Suspension tweaks

[Johnologue]

That image is also from shortly after the reveal in early 2025, very prototype. I wouldn't assume that the suspension will end up being exactly the same by production.

 

[ElectricShitbox]

That too. I can't wait until I can crawl under a production model. Lots I want to see up close.

 

[cadblu]

I would love to see an engineering analysis of Slate’s suspension conducted by Sandy Munro’s team. Here is an in depth hoist review of the suspension on the Chevy Blazer EV.

Munro Associates suspension design

 

[Driven5]

If the Slate ends up popular with people that care that much about how it handles (I still think an SCCA autox Spec Slate class would be a fun idea, even though that's not really what I'm looking for), then some real suspension pervert will design a watts link for it (maybe me, lol).

Spec Slate would be awesome, even if it doesn't make any logical sense.

The problem with Watts link is that it's a lot of complication and expense for no real benefit. From a performance perspective, a credit card (or even USB charging cable) worth of lateral movement that doesn't actually affect the alignment or contact patch is lost in the noise of other compliance and deflection from the tires and suspension. A few things people also tend to either not know or neglect when discussing the virtues of the symmetry of Watts for 'turning both directions' are that:

1) L/R handling is already imbalanced on cars with equal L/R spring rates but unequal L/R weight distribution. This is why so many people have experienced faster lap times with a passenger on board than solo, despite the extra weight.

2) Every autox/road course still has 360 degrees more turns one direction than the other. So equal L/R cornering is not necessarily fastest overall.

3) Not applicable to the Slate DeDion, but on live axles some Panhard angle can also be used to help counter the unbalanced torque effects.

Not that it's often done, or even thought about, but an adjustable AND reversible Panhard would actually be more 'ideally' tunable (and easily so) to any given track than a Watts.

Assuming a lowered Slate effectively levels out the Panhard, my biggest gripe with the it is just that it would be better to run the bar the opposite (axle left, chassis right) way... Such that the roll center rises when the body rolls towards the driver side and the roll center lowers when the body rolls towards the passenger side. This would counter rather than contribute to the imbalanced L/R roll effects. As well thought out as the rest of the Slate DeDion setup seems to be, I'm guessing there were other packaging constraints that took precedence instead.

 

[Johnologue]

When you put it like that, it sounds like the more complex linkage's main performance effect would be (potentially) adding weight.

 

[IamSpotted]

As well thought out as the rest of the Slate DeDion setup seems to be, I'm guessing there was packaging that took precedence instead.

That's what I'm figuring. I figure the factory drop will improve that angle some and I'd honestly be OK with an aftermarket kit that levels the panhard bar and corrects for the slightly shorter distance

When you put it like that, it sounds like the more complex linkage's main performance effect would be (potentially) adding weight.

There is added weight for sure, but depending on goals, it would be worth it. The watts linkage would have better handling consistency, especially if performance is the goal. For daily driving, it likely wouldn't be a noticeable difference over a well setup panhard bar.

 

[Driven5]

When you put it like that, it sounds like the more complex linkage's main performance effect would be (potentially) adding weight.

...And unsprung weight at that. But in all fairness, my previous comments were also from more of a theoretical standpoint.

As with almost everything, the answer to which is better in practice is 'it depends'. Each has its potential advantages in different circumstances. and execution matters more than anything. There are many people who have found improvements going from Panhard to Watts, but it generally seems to be non-optimized Panhard to optimized Watts. I've not seen any of those that have demonstrated true apples-apples comparisons between equally well engineered solutions.

Personally if I was going through the cost and effort to add the complexity of a Watts, I'd probably take it all the way to a Mumford instead.

 

[IanNubbit]

Here you go. My memory is wrong though the truck was on the ground. As seen in this article.
https://www.theautopian.com/why-the-slate-evs-unconventional-rear-suspension-makes-perfect-sense/

It’s not great for sure, but also this has the KO2s on, so this is the 2” lift, I suspect stock height will be basically flat, this is still less of angle on the 2” lift on JL/JTs and they perform just fine.

 

[coregrind]

Before hours, I slid under the truck on display at the event happening now in Portland, Oregon so I could take a look at the panhard bar situation. Later, during event hours when staff was on hand, I had a chat with Million, a Slate Technician. I asked how the change in panhard bar geometry would be addressed with the installation of the accessory kits for a lifted or lowered suspension. He wouldn’t confirm the means by how it will be addressed, but stated each kit will include the necessary items for optimal performance. He assured that everyone working on it is passionate about the project. My concerns are lessened now.

