AST lowering springs review + a mouthful of talk about springs

Tom over at European Auto Source has done a very comprehensive review on the AST lowering springs. I haven't come across any AST customer reviews, so I guess this is the first.

I just hit 50k miles, so warranty is over which means it's time to mod!

Quickly, the purpose of lowering springs is for aesthetic but also for performance. Some of you may be leaning towards one more than the other. For me, it was more of performance that I was looking for. My previous experience has been running Koni Yellows with H&R springs on a 2002 Toyota Rav4 and TEIN Basic coilover kit on a 2005 Mercedes C230 Kompressor Sports Sedan. This is the first time I've ever owned a lowered car with only springs so I wasn't sure what to expect as far as performance nor longevity of the rest of the suspension components - still don't but time will tell.

I don't have H&R's to compare the AST's to, but I can tell you from riding on AST's on installation day for about 45 miles that the ride is very close to stock. In fact, anyone who sits in the car or drives it won't be able to tell anything has changed. I can barely tell myself. It's that similar. In a way though that was a bit disappointing to me. I was hoping for a stiffer ride so that the car doesn't sit back before it moves off the line.

The i3 isn't exactly a popular car for modding so I suspect the community here may not be that technical as far as mods go. I'm sure some of you gear heads know a ton more than me so I'm not saying I'm the expert but wanted to just discuss some basics before going in depth with the AST lowering springs application on the i3 REX.

ABOUT SUSPENSION (skip this part if you know this stuff already and go straight to the review section below)
A stiffer ride typically accentuates the terrain. On smooth roads, a stiff suspension will feel super smooth. On rough roads, you can almost count all the bugs you run over. Stiff suspension is less bouncy but more jaring. I like to think of it like jumping on the floor vs jumping on the bed. When you jump on the floor, there's no bounce. Your body absorbs the full drop as your feet hit the floor. Jumping on the bed however is followed by more bouncing. There's a lot less force on your legs, but your body will bounce over and over until the momentum dies off.

So with stiffer suspension, every bounce is aggressive and you'll feel it to the bone. Once you hit uneven terrain, you experience the terrain and then it's over (until you hit the next one). Softer suspension will be more bouncy. You experience less degree of impact but each impact extends in duration. Big bounce followed by more bouncing, each progressively softer.

SPRINGS FOR LOOKS
My guess is that most people here feel that the stock suspension is already pretty stiff and are considering springs mainly for looks. If that's you, then the AST's will be it. Don't think too much about it - just get it. Generally lowering springs need to be stiffer b/c as it reduces the space between the tire and the inside of the wheel well, it needs to be stiffer so the car doesn't bottom out. The science of all this with manufacturers is to find the balance of exactly how low vs how stiff.

SPRINGS FOR PERFORMANCE
Wish suspension upgrades, I'd want the car to not sit back at launch. Generally when a stock car accelerates, the car will sit back briefly on the rear wheels before actually moving forward. I'd rather the car just move forward initially without sitting back and because of that, I like upgrading the suspension.

When stopping, the opposite happens. Stock cars will dive down at abrupt stops. All the weight goes to the front wheels and the car literally dives down. It's very aparent when looking at the car from the side. A car with stiffer suspension won't have to experience that. Instead of diving down on the soft front suspension, the stiffer setup allows the car to just stop.

The third component of course is turning. On a turn, the car naturally puts more force on the outside wheels compressing the suspension components which include the spring. If the spring can be stiffer, you can imagine that there's less body roll b/c it's fighting or pushing back against the road.


AST LOWERING SPRINGS REVIEW
The ride is as soft as stock. You're not really going to notice a difference even if you're looking for it. I'm still not certain I can tell the difference yet, albeit I'm not taking sharp turns and not driving aggressively on my way home from the shop with kids. Again, if you're looking for a stock "feel", just get these AST springs. If you share the car with a counterpart, I'd be surprised if they noticed the difference at all.

Since I'm lowering the car for performance, it was a little disappointing that the setup isn't noticeably stiffer. But then again, this is the first time I've lowered a car with only springs so may this is the "norm" of what to expect. I'm just used to entire suspension components being swapped out which has a huge impact. I have read that customers of H&R have complained about their setup being too stiff so I'm assuming it's noticeably different. As I'm the primary driver of the i3 (wife has driven it a total of 8 times in 16 or so months), maybe I should've gone with H&R after all.

