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Suspension tuning books

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#1
I want to learn more about suspension tuning so I thought a convenient way to do that would be to read a book. Anyone know of any good suspension tuning books?
 


RAAMaudio

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#4
My books are a bit old and packed up for moving but the one I found is still great.

Chassis Engineering by Herb Adams.

I have an even better one as it covers FWD setup, I think by Carrol Smith.

A couple of sites with good info if you dig into them.

http://www.improvedtouring.com/forums/

Great article here:

http://farnorthracing.com/autocross_secrets10.html

Toe out, FWD, page 2.

http://www.motoiq.com/MagazineArticles/ID/1936/The-Ultimate-Guide-to-Suspension-and-Handling-Part-Seven--Tuning-your-Toe.aspx

Further on it takes about toe in on the rear, which I removed from my car as well as added more camber, it was a BIG project.
 


BRGT350

1000 Post Club
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#5
Anything by Carroll Smith is worth getting. Fred Puhn's "How to make your car handle" is another good read on the basics. While these are not Fiesta specific, they go in depth about the reasons why your car handles the way it does and what changes to the suspension affect handling.
 


OP
G
Messages
70
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11
Location
Bury St.Edmunds
Thread Starter #6
Mike kojimas article series ultimate suspension guide is a very informative read

My books are a bit old and packed up for moving but the one I found is still great.

Chassis Engineering by Herb Adams.

I have an even better one as it covers FWD setup, I think by Carrol Smith.

A couple of sites with good info if you dig into them.

http://www.improvedtouring.com/forums/

Great article here:

http://farnorthracing.com/autocross_secrets10.html

Toe out, FWD, page 2.

http://www.motoiq.com/MagazineArticles/ID/1936/The-Ultimate-Guide-to-Suspension-and-Handling-Part-Seven--Tuning-your-Toe.aspx

Further on it takes about toe in on the rear, which I removed from my car as well as added more camber, it was a BIG project.
 


RAAMaudio

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#8
2005 Scion TC, TT, autocross, street, highly built car and very good at everything, fast enough to take second place in a national TT race I would of won the second day but blew the engine due to a bad tune.



As an experiment I lowered the ride height by 1/4" all around lower than the optimum I had calculated after drawing out the whole cars geometry in full scale on the shop wall. I had already been racing it setup exactly where it should of been which was only moderately lowered over stock.

I did this to prove a point in a debate online as well as just see if I could tell much difference. The results were far more than expected, it changed the roll couple by a great deal and put the roll center under ground. The only other change was a minor toe adjustment.

I went out for the 20 minute session and the car just did not stick like it did before, my best lap time was just about 2 seconds slower which is significant in racing but also the car was far more work to drive, less confidence inspiring, twitchy....

I raised it back up during the break, set the toe(everything was pre marked so it was really easy to do this) double checked everything.

Next session out I was right back at my normal lap times and the car was hugely easier to drive at the limit, which also means safer.

In this particular situation once going past the optimal ride height the changes in roll center and couple were very dramatic, on the other cars I have setup it was less so but still considerable. I cringe when I see overly lowered cars as I know what it is doing to the handling, I know most have not done anything to correct the geometry and likely have other compromises.

Of course a car can be lowered more if we change the pickup points on the suspension, which I have done, inboard and or outboard depending on parts available, room to make changes inboard, rules, etc.....

-----------------------

The simplest way to make sure your car is not to low is to ensure the center of the ball joint is lower than the center of the inboard pickup point on the control arm which is all I have done on the FiST so far and the car is amazing in the corners. (Of course I have done many other setup changes that adds to the handling but this simple step is easy and free and very important)
 


OP
G
Messages
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Location
Bury St.Edmunds
Thread Starter #9
So how much lower is the ball joint to the control arm pick up points on your fist? I need to adjust my ride height to be higher. After reading Kojima's articles I know I gotta raise it. I was gonna have the rear about a cm higher than the front.

I noticed due to the McPherson strut characteristic of more suspension compression=more positive camber I was riding on the sidewalks of my oem tires. May be weak side walls or too low ride height or over driving. Camber is at -2 degrees. I did order Dunlop direzza dz2 star specs 215/40 r17s for stickier tires.

