[TrackM4x]

Best explanation I've seen of roll center. If you are lowering your car without adjusting for roll center then you are making body roll worse.

[BulkBen]

Originally Posted by TrackM4x

Best explanation I've seen of roll center. If you are lowering your car without adjusting for roll center then you are making body roll worse.

The video was good, but not particularly relevant to the average M owner.
As discussed in the video, these drifters typically lower their cars 75 - 100mm which wreaks absolute havoc with suspension angles, roll centres ending up at terrible points.

In cars where we’re going 10 - 30mm max, control arm angles usually don’t move much, so things really aren’t being thrown out.

Cases where a minor drop (and stiffer springs) really don’t affect roll centre in a negative way, people can still expect a minor benefit to handling, albeit from less weight transfer.

[forcefed]

Originally Posted by TrackM4x

If you are lowering your car without adjusting for roll center then you are making body roll worse.

I don't think anyone takes that into consideration, let alone cares

[moproblems]

I only really consider roll center to be problematic when aftermarket coilovers with adjustable body length comes into the equation. Moving the full range of damper stroke to a position lower than what was designed is what really can fuck up geometry. A lowering spring or HAS only changing the static position within the OEM stroke keeps geometry within OEM parameters, although not as ideal. There is only so low full bump can go with a stock length damper.

However proper geometry is important, but I don't know how many people would be able to notice.

[yousefnjr]

Every day I get a little less motivated to install this KW kit sitting in my garage

[TrackM4x]

Originally Posted by BulkBen

The video was good, but not particularly relevant to the average M owner.
As discussed in the video, these drifters typically lower their cars 75 - 100mm which wreaks absolute havoc with suspension angles, roll centres ending up at terrible points.

In cars where we’re going 10 - 30mm max, control arm angles usually don’t move much, so things really aren’t being thrown out.

Cases where a minor drop (and stiffer springs) really don’t affect roll centre in a negative way, people can still expect a minor benefit to handling, albeit from less weight transfer.

I get that. But the problem is that some of these lowering kits are actually using softer spring rates.

[beachBmmr]

People will still argue that their ast springs improved their handling...

The correct answer is to get a coilover, but dont change ride height...

Or start re-engineering the entire suspension geometry BECAUSE ASTHETICS!!

[Ximian]

Unpopular opinion: the stock suspension is better than most of the coilover options available today.

[Limegrntaln]

My car has much less body roll with springs installed. And we don't use drop spindles.

[Dr.Deep]

Originally Posted by Ximian

Unpopular opinion: the stock suspension is better than most of the coilover options available today.

Have you driven the car with some coilover suspension and a proper setup?

You don't get a KW V3 or V4 suspension and just slap it on the car…you do some proper rebound and compression (high and low speed) setups to your liking and use.

It's day and night how the car handels afterwards. Believe me, I've driven both back to back after I had my V4 installed…if you wouldn't know, you wouldn't say you sit in the same car.
There are reasons you pay 6 or 7k for a suspension, not just because it sits lower

[Ximian]

Originally Posted by Dr.Deep

Have you driven the car with some coilover suspension and a proper setup?

You don't get a KW V3 or V4 suspension and just slap it on the car…you do some proper rebound and compression (high and low speed) setups to your liking and use.

It's day and night how the car handels afterwards. Believe me, I've driven both back to back after I had my V4 installed…if you wouldn't know, you wouldn't say you sit in the same car.
There are reasons you pay 6 or 7k for a suspension, not just because it sits lower

Is this for a track car? I have not driven the G80/G82 with coilovers.

What does your alignment look like now?

[Dr.Deep]

Originally Posted by Ximian

Is this for a track car? I have not driven the G80/G82 with coilovers.

What does your alignment look like now?

No, it's not a only track car…it's my daily with track use 2-3 times per year so the setup is not that radical as for a mainly track car.

Camber is slightly more than stock, don't have the papers in front of me from the last one. Always going to the same company for the re-adjustments so they have all the different setup I had so far in their database if I want to go back to a previous setup. Have done an adjustment 4 or 5 times until I was happy with it.
And the V4s have like two memory setups that you can switch from road to track setup in terms of rebound and compression when you arrive at tje track.

[beachBmmr]

Originally Posted by Ximian

Unpopular opinion: the stock suspension is better than most of the coilover options available today.

I agree. There are not great Motorsport oriented, rebuildable options out there. Tractiv is testing their DDC coil now, and they told me it's coming soon. I understand its programmable dampening so you can use the EDC selector for ride control and get a true dial-a-dampening with a wide range of rebound, and compression settings. This would be the only setup Id use on a street+track car.

The car as stock is very compliant over kerbs, but it does roll and dive *a Lot* and is tail happy under braking. Its setup to understeer (as typical street cars) with 53% weight on the front axle, which is also not a great track setup. I have gotten a bit better rotation with increased grip on the front axle with Camber plates, but pushing weight more rearward, and taking some rake out would be the next step to get a better balance.

