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I just bought a mountain bike with a Suntour XCM fork with lockout.

Being a BSO rider, this is my first ever bike with a lockout on the fork. I will be riding trails, but most of my riding will be in an urban setting.

The fork bobs and steals energy while I'm riding, so I figure I'll have it locked out while I'm on pavement.

I ride aggressively, and I occasionally hit potholes.

My previous bike was a rigid steel BSO. It took some hard hits while street riding, but nothing ever happened to it.

This brings me to my question: How strong is the thingy that locks out the fork? Will it break if the front wheel takes a hard hit while the fork is locked out?

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I have read about damaged lockout systems from big hits while locked, so my advise is treat a locked fork as a fragile fork unless you want an expensive repair bill. Probably the key point is what is "a hard hit" and "high load" for a fork? That said, I have taken a couple of what I would call big hits with my fork locked with no damage, but I weigh under 70kg and what I call big is probably nothing to some people.

The manual for the Suntour forks is somewhat contradictory. In one line it says "...This system protects you when riding in demanding terrain in case you forgot to unlock the fork."

Then immediately it states "...The fork may become damaged when it is compressed under a high load...."

The take away I get is it protects you but will possibly be damaged. In your case, I would suggest cranking up the pre-load when on the road, and only using the lockout when you know there are no potholes around.

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  • Does my fork (coil spring) have an automatic unlock function?
    – BSO rider
    Commented Jul 3, 2015 at 17:32
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Suspension forks with lock outs also have blow-off valves for exactly this sort of situation. It takes a really hard hit to damage the fork. You'll more likely dent your rim first.

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  • RockShox forks have TurnKey: "This exclusive technology works a lot like the Secret Service. If you happen to hit a big rock when you have your fork locked out, TurnKey’s patented blow-off design takes the bullet for you, absorbing the unexpected hit instantly.".
    – Cristian Ciupitu
    Commented Mar 5, 2017 at 22:05
  • Do note it's an XCM fork! I can't even imagine what @mattnz means by "expensive repair" - the whole fork costs 40EUR.
    – Vorac
    Commented Jul 10, 2020 at 6:15

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