any guys here have expirence with the mugen harded rubber rear trailing arm bushing. I like to know if the are noticably harder and stiffer the stock OEM.

 

i had them on front on a eg, much better

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b16chaos &raquo;</TD></TR><TR><TD CLASS="quote">i had them on front on a eg, much better </TD></TR></TABLE>

rear trailing arm bushings on the front?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18 rider &raquo;</TD></TR><TR><TD CLASS="quote">any guys here have expirence with the mugen harded rubber rear trailing arm bushing. I like to know if the are noticably harder and stiffer the stock OEM.</TD></TR></TABLE>

I've used the Mugen RTA bushings in my CRX racecar and to be completely honest, I can't tell the difference from the stock units. On the other hand, if you are looking for a stiff bushing then look no further than the PCI engineering spherical bearing unit. When I switched out the Mugen unit for the PCI bushing, there was a very noticeable in way the rear of the car felt, especially under braking. The stiff bushing doesn't allow the trailing arm to sweep rearwards like it will with the stock or Mugen compliant bushing. As a result, you don't get the toe-in change like you will with the stock setup. Honda purposely designs all of their bushings to deform in such a way under most combinations of pitch, heave, yaw, and roll such that the car's stability is maintaned. For example, in the rear of the car under braking, the stock RTA allows the trailing arm to move rearwards relative to the rest of the car just a little bit. The front of the trailing arm is allowed to move through a small arc by way of the toe link. Similarly, the rear of the trailing arm sweeps through a larger arc thanks to the lower control arm. The net effect of this is to cause a toe-in change under braking. And toe-in in the rear is stable while toe-out tends to be unstable.

 

^Great info. I've been trying to decide which type of trailing arm bushings to go with on 2 different cars: one is an SM EG Civic autocross ride with heavy spring rates, one is a daily driven STS/DSP GSR with softer spring rates built for more track day type of stuff. I have a set of HardRace nearly-solid rubber bushings for one of them I haven't installed yet.

Which did you prefer on your CRX, the Mugen/OEM type or the PCI spherical ones?

 

good info

however, i cant tell from your info how having a stiff bushing on the RTA is beneficial in any circumstance.

any other comments?

 

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

however, i cant tell from your info how having a stiff bushing on the RTA is beneficial in any circumstance.

any other comments?</TD></TR></TABLE>

Sorry, it was late and I forgot to mention that I feel the PCI bushing are a good improvement over the stock or Mugen bushings. First, I run zero static rear toe on the race car and keeping the rear from toeing-in while turning into to a corner under any trail braking means the car turns in better and more predictably. It is a small effect but it is a positive effect on the overall handling. If you do a lot of trail braking and your suspension set-up with a higher front spring set-up than what I'm running and the improvement in your handling will be even more pronounced than it was for me.

 

where can these be purchased from?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18 rider &raquo;</TD></TR><TR><TD CLASS="quote">where can these be purchased from?</TD></TR></TABLE>

Me!

http://www.specialprojectsms.com

In stock now.

Kiwi

 

I've used the Mugen bushings and couldn't tell a noticeable difference from new stock bushings. You will notice a difference if you are changing from old worn out stock bushings though obviously. The spherical bushings from Jeff are an awesome product, that's what i'm using now on the ITR racecar, couldn't be happier, very noticeable difference in stability.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Justin3 &raquo;</TD></TR><TR><TD CLASS="quote">The spherical bushings from Jeff are an awesome product, that's what i'm using now on the ITR racecar, couldn't be happier, very noticeable difference in stability.</TD></TR></TABLE>

The spherical bushings are not recommended for cars that see street and track use, are they? (I mean, are they used strictly on track-only cars?)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Vitt1 &raquo;</TD></TR><TR><TD CLASS="quote">

The spherical bushings are not recommended for cars that see street and track use, are they? (I mean, are they used strictly on track-only cars?)</TD></TR></TABLE>

I wouldn't say they are for "Track use only"...
Several of our customers are using the Spherical Trailing Arm bearings on street cars with no problems. However, I would imagine that the ride would be slightly harsher and for that reason only we don't recommend them for street use.
Performance and comfort don't always go hand in hand.

