UUC SwayBarbarians now available for our cars!!

[Orb]

Originally Posted by MisterKris

In regards to the bmw strut lowering camber gain comments from before. All i really know is VAG mcphearson suspensions, and those suffer from large amounts of +camber gain when lowering. But i see these 1er specific susoensions from everyone pretty much slamming the car. Any idea of why this is? Is the suspension geometry not compromised by lowering the cars to these extents?

Lowering this car will cause a very significant migration of the front roll center. It is not too uncommon for this to happen with McPherson struts. There is some increase in negative camber with the two independent lower control arms. Adding a front roll bar would help but at the cost of changing other attributes that are far worse and the car will under steer more in all cases! Not many people are thinking about the effects of roll bars through (load transfer is the key to understanding why). The recommendation are based on previous experience and not solving the problem first hand. If you lower the car you need stiffer front spring and most suspension kits do this. If your rebasing your roll bars to H&R front and rear you will need stiffer front springs with KW at least due changes in dynamic load dynamic (not steady state). In the end the car can be set dead neutral with roll bars and springs that work in harmony with sub -2.0 degrees front camber. It is something I achieved with a 150 hundreds of hours work and several custom parts. FWIW, droop travel became all so imporant on the front.

The far greater evil is people who change there wheel offsets with new wheels or spacers which physically changes king pin inclination offset and scrub radius. Honestly, when one hears king pin inclination change they should avoided it at all cost or you will be rewarded with far less traction and some undesirable handling traits at the limit.

[mikeo]

Orb, would you please expand on the droop issue? Thanks.

[Orb]

Originally Posted by mikeo

Orb, would you please expand on the droop issue? Thanks.

I did some tuning in how droop travel is handled with different main springs preloads & lengths & rates, tender spring lengths & rates, and camber plate stack heights. It made a big difference on how the car sets in the corner. It was a key turning point in getting the car to behave the way I wanted. The first part of the problem was in understanding why the car had under steer which was related to 3 separate problems along with this one. I will write something in the next two weeks about this long drawn out journey of what I did and why in a lot more detail. I have a track day next week so I will validate my latest changes then.

As a side note, the stock top mounts are a horror show for use with anything than the stock spring. They deflect 15 with static ride height and up to 20+ mm in compression. In reverse loading, the top mounts stretch 25+ mm from the maximum compression load. I will leave it to your imagination why this is not so good. Unfortunately, there are no camber plates they you can buy off the self that don’t add massive amounts of spring preload for a minimal/ideal lowering. The KW camber plates are still off by 14 mm for nominal stack height targets that I calculated which is twice as good as anything else available. The camber plates I’m running are hybrid of KW design with the modified stack height and they add 0.75 degrees more caster.

Orb

[mikeo]

Very interesting indeed. Please do keep us updated on your findings.

[Orb]

Originally Posted by mikeo

Very interesting indeed. Please do keep us updated on your findings.

I will let you think about it some more but what I have done is manipulated the inside wheel front spring rate so it falls off rapidly under droop and main spring preload far more than a stock BMW or KW 2011 front spring during a corner. This will effect how the car sets in but also how the suspension deals with bumps on the inside wheel during cornering. If you have a stiff spring on the inside wheel in droop under bump it will induce more roll and the car seems to be very sensitive to this. Sensitivity to this issue diminishes as spring rates increase and travel decreases if spring preload vs ride height is setup properly.

Most of the suspension tuning problem can be broken down into simply ideas. All one need to do is understand how the load is transfer in steady state condition but more importantly in dynamic condition. For example, you put a bigger roll bar on the rear and how does this effect load transfer. The load in steady state condition transfer to the outside wheel but in dynamic condition under braking the load moves forward to the outside front wheel as well. They next steep is to use a flow chart to fix the problem. In a lot cases you got a 50/50 chance of getting it right but the solution can go into an endless loop because it effect something else which happens more often than not. They key things to look at, are the solutions effective and balanced. Get it wrong then you go backwards. You will guess wrong more often than right but that how problems are solved. BTW, I have guessed wrong about 15 time now.

Orb

[scottn2retro]

We tried the UUC front sway bar only (did not try rear bar) in the race car and it made a huge difference in the handling of the car. Because of how low our car is, we had to shorten the end links, but once we got that done, it helped a lot.

[MINI135i]

Originally Posted by scottn2retro

We tried the UUC front sway bar only (did not try rear bar) in the race car and it made a huge difference in the handling of the car. Because of how low our car is, we had to shorten the end links, but once we got that done, it helped a lot.

I am sure you have quoted this somewhere else but just for reference: how low is your car compared to stock??

[scottn2retro]

Originally Posted by MINI135i

I am sure you have quoted this somewhere else but just for reference: how low is your car compared to stock??

Somewhere in the 1-2 inches range.

[MINI135i]

That's kind of vague..:wink::biggrin: