Track Suspension

[largeorangefont]

You will need more than the useless rear shock bushing brace if you go with a coilover setup on the rear shocks.

you could groove the rear shocks and run compression rings for coilover sleeves. That is what I run on my Cobra in the rear.

With a stiff rear sway bar and coilovers you could punch right through the upper shockmount. You would at least need delrin upper bushings and possibly weld or bolt on a steel plate for reinforcement.

[Tamago]

Originally Posted by largeorangefont

You will need more than the useless rear shock bushing brace if you go with a coilover setup on the rear shocks.

you could groove the rear shocks and run compression rings for coilover sleeves. That is what I run on my Cobra in the rear.

eye-to-eye shocks can be modified to accept spring perches :) if my Ksport perches don't work out that'll be my next step.

[largeorangefont]

Originally Posted by Tamago

eye-to-eye shocks can be modified to accept spring perches :) if my Ksport perches don't work out that'll be my next step.

Yea that would make things significantly easier, you would probably have to get them revalved for this application, but that is not horrible.

[Loren]

Originally Posted by largeorangefont

You will need more than the useless rear shock bushing brace if you go with a coilover setup on the rear shocks.

you could groove the rear shocks and run compression rings for coilover sleeves. That is what I run on my Cobra in the rear.

With a stiff rear sway bar and coilovers you could punch right through the upper shockmount. You would at least need delrin upper bushings and possibly weld or bolt on a steel plate for reinforcement.

Yeah, I was thinking the same sort of thing. That upper mount wasn't made to carry any weight. Even putting in a reinforcement at the top could just be moving the weak point to lower on the tower where something else will bend or break under fatigue. Now, if the car had a full rollcage and you could tie into that... that could work.

[kngrsll]

Originally Posted by Loren

Yeah, I was thinking the same sort of thing. That upper mount wasn't made to carry any weight. Even putting in a reinforcement at the top could just be moving the weak point to lower on the tower where something else will bend or break under fatigue. Now, if the car had a full rollcage and you could tie into that... that could work.

sounds like a great excuse to me :rofl:

[largeorangefont]

Originally Posted by Loren

Yeah, I was thinking the same sort of thing. That upper mount wasn't made to carry any weight. Even putting in a reinforcement at the top could just be moving the weak point to lower on the tower where something else will bend or break under fatigue. Now, if the car had a full rollcage and you could tie into that... that could work.

Yea.. the shock mount might need to be boxed in completely. If I was going this route, that is what I would do.

[kngrsll]

Originally Posted by largeorangefont

You will need more than the useless rear shock bushing brace if you go with a coilover setup on the rear shocks.

you could groove the rear shocks and run compression rings for coilover sleeves. That is what I run on my Cobra in the rear.

With a stiff rear sway bar and coilovers you could punch right through the upper shockmount. You would at least need delrin upper bushings and possibly weld or bolt on a steel plate for reinforcement.

do you have a link for this process? If not, could you explain more about grooving the shocks?

My idea is similar i think, i thought about simply welding on a collar to set the spring perch on.

[Tamago]

Originally Posted by kngrsll

do you have a link for this process? If not, could you explain more about grooving the shocks?

My idea is similar i think, i thought about simply welding on a collar to set the spring perch on.

i can groove them at my shop :)

however, Gordon at koni does not recommend doing this, as the outer shell of most shocks is not thick enough to withstand grooving/welding unless already equipped in such a way.

[largeorangefont]

Originally Posted by kngrsll

do you have a link for this process? If not, could you explain more about grooving the shocks?

My idea is similar i think, i thought about simply welding on a collar to set the spring perch on.

You dont want to be welding to shock bodies.

Pages 4-7 deal with the grooved shock body and the spirolock ring that hold on the coilover sleeve.

http://www.maximummotorsports.com/co...p/MMCO-4r6.pdf

[cali yaris]

I'll take pics of the Silk Roads on my car.

[kngrsll]

what do you guys think of using these? you can select rate, but probably cant adjust height though. I think i measured the rear spring to be 5 1/2" in diameter.

http://www.dansracingsupply.com/AFCO.htm

http://www.afabcorp.com/AFCO_Dynatec...t_Conventional

So if you can figure out what spring will allow you to have a decent height, and then you can get collars for the front, you are good to go. you wont have rear height adjustability, but you could use a good strong rate.

