Suspension tuning

[dav8427]

I threw this one out over at pt.com and didn't get any bites, anyone like to try over here?
Short of the obvious break in and 'make sure everything works right' cruise on a new design or unproven suspension set-up(both front and rear),Would there be a preferred order of tuning a new set up?Where would you start?
Where would you go from there?

Thanks, Doug

[novanutcase]

I'll say it again! Gentlemen?

[DFORCERRT]

Doug,
Well you have asked the "who's on first question" that needs some answers from you. What type of front and year suspension, shocks, springs, tires, wheels. But I'll give you some basics. Nut and bolt everything. The obvious is adjust camber, castor, bump steer, and toe being set for the application and assuming street use and tire width these might need to be adjsuted from "factory settings", but will be close. Corner weighting the car will optimize the balance of the car. Drive the car and note any bad habits, darting, excessive understeer/oversteer, brake dive, turn in transistion, and make adjustments one at a time to compensate. If you would like you can send me all your details and I would be happy to go over them and provide some more suggestions. Hope this helps,
Dave Force
Race Ready Technologies
610-889-1602

[dav8427]

Dave,
Front suspension is common un-equal length a-arms attached to B-body spindles,C4 Vette steering rack will be used.Rear suspension is un-equal length 4 link(non-parallel)with PHB.
Coil over shocks will be utilized on all 4 corners. Tires and rims will be conservative street size with decent street compounds.(no rubber band sidewalls)
Sway bars will be adjustable,either interchangeble or accommodations for moving sway bar for or aft and changing length of arms,not decided yet. Both the upper and lower control arms in the rear are adjustable +/- 1" from ride height at frame end and the PHB will be adjustable +/- 3" from ride height.
I am a ways off of that first drive yet, but would like to start making a 'check list' of sorts ahead of time.

Doug

[DFORCERRT]

Doug,
There are complete books on this subject but I'll hit some high points. Springs are used to support the weight of the car and to help remove slow transistions, shocks are high speed devices. A stiff ride is not necessarily a good handling car, especially in a street car. You want to rate the springs for the weight of the car and although adjustable shocks are nice be careful to make sure that they are adjusted to the same position on each end of the car. Spring rate/spring length and ride height all have to be considered when installing springs. To long a spring compressed for ride height no longer becomes a spring. To stiff a spring and you get a choppy ride. After setting ride height it's a good idea to get the car corner weighted to even each wheels load to optimize handling or at the very least make sure that the spring is compressed the same amount. Sway bars initial set should be with the car on the ground with no preload, driven and then adjusted for handling adjustments. Now if you live in a state that has perfectly smooth race track roads you can get a lot closer to race car setups but if you live in the Northeast where the roads stink I'll leave you with a very important thought- to many people setup their street car with race car suspensions that are set way to stiff with little compliance for street road variations, impresses those who don't have a clue, but doesn't give you a good handling car for the street. The secret to a good handling street car is keeping the tire in contact with the pavement, not skating over the top of bumps. Set your car up with this in mind and you'll have a car that handles great and provides a great ride. Hope this helps-
Dave Force
Race Ready Technologies

[dav8427]

Yes there are many good books and articles out there and I do try to read everything I come across.
For sake of discussion, I believe there is more real world experience out there that way out numbers the amount of good authors.
So hypothetically speaking,suppose a person has there rig handling pretty well.By that I mean it corners without being 'out of control', stays online in impromptu slaloms,and stops with authority.
When do you(or anyone else) decide that more anti-squat is needed or more rear steer,or to lower/raise the front/rear roll center heights,or swap front/rear sway bars, etc. etc. And which would you try first? Why?
Would it be more of a shot in the dark as to what steps to do before others or would you have to do one before the other. Then go back and do it all over again. Would trial and error with keeping good records of results be the 'best' option to weeding out the bugs of a new design?

Doug

[Marcus SC&C]

Doug,you`re on the right track. Keep reading and use all the info you can find to get the baseline setup in the ball park. You didn`t mention what kind of car it is but you should be able to find somewhat similar cars to backup at least some of your conclusions if you look. Then test and tune. A very large percentage of this process is subjective. One winning race car driver will often have his car set up TOTALLY different than another. It`s up to you to determine and feel out where changes and adjustments need to be made and yes good record keeping is a must. Start out with good solid geometry,select common sense spring and swaybar rates and use adj. shocks to give you some tuning range there. Don`t try to get overly radical. I generally do geometry,alignment,spring rates,swaybar rates and dampening rates in rough order. Once the first is pretty much set I go onto the next. Once geometry,alignment and spring rates are pretty well determined I use swaybar rates and dampening rates to fine tune the package. Bear in mind that`s a very rough overview of the process and that one aspect is really as important as another in the big picture. Mark SC&C