Di2 noise and/or discs?

oldgreyandslow

Veteran
Location
Farnborough
I have a new Canyon with Di2 and disc brakes, I've noticed when on the big front/mid to smaller rear range it sounds like I'm over spinning almost like the noise of the freewheel but not quite, and it doesn't seem to happen on the larger rear cassette range. (if that makes sense).

Also after a fast descent I turned hard to sweep around a roundabout and got a sound like the discs were rubbing, completely in time with the wheel revolutions, I tried applying the brakes, changing gear etc and it eventually cleared up.

My first thoughts on the gear problem is that the chain length is too long, no idea on the second though.

Slightly concerned so would appreciate any thoughts/advice/opinions appreciated. I do realise it is difficult to explain problems that involve noise though :-)
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
You can sometimes get dirt on the discs, or they may need aligning better.

Can't help with gears much without video, or pics. Check nothing is rubbing and front mech has been aligned.
 

I like Skol

Hold my beer and watch this....
Check your QRs/Thru-axles are tight. This may quieten both gears and brakes. Other than that, as Fossy said, brake calipers might need a small position tweak and gear noises are difficult to give a meaningful suggestion without seeing/hearing the problem.
 

CXRAndy

Guru
Location
Lincs
Thanks for the suggestions, how tight for the thru axles? Grrrrrrrr tight or not quite so much?
Through axles, dont need to be crushing tight. Turn by hand until they begin to tighten then 1/4 to 1/2 turn to nip.

Same for QR, firm but not so much you need to hammer the lever down

Slightly catching of rotors is due to new pads and little clearance, just ride and the pads will wear a little and stop making noise.

I
usually set my pads up very close and just ride until pads wear down-reduces lever travel
 

I like Skol

Hold my beer and watch this....
I
usually set my pads up very close and just ride until pads wear down-reduces lever trave
Maybe with cable discs. No such adjustment with hydraulic where rubbing means only two things, bad set up or bent rotors. Hydraulic self adjusts for clearance throughout pad wear/life.
 

I like Skol

Hold my beer and watch this....
Same for QR, firm but not so much you need to hammer the lever down
Also not entirely true. IME QR tension affects disc rub as the tension affects frame distortion slight!y as the axle compresses. Even the orientation of the QR lever can make a difference. This is why thru-axles are better, but you still need to be consistent with tension to replicate conditions from when the caliper was set up.
 

CXRAndy

Guru
Location
Lincs
Maybe with cable discs. No such adjustment with hydraulic where rubbing means only two things, bad set up or bent rotors. Hydraulic self adjusts for clearance throughout pad wear/life.
No if you pressurise the system with wafer thin shims you can get close gap and very little lever travel on hydraulic Shimano brakes
 
OP
oldgreyandslow

oldgreyandslow

Veteran
Location
Farnborough
Thanks for the advice, I am back home Thursday so will take the wheel out to inspect the discs and rotor and put it back and then check for clearance/tightness etc. After getting the bike I did loosen the rear thru axle to see how tight it was and it seemed pretty tight, more than the hand and 1/2 turn I ended up going with
 
Location
Loch side.
I have a new Canyon with Di2 and disc brakes, I've noticed when on the big front/mid to smaller rear range it sounds like I'm over spinning almost like the noise of the freewheel but not quite, and it doesn't seem to happen on the larger rear cassette range. (if that makes sense).

Also after a fast descent I turned hard to sweep around a roundabout and got a sound like the discs were rubbing, completely in time with the wheel revolutions, I tried applying the brakes, changing gear etc and it eventually cleared up.

My first thoughts on the gear problem is that the chain length is too long, no idea on the second though.

Slightly concerned so would appreciate any thoughts/advice/opinions appreciated. I do realise it is difficult to explain problems that involve noise though :-)
OK, lets go through this bit by bit.

Firstly, this has nothing to do with Di2. Exactly the same would happen on an an analogue bike as well.
Then for the disc noise. It is very, very common. Forks flex when the bike takes a corner and that flex temporarily takes the fork and disc (hub actually) out of alignment. If the gap is very close to start off with, it will touch and give you audible feedback. That's fancy term for scrape. It is not serious. If the caliper is obviously off-centre, fix that but if that doesn't improve things, get earplugs or go faster so that the wind noise overpowers all else.

Now for the chain noise. Congratulate yourself. Most cyclists are so mechanically unsympathetic that they never notice the subtle changes in noise chains and sprockets make when in different gears. Smaller sprockets sound different to larger ones. The reason is three-fold. Smaller sprockets have different cog shapes (a cog is one tooth on a sprocket) because a smaller radius has the cogs flare outwards and bits need to be chopped off the ends to make them not catch on the chain. Large radii have smaller angles between cog centres and sound different. Secondly, smaller and larger sprockets are laterally distant from each other and that either causes the chain to glide against the side of the cog before engaging or not. Obviously this sounds different.
Thirdly, a smaller sprocket causes the chain links to articulate more than when running on larger sprockets. That, you guessed it, sounds different.

Unless there is an obvious mis-alignment of derailers somewhere, don't worry about different noises in different gears. Consider it a feature to warn you of cross-chaining.
 
OP
oldgreyandslow

oldgreyandslow

Veteran
Location
Farnborough
Perhaps I should have clarified the issues.
It was the rear disc.
I have several non Di2 bikes and know what misaligned gears sound like, and this only happens under load, doesn't rub or look out of kilter when on the stand.
 

CXRAndy

Guru
Location
Lincs
Perhaps I should have clarified the issues.
It was the rear disc.
I have several non Di2 bikes and know what misaligned gears sound like, and this only happens under load, doesn't rub or look out of kilter when on the stand.
You can slightly tweak the indexing to see if its ever so slightly out of alignment
 
Location
Loch side.
Perhaps I should have clarified the issues.
It was the rear disc.
I have several non Di2 bikes and know what misaligned gears sound like, and this only happens under load, doesn't rub or look out of kilter when on the stand.

You keep changing your story. First you were sweeping around roundabouts like Lewis Hamilton and you you were putting your frame under load. Which one is it. Stop saying Di2. It is irrelevant.
 
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