AWD car, do FWD knuckles have better geometry?

[bigfoot]

I've read this several times and I'd like to nail it down. Will using FWD front knuckles improve AWD handling? What are the differences if any? I've searched several boards on this but came up blank everytime.

 

[ACM]

2G uprights are the same part #, so no difference would be experienced.

1Gs do have different part #s so assuming everything bolts up, you may get different geometry.

No experience with 1Gs, but I can move around CAPS handily

Charles

 

[SlowSpyder]

so far this is what ive seen. for both 1g's and 2g's the knuckles are basically the same for both fwd and awd with the exception of the wheel speed sensor(whether the car has abs or not)

 

[bigfoot]

Here's a cut and paste from my alignment guy explaining it to me. I don't think he understands capital letters yet.

"i'm not too sure about the FWD knuckles. just what i read on the net. and yes, less scrub radius means better turn in. when camber changes under dynamic load(cornering) your toe will change to a positive position / \ because of the lengths of the tie rod. from what i gather, the FWD steering arm on the knuckle is set further out from the rack which reduces the toe change during camber change. you could also try positive toe in the back. fwd cars usually use negative toe in the front due to the forces put upon the front suspension during acceleration."


So after finding out that RRE used to sell these as a 1G AWD upgrade I emailed them and asked about the knuckle differences and handling results. I told him of the smaller scrub radius rumor. Mike at RREs response didn't give any specifics, all he said was that they improve the handling on a lowered car. Less bump steer if I read my alignment guy right.

The wheel sensors on a 1G are on the hub just behind the rotor. Some non abs hubs have the mounting holes for the rings, just no rings. The knuckles are the same as far as ABS unless they are just missing the mounting point of the magnetic reader.

 

[lbartik]

Here is a derivational approach to answering this question by analyzing the geometry rather than third party advice. Hope it isn't going to lead anyone astray if they were all wrong...

http://www.galantvr4.org/ubbthreads...pe=&olderval=&oldertype=&bodyprev=#Post164272

 

[Todd TCE]

There are no known differences from where I sit.
One has an axle in it, the other does not.
Cross part numbers both new and at the junk yards pan out.

And just stop to ask yourself what the expense would be for a 'new' part in this manner as a manufacture. It simply wouldn't be cost effective to do.

Perhaps what you are thinking is that someone has made changes to the steering arm or tie rod with regard to lowering the car and getting bumpsteer back into spec?

 

[n2o4fun]

Different PN in CAPS for a FWD vs. AWD. The mystery continues?!

 

[jtmcinder]

Not true. Only the shocks and springs have different part numbers. The knuckle and control arms and hubs are the same numbers because they are the same parts.

You do realize that we're talking about 2Gs, right?

- Jtoby

 

[lbartik]

Not true. Only the shocks and springs have different part numbers. The knuckle and control arms and hubs are the same numbers because they are the same parts.

You do realize that we're talking about 2Gs, right?

- Jtoby

I don't know about that, the thread starter appears to have 1g car as most of his posts pertain to 1g issues. (ie. hotbits coilovers for 1g...) It is settled. One post does mention 2g uprights, another wayward soul. To clear things up however, there are two (left) front knuckles for 1g era cars:

MB518137 cross-references to the following platforms: D21A(1g 1.8l) D22A(1g 2.0 FWD) E33A(~89? - 92 Galant 2.0L FWD [same body style as the VR-4)


MB518227 cross references with E39A(Galant VR-4 AWD turbo) E38A(Galant GSX AWD) and D27A (1g DSM AWD)

So you can see that there might be differences in geometry as people who've held both in hand have pointed out. Some have even put them on their cars and measured with a (Hunter) alignment rack for geometry differences...

 

[n2o4fun]

So you can see that there might be differences in geometry as people who've held both in hand have pointed out. Some have even put them on their cars and measured with a (Hunter) alignment rack for geometry differences...

I wish people would stop beating around the bush and just post the difference's if they know what they are. This Secret Squirrel stuff is getting old.

