Whats that clunking, check your battery


Active Member
My Bulls Evo 3 27.5+ hardtail developed a sound which at first I thought was a loose headset and then possibly a damaged fork, thought I would share this story to help others.

I first noticed a defined 'clunk' sound when lifting the front tire to clear a curb. I first noticed this after flipping the stem to lower the handlebar.

Since I had just changed the stem, the first thought was a loose headset. I also thought that having the stem without any spacers below might be causing issues in getting the headset tight so I ordered the smallest headset spacer I could find to put under the stem and installed it. I could have sworn this fixed the issue.

So all seemed well.

Much of my rides dont really need a suspension fork so probably 75% of my rides are with the fork locked out. About two weeks ago, the fork was 'not' locked out and as I dropped off a curb I heard a horrendous clunk sound. When I got home I noticed the shock only had about 20psi in it (130psi is where I set it to). My thought was that the 'clunk' was the shock bottoming out. So the front shock is not holding air well (lbs is fixing it as I write this) but that doesnt appear to be the problem as the suntour shock has also specific parts(secondary spring) to handle bottoming out.

This bike (and probably any bulls bike with the brose system) has some adjustable bracket stuff at the front of the battery you can adjust to make the battery fit tighter and this appears to be the issue.


New Member
Thanks for the information. I have the same bike (BULLS E-Stream Evo 3 27.5+ hardtail). I'll have to check it out.

Had you ever removed the battery before the 'clunk' sound? I've always recharged with the battery still in the bike, never removed it.


Active Member
Thought I would provide an update on this.

As it turns out, the clunking sound when lifting the front tire to get over something was due to the rebound adjuster at the bottom of one of the legs being broken. Im guessing at some point a rock came up and broke it off so the rebound adjustment was at its minimum (i.e. no rebound damping). Forks with no rebound damping clunk when you try to lift the front wheel to clear an object like a curb.

Bulls being a european based company used a fork that is hard to get parts for in the US (in general Suntour fork parts are hard to get). Most axion forks in the US are 34mm stanchion but mine is 35mm.

The damping cartridge(only available thru LBS) to fix the rebound issue is $200 with a 25% discount and it has to be shipped from europe so $$ for shipping. So probably $250 to get this fixed (including shop time)

Im just living with the clunking for now but will replace with a rockshox yari. I can get one new for $400 locally.

Choosing the Rockshox as I can actually buy parts for it and do the work myself(lots of youtube videos showing how to service) saving down time and shop time. The rockshox also has a better design for the rebound adjuster allowing it to be replaced independently replaced without replacing the whole damper cartridge.

I also considered a Fox float 34 but it has the same issue (A $$ damper cartridge with a VERY fragile nub at the end to adjust rebound damping)
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