Guy Burns

I'm checking out 26 x 1.75 - 1.9 tyres for long distance touring. It seems to me, after several weeks reading catalogues, reviews, emailing manufacturers, and so on, that the best is Schwalbe Marathon XR, with a couple of the Continentals possibly in the running, and one or two others, including Vredestein. And they've thrown a spanner in the works - temporary I hope - because they mention skinwall and gumwall, terms I hadn't come across before. According to Vredestein:

Gumwall: Here the tread compound runs all over the tyre and around the sidewall. These are the traditional tyres suitable for normal bikes.

Skinwall: Only the top surface of the tyre carries a tread compound. The sides are a canvass carcass. These tyres are lighter and give a comfortable ride.

Sheldon Browne says something about different tyre makers do BOTH to make the sidewalls more flexible and improve rolling resistance. But goes on to say: "It is not clear to what extent this makes a difference."

So my question is: is there a difference in strength? Is a gumwall (no longer gum I assume from Vredestein's comments, but tread rubber) stronger because the tread compound covers the sidewall? Do all manufacturers still make gumwall and skinwall tyres? Would gumwalls be best for touring?

Any comments appreciated.

alanbikehouston

I live in Houston, which gets brutally intense sun from June to September. I have had sidewalls on "expensive" tires begin to fray and split after just four months of daily sun exposure. Some Continental tires (usually cheaper models) have "all black" sidewalls.

The tires with the black sidewalls are usually a tad heavier than "premium" tires (the ones where the sidewalls are almost transparent if you hold them up to a bright light) and the "blackwalls" might feel a little firmer on the road. But, the black sidewalls last for the life of the tire's tread, so that I can get a year out of a tire, not just four months.

Joeagain

I have gone completely to blackwalls for exactly that reason.

I ride all four seasons and have never had a set of skin/ gumwalls last a full (calendar) year without developing some type of cracking pattern. Actually they get a cracking pattern in a much shorter time than a year, but it doesn't take a full year before I am not comfortable with that tire on the front wheel.


Joe

jeff williams

Kevlar sidewalls hold up longer, I've wiped the tread off IRC Kevlar tires, the walls still hold -no cracks...the treads (what are left) are a different matter.

I'm currently running 2 different Kevlar weave tires, one a gumwall and Kev (rear) and a nicer multi-ply Kev skinwall front.

Softer HQ front (less wear, steering traction is most important) harder cheaper rear (fast rolling, more resilient to wear.)

I will not know for a while how the gumwall rear holds up, the IRC has the Kev weave across the sidewall, the Serfas has it as a strip under the mat I believe.
https://www.serfas.com/tires/VSSK-F19.html

https://www.irctire.com/technology/index.html

Guy Burns

If I understand these responses, Vredestein's description of gumwalls is not correct.

Vredestein's Spider is described as skinwall, I suppose because the thread covers almost the entire sidewall, but there appears to be a thin strip of gum near the rim. It certainly is not a light tyre at 840gms.

Schwalbe describes 'skin' as: "Skin tyres have light, thin sidewalls. Advantages: weight saving and reduced rolling resistance." Their only mention of gum is: "Gumwall: Tread - black; sidewall - gum" I wonder how they describe their Marathon range. There is no gum (so they can't be gumwalls) and the sidewalls are not thin (so they can't be skinwalls).


So, are there really three ways to describe sidewalls?

1. What I will call 'true gumwall', a tan-coloured compound on the sidewalls, maybe just a small strip, with who-knows-what underneath. The gum part is the bit that cracks under sunlight. Is this strip just for looks? Is there an historical reason older tyres were made that way? If you scrap it off, what happens?

2. A 'modern gumwall' which is as Vredestein describes i.e. the black tread compound continues over the entire sidewall, but there is no gum. This type does not crack as easily as No 1.

3. Skin type: light and thin, with little, or nothing, covering the bare carcass.


Would a better description be:

Gumwall: Any tyre that has a tan-coloured, gummy-looking substance on the sidewall which is prone to UV cracking. How it is otherwise constructed is immaterial. It is a layer that does not affect the strength of the tyre.

Skinwall: No tan-coloured, gummy looking substance on the sidewall. The sidewall can be thick, it can be thin, but it cannot have gum.

