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What Is Your Reason For Using Zero Grip Front Tires?

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  • What Is Your Reason For Using Zero Grip Front Tires?

    I have tried a few different methods for making zero grip front tires. I have coated them with Future, spray painted them with clear lacquer, or a real quick way, wrap them with Scotch tape.

    I tried all of these methods on my R&D Jaguar without any positive results. Actually the car lost a little speed because the zero grip tires seemed to reduce the braking effect of the car.

    This time I decided to use the Slot it Zero Grips, SIPT15, to see what they offered. They are made from a compound that has very little traction and have such a small outside diameter the rubber doesn’t touch the track.

    After trying the Slot it Zero Grip tires I removed the front axle assembly and got similar results on the skid pad.

    A set of Slot it 15mm aluminum wheels with S2 tires was installed on the front axle . This setup gave varying results depending on the tire grip.

    The test chassis is a Slot it 956 that has the motor pod attached solidly to the chassis with epoxy and frame stiffening brass angles on the sides.

    The chassis is weighted to simulate it having a body, 73 grams total, with 41 grams on the rear. (see photo)

    These are the skid pad results using a set of un-sanded new S1 rear tires.

    Slot it Zero Grip front tires or no front axle assembly.
    CW….0.745 seconds
    CCW..0.735 seconds

    Slot it aluminum front wheels with S2 tires
    CW….0.780 seconds
    CCW..0.770 seconds

    Slot it aluminum front wheels with S2 tires painted with gloss lacquer.
    CW….0.775 seconds
    CCW..0.765 seconds

    These are the race track average lap times.

    Slot it Zero Grip front tires or no front axle assembly.
    6.820 to 6.850 seconds, top speed 21.9 to 22.1 f/sec.

    Slot it aluminum front wheels with S2 tires.
    6.720 to 6.740 seconds, top speed 21.4 to 21.5 f/sec.

    Slot it aluminum front wheels with S2 tires painted with gloss lacquer.
    6.790 to 6.810 seconds, top speed 21.4 to 21.5 f/sec.

    OBSERVATIONS

    Without the front axle assembly, or with the zero grip tires mounted, the chassis had good cornering speed through the center of the turns. Because the chassis was unstable, the transition into and out of the turns was erratic, causing it to over-steer entering or leaving the turns.

    Riding on the pickup braids the chassis had a little better top speed, but it had more of a tendency to lift the front coming out of the turns without the weight of the front axle.

    I couldn’t detect any visual difference between the gloss coated or uncoated S2 tires, but with the paint removed from the tire tread the car ran faster and more consistent laps.

    CONCLUSION

    For my situation, the Slot it Zero Grip tires or any front tire with low traction, didn’t show any increase in performance.

    Dave

  • #2
    Originally posted by davejr View Post
    II tried all of these methods on my R&D Jaguar without any positive results. Actually the car lost a little speed because the zero grip tires seemed to reduce the braking effect of the car.
    If your car lost speed because of less braking effect, then your original tires were creating a LOT of resistance. That much resistance would cause your car to act loose in the corners, as does all resistance at the front of the car. Have you ever driven a Slot.It Jaguar before getting the front axle unbound from the body post? It's like it's on ice -- tail swinging everywhere. Loosen up that resistance, and the car handles like it should.

    One of the most important things gained with 0-grips is consistency. The tires are less likely to dig in, catch a seam in plastic, or respond to irregularities in the track surface. This contributes to fewer offs. Fewer offs = more speed.

    That said, I don't bother with 0-grips. Whatever gain I see doesn't justify the cost.

    Comment


    • #3
      Your results are probably right, but I must ask if your test chassis really does simulate a real slotcar.

      I think a body might have a higher CoG, but it depends on car type, but more important the body usually have some float, and especially when braking and entering a turn the body gets thrown forward and a lot of weight/force is applied to the front outer tire which makes the car want to tip over. The front tires then works as stabilizing "outriggers" but if the tires have too much grip they tend to "grab" the surface and put a braking force on the chassis. On a big wide well balanced group C chassis this might not feel like much, but on smaller narrower car the "grab" usually gets so strong that the car lifts over on the side and lifts the guide out of the slot (narrower track = increased corner grip).

      Your tests are nice Dave, but some aspects of tuning are probably too comprehensive to be explained by testing a single isolated factor, and it's the combination of many factors that makes the outcome. You can set up three different cars with very different methods, and still get them to perform very similar, just look at how close many of the RAA cars are.

