My Car So Far...

Oh boy... this will probably need more time than I have right now to respond. I'll try to give you the basics and will follow up asap.

There are two basic applications; street car and track car. Their preferred setups are at odds and compromises often make them bad at both. I have written in the previous version of this forum extensively about this very subject. In fact, it was my Championship DSP X1/9 that launched my career in Motorsport. The car taught me a lot about vehicle dynamics and setup. It was my laboratory where I could play Dr. Frankenstein and suffer my own failures.

It all comes down to two basic components; ride frequency and roll ratio, which tend to be at odds when applying them to the two applications.

For reference I will define a few terms:

Ride frequency is the time measurement of the vehicle's ability to recover from hitting a bump. That is; the suspension/chassis's cycle time. A soft ride frequency is typically about 1 Hz (1 cycle per second) and provides for a smooth ride quality. A high frequency is over 2 or even 3 Hz (2 or 3 cycles per second).

Wheel rate is the spring rate times the suspension's motion ratio. For example: if the wheel moves 2 inches for every 1 inch of spring movement the motion ratio is 2:1. So (spring rate) x (motion ratio) = (wheel rate). The reason wheel rate is important is wheel rate is the effective spring rate for setting up the chassis.

Roll Ratio is the comparison of front and rear wheel rates. In your case the front spring is 425 lbs/in and the rear is 400 lbs/inch. Sadly, I long ago lost my spread sheet that had the X1/9 motion ratios in it and I don't remember them off the top of my head but they are pretty close (which is typical of a strut car). So we will just use spring rates for now. Given your existing spring rates your roll ratio [(Front Rate) / (Rear Rate) = Roll Ratio] 425/400 = 1.0625 I will discuss how that ratio affects the car's handling later on.

Favored Speed is the speed at which the car would have to be traveling for the front suspension and rear suspension to recover at the same point in time after hitting a bump. This is the application of ride frequency in determining ride quality. Very simply, you want the vehicle's "favored speed", the speed at which is rides most comfortably, to be a a typical cruising speed.

Center of Suspension is the point on the car's chassis, between the front and rear axles, where if you were to place a vertical load the suspension would compress the same on both ends.

More to follow.
 
Steve please keep going I know its a lot to type out, but Im very interested in this topic. For spring rates and suspension setup this is a great convo to have

Im not looking for perfection here, I dont have the time or money to achieve it so realistic goals are what Im after. Im well aware of the effort and $ it takes to get those last few tenths.

For the front I was really looking for practical advice on things to look out for while taking apart and putting back the front suspension. To me it looks much easier than the rear but you know theres always those little logistical things you learn taking things apart and back together a couple times that might be good to know before doing it.

After I get everything back together I will be referencing this info and prob asking some more questions about settings so again its still a valuable convo to have and much appreciated!
 
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A car's handling balance, between understeer and oversteer, is determined by roll ratio. Rear wheel drive performance cars will typically want a F/R roll ratio of between 1.25 and 1.5 to 1. That is; the front wheel rate is 1.25 to 1.5 times the rear wheel rate. Typically, a rear weight bias car (mid or rear engine location) will be toward the higher end of the spectrum. For the X1/9 we will assume a 1.5:1 roll ratio. So for your 400 lbs/in rear springs you would need a 600 lbs/in front spring to yield the 1.5:1 roll ratio we would target. This is a pretty standard track/autocross setup for a typical X1/9. However, the ride qualities resulting from the very high spring rates, especially in front, will result in unacceptable ride characteristics on the street. We will return to roll ratio a little later.

For a typical enthusiast street car a ride frequency in the range of 1.5 Hz provides for a good balance of ride and handling. To achieve that the spring rates need to suit the weight carried on each end of the car. You can then see that the X1/9, being considerably lighter in front, would need a lighter front spring rate to achieve the desired ride frequency. This is at odds with the preferred roll ratio we noted previously. To resolve this issue for your street car a front swaybar can be utilized. A swaybar (or anti-roll bar) is only engaged when the chassis rolls thus we decouple the ride and roll functions, the swaybar's wheel rate only employed in roll. This permits a softer front spring and thus a smoother ride while maintaining the required wheel rate for handling balance in roll.

Favored speed is a calculation of ride frequencies at a given speed. To achieve the ideal ride for the desired speed (say 75 mph) the spring rates need to be offset somewhat from the original 1.5 Hz ride frequency. I tend to prefer stiffening the rear slightly to achieve this, rather than softening the front. A note on favored speed: Perhaps you have driven a car, probably a good European GT, that seemed to get better the faster you went. The car just seemed to settle in at say, 80~85 mph, and had a very stable and confident ride at that speed. This is the result of a well tuned 'favored speed', as well as other parameters like alignment and shock valving.
 
