The Mustang\u2019s problems seem to be due to poor rear-end grip. A light scuffing of the tyres<\/a> vastly improved handling and lap times. Increasing magnetic downforce<\/a> also helped, but that tweak gave the car negative side-effects such as a tendency to tip over and a motor that was running hot.<\/p>\n In this blog post I am going to concentrate on more advanced tyre treatment and adding a little weight to the car. I am sticking with all the standard parts that came with the Mustang and introducing important techniques for future tweaking and tuning.<\/p>\n Tyre Truing<\/strong> is a term you\u2019ll come across wherever slot car tuning is talked about. What it means is sanding the rear tyres flat and \u2018true\u2019 across their surface. The reason slot car racers do this is to get the maximum amount of tyre gripping the track. If the surface of the tyre bulges out \u2013 as it often does on a new car \u2013 only the top part of the bulge will be making good contact with the track, seriously reducing grip in the corners.<\/p>\n To true the Mustang\u2019s rear tyres, we could use the sandpaper-on-track technique used to scuff up the tyres in Part 2 – Tweaking a New Car<\/a>. However, effective tyre truing is a more time-consuming and precise process \u2013 and a more robust set-up is required. There are expensive tyre truers available to buy for \u00a3150-\u00a3250 or more. Most of these won\u2019t do the job on Scalextric axles and wheels \u2013 they are for truing tyres on removable alloy wheels. One type of tyre truer that is designed to take the whole axle and both wheels is produced by both Tire Razor and Overdrive. However, you can make something that works just as well for a few pounds\u2026<\/p>\n My DIY tyre truer<\/strong> is made from a scrap piece of Scalextric track that I\u2019ve cut in half lengthways and then hack-sawed out a slice. At the front, I have soldered wires from each rail to terminals (brass bolts), to which I attach my old Maplins bench power supply set to 12 volts. At the other end of the track piece, I have a square of 6mm-thick mdf sheet that has sandpaper glued to each side \u2013 400 grit on one side and 600 grit on the other. This give a lovely flat sanding block. The base is a 25 x 12 cm piece of mdf, each end braced by a piece of white PVC angle.<\/p>\n It wasn\u2019t a difficult job and I had all the kit and materials lying around. To avoid the soldering and need for a power supply, you can use a Scalextric powerbase, power supply and controller \u2013 the C8545 powerbase costs just \u00a33.95 here<\/a> in the Jadlam store. The plastic and metal connectors will need to be cut from one end to allow the sanding block to sit snuggly. You can slice the track in half length-ways if you want to. You\u2019ll need both hands to concentrate on the car, so a rubber band should be wrapped round the controller trigger to give permanent full power.<\/p>\n **Caution** I don\u2019t recommend sanding tyres when a digital chip is fitted in the car.<\/strong> The added friction of the sandpaper requires more power to go through the chip to the motor. This risks damaging the C7005 retro-fit chip, the C8516 F1 digital plug and older versions of the C8515 standard digital plug. The latest version of the C8515 plug and the Slot.it SP15B chip are both designed to handle more power, but I would still urge caution. It is always advisable to remove a chip before any tyre sanding or truing.<\/p>\n The process of tyre truing is straightforward<\/strong>, but requires patience and care. Sanding too hard and too quick risks damaging the car\u2019s motor, melting the tyres and messing up the sanding block.<\/p>\n The first step is to sand the plastic wheels<\/strong>, which may have lumps and bumps from the manufacturing process that will cause the tyres to be out of shape too. I remove the body from the car and then remove the tyres. The Mustang\u2019s wheels looked pretty good, although there was a slight ridge from the moulding process. I placed the car on the truing track so the motor and wheels spin, holding them up and away from the sandpaper. With the tyres removed, it\u2019s important to be careful of the gears \u2013 especially with a sidewinder car \u2013 you really don\u2019t want to sand down the gear! I move the sanding block to one side, so the wheel comes down on the edge of the block and the rest of the axle is suspended in mid air.<\/p>\n I slowly lower the wheel so it is just touching the sandpaper \u2013 the coarser 400 grit is best for this. You don\u2019t want to push the wheel down. Let the sandpaper gently do its work for five seconds \u2013 a count of \u201c1,000 \u2013 2,000 \u2013 3,000 \u2013 4,000 \u2013 5,000\u201d – and then lift up. After a break of at least five seconds, I lower the wheel for another five seconds of sanding. I repeated this process a few times until the centre of the wheel looks nice and smooth and any moulding imperfections have been sanded away. Then do the other wheel in the same way \u2013 moving the sanding block across. Each wheel took about two minutes of gentle, methodical sanding.<\/p>\n Now it\u2019s time to true the tyres<\/strong>… I replaced them on my nicely-trued wheels and placed the car back on the truing track, the tyres held above the sanding block. Using the 400 grit paper, I went through the same process as the wheels \u2013 gently lower onto the sandpaper, letting the grit do its job for a count of \u201c1,000 \u2013 2,000 \u2013 3,000 \u2013 4,000 \u2013 5,000\u201d and then lift and rest. The tyres grip the sandpaper much<\/em> more than the plastic wheels, and the back of the car will shudder and rattle \u2013 it is important to hold the car steady with both hands, but without pushing down.