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Still trying to put a combination together. Do you use a rear swaybar with a panhard bar on the PM3L?
 

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You need some kind of lateral control mechanism. I suppose you could use a Watts, but then if you had the money for that you wouldn't be doing a Poor Man's 3 Link, would you? ;)

Whether you use a swaybar depends on your philosophy on spring rates. I'd bet that 99.9% of guys do use one.
 

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With a PM3L, you need a PHB or Watts to contol lateral movement; no choice on this. Whether you use a rear bar or not may depend on the PM3L design. Let's say you are using one stock upper with the rubber bushings. To some extent these will still add wheel rate from "bind" despite only controilling for/aft axle roll because the stock bushings are sill bonded to the sleave and the ends still bite into the mounts to prevent rotation. So you might get away with using a mild rear spring and no rear bar. On the other hand, if you are using a PM3L design similar to mine (rod-ends), there is no bind. You need higher rate springs just as you would with a T/A and you will need the rear bar. In my case, I'm using the MM adjustable bar in the .75" solid bar configuration. With .5" spacers in the rear and the wider front track from the use of the longer sn95 a-arms and the MM front bar (lower rate than stock), this rear bar on the lightest setting is nearly prefect with this set-up. I want to try one degree firmer to see if I can get the car to rotate a little better, but until I try that it's pretty good as is.
 

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Lateral location device, as said above, is under the "need" column. Without it, well, you won't have a working car.

I'm guessing a majority of people use some kind of rear bar, but nothing says you need to. Totally up to you. Stiffer springs are suggested though. I tried the PM3L with H&R Sport springs. Rode pretty nice but rolled like a pig. I was using the stock rear GT bar with it.

Do not use rubber bushings in the upper control arm. It, basically, doesn't work. Do what qtracer did and go heim joints on both ends of the control arm. I tried all new stock style rubber. No good.
 

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qtrracer, I forget if you told me this before and I can't find it in my PMs: Wasn't there a site you recommended buying the rear UCA spherical bearing and UCA from? It wasn't a "normal" site like MM or LMR, but instead was some guy who builds stuff for CMC/AI cars, iirc. I'm finally ready to go PM3L. Any advice appreciated.

Casey
 

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qtrracer, I forget if you told me this before and I can't find it in my PMs: Wasn't there a site you recommended buying the rear UCA spherical bearing and UCA from? It wasn't a "normal" site like MM or LMR, but instead was some guy who builds stuff for CMC/AI cars, iirc. I'm finally ready to go PM3L. Any advice appreciated.

Casey
Sent you a PM.
 

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Question for the PM3L auto-xers out there:

So, I now have 3 PM3L events under my belt. During my third one, which was this past Sunday, when I was off the gas, the car turned like a sumbitch (finally!). However, when on the gas and trying to turn, it didn't turn nearly as well. I didn't know why until a spectator told me that the car was picking up the inside front tire while accelerating out of corners (setup was different and tires were ####ty during first two events). Apparently, the onlookers were quite impressed by how hard the car was picking up the front tires! I clearly need to add more rear spring, right? Unfortunately, I failed to get video.

After the first 6 runs, I raised the PHB two notches, so about 3 inches?, to dial out some rear roll. My next run, after lunch, felt even better despite cold tires. Over the course of the next 4 runs, I dropped 1.5 seconds (80-second course for me) even though I had plateaued during the morning session and the car turned in like never before. Spectators said the car wasn't picking the front up as much after the bar change.

Car setup (front):
~3100 lbs. with me in it '92 notchback
8" 425# front coil overs
Koni yellow SA struts (set nearly at full soft)
~-3* camber
94-95 spindles
SN95 FCAs
small front sway bar (the blue bar, stock 4-banger bar?)
17*9s with old 255 BFG R1s (not ideal, just what I had lying around after my other old tires proved to be rocks. They turned out to be pretty darn grippy)

(rear):
350-390 H&R conventional TA springs
Koni yellow SA shocks (set nearly at full soft)
weight jacker rear LCAs
PM3L with passenger-side spherical-bushinged UCA
28mm hollow rear sway bar ('98 cobra)
Grigg's adjustable PHB, initially set at it's lowest setting
18*9s with old 285 Hoosier R6s (apparently mega grippy!)

Wheel rate calculations:
Front: ?? I can't find the foxbody with SN95 FCA wheel rate conversion %
Rear: 175-195

Suggestions on new rear spring rate? Other suggestions?

