[ember.m4]

Wondering if any advanced track drivers have done a before and after comparison of stock springs vs. OEM HAS on track. My guess is that it's mostly a cosmetic upgrade, and the lap time difference would be negligible, but I'm interested in hearing first-hand accounts.

[arulm3cx]

Is spring rates published anywhere ?. Anyone know if these springs are fixed or progressive.

[ember.m4]

Originally Posted by arulm3cx

Is spring rates published anywhere ?. Anyone know if these springs are fixed or progressive.

They look progressive to me, and hence there isn't really a spring rate. I assume they're slightly stiffer than stock to account for the reduced travel once lowered, but I doubt by much given the OEM comfort angle.

[PLF69]

Very interested in having feedback also. I think the G8x will develop into a very popular track day toy but for now we are at the beginning I guess..

[Ximian]

Originally Posted by PLF69

Very interested in having feedback also. I think the G8x will develop into a very popular track day toy but for now we are at the beginning I guess..

We're just about to start seeing the peak of the high quality E9x M3 aftermarket upgrades. There's still about 5 more years of aftermarket downgrades for people to try out before we find the quality modifications for the G8x.

[FranckF1]

I didn't have the chance to track my G80 before putting the HAS kit on but having run at Paul Ricard and Magny-Cours F1 tracks in France, it is pretty clear from my feelings and pictures I have from my car that it clearly helps.

It is physics anyway : 2cm lower for center of gravity, stiffer springs, always better

By how much ? This I don't have the answer...

[ember.m4]

Originally Posted by FranckF1

I didn't have the chance to track my G80 before putting the HAS kit on but having run at Paul Ricard and Magny-Cours F1 tracks in France, it is pretty clear from my feelings and pictures I have from my car that it clearly helps.

It is physics anyway : 2cm lower for center of gravity, stiffer springs, always better

By how much ? This I don't have the answer...

The physics is a bit more complicated than that. If you were to design a car from scratch for track usage, I agree you'd make it low. However, lowering a car is not the same thing because every other suspension component is already designed for the stock ride height. You end up with changes to the roll center, scrub radius, positive camber gain during cornering due to MacPherson design + lengthened stroke, etc.

Every modification has pros and cons, but it's totally possible the pros outweigh the cons here. Just wanted data to back it up, but seems like no one's really done an A/B test.

[FranckF1]

Originally Posted by sleepingplant

The physics is a bit more complicated than that. If you were to design a car from scratch for track usage, I agree you'd make it low. However, lowering a car is not the same thing because every other suspension component is already designed for the stock ride height. You end up with changes to the roll center, scrub radius, positive camber gain during cornering due to MacPherson design + lengthened stroke, etc.

Every modification has pros and cons, but it's totally possible the pros outweigh the cons here. Just wanted data to back it up, but seems like no one's really done an A/B test.

I did some hard driving on the road as an A/B test and the gain was clear. Again, I can't say how much, but the pros are clearly outweighing the cons.
Of course, for track days, the best would be to have some great coilovers...

[PLF69]

Originally Posted by FranckF1

I did some hard driving on the road as an A/B test and the gain was clear. Again, I can'ts say how much, but the pros are clearly outweighing the cons.
Of course, for track days, the best would be to have some great coilovers...

I want my cake and eat it too but I know there is always a compromise, I find the ride so good in my new G80, I will try to ride in Sport more to have an idea how the HAS can feel in comfort.

[FranckF1]

I agree with you, the ride is very good for a stock car, but I always found the comfort mode a bit too soft, with body roll.

Where I live, in France, we have the chance to have excellent roads (that's not the case everywhere but in my region, it is). So with the stock suspension, I always used the Sport or Sport+ setting to avoid this body roll.

With the HAS kit, you simply forget it and, once again, I always use Sport or Sport+, never comfort.

[Boomer 2019]

I just finished my 4th track day with the MP HAS kit on Sunday and I really believe that the car rides flatter through the corners with more confidence than with the stock suspension. As far as improved speeds go it is absolutely impossible to prove or disprove this. There are just too many variables to be scientific about it. Laps will always be faster or slower, and the reason probably has more to do with the driver than the equipment. Still, it feels noticeably better to me, and that alone is worth the installation.

