Need help - fine-tuning camber to improve lap-times

[Asbjorn]

This goes back to the low hanging fruit thing. Instead of spending the time and money swapping springs out all the time, I would get adjustable front and rear anti roll bars. Then you can change roll stiffness at the track between sessions. Honestly before that I would first get a square tire/wheel setup. This allows for consistency front and rear and so you can rotate your tires to get more longevity out of them.

In the case of oversteer, if you had adjustable bars, you could have either increased stiffness of the front bar or decreased stiffness of the rear bar. Since you make a lot of power I would start with increasing stiffness of the front bar. This will help put more weight on the inside rear tire and help keep rear squat in check when powering out of a turn.

Done

Since there are no adjustable anti roll bars available on the market in China, I decided to just modify the H&R bar. I found a factory that actually makes these bars for the US ATV market. They had all the tools and skills to get the job done in three hours. This means I now have three settings to choose from both front and rear.

I am currently running the inner setting and it definitely makes a difference.

 

[barry@3DM]

@Asbjorn Love it!! Good move. I did the exact same thing as I wanted to keep a relatively soft bar in the rear of the e90 for starters. I'm in the process of building a custom anti roll bar rating machine to actually put some numbers to them instead of going by diameter which essentially means nothing. Can't wait to hear how it works out at the track for you!

 

[AzNdevil]

there are quite a few things you should try out
1 - a proper set of 2 way adjustable coilovers (ast/jrz comes to mind), you really need stiffer springs up front and nothing on the shelf works
2 - wider front tires, you can get away with less camber
3 - zero out/toe out in front, reduces mid corner understeer but it does make the car darty/twitchy under trail braking
4 - superpro control arms, you can squeeze and play around with a little more camber/caster up front
5 - your car is still rolling a lot so you need more camber to compensate for the roll, if you just want more camber outright, go get the dinan camber plates and stack them on top of the adjustable camber plate you currently have

tbh i wouldnt compare the zestino with ad08r, the zestinos you need to keep them cool or else they just melt away and give up
the ad08rs dont really bite until you warm them up enough, theres more grip from zestino than ad08r but its easier to find the limit on a ad08r than zestino

 

[Rob09msport]

This could be really dumb idk but what about like a bow flex design like 3 thin bars or a bar inside a large thin bar so you can adjust how many you bolt to alter torsional rigidity not just pre load?

 

[Asbjorn]

there are quite a few things you should try out
1 - a proper set of 2 way adjustable coilovers (ast/jrz comes to mind), you really need stiffer springs up front and nothing on the shelf works
2 - wider front tires, you can get away with less camber
3 - zero out/toe out in front, reduces mid corner understeer but it does make the car darty/twitchy under trail braking
4 - superpro control arms, you can squeeze and play around with a little more camber/caster up front
5 - your car is still rolling a lot so you need more camber to compensate for the roll, if you just want more camber outright, go get the dinan camber plates and stack them on top of the adjustable camber plate you currently have

tbh i wouldnt compare the zestino with ad08r, the zestinos you need to keep them cool or else they just melt away and give up
the ad08rs dont really bite until you warm them up enough, theres more grip from zestino than ad08r but its easier to find the limit on a ad08r than zestino

Thank you very much for these suggestions

1 - why do I need stiffer springs up front? That sounds like it would increase understeer.
1 - I love the idea of adjustable dampers, and I would love to have that for sure. But all the coilovers on the market lower the car. Here's an example: https://e89.zpost.com/forums/showpost.php?p=24742317&postcount=31
I do not want to lower the car, especially not up front. And I dont see why I would want to lower the car even for track use. Some of the tracks I visit are much faster when you are able to cut the curbs. Aerodynamics is not something Im getting into, and lack stability / lots of weight transfer is something I can handle. Im not doing bumper to bumper racing as such, so I can plan the cars direction ahead.
2 - thanks to this thread, I just ordered a set of 4x 18x9 et30 wheels. They should allow me to run 250 slicks or higher in a square setup. I just posted about this in my build thread linked in my signature below.
3 - Noted. I definitely don't want more dartyness under braking from the car, but I think stiffer RTABs will solve that, and then I can move forward with toe.
4 - The other posters recommended I didn't do that?
5 - when the car rolls, the camber on the outer wheel increases, because my car is still pretty much at stock height. So roll is good, no?

