More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation

Mar 30, 17 6:44

Post #1 of 34 (4006 views)

So my project where everything seems to go wrong has hit another hiccup...

I have the front and rear wheels laced (was able to correct spoke lengths) and tensioned

First issue is the rear wheel NDS spokes, the tension is really low on these spokes with proper dishing. I set the DS spokes at 14 on the TM-1 spoke gauge, at this tension the NDS spokes end up @ 7. 50% less then drive side, not really ideal but the fault of the powertap hub geometry.

Here is where it gets weird. When the tire is put on and pumped up. The tension drops off the chart. The DS spokes loose tension to 10 on the meter, and the NDS drops to 2-3. The wheel is obviously soft at this tension, but it stays true. Put the tire off and vola, back to the original tension. I measured a few of my other wheels at home and at most they lost 1 on the meter, often losing nothing.

What the heck do I do now? If I tension the wheel with the tire on I will end up way over the recommended tension of the flo rim when the tire is off (Not something that happens). But I can not ride it like it is.

I google searched this and got too many mixed answers. I trust the brains on this site more.

According to Flo owners manual I should have max. 110kgf of DS and front spokes and 50-90kgf on the NDS. At 14 I was supposedly at 118kgf, and @ 7 I was at 62kgf.

Last edited by: Triagain3: Mar 30, 17 6:55

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 7:09

Post #2 of 34 (3969 views)

Sounds like you have messed up the conversion for your spokes.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 7:13

Post #3 of 34 (3960 views)

1/2 the tension for NDS spokes vs the DS is typical on any rear due to the different bracing angles.

Not sure about the large tension drop with tire mounting though...

http://bikeblather.blogspot.com/

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 7:17

Post #4 of 34 (3953 views)

lyrrad wrote:

Sounds like you have messed up the conversion for your spokes.

Hey, thanks for the reply. I was thinking I might have done that as well. I am using the "Steel Blade .9 x 2.2mm"

If I move to the "Steel Blade 1.0 x 2.0 -2.2mm" I end up being 108 kgf and 57kgf. For DS and NDS. So I was not overtensioned using this conversion. This does not change the massive loss of tension with the tire on.

This is assuming the meter is reading correct.

I have a set of Boyd Wheels at home with the same spokes, if I knew what there spokes were speced at from the factory I could (In theory) test the meter (Assuming they set the spokes properly).I could not find this on Boyd's website.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 7:20

Post #5 of 34 (3946 views)

What spokes are you using?

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Tom A.] [ In reply to ]

Mar 30, 17 7:20

Post #6 of 34 (3946 views)

Tom A. wrote:

1/2 the tension for NDS spokes vs the DS is typical on any rear due to the different bracing angles.

Not sure about the large tension drop with tire mounting though...

It is the tension drop that is the real concern. The wheel felt spongy while riding with the tire on. Should I just true the wheel, then put the tire on, pump it up to my riding pressure (95psi) and then bring the tension up to recommended?

I imagine the guys from Flo will be along in a little bit to provide some guidance.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 7:21

Post #7 of 34 (3942 views)

lyrrad wrote:

What spokes are you using?

Sapim Cx-ray.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 7:28

Post #8 of 34 (3926 views)

Triagain3 wrote:

Tom A. wrote:

1/2 the tension for NDS spokes vs the DS is typical on any rear due to the different bracing angles.

Not sure about the large tension drop with tire mounting though...

It is the tension drop that is the real concern. The wheel felt spongy while riding with the tire on. Should I just true the wheel, then put the tire on, pump it up to my riding pressure (95psi) and then bring the tension up to recommended?

I imagine the guys from Flo will be along in a little bit to provide some guidance.

Just curious, but is it one of the original Flo alu/carbon wheels, or one of the newer all-carbon models?

http://bikeblather.blogspot.com/

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 7:28

Post #9 of 34 (3924 views)

The park meter applies quite a lot of pressure to measure spokes.
This makes it read high on very thin spokes like Xrays.
It applies so much pressure to read that it actually increases the tension.
There is a specific fudge factor for those spokes lurking in forums and websites.
Couldn't be bothered googling it for you, but now you know you can go chase it.

Pull em tight, when you think they are too tight, you are getting close.

There are much better gauges out there for those type of spokes, usually a variation on Jobst Brandt design he talks about in his book. They use a different principle and are almost immune to spoke type or gauge within reason.
Wheel fanatic do a version.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Tom A.] [ In reply to ]

Mar 30, 17 7:40

Post #10 of 34 (3901 views)

Tom A. wrote:

Triagain3 wrote:

Tom A. wrote:

1/2 the tension for NDS spokes vs the DS is typical on any rear due to the different bracing angles.

Not sure about the large tension drop with tire mounting though...

It is the tension drop that is the real concern. The wheel felt spongy while riding with the tire on. Should I just true the wheel, then put the tire on, pump it up to my riding pressure (95psi) and then bring the tension up to recommended?

I imagine the guys from Flo will be along in a little bit to provide some guidance.

Just curious, but is it one of the original Flo alu/carbon wheels, or one of the newer all-carbon models?

Flo 30 rims. 24h and 20h

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 7:41

Post #11 of 34 (3898 views)

I would start at 15 and see how it goes from there.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 7:44

Post #12 of 34 (3893 views)

So If I am under tensioned with the tire off, would this explain the drop when tire is on?