A somewhat lower ride height also allows for increased -camber if the car is equipped with camber plates, and this is a big advantage when on a track. I tracked my first G82 for a year and a half with the stock suspension and camber plates. My alignment Guru set the camber at -2.5 on the front and -1.8 on the rear. This was the maximum achievable with the same settings from left to right. On this car equipped with the same camber plates but also with the MP HAS the maximum settings are -3.6 on the front and -2.4 on the rear. I do not use these settings as this is primarily my DD, and this is too much. The sweet spot for me is -3.1 on the front and -2.0 on the rear. Feels great and wears great... another benefit of the MP HAS kit.

[ember.m4]

Originally Posted by Boomer 2019

I just finished my 4th track day with the MP HAS kit on Sunday and I really believe that the car rides flatter through the corners with more confidence than with the stock suspension. As far as improved speeds go it is absolutely impossible to prove or disprove this. There are just too many variables to be scientific about it. Laps will always be faster or slower, and the reason probably has more to do with the driver than the equipment. Still, it feels noticeably better to me, and that alone is worth the installation.

A somewhat lower ride height also allows for increased -camber if the car is equipped with camber plates, and this is a big advantage when on a track. I tracked my first G82 for a year and a half with the stock suspension and camber plates. My alignment Guru set the camber at -2.5 on the front and -1.8 on the rear. This was the maximum achievable with the same settings from left to right. On this car equipped with the same camber plates but also with the MP HAS the maximum settings are -3.6 on the front and -2.4 on the rear. I do not use these settings as this is primarily my DD, and this is too much. The sweet spot for me is -3.1 on the front and -2.0 on the rear. Feels great and wears great... another benefit of the MP HAS kit.

Makes sense. Are you running stock tire/wheel sizes? If so, are you running spacers with this setup? I assume being lowered at 3.1 degrees of neg camber without spacers would make the top of your tires completely disappear into the wheel well. Of course, this is more of an aesthetic concern than a performance one. Any chance we could get a photo of your car's stance as well?

[PLF69]

Originally Posted by Boomer 2019

I just finished my 4th track day with the MP HAS kit on Sunday and I really believe that the car rides flatter through the corners with more confidence than with the stock suspension. As far as improved speeds go it is absolutely impossible to prove or disprove this. There are just too many variables to be scientific about it. Laps will always be faster or slower, and the reason probably has more to do with the driver than the equipment. Still, it feels noticeably better to me, and that alone is worth the installation.

A somewhat lower ride height also allows for increased -camber if the car is equipped with camber plates, and this is a big advantage when on a track. I tracked my first G82 for a year and a half with the stock suspension and camber plates. My alignment Guru set the camber at -2.5 on the front and -1.8 on the rear. This was the maximum achievable with the same settings from left to right. On this car equipped with the same camber plates but also with the MP HAS the maximum settings are -3.6 on the front and -2.4 on the rear. I do not use these settings as this is primarily my DD, and this is too much. The sweet spot for me is -3.1 on the front and -2.0 on the rear. Feels great and wears great... another benefit of the MP HAS kit.

I tried to find what was your car but maybe missed it and I don't see signatures on my phone, RWD ? AT/MT ? AWD ?

[Boomer 2019]

Originally Posted by sleepingplant

Makes sense. Are you running spacers with this setup? I assume being lowered at 3.1 degrees of neg camber without spacers would make the top of your tires completely disappear into the wheel well. Of course, this is more of an aesthetic concern than a performance one. Any chance we could get a photo of your car's stance as well?

No, I don't use spacers, and yes, the tops are tilted inward pretty much. However, aesthetics are not my concern, performance is. Unfortunately when I wanted to take some pics yesterday I discovered that my camera has died. I ordered a new one but it will take a few days.

[Boomer 2019]

Originally Posted by PLF69

I tried to find what was your car but maybe missed it and I don't see signatures on my phone, RWD ? AT/MT ? AWD ?

My car is a 2023 M4 Comp RWD.

[PLF69]

Originally Posted by Boomer 2019

My car is a 2023 M4 Comp RWD.