Is it as simple as that?

capsicum

There seems to be differences in definitions of gum wall, skin wall, etc..
Without using the names, here are the following side walls that I have heard of:
(one extreme)*Plain carcass, AKA bare threads or fabric

(middle, all grades in between)*light, thin, very flexible, natural or synthetic rubber or gum compound, usually tan colored

(other extreme)*tread rubber

The idea behind the lighter walls is less damping(energy absorbtion) when the sidewall flexes.(all sidewalls flex continiously as they roll along under load)
The idea behind the heavier walls and coatings is to protect the carcass from various hazards like abrasion or intense sun.

Also the blackwalls are simpler to make because only one rubber compound is used, it is used all in one step, and because it's heavy duty the carcass does not need to be top notch.

That's the scoop as far as I know.

capsicum

Oh and tire construction.
All tires(even car and tractor tires) start as threads or fabric woven between two wire, or kevlar hoops, in the shape of a tire.(The hoops are known as beads.) This is the carcass, it is the tire's structure, strength, and so on, the exact weave or layering angle (usually single direction threads layered criss cross, not woven) will affect tire rolling characteristics.

This carcass is then impregnated with rubber. Tread rubber in the case of a blackwall(and it's finished, pop it out of the mold) or tan rubber for a thin wall. Then tread rubber is applied over the tan rubber.

The rubber is there only to protect the threads from wear, and in the case of tread rubber provide a certain desired type of traction.
Smooth tires still have tread, they just don't have a pattern formed, or cut into, the tread.

lilHinault

I do know the black stuff in tires is put there for UV resistance, I read about it in a book about Thomas Edison by the US Chemical Society, "Edison the Chemist" or something like that, Edison was working on a source of rubber, and ended up concentrating on the goldenrod plant. He was getting places too, then he died - it was his last project. In telling all about this, the book also goes into what tires are actually made of. They actually put black pigment intentionally into tire compounds to make them stand up to UV over time better.

Joeagain

carbon black

Guy Burns

Thanks for all the info. I've learned more about gumwalls/skinwalls in this thread than in all the manufacturers sites put together.

capsicum

Edison liked to patent other peoples ideas and pretend he was some kind of super inventor. He had a few of his own ideas but for the most part he ripped off other inventors.

Carbon black is used to make the rubber more abrasion resistant, I hadn't even considered it's UV qualities, hmmm learn somethin new every day. Michelin uses a silicon substance, instead of carbon black, in some of their tires.

tzugekumene

considering that most of the wear and tear to the tire happens practically everywhere except to the sidewall, I imagine this wouldn't make a difference until after the end of the useful life of the tire. But I'm only hypothesising.

Gresp15C

I worked for a plastics company, long time ago. Carbon black was remarkably effective at protecting plastic from UV damage. It works by just by being black -- blocking all light from getting into the plastic. There are other additives that can be used in colored plastics, that have more interesting chemistry, but carbon black is cheap and effective.

I also met a chemist who was looking for an alternative to use in tires, hoping for better fuel efficiency.

I got sick of gumwalls rotting away, and switched to blackwalls a long time ago. I don't know if it actually affected the performance or longevity of the tire, but it was unsightly. If you can wear out a gumwall tire before the walls rot, then you ride more miles than I do, and I salute you.

JanMM

Zombie Thread Alert!!

Can't remember how long its been since I last used tires that did not have black sidewalls.
Thinking that maybe I put Panaracer Pasela gumwalls on a bike around 2005 which is when this thread started and then went to sleep until this morning.

chaadster

Yeah, this is some well vintage-assed zombie sh*t, but in fairness to the noob who dug it up, gumwalls are quite trendy right now. I hve two sets in action, Panaracer Gravelkimgs (they call brown sidewall), and Herse Switchback Hill. I think they look sweet in many cases.

Also, I admit I didn’t know anyone made distinction between skinwall and gumwall. I don’t believe there is one, and that those are just two names for the same look and thing, with skinwall being particularly stupid terminology given its etnocentric perspective.

JanMM

The bike that I put Pasela tires on in '05 was an '03 Novara Big Buzz, by the way. Don't recall them having a rubbery/gummy look or feel to the tan sidewalls. I probably referred to them at the time as skinwall.

chaadster

I’m still lovin’ my Buzz, and her out today a bit!




I’ve never seen the terms gum or skin to refer to construction, only to color. I’ve seen differences in the amount (thickness) of rubber on the sidewall, of course, and that includes tires which have black sidewalls, but no on has ever referred to a thinly rubbered black sidewall as a skinwall that I’ve ever heard, and I’d wager it has never happened.