Yokohama dB brings silent motoring to quieter levels

By Lee Pang Seng

SILENT motoring has become a key factor in new car purchases, especially in the middle to premium class market. With carmakers producing vehicles that run quieter with more efficient engines and better body buffers to reduce transmission of noise into the passenger cabin, tyre makers are pressed into doing their part as well.

Yokohama took this challenge well back in the late 1990s (1998 to be exact) when it introduced the dB range. As dB stands for decibel, a measure of noise, the name was certainly perfect for this tyre. This range is still continued today although the focus has shifted to the Advan dB that was launched in 2011 to cater the premium class cars. This was the Advan dB V551.

Recently Yokohama brought out the Advan dB V552 as it sees a bigger market for silent tyres, namely from hybrids and electric vehicles, premium MPVs (multipurpose vehicles) and premium grade compacts. This also corresponded to the higher disposable income of the people who are potential owners of such vehicles.

This Japanese tyre maker, which celebrated its 100th anniversary recently, believes it has the benchmarks to work on having developed silent running tyres for 20 years. Given the success of its earlier dB range, the only way to go was up and with the new Advan dB V552, Yokohama feels that it has developed the ‘most silent tyre ever’.

The Advan range is seen as the more premium series in Yokohama’s selection of tyres and having a silent tyre in this model portfolio was a logical move. Premium car customers are the ones who would be more demanding of a complementary tyre to match the quieter running of the cars.

Other than air turbulence (the noise of which has been progressively curtailed with ever more aerodynamically refined car and vehicle bodies), the second noise generator was the frequency produced by the tyre treads as they rolled over the road surface. Reducing this frequency, or road noise, is one of the key areas that tyre makers factor in during the development of a new tyre. This margin of noise level would probably vary according to tyre models and the more premium it is, the quieter it would be.

For the Advan dB range, the V552 is said to be 30 per cent quieter (noise energy reduction rate or road noise) than the V551 and that is a big improvement. The pattern noise is also reduced by 20 per cent. At the same time, its safety performance is improved with six per cent better wet braking (from 100km/h to a complete stop) and rolling resistance is reduced by five per cent (this contributes to better fuel economy). While it matches the V551 in dry braking and ride comfort, the V552 is said to excel in wet handling (eight per cent improvement in wet stability).

To achieve a more silent performance, the Advan dB comes with a new pattern design featuring ‘beautiful’ small blocks, new structure with high quality parts and a new tyre profile. With smaller tread blocks, Yokohama says the sound of hitting the road surface is reduced. For better wet grip and fuel efficiency, a new dB compound is used as well as in adopting a fuel-efficient compound for the tyre side walls.

On the inner side of the tyre, the side that you don’t see when it is fitted to a car, has what Yokohama calls precise groove arrangement. What looks like a single connected area is actually narrower grooves to shift the timing of grounding, the point at which it comes into contact with the road. By doing so, the noise generated is dispersed. According to Yokohama, this prevents you from concentrating on a specific frequency band and harsh noise is therefore reduced.

The block of tread grooves next to it features twist edge chamfering. This is to control block rigidity; the technique applied here is to chamfer the edge part of the block into a twisted shape akin to cutting the edge part of the block. And whichever side of the tyre this block of treads is applied to, it helps in suppressing uneven wear.

The centre straight rib block is a common design on tyres as it provides stability in a straight line and aids handling. The tread blocks on each side of it come with single edge chamfering or what is called ‘partially applying precise chamfering’. Yokohama says this controls the occurrence of uneven wear and suppresses the deterioration of quietness.

We are now on the side of the tyre that you can see when it is fitted to a car. Here, there is the staggered arrangement of the grooves and sipes. This pattern optimises the rigidity of the tread block by placing non-penetrating grooves and sipes at precise intervals from the left and right. The result is improved steering stability, in particular through corners, and more silent performances.

The tread area is moulded from a new ‘special’ dB compound that is said to control fuel efficiency and wet performance at a high level. Beneath the tread area, Yokohama has a new silent base compound that optimises the gauge for each tyre size. This is found to improve quietness by suppressing vibrations.

This is supported by a single belt structure with wide belt and belt edge cover. This sees the use of a wider belt than that for a general tyre while Yokohama says the belt edge cover enhances the rigidity at the end of the belt. This helps to control vibration on the tyre shoulder for a more comfortable ride.