Thanks, your review on track is most interesting, I ran -3.0 in the M4C Vert (AWD) last summer and corded the inside of both front cup2s in 4 track days, the sucker was hard to slow down with its added weight + around 3500km between 3 tracks.

My new M3 in sport mode feels much more planted with less body roll on the street but eager to feel it on track with stickier tires. I rode a lot today in sport mode and think I could live with it. Would you say HAS comfort feels like OEM Sport or it's different since we are talking about different springs vs changing de damping calibration ?

[GTS Daddy]

Originally Posted by PLF69

...Would you say HAS comfort feels like OEM Sport or it's different since we are talking about different springs vs changing de damping calibration ?

I like this question. Would someone be able to comment with a modest amount of lowering how the MPHAS kit feels with comfort mode engaged compared to the stock suspension in comfort?

[M4nication]

Very interesting thread. Got about 6 months for my '24 M4 Comp to arrive, and I optioned the MP HAS. Seems it was the right choice from a aesthetics standpoint, just hoping the performance has some benefits too (I love hitting the canyons, plenty of those here in Los Angeles). Following!

[ember.m4]

Originally Posted by Boomer 2019

No, I don't use spacers, and yes, the tops are tilted inward pretty much. However, aesthetics are not my concern, performance is. Unfortunately when I wanted to take some pics yesterday I discovered that my camera has died. I ordered a new one but it will take a few days.

I guess from the performance angle, with spacers you do gain track width, lower roll center, and decreased weight transfer. However, you also change the scrub radius (although camber plates also do this). There's also more strain on the wheel hub, and it's probably less safe. Not sure how it all computes tbh.

[Boomer 2019]

Originally Posted by PLF69

Thanks, your review on track is most interesting, I ran -3.0 in the M4C Vert (AWD) last summer and corded the inside of both front cup2s in 4 track days, the sucker was hard to slow down with its added weight + around 3500km between 3 tracks.

My new M3 in sport mode feels much more planted with less body roll on the street but eager to feel it on track with stickier tires. I rode a lot today in sport mode and think I could live with it. Would you say HAS comfort feels like OEM Sport or it's different since we are talking about different springs vs changing de damping calibration ?

I have always run on stock wheels with MP4s. Like I said this is my DD and I am fine with never setting any records, and Verstappen is not looking over his shoulder and worrying about me. That said, I am a solid Intermediate/Advanced driver and do track the car in a serious frame of mind.

On my previous G82 M4 Comp with the -2.5 front camber the tire wear was heaviest from the midline to the outside edge. I would get scalloping of the outside tread and some rollover after 3-4 days but never any cording. I was changing the front tires after 5-6 days, and the rears at 10-11 days. I have only done 4 days in this car with the MP HAS kit and -3.1 front camber, but I can already see a marked difference in the wear pattern. There is absolutely no rollover on either the inside or outside edges. The wear has remained within the tread. Also the wear is even across the width of the tires. This bodes well for the future. I am already a big fan of the kit.

As for the the feel in the 3 ride settings I am not the person to ask about this. I have never, repeat never driven any of my BMW's in Comfort mode. It's an M. If someone wants soft, cushy, and quiet then why do they buy an M? I can tell you that the kit does give a noticeably stiffer ride than the stock set up. For DD I leave the suspension in Sport and it is perfectly comfortable as far as I am concerned (your tush-o-meter may vary). Also in South Florida we have well maintained and smooth roads as compared to many other parts of the country. On the track it is Sport+ although sometimes on the street as well.

[arulm3cx]

Any comparison on rear getting wiggly/squirm on high speed hard braking. (150+ to 40+) with stock springs. I believe stiffer springs would help with this. I'm still learning so if this is s stupid questions please disregard.

[PLF69]

Originally Posted by arulm3cx

Any comparison on rear getting wiggly/squirm on high speed hard braking. (150+ to 40+) with stock springs. I believe stiffer springs would help with this. I'm still learning so if this is s stupid questions please disregard.

I also felt this at my track day last week, my alignment is -2.0 camber and 0.20 total rear toe so I don't think it is alignement related. The rear does get squirlly on situations you described.