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By now you should have a fully built car. What you need to do now is to set it up. First I’ll give a base set up for the L4 and then I’ll explain a few techniques useful on a race night.
L4 Setup
If you have followed the advice written previously most of these will already be done, but here are a complete list of settings for a baseline setup.
Front
Use IRS lowered front arms. These are needed when you want to run small fronts. You also need ride height spacers to put under the arms to adjust the front ride height for different size tyres.
Use CRC threaded axles on steering block. The titanium ones are best as less likely to bend. Makes it easier to change front tyres. Use the standard spacer washer on the axle to increase the track width. The nut then has to go on backwards so it still locks.
Start on 0.020 front springs. Change to 0.022 springs if you want more agressive steering on corner entry. These will give more mid corner understeer though.
Use the 5 degree camber blocks with one white teflon washer on either side of it.
1.5 degree camber, adjust this until the front tyres don’t cone.
Use GRP purple front tyres on a club night. These will almost certainly be the correct tyres at a national also, though if the car is understeering still with full additive, magenta or cyan can be tried. Larger tyres can be used on a club night, maybe 44-45mm. Due to the grip level, smaller is better at a national, around 42mm.
Front ride height should be 3.5-4mm.
There should be 0 degree toe in, front wheels absolutely straight ahead.
Some people put Associated black grease or similar on the kingpin for damping. This isn’t absolutely necessary though as a lot of people use no grease whatsoever.
Rear
If a CRC durashock is being used, use the olive spring and 20wt oil. If an Associated VCS shock is used, use the olive spring and 30wt oil.
The thin 0.063 T-bars should be used with the tweak screws just touching the chassis. There should be no centre screw/spacer at the rear.
Use Associated diff grease on the damper plate. Check this after every run and before the first run of the night (the one I forget!). Some people use 30wt shock oil instead.
Use the CRC rear pod sides as mentioned previously if you want to run smaller rear tyres. IRS ride height spacers will be necessary with these and will also give you 0.5mm adjustment steps.
Use GRP grey rears. Run them at about 48ish mm diameter for a club night and down to around 45mm when the grip is up at a national.
Make the ride height the same at the rear as at the front. This should also be the same at the rear of the main chassis plate, adjusted by moving the shock spring adjuster.
Pod droop should be a maximum of 1.5mm max. This is the change in ride height at the rear of the main chassis plate from when the chassis is flat to when the shock is fully extended.
The cell trays should be placed so the cells are in the forward position.
Note – Parma tyre compounds are the same as GRP so these could be directly substituted.
Keith Robertson, 2007-2008 19 Turn National Champion, has given me a list of the differences between the above and his own setup. These are especially useful as he uses a different make of tyre to myself (Jaco vs GRP). These are below.
Front
Axles – CEFX front axles are better (than CRC threaded ones) but are difficult to get – don’t need to put the nut on backwards.
Springs – I always start with 0.020 springs – keeps the car nice and consistent.
Tyres – Jaco Prisms straight out of the box – I use double pinks but I would recommend lilac.
Kingpin grease -All the ‘World level’ drivers don’t use any lube, but I find that Stealth Diff Lube gives the most consistent performance (smooths the car down making it less on edge).
Rear
Shock – Same except for Associated shock with 25wt oil and olive spring.
Damper plate – Associated Green Slime on damper plates (seems to last longer between applications).
Rear pod – IRS lowered rear pod – does the same job.
Rear tyres – Jaco Prism yellows – straight out of the box be it national or club (48mm).
Front Camber Adjustment
On a 12th scale car the front camber adjustment is not a tuning aid as such, but it is important to get right to stop the tyres from coning, or wearing more on one side than the other. The picture below shows what happens if you get it wrong. The tyre on the left is correct, but the one on the right has had the incorrect camber set.
A good starting point for the camber setting, as stated above, is 1.5 degrees of negative camber (negative being the top of the tyre pointing inwards).
Set a camber gauge to -1.5 degrees, put against the tyre (with everything on a totally flat surface) and then adjust the turnbuckle so that the edge of the tyre lines up exactly with the camber gauge.
