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Thread: Choosing a Tire Durometer

  1. #1
    Join Date
    Jul 2003
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    Louisville Slugger
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    100

    Choosing a Tire Durometer

    One of the tools needed to bring my program up to the next level is a tire durometer. So I Googled "durometer" and quickly was a victim of TMI. Read a great article on Wikipedia which created WTMI (way too much information).
    http://en.wikipedia.org/wiki/Shore_durometer

    So here's the basic question: what is the preferred gauge rating for reading slot car tire hardness? A? C? OO? other? All gauges read from 0 - 100 with the actual number being meaningless. The letter rating of the gauge itself gives the range of depressive force it reads in.

    Anyone who has a durometer or experience with one, please have a look at the scale and let me know: 1. The letter rating of the gauge and 2. The range of numbers it reads in (25 - 40, for example).

    Thanks Guys!
    Tom Z.
    The Older I Get, the Faster I Was...

  2. #2
    Join Date
    Oct 2005
    Location
    TEXAS
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    329
    Most people that use a Durometer use one that 1:1 Race Cars use which reads 0-100. Wrightway Products sells one which is available thru Distributors so your Track can order it.
    Jet Products is the only tire manufacturer that currently puts a Durometer # Reading on his Tire Bottles. Koford, Alpha and Thunder all use some variations determined by hardness Medium(M), Hard(WH) or 1X, Extra Hard(WX) or 2X, Extra Extra Hard(WXX) or 3X.

    Durometer readings are a point of reference for your tires, example a Jet 36 hard will read 50 on some Durometers, if a Jet, Alpha, Thunder or Koford works good then you try and find tires that read the same on your durometer as that particular tire does. I write the reading inside the hub with a Sharpie so when I find something works I know how to match, tires tend to soften if you run glue so take your reading before running them.
    One of the problems is making sure both tires are the same hardness. Occasionally in some bottles you will find a 34 and 38 or 14 and 20, so I normally durometer several pairs at a time and match by hardness, that way I don't get a surprise.
    I made tires for 15 years and the donuts came in a 24" square and there could 4 point variance from one side of the sheet to the other.
    This variance will be present in Wonder, Natural, SBR or even Speed Rubber.

  3. #3
    Join Date
    Feb 2003
    Location
    barrington, il.
    Posts
    972
    Tiger Tom Pistone sells a nice unit for around $55 that a lot of racers use.He has them on ebay often. Google him for website. John
    Racing now at Wanker Valley Raceway and awaiting puppies!!

  4. #4
    Join Date
    Jun 2002
    Posts
    625
    Tire durometers are like any other "meter" you own. They are relative to you. How you use it, how you read it etc. As long as it gives you some kind of reading, any manufacturers meter will work for you. Just like arm meters, dynos and the likes, the numbers are always relative to you personally. You make your own logs and comparison figures..................
    Why make it tougher than it really is?
    e-mail: scrgeo@comcast.net

  5. #5
    Join Date
    Jul 2003
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    Louisville Slugger
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    100
    OK, I understand and agree with all the above. My issue is that there are 12 scales in use. There are 12 different configurations of durometer available. All read 0-100. The numbers mean nothing and are relative. Ignore the numbers on the dial.

    Each durometer is to be used within a given range of force and that use is assigned a letter. From Wikipeadia:

    Durometer Scale Configuration Diameter Extension Spring force
    A 35 truncated (frustrum) cone 1.40 mm (0.055 in) 2.54 mm (0.100 in) 822 gf (8.06 N)
    C 35 truncated (frustrum) cone 1.40 mm (0.055 in) 2.54 mm (0.100 in) 4,536 gf (44.48 N)
    D 30 cone 1.40 mm (0.055 in) 2.54 mm (0.100 in) 4,536 gf (44.48 N)
    B 30 cone 1.40 mm (0.055 in) 2.54 mm (0.100 in) 822 gf (8.06 N)
    M 30 cone 0.79 mm (0.031 in) 1.25 mm (0.049 in) 78 gf (0.76 N)
    E 2.5 mm (0.098 in) spherical radius 4.50 mm (0.177 in) 2.54 mm (0.100 in) 822 gf (8.06 N)
    O 1.20 mm (0.047 in) spherical radius 2.40 mm (0.094 in) 2.54 mm (0.100 in) 822 gf (8.06 N)
    OO 1.20 mm (0.047 in) spherical radius 2.40 mm (0.094 in) 2.54 mm (0.100 in) 113 gf (1.11 N)
    DO 1.20 mm (0.047 in) spherical radius 2.40 mm (0.094 in) 2.54 mm (0.100 in) 4,536 gf (44.48 N)
    OOO 0.635 mm (0.0250 in) spherical radius 10.7 mm (0.42 in) - 11.6 mm (0.46 in) 2.54 mm (0.100 in) 113 gf (1.11 N)
    OOO-S 10.7 mm (0.42 in) radius disk 12.0 mm (0.47 in) 5.0 mm (0.20 in) 197 gf (1.93 N)

    The different uses durometers are put to require as low a force as 78 gf (gram foot?) up to 4,536 gf. Which use do slot car tires fall into? Which scale (A - OOO-s) or spring force rating is appropriate?

    Tom Z.
    The Older I Get, the Faster I Was...

  6. #6
    Join Date
    Jun 2002
    Location
    Charles Town, WV
    Posts
    1,225
    Working on your PHD dissertation I see... You are making this way too hard.

