My car rides like a skateboard

[SUNNY Z]

Ok, so my car is on ground control coilovers 225F 250R, TTT camber plates, TTT t/c rods, sectioned struts with tokico 5 way adjustable shocks, lowered ~3" and 275-40-17 tires.

 

The ride is VERY stiff, and when you get onto certain cement surfaces, it will almost buck. I've played with the shocks, but found that they're the best in the middle, with both the 1 and 5 settings being more harsh. ?

 

I'm just curious if this is just the way the car is going to be, or if there is something I can do (pseudo easy) to make it ride better.

 

Thanks

Edited September 18, 2012 by SUNNY Z

[johnc]

Ride harshness comes down to these things:

 

1. Tire pressures.

2. Tire sidewall height.

3. Tire sidewall construction.

4. Suspension bump travel.

5. Bump stops.

6. Shock compression damping.

7. Friction in the suspension.

8. Suspension bushing material.

 

What are the answers to the questions above on your car?

[Dan Juday]

9. Spring rates.

[johnc]

Spring rate generally does not contribute to ride harshness. My racing 240Z had spring rates in the mid to upper 300s with Penske shocks and the folks that rode in it with me said it felt like the car had cat feet. Conversely my 1971 with Eibach progressive springs and HP shocks rode pretty stiff.

[ComicArtist]

Ride harshness comes down to these things:

 

1. Tire pressures.

2. Tire sidewall height.

3. Tire sidewall construction.

4. Suspension bump travel.

5. Bump stops.

6. Shock compression damping.

7. Friction in the suspension.

8. Suspension bushing material.

 

What are the answers to the questions above on your car?

 

With all due respect, I prefer to think that it's simpler than that.

 

IMO, harshness comes down to either

 

a) SPRING PRELOAD

Shock travel (not having enough)

c) Tire sidewall (to an extent)

 

It mostly depends on your preload. Too much preload will cause your springs to be wayy too stiff, no matter what your spring rates. Too little preload will cause you to ride the bumpstops, and you'll have no dampening.

 

Spring rates are fairly irrelevant if they're set up right. I'm running 10/12k springs comfortably.

 

Tire sidewall isn't going to affect it too much. I'm running a stretched 205/50/15 with 55psi in each tire and it's comfortable.

 

I'd look into your preload.

 

On an afterthought, what's your tire pressure? A 275/40 should be a decent enough sidewall for mild comfort.

Edited September 19, 2012 by ComicArtist

[RebekahsZ]

We don't have ANY preload with GC system do we? Not unless we have droop limiters. Sunny, how does it ride with the drag slicks? That will let you know if it is tire sidewall, which I think it is. I have same spring rates and shocks. I can't FEEL any difference between any of my tokico shock settings. My car rides very nicely. I can feel a huge difference depending on what tire I have mounted: R1s at 30psi to 50series radials for street to bias ply slicks and skinnies. Seat cushion firmness matters a lot too. You might also be feeling the whiplash effect of those quick a s s ETs and reaction times versus the inertia of your big mellon head. Johnc you forgot to list a loose helmet strap.

[SUNNY Z]

We don't have ANY preload with GC system do we? Not unless we have droop limiters. Sunny, how does it ride with the drag slicks? That will let you know if it is tire sidewall, which I think it is. I have same spring rates and shocks. I can't FEEL any difference between any of my tokico shock settings. My car rides very nicely. I can feel a huge difference depending on what tire I have mounted: R1s at 30psi to 50series radials for street to bias ply slicks and skinnies. Seat cushion firmness matters a lot too. You might also be feeling the whiplash effect of those quick a s s ETs and reaction times versus the inertia of your big mellon head. Johnc you forgot to list a loose helmet strap.

 

Well the track is a lot different than the poorly engineered concrete street with joints every 20', so i can't even make a comparison.

 

There is almost zero preload on the springs. Its not hitting bump stops (i don't think). PSI is around 35#

[RebekahsZ]

So drive around town a little with your slicks on...

 

Concrete joints are a killer with spherical bearings on the camber plates. There's always a little play. A gravel road is even noisier. Any problem on regular bumps or dips? I don't think you can get away from the noisy jarring and jolting that happens on concrete joints or bridge transitions. In my car those transitions sound bad, but really don't rock the car. I thought you'd have a come-back for that mellon head crack!

Edited September 19, 2012 by RebekahsZ

[zero]

I've got a similar setup except I kept the stock tophats and TC rods and I'm running 16's with a bit more sidewall. I find the ride to be very decent, at least on the softer strut settings. I stayed away from camber plates because after riding in a friends car before and after them the added NVH was very noticeable with no other changes. I suspect my sidewall makes a big difference as well.

[johnc]

Concrete expansion joints are different then regular bumps in the road. These are sharp edged and require an immediate longitudinal response from the suspension to reduce impact harshness. Urethane and solid TC rod bushings do not allow that longitudinal compliance so the tire takes all of the load because the suspension (shock and busing) cannot react fast enough due to stiction and inertia. Also, the high shaft speed compression damping on the Tokico shocks is incredibly stiff because their valving cannot react fast enough.

