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Rubber and Rubber Kits
1 Pinball Rubber Types
There are two main colors of pinball ring rubber, black and white. Flipper rubber has always been available in black and white as well, along with red, yellow and more recently other colors such as purple and blue.
Natural gum rubber that has not been colored or has no additives will have a brown (or beige) appearance. To get black, carbon is added to the gum rubber making it harder. I assume (although I do knot know for certain) that modern white rubber is bleached to get it's extreme whiteness. As mentioned before additives (such as catalysts and polymers) are used to change its elasticity and also talcs or other powders to make it release well from the ring molds. Other additives to enhance the white appearance are equally possible. Older original white pinball rubber will have a more 'off white' appearance. Be aware that white rings react to UV light, so should be kept in a drawer and ziploc bags or airtight tubs.
Rubber hardness is measured by a durometer scale considered to be from 0 (infinitely soft) to 100 (bone hard). They push a blunt probe at the rubber and see how much it resists. For example a rubber band would typically rate 25 on the 'Shore A' durometer scale. Chewing gum rubber would be even softer, while a car's tire tread would rate 70 or more on the same scale to make it more durable. Currently in F1 the cars can choose between hard wearing 'prime' or soft and grippy 'option' tires. You have the same choice for your pinball games.
1.1 Ring Rubber
Black pinball ring rubber rates around 50-60 'A' and so has less "bounciness" than white which rates around 40-45 'A' on the durometer scale. So the black rubber is harder and will last longer given the same conditions.
Although this is a personal choice, for pinball restorations intended for home use the preference is to use white rubber rings and a softer flipper rubber (so not black). Some games just look better in all black rubber, so the debate rages between looks and playability.
Operators preferred to fit black rubber because of their durability (they didn't need to change the rubber so often) and so most games came supplied new with black rubber rings. This continues today with Stern, the main supplier of coin operated pinball games.
1.2 Flipper Rubber
Red flipper rubber is considered to be about 45 durometer and is often preferred over black flipper rubber for this reason. So for Flipper Rubber the scale is White, Yellow, Red and then Black in order from Soft to Hard. White and yellow are considered very close for Flipper rubber performance. The same is true of the 'post sleeves' where yellow is the soft and black is the hard option. Games designers take this into account when placing them on the playfield. There are also colored 'Cliffy' post sleeves available that can make the game look nice and are easy to clean. You need to make your own choice as to how this effects your game, as with most things to do with rubber choice it's a compromise between maintenance, appearance and gameplay.
Don't forget to keep the post sleeves clean and 'spin' (rotate them to a different face) over time when cleaning the playfield. Same goes for flipper rubber, otherwise they wear at the tips and then will break there. I prefer Red (or yellow) flipper rubber on most of my games, and will clean them and then rotate the 'tip' behind the back of the flipper by 1/4". Over time you will see a line of indentations behind the flippers on my games. If this bothers you or reaches near the bottom of the flipper, change the flipper rubber for new ones.
1.3 Ring Kits
If you want to replace rubber rings on a game, many suppliers will sell 'ring kits' specific to your game with a fitting chart. If in doubt it's probably worth buying one of the kits to get the information.
Once you have more than one game, or can verify the rings on your game with a manual that lists the parts, it becomes more cost effective to buy an assorted 'tub' of rubber rings or make up your own assortments. From these you can make up your own 'kits' and only order special rings, flipper rubber and plunger tips that you need.
Another tip with rare plastics is to fit rubber 'post caps'. The theory is that a ball hit can pop the rubber cap off the post thread allowing the plastic to flex rather than break. With metal nuts (or with nylon hex caps) the plastics stay firmly in place and may be more easily broken. When the first cap 'pops' - you may have saved the cost of replacing the plastics and those post caps have paid for themselves. This works well for the Bally and Williams SS games.
If they are documented, we show a game's specific rubber kit will be found under the game's listing, and is considered part of the 'shop-out guide' for that game. Experienced owners are encouraged to document ring kits for their games and to provide fitting diagrams or explanations.
1.4 Rubber Ring Sizing Chart
For finding the size ring for a missing or deteriorated original, try the ring sizing chart at Rubber Ring Size Chart
Now that you know the rules, here are some exceptions.
Blue rubber rings have become available in many sizes recently and appear to be similar to white in hardness. It may just be white rubber colored with a blue 'acid dye', which is commonly used as a dye for nylon and man-made fibers. Although this may have some effect, it doesn't make them as hard as black rubber.
White rubber rings made from different suppliers can be different durometer! Happ white rubber seems to be softer than most of the modern rubber suppliers (STC and others). As you try different types you will get a feel for this.
Another point is that there are (yellowish tinged) white rings called 'dead rubber' - usually found in the 5/16" or 7/16" single post ring sizes. They were used in EM and some Bingo games.
2 Rubber Ring Maps by Game
3 Links to Other Web Sites with Ring Maps
Ring maps for various games can be found at the following sites: