I have old ZIPP 808 wheels and they definitely are not stiff. I'm 85-90kg and when I stand from saddle I can hear that rear wheel rubs brake pads from side to side. I've just received my new wheels, which are Archtek 20mm rims laced to Tune hubs with Sapim Superspoke. Rims are noticably verticaly less stiff than ZIPPs (when I glue tubulars, I always press tires against rims for better contact and grip when glue is stil not cured), so I was quite scared about lateral stiffnes of the wheels. But in fact, theese light 20mm shalow wheels are much more lateraly stiff than my old ZIPP 808 wheels.
So I would like to ask ZIPP owners, if their wheels are also noticably flexier than other wheels or if this is just problem of my old pair of 808's. Is it problem of old ZIPP hubs? ZIPP rims look quite strong to me, but built with their hubs, wheels are quite flexy.
I think you are confused between wheel lateral stiffness and how much does the rim moves between the brake pads.
Although they are more or less related, they are two very different values.
First of all, lateral wheel stiffness represents how much the wheel will deform under a load. This is basically how much you rim will move laterally, near the ground, when you stand on the bike. The stiffer the wheel, the lower the deviation of course. The stiffer the wheel, the better your accelerations (inertia apart).
Second, deviation between the brake pads is more or less the 180° rim deflection measured on a lateral stiffness bench. It is about 1/5th the lateral stiffness.
The wheel stiffness and the 180° deflection are working together through the spoking, the rim stiffness playing the most important role, the type of spoking has a good effect too.
The stiffer the wheel, the more deflection you will find between your brake pads.
This translates into 3 things:
1. your wheel is flexy: the rim deforms a lot near the ground, though this deflection does not translate as a deflection between the brake pads because the rim is flexy and somewhat "absorbs" the load. Also the spoking certainly can't hold the rim enough in place.
2. your wheel stiffness is quite standard, from moderately stiff to stiff: the deflection near the ground is not extremely low nor extremely high, but the rim is stiff enough to make a deformation too between the brake pads.
3. your wheel is extremely stiff: the deflection at the ground is very low, rim and spoking are very rigid too so the deflection between the brake pads is a quite high %age of it. Anyway you can't even perceive the brake pad rim deflection because it is too low.
From what you say, I can tell you the ZIPP 808 is from category 2. The other shallower wheelset is definitely from category 1 unless this is a very special rim.
Since you are a strong rider, you absolutely need wheels from category 3. Avoid wheels from category 1 for one reason: although they will deliver you a good stiffness perception, they won't be performant and won't come with a good durability because the rim moves too much left/right near the ground which will increase spokes fatigue.
Wheels from category 3 are basically stiff full carbon wheels like Mavic CCU, LW Sprints, custom wheels with deep/stiff rims and absolutely strong spokings (32 DT Competition).
Of course you must avoid the super light rims with standard drillings/spokings. Avoid the ENVE 25/45/65 rims because they are very flexy and only available with 20-24 spokings now. The same for Reynolds, though a 46 or 66 built with 28 or even 32 spokes as custom will be OK. Zipp rims, 303/404/808 are fine as long as they have a stronger spoking too: 28/32 or 32/32.
Please see our lateral stiffness bench, the pointer where the load is applied (similar to load near the ground) and the pointer at the 180°, translating the deflection between the brake pads.
What's interesting about wheel stiffness and perception of the stiffness is that we can tune both values depending on the spoking, the rim stiffness and the hub geometry.
Have a great week-end.
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Nice post that goes well in this thread too...