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I bought a road bike about 6 weeks ago, but I just only realised it now that at the end of my pedaling (when either foot pushes down), I can feel a bit of a drag/friction/grinding on either pedal. I don't know what's the cause. It just feels unsafe, like something's about to come lose.

The closest thing to describe this friction/grinding feeling is if you imagine going on to a grated bridge. It feels like that.

I noticed that I only feel this at high speed and high gear (about 20+kmph and ~50 cadence). I can't pin point what's causing this because I can only feel it when I'm travelling at high speed and so it is really hard to try to look to see what's the cause.

Is it "normal" to feel this "friction/grinding" at high speed. This is my first road bike so I'm not too familiar on what's "normal".

Could it be due to low/high tire pressure? The tire says 130 PSI... but my pump gauge is broken so I just put as much air as I can and as much as the tire can take before it won't take anymore (using my body weight to pump the last few inches of air into it).

What should I be looking for to troubleshoot this problem?

Update

I've put the bike on an indoor trainer. I took off the pedals and then apply pressure to the cranks by hand. I can still feel a "grinding". So not the pedal.

I then took the chain off to see if it's somehow related to the chain tension. I spun the crank slowly, and I can feel a slight grind - not very noticeable, but it has the same rhythm of the grind when pressure is applied. So it's not the chain tension, it has something to do with the crank.

That is, the grind is more noticeable when pressure is applied to the crank. It might have something to do with the bearings of the crank. But because this is a new bike, I'm questioning if this is suppose to be normal and whether I should put up with it?

When you spin the crank should it be completely smooth without any noticeable grind? If so then I need some tips to rectify this problem because I've never worked with a bike before.

More update

After weeks of inquisitively monitoring the bike, and doing bits of adjustments. I re-greased the pedal bearings, which helped. I can only feel the vibration slightly at high speed and when applying pressure. Not as bad as before. It appears that the pedal bearings were either too tight or too loose which caused a vibration when pedaling. Now the problem still persist, but slightly less so than before.

I cannot regrease the bottom bracket bearings because it is a Shimano Hollowtech and so would mean I have to buy a new bottom bracket if it is the cause.

However, I've done more research and found that the wheels can be out of "true" and cause a wobble/vibration when riding at high speed. I spun the wheels and monitored the brake calipers. My back wheel is definitely way out of true. It appears to be rocking from side to side about 1mm apart. So I've ordered a spoke wrench which should arrive in a week or two in hope to "True" the wheel to fix the problem. Will update when I've trued the wheel.

BTW, I've learned my lesson not to buy anything bulky/expensive online, because it's hell when something goes wrong.

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    It's hard to say what you're describing, with such a vague description. You say you're pedaling "at high speed", but what is your cadence (pedal RPM)? If you are in too high of a gear (with cadence blow 70-80 RPM) then the pedal will seem "stiffer" near the bottom of the stroke simply because you have less leverage there. As to your tires, your pump might top out at 150psi, or it might top out at 80 -- there's no way to tell from here (though generally the gauge scale will go to nearly twice the practical pressure). You need to get a decent pump with built-in gauge. – Daniel R Hicks Nov 13 '16 at 13:01
  • Please see updated question - I changed the description to "grinding" because it feels like something is grinding (like when your bike is grinding on a grated floor). I don't know how else to describe it but it may very well be the bearing of the crank. Not very noticeable without pressure. But when pressure is applied especially at high speed and high gear, the grind becomes 10 fold more noticeable. – chaser Nov 13 '16 at 22:38
  • Sounds like the bottom bracket then. If you bought your bike from a bike shop, then I'd recommend that you take it back and ask them to service it. – rclocher3 Nov 13 '16 at 23:05
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    A bottom bracket, even a well-used one, should turn with silky smoothness, even under load. – Daniel R Hicks Nov 13 '16 at 23:17
  • Unfortunately I bought online and to get it serviced by them I have to drive 2 hours away. Alternatively I can get it serviced by the LBS for a sizeable fee even if it's just a clean up job of the BB. I might buy some tools myself (I figured I need to learn to do this in the long run anyway) and look up some tutorials and report back if the issue is resolved. – chaser Nov 14 '16 at 23:50
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I would say: pedalbearings? Seems that when you apply pressure, the bearing gets pressurised, causing this "rough" feel.

