SuperPro Overhauls an ageing SEAT Leon FR at Demon Tweeks

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While it may not be as immediately sexy as say, a set of wheels, or a new exhaust, sorting the suspension on your car really could be the best (and smartest) money you’ll ever spend. We joined SuperPro at legendary tuning house Demon Tweeks to prove just that!

When it comes to making your car steer, handle and stop better than it ever did even when new, it’s hard to argue against countenancing the advice of an industry specialist. While there are countless articles and blogs out there offering great advice (including this one!) there’s nothing like sitting down with a grizzled veteran of the art and outlining your problems or areas for improvement. These consultations won’t just give you the benefit of their many years of experience, but will also help you shortcut to the best results – working alongside someone who’s tackled those very same problems many times before.

If you love your car, but dislike certain of its handling or dynamic traits, where do you start this process? Well, it’s a journey of steps, and the first of which is to accept the fact that what’s good enough for your local MoT man, may not be good enough for your local chassis and suspension specialist. Let’s take suspension bushes as a great example. As long as it’s there, not overtly deteriorated and keeping metal from metal, you’re probably going to get a pass. When you then think that that bush may be 10 or 20 years old, stiffer and harder than it should be, and therefore unable to deliver its required range of dynamic abilities, and you can start to see where the problem lies. Extrapolate that across every bush on the whole car – and you can start to see how even a clean sheet ‘pass’ is no guarantee of driving enjoyment.

The first question to ask yourself is ‘what do I want to use this car for?’ If your daily commute includes potholed roads and rough lanes, you’re probably not looking for a ground-hovering washboard set-up. Conversely, if you’re a trackday regular and ‘B’ road hero, you’re going to need a genuine balance of handing, compliance and comfort – mixed with a precision that allows you to really dial in the car’s tyre contact patch.

SuperPro dealers know that no two cars – or drivers – are the same, and that no two sets of driving requirements are ever identical. By consulting at length with drivers and owners, they build a comprehensive picture of what’s needed and how the car will be used. Once they have that, they can advise as to how to spec the suspension to make the car really fulfil its brief.

As a case study, we joined the team at Demon Tweeks in Wrexham as they set about the 2006 Seat Leon TDI of Sales Manager, David Salisbury. As one of the UK’s leading tuning houses and automotive mail order outlets, Demon Tweek’s experienced workshop team has perfected the handling and poise of literally thousands of cars, and having tried practically every brand and solution on almost every type of car, had more than a few neat tricks up their sleeves.

The Leon, with 115,000 miles under its belt was proving to be somewhat of a dynamic disappointment for owner, David. Straight-line speed was sorted thanks to a recent remap endowing it with some 210bhp, but cornering prowess was sadly lacking. Seeking comfort and handling, and wanting a precision in steering that had left the party long ago, David had turned to his learned colleagues to find the answer.

Experience really is key here. Technician Darren and Demon Tweek’s philosophy clearly match SuperPro’s. With a well-stocked storeroom behind him and a pristine workshop Hunter alignment machine to rely on for millimetric accuracy, it was clear that all the components that were to be fitted would be aligned to perfection. And that really is the key to a great suspension set-up. Many great kit parts have been let down inexperienced technicians – or inadequate kit.

David’s wish was to lower the Seat in order to improve both stance and handling. Before that could happen however, Darren carried out a full diagnostic on the Hunter aligner. While the whole set-up was found to be well within tolerance, you have to remember that tolerances are a very generous thing in alignment terms – with most factory settings allowing a mixture of toe in and out – and negative and positive camber ON THE SAME AXLE!

As well as full geometry measurement, ride height, tread depth and tyre pressures were also all checked – as each can have a marked effect on ride height. Once these were set and noted, ride height itself was measured from the hub centre to the wing edge. This is the only truly reliable method to remove variables from the mix. It’s also an essential part of the process, too. Here, Darren noted that the near-side rear was sitting 10mm lower than it should, with the offside showing some 15mm. Clearly all was not well beneath, warranting further investigation.

Tyre wear and condition were both spot on and front suspension parts were ticking all of the boxes. After poring over every component in turn, Darren discovered that there was actually a broken spring at the rear, with the condition of the bushes looking decidedly past their best – despite the car having a clean bill of MoT health! When you think about it, rubber naturally deteriorates over time. With constant exposure to UV light, oil, salt and petrochemicals, it’s bound to become less effective, losing elasticity and resistance, its two key functions.

A bush’s key function is to join and separate metal, to insulate and control while facilitating movement. As the material hardens it can no longer do this. Add in the fact that rubber bushes ‘set’ in a position over time and you’ll start to feel a huge difference in geometry changes, steering feel and compliance. They become sloppy where you want stiff – hard where you want comfort. Neither trait is desirable – and in their most extreme forms, it can be extremely dangerous as the tyre struggles to maintain its contact patch. It’s strange isn’t it? Tyres are advised to be changed after 7 years, but bushes aren’t, despite being made of the same material...

On David’s car the front bushes were also in a terrible state, with cracks and splits rendering them less than effective. These would also need replacing forthwith. At some point, as previous owner had also taken the opportunity to replace the front bushes on this car with one from the higher spec Cupra model to provide better front end precision. The factory bushes allow way too much movement as they’re heavily voided. Featuring less voiding, and using a harder material, the Cupra bushes address some of these problems.