Looking at the entirety of the Suspension, there is a lot of numbness and deflection to deal with as well. Fall Line addresses all the bushings- making full spherical bearings, and some nice adjustable control arms for the rear.

SPL took most of their F80 parts and adapted them to the front with toe links, sway bar end links, and tie rod ends...All told theres about 3500 in linkage parts available to remove all that comfort...not for a regularly street driven car.

The car also needs more rubber for its weight, again, not great options unless you look at Studio RSRs build with 19x11 and 305s in front, however its an extreme fit even with the fender flares.

https://csfrace.com/vehicle/csf-proj...attack-g82-m4/

Coils, Aero, and much wider tires took 4 seconds off their laptime at Button Willow...Thats a lot of changes for 4 seconds. likely the wider tires first, suspension second, and aero who knows...

[McLaren720s]

I'm thinking BMW's newly released M Performance HAS is probably the best solution for someone looking to drop center of gravity, speed up weight transfer and improve looks without spending 6-7k on a coilover set.

If price is not an issue or one is an advanced driver, a full coilover set is definitely the superior solution.

[DRLane]

Originally Posted by beachBmmr

I agree. There are not great Motorsport oriented, rebuildable options out there. Tractiv is testing their DDC coil now, and they told me it's coming soon. I understand its programmable dampening so you can use the EDC selector for ride control and get a true dial-a-dampening with a wide range of rebound, and compression settings. This would be the only setup Id use on a street+track car.

The car as stock is very compliant over kerbs, but it does roll and dive *a Lot* and is tail happy under braking. Its setup to understeer (as typical street cars) with 53% weight on the front axle, which is also not a great track setup. I have gotten a bit better rotation with increased grip on the front axle with Camber plates, but pushing weight more rearward, and taking some rake out would be the next step to get a better balance.

Looking at the entirety of the Suspension, there is a lot of numbness and deflection to deal with as well. Fall Line addresses all the bushings- making full spherical bearings, and some nice adjustable control arms for the rear.

SPL took most of their F80 parts and adapted them to the front with toe links, sway bar end links, and tie rod ends...All told theres about 3500 in linkage parts available to remove all that comfort...not for a regularly street driven car.

The car also needs more rubber for its weight, again, not great options unless you look at Studio RSRs build with 19x11 and 305s in front, however its an extreme fit even with the fender flares.

https://csfrace.com/vehicle/csf-proj...attack-g82-m4/

Coils, Aero, and much wider tires took 4 seconds off their laptime at Button Willow...Thats a lot of changes for 4 seconds. likely the wider tires first, suspension second, and aero who knows...

Went from 1:56 stock to 1:49.7. That's a considerable drop.

[BMWRacer523]

Originally Posted by DRLane

Went from 1:56 stock to 1:49.7. That's a considerable drop.

That's huge tbh.

[beachBmmr]

Originally Posted by BMWRacer523

That huge tbh.

I bet 90% of that was tires. They put 305 up front for that last session time. Suspension helped but suspension is not adding so much grip to enable time reduction of 6 seconds

[BMWRacer523]

Originally Posted by beachBmmr

I bet 90% of that was tires. They put 305 up front for that last session time. Suspension helped but suspension is not adding so much grip to enable time reduction of 6 seconds

Sure, but regardless that's a worthwhile increase.

[DRLane]

Originally Posted by beachBmmr

I bet 90% of that was tires. They put 305 up front for that last session time. Suspension helped but suspension is not adding so much grip to enable time reduction of 6 seconds

I dropped four seconds on a like track (length, avg speeds, etc) with similar aero to their package on the same tires before/after.

I wouldn't put that all on tires but yes going from PS4S to Supercar 3R is a step up in grip. More grip generally overwhelms all the OEM components (suspension, brakes, cooling) making it mandatory.

[TrackM4x]

Originally Posted by DRLane

I dropped four seconds on a like track (length, avg speeds, etc) with similar aero to their package on the same tires before/after.

I wouldn't put that all on tires but yes going from PS4S to Supercar 3R is a step up in grip. More grip generally overwhelms all the OEM components (suspension, brakes, cooling) making it mandatory.

Which aero are you on?

[DRLane]

Originally Posted by TrackM4x

Which aero are you on?

Zebulon

[CanAutM3]

Originally Posted by TrackM4x

Best explanation I've seen of roll center. If you are lowering your car without adjusting for roll center then you are making body roll worse.

That is not necessarily true.

The handling performance benefit of lowering a car resides in reducing weight transfer. Reducing weight transfer improves total grip when cornering and braking. Roll and weight transfer are not directly related.

Further, the increased rolled induced from moving the roll center on moderate drops can easily be offset by stiffer springs.