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    String alignment setup spreadsheet

    I wanted to share the my alignment spreadsheet with this community. It's applicable to anyone doing a string alignment at home, with whatever tools and methods you're using. I previously shared a link to a similar version in someone else's thread, but I have progressed this file a bit since then.

    Google docs to my setup spreadsheet LINK HERE

    Link to SmartStrings Instructions

    Note: the SmartStrings link changes from time to time so I've uploaded their PDF. It explains how to actually perform an alignment with strings. Once you understand the principles, my setup spreadsheet (link above) and the text below will make way more sense.
    SmartStrings Owner's Manual_v1.pdf


    While this is not a full flown DIY, I still thought it was worth sharing. The next time I do an alignment I will take photos and turn this into a true DIY. If you nerd out on setup, you may find this file useful. If you lack patience, you might want to look elsewhere. I wish I had something like this when I started doing alignments, so hoping others will find it useful

    Fundamentally, all string alignments start by creating a perfect box around the car (with strings) and then taking measurements from that box. I created this file several years ago and have tweaked it for accuracy, ease-of-use and repeatability whenever I did an alignment. I've used this for the M3, but also for other vehicles so the file has had probably 15 or so iterations to get to what it is now. It is the result of a LOT of trial and error, including screwing up the formulas within the spreadsheet and wondering why the car was doing super strange things after completing what I thought was a "perfect" alignment. I also learned I was taking measurements inconsistently and/or setting up the string inconsistently, so I've attempted to make the file as easy to use as possible. In a game where you are measuring down to a realistic 0.5mm of accuracy, a millimeter off here and there really adds up.

    When I first started doing my string alignments on my own (without the help of a race shop), I screwed some things up royally. I had everything from the car dog-legging down the road, to pulling to one side under steady state, to pulling to one side under acceleration. I learned (far to slowly) that the key to making any an alignment work is a developing repeatable system. That starts with a dead-nuts-accurate setup. To that end, row 1 of this file is a reminder for me to follow the detailed steps contained within the file, even if I think I remembered everything from the last alignment. I don't do alignments everyday, so it's easy to forget a step that can have negative impacts which compound with every subsequent step.

    Quick aside: I got incredibly frustrated by shops with the $80k laser alignment rigs that would have me driving down the road holding the wheel to one side in order to go straight. It all comes down to who is doing your alignment. Since alignments are typically flat fees, there is sometimes little incentive for the operator to take their time to really nail the alignment. After working with some race shops and helping doing alignments on my car, I decided I'd just start trying this on my own. When done right and combined with a fair share of patience, I firmly believe using strings nets you the best possible alignment, given other influencing factors that can impact a quality alignment at a typical shop. 100% this is my opinion, but it's also been my experience.

    Measuring alignments is 100% about angles and this spreadsheet solves for angles in either degrees and radians using some basic right-angle triangles calcs. I casually say "basic calcs" but apparently I had no issues screwing them up over the years. Thus...

    This file has a few key components:
    • The file has light yellow shaded boxes where you plug in your measurements. All the calculated values then show up in dark blue font with no shading.
    • With string alignments, you measure toe by comparing the distance from the string to wheel face at the front/leading edge of the wheel. Then take the same measurement from the rear/trailing edge of the wheel. The difference in those two measurement is toe at a given wheel and you here it quoted "1mm toe-in" for example. However, 1mm of toe (be it toe-in or toe-out) on a 15" wheel is materially different than on a 20" wheel. Thus, the diameter of the wheel affects the calculations if you're trying to get to degrees or radians, which I am. I drive towards end results quoted in degrees, rather than "1mm of toe in/out" as it's more accurate. After all, an angle is an angle. All that to say, the first step of this spreadsheet in row 5 is to measure the actual wheel diameter as it is used in the formulas which tell me what 1mm of toe equates to in degrees. I run a 18" wheel and at the farther point of the wheel where I measure equates to 488.95mm (19.25 inches). Once you have the wheel diameter entered in cell E5, the rest of the spreadsheet will work.
    • Next is setting up the strings or the "box" around the car. This is super tedious. You not only need the box perfectly setup when looking at the car from above, but also want it at the same height when viewed from the side. I try to align the string so it's the same height as the axle at each wheel. To do this, I start by eye-balling the string height to get it in the ballpark. I then take 2 measurements off the vertical axis of the wheel (each wheel!) to the string, calculate the average - which is done by plugging values into the spreadsheet. When my left rear and right rear are the same, and then my left front and right front are the same, I know I have a perfect box. This is the table the STRING SETUP table starting in row 9.
    • This file assumes that any corner balancing is done (ride height is set) and camber & caster are set before moving onto the final step which is setting toe. Note: I do not have caster in this spreadsheet as my car doesn't have adjustable caster... but that would need to be set before toe as well.
    • Cell V54 has a "Toe in working table" where I plug in the front vs rear edge values to get to toe. After taking umpteen measurements, I seem to begin forgetting the numbers I just measured just 5 seconds earlier. So I created this table to enter the values in real time and let it calculate toe for me. It solves for toe in which is represented as a positive value, or toe out as a negative value.
    • Around row 74, I started verifying my Excel formulas using a simple right triangle calculator on the internet. This is really just proofing my work. There is also the factory specs per the Bentley's manual for reference only.
    • Row 91 - explains my setup process in detail, step by step and in the right order.
    • After that is how to set preload and ride height on my BC Racing coilovers. They are by no means high end kit, but for how I use the car work just fine. They came with the car and when they need to be replaced, I'll likely swap out for something else. But honestly, they are good value for money. I will dive into flat ride at some point...
    Keep the shiny side up,

