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Discussion Starter · #922 ·

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Discussion Starter · #924 · (Edited)
So guys, another track report.

Right as I was getting frustrated with the GMS ARB development (so many revisions) and not being able to set new PR, although the car felt faster, we did it. Not by much as driving was not the best, the track was crowded so could be that the lap wasn't 100% clean and the temps were very high, but there it is. New PR. The car just handled perfectly and I rarely say that.

Past Sunday we spent blasting our home track Grobnik. I did some fine tuning to the design and specs of the GMS adjustable ARB's and yes, this is finally it. The car is beautifully planted. On the roads it provides slight understeer, but on the race track it's beautifully balanced. Neutral. Thanks to stiffer ARB's and consequentially less body roll, there is much less need for aggressive camber and the car feels feels solidly planted in the corners. It is confidence inspiring. I love it. This is what I was looking for. It was so hard to find the exact balance between understeer and oversteer which was achieved by selecting proper material in terms of wall thickness and diameter and I'm glad I didn't give up and did so many revisions.

With this last addition to our upgrade in terms of handling, I'm able to say now that we have added that last missing piece to the puzzle, the ARB's. The rear control arms provide super precise handling and feedback, the front control arms sharpen the front end steering feel and help with dynamic negative camber gain on racetrack, so we can run slightly less static negative camber, optimizing our braking, yet allowing us a good push through the corners. With the spring rates we are as stiff as we want to go (65N/mm front and 80 N/mm rear) for also a street driven car, so the GMS adjustable ARB's were a must. One thing that I might add is limited slip differential, other than that, car handles perfectly and it feels, as mentioned, really confidence inspiring to push, to drive on the limit.

Max peak lateral acceleration: 2.2 G
Max deceleration: 1.23G

So, after a really long time, some onboard footage for you fellas:

 

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Great news, Rudi!

One question - any concern that these are optimized for your particular setup (whatever shocks you are using, ride height, etc.). You note a spring rate adjustment, for instance.

So can you comment on how these might react with different setups. Or at least “minimum” and “recommended” system requirements. ;)
 

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Discussion Starter · #926 · (Edited)
We designed the GMS adjustable swaybars to improve OEM part (stiffer, lighter, adjustable), not to drastically change the understeer / oversteer balance. The adjustable ARB's will stiffen up the car through the corners compared to the OEM ARB's, but won't make a drastic balance change. However, by having these adjustable you can then move the balance slight towards oversteer or understeer, depending of your needs and preferences. Long story short, no particular setup needed. They work with OEM suspension and aftermarket suspension.

My current setup:
215/265 tires
Nitron NTR R3 with 65N/mm(front) and 80 N/mm (rear) spring rates
GMS adjustable ARB (soft front, stiff rear)
GMS carbon rear hood (slightly increased rear downforce) + GMS carbon rear louver (reduced lift)
940kg kerb weight (we need to lighten the rear end for 10-20kg's as we are slightly too heavy at the rear, compared to the front)

I'd call this a perfect endurance setup (neutral balance). You can drive the car on the limit with quite a confidence. In future I'lll go from 265 rear to 245 (due to class regulations), so I expect slightly increased oversteer characteristics due to this change. If I would be staying with this setup, I'd probably slightly increase rear spring stiffness to compensate for added downforce at the rear and the fact that rear end is not as lightened as the front is. That would then again, move the balance to slight oversteer, which in theory yields the fastest pace at increased tire wear penalty but not very forgiving setup. This would be hot lap setup (neutral balance with slight oversteer).
 

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Discussion Starter · #931 ·
We are discussing dealership conditions for LSD (limited slip differential) for 4C. We are focused on two potential business partners we want to cooperate with to offer this engineering art to you customers.

These two are:

1. Drexler (top end clutch-pack type LSD, very predictable to drive, fully customizable ramp angles - lock on acceleration / deceleration, preload - aggressiveness, friction - lock percentage). Best performance you can buy at noticeable price penalty and rebuild services required (depends of driving and driving regime). Pulling lap after lap on the race track could potentially wear the LSD in a year or so of serious tracking, but probably if that's the case, you'll be looking in to clutch rebuild anyway, so it's not all that bad anyway. Rebuilding LSD while you engine is out is a few hour job (replacing clutches inside the LSD).

