Disc brake issues/help please!

[Kiwikid]

Hi, looking for some help with a front disc brake issue.

Situation -
I've got a 2019 Specialized Sworks Venge, Ultegra DI2, Royal CLX64 wheels. Running a 160mm front rotor and 140mm rear rotor. Bike is AWESOME, and I love it.
The problem I have is that with the Roval 64's the front brake makes a lot of noise and the braking is shit, its done it from new. At low speeds its fine, but at high speeds it is terrible and was so bad that when bombing down a 90kmph decent in a race recently - when i applied the front brake the vibrations/noise of the front brake got so bad that i got speed wobbles and ALMOST crashed.
Even weirder, if it starts happening, if i release the brake and reapply it, the noise seems to go away and the braking is great.

Now here is the weird part. If I put in my other wheels, roval 24's the front brake works perfectly and I have no issues at all. I have tried swapping rotors over, I've tired different brake pads. I've tried a completely new rotor and I've tried packing the connection of the rotor and the hub to ensure its a tight fit. Nothing seems to stop the noise and vibrations.
Both my roval wheels have the same hubs.
I've tried realigning the caliber....

I am out of ideas on how to fix this and so are the awesome team at the shop that i brought it from. They have been really helpful.

I have a mate with the exact same frame and wheels and I am going to borrow his front wheel tonight for a ride and see if the same thing happens, but aside from that we are all out of ideas on what could be causing this issue?

Yes the rotors run true on the wheel, I can not spot even the slightest wobble....
I've tried Ultegra and dura ace front rotors, both with the same result.

Anyone got any ideas on what could be causing this?
Thanks
M

[Mr.Gib]

Assuming you have done the same extreme test on the Roval 24, the fact that the 24 is fine tells you that it is most likely a wheel and not a bike issue. Report back once you test your mates wheel. If the problem is still there I would try a completely different rotor as an experiment.

One thing you will have to keep in the back of your mind is that the combination of your body and your equipment maybe such that it sets up a nasty vibration or resonance when you apply the brakes. This is occasionally the cause of mysterious vibrations and wobbles. A different set of wheels may be the only fix.

[RedbullFiXX]

Speed wobbles ?
That sounds more like a hub/bearing issue than a disc issue, though there may be a correlation there
Is the disc centered with both wheels ?

[Kiwikid]

Thanks guys, I've tried a brand new rotor on the wheels, same result.
I've tried an 80kmph decent with the 24's and no issues at all.
Speed wobbles went away when i stopped using the front brake on the 64's.

[ChiZ01]

what is the spoke tension of DS and NDS on the front wheel?

[rollinslow]

Thanks guys, I've tried a brand new rotor on the wheels, same result.
I've tried an 80kmph decent with the 24's and no issues at all.
Speed wobbles went away when i stopped using the front brake on the 64's.

Maybe you should ask the shop to replace the wheelset then. That's pretty convincing that it's a wheel problem. If not a wheel issue I would try to get a warranty replacement rather than drive yourself crazy trying to figure it out.

Sorry, must be super annoying.

[Aeo]

Is the 64 front wheel balanced?

[spdntrxi]

Speed wobbles ?
That sounds more like a hub/bearing issue than a disc issue, though there may be a correlation there
Is the disc centered with both wheels ?

kinda my feeling too..

[Nefarious86]

Spoke tension causing the 64 to dive under load?

Also fair warning that any "Rim brakes don't do this" or other unhelpful nonsense will be deleted and the poster given a weeks holiday.

Sent from my SM-G977B using Tapatalk

[rollinslow]

Spoke tension causing the 64 to dive under load?

Also fair warning that any "Rim brakes don't do this" or other unhelpful nonsense will be deleted and the poster given a weeks holiday.

Sent from my SM-G977B using Tapatalk

Lol. Ugh you had to remove any temptation for us to take over the thread and convert it to disc vs rim

[RedbullFiXX]

Actualy have a friend that had a rim brake bike with a scary wobble he could not solve, ended up parting out the bike, and giving the frame away

[AGB]

This may not be a solution but might point you in a different direction.

I recently acquired a Giant Propel SL 19 model with a dodgy front caliper....the ting ting ting from the hot rotor rubbing the pad pissed me off so much that I started only using the rear brake to avoid that sound - it was starting to drive the weekly bunch riders nuts as well..........after a month or so the rear brake pads were well and truly "bedded in" (nice and grabby) so I thought I would switch the front and rear pads around as the front clearance was so small.......long story short....problem solved....

It might work, it might not work for you, but putting in nicely bedded in pads in the front brake fixed it for me......

Good luck..

[alcatraz]

Check for play on that front wheel. Hold the rim with one hand and try to move it sideways. It should feel solid.

It might be true in a stand but with nearly your full body weight on the front wheel (braking) it could be wobbling because of play in the hub. The rotor might wobble as well.

I don't use disc brakes. Just brainstorming here.

Also check the axle length (distance between endcaps). Maybe something is not the right length so you get play in the system or twist the fork legs when you clamp down the wheel.

[Kiwikid]

Ok so latest update and its more confusing than ever!
So i swapped wheels with my mate, identical bike, frame size, wheel etc.... he had no issues at all with my wheel, I had the same noise and vibrations with his. Tried a Dura ace front wheel, same issues.
Interestingly it looks like the pads are grabbing to low down on the disc rotor, i.e. the rotor is set for something like a 155 diameter disc, not a 160? But the calliper mount is set up for 160... and when you look at it when stationary it all looks like its set up perfectly but for some reason under load it must push into the caliber further than it shout...? Weird!
There are scuff marks on the rotor way to low down than there should be.
I have swapped to a 140mm rotor and gone for a ride and so far no issues.... it still does not explain the issues with the 160mm rotor!
We even had the Shimano rep look at it and he was stumped.
So we have had a Protour mechanic, leading local mechanic and shimano rep and none of us can figure out what the hell is going on!

[Kiwikid]

I should ad, when looking at the rotor on my 24's it does not look like it grabs to far down.... what they hell!?
What could cause a rotor on one wheel to be in a different location to that on another? Identical rotors, identical hubs...