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.

As the problem occurs either with turning or trying to remain on a straight path (which also involves turning, as you are always correcting your path) we need to look at the part engaged when turning. That would be your headset (fork bearing) not the wheel. I would guess that either it is adjusted too tightly or there is an internal problem - bad ball bearing, grit or other contamination, etc. that interferes only at certain times. There is a possibility that it's adjusted much too loose as well, now that I think about it. If you had any type of serious accident that could also be a factor.

The process of checking it involves feel and touch, which we can't do from here, so even if you describe what you find we may or may not be able to determine the problem. Given the safety factor involved, and especially as you have already had an accident I would very strongly advise you to have an experienced mechanic resolve the problem, unless you are willing to not ride the bike at all until you/we figure it out. Besides, if the fix involves headset overhaul you will need both tools and knowledge you may not have.

If you do want to try your hand: stand over the bike and apply the front brake, then rock the bike back and forth. You should not feel and "clunking" or hear rattling. Lift the front wheel and see if the front rotates smoothly on it's own from side to side and when you turn it with the bars. Then check this page: https://www.sheldonbrown.com/headsets.html#threaded. Study it thoroughly, particularly the sections on adjustment. You can also check the Park Tool page that applies to your headset:
https://www.parktool.com/blog/repair-help/threadless-headset-service OR https://www.parktool.com/blog/repair-...eadset-service

**Although I believe the culprit is likely the headset it certainly can't hurt to check your front wheel while you're at it. If much too loose I can see it possibly causing instability. When you lift the wheel off the ground it should rotate at least a bit on it's own and rock slowly to a stop. When you take hold of the wheel and try to move it from side to side you should not feel play or hear rattling. Rotation should also be silent. Adjustment or overhaul would require a cone wrench for proper completion.

Do the simple things first like make sure the front wheel is not loose. Do this while the bike is sitting upright with weight on the wheels. If it uses nuts undo them enough to be sure that the axle has settled (bottomed-out) into the dropout slots then tighten them quite tight with an open end or preferably box end wrench; an adjustable wrench is not ideal for this job as it may not have good clearance from the fork ends.

If you have quick-release skewers follow these instructions: https://www.bicyclinglife.com/HowTo/UseAQuickRelease.htm

Have you checked the tire pressure? I know that if the pressure is too low, the bike will feel very loose when going around turns and such..

How about a broken axel?

What ever you do, do it soon. Riding with questionable steering/stability is plane wrong.

A visit to your LBS should give you far more info then any one on the internet can. Yes, among the half dozen "answers" there is likely to be the one that is going on but some one still needs to figure out which of the possibilities is really going on. The LBS should be willing to take 5 minutes to look at and diagnose, then talk to you about corrective action, without charging you. Don't expect the shop to tell you how to fix the problems, that's how they get paid.

I like to do the easy stuff first. Air pressure, are things that spin (wheel, fork bearings) moving freely without slop or looseness, are things that need to be tight still tight (stem, bars, seat), doest the front wheel look to be in line with the fork and the rest of the bike and the rear end of the bike need a look at too. If the bike has suspension then that system's condition needs looking at. All this takes only a few minutes if done by an experienced eye. Now the fix might take much longer for all one knows at this point, but information is the first step to figuring out your problems.

Do get back to us with your findings. Andy.