CONCLUSION
If you're reason for getting springs is performance oriented, I'd probably recommend the H&R's even though I myself haven't ridden on them before.
If you're reason for getting springs is more about looks and you're not looking for any performance differences or may even be worried about it making the car too stiff, then the AST's are the perfect fit.

Pics to follow. It's nothing surprising. About a 1" drop on all corners. The car was just lowered today, so nothing substantial to show off yet. Just wanted to get the review out there.

UPDATE after 1,500+ miles of driving on AST lowering springs (with spacers):

At city speeds, I still don't find it any more harsh than the stock suspension. The only time I notice any discomfort is when going over the speed bumps that are painful for any car. You know the black ones that don't gradually raise in elevation. The ones that are made of some sort of rubber-like substance that are maybe only a foot deep and maybe 5" tall, those.

COMPARISON TO STOCK SUSPENSION:
When you hit the limit at speed with the stock suspension on a curve over the freeway, the car lets you know very abruptly. It reminds you that you're in an urban car driving faster than you're supposed to go. I wouldn't say there's a lot of body roll on stock suspension b/c it doesn't really give you enough time to feel that. The car performs just fine and then all of a sudden when you hit the limit, it shouts at you to ease off the accelerator. It's not the speed that scares you. It's the feeling of it potentially tipping over even though you've seen enough i3 drifting videos to know it'll do just fine.

I can't tell you if it's the lower center of gravity or mostly the spring rate, but when paired with the spacers, it raises the level of tolerance for speed on a curve. When you hit that limit further on the speedometer, the car no longer feels like it's going to fall over. Instead, it lets you fight it. I'm not going to say it sits on rails and stays flat across the full turn b/c it's no Lotus. It stays planted to the road at sharper turns at higher speeds than the stock setup but that doesn't mean it doesn't need your attention.

Remember that moment where you felt you were going too fast in the i3 on a turn at high speed? Well, the turn gets sharper and the speed gets faster before that same moment comes along. The car is composed for longer. It's got a higher level of tolerance than it did. You're more comfortable for longer and when you do feel like the i3 needs your attention, it tells you that you can do it but you better hold on. As you fight the steering wheel, you can keep the pedal pressure on. It'll take you around the curve just fine. Just make sure you're paying attention.

A SPORTS CAR IT IS NOT
Will the lowering springs make the car feel like some fancy sports car? No, but I also don't think that was the point. It'll get rid of the feeling of toppling over and replace it with confidence to turn harder at higher speeds. As long as you're not expecting it to feel like a Mini Cooper, you'll enjoy your set of AST Suspension springs as an improvement over the stock feel of the OEM i3.

MORE UPDATES:
I feel like at higher speeds, rather than feeling like it's going to tip like it did with stock suspension, the car feels like it would oversteer. Trying to keep it safe on the public roads, but I did take a freeway curve at 86mph and it still feels planted. Felt as comfortable on the same curve as if I were going 72mph.

So not only is the limit coming in at higher speeds compared to the stock suspension setup, but the threshold is bigger. When it does feel like it's hitting the limit, it lets you continue at still higher and higher speeds. I won't be doing anything unsafe on public roads so any further testing will need to be done on a track. That won't be happening until December so I'll provide some updates then.

When going too fast on speed bumps (and I'm already going very slow over them), the car can bottom out. That gives you an idea of how soft the springs still are. It's not going to eat away at your comfort if you're worried about that. I can't speak for H&R springs, but it's worth mentioning that many have reported that they're too stiff. Somewhat of a subjective statement, so take that with a grain of salt.

Thanks for sharing this info man. I'm new to the platform as I just picked up an i3 REx last week, and this certainly helps me make a decision on springs. I do know what you mean about the airy toppling over feel this car has due to its profile. I've modded all my sports cars, so the mod bug is still there even for this EV lol. But after reading your review, it seems AST is best for people looking for stock feel with a conservative drop for looks. I think I will go the H&R route, as it seems to be a little stiffer and lower.

Glad the AST review helped you make your decision. It wasn't meant to convince anyone one way or the either so glad you saw it that way and made a choice of H&R's for your particular interest.

