Zipp wheels Stiffness

[nevillec]

Hi, I've upgraded from Mavic Aksium to Zipp 303 + 404 combo (rim brake, firecrest, 2019) for 300+ miles so far.

Comparing to Aksium, sometimes I feel that Zipp is a bit soft when I pedal hard or go uphill (e.g. 4+ w/kg). Is this normal? - I'm not a heavy ride.

[Pinguin]

Hi, I've upgraded from Mavic Aksium to Zipp 303 + 404 combo (rim brake, firecrest, 2019) for 300+ miles so far.

Comparing to Aksium, sometimes I feel that Zipp is a bit soft when I pedal hard or go uphill (e.g. 4+ w/kg). Is this normal? - I'm not a heavy ride.

How do you feel this?
Is rim touching pads?

[bm0p700f]

the OP will be confusing brake rub with lateral wheel stiffness. brake rub is related to the ratio of rim to spoke stiffness. The stiffer the rim without beefing up the spokes make rub more likely event thought the wheel can be stiff.

The Zipp wheels are not soft you just need to sit down and rock the bike less.

[nevillec]

Thanks dudes. I'm quite sure that there was no brake rubs during my rides.

I think I'm talking about the rotational stiffness of the rear wheel. Maybe I should ride more miles before making any verdict.

[AJS914]

Rotational stiffness??

Maybe you are noticing deflection?

[LouisN]

Soft when pedalling hard/uphill ? What tires ( brand/model/ size) do you have, both on the Aksiums, and Zipps ?

Louis

[nevillec]

GP5000 on Zipps and GP4000S ii on Aksiums. I use 100psi on both wheelset.

But I did have 3 sneaky puncture within 300 miles on the Zipps
I only got 3-4 puncture on the Aksiums for 5000+ miles.

[LouisN]

All same size (23-25 mm ? ) ?
If 25 mm, maybe you should try lowering the pressure to 85-90 PSI at least to minimise the flats.
100 PSI on 25 mm tires (in my memory the GP 4000S are much bigger on wide rims) on Firecrests must result in very "hard" tire feeling.
I have trouble thinking you fell it "soft". Bouncy I could understand. Your pump/ gauge is accurate ?

Louis

[TheRich]

Thanks dudes. I'm quite sure that there was no brake rubs during my rides.

I think I'm talking about the rotational stiffness of the rear wheel. Maybe I should ride more miles before making any verdict.

Were the Zipps new?

Aksiums weren't very stiff in my experience.

[bm0p700f]

You can't feel torsional stiffness easily. You feeling sluggishness possibly which could be a number of things

[TheRich]

You can't feel torsional stiffness easily. You feeling sluggishness possibly which could be a number of things

You can feel differences in torsional stiffness, the Mavics were sluggish or less responsive compared to the Bontrager Aeolus 5s that I replaced them with.

When you swap in a set of good carbon wheels, you should be able to tell a difference in stiffness.

[bm0p700f]

Your conflating different things that's the point you can't feel torsional sroffnes by it self. Sluggishness has many causes. Aero wheels feel less sluggish because they are err aero. That's the point nowt to to with torsional stiffness.

A Mavic alloy wheel with the ose thick spoke and funny shapes rim may feel sluggish because it not that aero.

[TheRich]

Your conflating different things that's the point you can't feel torsional sroffnes by it self. Sluggishness has many causes. Aero wheels feel less sluggish because they are err aero. That's the point nowt to to with torsional stiffness.

A Mavic alloy wheel with the ose thick spoke and funny shapes rim may feel sluggish because it not that aero.

No, I'm not...especially considering that it's more apparent at low speeds.

Have you swapped between carbon and alloy wheels on the same frame?

Aksiums don't have the high tension thick alloy spokes either. This may help: https://shop.mavic.com/en-us/aksium-rr0 ... #1028=3283

[bm0p700f]

Well regardless of what you think you can't sperate torsional stiffness from other pararamter unless you built two wheels I indentical but with different gauge spokes an then mount he same tyre. In this case though you are also changing the lateral stiffness so it is impossible to seperate torsional stiffness from other parameters in how a wheel feels.

I know my wheels and the physics that governs how they behave.

That said. Torsional stiffness does have an impact on feel and a 20 spoke rear is somewhat lacking. However other factors maybe contributing to the feeling of sluggishness and you can't seperate those out.

[clarinet5001]

You're using GP5000 with one set and GP4000Sii with the other. They're pretty different tires. If your Aksiums are 17c (rim brake firecrests are 17 as well) then the tires on them will be wider than the 5000s on the Zipps, and this tire setup might feel different in corners and such. In reality, assuming they're both 17c rims under o circumstance should you be running those two different width tires at the same pressures: the 5000s should be a few psi higher than the 4000Sii are considering air volume differences.

You also might be feeling that the spokes aren't up to the task of keeping the stiffer rims in check, so maybe they don't feel entirely like they're 'working together' per se.