Is 12lb total difference in weight going to affect a lot?

[Spuds]

Originally Posted by ermax

Well obviously the sprung weight needs to be controlled. But that is slow movement. The wheels also need controlling and would be high speed. I can assure you our wheels DO NOT stay on the ground 100% of the time. I'm not talking about rally style jumps. I'm talking about very high rates of movement up and down where the tires unload reducing grip. All I'm saying is the potential for this to happen would be higher with more unsprung mass and IMO would require more damping.

Yes, more wheel mass is more likely to leave the ground by hitting a bump, all other conditions being the same. It also will take longer to get back to the ground than a lighter wheel. That's exactly what my addendum to zdan's post was describing. We seem to agree on that.

However, more damping would reduce the energy transferred to the spring, this is bad for wheel contact under bump conditions. A spring stores and returns energy, while a damper transfers it into waste. An overdamped car will transfer too much force into moving the frame of the car up and down. The car is only acted on by gravity (let's ignore aero for now). So if the wheel is stiffly linked to the car by a high rate damper, it can only fall at the rate of gravity since that's the rate the car is falling at. The less damping there is, the less that corner of the car will move vertically. This means that the spring absorbs more of the energy, and has a more stationary counterweight to push the wheel downwards with.

Also I feel like this applies lol.

[ermax]

Originally Posted by Spuds

Yes, more wheel mass is more likely to leave the ground by hitting a bump, all other conditions being the same. It also will take longer to get back to the ground than a lighter wheel. That's exactly what my addendum to zdan's post was describing. We seem to agree on that.

However, more damping would reduce the energy transferred to the spring, this is bad for wheel contact under bump conditions. A spring stores and returns energy, while a damper transfers it into waste. An overdamped car will transfer too much force into moving the frame of the car up and down. The car is only acted on by gravity (let's ignore aero for now). So if the wheel is stiffly linked to the car by a high rate damper, it can only fall at the rate of gravity since that's the rate the car is falling at. The less damping there is, the less that corner of the car will move vertically. This means that the spring absorbs more of the energy, and has a more stationary counterweight to push the wheel downwards with.

Also I feel like this applies lol.

I agree with all that. I guess the only thing that's debatable is if lighter wheels would require less damping. IMO they would require less but it's probably such a small impact that it wouldn't really be necessary to change anything.

For sure this thread is jacked, but the new topic is much more interesting. Hahaha

[Racecomp Engineering]

Sprung weight (the chassis) is controlled by rebound damping. Unsprung weight (wheels, suspension parts, etc) is controlled by compression damping. They are not the same (you can have a lot of compression damping and very little rebound damping for example, or vice versa).

The car was designed with certain goals in mind..."balance" is one of them. As was cost and durability. Lightweight wheels are generally expensive. If they're not expensive, they're usually not very strong. The OEM wheels were chosen as a compromise between function, durability, and cost. The same can be said of the OEM dampers. Over time, the OEM dampers have gone through some tweaks and changes...the OEM wheels in the USA did not (until 2017).

Track cars CAN have a relatively comfortable ride. Properly dialed in, they can feel better than stock especially over big bumps. They might not feel as good on certain surfaces though, and often require more frequent servicing. Many track cars do not have a great ride, but often the good ones will ride better than typical street tuner cars.

- Andrew

[Spuds]

Originally Posted by Racecomp Engineering

Sprung weight (the chassis) is controlled by rebound damping. Unsprung weight (wheels, suspension parts, etc) is controlled by compression damping. They are not the same (you can have a lot of compression damping and very little rebound damping for example, or vice versa).

- Andrew

Got a question on this part. Why does the unsprung weight need to be controlled? More specifically, what conditions would cause unsprung weight to be out of control and what could happen as a result?

[nikitopo]

Originally Posted by rvoll

For a street car, I've always regretted putting on lighter wheels/tires. And I've almost never found a better ride with alternative/higher priced suspension parts because they are designed for performance and not comfort. It is theoretically possible, but have you looked for springs with lower spring weights than OEM? Or dampers with less damping?

When I changed wheels I went to Enkei's RS05 which are not that different on weight from the stock ones.



As you can see they focus more on the strength and stiffness side and they are more suited for the street too.

Same can be said about the Sachs performance coilovers that have progressive springs with an average of 35.8N/mm rate front and rear. Stock springs on the latest models are in the range of 30.0N/mm front and rear, so not that much difference too.

I have not regretted with any of these modifications and overall the car drives now better without any noticeable imbalance.

[RayRay88]

Originally Posted by nikitopo

When I changed wheels I went to Enkei's RS05 which are not that different on weight from the stock ones.



As you can see they focus more on the strength and stiffness side and they are more suited for the street too.

Same can be said about the Sachs performance coilovers that have progressive springs with an average of 35.8N/mm rate front and rear. Stock springs on the latest models are in the range of 30.0N/mm front and rear, so not that much difference too.

I have not regretted with any of these modifications and overall the car drives now better without any noticeable imbalance.

What size did you buy those wheels in?

[nikitopo]

Originally Posted by RayRay88

What size did you buy those wheels in?

The stock wheels were 16" and I stayed in similar specs. When I changed the suspension to Zachs coilovers, I had to check that the wheels were approved by the suspension manufacturer:



The camber, toe, and caster angles of the suspension were checked after the installation by DEKRA.

This is how things SHOULD be and not the common local garage or shop installation.

[RayRay88]

Originally Posted by nikitopo

The stock wheels were 16" and I stayed in similar specs. When I changed the suspension to Zachs coilovers, I had to check that the wheels were approved by the suspension manufacturer:



The camber, toe, and caster angles of the suspension were checked after the installation by DEKRA.

This is how things SHOULD be and not the common local garage or shop installation.

A simple 16x6.5 would have sufficed, but whatever.

The state mandating such things seems super over zealous for anyone with half a brain. I guess it keeps the stupid masses from hurting themselves.

[nikitopo]

Originally Posted by RayRay88

I guess it keeps the stupid masses from hurting themselves.

And the rest of the drivers/family cars/etc ...

[why?]

it's totally moronic. But the EU wants everyone to look to them for absolutely everything, that way they can infantilize the populace completely.

I mean it is really hard to screw up wheels.