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Discussion Starter #121
Another interesting car using Tractive adaptive dampers, the Italian ATS Corsa. £100grand and 600bhp. Good looking bit of kit IMHO.
 

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Discussion Starter #122
Dropped the Alfa off at Raceshocks.UK earlier for the dampers to be revalved softer on bump and harder on rebound.
Simon gave me a lift home in his recently acquired late model Porsche 911 with PASM factory fitted adaptive dampers. He’s ordered a Tractive control box to replace the Porsche unit though will initially retain the Porsche dampers. The new control unit will provide faster damper response than standard, the potential for a more resilient ride, and the ability to be mapped via a laptop. The standard Porsche dashboard switch will be used to select either of two settings. Simon plans to remap it himself to suit the UK’s roads, and use the car to demonstrate the Tractive setup to potential customers by demonstrating how the ride quality can be instantly changed. Will be interesting to compare it with the 4C.
 

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Discussion Starter #124
Have you chosen spring rates yet? I’m running 50Nmm front and 40 rear. Handling is very nice, and ’playful’ on the limit. I’m not running anti roll bars (including the front), partially to focus on getting the springs right but mainly because the front A/R bar corrupts the steering and magnifies bump steer. Now, it’s very different to the standard setup which was uncompromising on the limit, and which I’d describe as a white knuckle ride. Regarding springs, the new shim stacks are being installed and the rear springs may be softened depending on the results - but don’t forget I’m probably looking for a more resilient road drive than you might be looking for. If you’re a track bunny, I think the dampers have the capability to control even harder springs if that’s the way you want to go.

i have Alfa Works rear lower suspension arms fitted (and front suspension arm spacers) with a spherical bearing and would concur with others that this increases stability when pressing on. They work very well with the Tractive dampers and RaceShocks.UK setup and I thoroughly recommend them. I’d like to add that Jamie is also a very helpful bloke to deal with, and very knowledgable and enthusiastic about our beloved cars.
 

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Discussion Starter #128
What does this cost in parts, then hours to fit in final product form?
I suggest the best thing would be to speak with Simon at Raceshocks.UK. You could buy the dampers and springs as supply only, as Alipapa has done, for UK customers Simon could supply and fit them at his workshop in South Wales, or he can work with your requirements and tailor them to your needs - either develop and supply or a comprehensive supply, development and fit service.

contact details here

His buyers guide which includes prices for Caterham 7 suspension - is well worth a read

Without making this into a commercial, now that he has experience with 4C I should imagine that Simon could customise the curves of Nitron dampers to suit you too, if you didn’t want the expense of going adaptive, though you’ll need to discuss that directly with Simon.

Nitron option
 

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Discussion Starter #129
After fitting this kit a squeaking/knocking noise developed from the front suspension, the cause being identified by Tractive Suspension and RaceShock.UK as being due to the wide clearance fit between the OEM mount and fixing bolt. The hole in the mount is 14mm dia and the shank on the bolt is 12.4mm meaning 1.6mm clearance hence allowing movement, and being the cause of the noise. Tractive will get some top hat washers turned with a step of 14mm OD / 12mm ID to be supplied with the kit complete with new 12mm dia fixing bolts. They’ll be a straight swap for the OEM washers and bolts so customers won’t need to perform machining or welding.
 

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Discussion Starter #131
I recall another brand of after market coil overs mentioned knocking noise. I wonder if that was the same issue?
Yes, I’ve been wondering that too. Nitron’s also use spherical bearings but utilise aluminium spacers whereas Tractive uses stainless steel. It might be that the softer material ‘beds’ into the larger diameter mounting holes because Nitron users here don’t report any unwanted noises.
 

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Discussion Starter #132
When Tractive introduces AI in the damper ecu the car should be capable of this

I hope it’s a user installed upgrade 😄
 

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Discussion Starter #135 (Edited)
A quick update as development of my setup is continuing. Spring rates are 50N/mm front and 45 rear. Both rates are firm on a lightweight car used predominantly on the road, and may sound an odd combination to you when comparing with other damper suppliers’ figures.

The front is relatively stiff which allows for a pointy front end when the Tractives are set to hard (4 or 5) but also a compliant ride on setting 1 (soft). With the fronts set to 1 or 2 the damping ability on less than perfect roads is phenomenal, and a world away from the standard car. It tracks with much less tramlining and the car can be placed more accurately because it’s more relaxing to drive without the need to constantly fight it down the road. A careful eye needs to be kept on the speedometer as it is possible to travel more quickly with less effort/fear compared with the OEM setup. With the new damper curves (which I assume Alipapa will receive) setting 1 is now less than critically damped and provides a good ride, as good, I feel, as an Alpine A110. Settings 2 or 3 work as a fast road setup depending on the surface, and 4 and 5 will provide stiffness and a pointy front end when on a circuit. The inherent bump steer designed in to the car still exists because changing the dampers alone cannot eradicate it, but the softer front setup lessens the effect substantially.

The rear is a work in progress. 45N/mm springs are hard on a lightweight, mainly road car (approx 250lbs/ins), but even with the rear dampers set to their softest the back end is still hard, and adjusting the controller has little effect on them. They’re good on track but offer much less of the front end compliance on road. Simon at Raceshocks.uk put them on his damper dyno when completing the recent retune and he reports they adjust as expected which suggests the issue is elsewhere. Starting at the easiest end, the Touch screen controller firmware will be checked next week to ensure that it’s sending the correct messages to the accelerometer and then on to the dampers. If necessary, softer spring rates will be required all round to meet my requirement for suspension compliance on road.