  • Thanks, you gave me an idea to isolate the problem to pedal. So I removed the pedals, and I can still feel the grind. Please see updated question. – chaser Nov 13 '16 at 22:40
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Sounds like the bottom bracket bearings are worn or failing. The bearings could be pitted or have become oval over time giving you a tighter/rougher feel in the pedaling stroke. This will become worse as time goes on, so a new bottom bracket is advisable.

  • If the bike was bought new just six weeks ago (which is not clear), there is no way there should be a worn bottom bracket. It could be a garbage bottom bracket. – Kaz Nov 22 '16 at 21:49
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If there is a grinding in the crankset with the pedals and chain removed, it most likely looks like you bought a bike with a bad bottom bracket. Modern bottom brackets are sealed cartridge units which turn smoothly with no grinding or free play (due to preload). Any grinding means that there is debris inside the cartridge (such as metal shavings), or poor quality balls (not almost perfectly spherical with a ridiculous tolerance, as bearing balls must be) or imperfections in the bearing surfaces over which balls roll.

But, one small thing check for is: are any of the chain rings coming into contact with the chainstay member of the bike frame? That would cause grinding; you'd be surprised at how you can miss this kind of detail if your focus is somewhere else. Rings rubbing on the frame would be caused by installing the crank on a bottom bracket with too short a spindle length for the frame: incorrect "chainline".

If a ring which is on the verge of touching the frame is slightly out of true, then you can get an inconstant rubbing when when a few teeth make a light contact with the frame, once per revolution; you would feel a light grinding on the bike stand, which might get worse with frame flex (actually pedaling the bike under load).

This rubbing issue is in fact more likely to happen on a road bike, like yours, when the crankset has only two rings, because the inner ring closest to the frame is large (often 36T or more; e.g 52-39 setup). With a triple crank (some road bikes, most mountain bikes and hybrids), it's less likely for this rubbing to occur even with a spindle that is too short, because the inner ring is much smaller: as little as 22T up to around 28T.

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A grinding feeling can be caused by all sorts of things. It could be a chain in need of lubrication or replacement, damaged rear derailleur pulley wheels, bottom bracket bearings grinding, lose cranks causing the innermost chainring to rub on the chainstay, misadjusted front derailleur rubbing against the chain, misadjusted rear derailleur, the tire intermittently rubbing or something else.

To begin, move the chain out of the way so that it is disconnected and not interfering with movement of the cranks. If there's still grinding without the chain attached then it's probably somewhere with the cranks, chainrings and bottom bracket. Are the cranks firmly attached to the bottom bracket spindle and do they move together if wiggled? If not only of your cranks may be loose and if it's the drive-side the chainring could be rubbing. If you wiggle the cranks do they move in any way other than the spinning that they're supposed to do? That would mean that you very likely have a problem with your bottom bracket.

If the chain needs to be attached for the grinding, is the upper pulley of the rear derailleur causing strain on the chain against the sprockets on your cassette or freewheel? That would mean you should adjust your rear derailleur. Does it matter which gear you're in when you experience the grinding? If the gearing matters, do you notice any rubbing of the chain specific to that gear, for example against the front derailleur cage?

If the gearing doesn't matter, does each link of the chain move freely or do some bind? It's possible that some links could be roughly passing through the rear derailleur or elsewhere and causing a grinding sensation. Does the grinding happen only when pedaling forward (i.e. the wheels are turning)? If so, does any part of the wheel or tire rub against the bicycle?

  • Op clarified that the problem reproduces when turning the cranks by hand, with chain and pedals removed. – Kaz Nov 22 '16 at 21:52
  • @Kaz to clarify I can only slightly feel the rolling vibration when it is off the chain. I cannot be certain that the chain/backwheel isn't the cause. The problem definitely radiates more when the chains are attached and on high speed. Just an update, I found my backwheel to be out of 'true' and rocking from side to side so I'm looking to fix that to see if it is the problem before looking at the bottom bracket, because the bloody thing needs to be replaced all together due to it being a Shimano Hollowtech. – chaser Nov 26 '16 at 0:40
  • If you feel it with no chain on the crankset, how can it be the back wheel? Though by all means debug your back wheel for a potentially separate, parallel problem. :) Also note that a wheel-out-of-true problem will not be synchronized to the pedaling cadence. – Kaz Nov 26 '16 at 3:20

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