Looking for some good suspension threads

Hasbro

Hasbro

True Classic
I've been reading up quite a bit on here and elsewhere (no books yet) since joining and would like to find some more info re. suspension mods leaning towards the more in depth and technical for the X1/9 specifically. I'm sure there's more stuff but can't seem to find it. (1)Topics such as developing a performance suspension, affects of track width changes and how the scrub radius is affected etc. I'm not that savvy with the engineering but it really intrigues me and want to have a lot of knowledge before taking the plunge.
(2)Also, how the weight of motor swaps affect handling and what is done to adjust to the changes.
The info doesn't need to be specific such as for autox or roadracing, anything that I can learn from is all good.
My mid engine background has been with British cars (Europa, Esprit).
Thanks!
 
Hasbro...

Go here...

http://pbseng.com/FIATX-19.html

... Purchase their book if ya really wanna go EXOTIC. They have drawings and all to make up your own suspension pieces that include changing the entire geometry. Not for the novice... but a great read.

Otherwise... some good struts, tires, cut down or performance springs and the stock suspension performs great... and for some, FANTASTIC, as it is. There may be some anti-roll bars out there also, but in most cases they are not needed or required.

Have fun.
 
Head on over to http://www.mr2oc.com/ Yes it is an MR2 board and you may need to register but there is an excellent writeup on suspension written by one of our own, Steve H. aka XHead, who has won multiple championships in an X1/9. The article talks MR2 but the info applies to an X as well. Look under the Auto-X forum for the threads titled "STS2 MK1 suspension setup w/host XHead" there is a part 1 and 2. Then come back here and do a search on suspension and you can read much debate regarding different setups. Enjoy!
 
spiggs said:
Head on over to http://www.mr2oc.com/ Yes it is an MR2 board and you may need to register but there is an excellent writeup on suspension written by one of our own, Steve H. aka XHead, who has won multiple championships in an X1/9.
Click to expand...

Thanks for posting that. Yes, the writeup talks MR2s but based more on X1/9 data and testing that MR2s. In fact, I was wondering if it wasn't a good idea to post it here directly?

Yes, the MR2 data applies directly to the X1/9, or more correctly, the X1/9 data applies directly to the MR2. So it would be a great document to post here.

And if you have any questions about the write up, post them here.
 
The MR2 thread

Steve - If its OK with you I will volunteer to compile those threads into something we could post here then update as the MR2 threads are updated with new info. Before I post it I can run it by you to make sure I captured everything relevant and you could add comment as needed, however you want to work it. Let me know.

Vince
 
spiggs said:
Steve - If its OK with you I will volunteer to compile those threads into something we could post here then update as the MR2 threads are updated with new info. Before I post it I can run it by you to make sure I captured everything relevant and you could add comment as needed, however you want to work it. Let me know.
Click to expand...

Thanks Vince. I was in the process of making a post that asked the question of how to copy an entire thread from another forum. That's no small thread so it wouldn't be as simple as "copy and paste".

You have my permission to have at it.
 
Well, I'm going through Steve's two threads and have already learned a few things that aren't mentioned in my chassis books.

Part 1: http://www.mr2oc.com/showthread.php?t=298272

Part 2: http://www.mr2oc.com/showthread.php?t=313691

Just ordered the PBS book. They have 29 left at $20 including shipping and won't be publishing any more as the last printer lost the artwork.
The PBS guy suggested that someone buy them all and sell them on EBay. The book is about 20 years old. Thanks for everyone's input.
 
Ok I will bite

I finally read the Mr2 post and I have a question, where did this come from?

"Back to determining total roll rates. I noted I had a simple formula for a starting point. That formula is: ½ the total vehicle weight divided by the inverse of the weight distribution. An example for a 2200 lbs car with 44/56 front to rear weight distribution (a rough estimate of your car's weight and distribution):

2200 / 2 = 1100 lbs

1100 * .56 = 616 lbs/in front wheel rate

1100 * .44 = 484 lbs/in rear wheel rate

The reason for inversing the weight ratio is to offset the car’s rear weight bias"

Maybe this is some index that Steve uses but I have never seen anything like that. In fact, the math seems very strange to me. Please educate me on this one.

For example wheel rates are calculated by the following:

The X is 41/59 bias so for 2200lbs the front is (2200*0.41) 902lbs and the rear calcs out to be 1298lbs breaking it down further for each corner is 451lb front and 649lb rear.

The calc for the front is:

fnf=0.159(RRf*g/W)^1/2
Therefore
(fnf/0.159)^2=RRf*g/W
RRf = W/g(fnf/0.159)^2

**Assume the wheel frequency (fnf) is 2.5hz for a race car

Rrf = 451lb/386in/s^2*(2.5/0.159)2 = 288.85lb/in (front)
Rrr= 649lb/386in/s^2*(2.5/0.159)2 = 415.66lb/in (rear)

So again please educate me on this.
 
