1g coilover/suspension adjustment

[talon77]

I searched & searched but couldn't find anything definitive on this... I'm almost finished installing a set of JIC FLT-A2 coilovers on my '94 talon awd and I would like to set the ride height this weekend. The car will be used for mostly hard street driving and perhaps some autox/road course. My questions are as follows:

1. I'm not looking to crazy lower the car, I just want to lower to enhance handling performance. I recall reading somewhere Mike from DSS recommending setting ride height to 13.75" from center of wheel to fender edge... Can anybody confirm what his F/R ride height recommendations were? Or perhaps provide a good ride height recommendation measured from wheel center to fender edge?

2. From what I gathering so far from searching the forum, a good street/track performance alignment is: Front- 2.0 neg camber with 1/16" toe out Rear- 1.5 neg camber with 0" toe. Can someone with 1g suspension knowledge confirm?

Thanks in advance for your help, I'm really looking forward to getting my 1G back on the road with the new suspension

 

[WatchItExplode]

Try to contact John Mueller at RRE, he's a pro setting up the FLT-A2's. www.roadraceengineering.com

 

[talon77]

I am hesitant about contacting Mueller @ RRE because I bought the JICs from another 'tuners member and it is my understanding that RRE keeps their proprietary JIC adjustments/settings very hush hush; you only get the settings if you bought from them.

Having said that, I set the front ride height this weekend so that the front control arms are just slightly higher than parallel....this ended up measuring 14.5" from center of wheel to fender lip. This actually appears just a little lower than stock, but not by a huge amount. I plan on setting the rear ride height so that it sits just slightly higher than the front.

I appreciate the RRE suggestion though. Any ride height suggestions from dsm handling wisemen are still definitely welcome, since I haven't set the rear ride height yet. If I don't get any, no big deal. I'll still post back to let you guys know how it turns out.

 

[Zenja]

What's the proper way to set ride height, if you can't do corner balancing? It seems to me like setting the height by making the height of the car the same in each corner wouldn't be a good idea. If you set all the coilovers to the same height setting before putting them on the car, the heavier corners of the car would ride lower. Now if you raise those heavier corners to equalize the height, you'd be putting even more weight there. It seems better to just set both front and both rear coilovers to the same height adjustment. Then, looking at some posted stock corner weights, I might lower certain corners by just a bit to go toward a better corner balance. Am I wrong? I'll be doing this in a few days.

 

[underradar92]

It is nearly to impossible to get an equal L/R weight on a DSM. The only true answer is to cross-weight them, so at least it doesn't act like a 4 legged table with 1 short leg. Keeping the front control arms a bit up from level is a good start, although I've yet to read of anyone who has over-lowered to the point where the evils of geometry have destroyed handling. Maybe we don't have enough vertical travel?

Since you should get an alignment anyhoo, why not look into a shop that can cross weigh it at the same time?

Maybe a local racer has scales, you could buy him/her some beers for they're efforts.

 

[RusherRacing]

Well if you were local you could buy me some beer (actually I prefer a good canadian wiskey) to cross weight your car. But since your not here is a couple suggestions. These are general to setting up a car with out scales.

I typically lower the car as much as possible with out it rubbing and able to keep the aligment within spec keeping the L/R and F/R all equal. Most cars I have put on the scales when the ride heights are all set equal is the driver front is slightly heavy. Normally it takes about 1/4 1/2 a turn in the height (shorter) adjustment to balance out the car.

now this will probably get you 95% of the way, the rest will need to be fine tuned with a set of scales.

 

[talon77]

1. Zenja: Can't tell you the "proper" way to set ride height w/o corner balancing, but so far I've adjusted the front ride height so that FL/FR sides are both at 14.5" from wheel center to fender lip (measure when car is on the ground and suspension is loaded). My plan was to proceed with adjusting the rear suspension so that it sits just slightly higher than the front. It is my understanding that this rear-slightly-higher arrangement is consistent with most performance car setups. Don't bash, but I know that the porsche 944 and boxster guys do this. The wisemen can feel free to correct me if I'm wrong, as I'm not making any claims of being right

2. underradar: My understanding has always been that keeping the control arms a bit up from level was a bump steer thing. Could possibly be a vertical travel issue as well, but I don't know for sure. You bring up a good point though, I might as well ask the alignment shop about corner balancing and cost difference.

3. RusherRacing: Sucks you're in South Dakota man, I'd take you up on that in a second You are alright though. Just curious, if the driver frt is slightly heavy, do you take a 1/4-1/2 turn shorter height adjustment out of just the driver frt side or is the shortened height adjustment made on the other 3 sides of the vehicle? Could be wrong, but it just makes sense to me that raising the height on one corner takes away some weight from that corner. Right or wrong?

