Track Suspension

[kngrsll]

Originally Posted by Loren

But, all you need is a strap or cable or chain or something to keep the axle assembly from falling low enough to unseat the spring. Sort of the same thing we're already doing with the shock. That's exactly what the shock does at full extension, it limits the droop of the axle. Adding a droop limiter takes that load off of the shock, which is probably a good thing.

great idea, someone brought it up last week i think

Originally Posted by largeorangefont

I already brought this up a couple weeks ago in the Tokico HTS thread.

You can use a tow strap to limit down travel, and it will be lighter than all that extra crap to hold the spring in. Pro Comp makes straps in various lengths for off road trucks.

I was also thinking of a bolt in perch on the torsion axle, but since there is a hole in the middle, make the lower perch adjustable.

LOL yep, thanks for the suggestion!

so now, we can use a shorter spring for a higher rate, as long as we use a strap to shorten the droop! 400 lb rear springs, here we come?

[largeorangefont]

Originally Posted by kngrsll

great idea, someone brought it up last week i think



LOL yep, thanks for the suggestion!

so now, we can use a shorter spring for a higher rate, as long as we use a strap to shorten the droop! 400 lb rear springs, here we come?

If you can find a 400# spring of the right diameter and length, you could do it now with no perches. You will definately need straps for those HTS shocks.

Assuming the spring can sit on the stock perches,you can roughly figure out the length needed measuring the length of your current spring with the car on the ground. Then take the weight of the car, and the weight distribution, and figure out roughly how much weight is on the rear tires. Remember you have 2 rear springs so you want to devide this weight by 2. You know it takes 400lbs to compress the spring 1 inch. Do the math and you will have your approximate free length. It should only be around an inch more than the measurment of the compressed spring. There is not a lot of weight back there.

Strap placement will be tricky, so you will need to figure that out. You would set the droop so that the spring could never fall out if the rear suspension were to become unloaded or if an inside rear tire left the ground in a corner. That type of full articulation is actually more droop than if both rear wheels were off the ground. If you set the droop such that the spring is unloaded, but still touching the perches, you should be fine. You have the "dome" of the perches to hold the spring in and give you a little extra buffer in a 3 wheel situation.

Unfortunately with stiff spring like that you wont be left with much rear droop. This is fine for the racetrack, but may be a little harsh on the street.

[Tamago]

Originally Posted by largeorangefont

There is not a lot of weight back there.

say what, 40% of 2300lbs? 920lbs total, split that and you have 460 lbs each spring.

so you'd get 1.15" of compression at rest..

[largeorangefont]

Originally Posted by Tamago

say what, 40% of 2300lbs? 920lbs total, split that and you have 460 lbs each spring.

so you'd get 1.15" of compression at rest..

Yea if that...

[Tamago]

Originally Posted by largeorangefont

Unfortunately with stiff spring like that you wont be left with much rear droop. This is fine for the racetrack, but may be a little harsh on the street.

if i cross from a parking lot to the street at a diagonal angle, i'm two-wheeling every time. i've gotten used to it, but have had strangers at the gas station comment on it lol

[largeorangefont]

Originally Posted by Tamago

if i cross from a parking lot to the street at a diagonal angle, i'm two-wheeling every time. i've gotten used to it, but have had strangers at the gas station comment on it lol

It is not that, it is dips at speed we are talking about. Potholes are a good example. At speed a softer, longer travel suspension would allow the wheel to drop into the hole and on hole exit the suspension would absorb the impact with bump travel.

Lets say you hit a pothole with yout right rear. With no droop the entire weight on that wheel falls into the pothole, you feel the car drop into the hole. Upon exit of the pothole, that wheel would reload the left front wheel, and you would feel the wheel and car lifting up and out of the hole. It would feel very jaring.

[Tamago]

Originally Posted by largeorangefont

It is not that, it is dips at speed we are talking about. Potholes are a good exampl. A softer, longer travel suspension would allow the wheel to drop into the hole and on hole exit the suspension would absorb the impact with bump travel.

Instead the entire weight on that wheel falls into the pothole, and pushes that weight back up upon exit of the pothole. It would be very jaring.

just drive really fast and float over the potholes? ;)

[Loren]

Originally Posted by largeorangefont

It is not that, it is dips at speed we are talking about. Potholes are a good example. At speed a softer, longer travel suspension would allow the wheel to drop into the hole and on hole exit the suspension would absorb the impact with bump travel.

Instead the entire weight on that wheel falls into the pothole, you feel the car drop into the hole. This takes weight off the opposite front tire and slams that weight back up and onto the opposite front again upon exit of the pothole. It would feel very jaring.

