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Sunday, 27 June 2010

Motorcycle tyre performance in the real world

If ever there's a subject guaranteed to raise blood pressure and provoke circular (no pun intended) argument, look no further than tyres!  Anyone incautious enough to ask on a forum "What's a good tyre?" will not only get conflicting results, most of the feedback will contain plenty of hot air and stuff-all in the way of qualitative facts.  Motorcycle magazines are only marginally better - lap times with the same bike using different tyres but how representative is that of the real world either?

In terms of main brand modern motorcycle road tyres, there's probably little difference between them in the performance envelope that most of us operate in, although there's no question that overall, tyre performance has improved markedly over the years.  Good news for all of us given the critical role they play in keeping us safe.

It's that old question about "fitness for purpose" because the term performance means different things to different people. Basically, sports tyres give incredible grip but (relatively) limited life and at the other end of the scale, touring tyres give longer life but a bit less grip. Manufacturers now try to blur these distinctions with additional options and we as consumers have seemingly endless permutations whilst trying to decide what's acceptable for the type of riding we do.

I wonder what others think about the subject of tyres?  Here's some personal experiences over the last few years that have marked the quest for tyres that fit my purpose.

Acquiring the Blackbird in 2001 was the first foray into riding what might be termed "hyperbikes" for want of a better word.  Enormous horsepower, heavy with a forward weight bias and conservative steering geometry that "pushes" the front end - those factors are an extreme test for any tyre.  It came equipped with Michelin 90X radials.  For the first few weeks, it could have had sugar-coated doughnuts on the rims and would have still been safe because I rode like a complete granny whilst getting used to it.  As confidence grew, a bit more power was applied, particularly whilst leaned over driving out of corners and the first limitations became apparent - the rear would spin up with little provocation in all but perfect road conditions.  The Michelins would have lasted forever because they were a pretty hard compound but in terms of grip, they struggled to cope with the new generation of performance bikes.  After 6 months of ownership, the tread depth had hardly dropped at all but they had to go because I'd lost confidence in them.  In wet weather, they were a nightmare.

The replacements were Dunlop D220's.  Better in terms of grip but as confidence grew in them and they were pushed a little harder, another problem manifested itself.  Have a look at the picture, particularly towards the bottom of the tyre:


As distance on them increased, the front tyre developed a terrible profile with big flats (almost concave in fact) from just off the centre line of the tyre running out towards the edge.  An under-inflated tyre could exhibit similar symptoms but it wasn't that as I was anal about pressures. The handling was horrible with it wanting to flop into corners. Fortunately, there was a lot of collected experience on the 2 major Blackbird websites and there was a strong body of opinion that most tyres simply weren't up to supporting the dynamic loads generated by heavy, powerful bikes when cornering and were almost certainly deflecting badly under load.  As already mentioned, the standard Blackbird has fairly conservative steering geometry with a weight forward bias.  To drive it quickly through corners requires a fair bit of countersteering and that exacerbates the problem.

Some manufacturers clearly recognised the problem and Avon brought out the Azaro "B" specification tyre which had additional reinforcing to reduce carcass deflection.  When the Hayabusa was released, Michelin shod it with the HPX, another reinforced tyre, for the same reason.  As soon as the Azaro "B" was released, I put a set on the Blackbird and the alarming front profile wear pattern disappeared.  Overall grip was pretty good too.  Clearly, the weight component and less extreme steering geometry compared with pure sports bikes had created their own particular set of issues.

Avon then released the Storm sport-touring tyre which was a further development of the Azaro "B".  This proved to be a real winner among sport-touring bike owners and is the Blackbird tyre of choice in the UK and NZ as well as with a lot of SV650/1000 and Hayabusa owners world-wide. I've had several of these tyres and whilst the good dry weather grip is probably on par with other major competing brands, the wet weather performance is the best I've ever encountered.  The other thing I like about Storms is that they keep their profile through a large percentage of their life, which means that handling remains uncompromised for longer.  Life was around 7500 km from a rear Storm which mainly consisted of spirited riding rather than touring or they would have lasted longer. Front Storms lasted nearly half as long again.  Overall, not bad for a heavy performance bike being pushed on grippy surfaces. Tyre life comparisons without replicating the exact road and road temperature conditions are pointless.  Where we lived pre-retirement had less-twisty roads with smoother surfaces and lower temperatures.  It is noticeable that the tyres lasted longer than where we live now.  This is a photo of a Storm rear:

Superb tread pattern for clearing water!

