Metallic 'catching' noise when 'grinding' or standing on pedals?

[Sloth]

I have recently had my bike converted from a 105 2x to a GRX 1x. All is well so far.
However, since I collected it from the shop I have only ridden it a couple of times, most recently yesterday, when, for the first time since the conversion.

I have noticed 2 things, which may be very minor and easy to fix, possibly even just 'teething' problems since the conversion.

1/ When I stood on the pedals to 'grind' up a hill. (I have done this on this hill many times with no issue on the old set up), I noticed a metallic scraping or catching noise when I stood on the pedals, in time with my pedal strokes (roughly).
I tried it several more times on that ride, and even stood on the pedals on the flat near home, all with the same resulting noise.
It is fine when sitting and pedalling normally though, so perhaps something to do with the additional load when stood on the pedals to push up a hill etc?
Could this be my rear disc catching on the pads, due to frame flex? It didn't do it before though.

2/ The new GRX812 front and rear 42t/42-11 set up is great, and gives me all the gears I need personally. However, despite being very smooth to change, I have noticed a hesitancy/delay to change down from the 3rd smallest rear cog, to the next largest up (not up to a smaller cog). I have (at the suggestion of the LBS) turned the gear selector cable tension a 1/4 turn tighter, then another 1/4, but although it seems a little better, it has still got that intermittent hesitancy to change, at that same point only. It changes fine with any other selection. If I turn the cable tension any more could I cause issues with the gears trying to change on their own? Since making the cable tweaks, it already felt like it 'slipped' or tried to change on its own on one occasion, but it was only once....so far.
For information, I am using the 105 flat bar shifter as I am advise that it will work fine with the GRX.

I will of course speak to the LBS again, as they may need to make some adjustments, as they were the last ones to remove the rear wheel and work on the bike.
However, it would be good to get your opinions and see if these are just minor issues, easily resolved by myself?

Thanks in advance.

 

[Specialeyes]

My money's on frame/fork flex causing brake rub. See if you can induce the noise by standing up and pushing hard, then lightly apply the brakes under the same load and see if the noise stops.

 

[Ian H]

My money's on frame/fork flex causing brake rub. See if you can induce the noise by standing up and pushing hard, then lightly apply the brakes under the same load and see if the noise stops.

Or chainset flex and rubbing between chain/chainring/front mech.

 

[ColinJ]

Or chainset flex and rubbing between chain/chainring/front mech.

Normally, yes, but this is now a 1x so no front mech!

I get a similar sound on my 1x Planet X Devon bike. I know it is the front disc brake rubbing because I can stop it by adjusting the pads to be further from the disc but I don't like how far I then have to pull the brake lever. I compromise with a fairly long lever pull, still good braking, quiet most of the time.

 

[Sloth]

My money's on frame/fork flex causing brake rub. See if you can induce the noise by standing up and pushing hard, then lightly apply the brakes under the same load and see if the noise stops.

This is my suspicion also. I’ll try applying the brake next time and see.

 

[Sloth]

Or chainset flex and rubbing between chain/chainring/front mech.

As above, this is how a 1x.

 

[Sloth]

Normally, yes, but this is now a 1x so no front mech!

I get a similar sound on my 1x Planet X Devon bike. I know it is the front disc brake rubbing because I can stop it by adjusting the pads to be further from the disc but I don't like how far I then have to pull the brake lever. I compromise with a fairly long lever pull, still good braking, quiet most of the time.

So can I increase the distance between the disc and pads via the cable adjustment on the brake lever?

 

[Sloth]

Spoke to the LBS, they are going to check it out and sort it on Thursday.

 

[ColinJ]

So can I increase the distance between the disc and pads via the cable adjustment on the brake lever?

I have BB7 brakes on my bike. The position of each pad can be adjusted in and out by adjusting rotary controls at the calliper.

The way I do it is first to get the calliper assembly in the right place...

Set the rotary controls about halfway between their limits. Loosen the bolts holding the assembly, apply the brake, then tighten the bolts with the brake still applied. That should have moved the assembly to a sensible position and fixed it there.

Next adjust the static pad as close to the disc as you can without it rubbing when you spin the wheel.

Finally adjust the other pad in so you get full braking power about halfway through the lever travel. You don't want to have to pull it right to the handlebar!

That should give a good effective braking action but you may get that rubbing noise when making big efforts on the bike. If so, adjust the pads slightly further from the disc.

As I said above - it can be a compromise. I managed to keep a very good brake action with only the occasional rubbing sound.

 

[ColinJ]

And I have just noticed that the bike shop is going to do it for you...

Never mind - someone might find that advice useful!

 

[Sloth]

The LBS have requested that I don't do any more 'tweaks' until they've had a look
Still useful information though.

 

[livpoksoc]

Just one thought - could the grinding/rubbing be your shoes catching the chainstays? When grinding uphill, you may be dancing the bike left to right a bit and just catching your heels. I found this with several bikes, though the sound wasn't all that loud, but the markings left on my inside heel confirmed it.

I have also previously fixed a metallic noise when out of the saddle by applying some ceramic grease to my front wheel axle/qr skewer, where the fork and wheel were under different directjonal loads when standing vs seated.

Just a thought. Might be very wrong.

 

[Sloth]

Thanks, I’ll mention it to them at the LBS on Thursday.

 

[Sloth]

Well I’m back from the LBS.
They and I tried the bike and it would not make that noise, no matter what we did. Up and down the road, round the block high gear, low gear, standing on pedals and not.
Also the gear change hesitancy from second smallest to third smallest also did not happen. I’m sure I heard the bike sniggering at me!
So long as it doesn’t do it again in my next ride I’ll take that, but I have an uneasy feeling I’ve not heard the last of it.

 

[Sloth]

The only thing that has been loosened and refitted is the front wheel.
Could I have perhaps over tightened the front wheel when refitting it after getting the bike out of my car? (It’s a straight through front wheel bolt).
If I did, could that account for the noise when stood on the pedals grinding, as in from my front disc rather than back?