Thanks,

Casey
 

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Less front spring? That's crazy talk! hehe

I used to have 300# springs up front but those got sold when I got the 425#s. I don't really drive the car on Boston's streets anymore, so I was planning on sticking with big springs/small bar up front.

I'm hoping Jack can tell us what the fox with SN95 FCA coilover wheel rate conversion % is so that we can bench race some spring rates. For the life of me, I can't find that rate anywhere but I know he posted it somewhere in the past.
 

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Well, here's the thing about the SN control arms. The conventional spring is located pretty much in the same place as a Fox control arm. The difference in length is from there out to the ball joint. Since the motion ratio is partially derived the SAI, the angle of the strut will have a bearing. For bench racing purposes, I'd use the Fox conversion factor of 25% conventional to 90% C/O; the longer arm may give you a different ratio but not by much.

Even here, your front springs are way mismatched to the rear assuming the PM3L yields a similar result as a TA. I get F: 382#.5; R: 182# (avg of the range). That's 200#s difference. Reduce the front rate, increase the rear rate and maybe adjust the balance with a bar? I imagine the ride is not pretty.

On my 86, I was having some serious snap over-steer with H&R Super Race conventionals (260-300 static; 140# avg range) in the rear with my PM3L and 300# C/Os in front (270#). 130# difference. When I went to the T/A I left the same spring combo and still had the problem. I went up to the same entry level T/A springs as you (182# avg; 88# difference) and moved my rear bar up one tighter. Problem nearly solved. And the car rides a bunch better due I think to the better resonance match. MM tech (not Jack) said I need th higher rate T/A conventionals, but thought I'd play with rear bar settings first.
 

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Did you ever play around with anti-squat brackets on yours? I'm debating having some ala Mathis fabbed up since I can't seem to find any reasonablly priced ones for sale for foxes. I am assuming that the S197 units from Whiteline won't work.
 

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Okay, next question, (since the last one got such an overwhelming response):

What would you say the ballpark wheel rate difference should be for a PM3L auto-x mustang? I think I've seen the number +100# front vs. rear thrown around on c-c before.

IF that is a good place to start, then I may be looking at stepping down the front springs to 375 and upping the rears to the 415-515 TA springs. Pro) This puts the front spring at the upper edge of what MM says is the range for a Koni SA sport, which I have on the car now. Con) I have to buy two sets of springs (although not terribly expensive, especially if I buy used).

Alternate option is to keep the 425s up front and bump up the rears to a 250# rear coil over (or find a 550# rear conventional spring). Con) Fronts remain, according to MM, outside the best range for Koni SA yellows. Con) Unsure if rear Koni SA yellows can handle that much wheel rate (I would assume so but MM's guide is blank for this line item). Con [if applicable]) Rear koni coil over conversion more expensive, harder to find used.

Thoughts, please?
 

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Sorry - been trying to get the 86 ready for a Sunday event.

Nope - never played with anti-squat. The two designs I favor don't consider this an issue for open track. KB has the bracket as does the Mathis design. But I'm not sure what advantage this would provide given the stress on the longer mount.

As for spring rates, keep in mind that the MM advice and the stuff discussed on C-C.com is for a F/R C/O set-up, not F C/O R conventional. With that said, you can look at the 100# spread and convert it to account for the conventional spring location. Example: F-300# C/O (270# wheel rate); R - 200# C/O (240# wheel rate). Spread = 30# To get a similar spread with a conventional rear spring would require a rate of just under 500# (500# conventional = a WR of 250#). This is the approach I'm taking.

Also, MM sells a kit that allows one to use C/O springs in the conventional rear spring location. Might be a lot cheaper to go that route - at least initially - than the other options.
 

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Thanks for the reply, I appreciate it. I wish more of the PM3L people posted as much as you do, just so we had more data.

Re: anti-squat, thanks for pointing out the KB pieces; not sure how I didn't find those during previous searches before (weak Google-fu).

What I'd really love to know is, given that the anti-squat % of a PM3L is the exact same as for a quadra-bind, if raising the anti-squat would affect the optimum wheel rate differential balance. I.E., assuming the 100# wheel rate difference front to rear is the correct starting point that I am thinking I've heard before, would anti-squat brackets change that to 125? 150? 50? Darius indicated that he ditched his brackets on his TA-equipped the car after it became oversteer happy. That, to me, would indicate that perhaps they would work with softer rear spring rates. Would love to hear Darius' thoughts on this.

