Tyson

EDIT FOR EVERYONE WHO CANT READ:

The below quote from SCC is bullshit, totally false about 88's having "passive" rear steering. There is a slightly more aggressive rear toe curve on 88's that all civics have, and totally washed out once you lower the car.

The lower control arms have nothing to do with it. It is the rear toe link anchor to the chassis being slightly higher. There's no other magic, you don't have to do anything different or be concerned about 88 EF's.


taken from SCC project 88 CRX HF. http://www.sportcompactcarweb....ojcrx/

"The '88 CRX also has a different rear suspension than any other CRX. Honda's unique sort-of-double-wishbone, sort-of-trailing-arm rear suspension uses a toe control link and a compliance bushing in concert to give a passive rear steering effect.

On the 1988 models, the passive rear steering is exceptionally strong, making them extremely nimble. On later years, much of the rear steering was tuned out, bringing handling more in line with conventional front drivers. Many road racers prefer the earlier car's more aggressive handling, but warn that they must be tuned differently. A big rear anti-roll bar that you would use on any other Civic or CRX is an invitation for snap oversteer on an '88. Most CRX experts agree that for a street car, '89 and later cars are preferable."

WTF are they talking about different "passive rear steering" compared to 89-91? its only the lower control arm and shock mounting thats different right? anyone else have a clue and fill me in?

honda parts catalog shows only the 88/89-91 lower control arm difference in design.




on second thought, is it that the lower control arm geometry is actually different? if so, how?


Modified by Tyson at 2:20 AM 11/28/2003

00R101

I don't know if the '88 is different than other honda rear suspensions. They all have passive rear steer to some extent.

Basically, if you look at the suspension and if all the bushings could only move in one plane then the suspension could not move. But the bigger bushings (like #26 and #29) move on more than one axis and have different flex through the arc of travel. So in effect they become moveable suspension mounting points. In other words, the ends of the wishbones that would normally attach directly to the car are not fixed in space relative to the car. Honda can tune the bushing deflection on these bushings and completely change the motion of the rear end.

Passive steering is caused by the pull or push exerted on the suspension by part #15 as the suspension moves through its arc.

Apparently in '88 they tuned it for extra passive rear steer (probably by softening the bushings at #26 and #15 and stiffening at #29) Also, your diagram shows a part that I am not familiar with on the ITR (which has an almost identical layout) and that is parts #42 20 and 23.

I know the '93 delSol had too much passive rear-steer; partially due to too much body flex. For '94 and beyond they modified the shell and bushings to reduce it. The '93 rotated better but had too much of a tendency to snap oversteer.

Regards,
Alan

89civicdx

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 00R101 &raquo;</TD></TR><TR><TD CLASS="quote"> Also, your diagram shows a part that I am not familiar with on the ITR (which has an almost identical layout) and that is parts #42 20 and 23.
</TD></TR></TABLE>

I BELIEVE 42,20 & 23 are the air deflector to help cool the rear drum....I think.

Jaker

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 89civicdx &raquo;</TD></TR><TR><TD CLASS="quote">

I BELIEVE 42,20 & 23 are the air deflector to help cool the rear drum....I think.</TD></TR></TABLE>

Its actually a debris shield to prevent the bolt threads of the various fasteners from being damaged.

743power

I always heard that the LCA's are what gave that passive steering effect. Since they use shocks with an eye for a bottom mount and not a fork, like most other us hondas. I dont understand this concept at all, but in 90-91, they changed to a different LCA and rear shock with fork bottom mount because too many people were having the rear ends swing out on them.

Where's the suspension gurus when you need them?

AcidGord

This explains a bit. I recently swapped my EG suspension out for a Integra Type-R setup and the rear LCAs are just like this. The strut has the sleeve/bushing on it rather than a fork. Someone told me this added 'passive rear steering' but I had no idea what they were talking about and they didn't back it up with an explanation.

http://spoon.org/civic/pics/ITR-LCA.jpg

Haven't had the chance to really try it out though, won't until May now. Ugh.

CRX Lee

The rear lower control arms don't have anything to do with the "passive rear steer" tendency on the rear of the '88 and '89. The issues are actually not based on any parts that you can move from one car to another. The difference is in the location on the body shell where the mounting point is located slightly differently on a vertical plane. Because of that pickup location at stock or near stock ride height, the car got more bump steer during body roll. I was told by a Honda motorsports guy that some people in the Firehawk days actually made an adjustable piece on the end of the trailing arms so they could have different adjustments and would test and tune with it.

