PSA: Think twice before lowering your car

[T.J.]

How would my comment be fixed to be accurate?

Body roll does not equal weight transfer, it is just a visual clue. Consider the extreme case of a go cart with no suspension going around a corner - zero roll but weight is being transferred.

[Bry5on]

If I'm understanding what you're saying...then I lowering the control arm mounting points would help with a loss of negative camber and maintain more optimal suspension geometry?

I run -4.1 camber in the front right now which gets even wear. I mostly use tire wear to set camber because tires ain't free! I also don't have the time jump out of the car and take tire temps...I'm usually jumping right into another car.

Yep! For example, if you take a look at a modern base/S Porsche 911 or cayman, they can’t run wheels smaller than 19” - not because of brake clearance but because the control arm and tie rod ball joints are placed so low! Those cars also have macpherson front suspensions

[bigjae46]

Yep! For example, if you take a look at a modern base/S Porsche 911 or cayman, they can’t run wheels smaller than 19” - not because of brake clearance but because the control arm and tie rod ball joints are placed so low! Those cars also have macpherson front suspensions

So if I lower the control arm mounting points then I can run less negative camber? I run 17" wheels...I'll have to go look at see how much room I have.

If I understand I would need to lower the 3 mounting points for the control arm plus the tie rod. I believe Bimmerworld, VAC, AKG and SLR are options. I think the BW option is the best one.

What about the rear axle?

[Wernd]

Body roll does not equal weight transfer, it is just a visual clue. Consider the extreme case of a go cart with no suspension going around a corner - zero roll but weight is being transferred.

It may not EQUAL weight transfer but it does AFFECT it. I'll give you the opposite extreme case, a vehicle that transfered so much weight that it's up on two wheels. Heck it could even be a go kart up in two wheels, in that case the entire body would have rolled without any suspension travel

[Bry5on]

So if I lower the control arm mounting points then I can run less negative camber? I run 17" wheels...I'll have to go look at see how much room I have.

If I understand I would need to lower the 3 mounting points for the control arm plus the tie rod. I believe Bimmerworld, VAC, AKG and SLR are options. I think the BW option is the best one.

What about the rear axle?

just the two control arm mounting points at the suspension knuckle. I also run 17s, there’s not a whole lot of available room.

I don’t have a lot of experience with the e46 rear suspension personally but it’s a pretty simple design. The biggest thing that you would have trouble dialing out appears to be anti-squat due to the angle of the rear trailing arm. Similar effect to the control arm that’s horizontal, except that you’ll eat up your suspension travel while under hard throttle.

Without knowing the curves of the rear suspension it’s hard to answer with confidence whether there would be roll center issues. The front suspension is so simple that it’s easy to understand without a whole lot of measurements. I’d expect based on the rear suspension design that it’s far less susceptible to roll center problems vs the front, but you’ll still have to contend with anti-squat.

[bigjae46]

just the two control arm mounting points at the suspension knuckle. I also run 17s, there’s not a whole lot of available room.

Isn't there only one mounting point at the knuckle? Or are you referencing the mounting points on the knuckle and front subframe? Would I lower the mounting point about the same about that I lower the car by?

[Bry5on]

Isn't there only one mounting point at the knuckle? Or are you referencing the mounting points on the knuckle and front subframe? Would I lower the mounting point about the same about that I lower the car by?

Sorry that should have read two ball joint mounting points. One control arm and one tie rod. They both need to be lowered together and yes, lowering the same amount as the car is being lowered is the simplest path. You can likely get away with less since you’ll be limiting travel with stiffer springs, but you’d need to do the math to get the best numbers.

[tlow98]

I always wondered why Porsche knuckles stuck down so close to the wheel like that. Now I know! Thanks.

[eacmen]

Sorry that should have read two ball joint mounting points. One control arm and one tie rod. They both need to be lowered together and yes, lowering the same amount as the car is being lowered is the simplest path. You can likely get away with less since you’ll be limiting travel with stiffer springs, but you’d need to do the math to get the best numbers.

