Traction Bars
 

So, looking forward to a built motor project, I see wheel hop as a major issue. It was an issue n/a, it was a big issue when I ran a 13.1@110 and it will most likely be a major issue once I am finding the limits of my disco potato. I saw a while back where TravisR was talking about fabrication traction bars but I couldnt find much else on the subject. I have never been able to break my 60ft times out of the 2 second range due to wheel hop and it is killing my ET's.

My question is, how hard are they (traction bars) to fabricate and can these really be universal?

"Fits cars and mini-trucks with leaf springs under the axle "

im not sure how you do traction bars on an independent multilink suspension... but that's not it

might require a minor conversion to your rear axle. :giggle:

seriously though, I think the traction/slapper bar is a solution for a problem a miata will never have. since the diff is rigidly attached to the PPF and tranny, the diff cant "wind up" like a muscle car.

Those in your link are for cars with leaf springs. Won't work on a wishbone setup.

FWIW, I had terrible wheel hop. Always have. When I pulled the engine to turbo, I found my drivers side motor mount was broken in half. Switched it to the passengers side as that one was only slightly torn. :) So now I have a torn drivers side and broken passengers side. Made a big difference in wheel hop. I will 100% be buying some stiff ass motor mounts soon, and diff mounts too.

As for traction bars, I think Travis is working on some. If you want to build your own, get on m.net and search through the V8 section. There's a few guys there that have built some and reported good results with V8 power.

Awesome. Thanks guys. I have a couple of connections with some good fabricators so I may do some research with the v8 guys and see if we can come up with a working solution.

I'm hoping to get my car out of storage and into the shop to build some traction bar jigs. It is one of the main business lines for ETD (Welcome to ETDRacing.com 2.0) and therefore we would love to make some for the Miata also.

Well, as I've found out more about this, I read a couple of SAE research articles on it, read a book about it (carols), and I really don't think traction bars are the answer for an IRS. What you have to do is put a comprehensive kit together that works on alot of little things in the rear to kill the big problem. Traction bars will always degrade turning performance on an IRS suspension, and they have to be very carefully placed if you do use them on any car or you'll completely bind your suspension. So while you can bolt up a set of universal bars, they really arn't what you need, and you have to crunch alot of numbers to get any positive effect at all.

i have never thought about it, but i have the MMR motor mounts only and i have NEVER had ANY wheelhop. so that makes sense

we just need something to hold the diff in place, it is winding up because its not hard mounted to anything. When I went from rubber to poly diff mounts it REALLY helped, I get very little wheel hop now where as I used to get it ALL THE TIME.

that and making sure your shocks are not blown lol.

I am just about to put in some solidish diff mounts in - the MS engine mounts help I'm sure.

I thought the question was more a diff brace - something to grab the front and keep it from moving. that seems like it might be useful?

Thats one of the things I"ve got in my kit. Thats a big key. Can't do a whole lot with the pumpkin floating up and down back there.

On my 99' the tire will move forward over an inch on a hard launch. That's not just the diff winding up.....

Thats a part not the whole thing ;)

Good lord!

On my tires, the car stays still, and so do the wheels. :-)

Where's this Kit, Travis? :-) Linkage!

How the hell did you find that out?

Havent I seen a bar out there that bolts to the lower 2 bolts on the housing, and run to the rear subframe or something? I cant recall exactly how it looked ,but do recall seeing it. Dont remember the maker either. I also have a good bit of hop, but havent really gotten to try it out since new engine mounts. My old ones were fully ripped in half, so Im guessing it should be MUCH better now. Plus all new suspension bushings, so maybe that contributes to less suspension flex in the rear. Diff mounts will come when I get the 3.6 gear set.

Also, anybody ever used those PPF braces Ive seen out there for sale? I cant see how this would improve things much, but Trackdog claims a decent improvement.

I watched my car do this while it was strapped down to a dyno. I was thinking either new rear control arms with heim joints or stiffer bushings would help out the most.

