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How To Check The Drive Wheels For Trueness

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  • #16
    Originally posted by davejr View Post
    The biggest reason I use nothing but the NEW S1 tires on Slot it cars, is they are perfectly true. I now take the tires out of the bag, mount them on a Slot it car, and just race it. You don’t even have to sand these new tires for any reason, other than to get the shiny surface off.
    Oh contraire.... We have found S1's, especially S1's, to not only to be seemingly made from differing compounds, but requireing trueing in every instance.

    We race a totally spec class of 55 Chevys with the S1 as the spec tire, glued and trued to Slot It rims. The cars performance is effected posatively or negatively when the rim/tire combo is switched from one car to another. We are changing to a tire that is of a more consistant compound

    Glue any tire to a rim, chuck it in your Hudy and rub your fingernail across the surface. The vibration you feel is exactly what is happening when that tire surface is on the track. The #1 Shoreline tuning tip, exposed.....

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    • #17
      I have found that even Slot.It wheels (some, not all) run out, due to an oversized hole. The amount of runout is small, but when you drive the car, it breaks loose suddenly in the corners. When I switched to other Slot.It wheels from a different batch, this car smoothed out very much. Only the rims were changed. I have trued several Slot.It rims on my lathe, and it only solves the problem sometimes.

      For casual running, these wheels are fine, but for serious competition, it cannot be.

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      • #18
        Mongo, I had hoped that you would have remembered that oath of silence that you took. Now you have let the cat out of the bag. I could point out that having round wheels is much more important if you race your cars, especially without magnets. If you are going to risk damaging some shelf queen you can just as easily knock off the antenna and mirrrors if the car has crooked wheels.

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        • #19
          I wrote to Slot it and asked why the latest batch of S1 tires performed so much better.

          Each tire is measured independently on the skid pad.

          Maurizio responded and told me the only difference in the S1 tires was the cleaning up of the molds to make them perfectly true.

          This has proven to be true in the last 10 sets of tires I have purchased, except for one tire. It was mistakenly mixed in with the new sets.

          There is no way to identify the new S1s from the original tires, except by their performance and that they run perfectly true.

          Dave

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          • #20
            Originally posted by RichD View Post
            Mongo, I had hoped that you would have remembered that oath of silence that you took. Now you have let the cat out of the bag.
            Rich ... Mike has been saying this forever. If they dont listen to him, they arent going to listen to me...



            Dave, That is great if Slot It fixed their molds. We have yet to find a tire from ANY manufacturer that is "perfectly" true. Close to true, maybe, but not perfectly.

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            • #21
              When I take a new Slot it car and install new S1 tires, run the car for a hundred laps or so until the gloss is removed from the tires.

              Then place the car on my tire sanding fixture, spray some window cleaner on the tires, and I canít measure any movement in the carís chassis with a dial indicator, to me that's true enough.

              Dave

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              • #22
                While we're on the subject, Dave, would you say the chassis jig works better for truing tires than the sandpaper on the skidpad technique?

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                • #23
                  After almost 3 years of enjoying this great hobby and website, I think you guys (specifically Dave Jr.) have pushed me over the edge. All this talk about truing wheels and tires, along with fantastic indepth tests and data from Dave Jr. has compelled me to do a little testing of my own. Tonight i whipped out my trusty interapid model 312b .0005 in. dial indicator and 4 of my favorite slot.it's, along with a set of slot.it wheels I had laying around in my parts bin. I set up my indicator to check runnout of the wheels. The measurements were taken with the chassis secured to a machinist vice and a 9volt battery was apllied to the braids. The results were somewhat surprising and speak highly to slot.it's quality control. All four cars I checked had between .0005 to .002 T.I.R. (total indicator runnout) at the wheel with tires removed. This is very good IMO. I was expecting double the amount. I ran the same test with the tires on (before they were removed) and the incator showed .002-.005in. T.I.R. I also checked for play between the axle and bushings and I found there to be roughly .005in. movement when pushing up and down on the opposite wheel. Not sure if any of this helps anyone but I think spending time truing up slot.it wheels on a lathe will add little to the performance of most slot cars. It also showed me I need to build a tire truing jig to better true my Tires.
                  Regards,
                  John

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                  • #24
                    My first post in this thread was strictly concerning previously removed plastic wheels from knurled or splined axles.