I could not agree more with you on AD08R vs Zestinos. That's exactly my observation as well. I did a 1h endurance race with the AD08r a few weeks ago, and they finally started to melt. The Zestinos start to melt when you turn on the car. I also tried slicks for the first time and holy moly that is another world.

 

[Rob09msport]

I run close to stock height with ground control coil overs

 

[Rob09msport]

I could use a 7 inch spring in front and run higher than stock if I wanted

 

[AzNdevil]

Thank you very much for these suggestions

1 - why do I need stiffer springs up front? That sounds like it would increase understeer.
1 - I love the idea of adjustable dampers, and I would love to have that for sure. But all the coilovers on the market lower the car. Here's an example: https://e89.zpost.com/forums/showpost.php?p=24742317&postcount=31
I do not want to lower the car, especially not up front. And I dont see why I would want to lower the car even for track use. Some of the tracks I visit are much faster when you are able to cut the curbs. Aerodynamics is not something Im getting into, and lack stability / lots of weight transfer is something I can handle. Im not doing bumper to bumper racing as such, so I can plan the cars direction ahead.
2 - thanks to this thread, I just ordered a set of 4x 18x9 et30 wheels. They should allow me to run 250 slicks or higher in a square setup. I just posted about this in my build thread linked in my signature below.
3 - Noted. I definitely don't want more dartyness under braking from the car, but I think stiffer RTABs will solve that, and then I can move forward with toe.
4 - The other posters recommended I didn't do that?
5 - when the car rolls, the camber on the outer wheel increases, because my car is still pretty much at stock height. So roll is good, no?

I could not agree more with you on AD08R vs Zestinos. That's exactly my observation as well. I did a 1h endurance race with the AD08r a few weeks ago, and they finally started to melt. The Zestinos start to melt when you turn on the car. I also tried slicks for the first time and holy moly that is another world.

1 - stiffer springs negate the effect of macpherson design of camber reduction when the suspension moves. thats why a stiffer spring works up front
yes most coilovers lower the car but when you go with a somewhat custom coilover setups like ast/jrz you can use longer springs and retain stock height
if you want to go on the curbs i would imagine a softer sway bar being better so the suspension isnt tied together and allows the dampers to absorb the curb independently
2 - slicks are something ive never tried before but i can imagine it being like god mode
3 - i havent driven a z4 with a 0 toe/toe out setup but if its anything like a e36/e46/e90 it should be similar
4 - doesnt make sense if you ask me, the m3 control arms increases camber and caster by default...
the superpro arms just lets you play around with it and add a little more/reduce camber/caster. but then you add another variable to the mix
i am running those superpro arms. they do the job but somewhere down the road i want to test the m3 arms + mono bearing bushing on my own car to see if its any better or worse
5 - this goes back to point 1, for the front, macpherson setup, car rolls = suspension linkages move, dynamic camber reduces, thats why you need to add camber to compensate... as for the rear iirc it applies for a certain degree as well as the e36/46 runs semi trailing arm designs

all the suspension/alignment setup correlate with suspension geometry and dynamics... i am not going to pretend i understand them but a lot of details and explanations behind do float around forums in alignment/racing threads. if someones more involved in a race setup, modeling the front/rear suspension linkages in a 3d model and calculate the camber curve/toe change when the linkages move would shed more light. iirc some of this has been done for e36 and the results were summarized online

if slicks are anything like i imagined, they will exagerrate the effects of camber/toe settings

 

[Rob09msport]

1 - stiffer springs negate the effect of macpherson design of camber reduction when the suspension moves. thats why a stiffer spring works up front
yes most coilovers lower the car but when you go with a somewhat custom coilover setups like ast/jrz you can use longer springs and retain stock height
if you want to go on the curbs i would imagine a softer sway bar being better so the suspension isnt tied together and allows the dampers to absorb the curb independently
2 - slicks are something ive never tried before but i can imagine it being like god mode
3 - i havent driven a z4 with a 0 toe/toe out setup but if its anything like a e36/e46/e90 it should be similar
4 - doesnt make sense if you ask me, the m3 control arms increases camber and caster by default...
the superpro arms just lets you play around with it and add a little more/reduce camber/caster. but then you add another variable to the mix
i am running those superpro arms. they do the job but somewhere down the road i want to test the m3 arms + mono bearing bushing on my own car to see if its any better or worse
5 - this goes back to point 1, for the front, macpherson setup, car rolls = suspension linkages move, dynamic camber reduces, thats why you need to add camber to compensate... as for the rear iirc it applies for a certain degree as well as the e36/46 runs semi trailing arm designs

