Sudden sharp bang query?

Maidhci · 25-08-2014 11:53am #1

While out for a cycle on Saturday, cycling at a nice pace (30km. approx) on a road bike, I heard a sudden sharp bang coming from what appeared to be the chainring area - it was a one off, not creaking but something similar to a part breaking off or the noise that a loose chipping makes when it hits off the bike while travelling at a fast pace etc. but it was not the latter. It was after changing gears etc. but the gear changes are very smooth and everything appeared normal after that. I have checked insofar as I can to see if any part is loose or has come off, checked the spokes, chain etc. Obviously, I am very worried about this but am not in a position to take it to a bike shop before I hope to do my next cycle. Any suggestions on what else to check or look out for would be appreciated. Many thanks.

Beasty · 25-08-2014 11:59am

Are you sure there's no damage to the frame (what's the material?). Also have you taken the chainring off and checked the bottom bracket?

Al Wright · 25-08-2014 1:05pm

It could possibly be chain slap on the chainstay, quite common (hence chainstay protectors). Look for chip/mark on the chainstay surface (inside and underneath)

Alek · 25-08-2014 1:10pm

Maybe the front tire picked a small stone from the road and shot it into your drivetrain?

Maidhci · 25-08-2014 1:11pm

Thanks for your response - I have only carried out a visual inspection and all appeared to be fine on that score. Apart from the usual cleaning and lubing, I am not very experienced at repairs etc. The bike is a Canyon Ultimate AL 9, I have checked the frame for damage and there does appear to be any but I have not taken off the chainring to check the bottom bracket, I think I would feel more comfortable to leave that aspect to a bike mechanic.

I presume you may be thinking that it might have been a chip hitting off the frame which seems like an obvious cause but although it seemed to be a similar type bang it was obvious to me at the time that it was not the case - perhaps I have not described it very well. If it were a bottom bracket issue, do you think that it would only be a one off only or would there be a continuing issue that would have become more apparent on the remained of the cycle home?

joxerjohn · 25-08-2014 2:41pm

Given that your frame is aluminium you can rule out some kind of structural cracking in the "carbon" frame. I would suggest taking off your wheels and checking that the welds and joints around your bottom bracket and stays are sound and don't have any visible cracks. Also ensure that nothing is loose or has any play with the pedals and BB. If all checks out I would say there is no obvious cause and you should be fine. As you were changing gear the sound could have been related to that but I would say its a one off.

CramCycle · 25-08-2014 3:50pm

Check your spokes as well (are any noticeably loose/easily squeezed out of position), rare enough but if one came loose suddenly, it could make a noise like that and you would not notice any immediate change to ride quality.

victorcarrera · 25-08-2014 5:49pm

Are you sure it wasn't just the sound of the front mech changing from big to small chainring. Try it while stationary and compare.

Maidhci · 25-08-2014 5:59pm

CramCycle wrote: »

Check your spokes as well (are any noticeably loose/easily squeezed out of position), rare enough but if one came loose suddenly, it could make a noise like that and you would not notice any immediate change to ride quality.

Checked the spokes and all are OK.

Maidhci · 25-08-2014 6:00pm

victorcarrera wrote: »

Are you sure it wasn't just the sound of the front mech changing from big to small chainring. Try it while stationary and compare.

Absolutely certain....I wasn't changing the front chainring at the time.....know that noise from a previous bike...it was much much more defined, sudden and sharp.

Type 17 · 25-08-2014 6:21pm

If you were pressing hard on the pedals, it could have been the bottom bracket assembly shifting in the frame a bit (this would happen if it was tight, but not tight enough).

Test it by holding the bike from the side, leaning away from you, and with the pedal on your side at six o'clock - press the pedal away from you with your foot (the force across the frame) and see if you get a click or popping noise. If not, swap sides and backpedal the cranks back ,so the pedal on that side is at the bottom, and do it again (so the force is going back the other way).

If there's no noise, it's unlikely to be the BB.

Maidhci · 25-08-2014 6:25pm

Type 17 wrote: »

If you were pressing hard on the pedals, it could have been the bottom bracket assembly shifting in the frame a bit (this would happen if it was tight, but not tight enough).

Wasn't pressing hard on the pedals at all at the time....was travelling at a nice steady pace on a relatively flat surface. Believe me, I am hoping it was something that was not too serious but am very puzzled.

Type 17 · 25-08-2014 6:27pm

Maidhci wrote: »

Wasn't pressing hard on the pedals at all at the time....was travelling at a nice steady pace on a relatively flat surface. Believe me, I am hoping it was something that was not too serious but am very puzzled.

Fair enough, but try the test above anyway (only press hard enough to deflect the frame a little, but don't worry, you won't break anything unless it was knackered anyway, or you're Mr Universe).

Gerry T · 25-08-2014 6:34pm

Would you have cycled over something on the ground that made the noise--like a crisp bag with air/water inside

sham58107 · 25-08-2014 6:44pm

Would bb not have showed a lot more noise on your way home if it goes, it goes but usually loosens.
Did you check chain could it have been a stiff link popping? or a bit off grit stuck in chain being ejected.
Does not sound too bad if it was a once off.

Maidhci · 25-08-2014 6:46pm

Type 17 wrote: »

Fair enough, but try the test above anyway (only press hard enough to deflect the frame a little, but don't worry, you won't break anything unless it was knackered anyway, or you're Mr Universe).

Thanks Type, but in all probability if that were the case it would have persisted on the remainder of the cycle home approx 30km., some of which was uphill.

Maidhci · 25-08-2014 6:47pm

Gerry T wrote: »

Would you have cycled over something on the ground that made the noise--like a crisp bag with air/water inside

No, definitely not, it was more sharp and pronounced than that.

Maidhci · 25-08-2014 6:51pm

sham58107 wrote: »

Would bb not have showed a lot more noise on your way home if it goes, it goes but usually loosens.
Did you check chain could it have been a stiff link popping? or a bit off grit stuck in chain being ejected.
Does not sound too bad if it was a once off.

I checked the chain at the time and again after I got home and nothing appeared out of the ordinary. I thought at the time that the chain had popped. The chain was was well lubed and very clean but as you say it could have been some grit being ejected but it sounded much louder than that at the time. I will have to examine the bike again when I get an opportunity tomorrow.

Gerry T · 25-08-2014 7:11pm

Maybe it was a stone that got caught in the rear cassette and it got "flicked" out after you changed gear. Checking all joints, top and bottom, on the frame would be a good idea but hopefully its just a once off. Also best to check the wheel spindle and axle for any signs of hair-line cracks while your at it. Like the test on the BB mentioned above, there should be on play on your wheels--so make sure there is no possible lateral movement.

Maidhci · 29-08-2014 10:27pm

Many thanks for all your helpful suggestions and advice here - much appreciated. I have carried out all the checks, visual and otherwise that have been suggested here and thankfully all appear to be in order. Hoping to do a 120k. cycle on Sunday and will see how it goes. Thanks again.

Sudden sharp bang query?

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