For the sidewalls, there is a fuel efficient side compound that suppresses heat generation and contributes to better fuel mileage. In addition, there is the side reinforcement belt that Yokohama says provides firm handling and ride comfort for heavy weight premium cars like the Mercedes-Benz S-Class and BMW 7 Series.

The new Advan dB V552 is made in Japan and is available in 45 sizes at the time of its launch (from 14-inch to 20-inch, and aspect ratios from 35 to 65). The biggest size is 245/40 R20 and the smallest is the 155/65 R14. However, the Advan dB 551 is still being produced for now to cater to sizes that are not available with the new tyre model range.

Yokohama Advan dB Thailand Experience

The proof of the pudding is of course in the eating and we did that, along with invited media from the Asean region, at Yokohama’s Tire Test Centre of Asia near Rayong, Thailand. This test centre was opened in 2009 and was expanded last year with more facilities to make tyre development trials more complete. The huge 320-hectare centre is said to be the biggest one outside of Japan for Yokohama.

It has 41 kilometres of varying road surfaces, including a large oval circuit, and 100,000 square metres of multipurpose terrain to put the tyres to the fullest grind. Tyre makers are guarded when it comes to the road surfaces that their tyres are put to the test on and during our visit, we were told that no pictures must be taken of the respective road surfaces that we were to cover.

There were four routines with a fifth ‘fun drive’ excursion on a sport tyre to cap the day. The first was the sound test involving two Toyota Camry sedans, one fitted with the Advan dB V552 and the other with the older V551. We were chauffeur-driven so that we could focus on the sounds picked up by the tyres over the respective surfaces.

The first section was on pattern noise, that is noise generated by the tyre’s tread pattern on smooth surfaces, and the other was for road noise on road surfaces that were generally found in Asean countries. Our first stint was in V552 Camry, followed by the ride in the V551 Camry and reconfirming our audible impressions in another ride in the V552 Camry.

Although we were a bit hard put to tell the difference initially, except for road noise, the second stint in the V552 Camry allowed us to discern and enjoy the quieter ride after the harsher one in the V551 Camry. It appeared that we could tell the difference better after experiencing the noisier ride in the older tyre Camry.

The second impression was a drive in an Honda Accord with V552 tyres; this routine was to let us feel the wet braking performance (from 80km/h) of the newer Advan dB tyre as well as grip and handling stability through slaloms (50km/h), lane switching (40km/h) – both on artificially wet road surfaces - and a roundabout at about 40km/h. We were allowed to drive the course twice to gain a better insight into the new tyre’s qualities and we came away reasonably impressed.

After lunch, it was the handling and wet circle experience. The first involved a Mercedes-Benz C 350 e Hybrid that we would explore the new Advan dB V552 with through a curvy course. The recommended speed was 50-70km/h but we pushed the limits up to 100km/h through some sweeping corners and the V552s helped the C-Class to hold the cornering lines well, albeit squealing a little through the tighter bends. That speaks well of the tyre’s high grip limits.

The wet circle experience was an interesting one. Again the two Camry sedans were used. We started with the V551 Camry and were told to drive as fast as we could without losing control of the car around the wet roundabout, a huge one at 20 to 25 metres across. We found the Camry wanting to understeer (or wanting to go straight) as we approached 50km/h and the fastest we could drive was 51km/h as clocked. We drove around the roundabout three times.

The second drive in the V552 Camry was more reassuring as the sedan was more willing to turn according to steering input above 50km/h, allowing us to explore a faster pace. At 55km/h, the car was beginning to say it wanted to go straight instead of turning and we had to lift off the accelerator pedal to get the Camry back in line. The fastest we could drive was 56km/h, the highest speed for our group. That gives the V552 a 10-per cent improvement in wet handling.

The last routine was a fun one but with the sporty model of the Advan range, the Advan Fleva V701. The tyres were fitted to a turbocharged Honda Civic and it was a timed trial through a gymkhana course that comprised a slalom section, a lane change manoeuvre and taking a 10-metre roundabout. We were to drive through the course twice and the fastest three were given Yokohama-branded prizes.

The Fleva V701 proved to be a grippy tyre that complemented the Civic’s high dynamic qualities. When the combination was driven prudently, in particular braking hard before the entry into the lane change section and roundabout to reduce understeer significantly, we enjoyed the drive. And that showed when we clocked the second fastest time but only because we were given a time penalty for knocking into a cone.

That in a nutshell is what Yokohama Advan has to offer during our recent visit to the tyre test centre; silent tyre with strong performance or an out-and-out performance tyre that lets you enjoy a dynamic drive to the fullest.