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Discussion Starter #1 (Edited)
**My portion of this thread is going to be limited to what I know which is primarily the 20" tire sizes (and thereby the third gen and fourth gen trucks). If someone with knowledge of the stock 17" fitments, older trucks, or even aftermarket fitments wants to add, please do so.

It seems like we get a lot of questions in the tire and wheel section about basic fitment issues and recommended tire sizes. A lot of the questions have been answered before and could be found with a search but as someone that has spent hours upon hours slogging through search results, it's always nice to have a go-to for at least the basic info. With that in mind, I started this thread. If it's needed and it helps, great. If not, at least I have a thread I can link to when I see these questions, lol.

I am no expert by any means. Most of my knowledge comes from those hours of searching and reading both here on our forum and other places on the web. With that in mind, if you see something that you think is incorrect or needs to be added, please let me know.

First, some quick facts:
* All third gen 20" rims are 9" wide
* Fourth gen 20" rims can be either 8" or 9" wide. To the best of my knowledge the chrome clads are 9" and the painted rims are 8".
* Here is a good site to visit if you don't know for certain how wide your rims are. Simply pick your model year and match the photo.
http://www.finishlinewheels.com/DODGE/RAM+%C0+TRUCK/
* I believe some early third gen 4x2 trucks came with 275/55/20 stock. However, most trucks, particularly more recent models come with 275/60/20 stock. 275/60/20 is a 33" tall, 10.8" wide tire.
* As stated above, stock is a 33" tire. All third and fourth gen trucks can run a 34" tall tire stock and a 35" tire with a proper level. This is height only...for info on width, see below.
* 17" diameter rims are the smallest that will clear the brakes on third and fourth gen trucks!

Sizing, fitment, and other info by model year:
* Early third gen (2002-2005) Ram owners are lucky in this regard. These trucks have torsion bar front suspensions that eliminate the clearance issues that newer trucks have. These trucks can run 305mm wide tires bone stock. As stated above, that means they can run 35x12.50x20 with only a level!!
* Newer third gens (2006-2008) and fourth gens (2009-present) are generally limited in width by the upper control arms. If you search, you will find differing comments regarding what fits and what doesn't. One owner will report that a size fits with minimal rubbing while another may report the same size runs with zero rubbing. While some of this may be due to differing tolerances on the trucks themselves, I would tend to guess it has more to do with variance between tire manufacturers and models. The general rule is that 285 is the widest that will fit on stock rims and without spacers.
* Exception for fourth gens with 8" wide stock rims: There is an exception to the above general rule for fourth gen trucks with the stock 8" wide rims. The narrower rim pulls the sidewall in more than the wider rim and allows fitment of a wider tire. Members with the 8" rims have confirmed no rubbing with 295/60/20 and 295/65/20. I personally have not seen confirmation of anything wider fitting but that doesn't necessarily mean it will not.

Fitment and other info by tire size:
All of these are compared to stock 275/60/20 (33x10.8x20). Please note that while comprehensive, this is not a list of every single tire size available for the 20" rims but simply some of the most popular.
* 275/55/20 (32x10.8x20) = Same width as stock, 1" shorter than stock, great selection, slightly cheaper or same price as stock.
* 275/65/20 (34x10.8x20) = Same width as stock, 1" taller than stock, large selection and not overly expensive compared to stock.
* 285/50/20 (31.2x11.2x20) = 0.4" wider than stock, 1.8" shorter than stock, great selection, slightly cheaper or same price as stock, used a lot on lowered trucks with stock rims.
* 285/55/20 (32.3x11.2x20) = 0.4" wider than stock, 0.7" shorter than stock, somewhat limited selection, fairly expensive.
* 285/60/20 (33.5x11.2x20) = 0.4" wider than stock, 0.5" taller than stock, very limited selection and expensive.
* 285/65/20 (34.6x11.2x20) = 0.4" wider than stock, 1.6" taller than stock, very limited selection and expensive.
* 295/60/20 (34x11.6x20) = 0.8" wider than stock, 1" taller than stock, limited to only the Nitto Terra Grappler all-terrain that I am aware of, expensive but a good blend of wider and taller.
* 295/65/20 (35x11.6x20) = 0.8" wider than stock, 2" taller than stock, limited to only the Nitto Trail Grappler mud-terrain that I am aware of, expensive.
* 305/50/20 (32x12.00x20) = 1.2" wider than stock, 1" shorter than stock, pretty good selection, priced comparable to stock size.
* 305/55/20 (33.2x12.00x20) = 1.2" wider than stock, basically same height as stock, great selection, somewhat expensive.

