RALLYING

For rallying, the ALR TPX/TTX range is also used. It’s testament to the effectiveness and the adjustability of this range that it’s suitable for the different demands of both rallycross and rallying.

“In rallying, it’s mainly long-term endurance you are after,” says Jarlmark Nafver. “In rallycross, it’s about being able to hit other cars and not lose the wheels as well as surviving the peak loads of the high jumps and the hard landings.

“In rallying, the peak loads are fairly similar from a ground contact perspective, but obviously not from contact with other cars. In rallying you also know more about what the surface will be like on a stage compared to the constant surface changes in a short time in rallycross.”

While Ohlins is not currently at the top level of WRC, a quirk of the manufacturers currently competing, its dampers are on the Peugeot 208 R5 car currently competing in WRC2. In that car, Jose Suarez managed to set a top six time overall on the Monte Carlo Rally, albeit in drying conditions that favoured his later road position.

“The peak loads, say on a jump in Finland, would be up around 40-50kn,” says Jarlmark Nafver. “But it’s when drivers make mistakes that you get the real peak loads if they put the tyre on the inside of a corner and there’s a 20cm rock in there – that’s when we see similar loads to rallycross. That’s a test of the bending resistance and the tensile strengths. We try to design the damper so that it’s still on the car and it’s the rim that brakes.”

With endurance also comes a temperature challenge. On a hot rally such as the Acropolis in Greece, the dampers can face heat up to 120-150C.

Inevitably, at this level the dampers require service after every event, but there are Ohlins products lower down the range without so many special features that don’t require such frequent attention.

The top-end TPX damper also has some advantages over a regular damper designed to make its performance more consistent.

“The TPX is a twin-piston system, compared to our TTX, which is twintube damper with two valves in the cylinder head,” says Jarlmark Nafver. “So what we’ve essentially done is instead of having both valves in the cylinder head, we put them on the piston rods, so it’s actually two pistons instead of one.

“The working principle for TPX is exactly the same as the TTX. You are only building pressure upwards rather than downwards so the lowest pressure in the damper will always be the gas pressure. This changes the handling of the damper because if you have a regular damper where you have a single piston, you can change the behaviour by changing the gas pressure.

“In such a damper, you have a positive build-up on the side that’s resisting, then a negative on the back side of the valves, so you need a very high gas pressure. On our damper, you don’t have that.”

Interestingly, the damper is so sensitive that if you run them in a static dyno, you don’t see much response on the graph based on adjustments. But the dynamic change in the real world is far bigger and can be felt with the drivers. This is why Ohlins puts a lot of effort into the response time of the damper by minimising the hysteresis – the lag between the input and the required reactive output.