H&R Coil-overs - Linear Springs with Higher Rates to Improve Ride?

[Jason5driver]

I have H&R coil-overs on my E39 525i.

When installing these and talking to H&R, I have found that the coil-overs are really H&R springs with Bilstein struts and shocks, but just valved to H&R's specs.

Ever since installing them, they have been rough riding, and cause the tires to lose contact with the road and larger bumps.

I find this very scary and unsafe when pushing the car in a turn or braking.

The car will hit a bump, and the car will go air-born, then I finally regain control.

The car hops / skips over bumps.

These H&R coil-overs are very similar to the Bilstein PSS coil-overs.

The H&R coil-overs have progressive springs with 325 lbs/in fronts, and 205 lbs/in at the rears (according to H&R).

I tried having the car approximately 1" - 1 1/2" lower than the OEM non-sport height per H&R's requirements, but the ride was still non-compliant.

I have found that with these coil-overs, the car rides better with the car lower, because it compresses the springs less (springs are more compressed at raised car height).

I have read that it is normal for Bilsteins to have high compression damping and very low rebound damping, which I guess is the opposite of Koni?


1. I am wondering if linear springs with higher spring rates will help the car ride better by pushing the tires back into the pavement, and help keep contact with the road.

Another thing I have found weird is that the car rides better with lots weight in it - with the whole family in the car, and groceries in the trunk.


2. What is the cause of this? When adding weight to car, does this increase the spring rates of the springs?

This is my last ditch effort for this suspension...

Thank you for your input.

Thanks,

Jason

[Turbohugh]

I've been informed that when you go to coilovers and lower the car it's a good idea to get it corner balanced . Uneven weight distribution can really upset your vehicle dynamics .

[scooper]

go back to a regular damper spring combo. Coilovers are for the track. You can't expect to get good ride characteristics nor handling on bumpy streets, especially with lots of weight. Try some m5 springs with konis or maybe Bilsteins. There's no substitute for damper travel.

[Jason5driver]

I've been informed that when you go to coilovers and lower the car it's a good idea to get it corner balanced . Uneven weight distribution can really upset your vehicle dynamics .

I have looked into corner balancing, but no one local really wants to consider my car.
Also, my car is lowered approximately the same amount all around from the stock height, so there is no rake - the car sits flat.

go back to a regular damper spring combo. Coilovers are for the track. You can't expect to get good ride characteristics nor handling on bumpy streets, especially with lots of weight. Try some m5 springs with konis or maybe Bilsteins. There's no substitute for damper travel.

I am considering the OEM Sachs struts and shocks with either Dinan springs or B&G springs.
M5 springs will not work because my car has an inline-6, the M5 is a big heavy V8.
Travel is not the issue.
These coil-overs ride better lower with less travel, and added weight.
Which leads me believe that there is a problem with the springs.
I can't tell whether the springs are too stiff, or too soft.
I assume too soft because 325 fronts and 205 rears is pretty low.
However, since the car rides better with more weight, might mean that the springs are too stiff.

[=BA=]

I would rather think springs are too soft and ride height too low. Try increasing the ride height see if that helps. You might simply be banging on the bumps tops. Especially in the rear.

The reason it drives better with more weight is probably because it's sitting on the bump stop all the time and doesn't impact as much. Other option is that rebound in the dampers is too low. But with your spring rates and vehicle weight it wouldn't require a lot of rebound force I would think.

[Jason5driver]

I would rather think springs are too soft and ride height too low.
Try increasing the ride height see if that helps.
You might simply be banging on the bumps tops.
Especially in the rear.

The reason it drives better with more weight is probably because it's sitting on the bump stop all the time and doesn't impact as much.
Other option is that rebound in the dampers is too low. But with your spring rates and vehicle weight it wouldn't require a lot of rebound force I would think.

I have tried raising the ride height - to H&R's requirements, and almost at the OEM stock height.
The ride is worse at those raised heights.
The coil-overs compress the springs more at the raised heights, which creates almost a pogo-stick effect when driving.

If the car was riding on the bump stops all the time, wouldn't you feel that ALL the time...? (bang-bang-bang...)
Yes, I agree the rebound is too low, or non-existent.
Hence, the reason why the tires lose contact with the road.

Would linear springs with high rates help increase the rebound, or push the tires to the road better?

[Turbohugh]

You probably should go back to stock suspension until you learn more about suspension .


Sent from planet Earth

[Jason5driver]

You probably should go back to stock suspension until you learn more about suspension .


Sent from planet Earth

Please enlighten me...

