Ridetech OUT, 4 link Watts-link in.

[David Pozzi]

Let me read up a bit on it. I don't want to give you bad advice. I've tuned rear suspension but not designed any.

[Tweak]

Have measured and locked in my CG with no passengers now, will re-measure with driver and passenger next weekend.

New image shows CG and rear arms at 43% anti squat

Can anyone help me with how to establish front roll centre with my ridetech setup?



FYI
Left Front 415kg (915lbs)
Right Front 416kg (917lbs)
Left Rear 325kg (716lbs)
Right Rear 333kg (734lbs)

As built with zero effort in moving weight around

[stab6902]

I think it's really cool that you're designing your own rear suspension, but I can't help but notice that your design is converging into something that looks a lot like this: https://www.detroitspeed.com/rear-su...d-041703-group

Have you considered the above kit? It's proven and regarded as one of the best in the business. In my mind, DSE is the way to go if you want a 4 link and you're comfortable cutting up your car. I see no reason to reinvent the wheel unless you're just doing it for fun. You seem to prefer a watts link, which you could add to the DSE kit, but I'm not convinced it's worth the additional weight, space, and complexity for this application.

As you've noticed, ridetech had to make a few compromises to make their kit bolt-in. I think they did a great job under those constraints, and it was good business to differentiate their product.

[Tweak]

I think it's really cool that you're designing your own rear suspension, but I can't help but notice that your design is converging into something that looks a lot like this: https://www.detroitspeed.com/rear-su...d-041703-group

Have you considered the above kit? It's proven and regarded as one of the best in the business. In my mind, DSE is the way to go if you want a 4 link and you're comfortable cutting up your car. I see no reason to reinvent the wheel unless you're just doing it for fun. You seem to prefer a watts link, which you could add to the DSE kit, but I'm not convinced it's worth the additional weight, space, and complexity for this application.

As you've noticed, ridetech had to make a few compromises to make their kit bolt-in. I think they did a great job under those constraints, and it was good business to differentiate their product.

Hey
Yes I think your right, but I'm pretty keen to do this myself. The more I understand how it works, the more I can respond to change.
Once I can understand the engineering principles, i think it will resole itself.
As far as having more weight in the rear, probably a good thing with a first gen.
Watts are definitely the best for keeping the axle centered through varied articulation and movement, and not complex with the added bonus of easily being able to change roll centre height in the rear.
Its all new to me and I love learning new stuff.

Cheers for your input.

[Tweak]

My first quick measure, but not sure if I'm on the right path.
My car doesn't sit that low (hence the bump steer issues I had), but be cool to get some input from ridetech on this, does this look similar to there Front Roll centre diagrams?
I forgot to measure my wheel track, so looks a bit off.

[stab6902]

Hey
Yes I think your right, but I'm pretty keen to do this myself. The more I understand how it works, the more I can respond to change.
Once I can understand the engineering principles, i think it will resole itself.
As far as having more weight in the rear, probably a good thing with a first gen.
Watts are definitely the best for keeping the axle centered through varied articulation and movement, and not complex with the added bonus of easily being able to change roll centre height in the rear.
Its all new to me and I love learning new stuff.

Cheers for your input.

Fair enough - there are pros and cons to each. Roll center height can also be adjusted with a panhard bar - whether it's easier or harder than a watts link depends on the individual setup I suppose.

Here's some good reading on the age old watts link vs. panhard bar debate:
http://www.rhoadescamaro.com/build/?m=201102
http://www.rhoadescamaro.com/build/?cat=12

[dontlifttoshift]

What does the math show for roll steer now with the lower links running up towards the front vs the posts on the first page where the lower links were running downhill towards the front?

[Tweak]

What does the math show for roll steer now with the lower links running up towards the front vs the posts on the first page where the lower links were running downhill towards the front?

