1995-1996 ROCKSHOX JUDY SL (Yellow) = Tire Clearance 26"

[Cloverleaf]

The other issue with modern tyres vs old ones is the volume. Casings now are generally the widest part of the tyre whereas on older tyres the widest point was usually the tread which stuck out quite a bit beyond the casing. Therefore a modern tyre is for example 2" wide and 2" tall, whereas an old tyre would be 1.6" wide at the casing, 2" wide at the outside of the tread but, crucially for clearance on old forks, only 1.6" tall. A 2" tyre these days is the equivalent of an old 2.2" tyre in height, or maybe even worse. It's one of the reasons modern gravel bikes are so much more stable than old 90's MTB's even though they're outwardly similar. Bigger volume tyres equal lower pressures and more grip. Old stuff is usually as much if not more constrained by height as much as width when it comes to clearance.

 

[wudangsatellite]

You gotta ride like its '95

If you set up 2.1/2.2 tubeless
(or even aerothan thermoplastic tubes)
you could drop the tyre pressure to 25psi and get the grip like 2.4 s

Thanks for the tip bikeworkshop.

 

[wudangsatellite]

The stock arch definitely has more tire clearance.

Stock arch with 2.25 Nobby Nic (set up with a tube):
20250207_175913 by Rented Mule, on Flickr

Stock arch with 2.4 Nobby Nic (tubeless):
20250207_180125 by Rented Mule, on Flickr

FSX arch (and AC crown) with the same 2.4 Nobby Nic:
20250207_180408 by Rented Mule, on Flickr

I think clearance is going to vary by tire manufacturer. There's enough clearance with stock arch that I would be very comfortable running the 2.4 Nobby Nic. It's basically touching the FSX arch though. I'm fairly confident this is an original FSX arch that's had the cantilever stop machined off - that's what the seller claimed and you can see the machining marks in person.

I think you are right.
I am very surprise the Nobby Nic at 2.4 has sufficient clearance from the OEM Arch and the FSX Arch.
Whereas my Continental Kryptotal has 0 clearance from the OEM Arch.
And I also had the Maxxis DHF 2.3 at the front which has only 4-5mm clearance. I did get some wheel bite and 1 spot while riding.
I am not running tubeless...I am using Maxxis Welter Weight Inner Tube 26" 1.5-2.5 (Schrader valve).

Right now thought is this.
Right now what I am thinking is...I'll keep the Maxxis DHR II 2.3 for the back wheel.
And I repurchase a Maxxis Ardent Race 2.2 for the front wheel.
I will try to sell away the Maxxis DHF 2.2

Please feel free to share any advice.
I still find it unbelievable the Noby Nic 2.4 can have clearance from the Judy SL arch.

 

[wudangsatellite]

The other issue with modern tyres vs old ones is the volume. Casings now are generally the widest part of the tyre whereas on older tyres the widest point was usually the tread which stuck out quite a bit beyond the casing. Therefore a modern tyre is for example 2" wide and 2" tall, whereas an old tyre would be 1.6" wide at the casing, 2" wide at the outside of the tread but, crucially for clearance on old forks, only 1.6" tall. A 2" tyre these days is the equivalent of an old 2.2" tyre in height, or maybe even worse. It's one of the reasons modern gravel bikes are so much more stable than old 90's MTB's even though they're outwardly similar. Bigger volume tyres equal lower pressures and more grip. Old stuff is usually as much if not more constrained by height as much as width when it comes to clearance.

Thanks for the valuable input Cloverleaf. Very good.

 

[rentedmule]

I was also surprised the 2.4 fit so well. I pulled it off a Marzocchi Z1 with a bolt-on arch where the fit looked pretty snug.

I forgot to add that both of those tires were on fairly wide rims - the 2.4 is mounted on a Crossmax Enduro and the 2.25 is on a Ringle Black Flag. A wider rim may pull the center of the tread down a bit further.