High speed instability

[DCMoney]

I didn't realize that he had changed the design to no longer use the oem subframe. Maybe it will be available both ways? I'm afraid of what the cost may be if it requires a new subframe.
View attachment 28174

Doubtful it'll be offered both ways.

 

[ATMironov]

I would like to say that I will have the new rear suspension production ready for sure by next spring, but time just send to fly by.

We are getting close to finishing the the instructional video cars. This will free up a lot of time.

I have finished redesigning the rear suspension and as soon as the material arrives I will fabricate two prototypes for testing. This should happen in the next few weeks and will give us a better idea of a production time frame.

View attachment 28162

YES!
I'd be happy to test the porotype. Though it might help if the car was running...

 

[r3drckt]

What's disappointing is the lack of a tow hitch receiver on that redesigned subframe How will @Ross tow his jet ski(s) to the lake?

 

[jennam]

I would like to say that I will have the new rear suspension production ready for sure by next spring, but time just send to fly by.

We are getting close to finishing the the instructional video cars. This will free up a lot of time.

I have finished redesigning the rear suspension and as soon as the material arrives I will fabricate two prototypes for testing. This should happen in the next few weeks and will give us a better idea of a production time frame.

 

[jayrolls]

A couple of things...

First, my tie rods are actually angled up just slightly toward the wheel. However, I'm unsure how to get them any lower.

Which leads to my next issue, my set up is not exactly as the factory setup is, as I have the tie rod mount in the upper hole in the front, and the lower hole in the rear. This is going to put the actual tie rod end link at the lowest position possible, unless I drill some additional holes.

The only thing I could do would be to swap the aluminum Mount brackets from left to right, since they are actually slightly tapered. That would put the tie rod a little lower, and therefore a little more level.

I thought the tie rod end mount was supposed to be in the same set of hole. Either the upper two or the lower two?

 

[Gtstorey]

There is post somewhere with Lonny saying that the multiple holes are to be able to adjust for bump steer. I'm not sure that it matters which two you use since it would depend on what you needed to reduce/eliminate bump steer. I think the arm will bolt diagonally, but I'm not totally sure I actually inserted the bolt, since at some point I was moving the arm with one bolt and a clamp to measure the bump steer, and then drilled a new hole when the bump steer was virtually zero below the lower hole. This may change the Ackerman(?) a little, but I don't think it was much.

 

[Chubbs]

I thought the tie rod end mount was supposed to be in the same set of hole. Either the upper two or the lower two?

It's been several months since I assembled it, but from memory, mine would only fit in diagonal holes. If I try to put it in both the top or both the bottom holes, the holes didn't line up with the tie rod end brackets.

I unbolted the shock, and was able to freely swing the suspension through its travel. At the lower end of the travel, with the suspension fully drooped, The wheels are slightly toed out. As the suspension compresses, the wheels toe in. At about mid travel, they stop swinging inward, and begin toeing out again.

I think my issue is that my suspension is at the minimum point, (or max toe in) as it's sitting on the ground. So, any extension or compression of the suspension causes it to toe out more.

Because the tie rod is longer than the A arms, and because its height is in the middle between the two A arms, it seems to me that it is impossible to completely eliminate bump steer. Am I looking at this wrong? I just don't see the geometry that would allow it to stay constant throughout the suspension travel. It seems like the best we can do is try to minimize it. Even that seems difficult without drilling additional holes, as I cannot get my tie rod any lower. The best I could do would be to raise the front suspension ride height.

Edit....I looked again, the issue is mine is above the neutral point, so any additional compression results in a pretty severe toe out. Lowing the tie rod should help. It will still toe out, but will be minimal since it's in the middle of the travel. Now, how to lower the tie rod bracket? I guess drill holes.

 

[jayrolls]

It's been several months since I assembled it, but from memory, mine would only fit in diagonal holes. If I try to put it in both the top or both the bottom holes, the holes didn't line up with the tie rod end brackets.