Consulting back with David, the team advised that he upgraded to SuperPro polyurethane. Although new rubber parts would have wound back the clock, dynamically, they would have started to degrade from the moment that they were fitted. SuperPro bushes have a ‘memory’ of their cast shape, allowing them to spring back to their original form, as well as being impervious to the factors that can rapidly degrade their rubber equivalents.

Another factor in the reasons behind the change to SuperPro is that it has a unique polyurethane (PU) composition that helps it retain its properties for life. Not all PU bushes can do this. It also has different properties to rubber, being not quite as compliant in certain planes. This is no problem once it’s engineered properly. As PU won’t twist like rubber can, it acts much better when it’s set up more like a bearing, allowing it to rotate around a central pivot. Being under less stress this way, it has more flexibility, allowing it to insulate NVH (Noise, Vibration and Harshness) from the car’s body, moving only as it needs to, transmitting minimal noise while maintaining maximum control.

SuperPro’s PU is also very progressive in its rate meaning that it’s compliant under low input forces but the more force you add, the greater the resistance becomes. Because of this unique characteristic, SuperPro varies the shore hardness of bushes on the car specifically for each location which allows them to exactly match the forces and loads across the car with the right product. This is how SuperPro products give you back control without ruining the ride.

The next component to consider fitting were SuperPro’s lightweight alloy arms. The PU bushes fitted in arms allow a free pivoting movement, increasing control of the rear mountings and keeping consistent toe under load. This prevents the arms from folding back under braking, keeping much more consistent toe geometry and steering feel. The rear bush is prefitted with an offset centre bush to increase caster by one degree. This offers better self centering and a much more positive steering feel. Having fitted many of these before, Darren already knew that the car would become much more communicative with this mod. And besides, it has 47% less mass than the OEM part, is prettier – and reduces unsprung mass. What’s not to like?

Darren also suggested a set of SuperPro’s adjustable ball joints. These add in a significant degree of camber adjustment, while a longer pin also allows roll centre correction. Allied to a full set of SuperPro bushes on the multi-link suspension on the rear, things were looking good.

The broken springs allowed the chance for an upgrade, so here a set of the much vaunted Eibach Pro-Kit springs were matched with Bilstein B4 dampers to give a true upgrade. A lower ride height, with progressive spring rate – and OEM quality damper will ensure that this Seat will now be punching far above its factory weight.

The final finishing touch came from the SuperPro anti-roll bars. (ARBs). A great way of reducing load transfer without increasing spring weight, the ARBs effectively reduce body roll without the need to increase spring stiffness. Clearly aimed at the UK market, these parts also benefit from 3-stage PU-based powder coating and are salt tank tested for 500 hours, making them good for many winters to come. To allow super fine tuning, there are two rate adjustment points on both the front and rear bars, which, when allied to SuperPro’s own fully adjustable heavy-duty links, can be used to precisely even out the preload on the bar, maintaining perfect adjustment. OEM wire drop links can twist and flex, absorbing forces. These uprated parts do not, ensuring all forces transmit into the bar making it work harder and more efficiently.

Throughout, Darren used best practise to make sure all was well. All bolts were pre-soaked in releasing fluid, and anything that looked stretched or excessively corroded was replaced with new parts. SuperPro’s press tool kit was used throughout to ensure each part was pressed out – or in- without any damage to either bush or surrounding component. Everything was deburred, cleaned, smoothed and painted where necessary, with all bolts and nuts precisely torqued bolts. A real pro tip here is to never to finally tighten the suspension at ‘full droop’ either, ensuring that each part sits where it should when the vehicle is under full load.

With everything carefully fitted and checked, it was back onto the wheel aligner for the final settings. The new lower ride height had increased camber – something Darren could easily cancel out with the new adjustable ball joints. Ride height was checked again, revealing itself to be perfectly level side to side once again, albeit a little lower than before, thanks to the ProKit springs. Although caster is pre-set on this car, the new constant geometry set-up will make it all much more positive. The new PU bushes ensure that the pick up points for each arm now stay in the precise same place making every corner and braking dive feel predictable and safe.

This left the final piece of the jigsaw; the roadtest! After Darren had signed it all off it was back to David for his verdict. ‘The difference is huge,’ he enthused! ‘The car has never felt this good since I’ve owned it. There’s a level of precision there that I’ve never experienced before, yet the car still feels comfortable and compliant. I was genuinely thinking of selling this car before today! I think I’ll keep it for a while yet. It’s such a hoot to drive!’

And there’s the theory in action. The importance of this whole process is knowing what it is that you want to achieve, measuring where the car is at the start, and carefully matching components and upgrades to achieve the perfect, homogenous whole. Don’t go fitting race suspension to a road car, and don’t forget the key components like bushes. They make a huge difference. It’s all about that constant geometry, making sure that the tyre is able to do its finest work. Choosing the right kit then is essential, but ensuring that you have the right specialist to advise you and fit it all, even more so. Choose wisely, and enjoy many years and miles of driving fun!

SuperPro has exceptional handling packages available for a wide range of vehicles and this article applies to all similar VAG vehicles based on the MK5/MK6 VW Golf platform (such as the Audi A3 8P, Skoda Octavia and VW Golf MKV/MKVI).

Demon Tweeks website