AST 4100 coilover suspension (and wheels/tires)

This is more like a teaser at this point, since I don't have many pics to share. But I wanted to post something.

Relevant specs:
AST 4100 coilover suspension
8kg/mm (~450lb/in) FR, 7kg/mm (~390lb/in) RR
6" spring FR + helper, 8" spring RR
Current ride height (change from stock): -1.2" FR, -1.0 RR

Kosei K4R 17x8 with Michelin Pilot Super Sport 225/45-17

Coilover suspension reduced unsprung weight by 16lbs (6lbs each FR corner, 2lbs each RR corner)
Wheels/Tires reduced unsprung weight by 18lbs (4.5lbs each corner)


Best pic I could get in the confines of my garage:



Nice chunky outer tread blocks:


I may go a bit lower in the future. Zero rubbing at current ride height, and clearances look really good - I could go a LOT lower without rubbing if I wanted, I think.

Haven't done a real alignment yet (no time), but a very (very) quick string setup says the moderate lowering hasn't affected things much. Keeping a very close eye on tire wear just in case.

The ride is excellent. Seriously, get rid of those Toyos, NOW. Seriously. I always found the most objectionable aspect of the stock vehicle's ride to be noise/harshness over small high frequency impacts like pavement seams, bridge expansion joints, or tar strips, and installing the AST suspension made this characteristic a bit worse (the rest of the ride motions and vehicle control were improved, it was just this aspect of the ride that I didn't like). The sharp sound and impact (like a 3 year old kicking your seat) really bugged me. I was afraid that the Michelins would be even worse yet – conventional wisdom says that a higher performance, lower profile (went from 16” to 17” wheels) tire will be less comfortable, but that was utterly and completely wrong. The Michelin Pilot Super Sports are seriously better in every way – turn-in, ultimate longitudinal grip, lateral grip, noise, ride comfort, everything. (Well, cost is probably the one category where the Toyos win but I’m not counting that). The sharp impacts are now a barely perceptible dull thud. I'm am very impressed with this tire and can barely recommend it enough.

I'll post some more detail and pictures in the future.

Here's a crappy cell phone pic, of a dirty car, taken in a parking lot, on a dreary day...



So photography... much suspension... such wheels... wow.

8kg/mm (~450lb/in) FR, 7kg/mm (~390lb/in) RR
6" spring FR + helper, 8" spring RR

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Would you happen to know off hand if the AST suspension uses 2.5” or 3” ID springs for F/R? Did you have to use another upper/top perch to fit the rear springs?

It sounds like only the front uses a helper spring but not the rear? It looks like a independent spring and not welded/fused onto the main spring, is that correct? Do you happen to know the rate of the helper springs F/R?

Btw, looking good!

sac02 said:

Kosei K4R 17x8 with Michelin Pilot Super Sport 225/45-17
*
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(Well, cost is probably the one category where the Toyos win but I’m not counting that). The sharp impacts are now a barely perceptible dull thud. I'm am very impressed with this tire and can barely recommend it enough.

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oof. i'm jealous. there's no way i'd be able to throw away brand new tires for a set of $640 Michelins. I'm on the stock 17"s 205/50s, and they're pretty cushy.

Silentnoise713 said:

Would you happen to know off hand if the AST suspension uses 2.5” or 3” ID springs for F/R? Did you have to use another upper/top perch to fit the rear springs?

It sounds like only the front uses a helper spring but not the rear? It looks like a independent spring and not welded/fused onto the main spring, is that correct? Do you happen to know the rate of the helper springs F/R?

Btw, looking good!

Click to expand...

The springs are Swift (Japanese mfg, good quality from what I can tell). Both FR and RR are 60mm ID (2.37"). The FR are 6", 80N/mm, with an 80mm 20N/mm helper. The rears are 8" 70N/mm.

The rears currently are in direct contact with the rear subframe/spring mount at the top, as the ID does not fit over the center "post" (where the bolt is). It centers itself on the post, but doesn't sit down in the seat fully. I may go to 65 or 70mm ID springs so that they can sit properly in the base of the spring perch (need to measure). I'm keeping a very close eye on it, and there is no damage being caused, but I still don't like it and want to do the 70mm springs to make it right. I haven't made any movement on this yet though. One of thing I would need to confirm is if the lower spring perch adjuster can handle the 70mm spring, or if I will have to make an adapter to mate the 70mm spring to the 60mm perch (I suspect I will).

TonyC said:

oof. i'm jealous. there's no way i'd be able to throw away brand new tires for a set of $640 Michelins. I'm on the stock 17"s 205/50s, and they're pretty cushy.

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Well, it's not like I left them out for the garbageman, lol. I have them in my garage, I was trying to determine if I would be better served by selling them on CL for a couple hundred $, or keeping them around for when I likely sell the car in a few years. I was swayed to keep them when someone pointed out that I could throw them on if we take any long road trips, and thus save several thousand miles of wear on my "nice tires". So I'm keeping them around for that.

sac02 said:

em out for the garbageman, lol. I have them in my garage, I was trying to determine if I would be better served by selling them on CL for a couple hundred $, or keeping them around for when I likely sell the car in a few years. I was swayed to keep them when someone pointed out that I could throw them on if we take any long road trips, and thus save several thousand miles of wear on my "nice tires". So I'm keeping them around for that.

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i was thinking of doing the same, but am really waiting for a deal on 17x8 used rpf1/ssr type c/gram light 57c's. still, i'm just mostly jealous...

TonyC said:

am really waiting for a deal on 17x8 used rpf1/ssr type c/gram light 57c's. still, i'm just mostly jealous...