 

[lbartik]

I think you've misinterpreted my thoughts. Man those elipses can get you in some trouble on this board. Look at my post count, I've not been here long enough to get all proprietary about these matters and I don't have any competitive motives. I simply do not know what the numeric differences are as I did not perform these measurements.

Here you go, I'll quote the material I linked to in the begining with the stipulation that this info was not provided by my measurement though he sounds quite certain of himself:
-----------------------------------------------------------------
This is what you should find, and it is not conjecture:

The steering rack tie rod end mounting location is:
22 mm higher on AWD than fwd
4 mm inboard on AWD than fwd.

Reasons? Not entirely sure, but AWD (TEL) has higher ride height, and shorter steering rack stroke to avoid contact with the large Auto trans.

The same differences apply to Galant. E38 and E39 use AWD knuckle, E33 uses fwd type.
-----------------------------------------------------------------

I assume that he means 4mm (inboard) toward the strut axis or shortening of the effective steering arm on the knuckls as opposed to 4mm toward the centerline of the car.

And so, the info was there all along.

 

[pneumo]

I was doing some work on my two DSM's lately and I was able to take some pics of the 1G FWD and AWD steering knuckles. Unfortunately my internet connection has been very erratic and I can't post the pics!

So anyway, I hope my words are good enough for now. I'll try to add the pics later.

The steering rack on the AWD car is raised up about 1.5" to make room for the transfer case, so the place where the tie rod ends attach on the steering knuckle are also raised up. I guess this keeps the tie rods level for good steering geometry. If a car was lowered enough the tie rods would be angled up. I could see how a lowered car might get some bump steer, and that FWD knuckles on an AWD car would help.

But I wonder if some people might like having a bit of Ackerman?

 

[n2o4fun]

I would love a little positive Ackerman in my 1G. What do you know?

 

[pneumo]

ah yeah!

 

[pneumo]

Ok so after waiting about an hour for a good connection I finally got the pics uploaded! The first one is FWD, the second is AWD. I was carefull to take both pics at the same level so the differences would be obvious.

Ackerman, as I understand it, is the tendency for the front wheels to toe-out during a turn. It's generally a good thing for fast cornering, but too much can give the car some bump steer. It looks like Mitsu engineers decided that bump steer was a bad thing for the general public, so they tuned out most of the bump steer, and the Ackerman along with it. Simple geometry shows how a lowered car will get some bumpsteer and Ackerman at the same time.

I also took a look at the angle of the tie rod while I was taking the pics. On a stock, unlowered car the tie rod has a very slight upward angle as it goes from the rack to the steering knuckle. A lowered car has more of an angle. When you hit a bump the wheel goes up, and the tie rod gets even more of an angle. Here's an exaggerated example \___/ that's sort of what the steering rack (middle flat part) and both tierods look like. As the wheel travels farther up from a bump the tie rod swings inward slightly and steers the wheel out. While the other wheel, the one that didn't hit a bump, maintains it's position.

When cornering, the outside wheel gains most of the toe out, while the inside wheel levels out the tie rod, resulting in a slight ammount of toe in. Taken together, in a corner the outside wheel gains slightly more toe out than the inside wheel gains toe in. It may not be much, but it's better than nothing.

 

[bjones18]

Ackerman, bumpsteer, roll steer.

Read some books:
1. How to make your car handle, Fred Puhn.
2. Tune to Win, Carroll Smith
3. Tires, Suspension, and Handling, John, Dixon
4. Race Car Vehicle Dynamics, Milliken
5. Vehicle Dynamics, Thomas Gillespie
6. Understanding Vehicle Roll Behavior, SAE paper Robert Jones

Bolting on a different knuckle is like installing a different camshaft...don't do it because someone said so. It is part of a system. What are you trying to accomplish?

Raising the outer tie-rod end is similar to lowering the steering gear, or rocking the subframe in side view. It will change roll steer.

Have you measured your roll steer to see what you have F/R?

Race cars have used "anti-ackerman" to equalize slip angles; do you want more ackerman? It is a system: everything affects something else.

 

[bigfoot]

6. Understanding Vehicle Roll Behavior, SAE paper Robert Jones

Would this be anyone you know?