Home OutdoorCycling How to mount the Thule Child Seat on the handlebars

How to mount the Thule Child Seat on the handlebars

by Tom

The assembly of the seat itself is uncomplicated and hardly encounters any language barriers thanks to the purely illustration-based explanation. The assembly steps are simple. Anyone who has ever mounted an IKEA Billy shelf manages the Thule Yepp Nexxt Mini* with ease.

Whether you can actually feel the 2nm torque specified in the assembly instructions for locking the footrests on the seat with the supplied tool exactly or over-torque by 4nm is written in the stars.

Mounting the Thule Yepp Nexxt Mini on a mountain bike

Installing the Thule Yepp Nexxt Mini on a mountain bike is possible, but not a walk in the park. Here, the footpegs touch and rub on the fork crown. Don’t forget to add protective foil!

The installation manual of the supplied “Slimfit adapter” for “normal and Ahead stems” was minified to only one page of illustrations in the assembly instructions. Looks easy: Just put the two-part adapter with two plastic collars for angle adjustment (A: flat angle, B: not quite so flat angle) around the stem. Then just tighten the two Allen screws with 8nm torque. At that point, you might ask yourself how if you’ve already reached the 8nm with the supplied IKEA style Allen wrench. Good thing I already bought a torque wrench.

DISCLAIMER: Here comes even more technical chit-chat

The “slim fit adapter” needs at least 21mm of space between the headset and the stem. Interesting definition of slim.

But I don’t get that far. Because the assembly instructions describe the process only for “normal” stems. If you – like me– own a bike that doesn’t come from the cheapest section of Wal Mart you most probably have an Ahead stem. Bikes with Ahead stems (which should be 80% of bikes from 400 $ up) usually have several spacers at the exact mounting point of the adapter. If you have no spacers between the stem and the headset, you might be out of luck. To match the maximum stem diameter of 28mm specified in the instructions you would have to (see update below: must) remove these and clamp the adapter directly on the steerer tube. Therefore, you would have to unscrew the stem with handlebars. And hope that the plastic of the adapter can cope with the task of the aluminium spacers.

Or you take the plastic half rings for the “angle adjustment” out of the equation. Then the adapter can also be clamped on the outside of the spacers – unless these spacers are super thick. Whether you should do that, is up to you. After mounting the seat to the adapter and testing it with vigorous lateral pressure, I decided that it should be enough for gentle rides over asphalt, gravel, forest trails and gentle single trails. You should avoid extreme terrain with a toddler in the child bike seat anyways.

If that does not work for you and the adapter rotates around the steerer tube with the spacers, you can try to add a squirt of carbon assembly paste (e.g., Muc Off Carbon Gripper*) between spacers and steerer tube, or switch to different spacers.

I have contacted the manufacturer concerning the assembly and I am waiting excitedly for a clarifying answer.

Update: Reply from Thule

The answer from Thule has now arrived. I was advised to remove the spacers (spacer rings) under the stem and clamp the adapter directly on the steerer tube. This requires the disassembly of the stem. Those who are not familiar with this should definitely go visit your favourite bike shop. If you are, go visit your favourite bike shop anyways.


The installation of the Yepp Nexxt Mini* on the mountain bike is not really smooth. The manual doesn’t say anything about mounting on Ahead stems, although it is explicitly advertised by Thule for this. Unlike its predecessor (Thule Yepp Mini*), the Thule Yepp Nexxt Mini got no dedicated Ahead adapter. Unfortunately, the Ahead adapter of the Yepp Mini is not compatible with the Thule Yepp Nexxt Mini.

Update Conclusion:

We used and loved the seat in everyday life and on tours for about a year – despite the installation hassle. Mainly because the front seats make your toddler your co-pilot and not a passenger. On bikes with a short upper tube and high bottom bracket, however, mounting and dismounting quickly becomes a circus act. A hydraulic seat post with a handlebar remote allows you to get on the bike from behind and eases getting on and off the bike. The same applies to legroom. On my somewhat “old school” KTM Lycan LT 272 Enduro MTB from 2015, you had to fold the knees a bit outwards to avoid bumping the seat when pedalling. More modern bikes usually sport a longer reach and – with the “boost standard”– some extra space for the kneecaps. But as always: you need to try this for yourself, your bike and your legs.

If you’re looking for a simple child seat solution for your mountain bike and want to avoid tinkering, you might rather switch to another seat (e.g., the Yepp Kids Mini*, the Mac Ride or Kids Ride Shotgun) or have the seat mounted in a workshop. The concept of a front-mounted child seat convinced us, the implementation in this case not quite. We later switched to the Mac Ride and the Kids Ride Shotgun. Both are great seats, but require your kids to sit very stable and not randomly fall asleep.

* These are affiliate links. You support our effort if you use our links to buy something. We will receive a small provision. There will not be any extra charge for you. Thanks for your support 🙂


Arthur 2. January 2023 - 23:21

Hi, it’s not clear from your post but I am having the issue where my stem is thicker that the 28mm. It fits on if I remove the plastic inserts with arrows pointing to A/B, but i am not sure how necessary those are for stability or rotation of the seat. Did thule say it was okay to use the mount without the two halfround inserts?

Clare 4. June 2023 - 22:00

Also seeking the answer to this question

Tom 22. August 2023 - 22:14

hi Arthur, hi Clare,
I mounted the seat without the A/B angle adjustment spacers directly onto the aluminum spacers, which worked for me, but I cannot advice you to do that, because Thule specifically adviced me to remove the spacers from the fork’s steerer tube – and use the A/B adjustment spacers.

If you have a 1,5 Inch straight steerer tube or a Cannondale Lefty not a tapered one (1 1/8″ – 1,5″), I guess you have to remove the A/B adjustment spacers of the Thule Yepp Nexxt Minis mount.

Unfortunately I cannot test it myself, as I sold the seat about 4 years ago.

If you are unsure if what you are doing is correct, please consider contacting a bike mechanic and/or Thule’s customer service.

If you stumble across any new information, we would feel delighted if you shared it with us in the comments below.

Cheers and good luck 🤞

Marleen 20. May 2023 - 08:54

Thanks for this, I was stuck and found no help on the Thule websites or their customer service. I did as you wrote and can now ride with my little one in her Yepp mini!

Kristina 22. August 2023 - 11:30

Hi Marleen, this is great!!


Leave a Comment

* By using this form you agree with the storage and handling of your data by this website.


Cookie Consent with Real Cookie Banner