Dispelling the "What's the Best Tyre" myth
In view of the hot air (oh, ok - absolute bullshit) which seems to blight any on-line discussion about tyres, including a complete lack of evidence to support some assertions about what tyre to buy, let's start with some facts which have a bearing with respect to tyre performance on public highways.
- It's likely that unless a rider is supremely talented, any of the major brands will offer a performance envelope which more than exceeds most people's capability. What WILL have a large bearing however, is their "Fitness for Purpose". e.g track day capability, predominantly commuting, riding in dry weather only and so on.
- There are many variables which impact significantly on tyre performance and life...... road surface and temperature, ratio of straights to curves, weather conditions, tyre pressures, suspension quality, bike weight and geometry - just to name a few. Also chuck in a rider's variables in terms in terms of speed, smoothness, their weight and god knows what else and it becomes clear that finding one tyre design that meets all criteria is close to impossible.
- Bike magazines which test normal road tyres round a test track for lap times don't replicate real world public road conditions either. In other words, we're not comparing apples with apples in most cases.
Past experience with the Street Triple
The Triple came equipped with sport-oriented Dunlop Qualifier 2's. The Qualifiers gripped really well in the warmer weather but I was nervous about them in cooler, wet conditions. I got the same feeling when riding a friend's Daytona 675 equipped with Pirelli Supercosas on a wet and cold day. It's not an unreasonable statement that pure sport tyres need heat to maximise grip and in wet, cool conditions, that's not easy to achieve. The generally smaller rain grooves on a sports tyre don't help either. That probably means that in adverse weather conditions, a pure sport tyre has no performance advantage and possibly less; than sport-touring tyres. The Q2's with higher profile crowns than many sport-touring tyres also tended to tip into a bend rather than roll in smoothly but this was something I eventually got used to. By 6000 km, they had lost much of their tread and equally importantly, the profile had changed significantly which affected handling.
Dunlop Qualifier front tyre. Losing shape and nearly down to the min legal 1.5mm tread depth in the centre
The next tyres to be fitted were the Avon Storm 2 Ultra sport-touring tyre. I was due to ride in the NZ Grand Challenge 1000 miles in under 24 hours event and wanted something which could handle adverse weather conditions. Avon Storms were my tyre of choice for several years on the CBR 1100XX Blackbird which I previously owned, so was familiar with their characteristics. They are a great all-round tyre with exceptional wet weather performance, finally being replaced after 10000 km. The tyre profile remained pretty good for most of their life.
Avon Storm rear tyre at 8000 km. Harder centre compound clearly visible
Experience with the Michelin PR3's
I would have happily used the Storms again except that the NZ Avon importers had hiked the price and that was the spur to consider other brands. The relatively newly-released PR3 sport-touring tyres were finally chosen mainly because the fine grooves (called sipes) which are traditionally used on some performance car tyres were an interesting point of difference. A point of note is that I fitted the "B" specification rear PR3 which has a stronger carcass construction and higher load rating.
PR3 "B" load rating identification
Brand new front PR3
Brand new rear "B" load rating PR3
Coming out of the tyre fitters and rolling slowly towards the nearby traffic lights, there was a slight vibration through the bars, almost as if the bike was running over small corrugations. I wondered if the sipes on the front tyre were causing the vibration as it happened at a couple of other slow speed locations too but didn't reappear at the end of the 160 km journey home. Maybe everything had bedded in by then.
Most of the homeward journey was on twisty, back country roads; perfect for carefully exploring the capabilities of the PR3's. They exhibited a smooth, progressive roll-in on bends as opposed to the more rapid tip-in of the Qualifiers with the higher crowns. However, they "felt" slightly slower to roll in than the previously-fitted Storm Ultras but to be fair, the difference was small. Overall, they were totally confidence-inspiring.
Being anal about tyre pressures, I checked them using my digital gauge the following day. The tyre dealer had set them to the recommended Triumph pressures which at best can only be described as a guide. Where I live in NZ, summer road temperatures are quite high which means that you can start with a slightly lower cold pressure. (Ever checked the difference between cold pressures and the operating pressure at the end of a lively ride???) In addition, I ride solo, weigh 80 kg and have found that 35psi front and 38 psi rear seems to work well. The other thing which was checked on arriving home was front/rear wheel alignment, using my home-built laser rig and it was a mile out. I've never seen an alignment rig of any sort used by tyre fitters anywhere so it's hardly surprising. Misalignment can affect both handling and tyre wear so setting it up properly on a new set gave peace of mind.
In terms of dry weather grip, the PR3's are good enough that I reach my level of competence well before the tyre is inclined to get squirrelly. In the wet, they are simply amazing - not an anxious moment. Even when I once hit wet clay, the slide was completely controllable. Perhaps as much due to the wonderful handling of the Triple as the tyres. The sipes actually seem to work as opposed to being a straight marketing gimmick as riding partners have remarked on how much water the tyres seem to displace and the strong dry line they leave. I always thought that Avon Storms set the standard for wet weather riding but have to admit that the PR3's are even better. Admittedly, the comments about relative grip are subjective but I reckon based on experience with different tyres on the same bike, they're pretty realistic.