Steve please keep going I know its a lot to type out, but Im very interested in this topic. For spring rates and suspension setup this is a great convo to have

Im not looking for perfection here, I dont have the time or money to achieve it so realistic goals are what Im after. Im well aware of the effort and $ it takes to get those last few tenths.

For the front I was really looking for practical advice on things to look out for while taking apart and putting back the front suspension. To me it looks much easier than the rear but you know theres always those little logistical things you learn taking things apart and back together a couple times that might be good to know before doing it.

After I get everything back together I will be referencing this info and prob asking some more questions about settings so again its still a valuable convo to have and much appreciated!


For freshening the front suspension its not much different that the rear. Inspect the bushings and mounts. The radius arm mounts (on the body) can get bent as well as their mounting locations. So be sure they are in good order. A bent mount or mounting pad will result in offset caster and cause the car to pull one direction. Also make sure the radius arms are true as they can get bent themselves. The radius arm bushings are replaceable and there is a little plastic insert for the mount that locates the arm and its sleeve where it passes through the mount. Be sure to replace these as well.

The front control arm has an integrated bushing. They can be replaced but because the ball joint is not independently replaceable just replace the whole control arm. Note that the radius arm is hard mounted to the control arm. This requires the control arm bushing to twist as the suspension is compressed. So Poly Bushings here are not ideal.

I also advise replacing the steering rack mounting bushings. They are often over looked but are easy to replace, as is the rack bushing itself. And of course inspect the inner and outer tie rod ends.

And as on all X1/9's (front and rear) check the strut turrets (top mounts) to ensure they are flat. They are often mushroomed from bottoming. Be sure to inspect the top mount bolt holes for cracking and weld up any you find.

Also, the project X1/9 book is available as a downloadable .pdf so there is no real need to buy it. It is fun to look at but there really isn't much relevant for most applications today.
 
If I have enough funds left over I will replace the whole rack as they are surprisingly cheap and do the bushes as well
 
I haven't looked for new racks. If you happen to have some links to good sources for new ones at decent prices, please post them.
 
Vick auto has / had them . Don’t come with rod ends , Mount bushings or jam nuts. Very reasonable for brand new , IMO. Still haven’t installed mine yet, so can’t comment beyond that.
 
Finished boxing in the other control arm. Then I attacked any rust and weakened paint with a pnuematic wire brushing. I then degreased and washed everything. Dont worry I sealed off the ball joints. In the time it took to dry in the California sun they started to rust again literally before my eyes. No joke. So I used a rust transformer primer

58FB47FA-5A91-4B0C-963D-8F583509FF37.jpeg


And then flat black

F00FDA9B-125D-492E-977C-F8B4FC6723EA.jpeg
 
Prep work takes a ridiculous amount of time but by painting things I can be assured that they will rust in a slower fasion and come apart easier when I go back later on. Plus it looks nice

Also its a good way to visually keep track of what has been touched and what still needs doin
 
Agree, I'm the same way. Spend more time cleaning and refinishing every part than actually doing the repair that prompted it.
 
Prep work is always the biggest time pit. Even building transmissions. I spend more time cleaning and prepping the cases and parts than I do actually building.
 
Ben

Thanks for picturing your spare ride behind the control arms. It may be a good idea to put back a seat on the bicycle... You may find the work on the Fiat could take more time than expected. Listen to the guy who started working on his engine 18 years ago and end-up buying another Fiat in between. :D
 
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Also as Im having PM convos with people and if youve paypaled me you might realize Ben Louis is an avatar name and Im starting to feel weird being called Ben. But I feel like you guys are cool so Ill clue you into my secret identity my name is actually Blake
 
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Things like that happen a lot. For example there is a member who registered with a 'phrase' that includes a common name, and it is often thought that is his name. Or another who's son registered and we all thought the father's name was the son's. And "Daniel Forest" is actually "Forrest Gump". Point is we are just trying to be friendly by using peoples real names rather than user-names. Hope you weren't offended by anyone's misunderstanding. By the way, I think "Ben Dover" would be a better fictitious user name (say it quickly out loud). :)
 
Things like that happen a lot. For example there is a member who registered with a 'phrase' that includes a common name, and it is often thought that is his name. Or another who's son registered and we all thought the father's name was the son's. And "Daniel Forest" is actually "Forrest Gump". Point is we are just trying to be friendly by using peoples real names rather than user-names. Hope you weren't offended by anyone's misunderstanding. By the way, I think "Ben Dover" would be a better fictitious user name (say it quickly out loud). :)


Ha. I was never a fan of avatars. This is me.

Hey, I am off working for the next several days. Will get back to this when I get home early next week.
 
How about Paul Mike Hawk?
Try saying that one fast

No not offended at all it just got to the point where I was like who is this Ben guy? Oh yeah duh its me

Ive been saving this one good user name for when I actually get this thing smogged and can get a specialty plate with the same. No spoilers but I bet youll be like dang I wish I thought of that
 
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