Kiwi

 

im runing 10k front springs and 7k in the rear with 22mm rear and 24mm front sway bars, my ride is harse as hell.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18 rider &raquo;</TD></TR><TR><TD CLASS="quote">im runing 10k front springs and 7k in the rear with 22mm rear and 24mm front sway bars, my ride is harse as hell. </TD></TR></TABLE>

Then you will notice no difference at... Comfort wise that is.
However, you will notice a marked improvement in handling and predictability on turn in.

Kiwi

 

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

Me!

http://www.specialprojectsms.com

In stock now.

Kiwi</TD></TR></TABLE>

Kiwi's stuff is AWESOME!
Those rear spherical trailer arm bushings are great. They make the car a bit easier to drive and much more stable.
I'd recommend them over the mugen ones any day!

Kiwi will get them right out to ya. He's been a pleasure to deal with every time I've given him a call.
Special Project Motorsports

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">The stiff bushing doesn't allow the trailing arm to sweep rearwards like it will with the stock or Mugen compliant bushing. As a result, you don't get the toe-in change like you will with the stock setup. Honda purposely designs all of their bushings to deform in such a way under most combinations of pitch, heave, yaw, and roll such that the car's stability is maintaned. For example, in the rear of the car under braking, the stock RTA allows the trailing arm to move rearwards relative to the rest of the car just a little bit. The front of the trailing arm is allowed to move through a small arc by way of the toe link. Similarly, the rear of the trailing arm sweeps through a larger arc thanks to the lower control arm. The net effect of this is to cause a toe-in change under braking. And toe-in in the rear is stable while toe-out tends to be unstable. </TD></TR></TABLE>
Eh? Are you sure the rear toes in under braking?

My understanding of the rear suspension is that it toes in under compression and toes out under droop.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Targa250R &raquo;</TD></TR><TR><TD CLASS="quote">
Eh? Are you sure the rear toes in under braking?

My understanding of the rear suspension is that it toes in under compression and toes out under droop.</TD></TR></TABLE>

Yes to your quesion as it relates to the RTA bushing itself. I'm talking specifically about the deflection in the RTA bushing, which allows the toe link and LCA to swing through arcs in a plane parallel to the ground that cause the toe-in. The motion of the RTA due to changes in bump and droop is another story and this requires looking at the kinematics of all the links.

 

Hows this for a thought? Eliminate the toe link and put a solid mount bearing in place of the RTA. Yeah it wouldn't be a perfect dual a-arm but it would be interesting. It would eliminate the toe change.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">Yes to your quesion as it relates to the RTA bushing itself. I'm talking specifically about the deflection in the RTA bushing, which allows the toe link and LCA to swing through arcs in a plane parallel to the ground that cause the toe-in. The motion of the RTA due to changes in bump and droop is another story and this requires looking at the kinematics of all the links. </TD></TR></TABLE>
Ah, I see. I misunderstood what you were getting at.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turboteener &raquo;</TD></TR><TR><TD CLASS="quote">Hows this for a thought? Eliminate the toe link and put a solid mount bearing in place of the RTA. Yeah it wouldn't be a perfect dual a-arm but it would be interesting. It would eliminate the toe change.</TD></TR></TABLE>
I've seen it done but haven't heard any comments on the results. I'd be interested to feel it for myself.

 

Johnny,

Are you sure about the rears toeing IN on braking? The rear wheel is outboard of the lower control arm, the toe-ling, and the RTA. With the braking forces applied to the rear tire, the rear tire will want to swing back towards the rear bumper. The toe-link should be under tension, not compression, so the rear tire should toe OUT due to the compliance of the bushings.

I know that the more toe-in I put on the rear wheels, the more stable it is under braking, and if the PCI gives you more toe out during braking, that'll lead to a less stable braking.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turboteener &raquo;</TD></TR><TR><TD CLASS="quote">Hows this for a thought? Eliminate the toe link and put a solid mount bearing in place of the RTA. Yeah it wouldn't be a perfect dual a-arm but it would be interesting. It would eliminate the toe change.</TD></TR></TABLE>

This is Brian with PCI. I do make a shaft that eliminates the toe link, what happens though instead of toeing in it will toe out under bump. I personally liked it but a lot of people i sold them to didn't. The car rotates well but it snaps out quick if you hit a bump, so you got to be carefull.