I'm in the Baltimore, MD area so I plan on contacting either Extrememotorsports or MachV about doing an alignment and getting the cost with and w/o corner balancing. Let you guys know how that pans out.

Thanks guys

 

[Rx3]

2. From what I gathering so far from searching the forum, a good street/track performance alignment is: Front- 2.0 neg camber with 1/16" toe out Rear- 1.5 neg camber with 0" toe. Can someone with 1g suspension knowledge confirm?

I think that rear camber number is a bit aggresive I would go with - 0.5 unless you have some weird wheel size that you need to tuck into the wheel well or if you minimize your street use. If you run -1.5, you will need to budget replacing your tires a lot sooner, and you will have to be very precicse on rotating the tires.

 

[talon77]

Actually, that IS alot of neg camber based on Mike@DSS's recommendation for 1g awd dsm:

Front: -2.5 w/ 1/8" toe
Rear: -1.0 w/ 1/32" rear toe

Link:

http://www.wincom.net/trog/autocross/1G_SM.html

I'm leaning on using those specs now, since the car will only see "weekend" time and won't be driven daily. Hopefully, the aggressive camber settings won't chew up my tires too bad if only driven on weekends and I religiously rotate tires. I've heard that most 1g dsmers go with 0 toe in the rear, that might help.

 

[RusherRacing]

You will want to shorten the Driver Front. How can I help you visualize this. Take a hard book place 4 quarters under 3 corners, place 3 quarters on the 4th you see there is no weight being applied to that stack. Does that help? Someone local should be able to corner balance your car but they would probably charge an arm and a leg. Corner balancing does help especially if your getting into racing where your car will see the max. Mainly because one tire will brake loose first and you could boil one tire and the rest be relitively cold... But if your only going to drive it on the street I personally wouldn't worry about it. Set them all the same and be done with it.

 

[RusherRacing]

Actually, that IS alot of neg camber based on Mike@DSS's recommendation for 1g awd dsm:

Front: -2.5 w/ 1/8" toe
Rear: -1.0 w/ 1/32" rear toe

Link:

http://www.wincom.net/trog/autocross/1G_SM.html

I'm leaning on using those specs now, since the car will only see "weekend" time and won't be driven daily. Hopefully, the aggressive camber settings won't chew up my tires too bad if only driven on weekends and I religiously rotate tires. I've heard that most 1g dsmers go with 0 toe in the rear, that might help.

That looks like a good setting for your alignment, the front toe could be a little more neutral but that would affect your street driving.

 

[Rx3]

Actually, that IS alot of neg camber based on Mike@DSS's recommendation for 1g awd dsm:

Front: -2.5 w/ 1/8" toe
Rear: -1.0 w/ 1/32" rear toe

Link:

http://www.wincom.net/trog/autocross/1G_SM.html

I'm leaning on using those specs now, since the car will only see "weekend" time and won't be driven daily. Hopefully, the aggressive camber settings won't chew up my tires too bad if only driven on weekends and I religiously rotate tires. I've heard that most 1g dsmers go with 0 toe in the rear, that might help.

Yeah, that looks better.

But if your only going to drive it on the street I personally wouldn't worry about it. Set them all the same and be done with it.

Yep, that's basically what I did. I decided if I ever get really serious about auto-x (i.e. trying to do ProSolo), I'll have it properly cornerweighted later. It should be find for your local events and street driving.

 

[Zenja]

Well if you were local you could buy me some beer (actually I prefer a good canadian wiskey) to cross weight your car. But since your not here is a couple suggestions. These are general to setting up a car with out scales.

I typically lower the car as much as possible with out it rubbing and able to keep the aligment within spec keeping the L/R and F/R all equal. Most cars I have put on the scales when the ride heights are all set equal is the driver front is slightly heavy. Normally it takes about 1/4 1/2 a turn in the height (shorter) adjustment to balance out the car.

now this will probably get you 95% of the way, the rest will need to be fine tuned with a set of scales.

Thanks for that figure. If I can't find a reasonable way to get corner balancing done, I'll go with the 1/4 to 1/2 turn.

About camber, I think I'm at -1.7* front and -2.2* rear right now with no toe and I'm not getting any excessive or uneven tire wear. The inner fronts are slightly more worn but this can be attributed to other things in my case too. Once I put the camber kit on and lower the car more, I think I'll go with -2.0* (or maybe slightly more negative) on the front and about -1.0* to -1.5* on the rear. Negative front camber seems to help a lot with cornering, but I also need camber all around to help clear the tires from the fenders.