      Comment


      • #4
        Originally posted by ElSecundo View Post
        If your car lost speed because of less braking effect, then your original tires were creating a LOT of resistance. That much resistance would cause your car to act loose in the corners, as does all resistance at the front of the car.
        Yeah, I found that out the hard way too. Racing with the guys from PSSRA a few years ago, we were racing stock scaley NASCARs. Mine had been one of the faster cars at the end of the previoius season, but I wanted to "freshen" it for a new season, so put a new front guide and braids on it. To ensure that everyone got as equal a car as possible, the group had hand-out tires. In the first race of the new season, I was convinced that I had gotten the worst set of tires possible, but the braking was fantastic. The second race wasn't quite as bad, and as the season went on it seemed I kept getting better and better tires, but the braking went away slightly. It didn't occur to me until after the third of fourth race that maybe the guide was binding in the slot. I sanded the sides of the guide slightly, and in the next race the car just flew! (Slaps head and says "Doh!")

        Comment


        • #5
          Dave, I'd like to respectively poke a few holes in your testing:

          1) You are testing using a car that has a floating front end. The front tires do very little in this situation. Not matter what you use for a front tire, it should make little difference.

          2) Even though you weighted the chassis down, these cars react very differently with a body on them. A high CG car uses the front tires to stop leaning. Low CG cars do not use the front tires at all.

          3) I find on my skid pad that there are some unique dynamics going on where the amount of grip a front tire may have little difference on the outcome of the test using the pad. My testing has shown fast cars have a good amount of chassis flex or a floating pod. With these type of cars (fast), once I reach my fastest point on the pad with a car, the inside front tire is in the air which says the only part of the outside tire that is touching is the very outside section of the tire. No matter what type of tire you are using, there is only a small cross section of tire that is on the track. In theory, a small cross section of a single tire should have little impact on a skid pad.

          What the skid pad cannot measure is the transition from the straight to the turn. In this case both tires are on the track and may impact the transition.

          I cannot argue that zero grips may do little but I do have a theory. Use a solid front end like most slot cars have and if both front tires are planted, if a car is in a turn and the front tires do start to drag at all, that has to have an impact on the handling of the car. Who knows, maybe it works well for people who have hairpin turns or big sweepers. It may not help anyone at all but since most of us use front tires, why not just use zero grips? I know all of my fast club and proxy cars use zero grips and some even use independent front ends. They may not work for everyone, but they work for me.

          Mike

          Comment


          • #6
            ElSecundo

            The reason I think the Jag lost braking effect was just the rolling resistance of a properly set up front axle. As long as the car is accelerating the weight of the nose on my cars is riding on the braids.

            When the brakes are applied the front wheels hit the track and add a small amount of braking effort. With the zero grip tires I didn’t get this effect.

            I don’t have any seams in my track where a tire would dig in.

            In recent years I have never put a car on the race track without first disassembling it and making sure everything was operating properly.

            356speedster

            The test chassis is just for testing individual items. The center of gravity is as close as I could get it to simulate it having a body.

            When testing an item I don’t want any tunable adjustments in the chassis, I only want the item being tested influencing the results of the test.

            Tuning a complete car is another subject altogether.

            Smokeio
            Mike

            The front tires on the test chassis do not float and are in constant contact with the track ,except under acceleration when the chassis is riding on the braids.

            There is no body for a reason, I don’t want it interfering with the test results.

            No matter where the center of gravity is located, if the tires normally ride on the track they will have some effect on the handling of a slot car.

            Removing the front axle of the test chassis gave the best test results on the skid pad. Depending in the slip angle needed for the drive tires to get the maximum speed out of the chassis, the angle of the front tires could cause some drag or rolling resistance. Any out of round condition of the front tires will also effect the rear tires performance in a turn.

            This I why I remove the front axle and only use one rear tire and a skid bar when testing a new tire. I just want to know the performance of that tire on the skid pad. (see photo)

            After finding the best performing parts using a test chassis, all of these parts are installed on my R&D Jaguar and the testing starts over.

            Sometimes the best parts don’t show an improvement on the skid pad or race track until the car is retuned for these parts.

            Sometimes the best parts in combination on a car don’t result in any improvement in a particular cars performance.

            Dave
            Last edited by davejr; 09-29-2008, 12:44 PM.

            Comment


            • #7
              So far, my best stab at understanding front tires and wheels is that they work well as outriggers to reduce chassis roll on flat smooth tracks. I also use stock RTR Slot.It front tires. I set my cars up with a little weight on the tires, which must touch and roll. I find that the compound makes little difference, but I always try to make them true, to reduce vibration. I have built several cars with independent rotating fronts, but have found no particular advantage, except for one car. That car uses high grip Ortmanns up front, and I felt that independent rotating tires were necessary, as nearly all the weight was on the front tires. This car was fairly successful in a proxy race, but it was also a scale model of a car, and needed the Ortmann repro-Cox front tires to look just right. It also had a pin guide (worst idea yet). In that case, independent rotating tires were important.


