why are my rear spokes pinging on 12%+ climbs?

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emotive
Posts: 124
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

After some advice. I have a set of Flyweight RM29C06 Light Bicycle rims laced to DT240S hubs with 28 x Sapim CX Ray spokes.

When I'm standing up, climbing grades of 12% or more, the rear spokes make a pinging or creaking sound. As the grade lessens, the pinging stops. Tension feels good when I do a basic check with my fingers.

I have ridden 4,500km on theses wheels.
I weigh 77kg
I am running Compass 44mm tyres tubeless at 30psi. I read in another thread here that tubeless tyres reduce spoke tension. Could that be the cause of the pinging?

alcatraz
Posts: 1798
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Is it friction and movement at the crosses perhaps? Try lubing and testing.

It's not a solution but I mean for failsearching purposes.

That's a 280gr rim with 90kg ride weight limit. Do you weigh under 80kg? Edit: yes

Still it's possible the rim is too flexy for the amount of torque you are asking it to handle. Being a disc brake rim maybe it's softer as the resin is low temperature and possibly carbon type too.

How about a picture of the nipples and spokes going into the rim. Trying to see the drill angles.

A pic or two of the wheel can help too.

I used to get pinging spokes on a light kinlin xr200 build, climbing 10-20% grades with improper gears where I occasionally had to put big watts standing up at slow cadence into the wheels. It's simply too much torque for the wheel. It's not torsionally stiff enough to handle that torque. Either swap gears to increase cadence, or maybe get a hub with larger PCD, or increase your crosses to 3x.

My wheel was laced 2x:0x. I'd try 2x:2x or 3x:2x to improve the spokes ability to handle torsional loads. If you have a straightpull hub there is no way to change this unfortunately.
Last edited by alcatraz on Mon Feb 04, 2019 3:52 am, edited 1 time in total.

by Weenie


fogman
Posts: 841
Joined: Fri Oct 30, 2009 10:36 pm

by fogman

This also happened to me. Try adjusting the upper limit screw on the rear derailleur. The derailleur might be adjusted slightly too far inward, thus pinging the spokes when the wheel flexes due to the higher torque when climbing.


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It's all downhill from here, except for the uphills.

NickJHP
Posts: 218
Joined: Wed Feb 14, 2018 2:22 am
Location: Canberra, Australia

by NickJHP

I have a pretty similar rear wheel (240s 28h disc hub, CX-Ray spokes built x2), except that I used the Light Bicycle RRU25C02 rim (nominal rim weight 405g), and I'm running Compass Bon Jon Pass 35mm tubeless tyres inflated to 55psi on the rear. I haven't noticed any noise similar to what you describe, and I've ridden them up quite a few ascents where I'm climbing out of the saddle at gradients of 15% or more. I weigh 65kg, and I tensioned the drive side spokes to 135kgf when I built the wheel. The drive side tension drops about 15kgf with an inflated tyre installed, and that happens regardless of whether the tyre is tubeless or with a tube.

ka3
Posts: 8
Joined: Wed Jun 20, 2018 11:14 am

by ka3

My wheel builder suggested that we use CX ray on NDS and CX sprint on DS due to possible pings.

Wysłane z mojego LG-H870 przy użyciu Tapatalka


none
Posts: 97
Joined: Mon Dec 17, 2018 11:29 pm

by none

This pinging occurs on every pedal stroke at certain location of the crankarm or just constant pinging as the wheel spins?

MikeD
Posts: 196
Joined: Thu Dec 11, 2014 9:55 pm

by MikeD

Do you have outside pulling spokes? If so, the crossed point gets pulled towards the derailleur cage when in low gear. Kinda sucks if so, and the wheel should have been laced inside pulling.

emotive
Posts: 124
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

alcatraz wrote:Is it friction and movement at the crosses perhaps? Try lubing and testing.

It's not a solution but I mean for failsearching purposes.

That's a 280gr rim with 90kg ride weight limit. Do you weigh under 80kg? Edit: yes

Still it's possible the rim is too flexy for the amount of torque you are asking it to handle. Being a disc brake rim maybe it's softer as the resin is low temperature and possibly carbon type too.

How about a picture of the nipples and spokes going into the rim. Trying to see the drill angles.

A pic or two of the wheel can help too.

I used to get pinging spokes on a light kinlin xr200 build, climbing 10-20% grades with improper gears where I occasionally had to put big watts standing up at slow cadence into the wheels. It's simply too much torque for the wheel. It's not torsionally stiff enough to handle that torque. Either swap gears to increase cadence, or maybe get a hub with larger PCD, or increase your crosses to 3x.

My wheel was laced 2x:0x. I'd try 2x:2x or 3x:2x to improve the spokes ability to handle torsional loads. If you have a straightpull hub there is no way to change this unfortunately.
Image

I think the spoke hole angles look OK. I think it may just be flexing as you suggest. I’ll try a larger cassette and keeping cadence higher



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emotive
Posts: 124
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

fogman wrote:This also happened to me. Try adjusting the upper limit screw on the rear derailleur. The derailleur might be adjusted slightly too far inward, thus pinging the spokes when the wheel flexes due to the higher torque when climbing.


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Thanks for the suggestion. Clearance looks fine and ita happening in gears other than the earliest gear, so I think it’s the spokes creaking against one another.


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emotive
Posts: 124
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

none wrote:This pinging occurs on every pedal stroke at certain location of the crankarm or just constant pinging as the wheel spins?
Yes, in a certain location, on the downward stroke, when the torque is highest.


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emotive
Posts: 124
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

ka3 wrote:My wheel builder suggested that we use CX ray on NDS and CX sprint on DS due to possible pings.

Wysłane z mojego LG-H870 przy użyciu Tapatalka
Maybe replacing the Drive Side spokes with CX sprint will be a cheap fix for more stiffness?


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alcatraz
Posts: 1798
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Do you have more pictures of the wheel? Hard to see anything in this pic...

bm0p700f
in the industry
Posts: 4656
Joined: Sat May 12, 2012 7:25 pm
Location: Glermsford, Suffolk U.K
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by bm0p700f

If the cause of the pinging is flex then you are getting alot of flex and spoke failure through simple fatigue will happen sooner. That wheel may need thicker, stiffer spokes. My advise use a ticker spoke both sides. Dont waste your with thicker spokes one side thinner the other. You need to stiffen the wheel up that mean thiocker spokes all round. stiffer wheels are more reliable wheel. Fuzzy logic by some says other wise but you might as well argue the world is flat.

Geoff
Posts: 5252
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

Check the hub flanges, too. I have broken a number of DT240 flanges and I am much lighter than you...

by Weenie


emotive
Posts: 124
Joined: Tue Nov 01, 2016 10:40 am
Location: Melbourne, Australia

by emotive

alcatraz wrote:Do you have more pictures of the wheel? Hard to see anything in this pic...
Day time photos:

ImageImage

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