Should I still need to go with a much stiffer rear spring, in order to keep the 425s, it will probably be very difficult to find a rear conventional spring that goes higher than the 415-515 I've found. That one would average a wheel rate of 233 when, assuming a 100# split f/r, I'd need 283. Thus, to keep the 425s, I'd need to find something in the 550-575 convention range. While it would most certainly be ALOT easier to find coil over springs in the 550-575 range, I think I'd prefer to just try to find a used Koni coil over setup via c-c instead of messing with the coil springs in a stock location conversion.

It's never easy, heh.

The good news is that the current setup is at least moving in the correct direction. During my first auto-x of the year (big front bar, small rear bar, ####ty tires), I was 13% slower than my bench mark, Cmasy from c-c in his z06. Yes, 13%. I was DFL against miatas and vettes on an 80-second course :(. DFL I expected, just not by that much. At event #2, I added more negative camber to the front and reduced the gap to 12%, heh. Still DFL. At event 3 (small front bar, big rear bar, new rear LCAs, better tires), the gap dropped to 9% (and I got 2nd-to-DFL, hah)! That's still an ass-whooping but his z06 is on those super sticky Contis and he's a great driver (every time I ride with him, I'm amazed at how small the corvette feels from the inside, it's such a damn go-kart when it has grip). I'm trying to decide what a realistic goal of % difference should be so that I set realistic expectations for next year.

Thanks again.
 

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Thought I'd share my set-up with you. Still in the process of learning it and tuning it.

Car: 94 Mustang

Front:
Stock k-member and a-arms
H&R Super Race Springs (950-1050 lb/in)
Cobra Bilstein struts
V6 front sway bar
MM CC (-2.25* Camber, 4* Caster, slight toe out)

Rear:
MM Rear LCA
MM Panhard bar (bar is horizontal when car is stationary)
Passenger UCA with spherical bushing on axle side and urethane on body side (Driver UCA completely removed)
MM T/A Springs (375-440 lb/in)
MM valved Bilstein shocks
No rear sway bar

Tires:
Cobra 17x9 with NT-05

Been running this set-up all autocross season. Handles pretty well, I'm usually in the middle of the pack in raw time. Rear end still wants to step out on me some. Biggest plan for next year is some better tires (maybe the ZII's). Also contemplating running a larger front bar and adding the V6 rear bar back on.
 

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5 0. The F/R spring rates appear pretty well balanced. I found on my 86 that I had to run more rear bar to avoid some front push (my front springs are 300# C/O -270# wheel rate; your w/r is about 250). My front rate was not well matched to my rear (H&R Super Race w/r of about 140; more than 130#s difference while yours is about 40# difference).

If your rear is stepping out, I'd look at the poly chassis bushing. I suspect some bind at the limit. I was running all rod ends on my PM3L and didn't have a rear end issue; was always a front push issue.
 

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5 0. The F/R spring rates appear pretty well balanced. I found on my 86 that I had to run more rear bar to avoid some front push (my front springs are 300# C/O -270# wheel rate; your w/r is about 250). My front rate was not well matched to my rear (H&R Super Race w/r of about 140; more than 130#s difference while yours is about 40# difference).

If your rear is stepping out, I'd look at the poly chassis bushing. I suspect some bind at the limit. I was running all rod ends on my PM3L and didn't have a rear end issue; was always a front push issue.
Thanks. I tried to do as much research as I could beforehand. I haven't calculated the wheel rates, good to know they are well matched. I'll double check my chassis bushing.

I think my main issue are the tires, the NT05s are done (2 years of autocross with 2 drivers). Trying to just finish out the season and get driving experience.
 

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What I'd really love to know is, given that the anti-squat % of a PM3L is the exact same as for a quadra-bind, if raising the anti-squat would affect the optimum wheel rate differential balance. I.E., assuming the 100# wheel rate difference front to rear is the correct starting point that I am thinking I've heard before, would anti-squat brackets change that to 125? 150? 50? Darius indicated that he ditched his brackets on his TA-equipped the car after it became oversteer happy. That, to me, would indicate that perhaps they would work with softer rear spring rates. Would love to hear Darius' thoughts on this.
Jack, Darius, any thoughts? I've purchased 375s to lower the front wheel rate and am still debating the merits of running the anti-squat brackets with the softer H&R 51650 RTA3 350-390# rear springs vs. just running the MM 43TA7 415-515# rear springs.

With the 375s and RTA3s, wheel rate difference front to rear is 152.5. That would drop to 105 with the 43TA7s.

TIA.

Casey
 

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For those that have used the pm3l how much noise does it transmit? I picked up a dead stock 96 GT and threw on a panhard bar, TA springs, UPR upper diff mount and have tried both an old HPR upper and a stock upper and I hear a lot of thumping and straining.
 
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