Last weekend's track day I rode along in a gentleman's turbo mk1 mx-5 and he had extreme summer tires and the speed, control and grip he had in the corners was amazing. I understand the mx-5 has wishbone suspension all around but it inspired me to take my fiesta's handling to a higher level.

2005 Scion TC, TT, autocross, street, highly built car and very good at everything, fast enough to take second place in a national TT race I would of won the second day but blew the engine due to a bad tune.



As an experiment I lowered the ride height by 1/4" all around lower than the optimum I had calculated after drawing out the whole cars geometry in full scale on the shop wall. I had already been racing it setup exactly where it should of been which was only moderately lowered over stock.

I did this to prove a point in a debate online as well as just see if I could tell much difference. The results were far more than expected, it changed the roll couple by a great deal and put the roll center under ground. The only other change was a minor toe adjustment.

I went out for the 20 minute session and the car just did not stick like it did before, my best lap time was just about 2 seconds slower which is significant in racing but also the car was far more work to drive, less confidence inspiring, twitchy....

I raised it back up during the break, set the toe(everything was pre marked so it was really easy to do this) double checked everything.

Next session out I was right back at my normal lap times and the car was hugely easier to drive at the limit, which also means safer.

In this particular situation once going past the optimal ride height the changes in roll center and couple were very dramatic, on the other cars I have setup it was less so but still considerable. I cringe when I see overly lowered cars as I know what it is doing to the handling, I know most have not done anything to correct the geometry and likely have other compromises.

Of course a car can be lowered more if we change the pickup points on the suspension, which I have done, inboard and or outboard depending on parts available, room to make changes inboard, rules, etc.....

-----------------------

The simplest way to make sure your car is not to low is to ensure the center of the ball joint is lower than the center of the inboard pickup point on the control arm which is all I have done on the FiST so far and the car is amazing in the corners. (Of course I have done many other setup changes that adds to the handling but this simple step is easy and free and very important)
 


RAAMaudio

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#11
I set the ride height quite some time ago and do not recall as it was not meant to be permanent, just a starting point, it is probably 1/4" or less lower.

It is a bit tricky determining the exact center of the ball joint, best to take a wheel off and look at the top and bottom and then mark what looks to be the center. To be more precise I will remove the knuckle from the control arm and then move the joint around to get a better visual of the center. Then mark it on the outside where I can see it the best and using a straight edge, square, etc I can measure it better once back together, the wheel is back on and the car on the ground and been rolled around.

Then inner pickup is easier, the center of the bolt but also the center of the rear mount as well so get the best you can on that and split the difference for inboard.

Instead of being absolutely accurate, which is not easy, it is pretty easy to just be lower on the outside than the front and knowing it is going to be close to optimal and only a bit of fine tuning would be left that should not make a huge difference.

Almost always on all cars we want the front lower than the rear, eventually I will get to that as well when I do a very accurate setup which includes using the scales, jacking a side of the car, getting the true CG, front and rear roll centers, etc..............I might even want the rear even or slightly lower to keep more weight on the back of the car, something I have never done before but I always have an open mind and test all I can.

For now:
Front
Front camber is -2.5, adjusted at the top of the struts, would of used the knuckle mounts but the wheels and tires are two close.
Stock castor, I have ran more positive on FWD with good results but I had more rubber on the ground, 265 slicks, lower CG, wider track, same weight car.
1/8" toe out
Rear
-1.9 camber
0.0 toe
Slightly higher, around 10mm ride height

With approx 210WHP, 225 slicks on 15x9 wheels, stock front sway bar with stiffer bushings and Steeda adjustable end links, no rear bar, all urethane bushings(ordered race grade, received street grade and no time to wait for them to manufacture the right ones I installed them and am fine with them)
My own BBK fornt and rear, carbotech XP12/8 pads. I was 5 seconds a lap faster than the national champ spec miata, I may have more power, they weigh less and as we all know are incredible handling cars. Even the pro race driver/instructors were quite amazed at my lap times and the car was very easy to drive all out which I was and beyond, purposely over driving it to shake out any issues and see what happens if I blow it, MMP is a safe track to find the weak points, I found none, car was incredible and only issue after two days of pounding over the curbs, etc.....lost 2 PSI in one tire.