                    I have not, so far, had any bad Slot.it aluminum wheels. Nor any bad BWA or SuperWheels.

                    My thinking is, though, that for the amount of effort and time required to try to re-true aluminum wheels, one would be better off just getting another set of wheels & attempt to return the out of round ones as defective.
                    =============
                    regarding the "dial indicator measurement" of chassis movement... I missed how the chassis is affixed & how the indicator was affixed in relation to it? That's got to be a rigid mount. Just curious...

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                    • #25
                      Not sure if any of this helps anyone but I think spending time truing up slot.it wheels on a lathe will add little to the performance of most slot cars. It also showed me I need to build a tire truing jig to better true my Tires.
                      Good additional research there, John. I suspect that the majority of aluminium/magnesium/whateverinum wheels are made to much finer tolerances than the plastic ones we get from the manufacturers on the rtr cars (though most, to their credit, to a superb job when it comes to scale accuracy and appearance).

                      It's notable that Slot.it put plastic front wheels on their cars (and I haven't ever seen them criticized except when the tires bind on the inside bits of the bodyshell) and even have them available as aftermarket options, such as the 17 mm black hubs.

                      As a frequent Proxy Host, I would have to say that attention to the details - and perfect truing has to be the most important of all - is the hallmark of the cars which excel. They are a delight, and they sound different and drive differently to any lesser car. Smooth and agile and controllable.

                      When we're dealing with very powerful cars that only weigh around 70 ~ 100 grams on the average, that can spin their rear axles at over 8,000 rpm, then it only makes sense that proper balance in the drivetrain has to be the first essential.

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                      • #26
                        Hard to believe...

                        Originally posted by Wet Coast Racer View Post
                        As a frequent Proxy Host, I would have to say that attention to the details - and perfect truing has to be the most important of all - is the hallmark of the cars which excel. They are a delight, and they sound different and drive differently to any lesser car. Smooth and agile and controllable.

                        When we're dealing with very powerful cars that only weigh around 70 ~ 100 grams on the average, that can spin their rear axles at over 8,000 rpm, then it only makes sense that proper balance in the drivetrain has to be the first essential.
                        Someone finally gets it.....

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                        • #27
                          Robert

                          The sanding fixture works like a cheap lathe. The chassis is held firmly in place and the sand paper is glued to ľ” piece of plastic. The chassis can be adjusted until the high spots of the tires are just touching the sandpaper, and run like this until the high spots are removed.

                          If a tire is round but not concentric to the axle, the tire fixture is the only way to correct this problem, other than using a lathe.

                          The sanding skid pad will remove small high spots on the front and rear tires. It will not correct tires that aren’t concentric to the axle.

                          Slider2

                          The car was placed on the sanding fixture without using the adjustable stop. The tires were on the plastic sanding surface. Window cleaner was sprayed on the sanding surface and tires for a lubricant.

                          The dial indicator was set on the axle bearing holder and the car was run at a low speed. The dial moved back and forth less than .001”. The indicator that I used is quite large but is the only one that measures perpendicular to the work so I could take a video of it in action.

                          I am trying to get my camera to take a video, but for some reason it refuses to focus in the video mode.

                          As I said in an earlier reply, I don’t think it is worth it to try to repair out of round aluminum wheels.

                          Moby Dick, John

                          Thank you for posting your test results. This has been my intention all along, to get everyone to do there own testing to find out what needs to be done to a slot car to improve it, and to post their test results. This way everyone benefits from their findings.

                          Dave

                          PS

                          I think we all get it, some times it just takes more than someone’s opinion to get the ideas across, the actual measured results speak for themselves.
                          Last edited by davejr; 09-10-2008, 06:28 AM.

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                          • #28
                            Yes, now we are getting somewhere.

                            When you compare proxy race results, and see who comes out on top most of the time, no matter which tracks, drivers, and rules, you see how "true" it is that a Hudy, and/or a lathe, and very precise machining of wheels/axles/bearings are necessary for that margin of victory.
                            The winning cars feel silky to drive, and perform as if they are glued to the track.

                            I've observed this for two years in the proxy races, which is why I feel it is important to have a beginner's class in the RAA.

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