Suspension Geometry Calculator

This utility can be used freely by any individual. Commercial use of this utility is strictly forbidden without the owners written consent. Email me at huwcdavies@hotmail.com for more information.

Normal settings (drag the icons to change pickup points)
Camber degrees
Upper wishbone length mm
Upper wishbone angle degrees
Lower wishbone length mm
Lower wishbone angle degrees
Distance between mounting points on hub mm
Distance between mounting points on chassis mm
SAL (distance between the intersection of wishbones and the hub) mm
 
Deflection (drag the icon up and down)
Vertical mm
Horizontal mm
Camber degrees
 
Scale
 
 Key Chassis Wishbones Hub
       
 
Links: Below is the url to link to this page retaining the current data. Feel free to add this link to your site.
 
Hints: From the Competition Car Suspension book.
 
Short SAL (500 – 1000mm) gives very good roll centre location, keeps the outer wheel vertical in corners, but going badly to positive camber in droop and negative in bump (accelaration squat and braking).
 
Long SAL (1800 – 4500mm) provides lower roll centres but less control over their sideways movement, minimal scrub (track variation), poor outer wheel control going into positive camber, but only small camber change in bump/droop.
 
Medium SAL (1000 – 1800mm) is the transition area between long and short with, as you might expect, a bit of this and a bit of that.
 
Ultra-long SAL (near parallel) provides excellent vertical control of very low roll centres but possible enormous sideways movement, wheel angles virtually unaltered in bump/droop but very poor control of wheels in roll, with near equivalency to body roll angle.

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35 Responses to “Suspension Geometry Calculator”

  1. Jon, on April 27th, 2009 at 12:23 am Said:

    Works great, would also be nice to have one in standard, but thats me being lazy, so this works fine

  2. Huw, on April 27th, 2009 at 9:19 am Said:

    Hi Jon, I do have a mcpherson calculator as well but, I haven’t added it to the new layout yet. Huw

  3. Ant1Xr1st, on April 28th, 2009 at 12:57 am Said:

    It’s isn’t working in Firefox and Safary in Mac OS X

  4. Huw, on April 28th, 2009 at 8:58 am Said:

    Okay, problem noted. It did work in Firefox. I’ll have a look.

  5. tony, on May 1st, 2009 at 9:07 pm Said:

    Hi Huw
    can’t seem to get it working.
    figures are locked
    and all I have is 3 colour bars and 4 4 point icons
    any ideas or do you have a copy you could email me

    regards
    tony
    running firefox

  6. Ian, on May 26th, 2009 at 7:25 am Said:

    Huw,
    This is a great suspension calculator.
    I have 2 small problems when using it:
    1. My lower wishbone length is 470. The animation screen is too small to show it. Can you make the animation screen a bit bigger to allow for longer wishbone lengths?
    2. I’m constantly having to scroll up and down during my setup to the numbers and to the animation.
    Can you try to fit it all to one page size to make it easier to use?
    Thanks and good luck with your racing season
    Ian

  7. Huw, on May 26th, 2009 at 9:41 pm Said:

    Thanks for the constructive comments Ian. I will have a look when I next have a chance. It may not be for a couple of weeks though. Huw

  8. Jeroldray, on June 1st, 2009 at 3:54 pm Said:

    Thank you! Thank you! Thank you!…The trig was giving me a headache….On question; I am going to widen my wheel track by 4″ then run 5″ back space on a 8″ wheel, which will give me a positive scrub of 2 5/8′…My current scrub is 3 5/8 and a gain of Cam per 1″ of up travel is 1 degree, my wider track will limit this to .8 gain for the same travel…Would you do it, it will never see slicks- just street fun, and will probably have a .8 to .9 static negative camber to start with…thanks for your insight

  9. Peter, on June 2nd, 2009 at 1:30 pm Said:

    Hi, Great calculator. I also suggest larger input perameters be allowed as my lower wishbone is 540mm and will not fit on the screen.
    cheers
    Peter

  10. Ashish Baidyanathan, on July 30th, 2009 at 7:53 pm Said:

    Mr. Huw, can u include caster change,toe angle,tire scrub,rear swing arm length too..that will be very usefull..
    Thnaks for the fascinating calculator though :) .

