There are lot of knowledge here so I thought I'd pick your brains... on a scale of 1-10 what is your rating of the RTA design on EF/EG/DA/DC Honda's?

If we do not relocate mounting points at all, what sort of improvements can we make on the geometry (if any)?

A potential improvement area would be making the RTA lighter while retaining or improving strength. Do you think it's worth the effort/cost?

 

most classes that people run in can not replace the TA. so we do other things to 'improve' things back there.

 

I think welding some extensions on the arm to help correct the geometry when you radically lower the car, is necessary, but seldomly done.

 

From the tests I've done I believe the biggest downfall of the RTA on those chassis is the compliance of the stock rubber bushing. Toe curve tests only tell us what the suspension does in "ideal" conditions but if you look at the bushing throughout it's travel it's not a happy piece of rubber by any means. PCI spherical trailing arm help with compliance and the newer version corrects the roll center as well. The toe curve with stiff springs isn't bad however the issue is when you lower the car to reasonable race ride height you operate in a part of the toe curve that is very toe-in aggressive on compression. If one corrects the roll center to static ride height and utilizes stiff springs the geometry isn't too bad in theory but if the stock rubber bushing is being used the issue of compliance still remains.

Short version: It's a pretty good design but needs a better main bushing to get rid of unwanted compliance.

 

I would completely eliminate the toe arm portion of the trailing arm. Fabricate an upright that can pivot independently of the main pivot point, then use an adjustable link from the main pivot point to the "upright". Then build a toe control rod onto the chassis behind the rear lower control arm mounts. This will allow you to tailor the toe curve to driver preference and it will allow you to bumpsteer the rear of the car. Plus you could play with the anti-squat and anti-dive, to help control weight transfer and help keep the car stable.

 

Jhail250 what's a reasonable race ride height? Would spherical bearings cause more oversteer?

914racer could you possibly draw some schematics or point me in a direction where I could see the fabrcation?

 

914Racer's idea is great and I have heard of something like that being done before. It would take a lot of work and development but if one were to go all out that would be the way to do it.

Generally reasonable race ride height for the rear is 23 inches from the center of the quarter panel to the ground (using stock OD tires). Spherical ball joints don't "cause" oversteer they prevent the suspension making unwanted toe adjustments. In other words to simplify it, they don't cause oversteer they prevent understeer from the stock suspensions nature to toe-in during compression.

 

Is that 23" from the center top part of the rear wheel well?

 

You have to make changes in the suspension to get the chassis down to 3in measured at the rocker panel (not the pinch weld).

 

Center of the wheel well to the ground, that's where I measure from. The proper way to do it is from the pinch welds to the ground but I've found this can be quite time consuming especially when trying to set ride height for the first time.

 

This is beautiful btw, do you have anymore pictures of this setup?

 

No I can't get my hands on more pictures of that car, but one day I would like to own it. If you want to learn more about what can be done with production tubs and an almost endless budget, start researching the old BTCC Supertouring cars. The technology and fabrication that goes into those cars is some of the best in the world.

 

Bravo. Now how do I do this to my crx?

 

Bring money.

 

Is the chassis in the 2 photos Honda, or from another make in BTCC? While those are ideal, I'm more interested in the discussion of improvements that can be made while retaining stock mounting locations...

Anyone recall the old and elusive front knuckle and RTA made by Rayne (or Ryane) Motorsports about 10 years ago? I believe they move the hub up about 2.5" to compensate for the lowering to retain stock geometry. Never ever seen anybody with a set thought. I think they probably only had the prototype set and it never saw production.

 

Both of those cars are Honda Accords. Mounting points on the chassis had to be retained within a circle of three inches, so the chassis points weren't moved much, but the 19in wheels allowed all kind of stuff to be done with the uprights. Having the huge wheel allowed for moving the mounting points on the upright pretty much anywhere within a 19in circle.

I have seen pictures of the lowering arms. Not a bad idea if you they were strong enough. But most people don't care about proper geometry and they just dump the car and deal with bounce.

Not exactly sure I like the trailing arm design. http://www.westshorefabricators.com/Honda/Rear_Arms.htm

The knuckle looks decent.
http://www.westshorefabricators.com/...t_Spindles.htm

 

Lowering the car without actually lowering the suspension seems ideal but who has used these to give us insight? Also how much do they cost?

 

Speaking of rear trailing arm design... I just inspected mine after running the slicks and...

time for wheel spacers.

 

VTECIntegra9: I'm guessing you are rubbing against RTA? What size wheel/offset and slick are you using?

 

im on 15x7.5 rota slipstreams (+38 i believe). 225/45/15 conti takeoffs (hoosier S04) Dont quote me on the offset tho... can't remeber exactly. Stinkycheez is sending me his 5mm spaces so I'll see if it helps out

 

No undesired effects with the exception of the main pivot bushing being a worthless polyurethane cylinder. Polyurethane RTA bushing is the worst thing you can do to your rear suspension.

 

Agreed. Honda designed the rear suspension to move and create a stabilizing effect. For a race car the effect is a little excessive and the heavy cornering forces allow the rubber to deform in a bad way. The nice thing with a custom setup, is the ability to control the toe curve by placing the toe link on the back of the trailing arm and setting the point where you want it. Then you could leave the front link off and tune the new toe link to give the desired effect.

 

914Racer, what are your thoughts on the PCI spherical trailing arm bushings for a race class where extensive modification (like changing pick up points) isn't allowed. Functionally speaking do they work well or are they another thing to throw money at?

 

They are better than nothing, but they are bandaiding the problem that you create by lowering and putting wide sticky rubber on the car. The toe curve gets all screwy when you lower the car radically. You need to be able to adjust the rear toe link to get the geometry back to where it belongs. I would say the easiest way to do that is to move the toe link mount on the trailing arm, but then you get into applying a torque moment as opposed to a linear force to the nose of the trailing arm. If you can build a mount on the body to lower the toe link that would work much better. Its not a complicated arrangement. If your building a race car this one is a no brainer.