              I use regular size Zero-Grips (SIPT-07) which touch the track on my current-era cars, if only because they fit and can be trued and re-profiled easily. The SIPT-15 low profile 0-grips tires are illegal in nearly every proxy in which I take part, if only because they are such poor representations of actual tires, and look very strange in scale-sized wheel arches. The regular-sized Zero-Grips tend to burnish up nicely after running a while, and definitely don't stick to the track. I give them a moderate crown, so no matter what the attitude of the car, the contact patch is small.
              Last edited by Robert Livingston; 09-29-2008, 09:05 AM.

              Comment


              • #8
                Robert

                Why don’t you like a guide pin? Have you found a performance advantage to using a guide blade?

                When racing with the use of corner marshals, they seem to have less trouble replacing the cars, especially if the blade is at an angle to the car. It takes some time to straighten the guide or wiggle the car back and forth until they find the slot.

                Now we use the crash and burn system, and all the cars have guide blades.

                Great looking chassis, I’d like to see the complete car.

                Dave

                Comment


                • #9


                  1962 Ferrari 250 GTO:



                  I had read of the glories and advantages of a guide pin, and I tried them in two proxy cars simultaneously. I quickly found that, although the car is easy to put back in the slot, and the thing is nearly indestructible if you build it right (I used a cutoff .035" Allen wrench inside WD-40 squirt tube sheathing), the car has no spinout-stop, so if you slide the rear beyond the point of no return, you cannot recover it. The car stops. This is death during a proxy, unless you are blessed with the best driver running your car. To compound the problem, when you spin, the braid gets bent, which causes further problems if the marshall doesn't take the time to reset it correctly.

                  I will never build another car with a pin guide.

                  I have a TSRF car with a home made pin, and it also has the same issues. Eventually, the Ferrari and the TSRF car will get regular guides.

                  The only "trick" about building a pin guide is that it should lean backwards, so that the lower end trails the upper end, by about two degrees. When the car slides, the point of contact drops down to the lowest point on the pin, which tends to keep it in the slot. That part works very well. If you have a car that never loses it by spinning out, that car might use a pin.

                  Comment


                  • #10
                    I don't use them at all on my home track. They seem to do little more than make noise as they roll along.

                    Scott

                    Comment


                    • #11
                      Removing the front axle of the test chassis gave the beast test results on the skid pad. Depending in the slip angle needed for the drive tires to get the maximum speed out of the chassis, the angle of the front tires could cause some drag or rolling resistance. Any out of round condition of the front tires will also effect the rear tires performance in a turn

                      Thank you for the clarification. Interesting information as you could also go one step futher by your testing to say it is faster to run without front tires than with them. Kind of the old discussion if a tripod is a faster setup.

                      Comment


                      • #12
                        Robert

                        Good looking car.

                        Smokeio
                        Mike

                        The difference in performance between the skid pad and race track clearly showed the problem with the tires that didn’t touch the track or with no front axle and tires.

                        The car was unstable entering and exiting the turns. The car would tip just enough to unload the inside rear tire and change the contact area of the outside rear tire, causing the car to over-steer and lose time entering and leaving each turn.

                        The car was faster through the center of a turn on the track or on the skid pad, but it couldn’t handle the transitional parts of the track and lost a bit of time, usually greater than a tenth of a second a lap.

                        Dave

                        Comment


                        • #13
                          What diameter is your skid pan as i am going to incorporate one into my "test" track. I call it test as it isn't very big.

                          My scaley DBR 9 would deslot at the front by tipping out of the slot. I added weight at the front. It helped but did not eliminate it. I coated the tires with superglue and it now drives beautifully.

                          Comment


                          • #14
                            Abarth Mike

                            The skid pad is 20.5 inches in diameter. Slightly larger than the smallest turn on the race track.

                            One of the first cars I purchased was a Fly C5R Corvette. In the smaller radius turns the car would bounce up and down.

                            On the skid pad, at low speed, I discovered the swing arm mounted front wheels were trying to tuck themselves under the body.

                            Without being able to view the car close up, in a continuous turn, I would have never seen what the problem was and make the proper modification to the car.

                            Dave

                            Comment


                            • #15
                              Great thread guys, with some very useful info

                              I have a 60 ft Ninco track, but have been having problems with my Scalextric Formula 1 cars being very "temperamental on tight turns. Just going on straight or barrel rolling.

                              After reading this thread I went home, removed the front wheels from the F1 cars, and hey presto, the cars were suddenly behaving.

                              Obviously this is not a permanent solution as we all strive for some reality.

                              If I painted clear varnish on the front tires, would my problem be solved?

                              GG

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