Suspension feedback wanted

[JPuehl]

I know this is not the best way to solicit feedback about a suspension setup but was wondering if anyone had any feedback based on the picture from a recent autocross about how it appears my suspension is working and if any changes could/should be made. My car is mainly my DD with emphasis on autocross but not prepped for a specific class, my wife and I race in “time only” classes at our local clubs and just compare times to our friends and other cars. Currently my setup is Koni SA shocks, Swift Spec R springs (so 201 lbs front and 503 lbs rear), an E93 M3 front sway bar and control arm bits, Ground Control street front camber plates with 3.3* front camber, a touch of toe out, 1.7* (I believe) camber in the rear with a touch of toe in. The tires 255 RE71s. I like the setup am thinking about “upgrading” to coil-overs in the next year or so. I’ve had my current setup for about 3 ½ years now and have read that the Swift springs sag over time, and I’m thinking about maybe a little more spring rate. As it is, I made ½” spacers when I put the suspension together because I thought the Swift springs made the car too low. Anyway, thanks for any feedback.

[lowside67]

Not surprised the car is rolling like crazy in the front on 200lb-in springs with 255 RE71Rs. I am running with ~400s and have just bought 500s to test with as the car still feels undersprung in the front to me.

-Mark

[JPuehl]

Originally Posted by lowside67

Not surprised the car is rolling like crazy in the front on 200lb-in springs with 255 RE71Rs. I am running with ~400s and have just bought 500s to test with as the car still feels undersprung in the front to me.

-Mark

That's what I'm thinking as well, just want to find a decent balance for DD and autocross. I didn't realize the car was rolling this much until I saw the pix from this even. Coil-overs and "stiffer" springs are on my list of future upgrades.

[Ginger_Extract]

Ditch the M3 bar, it's trash. Get stiffer springs.

[John_01]

I don't think the front stiffness is the only issue here. Looks like there's no trouble to lift the inside front wheel.
The real problem with the Spec-R front springs, is that due to the lowered height the car is always riding the bump stops.

Anyway it seems like a good time to upgrade to coilovers.

[JPuehl]

Originally Posted by Ginger_Extract

Ditch the M3 bar, it's trash. Get stiffer springs.

This seems to be the next upgrade I'll be doing.

Originally Posted by John_01

I don't think the front stiffness is the only issue here. Looks like there's no trouble to lift the inside front wheel.
The real problem with the Spec-R front springs, is that due to the lowered height the car is always riding the bump stops.

Anyway it seems like a good time to upgrade to coilovers.

I've read a review from someone that the Spec-R springs sag after time. I've had them on my car for over 3 years now and I think I agree with that statement. I also noticed the springs have contacted each over so they are soft and short. But you're right, time for a new front bar and coilovers. I need to re-read all the STU build threads and figure out which coilover to go with and what rates to at least start with. I believe a 7" spring is what I read most people use.

[John_01]

I don't understand the comment that the E93 M3 front sway bar is trash. That needs a bit more explanation to put it into context.
The situation is going to change a lot with new coilovers, so I don't see how that can be a universal conclusion.

[JPuehl]

As a temporary "fix" I ordered the Hotchkis 33mm front bar which should arrive today, get installed on Saturday and tested Sunday morning at a local autocross event. New springs/shocks are on the "to-do" hopefully over the Winter.

[bbnks2]

Originally Posted by JPuehl

As a temporary "fix" I ordered the Hotchkis 33mm front bar which should arrive today, get installed on Saturday and tested Sunday morning at a local autocross event. New springs/shocks are on the "to-do" hopefully over the Winter.

Sorry, but, what exactly are you trying to "fix?" Maybe I glanced over it but I don't recall seeing you say there was anything wrong...

OE style struts like Koni paired with mild spring upgrades like swift is going to ride on the bump stops just like the OE setup does. It takes a lot more spring rate to keep off the bumps stops when you only have ~4-5in of total suspension travel to play with. Dial in a lot of rebound for autocross to keep the car down on the bump stops.

Swift springs dial in a lot of rake and drop the car lower than I like, personally. That is a lot of what you see in the pic. Does the car handle neutral or not? Coilovers will be a much different ball game to tune since they usually eliminate the "spring supports" of OE struts but don't come with springs stiff enough to stay off the bump stops. Changes from steady state travel to under-steer/over-steer become much more transparent and abrupt when there is no spring supporter in place.