 

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

Are you sure about the rears toeing IN on braking? The rear wheel is outboard of the lower control arm, the toe-ling, and the RTA. With the braking forces applied to the rear tire, the rear tire will want to swing back towards the rear bumper. The toe-link should be under tension, not compression, so the rear tire should toe OUT due to the compliance of the bushings.

I know that the more toe-in I put on the rear wheels, the more stable it is under braking, and if the PCI gives you more toe out during braking, that'll lead to a less stable braking.</TD></TR></TABLE>


You are right that the wheel is outboard of the RTA and when braking the toe-link is in tension and the LCA is in compression. And as a result there will be a small deflection in the rubber bushings that ultimately cause a very slight amount of toe-out. Since the rubber bushings in the toe and LCA links are pretty stiff, the deflection in them under braking isn't very much at all, maybe .005 to .010 max.

Toe-link and LCA compliance (Est. toe-out .005 to .010")

However, the net effect braking on the change in toe would not be complete without looking at how the compliance in the RTA bushing allows the toe link, upper control arm, and the lower control arm to move throung an arc about a plane parallel to the ground. If you look closely at the RTA, you'll notice that it is very compliant in the for to aft movement. So it is flexible, much more flexible than the solid rubber bushings in the toe and lower control arms.

During braking, the rearward braking force causes a measurable amout of deflection in the RTA bushing causing the RTA to move rearwords a small amount. For a sample calculation, lets assume the RTA move rearwords 1/8" of an inch. Lets assume that the toe link is about 5.5 inch, and we'll just look at the lower control arm motion (the upper control arm is longer than the toe-link so this will not change the dynamics of what is happening). The LCA is about 13.5 inch long. In addtion, while the LCA is close to perpendicular to the RTA, the toe-link makes about a 75 degree angle to the RTA (in a plane parallel to the ground) with the outside toe-link pivot located farther rearward than the inner pivot.

For an 1/8" rearward movement of the RTA, the toe link moves from the angle of 75 degrees to 73.65 degrees and this causes the front of the RTA to move inwards .036". On the other hand, the LCA moves from an angle of 90 to 89.47 degrees and the RTA at rear moves inward only .0005 inch. So, the front of the RTA moves toward the center of the car roughly .035 inches. This causes the RTA, which is approximately 26 inches long, to toe in about .077 degrees, or with a 23 inch tall tire, this is about .031 inch for each side, or about a 1/16" for each 1/8" rearward movement of the RTA. This is a much larger amount of toe change than what the compliance in the bushing would give us in toe out. The net effect of all bushing compliances is toe-in.

Total Toe-in from RTA bushing flex under braking is .062" (.031" each side) for each 1/8" RTA movement

To find the total toe change under braking, you would have also know the toe curve as a function of droop distance and add this to the toe change from bushing compliance.




Modified by Johnny Mac at 1:54 PM 1/1/2008

 

Thanks, Johnny, for that detailed explanation. I didn't mean to make you respond in such detail, but it did clear it up for me. Although I knew RTA bushing had lots of room for for/aft movement, I didn't realize that the toe-link was at an angle to the RTA. I thought the link was perpendicular to the RTA. Being at an angle sure would make the RTA toe in during braking.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Another Drew &raquo;</TD></TR><TR><TD CLASS="quote">Thanks, Johnny, for that detailed explanation. I didn't mean to make you respond in such detail, but it did clear it up for me. Although I knew RTA bushing had lots of room for for/aft movement, I didn't realize that the toe-link was at an angle to the RTA. I thought the link was perpendicular to the RTA. Being at an angle sure would make the RTA toe in during braking.</TD></TR></TABLE>

Even if the toe link was at 90 degrees, it would still toe-in slightly due to the toe link being shorter than either of the UCA or LCA. Of course, being at 90 degrees, the movement toward the center of the car would be very small such that it would really have almost no toe change under braking. Honda and other manufacturers design their cars to be stable in just about any combination of braking and turning. And in the rear, toe-in is stable while toe-out is unstable and this is why, I believe, that Honda angled the toe-link.