I'm new to this and need to get some basic info. I have an '01 X se. What is the relationship between backspace & wheel spacers and what do they do?
If I run 16x8's with a 5" backspace how far-out will the wheels be outside
the fender edge ? thanx.

stock backspace is 5.5"...therefor your tires will stick out half an inch farther than stock

this is my X with 1.5 spacers

http://i39.photobucket.com/albums/e192/fallen9210/DSC_7312.jpg

Thank-you much for that info. What are spacers,what do they do?

They widen the wheel base. But be careful, the wider you go, the more rubbing issues you may have. I had to trim alittle plastic to run stock tires with my 1.5 inch spacers

Spacers go between the back of the wheel and the front of the brake drum/rotor, pushing the wheels further out and making the wheel-track wider.

However, if you do get wheel spacers, don't cheap out on them. Good ones will be concentric (outer diameter is located in the same position to the inner diameter) and the studs you will be bolting your wheel to will be pressed-in (IIRC, I may be wrong on the pressed-in part).

Cheap wheel spacers (really, wheel spacers in general) can be dangerous because it puts more stress on the lugs. Pushing the wheels outwards essentially makes them act as a lever, putting more pressure than normal on the wheel studs. And, with wheel spacers, you'll have 2 sets (12 lugs) per wheel rather than just 6.

I'm not trying to tell you "Don't get spacers", but I want to make sure you know that wheel spacers can be dangerous; especially the cheap ones. I should also note that a few guys here run wheel spacers with no problems, such as fallen for example lists that he runs 1.5" spacers in his signature.

I should also note that generally speaking, 1.5" spacers are pretty safe. Once you get much thicker than that (2"+) is when they start to get pretty unsafe. Keep it at/under 1.5" and you should be ok, and don't get some cheapo $65 for all 4 pieces of crap. Expect to spend $150+ for a good set of spacers.

http://farm6.static.flickr.com/5182/5606802619_78e546b7c7_o.jpg

Backspacing is the distance from the brake side face of the rim, where it mounts to the face of the hub....

To the outside edge of the rim lip.

If you lay the rim on its side, brake cavity facing up...

And lay a straight edge across the rim opening...

And measure straight up from the hub face to the straight edge....

THAT'S the Backspacing.


The MORE Backspacing, therefore, the deeper that brake side cavity will be.

The DEEPER that cavity is, the more the brakes are TUCKED INTO IT when the rim is mounted.


So - The MORE BS, the more tucked into the well the rim is.

The less BS, the more the rim sticks outboard.



For an IFS equipped rig (Xterra) - the less BS, the wider the arc the tire swings through on turns, and the more stuff it can hit.

The more BS, the tighter the arc, and the fewer things that get hit.

So, 5.5" of BS - for the 2000 - 2004 Xterra, is optimal for tire clearance.


A Wheel SPACER mounts between the hub, and the rim.

This effectively LESSENS the BS, as it spaces (SPACES) the rim outboard...away from the brakes, etc....so the tire swings in a wider arc.


As far as performance, wear and tear on wheel bearings, etc....there is NO DIFFERENCE between a rim with 1.5" LESS BS, and a rim with the SAME BS, but, 1.5" Spacers.

For obvious reasons, its simpler to have the rim have the BS you want, than to have to buy the rims AND spacers.


So - A spacer simply reduces the BS by the spacer's thickness....widening the track/robbing tire clearance, etc.




A wider track is a good thing in general, as it improves your center of gravity and off camber stability, etc....but, for the front end of the X, it does limit your tires to smaller sizes.


So, I can run 33 x 13.5/16's on 5.5" BS rims:

http://farm5.static.flickr.com/4129/5002324307_8298ccbbf8_o.jpg
Which looks like this.

VS

http://i39.photobucket.com/albums/e192/fallen9210/DSC_7312.jpg
This, With Less BS




:wink-big:

Wouldn't the extra inch of wheel width also figure into how far out it would be? For example, I'm interested in a set of wheels with 4.88 bs. The wheels are 16x8. So if it's 4.88 from the hub mounting point to the inside lip of the wheel, wouldn't that mean that the extra inch of wheel width over my stock 16x7 would all be to the outside? If I'm figuring correctly, the outside wheel lip would be 1.72 inches further out than stock. Or in the OP's case 1.5 inches including the extra inch instead of just the .5 from the bs difference. Or am I totally wrong? It's all a bit (a lot) confusing to me. I'm currently running 265/75 16 BFG KM2s and don't have any rubbing issues. I cranked the t-bars to get the front up 1 1/4 to level it but they didn't rub before. I'll be removing my mudflaps and don't mind some plastic trimming but I don't want to get too excessive. I would be running the same tires on the new wheels.

