Chevy Impala SS Forum banner
1 - 20 of 26 Posts

· Registered
Joined
·
12 Posts
Discussion Starter · #1 ·
Hello everyone I've been on the forums for about a week now and been reading all the stickies and trying to educate myself. Tons of great info. I've always been a chevy and buick guy and I want to get a RMS with the LT1. I've been planning the whole build step by step in which order I want to do things so I don't have to backtrack and change/redo things later. So to start to get to my questions I think I want to use 275/40r17 tires because I want a wide tire all the way around (and it seems to have the most selection). The wheels I want are American Racing AR500 in 17x9or9.5. The question is what would the perfered offset and backspacing be for those widths and width would be the wisest. I want the same size at all corners and the same size offset/backspacing on all wheels if possible? And yes I have readthe stickies on backspacing and used the search that's why I haven't posted anything for a week;) I just would like to hear from you veterans of bbodies so I can get some of your wisdom!

Thanks again,
Stu
 

· Registered
Joined
·
117 Posts
you can't fit as aggressive of a wheel on the front as you can in the back, iirc, so the same all around might end up looking kinda sunk in the rear...for 9.5" wide, you probably want 5" backspacing, maybe 4.5"...i'm not sure, but i've been doing research like you and have found it nearly impossible to nail this stuff down because no one seems to post specs when they post pics...definitely interested in replies from vets
 

· Premium Member
Joined
·
1,785 Posts
Neil, I can't agree with you. I have posted pics and specs of my setup many times on here as well as PM replies. I have seen literally hundreds of details added. And now the older posts have been recently recovered, the info is here.

OP. I can tell you what to do on a 94-96 Impala, but can't help with RM, sorry.
 

· Premium Member
Joined
·
3,776 Posts
OK, so you've read the stickies, etc....did you find the offset/backspace calculators?

Start with a couple of things....this discussion is about 8.5" rear axles only. RMS has a "narrow" rear axle--of the 2 sedan versions used between 1991-1996 (narrow only 91-92), it is 32mm narrower (total width) than the axle used on some Chevy sedans 1993-1996 with the revised wheel opening configuration. This works in your favor, but it may still limit your options at the 9.5" wheel width--depending on tire size choice and offset/backspace options available. You get an extra 16mm (5/8") per side to work with, in other words, but the body opening of the RMS probably takes most if not all of that away. To be clear--to do what you are wanting to do, you DO want to use the axle housing in the car now. There is nothing good to be achieved by using the wider housing with the RMS body design.

Stock Impala SS wheels are the reference starting point for your evaluation of what is possible.

17 x 8.5" bead width - total wheel width edge to edge is close to 9.6" due to rim design (extra material on inside, wheels designed for clip weights)--typically total width (such as a steel wheel) will measure 1" more, so an 8" wheel will measure 9" edge to edge.

+6mm offset = 5.06" backspace

You will find that these wheels with stock SS tire size (255/50-17) fit & clear RMS with no rear clearance problems (assuming car is "square" side to side).

275/40-17 has been used on stock Impala SS wheels by many, even though specs for this tire size typically calls for minimum 9" width (example--2000-2002 Camaro SS used this tire size on 17 x 9 wheels). These (Camaro) wheels are high-offset (+50mm), and used a spacer or adapter to fit on vehicles with more conventional suspension designs with lower wheel offsets, such as the B-body. This is driven by FRONT suspension design, brake rotor hub projection, etc.

There are some aftermarket wheels (American Racing, Coy's, and a number of others) that do provide a range of fitment for B-body (5x5, width choice, offset needed) to accommodate your quest.

Start by determining what amount of room you have to work with when an Impala SS wheel & tire is fitted to your car, and calculate from there.

Every 1/2" of additional bead width will add to the positive offset calculation by just over 3mm, so a 9" wheel should probably have +10mm offset. Many of the wheel suppliers making B-body wheels (those mentioned) often choose to express the wheel specs as backspacing rather than offset, so you would find a 9" wheel (10" total width) would be offered with a 5.25" or 5.5" backspace to position the wheel (and tire) safely within the available space the RMS offers.

