Positive Caster to yields greater dynamic camber

[DRLane]

Guys/Gals, would love your help.

Been reading about suspension setups
and while I hear everyone talking about the importance of camber, rarely is there a mention of caster. My understanding is positive caster is indirectly proportional to dynamic camber thus Increasing positive caster, increases negative camber when cornering? Other benefits would be increased stability at high speeds?

Just playing with my suspension, increasing caster reduces the available camber, as the plates are restricted by the chassis mount cutouts. But it's dynamic we should care about right?

Note this is my street setup, but on the track I run 275/295, with about -3.8 degrees of camber.

So, are y'all running larger positive caster than say 7.5 degrees? If so what's your experience? Without a measuring device I'm dependent on the shop alignments. But I want to play with the adjustments and test fit myself. For those with measuring devices are they worth it?

[dparm]

I run about 7.5 up front, and since my car has adjustable rear caster, I set it to the GM recommendation of zero.

Positive caster enables increased negative camber on the outside wheel during cornering, yes. It also makes the car more stable at speed because the wheels will naturally want to return to pointing straight ahead (I think I explained that right). My dad once explained it to me by challenging me to give a shopping cart a shove in an empty parking lot...it will basically go straight until it runs out of momentum.

There's not a lot of talk about rear caster because so few cars allow that to be adjusted, but my understanding is that any sort of rear caster will cause unintended rear-wheel steering.

There is almost no reason not to run caster up front. That's why people don't really talk about it -- commonly accepted practice.

[SYT_Shadow]

Front caster is very interesting. It allows you to dial in less camber for the straights and then in turns it has more camber.

Remember that camber is great for turns, but bad for braking/accelerating. Adding caster allows you to have a bit less camber in the straights and still have the proper amount in turns.

In the E9X you can adjust caster very slightly with the right camber plates, but adding some is useful.

[DRLane]

Thanks!

I'll have to measure how much caster I'm running as it's currently maxed out. Then I can measure the available static camber available given the top of the strut gets blocked by the chassis from moving inward any further.

[SYT_Shadow]

Originally Posted by DRLane

Thanks!

I'll have to measure how much caster I'm running as it's currently maxed out. Then I can measure the available static camber available given the top of the strut gets blocked by the chassis from moving inward any further.

yup, I have the same situation on my E90 M3

[dparm]

Originally Posted by SYT_Shadow

Remember that camber is great for turns, but bad for braking/accelerating. Adding caster allows you to have a bit less camber in the straights and still have the proper amount in turns.

Bingo. It will allow you to get the best of both worlds -- not sap straightline power with excessive negative camber, but still have the negative camber you want in the corners.

[DRLane]

I feel like it should be a stronger selling point to go with race plates vs street.

[SYT_Shadow]

Originally Posted by DRLane

Bingo. It will allow you to get the best of both worlds -- not sap straightline power with excessive negative camber, but still have the negative camber you want in the corners.

I feel like it should be a stronger selling point to go with race plates vs street.[/QUOTE]
It should be, unfortunately the amount you can adjust is tiny

[DRLane]

That's what I want to measure. What's the max caster you can get with race plates.

[SYT_Shadow]

Originally Posted by DRLane

That's what I want to measure. What's the max caster you can get with race plates.

Whatever I have on the E90 is pretty much the max, but I don't have the alignment sheet

[Lynch]

Afraid to turn this into another alignment spec thread but gotta have to ask, what sort of alignment specs are you guys on for reference?

My alignment specs is currently similar to this:
Front:
-1/32" toe out per side
-1.6* camber per side
Rear:
+1/16" toe in per side
-1.9* camber per side.
Thrust Angle = 0.00

I understand camber and toe, but now I'm trying to figure out what would I want to set caster in the front to?

I also came across these SPL adjustable front caster rod bushings:
https://www.splparts.com/products/ad...x-e8x-f8x.html

My initial thought was to just eliminate deflection in the front control arms, but now I would like to learn the benefits/downsides of messing with front caster.

Speaking with the SPL engineer, this would add only about 2 degrees of caster. I thought messing with caster would increase dynamic camber at the expense of increasing mid-cornering instability, but I was told this was not the case, as the bushing adding only 2 degrees would not be able to affect it to that degree.

Hopefully I can get some feedback on my alignment specs and how caster would help it.

My E92 is dual duty and used for high-speed canyon runs, highways, some autocross and track, and remaining 50% daily commuting.

[DRLane]

Originally Posted by Lynch

Afraid to turn this into another alignment spec thread but gotta have to ask, what sort of alignment specs are you guys on for reference?

My alignment specs is currently similar to this:
Front:
-1/32" toe out per side
-1.6* camber per side
Rear:
+1/16" toe in per side
-1.9* camber per side.
Thrust Angle = 0.00

I understand camber and toe, but now I'm trying to figure out what would I want to set caster in the front to?

I also came across these SPL adjustable front caster rod bushings:
https://www.splparts.com/products/ad...x-e8x-f8x.html

My initial thought was to just eliminate deflection in the front control arms, but now I would like to learn the benefits/downsides of messing with front caster.

Speaking with the SPL engineer, this would add only about 2 degrees of caster. I thought messing with caster would increase dynamic camber at the expense of increasing mid-cornering instability, but I was told this was not the case, as the bushing adding only 2 degrees would not be able to affect it to that degree.

Hopefully I can get some feedback on my alignment specs and how caster would help it.

My E92 is dual duty and used for high-speed canyon runs, highways, some autocross and track, and remaining 50% daily commuting.

Street:
Front ~2* camber, neutral toe
Rear ~1.9* camber (maxed on stock arms) 1/8" toe in.

Differences between street and track are maxing out the front camber at roughly 3.8*. But I haven't measured the impact from maxing out the caster. Need to buy a camber/caster gauge.

What camber plates are you running today? Also, not sure I follow how caster impacts and or increases midcorner instability?

[dparm]

Originally Posted by Lynch

Afraid to turn this into another alignment spec thread but gotta have to ask, what sort of alignment specs are you guys on for reference?

My alignment specs is currently similar to this:
Front:
-1/32" toe out per side
-1.6* camber per side
Rear:
+1/16" toe in per side
-1.9* camber per side.
Thrust Angle = 0.00

I understand camber and toe, but now I'm trying to figure out what would I want to set caster in the front to?

I also came across these SPL adjustable front caster rod bushings:
https://www.splparts.com/products/ad...x-e8x-f8x.html

My initial thought was to just eliminate deflection in the front control arms, but now I would like to learn the benefits/downsides of messing with front caster.

Speaking with the SPL engineer, this would add only about 2 degrees of caster. I thought messing with caster would increase dynamic camber at the expense of increasing mid-cornering instability, but I was told this was not the case, as the bushing adding only 2 degrees would not be able to affect it to that degree.

Hopefully I can get some feedback on my alignment specs and how caster would help it.

My E92 is dual duty and used for high-speed canyon runs, highways, some autocross and track, and remaining 50% daily commuting.

I would run 7-8 degrees of caster up front. There is almost no downside to doing so.


I'm a bit confused why you're running more negative camber in the back than up front. I think 1.5-2.0 all the way around is sufficiently aggressive for a DD that's driven spiritedly and/or occasional track use. Toe eats tires much faster than camber. I will defer to the experts on what works well for a hybrid scenario like yours.