DUNLOP RACING TYRES
The alchemy of performance tyres; the mixing desk where ingredients turn into world beating compound
to the particular mix, or recipe, of the rubber. ‘We have quite a range of
compounds and we can choose from this range for particular circuits and weather conditions,’ continues Meenan. ‘If it’s wet we have what we call a cut slick option, which is a soft slick tyre with ‘tractor-style’ cuts in the surface [angled cuts from around the middle of the tyre outwards]. For race tyres, these are all hand cut at the factory.’ The cut slicks are used in
situations where there is light rain, but not enough to go to intermediates. This is particularly useful for circuits like the Nürburgring where it can be very dry at the start of the lap and damp or even wet at the back of the circuit.
HAND-CUT GROOVES The grooves are only 3-4mm deep and are cut with a variety of blades in a hand-cutting tool that heats up to the temperature of a cool soldering iron. Dunlop looked at the possibility of automating this tread cutting process, but it’s not as quick as cutting by hand. The tread cutters are a little bit like sheep shearers – they are deft in what they do and can cut tread very quickly, setting their blades so they don’t go anywhere near the bandage (the fabric part
of tread produce the required volume of rubber and you work out the appropriate clearances at any position across the section to give you the pattern at a particular point. The hand-cut grooves give
The contact patch modelled in CATIA showing areas of high stress
of the carcass). If the process was automated, in situations where the bandage is closer to the surface an automated machine could cut into it. ‘Because this is part of the
– that wouldn’t be cost effective. ‘The tread pattern generally
comes from us and is based on feedback from tests. We would try a range of different patterns and converge on what we think
“The tread pattern is based on feedback from tests”
development process, having the tread cut by hand means we can change the pattern instantly without having to re-programme any machine tools or produce more tyres,’ says Meenan. ‘It can’t be moulded in because we’re changing the product so regularly
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is a good compromise for all conditions. A lot of theory goes into tread design and we have a number of our own programmes to help us choose the optimum tread pattern for particular conditions – things like a water clearance analysis for sections
you enough water clearance to make a slick tyre work in variable light rainy conditions, and on longer laps like Nürburgring where it could be dry for three quarters of the lap. ‘It’s very difficult to tweak a compound [swap tyres for better grip] in these conditions as it’s either going from dry to wet or wet to dry, so the best you can do is provide the possibility for water clearance when it’s encountered,’ explains Meenan. The Dunlop intermediate
gives about 30 per cent water clearance, the wet about 40 per cent and what they call the monsoon tyre gives about 50 per cent clearance. In comparison, the cut slick gives about 15-20 per cent water clearance, depending on the number of cuts made and their depth.
Dunlop does slick testing
at several locations and wet testing where it can. ‘At the end of this year, we went back to Sebring in Florida. We have lots of experience from Sebring, especially with BMW. We did a few 12-hour tests there before
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