Another thing you should determine before going too far into this endeavor is how much body clearance difference your car has at the rear--many B-bodies are NOT even, side to side, and since we're dealing with nearly 20 year-old (minimum) vehicles, if the car has ever been hit, and not knowing condition of rear suspension links or body mounts, you need to determine whether the amount of room you will have to work with is as equal as possible on both sides (is rear axle lateral position OK, in other words) and determine what can be done to correct it if you find it is NOT equal within 1/4" (ie. 1/8" either direction).

Probably very little if anything I've really contributed that hasn't already been stated in other posts over the years regarding this general topic.

What wheels are you actually considering? Give us some links to see what's available and look at what is offered in width and offset (or backspace).
 

· Premium Member
Joined
·
1,785 Posts
It's the skirt in the rear and the axle width, I believe, is different. Also, I am not sure if the front fender relationship to the suspension is the same. It probably is , but I don't KNOW, so don't want to tell you something wrong.
 

· Registered
Joined
·
12 Posts
Discussion Starter · #8 · (Edited)
Bill wow thank you that was helpful the wheels I'm looking at are http://www.americanracing.com/wheels/VN47/VN0473

And thanks king that lines up with what bill is saying

Also if I figured out on a wheel does the front have enough space for a 9in wide rim or will hit swaybars and such.

Oh and yes bill I did find the calculators and I think I'm starting to figure how everything adds together lol
 

· Premium Member
Joined
·
3,776 Posts
Stock wheels already hit the front sway bar--actually it's the tires that make contact. Just the nature of the design, and only an issue at full lock, unless you end up running a wider wheel and/or tire--so expect it to be part of the "normal" for these cars.

American Racing re-introduces the Vector....I had 'em on my 73 Nova (14x7) 40 years ago--wish I had some pictures! Interesting history--the design of the wheel originally came (or was "borrowed") from GM, and was the wheel used on the 1973 Corvette XP897 "Aerovette" mid-rotary engine prototype that never came to fruition. Later, it was given a production "go" on the 80's Buick Regal Turbo & GN. It doesn't appear that this wheel is being offered as a 17", however/anyway.

As for the Rally wheels from Year One, my concern is that the offset/backspace is not favorable--the extra 1/2" of width is all toward the outside (putting the wheel closer to the body opening sheet metal). This is a zero-offset wheel, and ideally it would need to be at +15mm or +20mm OS (5.5" backspace) or no less than +10mm OS (5.25" BS) to be safe. And I could be wrong....

Really, it would depend on just how much you can gain, if anything, by massaging/rolling/trimming the sheet metal flanges on the inside of the rear wheel openings.
 

· Registered
Joined
·
12 Posts
Discussion Starter · #11 ·
Okie dokie sounds goods as this is all just planning I've have plenty of time to decide just trying to educate myself. Thanks bill for all you input I guess I'll iust keep looking for better option in the offset you said.
 

· Premium Member
Joined
·
3,776 Posts
limited 17" selection?

Tire Rack:

255/50-17 - 2 choices starting at $133 each

275/40-17 - 32 choices starting at $91 each (size OP wants to use)

285/40-17 - 7 choices starting at $169 each

There are additional sources offering all 3 sizes in other brands.

I think it won't be a problem to get tires for 17's for a good while.....how much more "choice" is needed?
 

· Registered
Joined
·
117 Posts
Tire Rack:

255/50-17 - 2 choices starting at $133 each

275/40-17 - 32 choices starting at $91 each (size OP wants to use)

285/40-17 - 7 choices starting at $169 each

There are additional sources offering all 3 sizes in other brands.

I think it won't be a problem to get tires for 17's for a good while.....how much more "choice" is needed?
wouldn't 275/40 be way too small a diameter?...285/45 will give the exact same diameter as stock tires...that's what i'm looking at

do you think a 285/45/17 tire on a 9.5" wide, 4.5" bs wheel fit in the rear?...or would i need to go 5" bs?...looking to push it out as far as I can to stay flush, but avoid rubbing...I guess I can roll the fenders too
 
1 - 20 of 26 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top