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Go look on the other "Mazda 3 forums" in the for sale section. There is a set of RFP1 and some Ray's for sale now.

thanks mate!

too bad the rfp1 are GOLD (i mean, REALLY? (freak) ), else I'd go pick it up this weekend.

Suspension looks great

Bringing this thread to the top.

I was trying to get some used OEM tires for a second set for winter. However, the prices around here are not that cheap for used OEMs, so I may as well spend a little bit more and get a brand new set of aftermarket rims.

The Kosei K4R came to my attention because it is the lightest available at the Tire Rack.com (in size 16"). I saw your post about the 17" set that you got, and would like to ask you if you noticed any difference in gas consumption, braking, and accelerating.

I would buy them in 17" size. That way I would have two sets of rims in 17, and could use the tires in any of them.

EDIT: I just saw this post about the Kosei K4R in 16" and now I am wondering if that is the way to go (from 17 to 16)... but then I would have to buy Kosei rims in 16 + summer tires in 16 + winter tires in 17" for the OEM rims.... and then sell my stock Toyo tires in craigslist, for peanuts. Way too expensive.
http://www.mazdas247.com/forum/show...-downsizing-to-16-quot-alloys&highlight=kosei

How much adjustment is possible on these? Say you wanted less than 1" of drop, like 0.5"-0.9" Do you know if that's possible with these coilovers (or any others?)

How are you finding the ground clearance now? Any trouble pulling into driveways or parking lots? How well does the new suspension control "bounce" and float? i.e. when you're on the highway and hit an undulating part of the road, the stock suspension seems to travel/bounce a little more than I'd like. Does this tighten that up nicely?

Thanks for your input. I'm looking to do something VERY similar with my 5 and mine is identical to yours, just a 2014. Same color, manual sport and you got the exact wheels I want too!

where did you buy the coilovers from?

ROBOTO said:

The Kosei K4R came to my attention because it is the lightest available at the Tire Rack.com (in size 16"). I saw your post about the 17" set that you got, and would like to ask you if you noticed any difference in gas consumption, braking, and accelerating.

EDIT: I just saw this post about the Kosei K4R in 16" and now I am wondering if that is the way to go (from 17 to 16)... but then I would have to buy Kosei rims in 16 + summer tires in 16 + winter tires in 17" for the OEM rims.... and then sell my stock Toyo tires in craigslist, for peanuts. Way too expensive.
http://www.mazdas247.com/forum/show...-downsizing-to-16-quot-alloys&highlight=kosei

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Stick with the 17" Kosei and get some quality tires. EVERYTHING was better with the Kosei + MPSS tires. The lighter wheels and better tires ride better, are quieter, grip better, everything. I was worried that going from 16" all season tires (stock Toyos) to 17" performance tires would mean a decrease in ride comfort (that's the traditional thinking) but that was not the case, things got better - the stock Toyos really are that bad.

socialcarpet said:

How much adjustment is possible on these? Say you wanted less than 1" of drop, like 0.5"-0.9" Do you know if that's possible with these coilovers (or any others?)

How are you finding the ground clearance now? Any trouble pulling into driveways or parking lots? How well does the new suspension control "bounce" and float? i.e. when you're on the highway and hit an undulating part of the road, the stock suspension seems to travel/bounce a little more than I'd like. Does this tighten that up nicely?

Click to expand...

There is a good amount of adjustment available, you could easily set them at stock ride height if you wanted. They aren't designed to go stupid "for looks only" low. I only lowered mine mildly, 1.2" front and 1" rear. I'm actually close to the the maximum "low" setting of the rear adjuster, if you wanted to go much lower than the 1" I have, you would need to swap the 8" spring for a 7" or even 6" spring (only like $50)

McStrut suspensions don't generally like being lowered significantly and will perform poorly despite the "lower CG" that people seem to think is the only aspect of suspension design. (talking suspension geometry, such as roll center - I'm an engineer/vehicle dynamics nerd/auto-x'er).

Ground clearance is no issue at this ride height, no issues with driveways or parking lots. I can't jump curbs, but then, I couldn't do that before the mild lowering either.

The ride is excellent, damping is perfect. It is tight, but not bouncy at all. Impacts are absorbed, rebounded once, and finished. It really is very nice, and not abusive at all. I used to be a bit "extreme" in suspension choices for my DD's (I DD'd a nationally competitive auto-x car, that was abusive) but I can confidently say that this is a suspension that while maybe a bit firm, is still acceptable to my wife on a daily basis, while still satisfying my needs for DD fun and occasional auto-x use. (If this was a regular auto-x machine, I would have a LOT more rear roll stiffness though).

scsi said:

where did you buy the coilovers from?

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Direct from AST

So how much did you pay for the Ast coilovers?

About $1800. Like I said (somewhere, maybe not this thread), I got lucky.

Ok thanks I got ahold of Ast and they said $2500 shipped

Hi Sac. Do you have more detailed pics of the AST COs? I would like to see any/all pics you have. I'd like to compare (visually if its the only option) them to the BC and YS. Did you happen to take measurements of any of the components? I am in the process of debating a longer yet softer springs OR a dual spring like the AST for the front. Thanks.

Nice review on your upgrades sac02. I recently went from the stock 17's to rpf1's similar to the Kosei's. I now believe in unsprung weight making a nice difference. It wasn't a crazy, but acceleration, braking, ride all seem a tad better. Made me feel my car handles a little nicer all around. I think the light wheels makes a difference in a car thats low on hp like the 5. Maybe in a real sports car with gobs of power and grip already out of the box you wouldn't notice as much.