<\/p>\n On Scalextric cars that have the motor in-line, you will see the motor flex in the underpan when you true the tyres. The shaft and small pinion gear will climb up the crown gear, adding to the rattling noise. This isn\u2019t good. It shows what happens under harsh acceleration on track \u2013 the movement and the poor mesh is a waste of energy that could be powering the car. It also adds wear and tear to the gears. Gluing the motor to the motor mount helps keep everything tight and reduce the noise \u2013 we\u2019ll look at this in a later blog post.<\/p>\n One thing I did need to glue was a wheel! Early on, I noticed one of the wheels wasn\u2019t turning when lowered onto the sandpaper \u2013 it had come loose on the axle. This is an occupational hazard of tyre truing with plastic wheels. I simply pulled off the wheel, cleaned the end of the axle and the plastic hub with a little lighter fluid \u2013 and then added a dab of superglue to the hole and refitted it on the axle. I was careful not to push the wheel too far and risk gluing it to the axle bushing. I left it for an hour to set before returning to tyre truing.<\/p>\n Notice how careful I’m being<\/strong> with the truing process. I could be more speedy – using coarser grit sandpaper, pushing down and truing for longer – but that risks damaging the motor and ruining the tyres. Even with my over-cautious technique, I regularly check the temperature of the motor and the tyres. Hotter than \u201cwarm-ish\u201d and I stop. This is something I do once to a set of tyres, so it is worth spending time to do it well.<\/p>\n The aim of the truing process<\/strong> and repeated five-second sandings is to produce a tyre surface that is perfectly flat and a circumference that is perfectly round. In practice, I am looking at a tyre surface that is smooth and has no shiny spots left \u2013 or perhaps just a narrow ring on each edge. That still gives a rounded \u2018shoulder\u2019 on the edges, which is important. A completely square edge can increase the car\u2019s tendency to tip over. You can create a more rounded shoulder by spinning the wheels and sanding with an emery board. The tyre truing process took me just over ten minutes for the Mustang. Tyre residue did build up on the sandpaper and I brushed it away from time to time with the soft make-up brush in my tool kit. And there was plenty of muck that came off the tyres when I cleaned them on masking tape.<\/p>\n Before truing I ran the Mustang on the SL6 test track and timed a two minute session using the ARC app<\/strong>. The car was fresh from a full service and tyre scuffing \u2013 and I managed a pretty pleasing 24 laps and a best lap of 4.63 seconds, my fastest yet in \u2018standard\u2019 spec. After truing the tyres, another two minute session gave 25 laps and my fastest lap time had plummeted to 4.28 seconds \u2013 quicker than with the magnet tweaks and the best time for the Mustang so far.<\/p>\n Did the car feel different?<\/strong> It did, especially in the tight Radius One corner, where I had loads of confidence to carry more speed. Unlike the stronger magnet tweaks, I wasn\u2019t feeling the car tip \u2013 the rear still stepped out, but only at a much higher speed. I found myself adjusting how I drove the circuit \u2013 there were two short straights where I could now blip the throttle where I couldn\u2019t before. That showed I was able to get on the gas sooner and brake a little later.<\/p>\n Although most of the improved performance will be due to extra grip of the tyres on the track, there will also be a small magnetic factor. By removing some rubber from the tyre (about half a millimetre), the traction magnet is now fractionally nearer the metal rails, increasing the magnetic downforce \u2013 enough to push up the Mustang\u2019s reading on my magnet scales by nearly 3 grams.<\/p>\n A lot of slot car racers rub oil, WD40 or other more esoteric fluids (NSR tyre oil at Jadlams<\/a>) into the rear tyres of their cars to soften them and give more grip. It\u2019s something I \u2018discovered\u2019 as a teenager when tyres we\u2019d used in rally-cross races \u2013 we added a little oil to them to make them slippy \u2013 suddenly became ultra-grippy when the oil soaked in. It turned out we weren\u2019t the first people to do this\u2026 and the 3-in-1 oil we used was the most popular treatment \u2013 as it is today.<\/p>\n The theory is that the oil degrades the rubber and opens up the structure a little, making it softer. We only want to do this to the surface of the tyre that sits on the track \u2013 the surface we\u2019ve trued \u2013 as we don\u2019t want the tyre to swell up and distort. If that happens, the tyre may not fit tightly on the wheel and the surface will no longer be flat and true. The tyre would then need to be glued on the wheel (a palaver I don’t think is ever necessary on a standard Scalextric car) and then re-trued.<\/p>\n With the body removed from the Mustang, I rubbed a couple of drops of my favourite sewing machine oil onto my thumb and forefinger and then rubbed this onto one of the tyres \u2013 just coating the surface I\u2019d trued. I topped up the oil on my thumb and forefinger with another drop and rubbed it in to the other tyre.