Well, I am not sure what you don't understand about my math. I don't think I could have made it any more clear. Its just simple math. The method is one I developed myself. It is quick and easy way of figuring approximate wheel rates for most any racecar to achieve a reasonable balance.

You appear to have assumed that I was trying to achieve a typical ride frequency of 2.5 for each end of the car. I was not. In fact, calculating ride frequencies for each end of the car never figure into this process. Other than using the weight of the car as a starting point.

The wheel rates you figured using 2.5 as the ride frequency would result in a car with excessive oversteer. Incidentally, I used the weight distribution of the MR2, not the X1/9. The weight distribution for my DSP X1/9 was 46/54.

If you read the entire thread you will quickly realize that I do not follow conventional wisdom. I even state as much in the thread. My methods are wholely my own. I am quite familiar with most of the commonly accepted engineering principles and methods. I have studied them. I went my own direction. The results speak for themselves.
 
Yes the math is simple I really meant logic; I don't get your logic. I can't argue an index you developed for your use. You are right that I did not read on, I could not get past your index calc. I just did not understand it. I tried to figure out why you would arbitrarily break the car in to two equal parts 50/50 and then multiply the front by the rear weight bias and visa versa. Great points concerning conventional wisdom and results, F1, GT1, GT2, OE, etc, designers all use conventional wisdom to design winning vehicles. I bring these points up so those who are seeking knowledge not only appreciate your insight but also the true science of dynamics and suspension design.

Recommended reading for those interested "Fundamentals of Vehicle Dynamics" by Thomas D. Gillespie (a Society of Automotive Engineering book)
 
Dallarax19 said:
Yes the math is simple I really meant logic; I don't get your logic. I can't argue an index you developed for your use. You are right that I did not read on, I could not get past your index calc. I just did not understand it. I tried to figure out why you would arbitrarily break the car in to two equal parts 50/50 and then multiply the front by the rear weight bias and visa versa.
Click to expand...


That's not really an accurate description of the index. The roll rates are the inverse of the weight distribution. Basically, take the corner weights, and swap them front to rear.

Dallarax19 said:
Great points concerning conventional wisdom and results, F1, GT1, GT2, OE, etc, designers all use conventional wisdom to design winning vehicles. I bring these points up so those who are seeking knowledge not only appreciate your insight but also the true science of dynamics and suspension design.
Click to expand...
Dallarax19 said:
]
Click to expand...

If you do some in depth research into current methodology in F1, LMP and even NASCAR you will find out that some of that same thinking is going into those cars now too. I have been developing this method for about 15 years now.

Dallarax19 said:
Recommended reading for those interested "Fundamentals of Vehicle Dynamics" by Thomas D. Gillespie (a Society of Automotive Engineering book)
Click to expand...

As I noted previously, I have studied the subject extensively. I understand the accepted engineering principles. I know how and why they work. I learned a lot from studing them. I also know how and why my methods work.

I also know, from spending a lot of time talking with some very good race engineers, that as a driver, I think differently about how the car works and why. You will note that in the thread on the MR2 forum, I never consider the ride frequency, the favored speed or center of suspension. I am only concerned with front to rear roll ratios and weight distribution.

Incidentally, if you read my post on the '09 Rolex24you will know I was the chassis engineer for one of the top placing GT Porsches. I was probably the only chassis engineer at that race without an engineering degree. (I studied Finance and Marketing)

I have always been one to go my own way. But being different isn't the motivation. I know that nobody ever distinguished themself by being a sheep and following the crowd.

I would be glad to discuss my methods and the thinking behind them further if you are interested. There is a lot of thought behind them.
 
I finally got a chance to catch up. Well, we can do the tit for tat thing but I can tell you that with 100% certainty the F1, OE, Nascar, etc engineers do not use the Steve index or anything with like the rational - 100% Confident. I take exception that you refer yourself as an engineer. I don't know your background but from your jargon etc I am very confident you are not an engineer. I have the luxury of access to many experts in the vehicle dynamics field and at least once a week talk with an ex Benetton F1 suspension guy. I was reviewing the new Pratt and Miller GT2 car last week and got to see several new ideas, once again I can assure you the Steve Index was not used. If someone asks for your set up that is cool but when you start to profess engineering and higher order dynamics I think you need to be clear about what is your opinion and what is as you call it "conventional wisdom".

It is slow going but I am working on an updated state space model of the X - I did a simple "bicycle" model as my vehicle dynamics thesis 14yrs ago. This is a simple simulation model solving simultaneous equations with matrix mathematics, partial differentials etc. I have to admit that I need Matlab to do the symbolic math today because I am out of practice. When complete I will also model your set up as I know it for comparison. That may be worth discussion when the data and results are put together. For grins, in the mean time, if you have not got the Rfactor Dallara car you should give it a try. It is very accurate as to how my car handles. The fastest setups are "conventional wisdom".
 
