Big Willy

Can anyone tell me what size spacers would work best for a Stock wheel and tire set-up ( 17's ) with a conservative drop ( Springs )?
Does anyone have pics?
Winter is coming and I will be going back to the stock wheels and tires, but I'd like to fill the wheel well up a bit.
Thanks in advance...

Mister T

I'm on Eibach springs with stock 18's and running 15mm front and 20mm rear spacers.

Here are pics of my set-up...
https://www.clublexus.com/forums/sho...d.php?t=371272

Big Willy

That looks perfect to me. That's the setup I going with.

Mister T

I only caution you that I do experience some rubbing in the rear at full capacity. But since I rarely ever have 5 adults in the car, it's not a problem for me.

Big Willy

Would rolling the quarters fix that? Not a big concern, I normally don't have much in the back.

Mister T

Yes.

The total weight of my 4 spacers are less than 10 lbs. Adding more weight can't be a good thing for performance, so I will say it does but very minimally.

Also, as a result of the widen stance from adding spacers, the vehicle's stability and handling is slightly improved.

So to me, the looks and benefits are worth any loss in performance.

305is350

iTrader: (5)

I went 15mm all around (with prokit IS250) on my 350, and it never rubs.

Mister T

You're welcome meowCat.

15mm in the rear is a good choice too, it just wouldn't be flush enough for me.

Big Willy

You sound like an F1 fan. All your points are dead on, but my IS250 is slow and heavy if the entire drive train was made of carbon fiber my car would still be a slug...I am simply looking to add a little style without it being to noticable.

mikez

Nope, the spacer will have less inertia than your wheels. Say if your after market wheels are 1lb heavier than stock, your aftermarket wheels will have more inertia than a 1lb spacer with stock setup. Inertia depends on the radius of the density of mass from the center of rotation, and the closer it is to the point of rotation the lower the rotational inertia becomes. (basic formula for inertia I = mr^2 )

And the further the 2 wheels becomes from each other has nothing to do with how much power is being put to the ground, I have no idea where that came from. The power is transferred to the wheels via gearing inside the LSD that changes rotation of crank from one axis onto rotation via another axis.

mikez

I am an Engineering major, was a former Aerospace Mechanical but now Industrial . I think you should take my word for it

The swinging stick method need not apply since different forces are being applied in the case of swinging a stick, and rotating a stick. Swinging a longer stick will feel harder (ignoring the fact that the stick might bend) is trying to move a large object around its pivot point by pushing on the pivot point (etc opening a door by pushing on the hinges).

I can tell you that it takes roughly the same force rotate a full length chopsticks and a half length chop stick axial wise. The only effect on torque due to load for a rotational system is (other than inefficiencies) is exactly torque due to load... the load of the wheels, the load of the shaft etc.

So feel free to get them spacers for a sicker stance, I can give you approximation forumlas for motor and the steady state final speed w in rpm, and for a motor of 300hp, you will reach exactly same rpm about 0.001 seconds slower. Say 4600 rpm is when maximum torque is reached, that means with spacers you will reach maximum torque exactly 0.001 second slower than a stock car given that you both accelerate at the same time.

mikez

That is correct, Carbon fiber although strong, has a low modulus, strained and stressed enough time and suddenly you might find your carbon fiber gearbox and flywheels snap off like how that plane crashed over NY a long time ago, the entire carbon fiber rear stabilizer just fell off due to over stress.

lobuxracer

iTrader: (2)

Wow. Engineers and stuff. Nobody mentioned the two biggest issues with spacers - stud failure and bearing failure.

Increasing rotating mass? Sure a tiny bit. Increasing unsprung weight? YEP. 10 lbs worth. Expect a small loss of ride quality with the additional weight the suspension wasn't designed to handle. But most guys putting on spacers are concerned about visual performance, not mechanical performance anyway which is why I generally don't comment on anything related to bippu or VIP. This is my only post about fashion mods.

So, from an engineering perspective, you're changing the stress on the wheel studs which has been reported to cause sudden failure, and you're changing the stress on the wheel bearings which has also been known to cause sudden failure. The thicker the spacer, the more you amplify the stress on the studs and the wheel bearings.

The rest of the arguments are pretty esoteric (altered scrub radius, altered suspension geometry, change in effective spring rate, etc.), and again, fashion mods aren't my thing so I generally don't concern myself with threads like this. And spacers are most assuredly a fashion mod. But I was asked for an opinion, so here it is. No need to flame, I'm not going to respond.

mikez

Well I took this issue to our mechanical and materials science professors and the only issue was the shear force being applied on the stud when using a spacer with stock studs, this effectively double the normal shear stress which acts on the studs originally from the wheel itself. We came to the conclusion that with studs built into the spacer, and the spacer attached to original studs effectively eliminates any extra shear stress on the studs, the shear on the original stud will be slightly more (due to the weight of the spacer), and the shear on the spacer's stud is the same as the no spacer scenario.

I don't know about the wheel bearing since I have no idea what extra force is being added on there

lobuxracer

iTrader: (2)

The centerline of the wheel is in the same plane as the centerline of the wheel bearing with stock wheels. Using a spacer offsets the centerline of the wheel, so you no longer have equal lateral loading on the wheel bearing. Bearings are rated by service life at a given force. Moving the centerline of the wheel 20mm makes a HUGE difference to the wheel bearing's service life.

When I say centerline, think wheel offset as if you were slicing the wheel vertically between the beads on the rim.

Shear is not the only stress on a wheel and hub. There is considerable stress imparted by cornering - the forces are measured in tonnes. You don't seem to be considering the dynamic state of what the wheel does, and the leverage caused by the changes made when you add a spacer to the equation. The studs won't break while the car is sitting still. They'll break in the middle of a hard turn - probably the worst possible time.