This brace?

Miata BeatRush P.P.F. Performance Bar 1990-1997

http://us.st12.yimg.com/us.st.yimg.c..._2035_40091005

When I launched hard in 1st gear on the nitrous at the 1/8 mile, I could hear my drivers side tire "rubbing" the car's fender. After the run I have cuts in said tire and a damaged inner fender metal. I beat it in with a hammer but it still rubs on a very hard launch with 225's.

The Beatrush PPF brace is a nice piece. Haven't been to the track since I installed it, so I don't know if it helps with wheel hop any...

Nope. Got one one mine. Its better but still wheel hoped enough at track last month to explode my $700 torsen :vash:

What about the AutoExe one??

http://img329.imageshack.us/img329/6...ybrace1kj7.jpg

I'd love to have that, but it wouldn't work with my exhaust.

That doe snot bolt to the PPF?

Not the same one, but I guess thats probably the same thing.

yeah - that's what I was thinking, a nice rear subframe brace, but it would work just as well on a front drive car. :-)

As to the beatrush... It's like trying to carry your luggage on the end of a 10 foot pole - you're pulling on it over a huge lever arm.


I would think even just a strap across the front of the dif would help, anything better would be huge. It would nearly be a flat bar across...

Er, something like this. You probably don't need the other bars. I wanted to make one "horizontal" across, but this does seem easier.

http://abefm.smugmug.com/photos/451300051_MANPY-O.png
edit: I weld as well as I photoshop

Not a single comment on this? I thought I'd draw the first thing which came to my head - and learn something when people shot it down. How far off the mark am I here? A flat bar with 4 holes drilled in it is a pretty reasonable fix, no?

Here is what id do for a no wheel hop car.

1) solid diff mounts
2) mazdaspeed motor mounts
3) poly suspension bushings on all the rear arms
4) a good shock/spring combo with somewhat stiff dampening
5) some sort of brace, like a beatrush/autoex hybrid

rubber diff mounts + solid diff mount = redundant vibration nightmare

My opinion is that brace your drew won't do anything to help with wheel hop.

The differential can move on 3 axis as well as rotate about any of these axis. Rotating about any of these axis is a problem (there could (are) be other things that cause it to hop, but we'll get to that). It "winds up" like a spring when it does.

Here's a pic with 3 axis and moments(torques) about these axis labeled. Green is the axis that goes across the width of the car. Teal is the one that goes front to back. And Blue is the one that goes up and down the height of the car.

Attachment 209121

Now if we were to brace the differential, our goal would be to prevent movement along and about these axis. So what movements does the brace in the picture prevent? Looks like it's trying to prevent any moments about Y and Z axis. However, it's a very poor design if they were trying to restrict moments about the X axis. The brace is hanging out way away from where it's fastened to the diff. If you think about it, it's like a weight hanging on the end of a pole. If you're the one holding the pole, and I add some weight to the end of it, you will have a very hard time holding the pole steady. Leverage working against you.

The brace does help to prevent moments about the Y and Z axis. However, movement about those axis isn't the "problem" IMO. When you load the differential, the front end (attached to the PPF) doesn't try to rotate about the Y or Z axis. It wants to go up, rotating about the X axis. That's why they put the PPF attached to that end.

A better brace would offer as much support as possible at the PPF to prevent these moments about the X axis.


Of course, that's only considering the differentials aspect to wheel hop. The actual hub that the wheel bolts to could (does) move as well when it hops. When you take off in 1st gear, you're putting around 1K ft*lbs of torque to the ground. Well, the hub tries to move forward.

Meh, more later.

Huh. I mean, you have the same logic as me, but you discussed the brace I called useless. The brace I "drew" just ties the front of the diff about your Y axis. Or tries to... And it has an extra "stick" I didn't erase, but I'm not sure it does much for you.