Returning briefly to the start of this post, and taking into account the suspension motion ratios, suspension unit angles, and corner masses, the calculated starting point for the rear spring wheel rates is 60-70% firmer than the fronts, meaning the 45N/mm rear springs should match my 50N fronts perfectly (similarly with Alipapa’s slightly firmer 55F/50R setup). I havent tried them on 4C but would think that the even firmer rear springs often favoured by other manufacturers’ setups would negatively effect traction and increase the potential for oversteer.
 

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Sounds strange to me, that you go for lesser spring rate at the rear where the most of the weight is placed.
I have the Ohlins with 75 at the rear and the car is very nice to drive on any kind of road.
We will see if these spring rates will be the final setup, I have some doubt in case you want more than just cruising around.
 

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Discussion Starter #137 (Edited)
Sounds strange to me, that you go for lesser spring rate at the rear where the most of the weight is placed.
I have the Ohlins with 75 at the rear and the car is very nice to drive on any kind of road.
I think that you’re confusing natural spring rate with the much more important wheel spring rate. As described above, my rear wheel spring rate is 60% harder than the front.

To visualise this, think about the mass of the car and the front/rear balance, then take into account the natural spring rate required together with the suspension design (double wishbone front and strut rear) that will provide the motion ratio and ACF. IIRC, if you have 75N/mm rear Öhlins then you’ll have the earlier non-track specific setup with 57N at the front meaning your rear spring wheel rate is almost 3 times (2.67) harder than the front. You don’t often see that on a fine handling car. From their parts catalogue, it appears that Öhlins originally used the same spring rates for 4C that they used for the Lotus Elise (which is double wishbone all round - and therefore would also have wheel rates approximately 1.5 or so harder at the rear than the front. The Lotus MR and ACF is slightly different front to rear so 1.5 is my best guess). For 4C Öhlins has changed that setup more recently and now provide softer progressive rate front and dual rear spring (using helpers). I don’t know the rear rates.

We will see if these spring rates will be the final setup
I think my spring rates are about right for a car mostly used on track but also on the road. The Tractive dampers aren’t like the conventional dampers that you’re used to. They’re more like a cross between witchcraft, magic, and jumping off the wardrobe onto a beautifully damped memory foam mattress. My requirements are for a car that flows with the surface with great feel and maximum traction and I’m looking for the handling of a WRC car constrained by having less suspension travel.
Depending on how the latest work progresses on the rear I may adopt softer springs all round.

I have some doubt in case you want more than just cruising around.
Hahaha, that made me chuckle. I hope you don’t mean me!
 

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You are right: on the front we have double wishbone and the shock is angled. Probably you calculated the force relative to the angle of the shock but I don't know if you took in consideration the connection points relative to the wheel hub (tire itself).
On the rear we have the mcphearson design with the shock less angle (more vertical) but also it is positioned not so close to the wheel hub.
I also don't know if you took in consideration the antiroll bars --> the front one has much shorter arms so it's stiffer by design.

Also, extremely important: engine position and center of gravity. You probably considered only the center of gravity of the car BUT the engine is on the rear and the center of gravity is composed out of 2 forces: the one over the rear wheels and over the front wheels:
We may look at the car in 3 sections:
1) The front end that has the radiators and some aluminium structure --> It is very light (probably less than 150 Kg) and the COG is extremely low
2) The middle: CF TUB + seats + doors and windows + driver = Maybe around 200 Kg (and the center of gravity is a bit higher because of the driver
3) The rear - structure + engine + gearbox + ... = Maybe around 700 Kg + center of gravity quite high.

Now imagine that the rear suspension is actually working to stabilize ~ 700 Kg + a part of the middle section of the car and the front suspension is stabilizing 150 kg + a part of the middle of the car.
 

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Discussion Starter #139
It seems that you haven’t read my posts as you appear to have duplicated bits of them. Of course MRs have been included!
Corner weighting the car deals with what you state as being two vertical forces - there aren’t two forces (or three as you state later) - it’s one acting on the four corners and is dependent largely on the distribution of mass.
Some time ago I disconnected the front anti roll bar as it’s effect corrupts the steering and exacerbates the bump steer (a well known effect on lightweight mid-engined racing cars) and have left it disconnected whilst the spring rates are being finalised - A/R bars are more important to personal feel and tuning in any case.
It’s not helping and more confusing for you to think of the car as three discrete masses/loads/forces, though you could include thoughts of the transmission due to its effect particularly on horizontal load when cornering, (though from the perspective of ‘feel’ and therefore handling, this tends to be transient) which could be alleviated by the use of rear rose joints and perhaps wider wheels and tyres, together with stiffer dampening (providing wheel spring rate isn’t soft and allowing wallowing). I have assumed that your suspension geometry has been adjusted appropriately so have left it from this discussion due to the potential introduction of more variables.
Your suggested distribution masses are out too: a Euro 4C has a wet mass of approximately 1 tonne with an 80kg driver, and is distributed approximately 40%/60% front/rear.
 

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Your suggested distribution masses are out too: a Euro 4C has a wet mass of approximately 1 tonne with an 80kg driver, and is distributed approximately 40%/60% front/rear.
Why do you say is wrong? Because you assume that the rear section should weight 60% of the total weight? It doesn't work this way
 
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