 

[d.h.]

coregrind, what did it look like, level? I wouldn't expect the techs at the events to have every detail at their fingertips. No info is better than wrong info. Even a dead level panhard bar will have some lateral movement. During normal driving you're never going to see 4"of compression. My f150 is lowered 5" in the back, it doesn't have much more than 4"if that , but in the 4 years it's been lowered , it's only bottomed out a couple of times. I don't see the panhard bar as a problem.

 

[coregrind]

coregrind, what did it look like, level? I wouldn't expect the techs at the events to have every detail at their fingertips.

I didn’t see anything indicating it had lift spacers in place, so what was shown could be considered ‘stock’ height, if this represents the finished product. The bar on this unit was angled slightly upward.

I see that as a positive, as I want to lower mine on day one. At most, I would then consider a shorter bar. Definitely not necessary, but why stay stock. Ha!

The tech didn’t resort to a quick response and simply say it’ll be optimized. He wouldn’t confirm any of my suggested panhard ‘solutions’ as happening or not happening. And was very cautious about what he told me, as I got the vibe he was instructed to not divulge too much info. I appreciate that since I feel like two months ago there were agents providing contradictory info and specs on other topics. As you pointed out, no info is better than wrong info. He freely provided that camber correction bolts for the front will be included in the kits. No surprise there.

 

[kvermeer]

I am unconcerned about a little angle in the panhard when empty.

It's a truck, rated for hauling 1550 lbs, it shouldn't be optimized for neutral suspension when *empty*.

https://www.slate.auto/en/how-much-can-a-slate-tow

We keep comparing it to old compacts like the 1970s Chevrolet LUV, but in terms of GVWR/capacity it's more like the C20 with a curb weight of 4000 lbs and a nominal 3/4 ton payload! If you put half a skid of bagged concrete in the back, then the panhard bar will go past horizontal.

If you're not carrying a lot of concrete, then it's above center, but I suspect they use the same bar position and suspension when loaded down with 400 lbs of SUV kit and 400 lbs of passengers in the back seats, not to mention the driver and potential passenger in the front seats. I do wonder if the 2" lift kit includes an offset bracket to adjust this position, it might be just right for a lowered Slate but that would start to get too much if it's lifted higher.

Based on a Mk. 1 eyecrometer measurement and the published overall/between the wheel wells bed width, that's about a 40" long bar with 2" of rise. If you go over a rise and the bar gains an extra inch of rise, sqrt(40*40+2*2) vs sqrt(40*40+3*3) gives 40.049 vs 40.112, that's all of 1/16th of an inch of lateral movement in the axle and resulting angle added to the trailing arm bushings. It's fine. Yes, it would be reduced (0.012" vs 0.063") if the bar was horizontal to start, and yes, it goes 1/16th inch in the other direction for a total of 1/8th range of motion if you compress it by an inch instead of half travel to the right at neutral and travel to the left at either compression or extension.

If you want to optimize your Slate to compete with Porsches at autocross events, maybe that's an improvement you can make to the suspension geometry. But I'm more likely to be pouring a new slab in front of my shed.

 

[CEW]

Before hours, I slid under the truck on display at the event happening now in Portland, Oregon so I could take a look at the panhard bar situation. Later, during event hours when staff was on hand, I had a chat with Million, a Slate Technician. I asked how the change in panhard bar geometry would be addressed with the installation of the accessory kits for a lifted or lowered suspension. He wouldn’t confirm the means by how it will be addressed, but stated each kit will include the necessary items for optimal performance. He assured that everyone working on it is passionate about the project. My concerns are lessened now.

This is really cool that you got to do that!
BEFORE HOURS ? Is this Before the Mall opens? And the Display truck stays in there overnight?
The Slate tech (Million) stays with the truck?

Really good info 👍

 

[coregrind]

This is really cool that you got to do that!
BEFORE HOURS ? Is this Before the Mall opens? And the Display truck stays in there overnight?
The Slate tech (Million) stays with the truck?

Really good info 👍

Yes. Yes. No. Ok, I’ve said too much.

 

[d.h.]

kvemeer , thanks for the math lesson, and the calibrated eyeball. Looks to me like the sidewalls will eat up 1/16" lateral movement. Problem solved.