 

[talon77]

Rusher, when alignment specs indicate 1/8" toe (let's use the front toe for this example). Does that generally refer to 1/8" toe total = 1/16" toe for front left + 1/16" toe front right? If so, that certainly SOUNDS like it's not much... It has always been my understanding that a small amount of front toe out helps the car turn in. But too much and the car wants to wander and I'll be buying new tires frequently. BTW, I'll probably go with your recommendation and skip the corner balancing due to the primarily street use of the vehicle. I do however still plan on finding out the cost difference w/ and w/o corner balance from my local shop, just so I can give other tuner members an idea of the cost...

 

[RusherRacing]

I am guessing that is toe in since almost any rated spec is toe in.
Toe out does help turn in which DSM's NEED help with. However Toe out Sucks to drive on the street, every little dip, crack etc you car will want to follow. I would recommend a 1/16" toe in, a 1/32 each side. Turn in will be better than 1/8" and it won't wonder as badly. Another trick you can do to keep you car driving straight on crowned roads is tweak or right and left camber to compensate for the crown, it makes highway driving nice. I can't remeber how much, it was like 2 years ago last time I did that.
I am curious to what shops charge to set a suspension let me know will you. (I will have to keep that in mind when tweaking friends cars ).

 

[underradar92]

2. underradar: My understanding has always been that keeping the control arms a bit up from level was a bump steer thing. Could possibly be a vertical travel issue as well, but I don't know for sure. You bring up a good point though, I might as well ask the alignment shop about corner balancing and cost difference.

Bump steer is, as I understand it, usually corrected at the tie rod ends or the rack is re-located, whereas the under-centering of the control arms does weird things to the roll center. This is the way I understand these things, if someone (JToby?) has a detailed understanding/diagrams, I'm all eyes.

 

[RusherRacing]

This is a little something I wrote for a local website.

BUMP Steer
To continue with steering, after my last sessions I was posed a question on bump steer. Bumb Steer/Roll Steer is the change in steering angle as the suspension travels. Roll steer is the same thing as bump steer only that the suspension system is working because of the roll of the car. I prefer to design a suspension that doesn't include this but in most peoples case that isn't an option the steering geometry is predefined from the manufacture. So what you need to do is understand it! Its best explained visually and in person, or in a active 3D model. Neither of which I have the means of doing. I will explain it the best I can and then give you some very good reference material on this topic.

On most cars as your suspension travels up your tire will turn in, and has your tire droops it will toe out. For zero bump/roll steer the tie rod must travel on the same arc as the suspension travels. Zero bump steer is Ideal, as bump steer can cause adverse and unforeseen handling issues. One major issue is hitting a bump while in a hard corner, when the traction capability is all ready bordering breaking loose and the increased steering angle caused from the bump will cause it to break loose.

If you can obtain detailed tire analysis on your set of tires( very very hard to find). I have a copy of some Goodyear race slicks analysis. Look at a Lateral holding vs. Slip angle graph, mine shows that for every degree you loose in your ideal slip angle you can loose 160+ lbs of lateral holding capability per tire. When your tires can only hold 500 lbs of lateral holding capability that is a staggering number. (note these are number suited to the Formula SAE car, and the lateral holding capability and loss due to slip angle will both be much higher on standard vehicle do to the increased normal force.)

Please read http://www.ffcobra.com/FAQ/bumpsteer.html for one of the simplest resources I can find on bump steer.

 

[jtmcinder]

The reason to keep the lower control arms angled down slightly (to the wheels) is to keep the lateral force when turning from lowering the outside side of the car even more than what you're getting from weight transfer. (It has nothing to do with bump-steer, although bump-steer is an important issue.) Think about it this way: most of the lateral force when turning goes from the outside wheel to the chassis via the lower control arm. If this arm is angled up from the chassis to the wheel, then the force will lever the outside half of the car down even more. If this arm is angle down from the chassis to the wheel, then the force helps keep the car level.

- Jtoby

 

[underradar92]

If this arm is angled up from the chassis to the wheel, then the force will lever the outside half of the car down even more. If this arm is angle down from the chassis to the wheel, then the force helps keep the car level.

- Jtoby

Cool, thank you JToby, for the expert testimony, this is what I'd hoped for.

Thereby making the effective spring rate decrease, and if a bump or a dip is encountered, the rate is compromised by the angle, giving inconsistent cornering performance... AKA, the odd handling quirks I was referring to previously.

This may not actually be "roll center" though, as I'm not an engineer, or even any good at geometry.

 

[talon77]

My bad, I mixed up angularity of the tie rods with angularity of control arms, as it relates to bump steer. Thanks for clearing that up guys, sorry for the bad info! I knew there was some merit to running the control arms "downwards." In any case, I ended up with the following measurements (as measured from wheel center to fender lip):

1. Front: 14.25"
2. Rear: 14.75"

Driver and passenger ride heights are the same. I haven't had the chance to get the car aligned yet, its just chilling in the garage ### I've been travelling too much. I'll keep you guys updated and will post pics soon.