Spacers? What about spacers??
When I say spacers I am referring specifically to the 1/4" spacers that are required on most 2006-up trucks to clear some of these tires sizes. Some people use them and love them, some people wouldn't even consider running them, and some people simply don't know. So here's the facts. Lots of owners run cheap ($20-30) off the shelf universal spacers with absolutely zero issues. Many owners have shown that there is more than enough lug stud to run a 1/4 spacer with no increased danger of lug runoff. Checking lug torque periodically is certainly a good idea but that's the case even if you aren't running spacers. The only potential issue with universal spacers is that they do not fit the hub or lugs tightly and are therefore difficult to center on the hub. Some owners have experienced balance/vibration issues because of this. The solution is a set of hubcentric spacers from Motorsports Technologies. These spacers are basically the best you can buy. Hubcentricity guarantees that the hole in the spacers fits snugly around the hub thereby guaranteeing that they are centered. Seems like these spacers can be had for around $125/pair or maybe slightly less than twice that for a set of four. You can find them here...
http://www.motorsport-tech.com/

Alright, that's all I got. If I think if anything else to add I will and as I said, if anyone has any suggestions please throw them my way. Hope this helps someone.
 

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Rep points for this. Nicely collated info.
 

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thank you!!!! great post
 

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Excellent Post & great work! - you lucky 20" rim owners. This type of info. would be great for us 17" rim owners but so far I do not think anyone has gone to this effort yet. Reps for you!!
 

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Excellent Post & great work! - you lucky 20" rim owners. This type of info. would be great for us 17" rim owners but so far I do not think anyone has gone to this effort yet. Reps for you!!
really shouldn't matter that much between 17" and 20". The only difference is the width of the wheel. So that's all u need to get an eye one, whether you chosen tire can be mounted on whatever width your wheel is.

It's really about the overall tire diameter in the end. Not saying there aren't things to consider when having 17" wheels, but it should be most the same info
 

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Awesome post. But how do I know if I need spacers? Want 305/55 on stock 20's.

*edit* saw you said 285 was widest without spscers.

Also does 2wd or 4wd matter? Assume this post is 4wd.

And rep points!!
 

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Havent been back in a while.


Have had a 2012 RAM Express for a while now .... I personally want to dump these 20" wheels .... I have a street truck, I use it as a truck .. not a pimp mobile :) ...

Im searching all dodge truck forums for show one who wants to work out a reasonable trade .. or, Ill go to a junky and get the 17 clad and lets the 20's sit on craigslis and/or ebay until they sell.
 

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really shouldn't matter that much between 17" and 20". The only difference is the width of the wheel. So that's all u need to get an eye one, whether you chosen tire can be mounted on whatever width your wheel is.

It's really about the overall tire diameter in the end. Not saying there aren't things to consider when having 17" wheels, but it should be most the same info

I agree with you gonefishin776. There are definitely some pricing differences in the 17" tire sizes - especially the LT275-70-17 Rubber my Outdoorsman has - very few tire manufacturers selling in this size. Moving up to a slightly bigger dia. LT285-70-17 gives you way more selection and actually cheaper costs in most cases.
 

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I have searched and posted this in the wheel section without much luck yet, so I guess I'll try here.

I'm new here and this will be my first Ram but not my first truck by any means.

I ordered a 2013 Sport crew 4x4 and the dealer agreed to work with me on the wheels and tires.

I don't like or want 20" wheels so they will keep those and I wanted these.

http://www.discounttire.com/dtcs/filterWheelProducts.do?brd=MB+Wheels&fin=Black&dVeh=dVeh&bp=&c=4&rcz=48060&yr=2007&fqs=true&wd=17&rw=&vid=011074&rc=MPHINT&sortBy=prca&toggled=

It the TKO. they come with 2 offset options, -6 or 18

i want to run a ~32-33" tire combo so I am wondering which off-set to buy that will work with tires I am looking at.

I am looking at the BFG 265/70/17 which is only 31.8.

but also looking at 285/70/17 which are 32.8

which wheels do I need and will the LT 285/70/17 fit this model Ram?

The factory 20"s are 33" in dia, so I am just trying to convert over to 17" with that same dia, less wheel, more tire. I want to keep it close to stock as possible..

