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I have a GTD MkII with 15" rims which I currently run Yokohama tyres on. However, the profile is too low and I was wondering if I could put Dunlop Historic Racing tyres on instead. I understand they do not have the required markings on them for road use, but I also understand that as GT40's were built for the road, the tyres do not have "Race Only" on them either! Does anybody know if this is the case?
If you think I might get away with it, what size were the original GT40 tyres?
I appreciate any help you can give!
Kind regards
Simon Kelly [img]images/icons/confused.gif[/img]
Wide enough road legal 15 inch tires are almost impossible to find. Goodyear makes a treaded racing tire which has enough overall diameter but is not road legal. The Dunlops aren't road legal either, will fit but don't have as much overall diameter. Avon makes a tire that fits well and can be treaded but is not road legal either. If you search this forum under Dunlop you will find more info. In the US Roger Krauss tires is a good source.
My front tyres are the 4.75 1000 15 and the rears are 6 1200 15. The numbers can be interpreted as follows. First number is height of side wall in inches. Next number is maximum width of tyre (not tread or rim) in inches with two zeros tacked on. The last is the rim size. The front tyres whilst callled Dunlop Racing on the side wall do not have Not for Highway Purposes written on them butthese rears do. There is an alternative rear tyre sized up at 525 1050 15. This is free from the marking Not for Highway Purposes. The guys who run their cars on the road use this rear tyre ad not the 12 inch. I trailer my car to and from events anyway now as I carry too much clobber for driving there and back by road. Also it is a token gesture of a cost saving to not tax the car or pay road going insurance!
These tyres are good in some aspects but poor in others. Their sidewalls are soft amd tyre pressure is critical for handling balance and top prevemt too much roll on the sidewall. If you haev the 12 inch tyres clearances are quite tight to the bodywork and mechanics inside the wheel arch ie anti roll barmounts etc. Custom anti roll bars will reduce this issue ie go up and over the gear box not underneath as in std GTD set up.
In the wet the tyres are not that grippy. Ray Christopher follwoed me around Donnington once on Pirelli Pzeros in very wet conditions. He didn't overtake as he wanted to see my impending off. I disappointed him but only just!
However in the dry they are very grippy. The compound is a pure rubber compound and is quite stable when up to temperature. Again just set your tyre pressures correctly.
Down side to the compound is that the tyre will harden after a set number of heat cycles. Look at cars in museums and see theirr polished tyres. They are not polished but perished. You will need to change the tyres possibly once a year, you may get two season out of them depending on useage.
Suppliers can be found on the internet. Basically there are two suppliers. One is HP Tyre Exchange at Silverstone ask for John Pearson. Knowledgeable chap. However I think that the Beaulieu dealership may be a fraction cheaper now but I haven't dealt with them yet.
I beleive that all these tyres mentioned above were/are used on original cars. They are FIA historic racing approved.
If you go to GTD club website you may find some pictures of my car with these tyres on. They look the business.
Hope this helps
Malcolm
PS but for competition purposes I am considering going to Hoosiers next as the side walls are stiffer. However these are pure racing tyres and no chance of road use.
Short answer is no, they won't. Whilst they are the right size and say DOT approved, in fact they only have 1mm of tread on a compound soft enough to lose this tread after one lap. Itis a race tyre in disguise accoding to Hoosier! Bummer really as it sounded really good when I first saw it!
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