I always have thought this advantage/disadvantage was eliminated as soon as guys spring their cars stiffer and lower them. Once you've changed from that stock geometry and re-align the car then I think you have erased that tendency. I've had a pair of '88s and more '89s and I have never seen that big a difference in performance street or race form. The biggest difference is the 100 lbs. or so weight difference between the two years. They added a lot of weight and chassis structure when they moved the seatbelt from the car to the door. It's thicker and heavier well back into the quarter panel and can be a bitch to cut out.

The lower control arm thing I beleive is just an anomole between the years. They have used that same stamped control arm in Taiwan and parts of Asia for a long time on base model cars. That is how I tracked down the part number for the externally adjustable KONI Sport Type R rear shock we now sell.

j-rho

Good info man - minor correction in that the '89's still have the seatbelt mount on the B-pillar; it moved to the door in '90.

CRX Lee

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jaker &raquo;</TD></TR><TR><TD CLASS="quote">
Its actually a debris shield to prevent the bolt threads of the various fasteners from being damaged.</TD></TR></TABLE>

I had always thought those were not-very-good brake ducts but you are right. I've got the rear wheel off my drum braked racecar and looked at it closely. I looked it up in the parts book and they call it "Protector". Only problem is that the bolts they are trying to protect are some of the few nearly guaranteed to break on a Honda. Forget this bolt on an '88 lower rear control arm, I'd guess the ITR will be bad there too.

CRX Lee

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jzr &raquo;</TD></TR><TR><TD CLASS="quote">Good info man - minor correction in that the '89's still have the seatbelt mount on the B-pillar; it moved to the door in '90.</TD></TR></TABLE>

We are both right but I am more right than you are . They switched the seatbelt on the Si and the DX CRX for '89 (I own two '89s and 1 '88s Si currently) but kept it on the HF through '89 and changed for '90.

jsi

Also, wouldn't the toe control be affected somewhat by LCA bushing compliance, #24s on the 89+ and #25 on the 88? I'm guessing the different bushing design/stiffness would affect handling also...

CRX Lee

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jsi &raquo;</TD></TR><TR><TD CLASS="quote">Also, wouldn't the toe control be affected somewhat by LCA bushing compliance, #24s on the 89+ and #25 on the 88? I'm guessing the different bushing design/stiffness would affect handling also...
</TD></TR></TABLE>

Those bushings are different because of the different shape requirements of the two different control arms. The bushings themselves are very similar in functional size and I'd bet the rubber compounds are the same. The leading edge of the trailing arm is going to be easier to steer by. Much bushing design difference and I think they'd wear out faster.

Tyson

Lee, thanks for the info. very interesting that the actual body mount would be different. i wonder if the change is visible without any measuring tools.

Jack Black

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tyson &raquo;</TD></TR><TR><TD CLASS="quote">Lee, thanks for the info. very interesting that the actual body mount would be different. i wonder if the change is visible without any measuring tools.</TD></TR></TABLE>

In this thread, Scott (RR98ITR) discusses the effect of the toe control link and mentions that the toe curve could be "re-zeroed" by raising the body-mounted pivot point after lowering the car. From Lee's comments, it seems like the 88-89 CRX has a different inner toe link mounting point in order to change the part of the toe curve that the suspension operates in.

daigo

Yes that's correct. The location of the body side mount of the toe arm is at a different height in relation to the ground. We have a custom bracket on our 90 Road Race CRX that gives us the ability to move the point thus adjusting the arc of the rear tire in a corner. By adjusting the height we can tune the amount of toe in gain we have in a corner.
BTW, good to hear you're still involved Lee, it's been a while!

Tyson

mind sharing a picture of this mount? that would really help. thanks.

DB2-R81

Have a look at the "How the rear end of the DC2 chassis works against us..." post, I put up some pictures for you.

crxybaby

Daigo, and DB2, good to see some other canucks on here from the frigid north. Daigo which car do you race? I am just up the river from you in the town where the road course is. I have the '88 # 12 black crx.

Tyson

EDIT FOR EVERYONE WHO CANT READ:

The below quote from SCC is bullshit, totally false about 88's having "passive" rear steering. There is a slightly more aggressive rear toe curve on 88's that all civics have, and totally washed out once you lower the car.

The lower control arms have nothing to do with it. It is the rear toe link anchor to the chassis being slightly higher. There's no other magic, you don't have to do anything different or be concerned about 88 EF's.