When I originally built the wheel I had the tension up to 17 on the meter, and it felt right. I was shocked when I saw the tension on the meter was near 150kgf, so I lowered the tension to the recommended values using the meter.

Do I have to worry about cracking these Flo 30 rims? I have washers under the nipples.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 7:48

Post #13 of 34 (3880 views)

With the tire on or off?

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 7:52

Post #14 of 34 (3875 views)

The rims will be fine.
With a clincher, the bead pulls outward a similar amount as the tube pushes inward.
The only difference is that the chord angle inside the tyre is probably around 35 degrees or something (engineering stuff most will not understand so these brackets will do) and it makes the outward pull less than the inward push.

Your spokes are too loose.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 8:03

Post #15 of 34 (3862 views)

lyrrad wrote:

The rims will be fine.
With a clincher, the bead pulls outward a similar amount as the tube pushes inward.
The only difference is that the chord angle inside the tyre is probably around 35 degrees or something (engineering stuff most will not understand so these brackets will do) and it makes the outward pull less than the inward push.

Your spokes are too loose.

My spokes are definitely too loose.
I will crank them up a few notches, and go from there.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 8:06

Post #16 of 34 (3861 views)

lyrrad wrote:

The park meter applies quite a lot of pressure to measure spokes.
This makes it read high on very thin spokes like Xrays.
It applies so much pressure to read that it actually increases the tension.
There is a specific fudge factor for those spokes lurking in forums and websites.
Couldn't be bothered googling it for you, but now you know you can go chase it.

Pull em tight, when you think they are too tight, you are getting close.

There are much better gauges out there for those type of spokes, usually a variation on Jobst Brandt design he talks about in his book. They use a different principle and are almost immune to spoke type or gauge within reason.
Wheel fanatic do a version.

The Park TM-1 meter is a total POS. Among other things, the surface of the aluminum is rough and the nylon "pointer" catches on the surface. To make matters even worse, the bushing that it pivots on is either too sloppy or too tight. There isn't any middle ground. You can take several readings of the same spoke and get different results. I wouldn't trust it at all.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [RZ] [ In reply to ]

Mar 30, 17 8:13

Post #17 of 34 (3847 views)

RZ wrote:

lyrrad wrote:

The park meter applies quite a lot of pressure to measure spokes.
This makes it read high on very thin spokes like Xrays.
It applies so much pressure to read that it actually increases the tension.
There is a specific fudge factor for those spokes lurking in forums and websites.
Couldn't be bothered googling it for you, but now you know you can go chase it.

Pull em tight, when you think they are too tight, you are getting close.

There are much better gauges out there for those type of spokes, usually a variation on Jobst Brandt design he talks about in his book. They use a different principle and are almost immune to spoke type or gauge within reason.
Wheel fanatic do a version.

The Park TM-1 meter is a total POS. Among other things, the surface of the aluminum is rough and the nylon "pointer" catches on the surface. To make matters even worse, the bushing that it pivots on is either too sloppy or too tight. There isn't any middle ground. You can take several readings of the same spoke and get different results. I wouldn't trust it at all.

Agree, I use my ears and fingers.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [lyrrad] [ In reply to ]

Mar 30, 17 8:37

Post #18 of 34 (3809 views)

Anything to note if I crank the tension too high?

The hub and the spokes can handle way more tension then Flo recommended for their rim, so I wonder what I will see if I go to far.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 9:06

Post #19 of 34 (3791 views)

I may have missed your original post, where it talks about the specific parts you're using.

But, FWIW, on my Flo 30 wheels, the DS tension is between 16 and 18 with a Park tensiometer.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [rijndael] [ In reply to ]

Mar 30, 17 9:15

Post #20 of 34 (3782 views)

rijndael wrote:

I may have missed your original post, where it talks about the specific parts you're using.

But, FWIW, on my Flo 30 wheels, the DS tension is between 16 and 18 with a Park tensiometer.

Thanks, that is great information.
Is that with Sapim CX-ray spokes? Factory built?

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 9:17

Post #21 of 34 (3779 views)

>CX-ray spokes? Factory built?

Yes

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [rijndael] [ In reply to ]

Mar 30, 17 9:34

Post #22 of 34 (3760 views)

Thanks a ton.

I am obviously under tensioned, that was known well before this info, but it is good to know a ball park idea on where I can go.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 9:58

Post #23 of 34 (3732 views)

A couple of questions.

1. Are you using washers?
2. Do you see any cracks at the spoke bed of the rim?

Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Canadian] [ In reply to ]

Mar 30, 17 9:59

Post #24 of 34 (3729 views)

Yes.
Sapim polyax washers with Sapim polyax spokes.

No change at the spoke bed.

Re: More wheel issues, Powertap GS, and Flo Rims. Massive Spoke tension drop with tire inflation [Triagain3] [ In reply to ]

Mar 30, 17 10:04

Post #25 of 34 (3723 views)

Triagain3 wrote:

Yes.
Sapim polyax washers with Sapim polyax spokes.

No change at the spoke bed.

Ok. Those were some obvious ones for me. If you're using washers and have no spoke bed damage that clears that area of concern. I'd second that the park tension meter is terribly inaccurate, which could be part or all of your problem.

Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

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