Class: Fitment::Combo

Inherits:
Object
  • Object
show all
Defined in:
lib/fitment/combo.rb

Defined Under Namespace

Classes: DiameterMismatch, Max45Error, MaxError, MinError, ValidationError, WidthMismatch

Constant Summary collapse

BY_RIM_WIDTH =

we’ll go from 6“ to 10” rim width, with emphasis on 7“ to 9” a set of 3 tire widths for each rim width: min, max45, max max45 is the maximum width listed at 45% aspect ratio (no higher) data below is from www.tyresizecalculator.com path: /charts/tire-width-for-a-wheel-rim-size-chart

[[6.0, 175, 185, 225],
[6.5, 195, 195, 235],
[7.0, 195, 215, 255],
[7.5, 205, 225, 265],
[8.0, 225, 245, 275],
[8.5, 235, 255, 295],
[9.0, 255, 275, 305],
[9.5, 255, 285, 315],
[10.0, 275, 295, 295]]
BELOW_6 = 
[[3.5, 125, nil, 135],
[4.0, 135, nil, 145],
[4.5, 145, nil, 165],
[5.0, 155, nil, 185],
[5.5, 165, 165, 205]]
ABOVE_10 = 
[[10.5, 285, 315, 315],
[11.0, 305, 315, 345],
[11.5, 315, 335, 345],
[12.0, 325, 345, 345],
[12.5, 345, 345, 345],
[13.0, 355, 355, 355]]
MODELS =

Now, let’s model the above table with equations For every x (rim width inches), we have 3 ys (tire width millimeters) min, max45, max

{
  # Linear: y = a + bx (or: mx + b)
  simple: [20, 40, 75],            # assume 25.4 slope
  basic: [20.689, 38.467, 74.022], # assume 25.4 slope
  linear: [[13.222, 26.333],       # r2 = 0.9917
           [12.333, 28.667],       # r2 = 0.9941
           [71.889, 25.667]],      # r2 = 0.9926
}
TIRE_EXCESS =

extra rubber material near the bead relevant to fitment

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Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(tire:, wheel:, model: :actual) ⇒ Combo

Returns a new instance of Combo.



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# File 'lib/fitment/combo.rb', line 125

def initialize(tire:, wheel:, model: :actual)
  @tire = tire
  @wheel = wheel
  @model = model
end

Instance Attribute Details

#model ⇒ Object

Returns the value of attribute model.



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# File 'lib/fitment/combo.rb', line 123

def model
  @model
end

#tire ⇒ Object

Returns the value of attribute tire.



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# File 'lib/fitment/combo.rb', line 123

def tire
  @tire
end

#wheel ⇒ Object

Returns the value of attribute wheel.



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# File 'lib/fitment/combo.rb', line 123

def wheel
  @wheel
end

Class Method Details

.new_with_params(tread_with, ratio, diameter, width, et: nil, offset: nil) ⇒ Object 



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# File 'lib/fitment/combo.rb', line 114

def self.new_with_params(tread_with, ratio, diameter, width,
                         et: nil, offset: nil)
  tire = Tire.new(tread_with, ratio, diameter)
  wheel = Wheel.new(diameter, width, et: et, offset: offset)
  Combo.new(wheel: wheel, tire: tire)
end

.snap(flt) ⇒ Object

rounds to e.g. 235, 245, 255, etc. (per industry convention)



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# File 'lib/fitment/combo.rb', line 73

def self.snap(flt)
  ((flt - 5) / 10.0).round * 10 + 5
end

.tire_widths(rim_width_in, model = :actual) ⇒ Object

linear model, given a rim width in inches, determine:

  • minimum tire width in mm

  • maximum tire width limited to 45% aspect ratio

  • maximum tire width above 45% aspect ratio (big truck tires)

  • models: :actual, :simple, :basic, :linear, :best, :extended



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# File 'lib/fitment/combo.rb', line 82

def self.tire_widths(rim_width_in, model = :actual)
  if model == :actual
    (BY_RIM_WIDTH + BELOW_6 + ABOVE_10).each { |row|
      return row[1..3] if rim_width_in == row[0]
    }
    raise("no match for model :actual, width #{rim_width_in}")
  end
  params = MODELS.fetch(model)
  case model
  when :simple, :basic
    b = MM_PER_INCH
    params.map { |a| snap(a + b * rim_width_in) }
  when :linear
    params.map { |(a, b)| snap(a + b * rim_width_in) }
  when :best, :extended
    params.map { |(model, a, b)|
      snap(case model
           when :logarithmic
             a + b * Math.log(rim_width_in)
           when :linear
             a + b * rim_width_in
           when :power
             a * rim_width_in ** b
           else
             raise("unknown model: #{model}")
           end)
    }
  else
    raise("unknown model: #{model}")
  end
end