all the suspension/alignment setup correlate with suspension geometry and dynamics... i am not going to pretend i understand them but a lot of details and explanations behind do float around forums in alignment/racing threads. if someones more involved in a race setup, modeling the front/rear suspension linkages in a 3d model and calculate the camber curve/toe change when the linkages move would shed more light. iirc some of this has been done for e36 and the results were summarized online

if slicks are anything like i imagined, they will exagerrate the effects of camber/toe settings

our suspension actually increases camber during compression on a roll on both sides

 

[Asbjorn]

1 - stiffer springs negate the effect of macpherson design of camber reduction when the suspension moves. thats why a stiffer spring works up front
yes most coilovers lower the car but when you go with a somewhat custom coilover setups like ast/jrz you can use longer springs and retain stock height
if you want to go on the curbs i would imagine a softer sway bar being better so the suspension isnt tied together and allows the dampers to absorb the curb independently
2 - slicks are something ive never tried before but i can imagine it being like god mode
3 - i havent driven a z4 with a 0 toe/toe out setup but if its anything like a e36/e46/e90 it should be similar
4 - doesnt make sense if you ask me, the m3 control arms increases camber and caster by default...
the superpro arms just lets you play around with it and add a little more/reduce camber/caster. but then you add another variable to the mix
i am running those superpro arms. they do the job but somewhere down the road i want to test the m3 arms + mono bearing bushing on my own car to see if its any better or worse
5 - this goes back to point 1, for the front, macpherson setup, car rolls = suspension linkages move, dynamic camber reduces, thats why you need to add camber to compensate... as for the rear iirc it applies for a certain degree as well as the e36/46 runs semi trailing arm designs

all the suspension/alignment setup correlate with suspension geometry and dynamics... i am not going to pretend i understand them but a lot of details and explanations behind do float around forums in alignment/racing threads. if someones more involved in a race setup, modeling the front/rear suspension linkages in a 3d model and calculate the camber curve/toe change when the linkages move would shed more light. iirc some of this has been done for e36 and the results were summarized online

if slicks are anything like i imagined, they will exagerrate the effects of camber/toe settings

All my suspension links up front are mounted with bearings except the sway bar. At normal ride height the control arm points downwards, meaning that when the suspension compresses, the control arm moves up towards a horizontal position pushing out. I believe that increases camber?

I did not know that I could achieve stock ride height with custom ast and jrz coilovers. That is very interesting indeed!

And yes, slicks are definitely like god mode. But the noise is horrible and mine vibrated like crazy as they picked up pieces of rubber etc.

 

[AzNdevil]

All my suspension links up front are mounted with bearings except the sway bar. At normal ride height the control arm points downwards, meaning that when the suspension compresses, the control arm moves up towards a horizontal position pushing out. I believe that increases camber?

I did not know that I could achieve stock ride height with custom ast and jrz coilovers. That is very interesting indeed!

And yes, slicks are definitely like god mode. But the noise is horrible and mine vibrated like crazy as they picked up pieces of rubber etc.

sorry i dont have solid data to back it up but heres something to read, scoll down a bit and theres info for e90 rwd cars
https://www.e90post.com/forums/showthread.php?t=1330277

its still all text without actual data and stuff to back it up but it does make sense and is what ive done mostly... ymmv

 

[Asbjorn]

sorry i dont have solid data to back it up but heres something to read, scoll down a bit and theres info for e90 rwd cars
https://www.e90post.com/forums/showthread.php?t=1330277

its still all text without actual data and stuff to back it up but it does make sense and is what ive done mostly... ymmv

The posters in that thread explains that the suspension gains camber with compression up to a certain point (-20～-30mm). Therefore if the car is lowered, the front end looses the ability to gain camber with roll. And the car will roll more if lowered, as the roll center drops more than the center of gravity with this suspension. As such it makes sense to run pretty stiff springs/sway bar if the car is lowered.

My car is not lowered up front. That being said, slicks and sport tires do not generate the same roll, and ideally I would be able to compensate for that with my adjustable sway bar. But my springs are probably a wee bit on the soft side to fully support slicks, even with the stiffest sway bar setting. And I do believe that I would benefit from being able to adjust dampers as well.