I understand lowering the control arm mounting point. But the tie rod shouldn’t affect suspension travel, right? As long as its long enough to dial in the right toe?

[Bry5on]

I understand lowering the control arm mounting point. But the tie rod shouldn’t affect suspension travel, right? As long as its long enough to dial in the right toe?

If you don’t lower them together, you’ll end up with bump steer, where the wheels will turn when the suspension compresses mid-corner without any steering input. Personally I would treat eliminating bump steer as a higher priority than managing the roll center!

[eacmen]

If you don’t lower them together, you’ll end up with bump steer, where the wheels will turn when the suspension compresses mid-corner without any steering input. Personally I would treat eliminating bump steer as a higher priority than managing the roll center!

This makes sense. Thanks!

[BigDave]

I ended up with a compromise. For years since 2009 when I bought my 2005 cabro, I had it lowered on coil overs...KW, then BC Racing and now TC Kline. I live in South Florida and travel ALL the time on I-95 which is RIFE with large debris of all kinds. Over the years I sustained several thousands of dollars in damage to my Strassentech CF lips. You can repair them twice then you have to buy a new one.

Not to mention problems with sloped entry ways, speed bumps, etc. No MORE! The solution was simple.
When I installed the TC Kline kit, I adjusted the front and rear springs all the way to the top. Fortunately, that came out perfectly even for the front/rear ride height. The car's stance still looks great. I run full caster, and stock camber and toe. 245-19's in front 275-19's in the back...Michelin Pilot Sport 4s. (rolled rear fenders)

I still have a lowered car, but not the standard drop of 13.5"/13". Now, NO more damage at all up front...or anywhere. I clear EVERY parking divider, I clear every entry way slope and can take them straight on. The lift is not much. it is in-between stock height and slammed, but it makes all the difference for successful damage-free daily driving in Southeast Florida. I suppose I should measure it so I can post the figures. It just works so well for my needs.

[T.J.]

It may not EQUAL weight transfer but it does AFFECT it. I'll give you the opposite extreme case, a vehicle that transfered so much weight that it's up on two wheels. Heck it could even be a go kart up in two wheels, in that case the entire body would have rolled without any suspension travel

Roll effects weight transfer only with the movement of the CG which is an incredibly small effect compared to everything discussed in this thread. Your example of a vehicle with no suspension tipping over is more of an argument to widen the track and lower the CG.

[dukeofchen]

I ended up with a compromise. For years since 2009 when I bought my 2005 cabro, I had it lowered on coil overs...KW, then BC Racing and now TC Kline. I live in South Florida and travel ALL the time on I-95 which is RIFE with large debris of all kinds. Over the years I sustained several thousands of dollars in damage to my Strassentech CF lips. You can repair them twice then you have to buy a new one.

Not to mention problems with sloped entry ways, speed bumps, etc. No MORE! The solution was simple.
When I installed the TC Kline kit, I adjusted the front and rear springs all the way to the top. Fortunately, that came out perfectly even for the front/rear ride height. The car's stance still looks great. I run full caster, and stock camber and toe. 245-19's in front 275-19's in the back...Michelin Pilot Sport 4s. (rolled rear fenders)

I still have a lowered car, but not the standard drop of 13.5"/13". Now, NO more damage at all up front...or anywhere. I clear EVERY parking divider, I clear every entry way slope and can take them straight on. The lift is not much. it is in-between stock height and slammed, but it makes all the difference for successful damage-free daily driving in Southeast Florida. I suppose I should measure it so I can post the figures. It just works so well for my needs.

Pics of this setup? The idea of being able to crush city streets with less stress is attractive.

[Wernd]

Roll effects weight transfer only with the movement of the CG which is an incredibly small effect compared to everything discussed in this thread. Your example of a vehicle with no suspension tipping over is more of an argument to widen the track and lower the CG.

First, it was your example. Second, I was simply stating a fact that body roll does in fact affect weight transfer. Your comments were eluding to the opposite