    Bryan

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    Last edited by Casa de Mesa; 10-23-2021, 08:12 AM.
    Build thread: Topaz Blue to Shark Blue

    #2
    This is great! Gearing up to get a Smart Strings set up so this will be my guide!

    Comment


      #3
      Thanks for the great write up! Lots of work here.
      I have been fighting trying to get an alignment. Great alternative. And I know it will be done properly.

      Comment


        #4
        Originally posted by Kdubski View Post
        This is great! Gearing up to get a Smart Strings set up so this will be my guide!
        Originally posted by PowerSax View Post
        Thanks for the great write up! Lots of work here.
        I have been fighting trying to get an alignment. Great alternative. And I know it will be done properly.
        Hope it helps! I have more hours than I care to admit in this but got tired paying for subpar work. There ARE good shops out there, but once you get this system down, you can also *relatively* quickly try different alignments. Saving the setup numbers in this spreadsheet allows you to get the strings setup much faster.
        Build thread: Topaz Blue to Shark Blue

        Comment


          #5
          Great write up. I'll certainly use it.

          One thing to add. I recommend taking a steering angle sensor (SZL) measurement before adjusting toe and get it to zero. It will be hard to zero because the SZL is super sensitive. Believe it or not, this makes a HUGE difference. You can start off with a reading if you know the SZL setup correctly. If the steering rack has been disconnected, zero might not actually be dead center, may need to check that.

          And that is the issue with 99.99% of shops - they eyeball the steering angle, probably leaning in through the door window. When you take a reading from the ECU...you're gonna find they are going to be way off.
          Last edited by bigjae46; 10-24-2021, 02:04 PM.

          Comment


            #6
            Thanks for posting, next time I do mine I'll certainly have to use it!

            To keep the steering straight I machined a replica of the TMS rack centering tool. However, I think something is slightly off with its length, my car drives straight while on-centre with that tool seems to be ever so slightly to one side. But, my tires also have severe camber wear which likely induce a moment, so that is a likely cause as well.

            As the poster suggested above perhaps I should use this tool, then double-check with INPA for what the steering angle sensor reads.



            Sent from my SM-G781W using Tapatalk

            Comment


              #7
              I'll be on the lookout for the full blown diy. Having two kids makes it hard to trial and error with the limited time. Thank you for all the work!

              Comment


                #8
                Originally posted by bigjae46 View Post
                Great write up. I'll certainly use it.

                One thing to add. I recommend taking a steering angle sensor (SZL) measurement before adjusting toe and get it to zero. It will be hard to zero because the SZL is super sensitive. Believe it or not, this makes a HUGE difference. You can start off with a reading if you know the SZL setup correctly. If the steering rack has been disconnected, zero might not actually be dead center, may need to check that.

                And that is the issue with 99.99% of shops - they eyeball the steering angle, probably leaning in through the door window. When you take a reading from the ECU...you're gonna find they are going to be way off.
                Good point. I'll add this to the spreadsheet.

                Once I got INPA setup, I checked the steering angle sensor after the alignment and if required, reset it. However, it's always been at 0.00 (or green or whatever INPA shows you, can't remember what it actually spits out). I think because I started locking the steering wheel perfectly level per my comments below. But checking SZL before locking in the steering wheel is a great idea.


                Originally posted by timmo View Post
                Thanks for posting, next time I do mine I'll certainly have to use it!

                To keep the steering straight I machined a replica of the TMS rack centering tool. However, I think something is slightly off with its length, my car drives straight while on-centre with that tool seems to be ever so slightly to one side. But, my tires also have severe camber wear which likely induce a moment, so that is a likely cause as well.

                As the poster suggested above perhaps I should use this tool, then double-check with INPA for what the steering angle sensor reads.


                I have the Turner Motorsports rack tool. Every time I use it, I end up with the steering wheel too far to one side (slightly left or right, depending on what side you put the tool). It annoyed me to no end.

                So now I take a ~6 foot piece of electrical conduit, pass it through the side windows (rolled down), resting it on the tops of the doors. I then take bungee cords and "lock" the steering wheel perfectly level by wrapping the cords around the wheel at the 9 and 3 o-clock positions and then to the conduit.

