Zipp 303 Firecrest disc - Are they too flexible?

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pmprego
Posts: 2513
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

Hello all,

Owner of a pair of zipp 303 Firecrest disc (the hookless ones) here.

The situation: every time I push a bit harder out of the saddle (im talking 700w - not crazy sprinting numbers) I can hear the disc rotor "ping ping". I only hear it when doing those type of efforts (seated it does not happen - I have to put the front wheel going side to side) and when swapping to a pair of aluminium training wheels it doesn't happen either. Thus, I can confidently say that the slight "ping ping" comes from the wheels.

Question: is this normal in these wheels? Should I take them to the store for them to check spoke tension (they seem true to me)?

I can for sure say that this "ping ping" happened when the wheels were brand new. I also had one event where I put my front wheel on a train rail and almost fell down. Since then, I can hear sometimes the metallic sound of spoke tension being released.

Thanks for your help!

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bmrk
Posts: 185
Joined: Sat Feb 18, 2023 4:03 pm

by bmrk

This is much more likely to be the frame rather than the wheel (the hub in this case) flexing. Is actually common in some frames due to less stiff chainstays/bottom bracket area.

Lack of good alignment of the calliper or an untrue rotor can also amplify the problem.

Which frame? Which brake calipers and rotors?
Last edited by bmrk on Mon May 08, 2023 2:29 pm, edited 2 times in total.

bmrk
Posts: 185
Joined: Sat Feb 18, 2023 4:03 pm

by bmrk

.

pmprego
Posts: 2513
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

bmrk wrote:
Mon May 08, 2023 2:09 pm
This is much more likely to be the frame rather than the wheel (the hub in this case) flexing. Is actually common in some frames due to less stiff chainstays/bottom bracket area.

Lack of good alignment of the calliper or an untrue rotor can also amplify the problem.

Which frame? Which brake calipers and rotors?
As I've mentioned: I have a set of training aluminium wheels that do NOT make this happen. A slightly more untrue rotor could promote that, indeed. To the naked eye, the rotors seem OK.

Still...brakes and rotors are sram red. Frame is scott addict rc.

timmerrr
Posts: 217
Joined: Wed Sep 26, 2018 10:09 pm

by timmerrr

pmprego wrote:
Mon May 08, 2023 3:09 pm
bmrk wrote:
Mon May 08, 2023 2:09 pm
This is much more likely to be the frame rather than the wheel (the hub in this case) flexing. Is actually common in some frames due to less stiff chainstays/bottom bracket area.

Lack of good alignment of the calliper or an untrue rotor can also amplify the problem.

Which frame? Which brake calipers and rotors?
As I've mentioned: I have a set of training aluminium wheels that do NOT make this happen. A slightly more untrue rotor could promote that, indeed. To the naked eye, the rotors seem OK.

Still...brakes and rotors are sram red. Frame is scott addict rc.
When I switch between training wheels and my race wheels I get a similar problem, but its not from anything you listed. Your new wheels likely have brand new rotors on them. These new rotors are slightly thicker than the ones on your training wheels. Even if you have the rotors shimmed to the same position. The thicker, new rotors will rub slightly when the frame has a lot of torque going through it because the brake calipers are "set" to the used, thinner rotors on your training wheels. The pad gap to the new rotors is less.

You can spread the pads slightly to accomidate the new rotors. This will create a longer lever throw when going back to the training wheels. Or buy 2 new sets of rotors and rebleed the brakes so they are set up properly for those new rotors.
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pmprego
Posts: 2513
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

I've adjusted the calipers to the race wheels (even though I've them shimmed to be pretty closely they are not exactly the same) but what you've mentioned is definitely a possibility.

bmrk
Posts: 185
Joined: Sat Feb 18, 2023 4:03 pm

by bmrk

There is no possibility for this to be the "wheel" flexing. what you are suggesting is the hub flexing which would also require the frame to flex as it sits on the thru axle clamped to the frame.

OFC it is possible to have tolerance and pre-load issues on the hub which could in theory create some play but these are hard to diagnose and likely to not require out of saddle efforts.

this is usually due to (one or more) difference in caliper alignment for diferent hubs, rotor trueness and yes, the frame flexing as you apply more force out of the saddle efforts.

pmprego
Posts: 2513
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

bmrk wrote:
Mon May 08, 2023 9:53 pm
There is no possibility for this to be the "wheel" flexing. what you are suggesting is the hub flexing which would also require the frame to flex as it sits on the thru axle clamped to the frame.

OFC it is possible to have tolerance and pre-load issues on the hub which could in theory create some play but these are hard to diagnose and likely to not require out of saddle efforts.

this is usually due to (one or more) difference in caliper alignment for diferent hubs, rotor trueness and yes, the frame flexing as you apply more force out of the saddle efforts.
OK. Thks. I'll check the calipers once more. As for the frame flexing not much I can do :)

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LeDuke
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Location: Front Range, CO

by LeDuke

I would imagine it’s the opposite. Stiffer rims will result in flex anywhere besides the rim itself. Hub bearings and axle, for starters.

An aluminum rim/wheel would flex under power at the contact patch.


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AscentBikes
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by AscentBikes

Could you try this:
1) Lift the offending wheel off the ground
2) Try to rock it from left to right by pushing on the rim

The wheel should deflect when you push, but it should be almost linear, like the amount of force is proportional to the deflection.
If you can feel some knocking, that usually means either the preload is off, or the bearings are gone - time for tuning and replacement.

If there is no knocking, and there's still the rubbing sound, damn, your legs are powerful.
Check the pads if they are extended too far. Spread the pads and try again.

-QX

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