    Have you ever seen and touched a tire durometer at the track? I have a Longacre duromater ($50-60 vice $300-400+) I bought at a local car shop. I touch the needle to the middle of the tire and apply enough force to depress the needle until it retracts into the flat part of the housing. How much force is that; I don't care. I then spin the tire 180 degrees and "try" to replicate the amount of force that I did to get the first result... Whatever numbers are indicated on the dial I "try" to average to get an overall rating for the tire. I do that for a number of tires of the same type and "try" to match as close as possible. Will I ever win a Nats Championship; No. Does this really work; maybe yes or no. Does it give me a psychological advantage; maybe. Would I be better off to race right out of the tube; most likely...

    Do what works best for you and your program...

  7. #7
    Join Date
    Jun 2002
    Posts
    1,909
    Bill, your new name is "Tube Racer."
    I like long walks, especially when they're taken by people who annoy me.

  8. #8
    Join Date
    Jun 2002
    Location
    Charles Town, WV
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    1,225
    Thanks, Bill! I will wear that name proudly.

    I, like many others, have been known to "tube" a number of races over the years.

  9. #9
    Join Date
    Jun 2002
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    Wellington, New Zealand
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    4,474
    I too have one of these toys

    I use mine the same was as Bill describes. Guess I was using it correctly all the time
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  10. #10
    Join Date
    Jun 2002
    Location
    NorthWesterner now in Philippines
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    9,461
    Quote Originally Posted by Zippity View Post
    I too have one of these toys

    I use mine the same was as Bill describes. Guess I was using it correctly all the time
    How do you know??? Maybe you were BOTH using it INcorrectly!

    As with many measuring devices, the actual reading does not matter as much as the ability to consistently measure multiple objects and compare the difference between them accurately.

    There are many gadgets and gauges that can provide many clues... especially when at the work bench...
    But the one that tells the most is the LAP TIMER on the track, and ultimately the LAP COUNTER in a race.
    - - - - - - - - - - - - - - - - - - -
    Paul Kassens
    OWH Slot Car Talk "Mom"
    The Old Weird Herald
    email: paulk@oldweirdherald.com

    - - - - - - - - - - - - - - - - - - -

  11. #11
    Join Date
    Jun 2002
    Location
    Wellington, New Zealand
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    You cheeky sod

    I meant I make 3 tests per wheel and write the average on the tyre tube lid.

  12. #12
    Join Date
    Jun 2002
    Location
    NorthWesterner now in Philippines
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    9,461
    And I meant that just because more then one person uses the same method, that you can not necessarily assume that it means you are BOTH using the CORRECT method. It simply means you are BOTH using the SAME method.

    If scientific research was based on being validated by simply getting two people to agree on a method... well... nevermind.

    Yes... I do realize you meant that your method was validated because it was the same method used and described by a fellow slot racer whom you respect and trust - right?

    You were correct in also assuming I was simply being a "cheeky sod"

    PK
    - - - - - - - - - - - - - - - - - - -
    Paul Kassens
    OWH Slot Car Talk "Mom"
    The Old Weird Herald
    email: paulk@oldweirdherald.com

    - - - - - - - - - - - - - - - - - - -

  13. #13
    Join Date
    Dec 2008
    Posts
    161
    There really are not any commercial off the shelf durometer that work well for .760 dia. 600 hub tires (the most common wing car size). This is because the rubber is so thin. For smaller hubs like .500 or less or for 13/16 tires on a .600 hub you can use a Shore A durometer. This will at least let you tell the difference between a "fish" tire and a "Wonder" rubber tire. That is about it. For slot car use there are many problems with a Shore A durometer. For example it is not intended for foam rubber, if the point of the needle aligns with a bubble in the rubber you will see a low reading, it is intended for flat surfaces only, and the rubber needs to be at least .250 thick. If you meet all of these requirements and buy a durometer costing about $600 you can expect to get a reading accurate to about +-5 points if. One problem is the the reading varies depending on how hard you push, how fast you push, and how square the needle is to the tire. Shore OO is a little better because the needle is larger and the spring softer. We have built our own hardness measuring instrument for use in testing the tires we sell that has a much larger measuring area that is flatter, a much softer force, a smaller travel (to more closely duplicate the actual deflection of the tire and also to allow the accurate measuring of .600 hub tires), the tire sits in a nest and the probe comes down on it so the measurement is affected by the operator and is repeatable. Short of doing something like that I would suggest saving your money and take Paul advise and go out before the start of the race and take the tires you intend to use and try each pair out on the track with the car you are racing in that event. Test the tires you intend to run in the middle lanes on Orange or Blue, test the tires you intend to use on Red and White on Red lane. The same hardness tires will run completely different depending on how much rubber and glue is on the track, the room temperature, and the body you have on the car. The tires that work in practice the day before might not work at all if the track is cleaned before your event. Tires that hook up fine with a high downforce body may not get around at all with a low downforce body.

  14. #14
    Join Date
    Aug 2010
    Location
    Arizona
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    621
    Stuart,
    Would something like this work as far as using it hand held?

    http://www.ebay.com/itm/NEW-HT-6510O...item4605161609

  15. #15
    Join Date
    Mar 2006
    Location
    Sydney, Australia
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    189
    Seems like automotive and slot car tyres are suited to type A, I expect slot car tyres to be much like rubber bands as a measuring standard.

    Stuart is also right, large hub tyres make measuring a waste of time, so I would be spending the min amount on a unit. Accuracy is not going to paramount you will be looking at a differential between rubbers rather than an absolute reading. My usage will be checking new tyres what they are marked hard, soft medium where the fit in that bracket.

    Ie what is the difference between something that is marked hard but softer than normal and something that is marked medium but harder than normal.

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