Need Advice: What to check when buying used rims?
07-22-2002, 11:54 PM
#1
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Need Advice: What to check when buying used rims?
I am going to purchase a set of 18 X 8 and 18 X 9 Volk GT-N's for a good price from a local S2000 owner. I have read something about a hubcentric rings? Should these rims have them? And what do they look like? Also how can I tell if the rims are bent? I don't know much anything about rims. Any help is appreciated.
07-26-2002, 03:32 AM
#2
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Rims are located on the hub in two ways.
1) The desireable way is by carefully matching the center bore of the rim onto a flange on the hub. This is how the OEM wheels stay concentric with the hub and is called "hub-centric". Since some aftermarket rim manufacturers want to save money and not have to machine the center bore of each rim to match the variety of hub flange diameters out there, they machine the rim center bore oversize and use centering rings to make up to difference. This allows the rim to be located properly on the hub flange, but is not as precise as rims specifically machined for the S2000 hub. Plus, I've seen the centering rims stick on the hub instead of staying on the rim. This can cause a big problem if you don't notice it and try to mount another rim on that hub. Some people don't bother with the centering rings, making the rim lug-centric by default.
2) The undesireable way is called "lug-centric". In this case, the rim does not snugly fit on the hub flange (if there is a hub flange at all) and is located on the hub by the lug nuts (or bolts). This does not mount the wheel as concentrically with the hub as hub-centric designs.
Rims should be round (axial runout) and true (radial runout). A round rim spins concentrically on the hub and a true rim does not wobble side to side when spinning. To determine this, mount the rim on a tire machine and measure the axial and radial runout with a dial indicator guage. OEM specifdications call for no more than 0.7 mm (0.03") for both on new rims with service limit of 1.5 mm (0.06") radial and 2.0 mm (0.08") axial.
The easiest way to tell if a rim is bent (most of us don't have a tire machine and dial indicator handy
) is to put the car on jackstands with the wheels removed on one side. Mount the rim to the appropriate axle and spin it. Observe the rim carefully to see if it is round and true. It may help to place a rigidly mounted probe near the rim to see if it's wobbling - don't forget to look at the inside and outside of each rim. Bends and dings should be obvious using this method.
Good luck!
1) The desireable way is by carefully matching the center bore of the rim onto a flange on the hub. This is how the OEM wheels stay concentric with the hub and is called "hub-centric". Since some aftermarket rim manufacturers want to save money and not have to machine the center bore of each rim to match the variety of hub flange diameters out there, they machine the rim center bore oversize and use centering rings to make up to difference. This allows the rim to be located properly on the hub flange, but is not as precise as rims specifically machined for the S2000 hub. Plus, I've seen the centering rims stick on the hub instead of staying on the rim. This can cause a big problem if you don't notice it and try to mount another rim on that hub. Some people don't bother with the centering rings, making the rim lug-centric by default.
2) The undesireable way is called "lug-centric". In this case, the rim does not snugly fit on the hub flange (if there is a hub flange at all) and is located on the hub by the lug nuts (or bolts). This does not mount the wheel as concentrically with the hub as hub-centric designs.
Rims should be round (axial runout) and true (radial runout). A round rim spins concentrically on the hub and a true rim does not wobble side to side when spinning. To determine this, mount the rim on a tire machine and measure the axial and radial runout with a dial indicator guage. OEM specifdications call for no more than 0.7 mm (0.03") for both on new rims with service limit of 1.5 mm (0.06") radial and 2.0 mm (0.08") axial.
The easiest way to tell if a rim is bent (most of us don't have a tire machine and dial indicator handy
) is to put the car on jackstands with the wheels removed on one side. Mount the rim to the appropriate axle and spin it. Observe the rim carefully to see if it is round and true. It may help to place a rigidly mounted probe near the rim to see if it's wobbling - don't forget to look at the inside and outside of each rim. Bends and dings should be obvious using this method.Good luck!
07-26-2002, 05:35 AM
#3
Former Sponsor
Joshua you are again correct. Do you need a job? That was a very good answer.
Simon, If they will let you it would be a good idea to take the wheels to a tire shop and let them spin them on a balance machine. The Hunter GPS9700 is the best. This will show any problems in the wheel and or tires.
Jim
Simon, If they will let you it would be a good idea to take the wheels to a tire shop and let them spin them on a balance machine. The Hunter GPS9700 is the best. This will show any problems in the wheel and or tires.
Jim
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