A discussion on improving ride quality

[wparsons]

Originally Posted by Ubersuber

Um, yes, I can quite see how you missed the actual point made in the link.

Annnnnnd, I feel like I'm in kindergarten again.


Your ability to contradict yourself is simply amazing...

Originally Posted by Ubersuber

Rear suspension travel is effectively longer than the front mainly because the motion ratio is less due to the position of the rear coilover.

The big difference is the hardness of the bump stops. Although the motion ratio effects would apply more leverage to the rear bump stops than to the front the rear bump stops are as long as and much harder than the front bump stops.

The rear bump stops should be shorter to allow for the motion ratio difference but they aren't. The net effect is the rear suspension begins to bottom out on the bump stops much earlier and more firmly than at the front.

So which one is it? Does the motion ratio (your welcome by the way, I see you added a new term to your vocabulary) give more travel, or less, before engaging the bump stop?

Originally Posted by Ubersuber

The progressive compression of the bump stops masks this effect to some degree but it is very real and I am pretty convinced this leads to the tail happy character of this car. Certainly the spring rate doesn't explain it.

It's your lack of throttle restraint that is the issue, nothing further.

Originally Posted by Ubersuber

Winter driving will reveal if I have achieved my primary objective of improving rear grip on snow and ice.

Do you really think you're getting that much suspension compression on snow/ice without hitting a big bump? You're more clueless than I thought. Driving on flatish ground on snow/ice you're going to get VERY little suspension movement without bumps. Yet another swing and a miss for you.

[Trettiosjuan]

A little comment to the kindergarden discussion above. Ubersuber could be more careful in his statements, but that doesn't mean they don't have subjective value. Yes subjective, depending on the road, the car and the person, subjective impressions can differ a lot. I was driving in another country the other week that has a lot of small edges and small fast undulations, and the ride was awful. Happily I don't drive their often, before I had driven there, I wouldn't have known. It depends, you see?

If Ubersuber had a solution to his subjective problem, fine. That is interesting even if I don't experience the problem to the same degree.

As in the explaining suspension, we're here to discuss and learn , and perhaps some again express themselves a bit overly confident , but then again, it doesn't mean it has no value. If instead of trying to understand what is meant one goes and try to find error, that isn't helping the thread either...

If someone is more knowledgeable and now understand various psychological effects and how these impede communication, perhaps they can also be understanding and pedagogic?

[Captain Snooze]

Originally Posted by Ubersuber

Rear suspension travel is effectively longer than the front mainly because the motion ratio is less due to the position of the rear coilover.

Huh? This makes no sense.The the rear wheel travel is what it is regardless of the motion ratio. The effective spring rate is different due to the motion ratio.

[Trettiosjuan]

Originally Posted by Captain Snooze

Huh? This makes no sense.The the rear wheel travel is what it is regardless of the motion ratio. The effective spring rate is different due to the motion ratio.

I don't know either what the point is, but what can be said is that the rear strut stroke is shorter than the rear wheel travel. Edit: so if the front and rear struts have the same stroke, rear wheel travel will be longer because of the motion ratio.

What I mean is that the rear feels short, probably because the bump stop effectively progressively raises the spring rate as it engages over bigger bumps, but there remains plenty of travel hence why I can go proper fast in bumpy turns without the rear flying all over the place.

[wparsons]

Originally Posted by Trettiosjuan

A little comment to the kindergarden discussion above. Ubersuber could be more careful in his statements, but that doesn't mean they don't have subjective value. Yes subjective, depending on the road, the car and the person, subjective impressions can differ a lot. I was driving in another country the other week that has a lot of small edges and small fast undulations, and the ride was awful. Happily I don't drive their often, before I had driven there, I wouldn't have known. It depends, you see?

If Ubersuber had a solution to his subjective problem, fine. That is interesting even if I don't experience the problem to the same degree.

As in the explaining suspension, we're here to discuss and learn , and perhaps some again express themselves a bit overly confident , but then again, it doesn't mean it has no value. If instead of trying to understand what is meant one goes and try to find error, that isn't helping the thread either...

