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What do you guys think about these aftermarket rims? I have thinking about upgrading but have been considering used rims from newer bikes, watching ebay etc. Recently I have been looking around the web and emailed 2 companies to see if they made rims to fit vintage bikes. Both EPM and Dymag responded stating rims are available that will bolt on and use existing hardware.
EPM has some nice rims shown here. I like these and they have some good sizes available.
Dymag refered me to the 3 spoke classic and 3 spoke cast wheels. Dymag supplies cush drive and sprocket so I chain conversion may be necessary. Dymags are here.
The following is from the Dymag site and is interesting reading about the effect of reducing the wheel weight versus body weight.
Reducing unsprung mass (Wheels, discs etc) has a far greater performance benefit than reducing sprung mass (bodywork etc). In racing, some designers use a factor of eight. For example, saving 1kg on a wheel weight gaives the same performance gain as saving 8kg of sprung weight. This is due to the following benefits :
Braking/Acceleration
The force required to start a wheel rolling (moment of inertia) increases with the mass of the wheel. The same is true of the force required to stop a wheel, and so reducing the wheels weight, improves acceleration and braking efficiency. Since less energy is required to start and stop the bike, fuel efficiency also improves, but is not often noticed sa the rider simply goes faster!.
Gyroscopic effect :
Reducing the wheel mass, also reduces the gyroscopic effect of the wheel. When a wheel is spinning, it is very difficult to make it change direction, but the lower the mass of the wheel, the easier it is to flick from side to side. Try holding a front wheel at arms length via a spindle, spin it and then simulate diving in and out of a corner. The effort required is considerable, but it becomes significantly easier as the wheel mass reduces. Consequently, this has a major effect on the handling of a motorcyle.
Radius of Gyration :
This is more a function of wheel design rather than pure weight reduction, but the two are inextricably linked. The mass of a wheel is deemed to act at a certain radius from the center of the wheel (radius of gyration). In order to improve the performance of the wheel, the designer will try to reduce this radius, so that it acts as close to the wheel center as possible.
To demostrate this, try swinging a weight on a pice of string around your head. The shorter the string, the easier it is to swing. Hence reducing the radius of gyration, improves the manoeuvrability of the motorcycle. This is achieved by lightening the rim as this is on the extreme radius, and designing the spoke system with minimal weight at the extreme, whilst maintaining the required strength and stiffness.
In order to achieve the ultimate wheel, material choice is also crucial. Magnesium has the highest strength to weight ratio of any metal, and is only surpassed by Carbon Fibre. Hence all modern high performance wheels tend to use these materials. Dymag carbon wheels have achieved the tough German TUV standard for road use. This is a testament to the correct use of materials and design, enabling Dymag to make a race weight product, which conforms to British, Japanese and German roads standards.
In summary, the two main features of a high performance wheel are weight and stiffness. Both are important as the wheel needs to be as light as possible for the above reasons, but it also needs to be stiff to give crisp handling. If the wheel flexes, the tyre contact patch also changes, which can result in less predictable handling. These two features need to be married to a good design, which follows established engineering principles, to produce the optimum product for any given application
Check my math but if reduction of 1kg of wheel weight compares to a reduction of 8kg of body weight and 1kg = 2.2 lbs then if you reduced your combined tire/rim weight by about 9kg or 19.8 lbs (which seems reasonable) that would be about 160lbs of body weight!!!
Before you get too exited though they cost upwards of $2200.00 for a set of the EPM?s
EPM has some nice rims shown here. I like these and they have some good sizes available.
Dymag refered me to the 3 spoke classic and 3 spoke cast wheels. Dymag supplies cush drive and sprocket so I chain conversion may be necessary. Dymags are here.
The following is from the Dymag site and is interesting reading about the effect of reducing the wheel weight versus body weight.
Reducing unsprung mass (Wheels, discs etc) has a far greater performance benefit than reducing sprung mass (bodywork etc). In racing, some designers use a factor of eight. For example, saving 1kg on a wheel weight gaives the same performance gain as saving 8kg of sprung weight. This is due to the following benefits :
Braking/Acceleration
The force required to start a wheel rolling (moment of inertia) increases with the mass of the wheel. The same is true of the force required to stop a wheel, and so reducing the wheels weight, improves acceleration and braking efficiency. Since less energy is required to start and stop the bike, fuel efficiency also improves, but is not often noticed sa the rider simply goes faster!.
Gyroscopic effect :
Reducing the wheel mass, also reduces the gyroscopic effect of the wheel. When a wheel is spinning, it is very difficult to make it change direction, but the lower the mass of the wheel, the easier it is to flick from side to side. Try holding a front wheel at arms length via a spindle, spin it and then simulate diving in and out of a corner. The effort required is considerable, but it becomes significantly easier as the wheel mass reduces. Consequently, this has a major effect on the handling of a motorcyle.
Radius of Gyration :
This is more a function of wheel design rather than pure weight reduction, but the two are inextricably linked. The mass of a wheel is deemed to act at a certain radius from the center of the wheel (radius of gyration). In order to improve the performance of the wheel, the designer will try to reduce this radius, so that it acts as close to the wheel center as possible.
To demostrate this, try swinging a weight on a pice of string around your head. The shorter the string, the easier it is to swing. Hence reducing the radius of gyration, improves the manoeuvrability of the motorcycle. This is achieved by lightening the rim as this is on the extreme radius, and designing the spoke system with minimal weight at the extreme, whilst maintaining the required strength and stiffness.
In order to achieve the ultimate wheel, material choice is also crucial. Magnesium has the highest strength to weight ratio of any metal, and is only surpassed by Carbon Fibre. Hence all modern high performance wheels tend to use these materials. Dymag carbon wheels have achieved the tough German TUV standard for road use. This is a testament to the correct use of materials and design, enabling Dymag to make a race weight product, which conforms to British, Japanese and German roads standards.
In summary, the two main features of a high performance wheel are weight and stiffness. Both are important as the wheel needs to be as light as possible for the above reasons, but it also needs to be stiff to give crisp handling. If the wheel flexes, the tyre contact patch also changes, which can result in less predictable handling. These two features need to be married to a good design, which follows established engineering principles, to produce the optimum product for any given application
Check my math but if reduction of 1kg of wheel weight compares to a reduction of 8kg of body weight and 1kg = 2.2 lbs then if you reduced your combined tire/rim weight by about 9kg or 19.8 lbs (which seems reasonable) that would be about 160lbs of body weight!!!
Before you get too exited though they cost upwards of $2200.00 for a set of the EPM?s
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