<\/p>\n A thin layer of oil soaks in pretty quickly. After just ten minutes, the surface felt softer and very slightly sticky. I left the tyres overnight before returning the Mustang to the track \u2013 I managed 25 laps and a fast time of 4.38 seconds. The feel of the car wasn\u2019t as good \u2013 the grip was there, but the sliding had been replaced by a sudden \u2018letting go\u2019 when traction was lost. The Mustang felt \u2018tippy\u2019 again and I had it on its roof a few times! Another downside was that the stickier tyres picked up more dust and debris from the track, so the initial grip started to disappear before the end of two minutes.<\/p>\n This reminds us that a tweak doesn\u2019t always produce a better-handling car. And it’s not possible to revert to the harder tyres – there’s no going back to ‘standard spec’ anymore. It’s time for the next piece in the jigsaw…<\/p>\n Adding weight – or ballast – to a Scalextric car is an important tuning technique when traction magnets are removed. However, it can also be used in a standard car to help with oversteer and understeer. My aim was to do two things: help with rear grip and move the centre of gravity down towards the track a little. I hoped this might give the Mustang more stability.<\/p>\n There are lots of materials used to add weight – and plenty of different opinions of how much to add. When I am tuning a car, I like the flexibility of being able to add and remove very small amounts \u2013 so the big 5g and 10g wheels weights or lead sheet aren\u2019t my choice. Instead, I use either tungsten putty (Slot.it putty at Jadlams<\/a>) or good-old Blu-Tack. Unlike some racers, I don\u2019t like my cars to pile on the pounds \u2013 an extra gram here or there is enough, an extra 10 or 20g and the car becomes a tank!<\/p>\n I measured two 1g pieces of Blu-Tack and simply pressed these into the underpan, just in front of each rear wheel, either side of the motor. I made sure the Blu-Tack didn\u2019t impede any body-roll or interfere with the tyres, axle or gears.<\/p>\n On track, the Mustang’s handling was transformed \u2013 back to how I like it, but with more grip. In the initial ‘shakedown’, I managed a stunning 4.18 second lap. In a proper two-minute test run, I wasn\u2019t able to replicate that fast time, but I managed a record 26 laps and a fast lap of 4.32 seconds. My aim in these test sessions is always to set as fast a pace as possible for two minutes without crashing, rather than an all-or-nothing search for a top time. In that respect, the 26 laps is as important a measure of handling and performance as the 4.32 second best lap.<\/p>\n The beauty of the Blu-Tack is that it\u2019s easy to fine-tune \u2013 remove the body, whip out the Blu-Tack, re-weigh and replace. I tested with 0.25g, 0.5g, 0.75g and 1.30g on each side \u2013 but the original 1g (or 0.97g to be precise) remained the sweet-spot. The car felt superb, the rear was more predictable when traction was lost \u2013 sliding rather than breaking loose or tipping. In fact, the only offs were when the front of the car de-slotted in fast corners… I have created understeer!<\/p>\n In the next blog we will shift our attention to understeer<\/strong> and tweaking the front of the car \u2013 including truing the front wheels and tyres, reducing front grip, adding weight and tightening up the guide. This is the half way point of my Scalextric Tuning series and I hope you’re finding the blog posts interesting and useful. Don’t forget you can find all ten posts here: https:\/\/blog.jadlamracingmodels.com\/tag\/scalextric-tuning\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Oversteer is when the rear of the car tends to spin out in a corner… It\u2019s what Americans describe as the car being \u2018loose\u2019 – the rear-end steps out if you\u2019re going too fast. The opposite is understeer, when the car tends to go straight on in a corner \u2013 the car is described stateside […]<\/p>\n","protected":false},"author":4,"featured_media":3646,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3,5,13,6],"tags":[38,29,44,39,30],"_links":{"self":[{"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/posts\/3644"}],"collection":[{"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/comments?post=3644"}],"version-history":[{"count":36,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/posts\/3644\/revisions"}],"predecessor-version":[{"id":5619,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/posts\/3644\/revisions\/5619"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/media\/3646"}],"wp:attachment":[{"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/media?parent=3644"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/categories?post=3644"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.jadlamracingmodels.com\/wp-json\/wp\/v2\/tags?post=3644"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/blog.jadlamracingmodels.com\/wp-content\/uploads\/2020\/12\/Oversteer1.2.jpg\")
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<\/a>\n\t\t\t<\/div><\/figure>\n\t\t<\/div>\n\nTyre Softening Treatment<\/h4>\n
![\"\"](\"https:\/\/blog.jadlamracingmodels.com\/wp-content\/uploads\/2020\/12\/Oversteer5.1.jpg\")
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<\/a>\n\t\t\t<\/div><\/figure>\n\t\t<\/div>\n\nAdding Weight<\/h4>\n
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