I have a 98 Ram with the 16' inch wheels. I hate them. I would like to put on some of the newer Ram 20's or the SRT-10 20's. I have been researching and the majority of sites I find say they will fit 98-05 Rams, but I have also talked to people who have done it and they say it that I have to knock out the center caps and replace my studs. I've also been told that the early 98's are the ones that are difficult to install the 20's on, but on the later 98's they will go right on. My truck was made in June. Does anyone know what month in 98 Dodge made the change? And if I get the 20's do I need to go from 3:55's to 3:92's? I've asked about this before and I could never get a real answer. Would someone please set me straight?

 

not sure on any of your specific questions, but here is some general info.

-only the overall diameter of the tire/rim combo (how tall it is) effects spedometer

-if the combo weights alot more then your current then you may feel a little less power, if they are taller and weigh more, most do, depending on how muchtaller and the weightyou may feel a noticable power loss, but i think the combo your talking about should be fine, changing gearing is needed only when going to a much larger then stock

-the speedometer will read higher speed with a bigger tire, a 3" overall larger tire diam will effect your speed by about 5 MPH

-on wheel fitment, be carefull on lugnut hole size and the taper of the nut, they have to match, the new ones may have larger studs with different threads and may be hubcentric type of mounting

-the hub hole in the middle may be an issue on the new wheels to older hub

-a test fit on wheels you want to swap is always best

-be very carefull to make sure they seat correctly and always check lug torque often after you swap

 

Some very good points raised by overs ram, but the speedometer actually reads *lower* when the tire gets taller. At a given road speed, the larger wheels are not turning as fast as they used to. Since the speedometer works by counting wheel rotations over time, it does not "realize" how fast you are actually going.

The percentage change depends on the percentage change in overall diameter. So the acutal mph inaccuracy will vary at different speeds. For an easy example: If you have 2% error, your speedometer will 2mph off at 100mph (2% of 100) but only 1mph off at 50mph (2% of 50mph). At 0mph, you'll have no inaccuracy, it'll always read zero.

Calculator programs like this one: http://www.miata.net/garage/tirecalc.html can streamline all the calculations you would do.

 

Ben, You are CORRECT
Thanks.

Sorry I got that reversed.

*Also be aware if you have a hubcentric type application

*on the lug nut hole size, they do not have to match, but must be close, if one truck had metric studs and one S.A.E lugs both are close to the same outside diameter and will work (my case with the H2 rims, the H2 was a slightly different thread then the 3/4 ton dodge but worked fine)