Thanks
 

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Discussion Starter #12
That's pretty cool that the dealer is going to work with you like that. I like those wheels. To answer your question...either of those tires sizes should fit fine. I personally would stick with the larger one. I would think the shorter tire would look noticeably too short. The 285/70/17 is pretty close to stock height and only a tad wider but not enough be rub anywhere. Either of those wheel offsets should work fine as well. It just basically comes down to how you want the wheel and tire to fit. The 18 offset will fit basically like stock. The -6 offset will stick out about an inch more than stock.

Hope this helps!
 

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Yea, I want to keep it as close to stock as I can, but just more tire and less wheel. So I guess I need the wheel with the 18 offset. This will be ok with the 285's? So no extra space is needed?

Is backspacing a concern with this setup with these specific wheels?

Thanks !!
 

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Discussion Starter #14 (Edited)
The 285's will fit fine with no issues with either of those offsets. Backspacing is always a concern when fitting aftermarket rims but I don't think you need to be concerned with it. Backspacing is a product of rim width and offset and you already know that you are fine in those areas. The stock 20" rims for example are 9" wide with about +18 offset. If a 9" rim with "x" offset will run then an 8" rim with the same offset will certainly run with room to spare. You wouldn't really need to worry about backspacing unless you were going to a wider rim or a rim with more positive offset than stock and you are doing neither.


**EDIT**
Let me correct myself on what I said earlier about the +18 offset sitting the closest to a stock 20" rim. I wasn't taking into account the narrower rim that you are swapping to. I know I keep comparing things to the stock 20's but that's what I know so that's what I use, lol. Going from a 9" rim to an 8" rim of basically the same offset will subtract that inch on the front and back of the narrower rim equally. So the 17x8" rim with +18 will actually stick out about a half inch less than a stock 20" rim would. For that reason I would say you might want to consider the -6 offset rim. Going to a -6 offset in the 17x8" rim would make it stick out about an inch more than the 17x8" rim with +18 offset or for comparison sake, it would stick out about one half inch more than the stock 20" rim. Personally, I would rather it stick out a half inch more than tuck in a half inch more but that's just me. You should look at a truck with the stock 20's and decide for yourself.
 

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The 285's will fit fine with no issues with either of those offsets. Backspacing is always a concern when fitting aftermarket rims but I don't think you need to be concerned with it. Backspacing is a product of rim width and offset and you already know that you are fine in those areas. The stock 20" rims for example are 9" wide with about +18 offset. If a 9" rim with "x" offset will run then an 8" rim with the same offset will certainly run with room to spare. You wouldn't really need to worry about backspacing unless you were going to a wider rim or a rim with more positive offset than stock and you are doing neither.


**EDIT**
Let me correct myself on what I said earlier about the +18 offset sitting the closest to a stock 20" rim. I wasn't taking into account the narrower rim that you are swapping to. I know I keep comparing things to the stock 20's but that's what I know so that's what I use, lol. Going from a 9" rim to an 8" rim of basically the same offset will subtract that inch on the front and back of the narrower rim equally. So the 17x8" rim with +18 will actually stick out about a half inch less than a stock 20" rim would. For that reason I would say you might want to consider the -6 offset rim. Going to a -6 offset in the 17x8" rim would make it stick out about an inch more than the 17x8" rim with +18 offset or for comparison sake, it would stick out about one half inch more than the stock 20" rim. Personally, I would rather it stick out a half inch more than tuck in a half inch more but that's just me. You should look at a truck with the stock 20's and decide for yourself.
ok, I am trying to sort through that, and I really appreciate the help.

they are these two size wheels, both are 8.5 wide!! you mentioned 8" in your post.

here are the sizes and I would like to go with the LT285/70/17 load D BFG AT KO, blackwall out.

17X8.5 5-139.7 18MTB

17X8.5 5-139.7 -6MTB

It says something on the discount site about negative offset can be bad???

am I in that discussion?

http://www.discounttire.com/dtcs/infoWheelOffsets.dos
 

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Discussion Starter #16
My bad. I thought the rims you are looking at were 8" wide. I see now that they are 8.5" wide. No biggie...either rim will still fit and run fine with a 285mm wide tire. The only question is do you want them to tuck under a tad more than stock or stick out a tad more than stock?

I tend to over explain things so let me try to simplify a little. As I said earlier, I use the stock 20x9" rims as an example because I know a little about them and you can go to any lot and look at how they fit. So here's the important part.

With the 17x8.5 with +18 offset you would basically be cutting 1/4" off of the front and back of the rim as compared to the stock 20" rim. So this wheel would have 1/4" more clearance on the inside and tuck under the fender 1/4" more as compared to a stock 20" rim.

