I replaced the headset on a Pinarello.
I'd been holding onto this bike for another job, but when turning the handlebar
there was a "grinding sensation that locks up in the middle"—the bearings needed replacing.
The middle lock-up phenomenon is rideable if it's minor,
but there's pitting (uneven wear) on the front and back of the bearing ball races,
so it really should be replaced.
Plus, no-handed riding becomes impossible.
The bearing stiffness overpowers the natural centering force of the front wheel during riding.
These are different-sized top and bottom bearings, but this time the top one was shot.
When I sprayed parts cleaner, rust liquid came out endlessly.
Most integrated headset cartridge bearings
have some angle at the contact point with the inside of the head tube.
It's either 45° (left in the image above) or 36° (right).
Because of this angle, you're essentially pressing in a cone,
which centers everything and eliminates play,
but on the Pinarello headset, the press-in section is 90°.
With 90°, you theoretically can't eliminate lateral play,
so the headset bearings are press-fit.
This is why Pinarello forks won't come out by hand.
Think of it like a BB30 crank going in vertically.
In the diagram above, the inner and outer diameters are shown as equal,
but if the frame's inner diameter is even 0.1mm larger,
the bearing would slide in by hand and lateral play wouldn't be eliminated, so
I suspect the frame's diameter is slightly undersized.
While I was at it, I swapped the top cap for a thinner one.
If your shop carries Pinarello, they can order this from their distributor.
(Though I'm not sure if distributors have it in stock)
Among Pinarello owners riding with the top cap in the "Mount Fuji" position
and their stem all the way down,
I think there are probably quite a few who secretly wish they could go lower,
but many just keep riding as-is without knowing about this option.
Since Pinarello headsets are press-fit, most people probably
can't easily swap this part themselves.
To match this customer's other bike's position,
we needed to lower the stem, and since we were doing the headset swap anyway,
I suggested doing it at the same time.
So, if you're curious about this part,
please consult with your local Pinarello dealer.
I'd been holding onto this bike for another job, but when turning the handlebar
there was a "grinding sensation that locks up in the middle"—the bearings needed replacing.
The middle lock-up phenomenon is rideable if it's minor,
but there's pitting (uneven wear) on the front and back of the bearing ball races,
so it really should be replaced.
Plus, no-handed riding becomes impossible.
The bearing stiffness overpowers the natural centering force of the front wheel during riding.
These are different-sized top and bottom bearings, but this time the top one was shot.
When I sprayed parts cleaner, rust liquid came out endlessly.
Most integrated headset cartridge bearings
have some angle at the contact point with the inside of the head tube.
It's either 45° (left in the image above) or 36° (right).
Because of this angle, you're essentially pressing in a cone,
which centers everything and eliminates play,
but on the Pinarello headset, the press-in section is 90°.
With 90°, you theoretically can't eliminate lateral play,
so the headset bearings are press-fit.
This is why Pinarello forks won't come out by hand.
Think of it like a BB30 crank going in vertically.
In the diagram above, the inner and outer diameters are shown as equal,
but if the frame's inner diameter is even 0.1mm larger,
the bearing would slide in by hand and lateral play wouldn't be eliminated, so
I suspect the frame's diameter is slightly undersized.
While I was at it, I swapped the top cap for a thinner one.
If your shop carries Pinarello, they can order this from their distributor.
(Though I'm not sure if distributors have it in stock)
Among Pinarello owners riding with the top cap in the "Mount Fuji" position
and their stem all the way down,
I think there are probably quite a few who secretly wish they could go lower,
but many just keep riding as-is without knowing about this option.
Since Pinarello headsets are press-fit, most people probably
can't easily swap this part themselves.
To match this customer's other bike's position,
we needed to lower the stem, and since we were doing the headset swap anyway,
I suggested doing it at the same time.
So, if you're curious about this part,
please consult with your local Pinarello dealer.