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I tend to agree with you. If we look at the wins at the Solo National Finals in my class(CP) I think Strut cars have won 7 out of the last 10 but I only think 1 of those was a third gen camaro, the rest where in Mustangs. The other 3 wins where with cars that have fully scienced out SLA suspensions. Not bad in a class that is supposed to be full on race cars and is really a testiment as to how well strut cars can actually work.
Welcome to the party Big, I cant validate your chart but it is impressive.
I noticed though a "problem" with the camber curve's on the chart though that is typical of a strut. It's most obvious on the "lowered 2" curve, at about 2 1/2" compression the curve essentialy flattens out. Thats where the inside edge of the out side tire begins to lift and cost traction.
The rebound curve wich will be effecting the inboard tire is better but since the load is concentrated on the out side tire camber under compression is whats most important.
the adjustable balljoints in the links should help out because with a significantly lower car (2+ inches) the stock balljoint is definitely stealing camber at 2 1/2" compression.
I also agree that the F body package is really very good. Thats why I'm not going extreme with this project. I'd proabably be the only one to use it and my car is definitely not going to be a full on race car.
Last year i was asked on a Mazda forum if a Mazda MX-3 could be made competitive in national solo racing and I responded that the car is very well engeneered light weight and nimble and it's a great platform to start with.
Another member chimed in and said that NO strut car could EVER compete with a double wish bone Honda. I feel that is complete ignorance, though the class the OP was interested in was proabably 90% Honda and he would be a true underdog for many reasons ( and many seasons the truth is that if you only placed 5th you still beat a dozen or more of the supposedly un-touchable Hondas out there.
1st and second gen RX7's are proven winners with struts as well as the smaller BMW's and 924/944 Porsches among others.
It's also worth noting that the "ideal" camber curve can change due to many factors, mostly roll resistance and tire dimentions and construction.
Wider tires and lower profile tires each are more sensitive to too much or too little camber. If you have camber issues and you cant do any radical suspension work and dont want to give up tread width you can try stepping up your sidewall a bit and/or use a tire with a less rigid sidewall.
The extra compliance can help keep tread on the ground and inprove overall traction.
I know the AutoX mentality is to have the shortest stiffest sidewall possible for better response and I dont want to start an arguement (again) but response issues can be resolved with the driver tweaking his style a bit.
the adjustable balljoints in the links should help out because with a significantly lower car (2+ inches) the stock balljoint is definitely stealing camber at 2 1/2" compression.
That’s exactly why I put in the "raised 1" curve. That would be stock ride height with a 1" drop on the mono ball joint. Or for example, "lowered 1" could be a 2" drop with 1" from the suspension and 1" from the mono ball joint.
Was wondering about that! I just figured you were grtting into rallyX lol.
But a1" lift isnt the same as a 1" baljoint drop, it adds in the effect of the strut starting in a different position where the uniball on a stock ride height carwould have a slightly inverse effect on the curve.
Was wondering about that! I just figured you were grtting into rallyX lol.
But a1" lift isnt the same as a 1" baljoint drop, it adds in the effect of the strut starting in a different position where the uniball on a stock ride height carwould have a slightly inverse effect on the curve.
No, the strut would compressed 1" shorter. The pivot points remain in the same spots (BJ, strut bearing in shock tower, and LCA pivots) so the geometry remains the same.
But you need to realise that raising the car 1" extents the strut by 1", as you can see in your own chart the camber changes with bith compression and droop.
The strut ads it's own peculiar aspect to the camber curve so any change in it's static state will effect the static camber and the entire curve, just the movement of the balljoint dose not change the position of the strut or it's movement at all where as a 1" raise would have the same effect on the balljoint position in addition to the change in the strut position and geometry.
You could thereticaly re set the alignement using basic alignment tools but unless you took that into consideration with your model then the 1" raised curve is invalid as anything other than a refference. But as it is ats a great tool for observing the effects ofa wide range of motions being imparted to the suspension.
Ok, I think might see where there is some confusion.
