Hi everybody,

First of all, let me just say that I'm not a professional cyclist or even anything close. I have a Carrera Vulcan Mountain Bike which I ride to get to and from college, cadets, the gym, work and where-ever else I need to go. As a 16yo, who can't start learning to drive until I'm 17 (In the UK), my bike is my only real way of getting around. However, I'm not a professional, I don't own a road bike and I know the best part of nothing with the mechanical side of things.



Now, this may be a common issue w/ an easy fix, but as I said, I'm not a professional, so I apologies if this seems a bit silly.

So, I usually bike about 15-20 miles a day. Most of the time the bike is absolutely fine with no complaints. However, once in a while it does something very odd. It feels like the handle bars become 'sluggish' and turning the handlebars takes just that little bit more effort than you'd expect. It's like the front wheel isn't gripping the road, or at least not turning. More concerning, it also seems to become unstable; the front wheel will start drifting either left towards the kerb, or right into the traffic, despite the fact I'm trying to ride the bike in a straight line. I consider myself to be a stable cyclist, and can usually keep the bike exactly where I want it; but when this sluggish feeling starts, the bike starts drifting left or right, the handlebars feel sluggish to turn and there is an excessive amount of pressure required to try and keep the bike going where you want it.

The problems intensify going round corners, with the bike feeling unbalanced and the front wheel feeling like its going to lose grip at any moment. One coming back from work, I was going around a roundabout when the bike wasn't gripping as much as it should have been. I put a little bit more effort into the turn and suddenly the front wheel bit and oversteered, almost taking me into the other lane of traffic.

The weird thing is that this feeling of missing grip comes and goes. I only normally experienced it on the way to work, and just presumed it was the camber of the road. However, this morning I biked to college using the same route I've done for years. On the way back however, this sluggish feeling started again, and I've never before had it on this piece of road. And the puzzling thing is that this lack of grip feel comes and goes without any warning or clue what was causing it.

I appreciate this is more of a mystery than a straight out question, but would could be causing this? I have knobbly tires on both front and back; and whilst they are the default tires that came with the bike, they still have good grip, the wheel doesn't look bent to the eye, and I can't see any un-even wear on either tire.

Hope you can help me with this bizarre circumstance.