New wheels for 2008 2500HD
October 27th, 2008, 12:12 AM
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New wheels for 2008 2500HD
I went to the dealership the other day to get a few accessories for my new truck and asked about possibly getting some 18"-20" chrome wheels. The sales guy I was speakingwith said that I would haveto stick with the same size wheels that it came from the factory with because changeing wheel sizes would mess with the Allison tranny. He said that I could go with bigger tires without any problems and just recalibrate the speedometer. This didn't really make any sense to me because one would think that the wheel diameter is irrelevant if you can make adjustments for the tire diameter. Is this true?
October 27th, 2008, 5:35 AM
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RE: New wheels for 2008 2500HD
Let us sort out the terminology here. A wheel consists of mainly two parts, the rim and the tire. The diameter of the correctly inflated wheel is approximately the same as for the tire.
Saying that you can change the tire but not the wheel sounds very odd. Changing the tire on the existing rim without changing the diameter of the wheel is possible within limits. This would not effect the ratio and therefor should not be a problem with your tranny, Allison or otherwise.
Changing wheel to a bigger rim, say from 16" to 18" is normally not a problem. There will be tires on the market to fit the 18" rim that will have the same diameters as the tire on your 16" rim. In most cases 20" will work the same.
What you need to know and take into consideration is the amount of air your vehicle is designed to have between the road and the rim. This air is a calculated part of the suspension. If you are willing to accept the changes in suspension performance, fine.
As for the tranny. Yes if you stray from the original wheel diameter the automatic transmission will perceive this as a change in load. Consequently it will shift differently. Or more correctly, it will shift the same in accordance to its settings. But as you have changed the settings on ratio this will affect what gear you will be driving in close to the shiftingpoints It will also affect your mpg. Unless you go with tires of diamters way off the charts this should not be a problem with the durability of the tranny.
Saying that you can change the tire but not the wheel sounds very odd. Changing the tire on the existing rim without changing the diameter of the wheel is possible within limits. This would not effect the ratio and therefor should not be a problem with your tranny, Allison or otherwise.
Changing wheel to a bigger rim, say from 16" to 18" is normally not a problem. There will be tires on the market to fit the 18" rim that will have the same diameters as the tire on your 16" rim. In most cases 20" will work the same.
What you need to know and take into consideration is the amount of air your vehicle is designed to have between the road and the rim. This air is a calculated part of the suspension. If you are willing to accept the changes in suspension performance, fine.
As for the tranny. Yes if you stray from the original wheel diameter the automatic transmission will perceive this as a change in load. Consequently it will shift differently. Or more correctly, it will shift the same in accordance to its settings. But as you have changed the settings on ratio this will affect what gear you will be driving in close to the shiftingpoints It will also affect your mpg. Unless you go with tires of diamters way off the charts this should not be a problem with the durability of the tranny.
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