Matt: Vibrato-what? I was thinking you'd mount it similarly to the other diff mounts - a little play won't hurt, rubber mounting won't mean much - if the end of the diff moved 1/4" who cares - or are you saying with solid diff mounts, rubber mounting the end would cause MORE vibration than solid?

i meant that solid mounting the diff would suck for vibration and negate having rubber mounts in the first place. if you put that brace in, make some delrin or aluminum mounts for the diff ears.

I want to get my lathe going and make delrin bushings for everything. Almost bought a few sticks of Delrin this summer.

Attachment 209120

Already have delrin mounts for the diff. I would probably make the same for the brace if I made it.

The question, I thought, was simple - is that a light weight way to significantly improve the performance of the vehicle (comments on detraction from the comfort are also appreciated).


Certainly poly bushings is a good suggestion, one I've yet to take.

but you guys see how the PPF solidifies the diff, right? it's not going to pivot. the problem is more likely in the bushings in the suspension winding up.

Yeap. I'd want to make a pair of long arms that attach to the A-arms close to the hub area and run forward and bolt to a bracket that's welded to the frame rails. It would take the load off the A-arms when accelerating. More projects....

perfect.

You think the PPF does enough to hold it in the Z dimension (er, the y axis as we were talking earlier)?

holy shit, my car came with the autoexe or whatever. I thought it was stock but I guess its not

+1
Long arm to framerail to stop front to rear motion sounds promising.

BTW - This isn't the only independent rear car in the world. There must be an answer already.

I sure wish someone would Google that for me...


.

Love your avatar. :bowrofl:

I've searched so much on fixing wheel hop with an IRS suspension. What I said is what I found. Don't let the front of the diff move and put long arms to support the A-arms. A few V8 guys did the long arms on the A-arms and reported success. Another Just triangulated them from the A-arms back to the subframe. Not as optimal, but it didn't affect ground clearance doing it that way.

I doubt the diff pivots much at all. it's rigidly attached to the motor.

oh and for the record, YAW, PITCH, and ROLL are the words you want.

yaw is left to right like you steer

pitch is up and down like pat's signature pic

roll is side to side like when you have wimpy sway bars.

The only downside to the long arm is the front mounting point. As I discovered when installing Stein's framerail kit, the stock framerail is thin and soft. Maybe at the very back where it is reinforced.

Since my last post I have searched and only found the diff movement idea (which is not a problem for ours because of the torque arm between the diff and the trans/engine) and the need for less compliant A-arm bushings to disallow wind up. As you know, once there is wind up there is often a dramatic release.

The long arm helps to compensate (take the brunt of the force) for the softer stock bushings and I assume that is why it helps. Thoughts?

Edit: We have people who have noticed at least an inch of movement front to rear (I guess that is FORE and AFT :)) at the wheels.

fore and art, I love it. My car pulled hard to starboard till I evened out the tire pressure. But you're right, the terms are better than an arbitrary XYZ.

Anyway, how about a small shock absorber? Tie it to the front with a shock - so it pulls forward, fine, but then it won't HOP back.

I'd love to see a pic (pat or anyone) of this tieing the a-arm thing. I would guess something like solid bushings would help, at least getting the travel low enough...

BTW - FM's frame rail kit certainly helps a bit. :-) I took my butterfly off (left the rails) recently and the car feels noodley.

I suspect the PPF does alot of twisting and bending.

Interesting idea for a video shot.

While it wasn't IRS, my old '86 T-Bird Turbo Coupe had these small shock absorbers attached to brackets that stuck up from the ends of the rear axle. The dampers were mounted horizontally and the other end attached to the frame either in front of or behind the wheel (don't remember which way). I was told it was to avoid wheel hop caused by the large rubber bushings in the rear trailing arms.

Edit: found a link here -->http://www.foxthundercats.com/tctechhighlights.htm

Anyone try something like this out?