Having established grip credentials, we now move onto tyre life which as mentioned earlier in this post, is affected by a multitude of factors. However, as also mentioned, the 3 different tyre brands which have been fitted to the Triple since new have been used in near-identical conditions. Therefore, a comparison between the 3 is valid. It's also worth mentioning that the Triple isn't used for commuting and I live in an area with really twisty roads so the wear is probably more evenly spread round the surface than it would be with a greater percentage of upright riding/commuting.
Just to recap, the Dunlop Qualifier sport tyres lasted for 6000km before they were replaced due to wear and going out of shape. The Avon Storm Ultras lasted for 10000 km before being replaced. They retained a decent profile for perhaps 90%+ of their life. The photos below show the PR3's at just over 13000km.
Rear "B" load rating PR3 - 13000 km
It can be seen that the rear hoop has maintained an excellent profile. The rain groove depth towards the centre is approximately 2mm, indicating that the 1.5mm minimum legal tread depth will be reached in less than 1000km. From my perspective, a total life of 14000km is perfectly satisfactory given that the Triple is used as intended by the designers! Just out of interest, compare this photo with the one of the brand new rear PR3 above. In the brand new photo, the major rain grooves coming from the left and right hand edges actually reach the tyre centre line. In the 13000 km photo, the end of the grooves are close to 8mm from the centre line, showing how much wear has taken place. The sipes have also narrowed in width as they have worn.
Rear tyre - view of tread towards edge - 13000 km
The rear tyre is worn right round to the edge but the rain grooves and sipes have maintained fairly sharp edges. It's hard to see in this photo but the trailing edge of each sipe has a distinct raised feather edge. There doesn't seem to be any adverse consequences from this,
PR3 front tyre - 13000 km
As with the rear tyre, wear is evenly distributed and to within 5mm of the front tyre edge. Remaining tread depth is approximately 2mm in the centre. With the lighter loads on the front tyre, it will almost certainly last considerably longer than the rear. I generally change both tyres together but there may not be any compelling need in this instance. It will be reassessed shortly.
Given the life of the PR3 compared with the other tyres previously used, it brings into question the wisdom of comments on bike web forums which simply dismiss certain tyres as being too expensive. The Avon Storm is currently a little cheaper in NZ than the PR3 at present but taking into account the difference in wear rate, the PR3 lifetime cost is significantly cheaper. If a pure sport tyre fits your riding requirements best, their reduced life means you're going to shell out more $$ on a regular basis. It's also appropriate to mention the impact of suspension on tyre life. If you have either tired or budget suspension where the effectiveness of spring rate and/or compression and rebound damping is questionable, it will definitely have an impact on tyre life (and handling of course). When I changed from the standard suspension on my Honda Blackbird to modified front fork internals and an expensive Penske adjustable rear unit, the tyres lasted on average for an additional 2000 km. A plausible argument if you have to go cap in hand to your Chief Financial Officer to spend money on the bike, ummmm..... like I do!
There is actually one unquantifiable variable in the last 18 months of Street Triple ownership which may have appreciably contributed to the excellent tyre life of the PR3 and that's the on-going enhancement of my riding with the Institute of Advanced Motorists. In addition to being a safer rider, I'm a smoother rider thanks to much better positioning and smarter use of throttle, gears and brakes. This must have a beneficial bearing on tyre life, although how much is open to debate.
Conclusions
In summary, the PR3 tyres are the best I've ever had on the Street Triple for the type of riding I do. The ST gets ridden pretty briskly but it doesn't have to put up with, for example, the requirements for track days. If I was a track day junkie, then a pure sport tyre would be the most appropriate option.
Philip, the NZ IAM Chief Examiner has PR3's on his Honda ST1300 and they were beginning to lose a little shape at 6000 km but are now up to 9500 km. Part of this would be due to a long fully-loaded trip he did on them on relatively straight roads and the overall weight of the bike must also be a significant factor. Nonetheless, that sort of life on a big bike is still acceptable. He intends to fit another set of PR3's. My fellow moto-blogging mate Roger also has them on his Triumph Sprint ST. Whilst Rog hasn't had them on for long, he speaks highly of their performance.
Clearly, there is no one best tyre, it all comes back to that all-important "fitness for purpose" which an individual owner wants from his machine.
I hope that this post has provided some food for thought!
Oh, and a final thought which only occurred to me the other day. 2013 will mark the 50th anniversary of owning my first motorcycle. Guess that shows a decent passion for motorcycles, as well as definitely confirming Old Fart status :-)
Addendum: I changed the front PR3 at 17,200 km. The tread depth was still just above the legal minimum but the profile had lost its shape, taking a more triangular profile with significant wear on the sides. Hardly surprising really given that I live in an area with hardly a straight road and only ride for fun, not commuting. It always comes as quite a surprise how the handling is rejuvenated by a new tyre!
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