Adjusting the turnbuckle can be seen below. Afterwards, make sure the upper suspension arm eyelet is still in line with the steering block, or the suspension can bind.
Ride Height Adjustment
Use a ride height gauge with the car fully equipped (cells installed) on a totally flat surface to measure the ride height of the car. Measure the front of the chassis as shown below. Use front ride height spacers as described earlier to change the ride height. Do not try to change the ride height using shims on the kingpin as this will change the suspension geometry.
Measure the ride height at the back of the chassis. This should be the same as the front and rear. Adjust this by moving the spring adjustment nut on the centre shock. Settle the car by pressing down on the rear ball joint of the shock before remeasuring. This can affect the front and rear measurements so always remeasure this after changing this.
Measure the rear ride height as shown below. The ride height is changed by changing rear ride height adjusters.
Gearing
A difficult one this, as it very much depends on the motor being used.
12th scale gearing is not measured by straight gear ratio as it is very dependent on rear tyre size. Instead, it is measured by something called roll-out, which is the distance a car travels for one revolution of the motor. For a full description and charts to help look here.
The best thing to do is to look at the technical charts for the nationals (reports and charts are on this web site) to see what other people are using for similar motors and start from there.
This doesn’t always apply to other cars, but on the L4 most people use an 88 tooth spur gear when running a 19 turn motor as there is not enough motor movement to mesh the gears properly at the required roll-out when using a larger spur.
Tweak Adjustment
This is absolutely critical to get right, otherwise your car will not go in a straight line. Luckily, it is quite simple to do. If you are an expert it is possible to do this by eye (Andy Griffiths has done this on my car in a matter of seconds and it was spot on!) but for us mortals I’ll describe the coin test, which is a good method to use.
First set the tweak screws (as seen below) approximately so they just touch the chassis. They should not be clamped down onto the chassis as I have seen on some cars.
Then, put the car on an absolutely flat surface, and press down on the top ball joint of the shock to settle the car (and let go again). Put a coin on the top of each front wheel, and then lift the front end putting a small screwdriver or similar (small and circular so it can’t affect the measurement itself) under the exact centre of the front of the chassis. Very slowly lever this up until the front wheels lift off the ground.
The aim is for both front wheels to lift at the same time, shown by both coins dropping off the wheels simultaneously. If the tweak is incorrect, as it almost certainly will be at this point, one front wheel will lift before the other, and that coin will drop off the front wheel first as seen below. If this happens, turn the tweak screw on the side of the car the coin dropped off first in 1/8th of a turn, turn the other one out 1/8th of a turn, settle the car and retest with the coins.
Keep doing this until both coins drop off the wheels at the same time as (sort of) shown below. The car will now be balanced left to right and should go in a straight line.
Additive
I hardly know of two people who do this exactly the same, but there is a general technique to be followed and I will show my own interpretation of it.
There are two common additives in use at the moment, CS High Grip as shown below, and Speedtech. Both are very similar so take your pick.
I use a brush as can be seen below to coat the tyres with the additive. With the rear tyres put on the additive around 20 minutes before the race, brushing an even coat over the full width of both tyres.
Around 10 minutes before the start of the race put the additive on the front tyres. The amount of additive on the front tyres is a major tuning aid. Start with coating the inside half of the front tyre as can be seen in the photo below. Spinning the front tyre while holding the brush against it gives a nice clean line.
On a high grip track you will probably end up coating the entire front tyre with additive when running with purple fronts, or close to it.
Around 5 minutes before the start of the race, wipe the tyres to remove as much additive as possible. I use an old towel to do this.
Then, just before running rub the tyres on the carpet by moving the car in a circular motion to remove as much remaining additive as possible. This will give you grip from the start of the race.
Hopefully this should be everything you need to know when moving from another class into 12th scale with an L4 or similar car and should get you started. Remember that 12th scale drivers are well known to be the most helpful of any class, so if you are stuck just ask.
All you need to do now if you haven’t already is to get yourself a car and start racing in one of the most rewarding, and at the same time fastest classes of car to drive in RC.
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