I have always planed to use 13" wheels on my Berkeley project car. My previous car had 13" wheels with 175/50VR13 tyres made by Yokohama. I had always resisted going too wide on my three wheelers on the assumption that the low car weight would not give enough lbs/in squared over the contact patch. I once used a low profile 185 on the back and found that although excellent in the dry and excellent handling up to 150mph but was a bit disappointing in the wet aquaplaning at a lower speed than previous tyres. But that was 14 years ago and tyre compounds have improved since then.
I have now learnt that the contact patch will be the same no mater how wide the tyre, the thing that changes is the contact patch shape and the size is dependant on tyre pressure.
My dilemma is that the new car will be capable of speeds well in excess of 150mph and that would require a rating of "Z", and to my knowledge that rating is not available in 13".
I may be worrying unduly here as the difference in compound between VR and ZR is only slight and the speed rating is based on the ability to withstand higher temperatures and as temperatures are weight related my lighter than normal car may be ok.
Friday, September 12, 2008
Monday, September 8, 2008
Graph Text
I took a load of measurements at approximately every half inch. I have made a graph to show the way the rate raises. I started with a bit of tension because of the way I set the test up. The best part of the graph is between 14" and 18". I used two 22" bungees and stretched them to 44".so the diagram starts when the chords are stretched to 26". I am going to try bicycle inner tube tomorrow with and without air.
Wednesday, September 3, 2008
Suspension Musings
Before I can finalize my suspension design I will need to know my CofG height, and that means I will have to have my roof, floor, space frame and roll bar in the equation. The rubber that I intend to use is this stuff http://www.ci-band.com/ . It is very thin and so I can make it up in multiple layers. I want a rising rate and my gut feeling is that I can leave the rate rise to the properties of the rubber, provided that the geometry of the suspension does not give me a falling rate like angled coil over’s do. I will give a rough sketch to show you my ideas
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