I assumed that the alignment was always set to -.5 deg at ride height for each curve. You could change this to 0, -1.5, or whatever you want. It would effect the camber curve a little bit, but I had to baseline it somehow. I did this because I was trying to look at it from the point of view that the suspension will spend most of its time at static camber and bumps and body roll with cause it to move up and down from there.
The way you are looking at it you could just look at the stock curve and ignore the rest. If you lower the car 1” using springs and do not touch the alignment your static camber would be about -1.25 deg, for example.
Thanks - that was a Lot of info - I'm glad you noticed that post with that dumb title
anyway -
using the 2D design software I had to lower the lower control pivot point about 1.5 inches to get good camber curves and consistent roll center height (about 4 inches above ground)
for antidive the frame is already angled upwardly toward the front where I mounted the upper arms - it can be calculated and shock settings, weight and other things have an affect on it - so I went with the frame angle
I set caster to 10 degrees - now theres slightly more space ahead of the tire than behind looking at the fender
I couldn't weld a caliper bracket to the B-body spindles I started with so I used the
C4s which changed my design with respecgt to the vehicle height and tire size because of the change in the upper and lower ball joints and spindle center line spacing
Last thing my tie rod are at kinda of a large angle - seems ok so far - but the Type 2 PW pump, under drive pulleys and those 275/35/18 makes it tough to steer
I'll post the 2D lay out I settled on and camber curves fyi
That exactly what I was talking about but I would probably still use the factory spring pocket and an externally mounted shock(since I have a weight jack in the way) like we used to do on our dirt track cars. Coilovers like on Mell's car also look like a good option and if I did that then I would run them from the Lower A-arm through the upper arm up to mounts on the cage. It would mean a lot of redisign on my part to go coilovers for very little if any improvement. The only reason I would have used G-body spindle is I still have stock brakes so it would be a bolt on deal and they work fine for autocross. Going with the Vette parts would make it easy to go with the vette brakes so that looks like a real good option.
Right Height Left Height
A 24 20.5 UBJ 24 20.5 G
B 17 19.75 UFP 17 19.75 H
C 28.37 7 LBJ 28.37 7 I
D 11.65 7 LFP 11.65 7 J
E 21.5 18.75 USP 21.5 18.75 K
F 25.37 7 LSP 25.37 7 L
right and left distances are from the car center line – lower frame pivot (LFP) is the difference between the front the rear bushing distance from the centerline since they are not equidistant from the centerline
Upper arm dimension calculated
Length 7.04 – angle 6.12
Lower arm dimension calculated
Length 16.81 – angle 0
C4 spindle info:
Hub distance 3.75 - horizontal distance between the center of the lower ball joint to the wheel mounting surface
5.875 in distance between upper ball joint and center of the rotor
7.5 in distance between lower ball joint and center of the rotor
Spindle angle 16 deg
Track 60.7
Scrub radius -.3
Roll center height 1.6
Camber gain -.59deg at 1 in dive; -1.01deg at 1.5 in; -1.5 deg at 2 in
Roll camber change shows the loaded tire losing camber at 0 degrees dive
.74 deg at 1 deg roll; 1.41 at 2 deg; 2 at 3 deg
and the unloaded tire gaining camber at 0 degrees dive
-.82 deg at 1 deg roll; -1.72 deg at 2 deg; -2.7 deg at 3deg
Static camber is 1deg
That software was helpful ($80 back in 2003) since I didnt intend to keep any stock susp parts-
hth
oh and finally found a pic of a 4th front end.
i was wandering around a junkyard and looking at one while thinking about this thread. the 4th gen upper arm, just bolts to the strut mount and uses the long upper ball joint mount. since most of us, or atleast me. have conveted to 4th gen front brakes anyways, wouldn't finding a way make an upper tie into the bottom of the strut mount like the 4th gens, and use their spindle be a pretty easy/good idea? it would also make swapping to a steering rack easier.
or does this type of upper a arm being so far up there, have some camber side effects that make it not worth while?
Well by my reconing if everything is the same raising the upper arm reduces camber gain for a given compression, that means that the upper arm either needs to be shorter or have a steeper angle at static ride height to compensate.
