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Discussion Starter · #1 ·
I have 15x7 caprice alloys. I want to put 17s on.

The stock backspacing on those is 4 inches.

I think the 17s will clear the tie rod end (spindle nuckle) because of the bigger diameter.

Is there a max on the front backspacing??

I am pretty sure I can go 5 7/8 in the back with no problem (leaving room for the bead of the tire ~1")

I know this question has probably been asked a GAZILLION times but I would appreciate any help on the subject.

Thanks
Tim

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Torquemaster
1995 Caprice LT1
 
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Discussion Starter · #2 ·
Tim
The backspacing on the stock wheels should be 5 3/16". My wifes '94 has 17x9.5" on the front with 5.5" backspacing. Perfect fit with no problems.

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Gary- HOTSS
1994 BBB Impala SS
1995 BBB Impala SS
2000 C5 Hardtop
1996 C4 CE Coupe
Chevy Collection Pictures
[email protected]
 
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Discussion Starter · #3 ·
Actually stock SS wheels (17x8.5") are 5 1/16" backspacing.

If you run 9.5s, use the 5.5" backspacing.

BTW, if you DO hit anything, it'll be the front swaybar (long before you have to worry about tierod clearance).

Ed
 
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Discussion Starter · #4 ·
my SS rims rub when the wheel is fully turned to either side, but its not bad, and hasn't resulted in any cosmetic or mechanical damage, they're the stock chevy SS rimSS 17x8.5, no idea about the backspacing
 
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Discussion Starter · #5 ·
Hey Ed, when you go to wider rims, does the backspacing have to change, i.e. is 5 1/16 backspacing on stock 8.5" rims different than 5 1/16 backspacing on 9.5" rims? If the backspacing stays the same, wouldn't a wider rim increasingly grow toward the inside, eventually rendering it too wide?
 
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Discussion Starter · #6 ·
G Man

I may not understand how backspacing is measured. I measured from the inside face of the rim that goes flush against the brake drum to the lip of the inside part of the rim.

-l
l_______
l
l
l
L------Ll
l
l
l
_______l
l
-l


from L to L This being the inside of the rim.

I measured it on my full size spare in the trunk. It was 4 inches. these are the 15x7 alloy rims on my 95 Caprice.

thanks for the info on the backspacing. I want to buy some 17 x 8 to 91/2 depending on the prices I can find.



[This message has been edited by torquemaster (edited October 31, 2000).]
 
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Discussion Starter · #7 ·
The backspacing doesn't HAVE to change when you go wider, but you probably want it to. If you add width, you want to add it BOTH to the outside AND the inside of the wheel centerline. And yes, there will come a point where you can no longer add width due to clearance (usually problems on the inside first on the SS).

Reason why adding both outside and inside is is vital : it's important for wheel bearing life to not change (much) where the wheel bearings are lined up relative to the centerline of the wheel. If you change it much, it starts putting some higher loads on the wheel bearings and can destroy them in pretty short order!

Extreme case is those lowriders that have 13x7" rims with basically NO backspacing (i.e. backspacing around 1" or so). I have heard a few mechanics refer to those vehicles as "Wheel Bearing Cash Machines"


Not to mention, a small change in backspacing can significantly change how a wheel looks when mounted on the car. I know that on my SS that when I installed the TCE Wilwood brakes (which space the front wheels out 0.25" on each side, effectively REDUCING backspacing by that amount) that it was a quite noticable (and better IMHO) change in appearance.

So, on an SS, I'd go with<UL TYPE=SQUARE><LI>4.75" backspacing for 8.0" wide rims<LI>5.0" backspacing for 8.5" wide rims<LI>5.25" backspacing for 9.0" wide rims<LI>5.5" backspacing for 9.5" wide rims[/list] on the front of the car. You're probably gonna be looking at either 9.5" wide or 11" wide for the back. For 9.5" wide, use the same backspacing as the front. For 11" wide, you'll have to measure it as the car-to-car variation is enough that you basically can't predict what will be needed (and it probably will be different on L and R sides!).