[Tamago]

Gordon at koni said 9" would be good for my setup, and i'd imagine that a 9" travel shock would work for y'all in the back as well

[kngrsll]

Originally Posted by Tamago

Gordon at koni said 9" would be good for my setup, and i'd imagine that a 9" travel shock would work for y'all in the back as well

got any aftermarket springs around you can measure?

[Tamago]

Originally Posted by kngrsll

got any aftermarket springs around you can measure?

not currently, i'm at home :)

[kngrsll]

does that sound doable though? i know normally, you can trim up to 1 coil off a spring and without affecting its rate, so you could do that if you needed to, or if its too short, you can spring rubber to raise the height.

[Tamago]

Originally Posted by kngrsll

does that sound doable though? i know normally, you can trim up to 1 coil off a spring and without affecting its rate, so you could do that if you needed to, or if its too short, you can spring rubber to raise the height.

i'm currently on xB Tein S techs with one coil removed. car is stiff, but strut/shock rates are garbage (stock)... i traded my coilovers for boost back in late 2007

[Loren]

Here's a tip: If you're looking for a shock that's designed to be a "load bearing member", look at Miata shocks. A lot of mechanics think they are struts because that's what they look like, but due to the Miata's double-wishbone suspension, they carry no side load.

Anyway... look at something like the rear KYB AGX for a 94-97 Miata. 8-position damping adjustment, and the spring perch can be hammered off to reveal a retaining ring. You can put anything you want around that shock to be supported by that ring. Of course, you'd still have to deal with whether or not the Yaris rear upper shock mount is sufficient to support the weight of the car.

I like the idea of fitting larger diameter race springs in place of the stock rear springs. I almost made that suggestion a while ago. There are several diameters available, circle track guys use them for building those old school stock cars. Just need to figure out what diameter will fit, or make some perch adapters to make something fit.

BUT, the problem comes when you want a stiff spring. Let's take my 7kg for example. I think better in pounds (and most non-JDM race springs will be spec'd in pounds, anyway), so let's call it 400 lb/in. The stock springs are something like 120 lb/in. At stock height, let's say that the car has 4 inches of compression travel and 4 inches of droop travel (which probably isn't too far off). So, the spring needs to be able to extend more than 4" under suspension droop to avoid falling out of the perch when you're playing Dukes of Hazzard jumping over RR tracks or lifting a rear wheel while autocrossing.

Stock springs are about 14" long (I'm guessing), and probably compress to about 4", giving them 10" of compression before coil binding (which a stock suspension should be designed to never do). With 8" of total suspension travel, that means that at full compression there's probably an inch left to compress, and at full droop probably an inch of extension left to keep tension on the spring in its perches. Cool.

Now, let's put in a 400# spring. First of all, if we don't change the length of the spring, the height of the rear of the car is going to go WAY up. Just to keep the same height, we need to shorten the spring. With each corner of the rear of the car weighing about 460# (2300 x half x 40%), the stock spring was compressing (assuming 1:1 motion ratio just for the sake of this discussion) 460/120 or 3.8" (hey, there's our 4" of droop travel!). The 400# spring will only compress 1.15", so the 400# spring needs to be about 2.75" SHORTER just to retain stock ride height.

But... at stock ride height, we still have 4" of droop travel. Is the 2.75" shorter spring going to stay in the perch at full droop? To complicate and amplify this problem, who runs stock ride height when they have a modded suspension? Subtract 2" from the ride height, which ADDS 2" to the droop height... ugh. What's holding those springs in now?

There are a couple solutions to this problem. One is with the shocks. Shorter shocks with less droop will limit how far the suspension can droop, possibly more than the factory limit. I think most coilover shocks (especially those intended for the rear of a FWD car) are designed for this, and probably have a "reverse bump stop" built into them. You can't fully rely on this, though, as you do need SOME droop travel for the suspension to work properly.

