Rear suspension

[Brentorius]

Today I jacked up the yaris with the rear tires off and did not see any scratches on the gas tank. I did not see any interference issues with the suspension either (at full sag). I then individually compressed each side with another jack and can not see where it would be hitting. I haven't heard any odd noises in a while, but the tein springs are very compressed at static ride height and maybe the noise is the coils? There are about 6 coils touching.

[fmicle]

Yep, that's what I think as well, the noise must come from the coils themselves and not from the axle touching anything. The Toyota engineers who designed this could not have overseen such a simple thing...

If you think about it, by moving the pivot point up, you are actually increasing the distance of the axle from the gas tank, which is above the pivot point. I am personally not worried about any damage with this configuration, but whenever I'll have some time I will jack up the car, remove the springs and the shocks and try to swing the axle all the way to see if it could theoretically hit anywhere, just like Loren suggested a while ago. Until then I'm not losing any sleep over this

Another thing that crossed my mind: if you think about it, the springs are not compressed between two parallel planes (as they are in the front), but they are compressed between two planes at an angle. I'll try to illustrate this in a drawing below. What I'm trying to say is that if you push the spring straight forward, it's unlikely that the coils will slip or otherwise rub unevenly, but if you compress the spring at a certain angle, you may get some slipping - hence the clunking noise. By moving the axle up that angle will increase considerably, I was actually thinking how come the springs stay in there and don't just snap out

I have exaggerated the angles in my drawing to make the point, because I believe depending on the drop, moving the pivot point up is just a necessary correction. If the spring drop is less than the distance between the two pivot points, then the angle will be slightly increased (or decreased if you measure it against the vertical).

[Brentorius]

When I first relocated the pivot point, I moved the axle through its range of motion to free up the bushings before I installed the shocks. I did not see any problems...

[Loren]

Originally Posted by Brentorius

When I first relocated the pivot point, I moved the axle through its range of motion to free up the bushings before I installed the shocks. I did not see any problems...

This is what I suggested that someone do a few weeks ago. Answers the clearance question definitively. If you were able to completely bottom out the suspension without hitting anything, then there is no clearance issue.

[evo165]

Originally Posted by fmicle

Yep, that's what I think as well, the noise must come from the coils themselves and not from the axle touching anything. The Toyota engineers who designed this could not have overseen such a simple thing...

If you think about it, by moving the pivot point up, you are actually increasing the distance of the axle from the gas tank, which is above the pivot point. I am personally not worried about any damage with this configuration, but whenever I'll have some time I will jack up the car, remove the springs and the shocks and try to swing the axle all the way to see if it could theoretically hit anywhere, just like Loren suggested a while ago. Until then I'm not losing any sleep over this

Another thing that crossed my mind: if you think about it, the springs are not compressed between two parallel planes (as they are in the front), but they are compressed between two planes at an angle. I'll try to illustrate this in a drawing below. What I'm trying to say is that if you push the spring straight forward, it's unlikely that the coils will slip or otherwise rub unevenly, but if you compress the spring at a certain angle, you may get some slipping - hence the clunking noise. By moving the axle up that angle will increase considerably, I was actually thinking how come the springs stay in there and don't just snap out

I have exaggerated the angles in my drawing to make the point, because I believe depending on the drop, moving the pivot point up is just a necessary correction. If the spring drop is less than the distance between the two pivot points, then the angle will be slightly increased (or decreased if you measure it against the vertical).

Bingo on the springs. As i mentioned it on my Tokico structs thread(post number 7).

http://www.yarisworld.com/forums/showthread.php?t=24722

[detroiter]

So I'm wondering what others opinions are on if you keep the springs tightened up while you have it in the upper bolt position for quite some time, if you decide to lower it back to the lower bolt position will the springs return to their standard stiffness and reaction or will the springs be permanently compressed because of being tightened down for so long from being in the upper position?