At this stage the rebound is very good
Compression not so good, wheel base shortens and would create rear steer on articulation
I think once I get a target anti squat % , I can start working on rear links

I will post updated front roll centre and roll axis tomorrow when I add dimensions

cheers

[Tweak]

Image below shows updated Front Roll Centre with CG. It's showing roll centre is 43% of the height of the CG.


Image showing 41.5% anti squat with updated roll axis


Input would be greatly appreciated.
Cheers

[Tweak]

This one has 42% Anti Squat with equal shortening of wheel base in compression and rebound, so when it articulates at the rear roll centre it has very minimal rear steer.
Top arm is falling down ever so slightly towards the front, almost level.

Thought?

[Tweak]

Ok all the suspension pros out there. Crazy long instant center forward of front axle, but still has 24.4% Anti-squat.

Diff articulates through 4" incredibly well with very similar pinion angle creating almost no bind.
I was having trouble pin pointing the bind, have since worked out where it comes from on a 4-link.

Top link imaginary link almost goes straight through CG, is this good?

Is having the Instant Centre this far forward an issue?

[David Pozzi]

Here is a page from the back of an old “Chevrolet Power” book published by Chevrolet 6th edition, 1988. It's mostly an engine build and parts book but has a few pages of Suspension info at the back. Ignore the first paragraph which refers to a previous page. The drawing shows lower link angles that are pretty severe but they are just an example. The theory used should be sound.

It shows an upper link intersection point "A". and in side view, a line drawn forward from "A" at the angle of the lower links. Where it crosses the axle center plane, is the RC location. If this is really how it works, this system has a very high roll center.

[David Pozzi]

The Ride Tech rear suspension has a designed or recommended ride height. I would double check if your car is set at that height. With the short upper links used to fit under the stock floor, I imagine the geometry would not work well if set very far from recommended height.

[Tweak]

The Ride Tech rear suspension has a designed or recommended ride height. I would double check if your car is set at that height. With the short upper links used to fit under the stock floor, I imagine the geometry would not work well if set very far from recommended height.

100% David, very small window. I have a mechanical engineer who specialising in automotive suspension design helping me now. I'm getting close for my custom setup.

[Tweak]

Working towards zero Rear Steer (tough with short UCA) and zero bind.
Currently have 4mm (0.157") Rear Steer at the axle flange when fully articulated diff.
Small amount of Rear Steer on bump.
Fully articulates with NO Bind now.

Would like to see half this amount.

[dhutton]

How does wheel hop play into all of this? I understood that the lower links had to be parallel to the ground to avoid wheel hop.

Not an expert, just curious.

Don

[Tweak]

How does wheel hop play into all of this? I understood that the lower links had to be parallel to the ground to avoid wheel hop.

Not an expert, just curious.

Don

Hey Don

Yes we looking at the LCA front pick up point now, I'm certainly no expert either. But love a challenge.

So many variables, and at some point there will need to be compromise.
For me the rear steer is the major issue with my ridetech that I need to eliminate.
NZ roads test a suspension system to the max!!! Off chamber fast corners are quite common, with lots of bump. But very fun to drive when the car is nice.

cheers

[Tweak]

How does wheel hop play into all of this? I understood that the lower links had to be parallel to the ground to avoid wheel hop.

Not an expert, just curious.

Don

Hey Don, do you have a build thread for your Cameo.

Im about to start my 56 with C3 suspension. Was already fitted when I bought it, but needs to be re-done for vehicle certification here in NZ.

Cheers

[Tweak]

This road is 10 minutes from my home and a good example of NZ back roads.



Road down south, but they are everywhere

[dhutton]

Hey Don, do you have a build thread for your Cameo.

Im about to start my 56 with C3 suspension. Was already fitted when I bought it, but needs to be re-done for vehicle certification here in NZ.

Cheers

Sorry no build thread. I am using front and rear Dobbertin cradle adapters along with a longer torque tube. I have to run C6 offset wheels due to using the stock C5 track width.

Dobbertin website:

https://rick486.wixsite.com/dobbertinperformance

Don