Post by nickd on Mar 8, 2016 11:05:33 GMT
Lets start with wheels.
If you don't understand what offset is, use Google. However, what size wheels fit an MX-5?
Tyre width and "Lows" make a difference. Assuming you are going to fit proper size tyres then for a MK1, from the hub face of the car, the bit the wheel actually bolts to, the original 14" MK1 wheel's outer face was about 35mm further out. So if you want wider wheels, you need to work out your width and offset.
So if you have a 15 x 7J wheel with a 30 offset, will it fit?
Width in inches so 7" x 25.4 to give the wheel width (they are wider than this, but this is good enough) 177.8 (you can round it up to 178.
Divide that by 2 to give you half the width and then take away the offset 178/2 - 30 = 59mm.
So here are the important figures.
For MK1 cars, if that final figure is below 66, for normal tyres and suspension you will require no body mods to fit the wheels.
For MK2 cars the figure is 78
If you go above these figures you are likely to need to roll your arches. Spastic camber is not a solution and it will cost you more in tyres that the cost of rolling.
If you fit big tyres the situation will be different, so 225 50 15 tyres would require the arches rolling and pulling if you are at the 78 figure for instance.
Tyre sizes.
Just because you can buy a wide wheel, do not assume there will be tyres to fit them. Different world markets have different tyres and specifications and regulations that apply to them. Just because you can get a tyre in the US, it does not mean it is available in Europe or even legal for use. Equally just because "it's been proved in America or Japan" does not mean results are equal in Europe and generally far from it. You will see very few cars in Europe running Hoosier tyres for this very reason.
Also, just because a tyre size exists in one brand and pattern, it does not mean that other manufactures make that same size. If you buy 10" wide 13" rims, the chances of getting a road tyre to fit are slim. Think before you buy!
Tyre technology. Firstly Tyre sidewalls are soft, any talk of soft sidewalls dulling the performance of your tyre puts you pretty squarely in the stupid category. Let the air out of your tyres and see how strong the sidewalls are. Some of the best tyres have the softest sidewalls. Tyre response and performance is down to many things, shoulder stiffness and tread design are influential in this.
Tyres grip the road in two ways, chemical grip, the physical stick to the road and mechanical grip, the way the rubber deforms around the features of the road. Chemical grip is like sealotape, a physical glue to the road. Many things influence this, but one thing that is guaranteed to reduce it is to put a barrier between the rubber and the road surface. This is commonly known as rain! On wet surfaces chemical grip is vastly reduced and mechanical grip becomes more important.
All tyres are not the same. While price is not a necessarily an indication for performance in the vast majority the Chinese budget brands, designed to be cheap and long lasting have poor wet grip. Most tyres that you have never heard of will fall into this category. However, even the very best tyres will have reduced wet grip over dry and anyone who says they cant get a tyre to slide in the wet is simply not trying hard enough.
If you don't understand what offset is, use Google. However, what size wheels fit an MX-5?
Tyre width and "Lows" make a difference. Assuming you are going to fit proper size tyres then for a MK1, from the hub face of the car, the bit the wheel actually bolts to, the original 14" MK1 wheel's outer face was about 35mm further out. So if you want wider wheels, you need to work out your width and offset.
So if you have a 15 x 7J wheel with a 30 offset, will it fit?
Width in inches so 7" x 25.4 to give the wheel width (they are wider than this, but this is good enough) 177.8 (you can round it up to 178.
Divide that by 2 to give you half the width and then take away the offset 178/2 - 30 = 59mm.
So here are the important figures.
For MK1 cars, if that final figure is below 66, for normal tyres and suspension you will require no body mods to fit the wheels.
For MK2 cars the figure is 78
If you go above these figures you are likely to need to roll your arches. Spastic camber is not a solution and it will cost you more in tyres that the cost of rolling.
If you fit big tyres the situation will be different, so 225 50 15 tyres would require the arches rolling and pulling if you are at the 78 figure for instance.
Tyre sizes.
Just because you can buy a wide wheel, do not assume there will be tyres to fit them. Different world markets have different tyres and specifications and regulations that apply to them. Just because you can get a tyre in the US, it does not mean it is available in Europe or even legal for use. Equally just because "it's been proved in America or Japan" does not mean results are equal in Europe and generally far from it. You will see very few cars in Europe running Hoosier tyres for this very reason.
Also, just because a tyre size exists in one brand and pattern, it does not mean that other manufactures make that same size. If you buy 10" wide 13" rims, the chances of getting a road tyre to fit are slim. Think before you buy!
Tyre technology. Firstly Tyre sidewalls are soft, any talk of soft sidewalls dulling the performance of your tyre puts you pretty squarely in the stupid category. Let the air out of your tyres and see how strong the sidewalls are. Some of the best tyres have the softest sidewalls. Tyre response and performance is down to many things, shoulder stiffness and tread design are influential in this.
Tyres grip the road in two ways, chemical grip, the physical stick to the road and mechanical grip, the way the rubber deforms around the features of the road. Chemical grip is like sealotape, a physical glue to the road. Many things influence this, but one thing that is guaranteed to reduce it is to put a barrier between the rubber and the road surface. This is commonly known as rain! On wet surfaces chemical grip is vastly reduced and mechanical grip becomes more important.
All tyres are not the same. While price is not a necessarily an indication for performance in the vast majority the Chinese budget brands, designed to be cheap and long lasting have poor wet grip. Most tyres that you have never heard of will fall into this category. However, even the very best tyres will have reduced wet grip over dry and anyone who says they cant get a tyre to slide in the wet is simply not trying hard enough.
le sigh