If someone is more knowledgeable and now understand various psychological effects and how these impede communication, perhaps they can also be understanding and pedagogic?

Look for posts by a banned user with the name Suberman, same guy as Ubersuber. I'm not patient with him because we've been through his nonsense before.

The real issue with his suggestions is that he makes claims that contradict everyone else in the automotive world (and physics) with no evidence and expects everyone to just accept him as an encyclopedia of knowledge.

He claims that the rear shocks were underdamped and by putting bilsteins (which have stiffer damping) the handling over bumps was vastly improved and it's lees likely to oversteer. Two big issues there: 1) people that have actually done the testing found that the stock shocks are actually overdamped and 2) increasing rear damping (compression or rebound) makes the car more likely to oversteer.

His complaint about the rear feeling loose over bumps is most likely to be because the rebound is too stiff stock and the wheels can't droop fast enough to stay on the road. I've felt that with stock springs, but with the springs I have now it's not an issue.

[Ubersuber]

Segueing into actual evidence:

A little surfing finds you here:

http://www.iwsti.com/forums/gd-suspe...ump-stops.html

or here:

http://www.rs25.com/forums/f9/t76419...surements.html

Lots of discussion about essentially the same problem both from a ride perspective and a handling perspective. An Impreza is an Impreza whatever you might wish to think.

[gramicci101]

Originally Posted by Ubersuber

Lots of discussion about essentially the same problem both from a ride perspective and a handling perspective. An Impreza is an Impreza whatever you might wish to think.

This may come as a surprise to you, but BRZs are not Imprezas, whatever you may wish to think.

[stonenewt]

So getting back on topic. What we're saying is the first port of call for the rear of the BRZ is to get new dampers which are slower on rebound damping & possibly bump damping as well? This will allow the rear wheels to maintain better contact with the road & thus improve handling a bit?

[gramicci101]

The first port of call is to get springs that are not overpowered by the OEM dampers. All the way around, not just in the rear.

[stonenewt]

With a damper & spring miss-match you can do two things. In the context of back road driving with lots of surface imperfections are we certain that a more rigid suspension setup is better?

To me the weight transfer is about right which suggests the springs are closer to being right than the dampers. Thus shouldn’t the damping be slowed down to match the spring strength?

Am I making any sense here?

[gramicci101]

You can go that direction, sure. It'll be a little challenging to find struts that match the springs, vs. the other way around. Also, if the suspension becomes softer, you'll find yourself hitting its limits more frequently. You might be better served finding struts with separately adjustable compression and rebound, so you can set them up as you see fit. If for no other reason than they're easier to find.

But don't change just the rear struts and leave the fronts stock, like others are suggesting.

edit: This thread may have what you're looking for.
http://www.ft86club.com/forums/showthread.php?t=57564

[stonenewt]

Slowing the damping down shouldn't cause significantly more suspension movement, only allow it to happen quicker. If you're running out of suspension travel under cornering loads would you use stiffer ARBs to reduce body roll?

[wparsons]

Originally Posted by stonenewt

With a damper & spring miss-match you can do two things. In the context of back road driving with lots of surface imperfections are we certain that a more rigid suspension setup is better?

To me the weight transfer is about right which suggests the springs are closer to being right than the dampers. Thus shouldn’t the damping be slowed down to match the spring strength?

Am I making any sense here?

The issue is that stock the dampers are valved too stiff (not too soft) for the springs, going with stiffer damping will only make it worse.

Your options are increase the spring rate, or get re-valved shocks that are softer ($$$$$).

[calmtigers]

Originally Posted by RYU

BTW... this car is ok on normal roads. But my commute in downtown LA requires 16 miles of driving on Olympic or Pico blvd. For those who know these roads...I know you feel sorry for me now. The thing is.. my NSX, E36 M3, and S2000 take these roads perfectly fine. The BRZ suspension must just suck in these situations.

I know those roads too well, I literally decided to carpool with a girl rather than deal with that headache.

However, i think someone hit the nail on the head with air ride. Yes it's one of those cult hated things but it would allow for most adjustability and comfortability (though I've only ridden in air ride trucks )