Ed
 
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Discussion Starter · #9 ·
thanks for the info guys.


By that drawing, my backspacing is equal to 4 1/4 inches on my stock 15x7 alloys.

I think that gives me the info I need.

Other than how wide of a tire can an 8" rim take? 275 40 17? Is that too big?

Would that fit on a stock 81/2 17 SS wheel?
thanks
Tim
 
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Discussion Starter · #10 ·
I'm still not 100% understanding this whole concept, but simply put, as backspacing increases, does the rim start to grow toward the inside or outside?
 
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Discussion Starter · #11 ·
T-Master,

There are literally hundreds of SS owners using the 275/40 17 on stock rims without incident. I'm one. Good Luck

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Scott Miller
Warden/JAILerSS
Jax Area Impala SS Lovers
'96 BBB - mods!
 
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Discussion Starter · #12 ·
SSlimo

As the backspacing increases, the rim becomes DEAPER to the inside. More rim is covering the 3rd member housing. the farther inside the rim is. The less deap the outside of the rim you can see is.

I hope one of those descriptions covers it for you. It can be confusing.


CloakedSS

thanks for the info on the tire size.

ONe more question for anyone willing to answer


will the speedo be off with the 275 40 17? Does anyone know the hight of the tire?

I guess a tire store will know this.

Thanks
Tim
 
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Discussion Starter · #13 ·
275s work fine on stock SS rims (8.5" wide) but do NOT work well on only 8.0" rims. A HAIL member had them (275s on 17x8.0" rims) in Houston, and basically they kept damaging his rims on potholes and such. After paying to repair 3-4 rims, he gave up and went back to 255 wide tires.

There are many tire height calculators out there on the web. In summary, a 275/40R17 is 25.66" in diameter while a 255/50R17 is 27.0" in diameter. So yes, you need to reprogram the PCM or your speedo (and odometer) will be off.

Ed
 
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Discussion Starter · #14 ·
As far as tires go, I have 17x8 on front with a 245/45 tire(Looks good). Rear is 17x10 with 285/40. I went with the 45's on front so the tires front and rear would be the same height(approximately). a 40 on the front would have made the front tire shorter than the rear. As soon as I get better pics I will post em so you can see what these sizes look like. For now, I posted as few crappy pics in "Wheels & Tires" section
 
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Discussion Starter · #15 ·
I am also running a 17x8 with a 245/45 on the front.I was trying to get kind of a dragster look with the tires tucked well into the fenders.on the rear I have 17x11 with a 315/35

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Discussion Starter · #16 ·
Prossound
How did you fit 11 x 17S??? what kind of offset did you use?? YOu didn't have any problems with rubbing?

Did you modify your wheelwells?

Thanks for everyone's help.

I probably should plan on at least 81/2"
rims. (17) with a 5 1/2"offsets.

To fix the speedo, do you have to buy an aftermarket attachment?? Can a transmission shop do that? Or the dealer without having to buy a part or chip??

I really don't know how it works.

Thanks

Tim
 
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Discussion Starter · #17 ·
a:) measure measure measure!!!!

b:)if my control arms were not torn up from the shifts they would not touch anywhere but I do get a light touch from time to time with no modifications

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My Home Page
[email protected]
Just wait for the mod list I am building

as Sinatra said "I feel sorry for people that don't drink,because when they wake up in the morning that is as good as they will feel all day long"
 
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Discussion Starter · #18 ·
Okay, I think I got it; as backspacing increases, the lugnut holes start to get closer to the outside? So between a stock (8.5" wide) SS rim and another 17" rim (8.5" wide) with 6 inches backspacing, 6" backspacing rim would have less rim on the outside but more on the inside?
 
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Discussion Starter · #19 ·
You got it. . . the greater the backspacing, the deeper the rim is on the INSIDE. the shallower the rim is on the outside.

Tim
 
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Discussion Starter · #20 ·
This is a cool post with detailed reposes from Ed. Thought it deserved a TTT!
 
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