I recently fitted a set of AST springs (ASTLS-14-2686) to my UK 2017 94Ah REx and are very pleased with the result. With the stock springs the ride was choppy when going over bumps and undulations. It did not respond well to sudden changes in direction and felt rather vague at higher speeds. However, I should point-out that previous car was a 2016 Focus ST. With the ASTs the driving experience is way better and to my mind what BMW should have fitted originally. The choppiness and pitching has pretty much gone and car feels so much more planted on the road. Fast turn-in to corners is no longer the nerve racking experience it was before and the steering has more feel. The good thing is that this improvement has not come at the expense of comfort as the ride is pretty much as plush as before, I would say it's hardly any bumpier at all.
On motorways and dual carriageways it feels a lot more stable and is less susceptible to side winds. It feels like it wants to go faster and eat its battery
So i'm very pleased with the upgrade and would recommend AST. It would have taken me about half a day to do all four corners if I had not taken the time to clean all the corrosion off and paint the aluminium top mounts. Not sure why BMW didn't put any protection on them...

I'm coming from an R53 Mini Cooper JCW, which is a stiffer than most sports cars. I love my '14 i3 BEV, but the steering is floaty with way too much body roll. Ideally I'd like a little softer of a ride than my R53, but if the handling will be anything alike, I'm in.

What parts am I looking at besides springs? I really dont care about lowing, just driving feel. What should I do first?

I already bought a set of ASD springs but never installed them. I'm worrying about the ground clearance and the battery being the first to take a hit.

Thank you for the comprehensive postings on the AST lowering springs. I was curious why at the end you thought you should have gone with H&R's. Has anybody tried to use the stock springs from the i3S? I was wondering if the lowered position of the rear springs affected or even accentuated the negative camber? I really would like to decrease the camber settings if possible. I have lowered almost all my cars including Porsche 911, Jaguar XKE, Bertone, and even my Rolls-Royce. The Mercedes is lowered through the hydraulic suspension and the Porsche just through settings on the torsion bar. Did you do the spring exchange yourself? I was wondering which spring compressor you used since the spring to shock distance is very tight.

On the subject of suspension, have you looked into wheel and tire replacements?

How does this compare to a stock i3s?

I just installed the ASTs on my 2017 i3. Bought them from Tom at european auto source and I am extremely happy with the customer service. I could've saved extra $40 if I chose an alternative vender but his support throughout the process was incredible. Additionally, the photos they have included in forums really tell the story.
The springs + spacers (12mm front & 15mm rear) arrived super fast (west to east coast during covid and holidays) and yesterday I had a chance to install them. The front took me 2 hours 20min and the rear almost 4.5 hours (including two trips to autozone). First of all, I want to say, I don't own a garage, so everything was done in my DC backyard.
I was surprised that the rear had a lot more going on and space was very limited. Additionally, BMW decided to introduce torx bolt on the rear suspension so I had to make two trips to autozone to get the necessary tools.
Overall, I like the look and that's how it should've rolled out from the factory, in my opinion. It's not aggressive at all. I wasn't looking for a slammed i3 for various reasons. I have not tested the handling at a highway speed yet nor cornering, but I am happy to report back if anyone is interested.

nice, pics please?!

this would be your best reference: https://bmwi.bimmerpost.com/forums/showthread.php?t=1621692

I can't comprehend that nobody can provide the rates of these springs.

... and refuse to buy any springs without knowing that.

Obioban said:

I can't comprehend that nobody can provide the rates of these springs.

... and refuse to buy any springs without knowing that.

Click to expand...

really? why?

GoldiE46 said:

Obioban said:

I can't comprehend that nobody can provide the rates of these springs.

... and refuse to buy any springs without knowing that.

Click to expand...

really? why?

Click to expand...

Because the overwhelming majority of aftermarket springs, including those from "reputable" companies, are set up for form over function.

I don't want to make the car into a pitchy mess.

I'm reasonably handy and not above tackling this install myself, but I just want opinions from those who swapped their own springs - aside from the Torx issue, level of difficulty from 1 (unlocking your door with the key) to 10 (swapping your REx motor for a 5.0 V8)?

4 months and about 3k miles later, including a trip DC - Savannah GA, I can say that I am very happy with the results. The car handles much better, especially at highway speed. DC roads are extremely bad, but the ride is still similar to stock. HAPPY