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what is the function of the gumwall on a tire?

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

what is the function of the gumwall on a tire?

Old 03-09-01, 07:32 PM
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mike
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I like to use old tires because it is recycling at it's best. It gives me great pleasure to rescue a 20+ year old tire from it's trip to the landfill and ride it thin.

The other day, an 83 year's young gentleman friend of mine gave me an old 27" X 1 1/4" gumwall tire from a '70's vintage 10-speed.

The problem was that the gumwall had deteriorated. It turned into a collection of what resembled black scabs - very unsightly - not sexy as road biking should be.

Happily, after two days of riding them, the scabs have fallen off leaving a clean pale-tan colored wall. The cords are visible through a thin skin of white-ish rubber. The black tread is still in fine shape and is holding nicely.

This leads to the question: What is the purpose of the gumwall? Is it simply cosmetic?

Does it add any strength or other function to the tire?

Why did tire manufacturers use gumwalls for tires?

Mike
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Old 03-30-01, 11:36 PM
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Geez,

The replies to this post got wiped away by the server crash. Alas. They were so clever and informative.

Allow me to fill the gap. One writer said that the gum-wall provided a softer ride for the thin hard 1 1/4" tire than a solid black-wall would. That made good sense.

The question I had was, "How will the tire function without the gum wall? What if the gumwall rots and falls off like it did on my vintage 1970's?"

Yesterday I found out. The tires rode pretty well on the road when all was well. The streets were clean, and I rode mostly vertical. However, I chanced into a rose garden by accident along my commute home yesterday (for the whole story, see my post in the maintanance section in the thread about Slime in tires).

The thorns of the common rosebush attacked my naked tires like savage dogs; clawing and biting and piercing. Oh, it was terrible.

AND, I got a flat tire.

So, the gumwall helps PROTECT the tire and the inner tube. It is not just for looks after all.
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Old 08-17-03, 12:08 PM
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This is an oldie, but per above, it looks as if the replies got nuked. Could any of you please elaborate on the advantages or disadvantages of a gumwall tire?

Thanks!

pHusion
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Old 08-18-03, 07:57 AM
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greywolf
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I was wondering the same question myself my newly renovated wet weather bike has 27" wheels with narrow alloy rims , the old back tyre was shot but the front was just as you described Mike, the only new 27" tyres avalable here are 1&1/4" width & they look & feel odd on the narrow rims ! I didnt throw the front one away but hung it up in the shed for a spare , the 27" tyres are cheap to buy but of poor quality but I don't think it matters too much as the pressure is a lot less ! I dont use the bike much anyway but because of the wider tyres I've ridden a few of the lesser trails around here which I would'nt take my road bike with its 700x23c, s on !!
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Old 08-18-03, 10:44 AM
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The "gumwall" is merely latex over the cloth casing. In olden times, you would periodically brush liquid latex over your sidewalls, in order to keep your good tires (tubulars) watertight. the latex weighed less than rubber, cost less, allowed better sidewall flex, and just looked better.
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Old 08-18-03, 10:46 AM
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Dave,

The latex also ensured that your base tape wouldn't
seperate from the carcass of the tire, which we oldtimers
know is not a good thing. . .

Marty
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Old 08-18-03, 04:56 PM
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Good 27" tires are getting hard to find, so I read the latex hand-painting info with great interest.

It would be good to use up some of the skins on old tires of which the gumwall rotted off.

Does anybody remember riding on Schwinn Puff tires? Don't laugh. Those were some good performers - not racers, but they provided a silky ride and hugged the road well. I would like to keep a couple of those alive with some latex.

What kind of latex do you use? Where do you get it?
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Old 08-18-03, 05:05 PM
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Originally posted by Dave Stohler
The "gumwall" is merely latex over the cloth casing. In olden times, you would periodically brush liquid latex over your sidewalls, in order to keep your good tires (tubulars) watertight. the latex weighed less than rubber, cost less, allowed better sidewall flex, and just looked better.
Where I grew up, there was a factory that made balloons with latex. I would go there with a jar, and they'd fill it with pure liguid latex for me for free. I would use that to restore the sidewalls on my tubular tires.
 
Old 08-18-03, 06:21 PM
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what is replacing the latex gumwall on modern tires?
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Old 08-19-03, 02:29 PM
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What kind of latex do you use? Where do you get it?
http://www.worldclasscycles.com/jevelot_tire_life.htm

what is replacing the latex gumwall on modern tires?
Just plain rubber.
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