My thoughts are that with the sway bar upgrade your next post will be "how do I get rid of all this terrible under-steer."

[JPuehl]

Originally Posted by bbnks2

My thoughts are that with the sway bar upgrade your next post will be "how do I get rid of all this terrible under-steer."

Turns out you're wrong. The car didn't have any new/additional under-steer and did well, hard to same if it was any better though. I did co-drive with a national level driver who liked the car and said it was well balanced but felt the boost comes on "a bit aggressively". He also beat my by 3 seconds on a roughly 55 second course. I'm still .1 second slower than the 2 '18 M2's that show up but I'm getting closer to their times.

[bbnks2]

Originally Posted by JPuehl

Turns out you're wrong. The car didn't have any new/additional under-steer and did well, hard to same if it was any better though. I did co-drive with a national level driver who liked the car and said it was well balanced but felt the boost comes on "a bit aggressively". He also beat my by 3 seconds on a roughly 55 second course. I'm still .1 second slower than the 2 '18 M2's that show up but I'm getting closer to their times.

MHD just released torque reduction by gear.

[JPuehl]

Originally Posted by bbnks2

MHD just released torque reduction by gear.

Thanks. I have the JB4 boost control and JB4 BEF, I limit 1 gear boost to 5 lbs when racing and can limit boost in 2nd and 3rd as well, but that doesn't slow down the delivery of the boost. There is a map 6 where you can set max boost in 500 rpm intervals I might play with over the winter. I'll do some reading on the MHD torque reduction also.

[bbnks2]

Originally Posted by JPuehl

Thanks. I have the JB4 boost control and JB4 BEF, I limit 1 gear boost to 5 lbs when racing and can limit boost in 2nd and 3rd as well, but that doesn't slow down the delivery of the boost. There is a map 6 where you can set max boost in 500 rpm intervals I might play with over the winter. I'll do some reading on the MHD torque reduction also.

The turbo spool in about 260rpm... It delivers torque like an N/A motor at low rpms. Scale the boost back in 2nd gear to reduce torque. The shorter gear ratio of 2nd gear acts as a torque multiple and even 11psi in 2nd is enough to drift through autocross with ease. Feels slow in a straight line but drop boost back to 8psi (basically stock) or so at <4000rpms. Bring it up linear fashion up to like 15psi toward 6k+.

[JPuehl]

Originally Posted by bbnks2

The turbo spool in about 260rpm... It delivers torque like an N/A motor at low rpms. Scale the boost back in 2nd gear to reduce torque. The shorter gear ratio of 2nd gear acts as a torque multiple and even 11psi in 2nd is enough to drift through autocross with ease. Feels slow in a straight line but drop boost back to 8psi (basically stock) or so at <4000rpms. Bring it up linear fashion up to like 15psi toward 6k+.

Thanks, I'm going to work on this over the Winter. A friend mentioned that some people are trying to boost by throttle position which I don't think would work for auto-cross, boost by rpm will probably end up being better.

[bbnks2]

Originally Posted by JPuehl

Thanks, I'm going to work on this over the Winter. A friend mentioned that some people are trying to boost by throttle position which I don't think would work for auto-cross, boost by rpm will probably end up being better.

Linear throttle is very nice imo and could be another way to explain why "boost feels like it comes in too hard." Stock throttle mapping is too aggressive and basically works like an on/off switch. MHD has linear throttle as an option and it makes the car much easier to modulate. I am sure BMS has a BEF with linear throttle mapping available too.

JB4 tuning for 2nd gear would definetly help if you want to limit boost (torque) in the lower rpm range.

[Kgolf31]

Sure front spring seems a tad soft - but depends if the car is compliant and doing what you want it to do.

"Roll" isn't a bad thing, as long as the car is loading and behaving as it should then there is no need to take immediate action on it.

I guess IMO I need more information on actual car behavior before for certain I can agree that upgrading suspension is the right way to go. Sure SA Koni's are an entry level shock, but if you don't know what is wrong with the car or what you want to improve throwing $4000 shocks won't fix anything. Just IMO.

Just to show that roll isn't always bad:



And to more extremes: