My tires have developed an annoying 'squishing' noise when riding. At first, I thought there was tar or some other sticky substance on part of the tire tread (I was riding on pavement). That's not the case. The tires are clean and the same noise occurs on the trail, regardless of surface. If I inflate the tires to 15-20 PSI, the noise disappears completely. Below about 15 PSI, it comes back. I'm guessing there is some movement between the tire and tubes causing the noise??? Is this noise common at low pressure?

Possibly sidewall noise.

wrinkle in the sidewalls?

Guessing the tires against the inner tubes. Maybe some chalk powder or talc might fix it

Solved...

What tires?
Why so low a tire pressure?
Likely, as previously stated, sidewall sound due to low pressure and movement.
Solution...already stated...

In the Fatbikes forum, the relevant question is, why so high a tire pressure? I have a pair of fatbike tires that need to be run at 20 PSI. They're up for adoption, if anyone is interested.

What fatties need to be 20PSI?

(one drop and you bounce like a beach ball!)

I had one ride following a trail, but the last part was washed away. What should have been a 5km trail turned into a 25km road. It was a long day, quite tired, so I pumped up to 25 psi for an easier, bouncier ride home

I have a pair of Origin8 Supercell tires left over from when I was riding a 26" fatbike. They exhibited awful self-steering unless inflated to the full 20 PSI. They're heavy, too, but they are the quietest fatbike tires I've had for pavement.

Low pressure (5-10psi) was initially for riding in sand. On the trail, I started at 20psi, but it was too bouncy in many sections and I lowered it to about 15psi. 20psi seems great for pavement but I don't really ride it on pavement.

What I've noticed is actual diagonal 'stress' lines on the sidewalls that were not there when I bought the bike. Bike was used but had been stored unused in an air-conditioned storage unit for 4 years. So I'm wondering if the tires (or at least the sidewalls) have become slightly brittle from age?

These diagonal lines were not there when I bought it. They are around most of both tires. Since I'm converting it to tubeless, I suppose I'll find out if this is an issue caused by the tubes soon enough.

ok that makes sense,
a MUP connects several trails in my area, so when on the paved I get to deal with the
wirrRRRRRrrrrrRRRRRrrrrrRRRRRRrrrrrr in time with my cadence.
On the bright side, walkers and runners know I'm coming... 500 feet away (slightly embarahassing)
(I sound like an off road 4x4 pickup)

Yup those stress lines will happen with the lower pressures
(same lines that the dragsters get)
I've noticed that gumwall tires have the colorful layer that goes bad sooner for some reason (or it's more noticable)

I know that the cheapie knobbies (like the set I have) are heavier/more rolling resistance/more self steering.
But my cheap a- um... butt, gets buyers remorse if I get new tires before the old ones ware out.

I'm due for a set of jumbo jims.... so... one of these days.

Edit: apparently there is a sale and my cheap self just bought a set.... so update in a week or so.

Wow, the stress lines got significantly worse after my trail ride this morning They may have nothing to do with the 'squishing' sound - I really think that is a tube-tire friction problem. But I'm fairly certain the lines are cosmetic in nature and related to their age (6 years). I was running about 12PSI on the trail today and that seemed optimal. Started out at around 18 and the bike was nearly unrideable.

Did I say 'cosmetic'? After a post-ride inspection, these tires are pretty much shot. The 'gum' is brittle and flaking away exposing the reinforcing threads. Looks like new tire time soon!

There have been some negative stories about gum wall tires. I only lightly skimmed over the stories, but it's a real thing

Well....
https://www.schwalbetires.com/Jumbo-...BOXED-10601023

Found this on MTBR forum:

​​​​​​there is a reason carbon black is added to rubber for tires, it has the highest
molecular surface area for reinforcement of the polymer chains.
it improves its tensile strength and wear resistance

skinwalls are weaker, since there is far less reinforcement and wear resistance going on in the non-black rubber

in fact any other color than black is weaker or the tire behaves worse in some way.

run them if you want, expect them to degrade sooner

Practically all rubber products where tensile and abrasion wear properties are crucial use carbon black, so they are black in color. Where physical properties are important but colors other than black are desired, such as white tennis shoes, precipitated or fumed silica has been used as a substitute for carbon black in reinforcing ability.

Traditionally silica fillers had worse abrasion wear properties, but the technology has gradually improved to a point where they can match carbon black abrasion performance.

advanced fillers are not in your gumwalls, your gumwalls are closer to raw vulcanized rubber.


I won't be buying gumwalls again for sure. Merlin in the UK has a clearance sale on Jumbo Jims - looks like just over $100 for a pair including shipping to USA

You also said the tires are six years old.

How were they stored? The way they were kept could have massive implications on that degradation.

I've had road tires (that weren't even gumwall) harden significantly after six years, and perform poorly enough that it was better to swap them out.

Problem solved, sort of. After researching the subject on this forum and elsewhere the 'gum' is simply a weatherproofing that protects the threads. So it's not really structural. Applying a latex coating is all that's needed. This is one recommended product and what I used. Just brushed it on. 2 coats in those areas that were really bare. We'll see how they hold up. I've also got some Jumbo Jims incoming and will wait to go tubeless when I eventually mount those.

I'm so sorry I'm enabling you....
(don't listen to meeee!)

I run 4.8" Jumbo Jims year-round tubeless. Absolutely no regrets.