Staggered wheel sizes on MPS6

[99GTT]

Does anyone know the implications of running staggered sizes to the AWD system? Was thinking something along the lines on the following:

Front 225/35/20
Rear 265/30/20

As per trusty website TYRESAVE: Tyre Size Calculator the difference in rolling diametre is 1mm (666mm and 667mm). In the scheme of things, would this difference effect the driveline? I think it works out to be 0.15% difference.

Has anyone had any issues in the past, or can anyone forsee any other issues with this set up on a 6?

Cheers!

[Grajy]

With different rolling diameters, I can see a problem occurring with your centre diff...
I wouldn't risk it

Jon

[kmh001]

If those numbers are correct, and the diameter difference is only 1mm, theoretically you should be OK. I have found that more than 4mm difference causes problems. But it's an expensive experiment if it doesn't work out.

But how are you going to fit 265's under the guards?

BTW Jon there is no centre diff, instead they use a diff coupling which is essentially a clutch pack.

[99GTT]

If those numbers are correct, and the diameter difference is only 1mm, theoretically you should be OK. I have found that more than 4mm difference causes problems. But it's an expensive experiment if it doesn't work out.

But how are you going to fit 265's under the guards?

BTW Jon there is no centre diff, instead they use a diff coupling which is essentially a clutch pack.

I guess if you were ocd you could always run the rears 1 or 2 pounds lower to make up for 1mm in rolling diameter.

Am looking at a set of staggered 8" & 10" wheels, 5x114.5, +40, 71mm bore. Would they not fit in the rears?

Would be awesome to see big fats from the back...

[BOOOSTED]

Apart from diff, the only other thing thats worth a mention (also 2 wheel drivers out there.) is you need to keep in mind poternetial implications with ABS...if you go with heaps of "stagger" (in this case sweet .....all )

[projectrracing]

BTW Jon there is no centre diff, instead they use a diff coupling which is essentially a clutch pack.

Wanna explain how a diff coupler with clutch plates in it isn't a diff? Sounds like a diff to me.

[kmh001]

Wanna explain how a diff coupler with clutch plates in it isn't a diff? Sounds like a diff to me.

I'm amazed that you could mistake a clutch pack for a diff. They don't employ the same components, they don't work the same way and they don't even perform the same function. Ordinarily I would suggest that you look it up because it's been covered elsewhere a million times. But you just sit there and I'll explain it for you:

From Wiki "A differential is a device, usually but not necessarily employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs."

The diff coupling in the 6MPS has one shaft, one input, one output, no gears, and most importantly, it doesn't add/divide or average anything. It is not a diff.

[Grajy]

I'm amazed that you could mistake a clutch pack for a diff. They don't employ the same components, they don't work the same way and they don't even perform the same function. Ordinarily I would suggest that you look it up because it's been covered elsewhere a million times. But you just sit there and I'll explain it for you:

From Wiki "A differential is a device, usually but not necessarily employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs."

The diff coupling in the 6MPS has one shaft, one input, one output, no gears, and most importantly, it doesn't add/divide or average anything. It is not a diff.

The 'slipping' coupler is commonly known as a centre diff. It's not a conventional differential as it doesn't have a gear reduction involved.
A 'clutch pack' in between the gearbox output shaft and the rear differential input shaft is commonly called a 'centre diff'.
It's not healthy to have different speeds in and out of the centre diff for long periods of time.
BTW, the poster of this thread should also consider the centrifical force of the extra weight of the proposed larger wheels/Tyres. Extra power will be needed to turn these wheels. Again, puts load on the centre diff.
Staggered wheels (that size) = not a good idea.

[kmh001]

I disagree. 4wd and awd platforms like the subaru employ and actual centre differential to distribute an input from the gearbox into two outputs, one to the front diff and one to the rear diff. This is a centre differential, it's an actual differential and has three shafts and it averages the two outputs. Centre diffs have become more sophisticated and can have viscous couplings added to them to control the differential action.

I guess you could become confused about this when reading about the rather unique mitsubishi evo awd system

But the fact remains that the 6MPS uses a PTO and diff coupling. It very definitely does not have a centre diff.

