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View Full Version : Front wheel drive rims vs. rear wheel drive????



Deep6
07-01-2002, 08:07 PM
What is the difference when rim manufacturers advertise that some of their rims are for a front wheel drive application and others are for a RWD application??

I'll give you my motive for asking. The tread on my crappy pep boys futura tires that I originally bought to last "for a year" is now going to be going on three years this september. Funny how the wallet determines things like that. Anyway, I won't be able to put it off any longer, I WILL have to get new tread for the upcoming winter season. I plan on putting a "All-season Z-rated" tire on my car. I intend to keep the sizes front to rear the same.

I'm considering the new "centerline rotary Forged" wheels due to the fact that they advertize unsprung weight savings in their ads. Unfourtunatly those rims that are the rotary Forged aluminum wheels are advertised for front wheel drive applications.

In theory, if the bolt pattern, Offset were the same shouldn't they work in a RWD application as well?

chris94SCmt
07-01-2002, 08:21 PM
yes they technically can. The tbird offset wheel is really a fwd offset


chris

AV8R040
07-02-2002, 03:12 AM
The reason they are advertised as FWD is to say that they will clear the brake calipers on FWD cars. The RWD wheels will not fit on a FWD car but the FWD wheels should fit a RWD as long as the offset is the same and the bolt pattern fits.

dode
07-02-2002, 11:03 AM
Ok...FWD cars use a different kinpin and wheel offset combination to achieve a much different scrub radius than a RWD car. Most FWD cars run a negative scrub radius (or sometimes 0), while most RWD cars run a positive scrub radius. It is NOT recommended to mismatch them, even if you can get them to fit. It can cause very poor handling and steering response characteristics.

John

Mike8675309
07-02-2002, 11:17 AM
I think of it as how the hub of the wheel mounts.

RWD wheels have the facing for the hub to mount towards the inside of the wheel. FWD wheels have the facing for the hub to mount towards the outside of the wheel. Notice in the pictures below where the weight of the car will be distributed to the wheels. FWD is towards the outside, RWD is towards the middle.


Note that someday, I would like to have some significantly wider wheels on my car. A bit of the muscle car look.

RWD:
http://www.pantherwheel.com/v1.1/Wheels/500x500/224.jpg
http://www.pantherwheel.com/v1.1/Wheels/500x500/new/208slm.jpg

FWD:

http://www.pantherwheel.com/v1.1/Wheels/500x500/new/250.jpg
http://www.pantherwheel.com/v1.1/Wheels/500x500/new/212.jpg

bagged89
07-08-2002, 01:43 AM
i have KMC wheels and mine are classified "FWD/Passenger car" I agree with the earlier post that our T-Bird wheels seem to have the charateristics of a front wheel drive wheel. My thought was it has to do with the offset of the wheel.

Deep6
07-11-2002, 08:24 PM
Sorry that I have not been able to respond to this thread for a couple of weeks, but I was unable to access the website.

It seems that there is some conflicting information here.

What I'm trying to find out is this, if I upgraded to 17"x7" or 17x8.5" rims with an offset of 39"mm (which I *think* is the stock SC offset) that should work as long as it was a 4.25" 5 lug bolt pattern??

Mike I see what you are saying about the way the "spokes" of the hub match up to either the middle of the centerline or the outer edge of the centerline.

I noticed that the stock SC rims, have the "spokes" set up similar to a front drive car.

Dode, mentioned the scrub radious and I don't know what this means, someone care to enlighten me? Will this be a problem for us?

I still don't even know if they offer these rims with the above bolt pattern and offset but I thought that centerline was able to customize some things.....

Mike8675309
07-12-2002, 11:45 AM
I wish I knew. Maybe someone has played with offsets to help you.

The big difference with "rwd" vs "fwd" wheels is that on rear wheel drive cars, the axles tend to be shorter and place the hub right at the wheel wheel. FWD cars tend to have longer axles and the hub is near the outside of the wheel well.

It's a suspension design issue. Some day I'll do enough research to understand the math that goes into such decisions. The built in deflection of the suspension plays a large role in how the car handles. If you relocate the center of the contact patch of the tire, it can change the behavior of the suspension. deflection toe-in can change. Camber can change.

Unfortunately, it's likely to be something people will need to experiment with to get right.

dode
07-12-2002, 02:29 PM
Ok...visualize the car looking at it from the front. Draw a line through the upper and lower pivot points of the contol arms at the spindle and continue this line all the way to the ground. Now, remember where the point contacts the ground, and put the wheel back on the car. Now, take the centerline of the tire patch and measure the distance from that centerline to the point on the ground previously mentioned. This distance is known as the scrub radius. If the point on the ground is away from the center line of the car in relation to the centerline of the tread patch, this is known as a negative scrub radius, which is how FWD cars are designed for the most part. Now if that point on the ground lies between the centerline of the car and the centerline of the tread patch, this is known as a positive scrub radius, and is how a majority of RWD cars are designed.

When selecting a wheel, you want to maintain the cars original scrub radius, if at all possible (unless you really know what you are doing and are very well versed in suspension theory). Small changes will not make a huge difference, but whatever you do, DO NOT change a negative scrub radius to positive, or vice versa.

John