Toyota MR2 Wheel and Tire Calculator Readme

Overview

I created the wheel and tire calculator when I was looking for new wheels for my car. People would always ask, "is this flush?" questions on the MR2 message board, and El Paalo was answering them manually, one by one. With his help, I was able to create a very simple calculator that would tell how close a given input was to flush. From there, I expanded it to have inputs for old/stock wheels, so the calculator could be semi-applicable to any vehicle. Then I added speedometer calculations.

When version 1.0 came out, I had completely redesigned the calculator interface and optimized many of the calculations. I also adjusted its handling of erroneous inputs.

Now, version 1.5.0 is out. The calculator uses Ajax (allowing the data to be received without loading a new page). It has also been optimized far more than I would have thought possible, bringing the total code from about 750 lines to about 450. This new version has visual representations of the flushness and wheel/tire sizes.

What's next? I have no idea! I've implemented everything that I had thought of. The graphics could be nicer, but right now they are extremely fast and use minimal server resources, so I'm not sure how fancy I want to make them.

Directions

Hopefully the calculator is pretty self-explanatory. Simply input the data, check the options you would like, and hit calculate. There are quick-set buttons for 1991/1992 and 1993+ second generation MR2's as well as quick-sets for generic wheel/tire combinations for the new setup. Sometimes it's easiest to click those and then make the changes.

The sideview images use circles to represent the outer circumference of the given wheels and tires. Green represents old values and red represents the new. Brighter colors are for the tires and darker colors are for the wheels. The variables that the image displays may appears slightly off, but this is due to rounding after the calculations are made (so it doesn't affect the image).

The flushview images are specifically for the 2nd generation MR2. There is a 90-degree angle that represents the fender and a gray line that runs straight down it (representing flush). If your wheel is close to flush, it may hide the flush line. Note that the height of the wheel does not change (so the display of a 14 inch wheel looks as height as a 17 inch wheel), but the width does. The old wheel is displayed a couple of pixels lower, because otherwise you would not be able to see the lines from all the overlapping.

Features

The calculator is able to do the following:

• Determine flushness of wheels for a second generation MR2
• Estimate if a front wheel will touch the suspension (based on wheel width only) for a second generation MR2
• Tell how much difference there is for the new wheels vs. the old wheels
• Show differences in tire speeds (and the speedometer)
• Display visual representation of the difference between the old and new wheels/tires (sideview)
• Display visual representation of the flushness of the old/new wheels for a second generation MR2

Bugs and Errors

This paragraph usually stays bug-free because I try to fix problems right away. If the issue requires a lot of work, I post information here and on the calculator page itself.

Keep in mind the calculations are not perfect. For instance, flushness does not take into account your alignment. Tire speeds do not take into account air pressure. Slight differences exist between cars, wheels, tires, etc. so it's impossible to be completely accurate, but this calculator is reasonably close.

Future Plans

This is a list of possible features that might be worked on in the future. I've nearly cleared out the list and the remaining items might never be complete due to low demand/interest. If you have any thoughts or suggestions, feel free to let me know.

• Tell if proposed wheel/tire combo will cause stretched or bludging tire (tricky do to rounding of sidewall, tire pressures, and wheel materials)
• Have an alternate output? Maybe a table or something else?

Revisions

1.5.0

• Calculation results are now dynamic with Ajax
• All code completely rewritten from scratch - improved efficiency
• Added flushview image capability
• Corrected previous "divide by zero" bug
• Made tire speed calculations much more accurate

1.10

• Added dynamic PNG images to show a sideview of the wheel/tire differences
• Corrected a significant bug with the speedometer calculations

1.00

• Complete redesign of front-end
• Added quick input buttons, allowing for fast insertion of old stock values and generic new values
• Added logic to correct inputs (e.g. a wheel width input of "70" is corrected to "7.0")
• Added logic to kill off invalid inputs (e.g. "monkey" or a sidewall of "500")
• Form retains input values (except for erroneous ones) when displaying output
• Error messages are now displayed, detailing what variables were missing or incorrect
• Fixed bug with fractional wheel widths (e.g. 8.5")
• Output goes directly above input screen and is organized by calculation

.90

• New input "radio" buttons allow for easy switching between 91 and 93 stock ("old") values.
• All outputs should now be rounded to two (2) decimal places (previous suspension calcs were up to 8 decimal places... a bit excessive)
• Minor formatting changes
• Fixed "0" offset calculations

.85

• Redesigned input to include only one Tire/Wheel height (as opposed to separate ones) stopping some of the confusion
• Reprogrammed the code to use the correct variables for the change
• Made code more efficient, so it calculates less than before

.83

• Separated front and rear speed change calculations. I made the default calculate only the rear change since that is what the speedo in an MR2 goes off of, but I left the front as an optional check in case anyone was really curious.

.82

• Minor improvements to input screen

.81

• Fixed minor errors, no effect on calculations

.80

• Modified output to display optimal flush values when input is other than flush
• Fixed a significant error in the way that front suspension offsets were calculated for the MKII
• Fixed an error that incorrectly calculated the differences from the old to new wheels

.62

• Fixed another error that displayed the wrong variable for rear wheel differences

.61

• Fixed error that used a front variable for the rear wheel difference calculations

.60

• Removed all ignore variables. In the future, all calculations will take place if the appropriate box is checked

.55

• Separated calc and calc_readme to keep the page a bit cleaner
• Fixed reversed 60 MPH calculations.

.50

• Added 60 MPH calculations

.40

• Added comparing of old and new wheel widths and offsets.
• Fixed negative value for "tucked in from flush" calculations on the front offset
• No input of offsets now gives warning and prevents erroneous calculations

.30

• First beta version, calculator works but only does MKII calculations including flush for front and rear, and suspension for front

.10

• Grab user input variables from rough calc input screen