Mazda Performance Parts: Miata PPF Power Kit

Yeah, I can "see" exactly what would need to be fabbed to build a set of long arms. I have no cad skills though. I could draw them out on paper, but I have no dimensions to go by. I would basically build a bracket that I would weld to the frame rail. From it would hinge the long arm things that go to the bottom of the A-arms, directly under the hub. The piece that went on the A-arm would weld to the arm and then then you'd put the arm in and slide a bolt/bushing in. Both ends would be hinged basically.

Of course the problem is that now the A-arms want to move in an arc. However, I don't 'think' this is gonna be too significant. IE- how much suspension travel does a stock miata have from say normal ride height to the bump stops?

Or as someone suggested, a badass shock instead of an arm might would work. It would not limit the movement, just damp it to prevent an oscillation (wheel hop).

Yeah - the shock (awesome find) on the t-bird isn't really doing what we're talking about, though I suspect it helps anyway - it's keeping the whole axel/diff from rotating. Certainly that's what I was thinking with a shock - I don't care where the wheel is, I just don't want it to hop, and it's plenty compliant.

Why would you tie to the a-arm, and not the spindle/brake/etc? Something on the end of the travel, and even with the axel as much as possible? That is where the force is applied, restricting only one A-arm would help,but would potentially introduce a torque twisting the entire hub.

Pat, why don't you sketch up this picture?

Even though the hubs are not twisting at the ends of the control arms, it would dampen any fore-aft movement as well. I'm looking to see if they ever sold replacements for those things.

ideas.

I should point out that these below with the trailing link work because there are two bottom arms and they allow some amount of rotation as the wheel moves up and down. that means you replace the miata component with two arms with heim joints, not standard cylindrical bushings or you will bind.

http://www.hyundai.co.in/tucson/imag...neering/25.jpg

http://farm3.static.flickr.com/2143/...7ad48c2c8e.jpg

http://www.gtfours.co.uk/pics/suspension/205/005.jpg

http://www.gtfours.co.uk/pics/suspension/205/006.jpg

Yeah, I wasn't thinking about it twisting if I don't hold it from the hub. But I'm not sure that's doable either. IE-there's a lot of stuff there like a CV joint and shock. So not sure you could really mount a braket in there. And even then, I'm not sure you could get it to go down to clear everything and put your arm for support. Guess that's why I was shinking of just holding the bottom one.

I need a decent picture that shows the rear suspension and the frame rails to draw to. Searched and I don't have any pics like this, and haven't found any posted yet.

That 2nd pic that y8s posted looks like the rear suspension of an STI. I own a 2006 and I can tell you that it still wheelhops pretty bad sometimes.

Found some part numbers for those little dampers.
Monroe 32242
Koni Red 25-1215 $209.95/pair
KYB KG 4521 $ 79.95/pair

It was also stated in the Ford Mustang forums that the KYB's were much stiffer, and that cheap replacements were available for $25 from some discount parts places.

It still seems that the cause of the hop would be good to get down - is the wheel moving back and forth, are we just feeling the tire grip and relax, etc? Some high speed video of the rear wheels on a launch would be awesome. I never should have quit my job working for the high speed video camera guys. :-)

Still, I think I have something here at work which might be able to get at least a few hundred FPS, it probably doens't have to be the highest resolution. I'd have to think about it...

"The" two arms? You mean, these trailing arms we'd put in or?

A few hundred FPS would be PLENTY. Get to it Abe!

I wonder if you couldn't mount a camera to the car itself. I imagine a webcam would be too slow (though it's the lowest investment, and would follow the wheel). I should look around. And see if we still have the pco.1200

replace lower arm with two heim jointed links

We will be making Miata Traction bars very soon. I just need to find some time when the Hoist is not busy with a Honda getting Traction bars fabbed up for our new models.

Traction Bars is what we do... Checkout Http://www.etdracing.com (Parent company of M-Tuned.com).

Just need the hoist free and pull my miata out of storage.