is this the end of top tube bags with velcro straps?

These top tube bags have two straps around the frame (top tube) and another around the headset, usually where the spacers are.  These bags will continue to be widely used by cyclists owing to the flexibility offered and the fact that most bikes don't come with top tube fixings.  Well designed strap based bags work excellently and are especially popular in triathlons, where access to nutrition is priority.  

In terms of our approach, we are pleased to announce that our bolt on top tube bag is now available for delivery from February 2023.  Our waterproof Craft Cadence top tube bag already ranks among the best in class for top tube bags with straps, and we are confident we have made the right calls with the bolt-on version. 

Firstly, we have thought through the specific needs of bolt-ons with wide availbility of holes for different frames (6 in total).  See dimensions below:

Second, we think that bolt ons will mostly be used on bumpy gravel and single tracks, so stability of contents will be important.  That's why we have put a side mounted zipped pocket on one side, and elastic bands on the other.  That way, items can be stored safely on bumpy surfaces and won't rattle around as you ride.  Here are diagrams showing our design:

Thirdly, we think that once in a while, one may need to clean the bag from debris and dirt that find their way inside the bag.  That is why we have designed a modular internal system whereby all internal sections (foam padding and hard plastic base insert) can be removed so you can properly clean your bag should you need to.     

Unilke most top tube bags, which use a zipper down the middle, we use a “flip” mechanism that provides effortless one-hand access while providing security through the magnetic enclosure system. 

The seamless welding design makes it fully waterproof, and the flat top with loop allows the mounting of a cycling computer. There is also a cable outlet for charging external battery packs or electronics such as phones and computers if you mount them out front on even on the bag itself.  The headset strap is generously long to cater to different bike types and removable for slammed stems.  

Link to our bolt on top tube bag here.  

Final thoughts

There are some serious advantages to having a bolt-on top tube bag. Namely, the added security and peace of mind that it will not wriggle around mid-ride or get in the way of steering. If you are into gravel riding and have a new bike to boot, bolt-ons are a no brainer. For those with more traditional bikes or who need to swap bags between bikes, a top tube bag with a strap and velcro fastening system will be more than adequate for most cyclists.

What is your opinion on bolt-on top tube bags?  Are they necessary?  Share your opininons with us.