  11. Mxer75, on October 3rd, 2009 at 12:27 am Said:

    Very helpfull. can u make it so we can fill in the fields above with our own numbers, That way its more accurate to what pwople are fabricating. Thanks

  12. dereck, on October 31st, 2009 at 2:57 am Said:

    Great calculator!
    Would it be possible to add the ability to add tie rods to the calculator so bump steer can be observed and corrected?
    Thanks

  13. Gene, on December 13th, 2009 at 5:50 pm Said:

    Great calculator. Thanks for adding “Scale”. MBN sends member this way to learn about suspension modeling and it is tremendously helpful.

  14. Javier, on January 23rd, 2010 at 9:32 pm Said:

    Good job!
    Could you post the old mcpherson calculator please?

    Thanks!

  15. jezza, on March 1st, 2010 at 11:45 pm Said:

    does anyone know of a site that could help me with set ups, what will effect certain problems i already have. such as bump steer, very twitchy at high speed, and so on. any help or direction would helpful

  16. Woz, on April 6th, 2010 at 1:42 am Said:

    Hi Huw, I’d also be very interested in the MacPherson Strut calculator, apologies if it’s been added then removed again since Jon’s request.

    Woz

  17. Huw, on April 6th, 2010 at 7:51 am Said:

    I’ll see if I can dig it out.

    Huw

  18. Andrew, on April 21st, 2010 at 9:02 pm Said:

    Great calculator, I would like if I could enter in values for the measurements though instead of just dragging the points.

    -Andrew

  19. TEO, on May 15th, 2010 at 10:19 am Said:

    Great calculator, well done, magnificent job….
    I´d be interested in calculating on mcpherson struts…I´ve read you have a calculator for this…are you going to put it on here as well?…

    Thank you and congratulations.

  20. TEO, on May 15th, 2010 at 2:33 pm Said:

    congratulations

  21. John, on May 17th, 2010 at 9:42 pm Said:

    Really cool tool, would love the macpherson one though!

  22. Dirtyminds off road, on May 20th, 2010 at 9:17 pm Said:

    this is really cool, I also like the idea stated above about entering my own numbers, and adding tie rods.Keep it up and thanx. Steve

  23. Joe Ellis, on August 4th, 2010 at 5:44 pm Said:

    I would like the MacPherson one too. Keep up the good work.

  24. Wrozbita Roland, on September 10th, 2010 at 3:15 pm Said:

    Nice post

  25. scott, on September 28th, 2010 at 2:48 am Said:

    Thank you for making this available free for everyone. It really helped me with my project

  26. toyota parts jobs, on November 17th, 2010 at 12:29 pm Said:

    I am really loving this website but I’m having issues with getting the rss feed to come up on Google Chrome. Any help? Thanks!

  27. terry o, on January 3rd, 2011 at 11:37 pm Said:

    useful tool. thanks a lot. helped me with some options
    would be really helpful if drawing and data was on 1 page.
    it would be great if data could be directly entered
    is there any way to save the data and come back to it..?. it defaults to some pre-set data by the looks

  28. T.J., on March 9th, 2011 at 9:26 pm Said:

    Hello;

    When the mcpherson geometry calculator?
    would be really helpful!
    thank you

  29. Örjan Brattberg, on March 16th, 2011 at 7:57 am Said:

    Hi
    Very nice modelling.
    I just wonder about “Camber” in the static information.
    Should it not be “King pin” inclination to vertical?
    Best
    Örjan

  30. Huw, on March 16th, 2011 at 9:31 am Said:

    Hi Örjan,

    Yes, I guess it should be King pin inclination to vertical, but I prefer the simpler term of camber. This is probably more understandable for basic users.

    Regards,
    Huw

  31. Dan A in Oregon, on March 23rd, 2011 at 1:30 pm Said:

    Can you allow us to input our own demensions and it move to those parameters? Thank You Again.

  32. Dan A in Oregon, on April 4th, 2011 at 12:38 pm Said:

    Can you add a scrub measurement in to the diagram. I’m using this for long travel off road suspension. Thanks

  33. Stabilny Hosting, on July 9th, 2011 at 2:42 am Said:

    Thank you very much for this article :)

  34. jason_m, on October 20th, 2011 at 7:34 pm Said:

    Could you tell me the basics and how to go about designing a trailing arm suspension. If the suspension is mounted in such a way that the axis of rotation is parallel to the wheel axis and horizontal and perpendicular to the direction of motion.
    Conflict arises when the propeller shaft comes into the picture.

  35. john, on November 3rd, 2011 at 11:19 am Said:

    Malicious virus lives under suspension calculator, Try it and see.

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