Wouldn't the extra inch of wheel width also figure into how far out it would be? For example, I'm interested in a set of wheels with 4.88 bs. The wheels are 16x8. So if it's 4.88 from the hub mounting point to the inside lip of the wheel, wouldn't that mean that the extra inch of wheel width over my stock 16x7 would all be to the outside? If I'm figuring correctly, the outside wheel lip would be 1.72 inches further out than stock. Or in the OP's case 1.5 inches including the extra inch instead of just the .5 from the bs difference.

Or am I totally wrong?

It's all a bit (a lot) confusing to me. I'm currently running 265/75 16 BFG KM2s and don't have any rubbing issues. I cranked the t-bars to get the front up 1 1/4 to level it but they didn't rub before. I'll be removing my mudflaps and don't mind some plastic trimming but I don't want to get too excessive. I would be running the same tires on the new wheels.


Nope, you have it completely and utterly wrong.

:D

The BS is the BS....notice you don't even need to know the rim width to find it.

Its independent of the rim width.

If I laid a wider rim as in the pic above, lets say its a FOOT wide rim....

...and it has 5.5" of BS...

...my ruler and straight edge would look EXACTLY like they do in the picture.

So the brake clearance for a 16 x 7 rim with 5.5" of BS is the same as the brake clearance for a 16x12 rim with 5.5" of BS.

The OFFSET WILL change with rim width, if the BS stays the same though....because its measured differently.


As for TIRE width...for a truck tire...the rim's width really doesn't change the tire width, it just puckers/unpuckers the hole in the middle in/out a bit.

It makes more difference for a car tire, where the sidewalls are much shorter.

So, a wider rim doesn't make the tire a different size....or change the clearance, or how far out the tread sticks.

The tire, when mounted, is pretty much stuck onto the rim, with the center of the tire, centered on the center of the rim.


If the RIM is wider...the tread is not wider...and, the center line is still the center line, etc.


So, A wider TIRE will stick out more than a narrower tire...because it sticks out more away from the center line.

A 2" wider tire will stick out 1" more outboard (Half is sticking more inboard - and half is sticking more outboard.)


So, I would much rather get a wider track with a fatter tire, than a skinny tire on outriggers...

...because fatter tires do more for me off road, and ON ROAD, anyway.



The practical limit for the X (1st gen at least) is a 13.5" wide tire (LTB's in pic)


(~ 345 mm)



If we call a 265 mm tire our baseline (~ 10.5") as its a stock size...and what a 31 x 10.5 tire would offer...


....I can increase my Track (Only discussing ONE SIDE for now....) by ~ 40 mm (Half the difference of 80 mm/tire) with 13.5's. (~ 345's).


If you use a 1.5" spacer, or a rim with 1.5" less BS, you'd be trimming to fit 265s on there.

So, you'd add 1.5" to your track.

1.5" = 38.1 mm

So, my 13.5" tire with 5.5" of BS has a little more track width than the 10.5" tires with 1.5" spacers.



:D

If you run 12.5" tires (A more popular size...it only decreases the track on one side by 0.5" from the 13.5" tire)... its still out ~ an inch more than stock, etc.

:wink-big:




PS _ If you run the smaller amount of BS you describe, with the 32 x 10.5 tires you describe, you will have severe trimming to do...on turns, the rears of the front tires will be against the wells about where that little ledge your mud flaps used to screw into....so that ledge is history, and, potentially, some more between that and the leading edges of the front doors at those corners. (It sounds scarier than it is...its not THAT big a deal...)


Typically, 4.5" of BS and 32's = Metal trimming.

Typically, 4.88" BS means just plastic...but ALL of it there, is going bye bye...and it still may rub on turns, or when the suspension compresses, etc.

(On compression/uptravel....Tire room made with suspension goes where your lap goes when you stand up.)

A Body Lift is best for that situation....or just using rims with 5.5" of BS...so you can one day get LARGER tires if you wanted to.

:D

Thanks for the info. Fortunately I have prior experience at being wrong so it wasn't exactly shocking. I'll get some pictures posted as soon as I get some new wheels, sliders, mudflaps removed, trimming, crying, saying things I probably shouldn't...you get the idea.