I also believe that having the arms so far apart reduces slop in the suspension due to bushing and arm deflection compared to a traditional setup without resorting to harder bushings or more rigid and thus expensive to manufacture control arms.
As far as instaling the 4th gen spindle with upper arm the main problem I encountered was 1 the upper ball joint and the related areas of the suspension would hit the underside of the stock 3rd gen strut tower, you can see where the 4th gen tower is formed to allow the suspension to clear the structure. This is evident on many other cars as well like SLA Hondas and Mitsubishis/Chryslers.
A rack or a custom set of steering links would be needed also since the 4th gen spindles have shorter steering arms and would introduce a host of bump steer and roll steer issues.
For someone willing to cut up their car it wouldnt be the most dificult job though.
I'm on my way to a basic prototype setup as we speak It'll look almost production btw so dont get freaked if I post pics of a 16 ga sheet metal origami looking thing!
Since I have constrained my self to the space available I'll have to build it to fit first then go about insuring improved geometry and such.
I suspect I'll have to resort to lowering the LCA like Mell did in order to control the wild camber gain I might be looking at, if I'm lucky I can do this with off set bushings like are available for my Mazda.
The 5th gen was almost an after thought and is based on an Australian family sedan, just like the 1st and 2nd gens and even the 3rd gen to an extent the 5th gen is based on current conventional technology.
Designing a whole new front end just for the F body would have the car priced nearer the Vette and Viper except it would still have a family sedan's fairly basic IRS compared to the expensive space consuming and very effective rear ends used in those cars. on the back burner is a plan to swap the rear from a final gen GTO (or Caddy Cattera) into a 3rd or 4th gen to compliment the SLA front.
Well by my reconing if everything is the same raising the upper arm reduces camber gain for a given compression, that means that the upper arm either needs to be shorter or have a steeper angle at static ride height to compensate.
Sounds about right. These tweaks also affect lateral tire scrub as well (Marks' "Standard Handbook for Mechanical Engineers" even has a sketch and brief discussion about this specific item).
Quote:
I also believe that having the arms so far apart reduces slop in the suspension due to bushing and arm deflection compared to a traditional setup without resorting to harder bushings or more rigid and thus expensive to manufacture control arms.
Loads applied to the basic chassis structure also tend to go down with a tall knuckle design. On the other hand, deflection in the knuckle itself tends to increase and clearance issues around the top of the tire may limit the wheel sizing in some ways. Seems like there's always going to be a little give-and-take.
Norm
Last edited by Norm Peterson; 10-30-2009 at 07:03 AM.
The scrub radius is unaffected by the upper arm, the only things that dictate scrub radius are kingpin inclination (steering axis angle), wheel diameter and offset w a given size hub and spindle snout. Basically it's the result of where the kingpin axis intersects ground level and where the wheel centerline intersects ground level. The distance between the 2 is the scrub radius.
That lateral tire scrub is almost completely the result of the effective horizontal lower control arm component changing length when the arm swings around. It's obviously longest when the arm is horizontal from bushing centerline to balljoint center. A longer lower control arm will have less change here. Longer lower control arm = less balljoint angularity.
Fabbing a longer LCA has been on my mind but I have been trying to avoid that for cast reasons, especialy since the suspension will retain the stock spring location and proabably use a shock in the same location. The LCA would need to be quite strong and resistant to fatigue.
What many people dont realise is that while the tubular components they can buy from various vendors are stiffer and lighter than the OE stamped parts they replace the fatigue life of many of those components may not be near what you see in the OE stampings. For all their flexability they are usualy very resiliant and rigid tubular replacements will tend to crack and fail outright rather than bend.
For a coil over car like my mazda i wouldnt have any problem fabbing a light tubular piece as there is little bending pressure being applied but for our style suspensions a lot of attention needs to be paid to how the stresses imposed by the spring and or shock are handeled.
The bending force entirely depends on where your coilover or our spring is mounted, not familiar with your mazda but if the coil over is mounted close to the balljoint for a closer spring/shock to wheel ratio relationship then yes,that would be true.
the truth is that if you only placed 5th you still beat a dozen or more of the supposedly un-touchable Hondas out there.
This is pretty much what we were talking about rayar. 