Instance Method Details

#bounding_box ⇒ Object 



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# File 'lib/fitment/combo.rb', line 188

def bounding_box
  [[short_width, tall_width].max,
   [short_height, tall_height].max,]
end

#increase(other) ⇒ Object Also known as: clearance

returns [inside increase, outside increase, diameter increase] for each of :wheel and :tire



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# File 'lib/fitment/combo.rb', line 196

def increase(other)
  short_width_increase = other.short_width - self.short_width
  short_height_increase = other.short_height - self.short_height
  tall_width_increase = other.tall_width - self.tall_width
  tall_height_increase = other.tall_height - self.tall_height

  # smaller et on other wheel moves it outside; more inside clearance
  et_decrease = self.wheel.et - other.wheel.et

  halfwidth = short_width_increase * 0.5
  wheel = [halfwidth - et_decrease, # inner expansion
           halfwidth + et_decrease, # outer expansion
           short_height_increase]   # height increase

  halfwidth = tall_width_increase * 0.5
  tire = [halfwidth - et_decrease,  # inside expansion
          halfwidth + et_decrease,  # outside expansion
          tall_height_increase]     # height increase

  { wheel: wheel.map { |flt| flt.round(2) },
    tire: tire.map { |flt| flt.round(2) }, }
end

#report(other) ⇒ Object 



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# File 'lib/fitment/combo.rb', line 220

def report(other)
  increase = self.increase other
  wheel = increase.fetch :wheel
  tire = increase.fetch :tire

  rpt = []
  rpt << "Wheel: %s > %s" % [@wheel, other.wheel]
  rpt << "  Inside extension:   %.1f mm" % wheel[0]
  rpt << "  Outside extension:  %.1f mm" % wheel[1]
  rpt << "  Diameter extension: %.1f mm" % wheel[2]
  rpt << "Tire: %s > %s" % [@tire, other.tire]
  rpt << "  Inside extension:   %.1f mm" % tire[0]
  rpt << "  Outside extension:  %.1f mm" % tire[1]
  rpt << "  Diameter extension: %.1f mm" % tire[2]

  rpt.join "\n"
end

#short_box ⇒ Object 



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# File 'lib/fitment/combo.rb', line 172

def short_box
  [short_width.round(2), short_height.round(2)]
end

#short_height ⇒ Object 



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# File 'lib/fitment/combo.rb', line 168

def short_height
  Fitment.mm(@wheel.diameter) + TIRE_EXCESS * 2
end

#short_width ⇒ Object 



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# File 'lib/fitment/combo.rb', line 164

def short_width
  Fitment.mm(@wheel.width) + TIRE_EXCESS * 2
end

#tall_box ⇒ Object 



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# File 'lib/fitment/combo.rb', line 184

def tall_box
  [tall_width.round(2), tall_height.round(2)]
end

#tall_height ⇒ Object 



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# File 'lib/fitment/combo.rb', line 180

def tall_height
  @tire.od_mm
end

#tall_width ⇒ Object 



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# File 'lib/fitment/combo.rb', line 176

def tall_width
  @tire.width
end

#to_s ⇒ Object 



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# File 'lib/fitment/combo.rb', line 131

def to_s
  [@tire, @wheel].join(' ')
end

#validate! ⇒ Object 



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# File 'lib/fitment/combo.rb', line 159

def validate!
  validate_diameter!
  validate_width!
end

#validate_diameter! ⇒ Object

Raises:



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# File 'lib/fitment/combo.rb', line 135

def validate_diameter!
  wd, twd = @wheel.diameter, @tire.wheel_diameter
  raise(DiameterMismatch, "wheel: %i; tire: %i" % [wd, twd]) if wd != twd
  true
end

#validate_width! ⇒ Object

Raises:



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# File 'lib/fitment/combo.rb', line 141

def validate_width!
  msg = "tire width %i %s %s %i for wheel width %i"

  min, max45, max = self.class.tire_widths(@wheel.width, @model)
  raise(MinError, "no min available for width %i" % @wheel.width) if !min
  if @tire.width < min
    raise(MinError, msg % [@tire.width, '<', 'min', min, @wheel.width])
  end
  if max45 and @tire.ratio <= 0.45 and @tire.width > max45
    raise(Max45Error, msg % [@tire.width, '>', 'max45', max45, @wheel.width])
  end
  raise(MaxError, "no max available for width %i" % @wheel.width) if !max
  if @tire.width > max
    raise(MaxError, msg % [@tire.width, '>', 'max', max, @wheel.width])
  end
  true
end