[Turbohugh]

Please enlighten me...

Check out suspension article on this website .

Some of your theories about how and what to adjust will be clarified here , and may help you decide what you want to go for. For example a street car that's only going to autoX may find bigger swaybars and stock springs to be better .

http://www.rapid-racer.com/suspension-tuning.php

[=BA=]

I have tried raising the ride height - to H&R's requirements, and almost at the OEM stock height.
The ride is worse at those raised heights.
The coil-overs compress the springs more at the raised heights, which creates almost a pogo-stick effect when driving.

If the car was riding on the bump stops all the time, wouldn't you feel that ALL the time...? (bang-bang-bang...)
Yes, I agree the rebound is too low, or non-existent.
Hence, the reason why the tires lose contact with the road.

Would linear springs with high rates help increase the rebound, or push the tires to the road better?

If you have a non existent rebound then higher rate springs will simply make ride quality worse as it will create more chassis oscillation.

If you are compressing the springs when you are increasing rideheight, you are compressing them against the damper end stops. Not good as you are preloading the springs. This limits rebound travel a lot. So in that case I would suggest going lower. While this might decrease compression travel the added rebound travel might fix it.

[Jason5driver]

Check out suspension article on this website .

Some of your theories about how and what to adjust will be clarified here , and may help you decide what you want to go for. For example a street car that's only going to autoX may find bigger swaybars and stock springs to be better .

http://www.rapid-racer.com/suspension-tuning.php

Thanks much for the link!
That is a great write-up.
My car is mostly a daily driver, but if I am lucky I am able to make a couple of auto-crosses a year.

If you have a non existent rebound then higher rate springs will simply make ride quality worse as it will create more chassis oscillation.

If you are compressing the springs when you are increasing rideheight, you are compressing them against the damper end stops. Not good as you are preloading the springs. This limits rebound travel a lot. So in that case I would suggest going lower. While this might decrease compression travel the added rebound travel might fix it.

It is interesting, but according to the article in the link above, the car's symptoms point to too much rebound damping.

From the article:

"If there is too much rebound stiffness, then the wheel could hold longer in the wheel arch then needed, effectively losing contact with the road as the force to push the wheel back down is slower to respond to the changing surface levels.
This state is again far from ideal and it is best to make sure a good level is set for optimal tyre contact with the road."

1. Wheel can not keep up with road surface changes.

2. Inside cornering wheel could be pulled of road by shock.

3. Car could become jacked down in long corners (lowered ride height).

[=BA=]

If your rebound travel is too short the same will happen, you loose contact with the road.

[Jason5driver]

If your rebound travel is too short the same will happen, you loose contact with the road.

So, you are suggesting to lower the car even more to increase rebound travel?
Would linear springs with higher rates play any role in this?

[MIKYZZ4]

This thread cries out for a suspension "guru " to respond! OP, read up on the Similar Threads below.

[Turbohugh]

If it were my car is raise it back up starting at stock height ( I know it's ugly) set it all full soft then start turning up compression til it's firm , then back off slightly. I would turn both ends up evenly . Then do the same for rebound ( if you have rebound adjustment) Onc it's riding nice at stock height I would start lowering it 10mm at S time . After the height and damping is good I'd get corner balancing and alignment . If it were my car .
Oh it's fairly important to have a precise and repeatable method of measuring ride height . Two ways would be center of axle to highest lip on fender / wheel arch. The way I use is edge of wheel to highest edge on fender

Sent from planet Earth

[=BA=]

As far as I know there is no damper adjustment, only rideheight. Also setting corner weights is not so important with very weak springs like on the car of the topic starter.

What I would do in your case is simply try and measure where you are in the damper stroke.

Usually this can be done quite easily.

Jack up the car. Measure the distance between the fender lip and center axle, this is full droop.

Take off the wheel, turn the spring platform all the way down. Use a second jack underneath and jack up the damper to the point where it touches the bump stop. Measure fender lip to center axle again. You now have a upper and lower value.

Try to set your rideheight in the middle of those 2 values. This will give you 50% rebound and 50% compression. And try from there. A figure of 40% compression vs 60% rebound travel is often a good starting point as well, which means lowering it slightly from that value.

For stiffer linear rates you have to work out a bunch of other things so you will have the correct length and balance. But if rebound stroke is your issue, this will not change with stiffer springs if you run the same rideheight.

Simple test is also, jack up the car and simply measure how much rebound travel you have now. If that is only a few centimeters then you know that's your problem and you need to lower the car.