The solution to that would be a progressive spring, or a stack of springs designed to be progressive. I figured out how to do this on my Miata, but ultimately decided it was too expensive to bother with. You have to buy two springs instead of just one, and then you have to buy the couplers to go between them (unless you're really confident that your math is correct, then you could just weld them together).

For the back of the Yaris, if you did something like stacking a 6" 400# spring with a 2" 200# spring, the low rate spring would be mostly compressed under the weight of the car and as soon as you entered a turn, the outised spring would coil-bind and give you the 400# rate that you want for cornering. The inside spring would extend, giving you the full effect of the two springs, which nets a nice, soft 133# rate that would be in effect when that wheel came down to smooth things out.

Ground-Control sells the springs you'd need to do that if you wanted to go with 2.5" ID springs.

[Tamago]

Originally Posted by Loren

Ground-Control sells the springs you'd need to do that if you wanted to go with 2.5" ID springs.

ground control utilizes eibach :) so you may be able to source them cheaper thru someone else?

[largeorangefont]

Originally Posted by Tamago

ground control utilizes eibach :) so you may be able to source them cheaper thru someone else?

Hypercoils may be cheaper.

I used to know a place that sold lightly used springs from race cars, eibach and hypercoils for cheap. I'll see if i can dig it up. They wanted like $30 per pair.

[largeorangefont]

Originally Posted by Loren

The solution to that would be a progressive spring, or a stack of springs designed to be progressive. I figured out how to do this on my Miata, but ultimately decided it was too expensive to bother with. You have to buy two springs instead of just one, and then you have to buy the couplers to go between them (unless you're really confident that your math is correct, then you could just weld them together).

For the back of the Yaris, if you did something like stacking a 6" 400# spring with a 2" 200# spring, the low rate spring would be mostly compressed under the weight of the car and as soon as you entered a turn, the outised spring would coil-bind and give you the 400# rate that you want for cornering. The inside spring would extend, giving you the full effect of the two springs, which nets a nice, soft 133# rate that would be in effect when that wheel came down to smooth things out.

Ground-Control sells the springs you'd need to do that if you wanted to go with 2.5" ID springs.

I have not taken any measurments, but I dont think there is enough room to do that with 2.5 ID springs as we would need perches as well. I think the whole thing would coilbind over bumps, which is fixing one problem and creating another. I would rather have a droop issue than an compression issue. I have no problems living with the horrible street manners of a track spring and damper setup however.

That would absolutely solve the problem if there was room to make it to work.

[Loren]

Originally Posted by largeorangefont

That would absolutely solve the problem if there was room to make it to work.

Nah, I don't have much problem with it, either. :) I just run the rear shocks softer on the street and call it good.

I just wanted to throw that out there as an example of what can be done if a person were so motivated.

[Loren]

Originally Posted by largeorangefont

if an inside rear tire left the ground in a corner

If? This is a situation that anyone who's going this far with their suspension needs to PLAN on. The young guys working course at the BMW club autox I went to last weekend were calling me "tripod" at the end of the day!

The inside rear wheel will be in the air more than it's on the ground unless you're going straight.

[Tamago]

Originally Posted by Loren

If? This is a situation that anyone who's going this far with their suspension needs to PLAN on. The young guys working course at the BMW club autox I went to last weekend were calling me "tripod" at the end of the day!

The inside rear wheel will be in the air more than it's on the ground unless you're going straight.

which is kind of unfortunate as it leaves you with 3/4 of your total grip..

[largeorangefont]

Originally Posted by Tamago

which is kind of unfortunate as it leaves you with 3/4 of your total grip..

There is no weight on that tire anyway in that situation. It will last longer if it is in the air. :)

[Loren]

Originally Posted by Tamago

which is kind of unfortunate as it leaves you with 3/4 of your total grip..

Yes and no. You're optimizing the grip at the front of the car where you need it by taking weight off of the rear of the car. If you want that extra 1/4 of grip that you "lost", run wider tires in the front!

You're not really losing any grip, though. The overall cornering potential of the car goes up. You're taking grip away from the rear where it wasn't needed and transferring it to the front where it was.

[largeorangefont]

Originally Posted by Loren

If? This is a situation that anyone who's going this far with their suspension needs to PLAN on. The young guys working course at the BMW club autox I went to last weekend were calling me "tripod" at the end of the day!

The inside rear wheel will be in the air more than it's on the ground unless you're going straight.

You are right, how silly of me. It should look like an old GTI out there.