                Since I started doing this, the steering wheel is always perfectly straight. Also, checking steering angle sensor with INPA afterwards, it's always been at zero with this approach.
                Build thread: Topaz Blue to Shark Blue

                Comment


                  #9
                  Great spreadsheet Casa! But I am bumping this to the top with a dumb question after reading the spreadsheet section about setting rear ride height. I believe the necessity for tightening the rear shocks at ride height is for the OEM shocks that I believe use a rubber bushing. The coilover kits I have seen use a bearing in the rear shock that rotates. These should not require preload - correct?

                  Comment


                    #10
                    Originally posted by eacmen View Post
                    Great spreadsheet Casa! But I am bumping this to the top with a dumb question after reading the spreadsheet section about setting rear ride height. I believe the necessity for tightening the rear shocks at ride height is for the OEM shocks that I believe use a rubber bushing. The coilover kits I have seen use a bearing in the rear shock that rotates. These should not require preload - correct?
                    I always thought it had to do with the radial play between the bolt and inner sleeve (which would still be an issue on a spherical), but maybe you're right.

                    Comment


                      #11
                      I spent a lot of time getting all of the bars square but it was a waste of time. Just need to get the string centered from top to bottom on each corner and then same distance between left and right on each axle. First two times took forever. I've marked the bars and mounting points on the bumpers which speeds up the setup.Took 10 minutes to setup last time...maybe I just got lucky.

                      But once you get it down...it's very satisfying!​

                      Comment


                        #12
                        Originally posted by eacmen View Post
                        Great spreadsheet Casa! But I am bumping this to the top with a dumb question after reading the spreadsheet section about setting rear ride height. I believe the necessity for tightening the rear shocks at ride height is for the OEM shocks that I believe use a rubber bushing. The coilover kits I have seen use a bearing in the rear shock that rotates. These should not require preload - correct?
                        Hey eacmen - this is a BC Racing coilover thing for the most part. I'll edit the spreadsheet to reflect this. After re-reading this, it's technically not accurate for even the BC setup. Sorry for the confusion.

                        The BC Racing rear shock has a threaded sleeve (with the lower mounting point attached to it) that threads onto the shock body. This allows for optimizing shock travel by setting it for a static ride height, which is accomplished by adjusting the spring perches (not the shock - it's not a true coilover setup like most M3 rear setups). Disconnecting the lower shock bolt allows you to rotate/thread the shock body up or down or up on the damper itself, which changes the mounting point of the shock. So once you have ride height set, you can then optimize the shock length based on that static ride height.

                        bigjae46 not totally following. Do you mean that you didn't square up the "string box" making a perfect rectangle? You just got it close so it was slight parallelogram? Not totally tracking what you're saying but I'm all for time saving tips because setting up the box is such a PITA.
                        Build thread: Topaz Blue to Shark Blue

                        Comment


                          #13
                          eacmen Here is a video that explains the process I attempted to describe above:

                          BC, Racing, Suspension, coilovers, Preload, Seperate, Spring, Shock, Low, Performance, Tuning


                          3 min long, about 2 min in they start talking about preload. It's not an E46 M3 in the video, but the concept is the same.
                          Build thread: Topaz Blue to Shark Blue

                          Comment


                            #14
                            Originally posted by Casa de Mesa View Post
                            bigjae46 not totally following. Do you mean that you didn't square up the "string box" making a perfect rectangle? You just got it close so it was slight parallelogram? Not totally tracking what you're saying but I'm all for time saving tips because setting up the box is such a PITA.
                            The square tube frames that hold the long round rod. I was trying to make sure those were square at every 90 deg connection but it was a waste of time. Mostly because I have different ride heights at each corner.

                            The box can be a parallogram as long as the left to right distances on a given axle are equal. IIRC, the front was further than the rear from the string.

                            So from the center of the wheel to the string if the LR is 10mm, the RR needs to be 10mm. Then my front was something like 15mm LF and 15mm RF.

                            Comment


                              #15
                              Originally posted by bigjae46 View Post

                              The square tube frames that hold the long round rod. I was trying to make sure those were square at every 90 deg connection but it was a waste of time. Mostly because I have different ride heights at each corner.

                              The box can be a parallogram as long as the left to right distances on a given axle are equal. IIRC, the front was further than the rear from the string.

                              So from the center of the wheel to the string if the LR is 10mm, the RR needs to be 10mm. Then my front was something like 15mm LF and 15mm RF.
                              Ahhh got it. This makes sense now. The parallel part of the parallelogram must be on the sides of the car, but the front and rear bars do not need to be parallel. I'm picking up what you're putting down now.

                              Yeah, I never worry about a perfect box with 90 degree corners, just that the sides are parallel and equidistant to the reference points (i..e, a hub, machined wheel surface, etc.). That in an of itself is enough of a PITA for me to manage!
                              Build thread: Topaz Blue to Shark Blue

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