Formula TKM: January, 2010 Formula TKM News

Written By: Grahame Butterworth

Well the good news is that the first batch of new era green label Maxxis tyres are produced and on a boat as I write, And there’s a small batch of them already in the country.

This first small batch has been flown over so that TKM traders and chassis manufacturers can have a proper chance to try out the new production tyres rather than the prototype tyres here a few weeks ago.

As you will see from the photo they have a much squarer shape then the old tyres, especially at the front where there is a significant increase in the contact patch on the track.

Add to that a new ‘green’ formulation and a new type of construction and you see that these really are new tyres rather than just a change of manufacturing materials.

One of the characteristics of the new tyres is that they seem to warm up to operating temperature quicker than the previous tyres, especially useful at this time of year. But having said that they also performed extremely well during testing on one of the hottest days of the year.

It is worth making careful note of the fact that they not only vary in surface width to the old tyres, but that they are also different diameters. Not a huge amount, but enough to make some difference.

Now the exact amount will vary slightly according to the rims you use them on but on fairly standard size 130mm front and 210mm rear the differences were as follows.

The front tyre is about 2cm larger in circumference which will mean the kart rides a shade higher but little to fuss about. At the rear the tyres have a circumference about 1.5cm smaller than the previous tyres and that is enough to make a gearing change.

So remember a smaller circumference is basically equivalent to putting on a larger rear sprocket. In this case effectively about one to 2 teeth less on the rear axle sprocket.

However because there is no doubt these tyres do give more grip, you may well find that you are coming out of corners quicker and can therefore afford to go two plus teeth smaller to gain maximum advantage.

The thing that is very important is to take into account the changes in set up you may need on your kart to gain the best performance from them. And of course something that will vary from kart to kart and driver to driver.

First thing to underline is that because these tyres have different construction you don’t need to run them at the fairly high pressures often used on the old green tyres, especially in cold conditions. It is suggested that 10 – 12psi is a good starting point and then you need to keep an eye on them to see how they are getting on.

Because they offer a significantly wider contact patch at the front it may well be an advantage to re-look at your front settings. For example previously some karts needed a few degrees of toe out to make them handle. I’ve known others that need some toe in. Both of those settings may now be closer to parallel because the tyres offer more grip.

So the real key point here is to really learn about the new tyres and how to get the best from them. Try different settings and take a close look at both lap times, driver feed-back and the look of the tyres to see which is the way to go.

How much faster are the new tyres? Well that is a subject creating a whole sea of mythical figures. Claims of two and three seconds a lap are just ridiculous unless they were previously using concrete tyres! Half to one second is about the mark, but again this will depend on track and chassis set ups etc.

The new tyres will be on sale at £105.63 a set plus VAT and will be available from late December or very early January depending on shipping delays and the Christmas shutdown.

Now while we are talking about handling let’s also just underline a change in kart set up which some folk have not fully comprehended and that surrounds the change in side bar fittings.

Now in the good old days (pre crash tested plastic & bars) when the side bar was fitted at right angles at the back and then angled about 60 degrees to the front, the tightness of that bar in its mountings could make a very substantial difference to handling because it acted as a stiffener for the length of the chassis.

Now with the new type CIK crash tested bars the situation is totally different. The right angle fitting of both bars fairly close to the middle of the chassis means it no longer has any real effect on handling.

So whereas in the old days you softened the side bars to help the rear wheel lift as it goes round a corner, these days the side bars are no longer a significant adjustable handling item.

What you do tend to need now is a kart which is very stiff across the front so that when steering lock is applied it lifts an inside rear wheel – vitally important in the wet when there is less momentum and g-force to lift a wheel.

Remember karts have no rear axle differential so to go round a corner easily they need to have the inside rear wheel, if not fully off the ground, certainly only just brushing the ground. If that wheel doesn’t lift then you have monster understeer and engine bogging (especially in dry conditions) out of the corner with the kart running wide.

So if you have one of the older karts with traditional crash bars – still legal in Formula TKM so long as used with CIK bodywork – you actually have an advantage over the latest karts with their CIK sidebars. Something to bear in mind, especially if you trade up to a newer style chassis.

Finally a big thumbs up to the uprated TAG engine. It scored heat wins and fastest laps and helped two drivers on their way to GP plates. Not surprisingly sales of TAG engines have started soaring. Don’t miss your opportunity to buy one before the queue for engines gets too long.

Sidney Sprocket