The other solution is to use a "tender" spring (this is what I did), which is a very low rate spring that stacks on top of (or below, doesn't matter) the main spring and is fully compressed under the weight of the car. At rest, it essentially acts as a spacer. But, when the weight comes off of that corner and the suspension droops, it expands with enough force to keep itself and the main spring retained in the perches. You'll find a lot of so-called "progressive" aftermarket springs are done this way. The coils at one end will be so closely spaced that they are fully compressed under the weight of the car. That's why.

So, you can go with either a super-low rate tender spring like I have... I think the rate is something like 50#, and it compresses flat to about 1/2" height, or you can go with a low rate "real spring" that won't compress as flat. You can either get couplers to fit between the two springs and keep them together, or you can simply weld the two springs together. As long as you go with a tender or "helper" spring that is a low enough rate to be fully compressed under the weight of the car, you can figure it as a "spacer" for static ride height, and figuring the length of the main spring won't be too hard. If you try to build a truly "progressive" spring stack where both springs are still in play, then things get more complicated and adjustable perches make life MUCH easier.

Have I confused anyone yet? I think I confused myself.

The important thing is, for safety, always be sure that your spring has enough tension under full droop to stay in its perch. That can sometimes be a challenge.

[kngrsll]

Ok, totally got what you are thinking Loren...

Now there are also some other issues. In studying this issue, it appears that our "stock" rear springs are "double pig tail" meaning they are fat in the middle, and get smaller near the ends. Wierd terminology, i know. Anyways, the Tanabe springs are 5.5" in diameter in the middle, and about 2.5-2.75" (measured on the car). When the car was jacked up and the rear was fully unloaded, the spring was sitting at 12". it was not able to be pulled out, so there must be a little more length in it, but not much, i would guess its a 12" spring out of the car, its just tight in there. Now there are also two rubber pieces in the back on the top and the rear, so removing one or both of those can reduce the height somewhat. So the free length of the spring must be about 12" to stay in place if the rear suspension becomes fully unloaded, correct?

So what is available for the aftermarket NASCAR folks? Well they carry 2 1/2" or 2 5/8" diameter springs in nearly any length and spring rate you can imagine. Now, if the pig tails end up at that diameter, you could use them i imagine. I would like to try and stay somewhat closer to stock, that can be tried later. So i looked at double pig tail springs, and most of them were 7" inner diameter in the middle, and were very soft, so they are out. Next, i found single pig tail springs. They are flat on the bottom at 5.5" diameter and curl up to the "pig tail" of 2 5/8". They do not come in as many lengths (11, 12, 14 i think is what i came across.) They also don't have as many rates, they highest rate was 300# (as opposed to nearly 1500#s for the others!!) but they are stiff enough for what i want. they come in increments of 25 and 10 #'s.

The reason i believe the single pig tail will work is because the top of the spring is tight, it tapers in like the "pig tail" springs. The bottom though does not, the rear spring seat is a flat tray that is about 7" in outer diameter. Thus i think a flat bottomed, single pig tail spring (5.5" tapering up to 2 5/8") will work. Now the length of the spring i measured on my car is 12", but was still loaded in, so may be a bit more compressed (maybe an inch or two). Remember there are the two rubber insulators on the top and bottom of the spring as well (easily an inch in addition.)

Now we are back to the problem with the spring rates. The length is correct, but the spring may cause the car to sit higher than it needs to. For an easy fix, the rear insulators can come out. As well, you could trim part of the spring off. Or you could just use lower rates then you really want to. Now the rear spring i have now is a Tanabe, so it is a 2.2kg or 123 lb spring. To match the front, you only need to go to 175, that gives you a matching rate front and rear, shifting the balance toward the rear. I think that will easily work. Now what about higher rates? no idea. I would also like to try a 275 lb spring (to make it 175F/275R) to see how it would turn out. This spring may need to have part of a coil trimmed off, while the 175 may actually need a spring rubber to raise it.

So i ordered two sets of springs ($50 a piece with a $40 discount for ordering 4) to try out. i got 12" free length single pig tail springs, 175# and 275#. If they dont work, ill send them back and try something else. After i try this out, we can go from there.

Whew, longest post i think ive ever made lol, hope it helps (and works!)