2. Wavetrac (top end Torsen type LSD, slightly more tricky to drive due to various locking percentage, non customizable). Solid performance at an affordable price and no rebuild needed. In scenarios when a single wheel is lifted and then the car suddenly lands on the ground (over crest, curb), the instant lock of the LSD, can easily brake either LSD helical gears or the gearbox, so it's not commonly used in racing.

Now, my thoughts on this are. Not many customers will be looking into the LSD for 4C, but if you ever driven 4C hard in tight turns, you probably noticed inner wheel spin, regardless of the Alfa Romeo's Q (electronic limited slip), that should be braking one wheel, transferring power to the other. Now if you experienced the inner wheel spin multiple times on your 4C, then we probably agree that the Alfa's electronic LSD doesn't work good enough for serious tracking. And if that bothers you, you'll be looking into the LSD right? So if you are looking into the LSD, you are probably serious tracker and only the best will do right? From this point, the Drexler, clutch pack type LSD is the thing to go, right? You wouldn't be making compromise on this would you? I think I already answered myself a question.

Let me know you thoughts dear fellas...

Cylinder Gas Font Machine Technology
 

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Yes, I think you already gave yourself the answer.
And looking back at previous times you asked ‘the people’, we always ended up with the best, didn’t we 😉.

Though truth be told, me personally, I would love a good but budget conscious option, as my well is not endless…
 

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Discussion Starter · #933 ·
Tomorrow I'll attend the hillclimb event with 4C and there are a few nasty tight corners that make the 4C beg for LSD. I think this will speed up my decision, so I can decide by Monday which way will go.

Though truth be told, me personally, I would love a good but budget conscious option, as my well is not endless…
We all would, but in 99% there is a reason for one option being cheaper than the other. In the world of motorsport if you go budget way at first, you usually end doing both options in the end. That's how was with all the parts I ever bought for previous cars I had (wheels, suspension, brakes,...). Since owning a 4C I rather don't buy parts than look for shortcuts if i can't afford them. That's why I don't have the LSD mounted yet. But with having the clutch out, it seems like a reasonable time to do it.
 

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We all would, but in 99% there is a reason for one option being cheaper than the other. In the world of motorsport if you go budget way at first, you usually end doing both options in the end. That's how was with all the parts I ever bought for previous cars I had (wheels, suspension, brakes,...). Since owning a 4C I rather don't buy parts than look for shortcuts if i can't afford them. That's why I don't have the LSD mounted yet. But with having the clutch out, it seems like a reasonable time to do it.
Yup, my experience as well.
But I keep on doing this to myself anyway! :ROFLMAO:
 

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Tomorrow I'll attend the hillclimb event with 4C and there are a few nasty tight corners that make the 4C beg for LSD. I think this will speed up my decision, so I can decide by Monday which way will go.



We all would, but in 99% there is a reason for one option being cheaper than the other. In the world of motorsport if you go budget way at first, you usually end doing both options in the end. That's how was with all the parts I ever bought for previous cars I had (wheels, suspension, brakes,...). Since owning a 4C I rather don't buy parts than look for shortcuts if i can't afford them. That's why I don't have the LSD mounted yet. But with having the clutch out, it seems like a reasonable time to do it.
Go GMC...
 

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Discussion Starter · #937 · (Edited)
Onboard POV of GMS prepared Alfa Romeo 4C on a Hrusica - Hill climb event organized by Heartuned. Sub-optimal car setup, with room for improvement, but we take responsibility (too many heat cycles on tires, lack of LSD). Still it ended as a solid drive which secured us 1. st place 200 - 321 HP class and 3rd overall, although it didn't feel the best. Best time 1:38.390. We look forward for next event.

 

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Discussion Starter · #939 ·
What about our man GMS? 😉 😁
I was thinking about that too, at some point, but honestly, I don't think we can reinvent the wheel here, so we'll just let the dedicated fabricators do their job.

Anyway, regarding the LSD dilemma clutch type vs. torsen type, I came to a conclusion that it would be best to offer both - top end, Drexler clutch type LSD for those who will be building the track cars and more "civil" version, the torsen type Wavetrac. I believe this is the only way to actually offer all a 4C owner might ever need. We simply cannot prefer one LSD over the other as both have pros and cons and shall be chosen according to the needs. Both items will be available in GMS online store soon, as we are already working on dealership terms and conditions with both companies. I will keep you updated.
 
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