Larry is this what you were looking for? - PeachParts Mercedes-Benz Forum

Ashman · #1 05-23-2002, 10:18 PM

Larry are the circled red things the mold marks you were looking for? I have seen this on conti and michelin too if it is.

Alon

Ashman · #2 05-23-2002, 10:19 PM

the other pic

suginami · #3 05-24-2002, 12:08 AM

Ashman, I had the same question. I feel stupid, but I can't figure out what he means by "radial mold marks".

As an admitted novice, don't those bumps look like wear bars to you?

bobbyv · #4 05-24-2002, 12:51 AM

those are tread wear indicators. On a Michelin tire (at least on my Pilot XGT H4s), if you look at the side of the tire's tread directly across that, you will see a small Michelin Man logo. On other tires (like my old Pirelli P600s), you will see a "TWI".

Ashman · #5 05-24-2002, 03:47 AM

Ahhhhhh Larry wanted to see the sidewall.

Ok I'll edit this post with a pic in a sec

Alon

#6 05-24-2002, 06:29 AM

Ashman,

Thanks for the pictures. As said by others in the thread, these are the wear indicators. When the tread wears to the depth of that bar, the tire is supposed to be replaced. However, at that point your tires would probably make very good dry pavement autocross tires.

If you go to:

http://www.tirerack.com/tires/conti/co_ch95.jsp

you will see a picture that I selected becuase it shows the mold mark across the tread. This mark also wraps around onto the sidewall of the tread. This mark was made by the molds which came together from the outside as if you took all the slices of pie, put them on the outer edges of a round table and started pushing them toward the center of the table, putting them back into the same position from which they were sliced.

If you look closely at this picture:

http://www.tirerack.com/tires/goodyear/gy_egt2.jsp

you will see the mold mark running AROUND the circumference of the tire in the center of the tread. This tire was molded in a clamshell shaped mold. This mold is as if you took two pie pans and put one upside down over the top of the other.

I apologize for not describing all this very well. I am very accustomed to drawing diagrams on a white board during technical discussions, it is very frustrating when I try to describe something like this with words alone. I apologize if you feel like I have sent you on a "wild goose chase."

Do you see any marks on the sidewalls of these tires?

Thanks for going to so much trouble in helping satisfy my curiosity.

Have a great day,

Ashman · #7 05-24-2002, 02:45 PM

I'll snap some pics later when I geta chance... My dad borrowed the camera for Granny's 92nd Birthday today.

Last night I tried to get pics, but the flasha nd the darkness made them hard to see.

I do not think mine have a mark across the tread, but there is some little rubble sliver on the sidewall facing towards the tread.

I'll snap some pics and post them later for you.

Its no bother, I enjoy any excuse to take interesting pictures of parts of the car.

Alon

JohnEspeed · #8 05-24-2002, 06:25 PM

Hi Larry,
My dad owns a Tool&Die shop which I used to work at along withmy brother. We made investment casting molds for the aerospace industry. These were complex aluminum molds. We were looking at getting into tire molds, as these are also made from aluminum. We went to Goodyear and saw their molds. The ones I saw were as you described; top and bottom sections.The actual cavities however were made from several machined sections(8 sections for the tread I think, and then 1 or 2 ring sections for the sidewalls,top&bottom).These sections are then screwed down in the top and bottom plates.The tires are literally pulled out the mold. Not sure how, as the tread and undercut created by the radius would lock them in.Perhaps because they are rubber there is enough give?
Anyways, I heard that some other tire companies (specifically Michelin) use, as you described, pie shaped sections, which are pulled outwards radially from the center of the mold. This supposedly also creates a more uniform, accurate tire, however more time consuming.This may partially account for Michelin's higher price.Interesting though. I will start looking at "parting lines" on tires from now on!
John

Subman · #9 05-24-2002, 07:25 PM

Ok I have just taken pics of my tires, Kuhmos, and my dads Pilot Sports.
I have circled what I think you guys are talking about, but I still do not know what it means or why it matters.
Firts my Kuhmos,

Subman · #10 05-24-2002, 07:26 PM

Now the Pilot Sports,

Subman · #11 05-24-2002, 07:28 PM

Is this what you were looking for.
Both the Kuhmos and Michlens have the same types of marks on them. So I would guess that they were made in the same manner.
Subman

#12 05-25-2002, 08:11 PM

Subman,

Thanks for these pictures. Yes, indeed it does appear that the Kumho is molded with a radially sectioned mold.

The reason this matters is that the radially sectioned mold allows the belts to be molded more consistently and accurately into the tire. This results in a tire that is more consistently balanced, but more importantly it has much more consistent road force, which means less stiff spots.

Thanks again,