Dallarax19 said:
I finally got a chance to catch up. Well, we can do the tit for tat thing but I can tell you that with 100% certainty the F1, OE, Nascar, etc engineers do not use the Steve index or anything with like the rational - 100% Confident.
Click to expand...

I never claimed they used my "index" (your word, not mine). I referred to the fact that from talking with a number of engineers of prototype and F1 teams, including the technical director of Jaguar F1, I know that some of my ideas turned up independantly in those cars. I didn't identify what those ideas were.


Dallarax19 said:
I take exception that you refer yourself as an engineer.
Click to expand...

I have never claimed to be an engineer. Ever. I studied Finance and Marketing. But I have read and studied the subject for more than 20 years.

The team I crewed for gave me the roll of engineer within the team. They did not grant me a diploma.

Because I am not an engineer, I don't think like an engineer and am not constrained by the principles that engineers typically limit themselves to. I am well aquainted with how engineers think as I worked with them daily for more than 20 years. I also know that just because I don't have an engineering degree doesn't mean my ideas are not valid. As I said previously, I earned my position with those teams and the results speak for themselves.

If you read the thread you will find that I state in the thread that the "index" (as you call it) is a simple rule of thumb or seat of the pants method to get you close on the setup. I also stated that I don't use that method to setup my racecar today. I use Susprog3d. But I still use my own ideas and the 'no swaybar' setup.

If you dissagree with my methods, you don't have to use them. Set your car up the way you want. I do find it interesting that you dismiss my ideas without having tried them. I have tried the conventional wisdom and know that my methods have consistantly produced better results.
 
What constitutes an Engineer

ISN'T AN ENGINEERING DEGREE. Those who disagree are likely those who have engineering degrees. I work among those with 'engineering degrees' that have difficulties tying their own shoes. When I read about those who challenge the engineering skills of others, it turns me off completely.

'I'm more credible than you because I'm an engineer and you're not' -Bulls:censored:t!

There are those who think like an Engineer, and there are those who don't. I've read enough on this board over the years to know who thinks and writes like an engineer. Whether (or not!) he wants to consider himself 'within the klan' of engineering, Steve H. IS every bit an engineer and has a history to prove so. He is no more and no less perfect than any other so-called 'engineer' I've read about on this forum. Steve has a time-tested history here, but you sir, DO NOT.

Maybe you should worry about your own 'credentials', and leave judgment to the readers.

My :2c: FWIW.
 
Can't remeber where I heard this, but "In theory, there is no difference between theory and practice. In practice there is." Seems kind of appropriate.

Dallarax19, no need to attack anyone here.

Mac, do we have access to an "ignore" list on this forum?
 
Ok, mandatory "take a breath"...

Hi everyone.

Good conversation, but lets be careful as we are walking very close to the line of good conversation vs. unpleasent ones.

Here is what I can tell you from my experience on this. I run a partial Steve setup on my car. Just haven't made the full jump into a toe out setup on the rear yet! For what it is worth, I am faster with a partial setup vs the standard toe in rear toe out front setup.

Now, I also know of a couple of other people who run very fast cars and swear by this setup as well.

Give it a try and see what you think. On a correctly prepared car, it should take you an afternoon to swap things around and get it setup. The hard part is when you are in a corner and understeer is beginning to happen, conventional wisdom says you should keep even gas or even back off slightly. With Steve's setup, you put your foot into it and the car goes around the corner.

Maybe we should setup up a car with the conventional setup, run some laps, then change it over to Steve's setup and run some laps. It would be fun to see the difference.

Eric Armstrong
 
Some good discussion in the mix and some not, Just for clarity I have tried swapping the spring rates etc early on as a student engineer in a Design Of Experiments fashion to understand the impact. I am a data guy and I don't speak out of school - no pun intended. My trials may not be your exact spring rate selection but the principles are still there - firm front/soft rear/bars/no bars. Yes these days I do it by simulation. In my experiments I found the set ups where you have a high spring rate in the front to grossly under-steer in both the entry and excessively at the exit of the apex - on throttle lift of the front and loss of steering. I am not looking to create a big stir but I want everyone to be honest. Just for reference I have "practiced" at the local race tracks for 19 years now, Waterford Hills, Gingerman, and Gratten (I also ran my 87 MR2 at Waterford too so I have an idea how that ran). I had made a go of it in the autocross circuits for two years with the SCCA too before I could afford to go to the tracks. To assume I have not practiced what I preach in not correct - just wanted to be clear on that. I think both points are pretty clear on this post so it is probably best to move on to other things.
 
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