Vibration like feeling while pedaling

[Camus47]

Hey,

Got a fairly new bike, and for the past few rides I noticed this weird vibration (like slightly more and less resistance feeling) while pedaling. Haven't noticed it before much, as it's being apparent only on higher gears while riding fast on a smooth surfaces (more than sure it's there regardless of surface, just being masked by roughness of terrain). I went to a nearby bike mechanic, he gave it a checkup and told me that mechanically everything is all right. He suggested it might be due to chain being more tense on higher gears, and this is just how my cycle is working (agree it's not most expensive high end bike, but it's not that bad either. At least I hope).

Today I had some more time so I cleaned drivetrain, applied fresh lube and checked it again. Vibration is still there, and after putting my bike upside down to check if anything is visibly wrong while wheels are spinning, I could definitively feel it while spinning pedals with my hand. It's way more intense on higher gears, but it's still there on the middle ones. I don't think it's related to the specific sprockets (that's how the gear wheels are called right?), as the transition in intensity of this feeling is smooth rather than a rigid one.

Do you have any idea what might be causing it? I already cleaned everything and even applied fresh grease to the pedals. Should I just go back to the bike shop with it, or I'm exaggerating and this is just how it is? I would just like it to be a smooth ride, not annoying one.

Appreciate any answers.

my bike info:
Bike is Marin Fairfax 1, alloy frame with rigid fork.
DERAILLEUR, REAR - Shimano Tourney, 7-Speed
DERAILLEUR, FRONT - Shimano TY510
BOTTOM BRACKET - Sealed Cartridge Bearings, Square Taper
CHAIN - KMC Z50
CASSETTE - SunRace 7-Speed, 11-34T

 

[Ajax Bay]

Riding along, such vibration is not just an irritant: your bike's trying to tell you something.
Bottom bracket would be my first stab: try displacing the chain off the chain rings (either inwards or outwards), turn upside down if you must, and spin the cranks. Listen and feel. Go to another LBS if they really said it may be because the chain has more tension in the higher gears (for a given force on the pedal there is more tension (higher gear = large chain ring), but most unlikely to be the cause).
A relatively new bike really shouldn't have BB issues (square taper) - well not for 10,000km - however a cartridge BB is inexpensive (<£20) and quick to fit. Given you haven't any tools for it, this is a simple LBS job, which would double(ish) the cost.

 

[jay clock]

tyre not seated fully so you have a slightly oval wheel?

 

[Ming the Merciless]

Tyres overinflated?

 

[ColinJ]

Does it ONLY happen when actually pedalling?

If 'YES', then the problem IS somewhere in the transmission.

If 'NO', then that sounds more like a rear wheel problem. (Dodgy bearings, or a bent disk rotor?)

 

[Ajax Bay]

Vibration is still there, and after putting my bike upside down to check if anything is visibly wrong while wheels are spinning, I could definitively feel it while spinning pedals with my hand.

Tyres overinflated?

And with tyres in air, Ming?

 

[Camus47]

Bottom bracket would be my first stab: try displacing the chain off the chain rings (either inwards or outwards), turn upside down if you must, and spin the cranks.

That's a good idea, it might eliminate the chain/rear wheel as a culprit. Haven't thought about it. Will give it a check in the evening.

tyre not seated fully so you have a slightly oval wheel?

Tyres overinflated?

Tires shouldn't be overinflated (70 psi on the rear, 65 on the front with tires 700c x 35mm) I used online calc to adjust it to my weight. Also it doesn't happen only when I'm riding the bike, I turned it upside down and placed on the bench to have a better look on everything. It did vibrate when I was pedaling it with my hands alone, so with not much weight or force.

Does it ONLY happen when actually pedalling?

If 'YES', then the problem IS somewhere in the transmission.

If 'NO', then that sounds more like a rear wheel problem. (Dodgy bearings, or a bent disk rotor?)

Definitely only when pedaling.

 

[ColinJ]

And with tyres in air, Ming?

Perhaps overinflated to the point where the rear tyre was touching the frame...?

 

[Camus47]

Ok, so I did turn the pedals a little bit with chain displaced, couldn't feel anything but smooth spin. Tbh I wasn't able to put much force into it as there was no resistance, but I don't think there was any weird feeling to the cranks rotating on it's own.

I also observed the rear wheel and cassette while spinning and there was no side movement on the wheel. Cassette however does 'wobble' a little bit when the wheel is spinning, very slight movement from left to right ( around 0.5 to 1mm). Just like it stayed slightly closer to the center on one end of the cassette and slightly further on the other. When immobile I can press down on couple of teeth (sprockets?) on the one side (rear, furthest from the front of the bike that is) of the largest cog, and move slightly to the center of the wheel. It's impossible on the other side. Not sure if it's it, as wobble is there constantly, and vibration is there only when I'm rotating the pedals.

That's all I found.

 

[bikingdad90]

Possibly missing a cassette spacer on the freehub as the cassette should be tight?

 

[ColinJ]

Possibly missing a cassette spacer on the freehub as the cassette should be tight?

I borrowed a bike from a cousin in Scotland and discovered that the spacer was missing. Fortunately, his brother had a spare spacer and put it on for me. It fixed the problem.

 

[Ajax Bay]

No spacers are required for a 7sp 'cassette', slid onto a freehub (7 speed, 8sp freehub is deeper and spacer needed, but this is a newish bike so latter circumstance v unlikely). There is always a tiny bits of 'wiggle' on sprockets: by design: it helps the shifting process. Not sure it's as much as 1mm.
Take the rear wheel out and check the lockring is tight (spec is 40Nm). Unlikely you have the tools but present the wheel (with QR removed) to your LBS and they will tighten it (if needed in seconds).
Biut I do not think this is the likely source of vibration: I cannot envisage the mechanism.

 

[bikingdad90]

@Ajax Bay might be future proofed with an 11speed hub that needs a 1.75mm spacer for 8 to 9 speed or a 1mm for a 10 speed but none for a 11 speed?

 

[Ajax Bay]

It's an excellent Marin Fairfax 1 @dad: no future proofing there.
Worth checking your spacer index btw.
AASSIA (minor edits)
"Hubs marked "8-speed", "9-speed" or "10-speed" will work with any number of sprockets up to 10! (Add a 4.5mm spacer before installing a 7-speed cassette on an 8-, 9-, or 10-speed hub, and the included 1-mm spacer before installing a 10-speed cassette on an 8/9/10-speed hub.) Any of these cassettes will work with an 11-speed hub with the addition of another 0.85mm spacer. 1.85mm spacers are available so a 10-speed cassette will work on an 11-speed hub."

 

[Camus47]

Ok, so finally got time to visit the bike shop today and asked the guy to look into this wobble issue. He told me there is no need for a spacer there, and the amount of said wobble is all right. He told me again not to worry about it, and that it's most likely due to my chain tension on higher gears.

I have a slight feeling, that he's fed up with me at this point. So I'm back to the square one with it. Should I just ignore it and hope it'll go away with more mileage put into the drivetrain? Or should I just try to bother another bike shop about it?

And ywah I don't really want to future proof it or invest a lot to make it some miracle bike. It's a simple little bike for some fitness on my spare time.