With the 17x8.5 with -6 offset you would be creating 1-1/4" of extra clearance on the inside of the rim and it would stick out from under the fender 3/4" more than a stock 20" rim.

Which of these fitments you prefer is really up to you. You probably aren't really going to notice a tire and rim that tucks in 1/4" more than stock (the +18 offset). In fact, the 285mm wide tire will basically make up that 1/4" so this combo should sit almost identical to the stock 20" tire and rim combo. You will, however, probably notice a tire and rim that sticks out 3/4" more than stock (the -6 offset). Now I don't think this would look bad or anything....some people actually like that look. But as I said earlier, it's really personal preference.

And lastly, no you don't need to worry about that warning. Wheels with large negative offsets (that push the wheels out from the vehicle a lot) can cause suspension and tire wear problems but the offsets you are considering are nowhere even close to enough to be concerned about that.

See there....even my simplified explanation turns into half a page, lol.
 

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My bad. I thought the rims you are looking at were 8" wide. I see now that they are 8.5" wide. No biggie...either rim will still fit and run fine with a 285mm wide tire. The only question is do you want them to tuck under a tad more than stock or stick out a tad more than stock?

I tend to over explain things so let me try to simplify a little. As I said earlier, I use the stock 20x9" rims as an example because I know a little about them and you can go to any lot and look at how they fit. So here's the important part.

With the 17x8.5 with +18 offset you would basically be cutting 1/4" off of the front and back of the rim as compared to the stock 20" rim. So this wheel would have 1/4" more clearance on the inside and tuck under the fender 1/4" more as compared to a stock 20" rim.

With the 17x8.5 with -6 offset you would be creating 1-1/4" of extra clearance on the inside of the rim and it would stick out from under the fender 3/4" more than a stock 20" rim.

Which of these fitments you prefer is really up to you. You probably aren't really going to notice a tire and rim that tucks in 1/4" more than stock (the +18 offset). In fact, the 285mm wide tire will basically make up that 1/4" so this combo should sit almost identical to the stock 20" tire and rim combo. You will, however, probably notice a tire and rim that sticks out 3/4" more than stock (the -6 offset). Now I don't think this would look bad or anything....some people actually like that look. But as I said earlier, it's really personal preference.

And lastly, no you don't need to worry about that warning. Wheels with large negative offsets (that push the wheels out from the vehicle a lot) can cause suspension and tire wear problems but the offsets you are considering are nowhere even close to enough to be concerned about that.

See there....even my simplified explanation turns into half a page, lol.
nah, that one come through good. so it looks like i can go with the 18 offset wheels, and the LT285/70/17 BFG ATs load D and it should be fine, I hope...
 

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Discussion Starter #18
I think so. Should be what you are looking for...should sit and look basically like stock, just less rim and more tire. Keep us updated.
 

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Do I need spacers?

I have an '06 1500 with the factory 20" wheel option. When I recently replaced the front pads and rotors I noticed that when I put the wheels back on and tightened the lugnuts through the full travel of the nut, the wheels were a little loose. I called NAPA thinking that I got the wrong rotors and they told me to pump the pedal. Obviously when you do that, the pads grab the rotor and everything then seems tight. That doesn't seem right to me though as I wouldn't think the pads need to stay tight on the rotor. Seems like tightening the lugnuts should get everything tight. Sometimes when I brake hard at highway speeds, I get a good shimmy. Bottom line question - do you guys think I need a spacer so I don't run out of travel in the lugnuts? Thanks.
 

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Discussion Starter #20
Man.....not sure what to make of that. I'm not very savvy when it comes to brake stuff but I can't think of any reason why your wheels wouldn't be tight and firm when the lug nuts are properly torqued down. Are they still that way? If there is any movement in the wheels at all then there is definitely a problem somewhere. It would almost definitely cause premature wear of the tires and probably the front suspension and could also do damage to the hub/lugs. I'm thinking you may be correct about getting the wrong rotors.

I can answer part of your question for sure. No, you do not need spacers. That may fix your issue but it's not the proper fix. If your wheels aren't seated firmly on the hub you need to find out why and address it. If your wheels are still loose like that I would recommend you demand a replacement set of rotors and try that first. You may have to get right with them to get another set but the bottom line is that it really is a safety issue.

I would alsorecommend you repost your situation in the third gen suspension help zone located here.
http://www.ramforumz.com/forumdisplay.php?f=192

I feel like your issue is more of a brake setup issue than a wheel issue. I'm sure someone with a little more knowledge on the braking system in our trucks can give you a good answer.
 
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