loggyboy
15-01-09, 09:56 AM
As with all cars, when upping the size of wheels, the 3 things to note are diameter, width and offset. (ignoring PCD and centrebore sizes that must suit your car.). With the nova 90% of the time it’s the width/offset combo that can cause problems.
Vauxhall chose the (quite high) 49mm offset to their FWD cars. It was said to aid control of the car in a blow out situation (The closer the wheel is to the centreline of the turning arc, the less likely it is to pull to either side). This was quite high when compared to other manufacturers, so back in the 80s/90s when it came to aftermarket alloys, Alloy wheel manufacturers tended to produce moulds/dies that cater for the majority of cars, meaning 1 or 2 wheel moulds could be machined and drilled to suit almost all car manufacturers wheel sizes, however the 49mm offset was harder to achieve as it tended to leave very little room for calliper clearances on most wheel spoke designs and also there was very little material left on the mounting face of the alloy to machine off and leave enough metal to be still be strong (Just think that more than ΒΌ of your cars weight is supported by a few thin metal spokes!). Some wheel manufacturers did produce wheels that specifically catered for the high offsets, This is more so recently as other Car manufacturers (inc Ford & Renault) were increasing the offsets they used too. Compomotive and Speedline were two such wheel manufacturers that did so, hence the popularity of their wheels on a lot of Vauxhalls.
Sadly as the Nova is quite a small car there is little room to work with when wanting to up the size of wheels/tyres. There’s no 100% fixed way to work out the Maximum size of wheels you can fit and/or low you can go without causing arch issues - every car is slightly different. Not only are there manufacturing tolerance (such as beam position, arch /panel lines etc) but the condition of the beam bushes can cause rubbing.
General principles.
Below is the simple cross section of a wheel showing where the key variables are, including Diameter, width (J) and Offset (ET).
http://www.loggyboy.com/images/WheelDiagram.gif
The diagrams below show the relationship between the body and suspension components.
Here were see how changing the offset and width can alter the position of the wheel in relation to the cars components.
http://www.loggyboy.com/images/WheelOffsetsExample.gif
Standard Nova wheels.
The largest wheels fitted to Novas from the factory were 14", these were 5" wide and had an offset of 47.5 or 49mm. The narrow width gave plenty of room on between front (arches) and rear (inner arches/suspension).
15 inch alloys
In general most 15" diameter alloys will be available with 6" width, meaning 49mm offset is ideal (If available). With 195 45 15 tyres there should be minimal rubbing with unmodified rear arches even when using lowered suspension. Any rubbing would be solved by lightly trimming/rolling the back edge of the rear arches.
195 50 15 tyres on the same wheels are more likely to rub slightly so may require the rear arches to be trimmed more.
16 inch alloys
16" alloys will generally be available in 6.5 or 7 inch width
Some exceptions being Compomotives and Speedline Allesios, as these were/are available in 16"x6" and 49mm offset. Hence the reason why these are so popular on Novas/Corsas.
The above fitted with 195 40 16 tyres should require no or minimal arch mods. 195 45 16s may rub slightly more but can fit.
If fitting 6.5 inch wide rims you will likely need 45mm offset and well trimmed/rolled arches. You would also expect rubbing under heavy load.
17 inch alloys
These are rarely available in less than 6.5/7" wide so as such will need arch mods and 45mm offset and as low profile tyres as are available. Expect rubbing even with arch mods. Also expect a harsh ride and naff handling!
Vauxhall chose the (quite high) 49mm offset to their FWD cars. It was said to aid control of the car in a blow out situation (The closer the wheel is to the centreline of the turning arc, the less likely it is to pull to either side). This was quite high when compared to other manufacturers, so back in the 80s/90s when it came to aftermarket alloys, Alloy wheel manufacturers tended to produce moulds/dies that cater for the majority of cars, meaning 1 or 2 wheel moulds could be machined and drilled to suit almost all car manufacturers wheel sizes, however the 49mm offset was harder to achieve as it tended to leave very little room for calliper clearances on most wheel spoke designs and also there was very little material left on the mounting face of the alloy to machine off and leave enough metal to be still be strong (Just think that more than ΒΌ of your cars weight is supported by a few thin metal spokes!). Some wheel manufacturers did produce wheels that specifically catered for the high offsets, This is more so recently as other Car manufacturers (inc Ford & Renault) were increasing the offsets they used too. Compomotive and Speedline were two such wheel manufacturers that did so, hence the popularity of their wheels on a lot of Vauxhalls.
Sadly as the Nova is quite a small car there is little room to work with when wanting to up the size of wheels/tyres. There’s no 100% fixed way to work out the Maximum size of wheels you can fit and/or low you can go without causing arch issues - every car is slightly different. Not only are there manufacturing tolerance (such as beam position, arch /panel lines etc) but the condition of the beam bushes can cause rubbing.
General principles.
Below is the simple cross section of a wheel showing where the key variables are, including Diameter, width (J) and Offset (ET).
http://www.loggyboy.com/images/WheelDiagram.gif
The diagrams below show the relationship between the body and suspension components.
Here were see how changing the offset and width can alter the position of the wheel in relation to the cars components.
http://www.loggyboy.com/images/WheelOffsetsExample.gif
Standard Nova wheels.
The largest wheels fitted to Novas from the factory were 14", these were 5" wide and had an offset of 47.5 or 49mm. The narrow width gave plenty of room on between front (arches) and rear (inner arches/suspension).
15 inch alloys
In general most 15" diameter alloys will be available with 6" width, meaning 49mm offset is ideal (If available). With 195 45 15 tyres there should be minimal rubbing with unmodified rear arches even when using lowered suspension. Any rubbing would be solved by lightly trimming/rolling the back edge of the rear arches.
195 50 15 tyres on the same wheels are more likely to rub slightly so may require the rear arches to be trimmed more.
16 inch alloys
16" alloys will generally be available in 6.5 or 7 inch width
Some exceptions being Compomotives and Speedline Allesios, as these were/are available in 16"x6" and 49mm offset. Hence the reason why these are so popular on Novas/Corsas.
The above fitted with 195 40 16 tyres should require no or minimal arch mods. 195 45 16s may rub slightly more but can fit.
If fitting 6.5 inch wide rims you will likely need 45mm offset and well trimmed/rolled arches. You would also expect rubbing under heavy load.
17 inch alloys
These are rarely available in less than 6.5/7" wide so as such will need arch mods and 45mm offset and as low profile tyres as are available. Expect rubbing even with arch mods. Also expect a harsh ride and naff handling!