 

The tire is a spring with its rate determined primarily by air pressure and secondarily by its construction. A crude number is 50 lb. in. of spring rate per 1 psi., so a tire with 30 psi has an undamped spring rate of 1,500 lb. in. A tire with 55 psi has an undamped spring rate of 2,750 lb. in.

 

Anything you can do to reduce friction in the suspension will help. Adding longitudinal compliance will also help.

[SUNNY Z]

Also, as long as I'm whining, the front end on this thing is SQUEAKY. Everytime the control arm moves, it squeaks. Both sides. Sounds like metal on metal almost. Yes I greased the poly bushings - liberally. As well as the tie rod ends and ball joints. Only other thought was maybe the heim joints on the TC rods? Usually those rattle and don't squeak though....

[johnc]

If you're running urethane lower control arm bushings remember to not tighten the bolt to the factory spec. You want to tighten it down to the point that it takes a little effort to move the control arm up and down. Maybe 3 lbs. of force from your hand on the end. Make sure you also use a new lock nut on the lower control arm bolt.

[JMortensen]

Not sure I like the leave it loose method. I would sand the bushing down so that the steel sleeve is the same length when installed, so that when the nut is torqued there isn't a lot of preload on the bushing.

 

I haven't tried it, but I think on the front control arm you should also be able to add a zerk and grease the bushings. Doesn't work with the rear inner bushings, but I did that on the rear outers and it worked fine. Basically the bushing has to be tight in the arm so that when you grease it the grease makes its way between bushing and sleeve.

 

Also, run your shocks on 1 or 2. I ran 200/250 with Illuminas and my 75 year old dad's comment when he got out was about how comfortable the Recaros were. If you're getting harshness on 1 or 2, it's probably because you're bottoming out.

 

Another thing to look at is bump stops. Having recently gotten into Miatas, I can say that they are light years ahead of us on bump stop tech. Most of us use Energy Suspension poly bumpstops, they have different stops with different spring rates, progressive, linear, etc. Fat Cat Motorsports has a wide selection. I just changed my stock rears to Koni 40mm bumpstops and had a huge improvement over concrete joints. Miatas run practically sitting on the bumpstops, so they're much more important. You might now be in the same boat if you've got 17's and you're trying to run it low enough to "look right".

Edited September 21, 2012 by JMortensen

[RebekahsZ]

Look at my learning to drag race thread and you will find pictures of the bumpstops jnjdragracing recommended. Also, did you use progressive springs? They coil bind really bad and that feels just like bottoming out. Simple way to find out if coil bind bumpstops orbottoming out is the problem is to raise ride height and see if problem goes away. Actually coil bind could continue even still. That can be seen by jacking car up by by LCAs with tire off.

[SUNNY Z]

These are not progressive rate springs.

 

I'm running the bump stops provided in the full bushing kit.

 

It is possible that the car is bottoming out, but when I run on 1 or 2, it seems to bounce TERRIBLY. Like it just gets in rythem and stays there.

[JMortensen]

It is possible that the car is bottoming out, but when I run on 1 or 2, it seems to bounce TERRIBLY. Like it just gets in rythem and stays there.

That's what my Miata was doing. Felt like it was going to shake my teeth out. The bumpstops that came in your bushing kit are poly.

 

3 options I see:

 

1.Swap them out for FCM or Koni stops

2. Raise the car

3. Up the spring rate so that you don't hit them as often

 

 

[SUNNY Z]

That's what my Miata was doing. Felt like it was going to shake my teeth out. The bumpstops that came in your bushing kit are poly.

 

3 options I see:

 

1.Swap them out for FCM or Koni stops

2. Raise the car

3. Up the spring rate so that you don't hit them as often

 

Ok. Where can I get some different stops at? I dno't really want to raise the car, as I think it'll look out of place. And spring rates... eh, I think pre-bump stop ride quality might suffer.

 

I might get froggy sometime and raise the car up an inch and see how it rides.

[JMortensen]

I'd try Fat Cat Motorsports. http://www.fatcatmotorsports.com/

 

Just give the guy a call. Everyone says he's super helpful, although I haven't talked to him personally.

[Snailed]

I have noticed that the ratio of unsprung weight to sprung weight can change how harsh a suspension feels too. If you have extremely heavy wheels/brakes/tires on a very light car it won't ride nearly as nice as a car with lighter unsprung parts. I have installed lots of lightweight wheels and tires on various cars and the ride nearly always improves, even when the sidewall height decreases and the wheel diameter increases over stock.

[SUNNY Z]

I have noticed that the ratio of unsprung weight to sprung weight can change how harsh a suspension feels too. If you have extremely heavy wheels/brakes/tires on a very light car it won't ride nearly as nice as a car with lighter unsprung parts. I have installed lots of lightweight wheels and tires on various cars and the ride nearly always improves, even when the sidewall height decreases and the wheel diameter increases over stock.

 

Hmm. This might have something to do with it. However, I feel that the root cause is somewhere else.