I unbolted the shock, and was able to freely swing the suspension through its travel. At the lower end of the travel, with the suspension fully drooped, The wheels are slightly toed out. As the suspension compresses, the wheels toe in. At about mid travel, they stop swinging inward, and begin toeing out again.

I think my issue is that my suspension is at the minimum point, (or max toe in) as it's sitting on the ground. So, any extension or compression of the suspension causes it to toe out more.

Because the tie rod is longer than the A arms, and because its height is in the middle between the two A arms, it seems to me that it is impossible to completely eliminate bump steer. Am I looking at this wrong? I just don't see the geometry that would allow it to stay constant throughout the suspension travel. It seems like the best we can do is try to minimize it. Even that seems difficult without drilling additional holes, as I cannot get my tie rod any lower. The best I could do would be to raise the front suspension ride height.

I wish you luck, mine seem to line up good. Have you thought about using a bump steer kit. This one is for a mustang, but it gets the idea.

 

[Gtstorey]

I spent some time looking for a bump steer kit that would work and didn’t have any luck. Even finding threaded adapters to make rod ends work didn’t seem available without a lot of work or custom machining.

 

[Ross]

I too looked for a bump steer kit. No luck. I am now considering modifying the rack to move up, or the ball joint arm to move down.

 

[Rttoys]

If it matters, I replaced my front shocks with 1” taller ones. I mostly wanted a tad more ground clearance, but there’s also a little more adjustability and seems to ride a little better. You can look at the rod levels to compare. I took angle measurements but forgot exactly what they are

 

[Gtstorey]

I think drilling a new hole in the hub bracket worked pretty good for being simple but it doesn’t allow for adjustment if I make major changes to the alignment.

 

[Chubbs]

If it matters, I replaced my front shocks with 1” taller ones.

Beat me to it. What I really need is to increase the ride height on the front just a bit. But after looking at the qa1 shocks, it doesn't look like they are adjustable for ride height at all, other than spring preload.

Is that true? does anybody know if the front ride can be adjusted besides preload?

 

[Scott #321]

I suppose I need to check mine out more as I have not had any stability issues at speeds around 70. I am running -9.5deg castor -.5 camber, and 3/16 front toe empty on 255's and maybe that is just making the bump steer less noticeable. I do go over a very rough set ot train tracks but slow to 50-55 for them

 

[Andrewlee92]

I would like to say that I will have the new rear suspension production ready for sure by next spring, but time just send to fly by.

We are getting close to finishing the the instructional video cars. This will free up a lot of time.

I have finished redesigning the rear suspension and as soon as the material arrives I will fabricate two prototypes for testing. This should happen in the next few weeks and will give us a better idea of a production time frame.

View attachment 28162

How much less will the new rear end weigh than. The cobalt one

 

[Lonny]

I'm hoping for around 20 pounds.

 

[Andrewlee92]

I'm hoping for around 20 pounds.

Is that just the subframe or only 20lbs lighter than the stock subframe, control arms, knuckles, and toe bar

 

[Lonny]

For everything but I'm just guessing.
The new tubular subframe model shows to be 29 pounds and I think a stock subframe is around 41 pounds.
The new knuckles and control arms are possibly lighter than stock.
We are eliminating the toe link rack and the inner and outer tie rods from the rear with the new setup.
When we get the new prototype installed I will get a before and after weight of the Goblin.

 

[Desert Sasqwatch]

I know how to get the stock frame under 38 pounds.

 

[Rttoys]

Beat me to it. What I really need is to increase the ride height on the front just a bit. But after looking at the qa1 shocks, it doesn't look like they are adjustable for ride height at all, other than spring preload.

Is that true? does anybody know if the front ride can be adjusted besides preload?

No, not adjustable ride height. Going with the 1” taller shock got me a just under 3/4” raise up front. BUT I was using spring preload to raise the front to where I wanted it, on the old shocks. So with the old shocks (kind of) maxed out, it sat as high as it could with still having movement and rode rough. Now with the 1” taller ones, I can use the springs correctly, getting the desired preload I feel works best for my liking with a good bit of adjustability, while having a better stance that I like. You’re results may vary.