[Grajy]

The description you made on your 'centre diff' is actually called a 'transfer case'. It has gears, but no reduction is made. Just changes direction of the power flow.
This description from wiki should help a little better...

http://en.wikipedia.org/wiki/Differe...hanical_device)

In a four-wheel drive vehicle, a viscous coupling unit can replace a centre differential entirely, or be used to limit slip in a conventional 'open' differential. It works on the principle of allowing the two output shafts to counter-rotate relative to each other, by way of a system of slotted plates that operate within a viscous fluid, often silicone. The fluid allows slow relative movements of the shafts, such as those caused by cornering, but will strongly resist high-speed movements, such as those caused by a single wheel spinning. This system is similar to a limited slip differential.
A four-wheel drive (4WD) vehicle will have at least two differentials (one in each axle for each pair of driven roadwheels), and possibly a centre differential to apportion torque between the front and rear axles. In some cases (e.g. Lancia Delta Integrale, Porsche 964 Carrera 4 of 1989[7]) the centre differential is an epicyclic differential (see below) to divide the torque asymmetrically, but at a fixed rate between the front and rear axle. Other methods utilise an 'Automatic Torque Biasing' (ATB) centre differential, such as a Torsen—which is what Audi use in their quattro cars (with longitudinal engines).
4WD vehicles without a centre differential should not be driven on dry, paved roads in four-wheel drive mode, as small differences in rotational speed between the front and rear wheels cause a torque to be applied across the transmission. This phenomenon is known as "wind-up", and can cause considerable damage to the transmission or drive train. On loose surfaces these differences are absorbed by the tire slippage on the road surface.
A transfer case may also incorporate a centre differential, allowing the drive shafts to spin at different speeds. This permits the four-wheel drive vehicle to drive on paved surfaces without experiencing "wind-up"..

(I wrote out a description myself, and then somehow deleted it before posting... FML. )

---------- Post added at 07:40 AM ---------- Previous post was at 06:56 AM ----------

I've also had a look at some other threads on this site about torque distribution, and I'm sorry to say, but most of it is incorrect.

In 2 mins searching I found this...

6 MPS (MAZDASPEED6 In The U.S.)
"Active Torque Split" proactive automatic all wheel drive. Normally front-wheel drive vehicle. Electronically controlled multiplate electromagnetic clutch transfers up to 100% of torque to the rear when needed. Limited-slip differential in the rear.

The MAZDASPEED6 with advanced AWD system analyzes real-time data on steering angle, yaw rate, lateral G-force and engine status to establish up-to-minute road surface conditions, and the vehicle's dynamic status. Normal, Sport, and Snow modes give the perfect amount of torque where it is most needed, and have a performance reaction that leaves conventional gear- or fluid-controlled systems in the dust. Front/rear torque distribution varies from 100/0 to 50/50.

Source: Mazda USA - The Official U.S. Site for Mazda Cars, Crossover Vehicles, SUVs and Trucks

The current Honda Legend, and the now extinct MDX have/had this system. (I will just quickly say now that the CR-V is a completely different setup). Simply put, it's a shaft that goes into a coupling, with wet clutch discs and metal plates. In normal operation, the input slips inside the coupling, producing NO output. When the vehicle needs it, the ECU will send a signal to the 'coupler', magnetizing the clutch plates and discs, locking them together to provide FULL output. It can be varied with lower current to allow output slip. Same output speed, just less torque.
I've just now learnt how the system works (because I haven't bothered to learn), and am trying to pass on some correctness here.
This electro-magnetic clutch system is fantastic. As I said, the Legend has this in the rear diff (instead of seperately) in the SH-AWD badged vehicles, and does the same job.

That 'switch' you have in your car to turn of the rear diff, just stops any power to the electro-magnetic clutch pack, and then enables FULL front wheel drive mode. This switch backs my description.

If you disagree at all, I'm happy to explain this better.
P.S. Just before I go, I do disagree with the extract I pulled and posted before. The electro-magnetic clutch arrangement on the 6's DOESN'T allow for 100/0% torque to the rear, it SHOULD say 100/0% torque to the front wheels, and up to 50/50 torque split, front and rear.
The 6 is primarily a FWD vehicle until rear drive is needed...