In other words, will the springs rate and reaction be ruined because of being compressed for so long? Almost like if you take a slinkee and stretch it out too much, it never returns to it's original state. But this case being the opposite. Being compressed for so long, maybe it won't return to it's normal state?

[docB]

The spring rate is determined by material properties, number of coils, diameter of the coils, diameter of the wire. Some think color makes a giant difference but that is for another post... Moving the beam may cause a slight change in installation height, but the spring rate will remain constant.

[ozmdd]

To answer an earlier question about setup, I am running NF210's on OEM struts/shocks w/ a TRD sway bar. The clunking never went away after several months, but closer inspection seems to indicate that the "clunking" is primarily within the springs themselves (as speculated by several posters), and possibly at the swaybar mount, though that is hard to say since road crap keeps interfering. We have some good weather now, so I'm going to put it through some rough roads and sharp curves later today and immediately lift it and inspect for marks after chalking the supected rub areas.

I'm installing coilovers this week after that test, so its a bit of a moot point, but others may find the info useful.

I AM positive that the axle is free of interference throughout its full range of motion, unlike what I initially thought.

Performance-wise, there is no doubt that this improves turn-in for autocross situations. I was very inpressed with the results at this weekend's event, even on cold tires/concrete.

[fmicle]

Originally Posted by docB

The spring rate is determined by material properties, number of coils, diameter of the coils, diameter of the wire. Some think color makes a giant difference but that is for another post... Moving the beam may cause a slight change in installation height, but the spring rate will remain constant.

+1, I don't agree that the springs are more compressed with the axle beam moved up. The are just compressed at a different angle and the forces acting on them are slightly different. It's the weight of the car that compresses the springs, not the position of the axle beam...

[fmicle]

I was going to replace my rear brake lines today, so I had the wheels off and noticed this. I don't know if it has anything to do with this suspension mod, since I'd think this is rather affected by the length of the springs, more than the axle geometry, but I might be wrong. Anyway, it's probably good to keep this in mind. I suspect this happened only a few weeks ago when I took a longer trip with 4 adults in the car, since the damage is not too bad. You may just want to check this from time to time when you happen to be under there.

On the positive side, I saw absolutely no contact with the gas tank and just a very tiny tiny contact point on the exhaust pipe

Right hand side:






Left hand side:

[detroiter]

I never noticed that under there, which line is that?

[Loren]

Brake line!

Doesn't look like enough contact to be a problem, especially if it only happens with 4 people in the car, but it warrants further attention. I'll give my car a close look next time I'm under there. (it's in the stock axle configuration with lowering springs... but it's not super-low, and the springs are really stiff, so I suspect I won't see any rubbing on mine)

[fmicle]

^ What springs do you have Loren? I have the Progress, I think they have a 1.4" drop, both front and back.

I was thinking about gluing some rubber piece, like a bump stop or something to the frame, to prevent the axle from traveling all the way, what do you think, could that work?

[Loren]

I have non-standard springs that were never intended to be on a Yaris. :) Leftovers from my Miata.

Yeah, some sort of bump stop would help. There should be a factory bump stop. Usually fitted around the shaft of the shock. You might check to see if yours are still there and that they weren't cut during the spring install. In any case, you could replace them with a longer bump stop. Progress makes a variety of them, but I don't have any more detail than that.

[fmicle]

Well, I did the install myself and if I remember correctly, the rear bump stops were not too long to begin with. I still cut a little bit, I'd say maybe one third of the original length. Here are the leftover pieces:



These might have just enough thickness to prevent that little bit of scraping and rubbing of the line on the frame. I could probably glue them back on if only I could find them... I think I kept them though... :)

[docB]

Anyone see how the car reacts under extreme braking before and after with this modification? Does the anti-lock kick in more?

[ozmdd]

No change in braking response that I can detect, and I have done several track day and autox's, so I've tested under pretty drastic braking.

I don't have ABS, so can't help you there.

[Maitre_Te_Te]

My rear suspension mod progress!!!! :)