I hit a big pothole the other day and my fork bent. I have approx. 2-3mm of clearance and I'm wondering if it is safe to ride. Is the fork weakened now? Should I replace it immediately?

No No Yes.

what kind of steel if that fork made from? I would not ride that bike with that fork, aside from the fact that it could break anytime it will not handle well.

Not necessarily. I've seen plenty of forks returned to usefullness after being bent that far back. However, judging by the positioning of the front brake shoes I'd say that the fork blades aren't bent that bad, which means the steerer tube is bent. That's a definite replacement. Take it to a good bike shop for an evaluation.

That must have been a heck of a pothole!

For safety reasons steel forks have overbuilt steerers made of reasonably malleable steel grades and tempers. I've seen much more serious bends survive and - before fear of lawsuit became an issue - these were routinely straightened and ridden for years afterward.

Bent forks were routinely straightened or ridden as is for decades. Everyone of my generation either rode or knew someone riding a straightened or custom-made short-wheelbase bicycle. But these days that's out of fashion, because in the event of any kind of subsequent failure no shop or professional would want to face a jury in a civil suit. If it were my bike, I'd pull it back and ride it after removing and inspecting the steerer for any cracks.

As for as riding it as it is, the frame clearance is less than I'd like, so I'd first test by lightly taping a piece of cardboard to the downtube thick enough to fill about half the gap at the nearest point. Then ride it on a fairly bumpy course to see if the fork flexes enough to touch. If not, you have the added thickness of the cardboard as a safety margin.

The real issue is toe clearance, especially if you have big feet. Make sure your toes cannot touch the tire at the nearest point.

BTW- if the fork is carbon or alloy it's toast, because those are far less forgiving than steel is.

How is your front wheel?

The wheel is fine, the fork is apparently much less sturdy. I think it's aluminum, not steel. And as for the toe clearance, my toes touch all the time when I'm approaching a red light, just one of the downsides of riding a fixed gear, that happened before the fork got bent.

That is almost certainly a steel fork. Take it to a decen shop and you may be able to salvage it.

it's hard to tell for certain from the picture but it looks like the bend is where the steerer enters the headset and that's probably not good.

Can you feel it in your headset at all when you turn the bike? it's possible the headset is toast after a knock like that. you'd hear it (or more likely feel it) in the headset bearings as you steer the bike.

At least thats what the Mercier website indicates.

But I`d suggest replacing it with another from Mercier - just visit your dealer. At the same time you should ask for an inspection to confirm (or not) that nothing else is outta whck.

Looks like the steering tube itself is bent and if thats the case, the damage is extremely localized. When metal is forced past its yield point, its weaker, and straightening it will actually be doing more damage.

Considering the time it`ll take to set up a gig and straighten that one, it probably won`t be much more expensive to buy a new one. I expect less than $100.