This is my third FWD project car, first was the first turbo 1ZZ Matrix in the world, 250whp on a simple turbo with a simple 5th injector tune and far fewer mods and less chassis to start with, second fastest SM car in SoCal, that is saying a great deal!

Second was the TC, better chassis, IRS, foam filled chassis, CF roof, caged, 250lbs lighter than stock, 265 tires, far more mods than the Matrix, national classTT performance.

Now the FiST, best chassis, coolest looking, most fun, in many ways my favorite car ever:)
 


RAAMaudio

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#12
Sway bars are the last step in setting up a suspension properly, why mine is at is is for now and quite good.
I have a 5-way rear bar I modded, lots of work, I can install for testing but so far have not felt I needed it, I had a massive rear bar on the tC but it also had IRS, no front bar, incredibly fast in all turns.

After reading the Kojima articles and another one I found I am going to look into a bit more front sway bar, normally I have just not seemed to need one but it might help keep the rear inside wheel down but to much bar can result in less grip when accelerating out of a corner.

I am going to disconnect the front bar and have some pictures taken hooked up and disconnected to see just what happens in the rear and then determine if I want to try a stiffer front bar.

If I recall the stock none ST bar is a bit stiffer, I might get one to test, probably a pain to swap like most FWD cars are.

If you even loosen the subframe you need to ensure it is bolted back up exactly where it was, as long as it was known to be correct in the first place. This is not easy to do so best to mark it really well before dropping it, I have had to redo a great deal of work when in a rush and forgot to ensure it was correctly positioned after changing engine mounts on a Vetter, hours of added work in fact and not easy as doing the alignment on the ground.

(Note: on the tC I had issues with the ABS freaking out and losing the brakes on some autocross courses so I removed it entirely to save some weight. Then I had an issue with locking up the inside rear tire on road race tracks while in the air and flat spotting the tire when it came back down. I was going to reinstall the ABS and test it again on road courses but first was going to do some more spring rate and sway bar testing. The ABS on the ST is working just fine on track:)
 


RAAMaudio

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#13
Alignment things to check, even if not adjustable we need to ensure none are way off and I have seen factory parts that were, my rear axle was off a bit.
Front camber, toe and castor
Rear camber, toe
Front cross member to chassis
THRUST ANGLE, rear axle to front axle, not mentioned often which is odd as very very important

It was relatively easy to adjust on my Vettes, on the ST the mounting points for the beam angle have a little play, if not enough the mounting brackets to the chassis would have to be slotted a bit more.

I use a DIY string gauge with just jack stands, etc....I set the rear tow with toe plates then check the thrust angle which is just a line from the rear tires to the front to ensure they aim straight ahead. Run the line across the front and rear of the tire wall, center height, just touching both surfaces, forward to the front tire, past it to a jack stand to wind it around and move back and forth until the rear is setup right. Measure the distance to the center of the front axle, dust cap, etc, each side if the tire, they should be as perfectly the same as possible.
 


RAAMaudio

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#14
I know I have upset at least one if not a few others on this forum with my posts about setting up a car for real performance over looks but I know the real difference is vastly more critical than some seem to be willing to consider.

Taken to the extreme, not compensated for, overly lowered, far to much camber, far to wide wheels with super narrow tires, very limited contact patch, improper wheel offsets, compromised suspension travel, overly stressed ball joints, bushings, mounting points, all in the opposite direction of making a car handle properly.....taking an incredible car like the FiST and turning it into a parking lot attention getter with severely compromised handling is simply incomprehensible to me.

OK off the soap box, I am very glad most of us here are wise enough to know the truth and strive to make out great cars even better:)
 


OP
G
Messages
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Location
Bury St.Edmunds
Thread Starter #15
So regarding the rear springs and damper, how do I properly raise the rear ride height? Having the spring perch adjustable and the separate damper length adjustable and lining them up
 


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