Mind you, new tyre development isn't always smooth sailing.  Four of us with Blackbirds fitted the newly-released Storms in readiness for a South Island tour in early 2007.  All of us experienced a low speed front end shimmy, two of them so severe that even rebalancing had no impact whatever.  A bit of networking both in NZ and around the world revealed quite a number of other cases and Blackbirds seemed to be particularly affected.  To cut a long story short, we worked with the NZ importer to gather data as well as with overseas users and Avon were able to identify an intermittent manufacturing issue and addressed it promptly. Far from the fault putting me off Avon tyres, it actually gave me confidence that here was a company that was willing and able to respond quickly to feedback.

Working with the NZ importer had a useful spin-off and I was subsequently approached in 2009 to formally evaluate a new pure sports tyre, the Avon VP2. It was a new generation tyre with a radical carcass construction to increase contact area when leaned over and had an overlay of 3 different types of rubber plus grip additives for wet weather.  I had severe doubts as to whether a pure sport tyre on a heavy bike was a smart idea but was pretty surprised at the outcome.  Firstly, the grip.  The VP2's were still effortlessly holding on long after my nerve had given out, both in wet and dry conditions.  They also had a great "feel", progressively rolling into corners rather than "dropping in" despite the aggressive profile (a high crown).  This was a clear example of just how good modern tyres are.  Most of us will never explore the outer limits of traction during normal riding but it's comforting to know it's there for those occasional "oh shit" moments!  Secondly, life.  The rear VP2 lasted for just over 5000 very hard kilometres which was a real surprise as I wasn't expecting much more than 3000km.  On a lighter pure sportsbike, the life would have been significantly greater.  I subsequently replaced the worn rear with a Storm sport-touring tyre, but kept the front VP2 on and it lasted for around 7500 km all up; a pretty good result considering that the 'bird tends to "push" the front end.  Had I kept the Blackbird, a Storm rear, VP2 front would have been the combination of choice for the type of riding I do.  The photo below shows the rear VP2 at 5000km.  The centre tread is down to the minimum depth indicator, yet there is no real indication of "squaring off" in the centre, a remarkable achievement by the manufacturer.  Carcass construction and the use of different rubber compounds for the centre and sides clearly have a significant influence in keeping a good profile for a big percentage of total tyre life.


VP2 profile has remained excellent over its life

Moving forward to recent times, the Street Triple came equipped with French-made Dunlop Qualifier pure sport tyres and I was prepared not to like them because of my past experience with the Dunlop D220's.  This proved not to be the case as dry weather grip far exceeded my modest abilities although in the wet, I didn't feel as confident with them compared to the Blackbird with Avons.  However, this is akin to comparing apples with oranges because of the differences in the 2 bikes - far too many variables to reach a meaningful conclusion.  At just over 6000 km, the rear tyre  needed replacing.  I was expecting a little more distance given that the Triple only weighs 167kg dry compared with the 230kg of the Blackbird but it's still ok for a pure sport tyre, especially given the type of roads where we live!  The front still had plenty of centre tread but it was developing flats on the sides and whilst the handling was still acceptable, the transition from upright to leaned right over was no longer linear in terms of "feel".  Here's a photo of the front profile and the flats are quite noticeable.


The following photo shows a different view of the front tyre wear.  Despite the high crown of sports front tyres, it also shows how far a bike can be comfortably leaned over in perfect safety.  The rear has no "chicken strips" at all and the high angles of lean weren't noticeable at the time because the bike felt so planted.


So what now?  A set of tyres that would last up to and beyond the forthcoming endurance ride in October were needed so the VP2 sports tyres I'd really like to have fitted might be pushing the boundaries of life until that time.  Besides, there aren't any in the country for a few more weeks and waiting that long wasn't an option. The new Pirelli Angels looked  interesting and early feedback seems very promising, but full-life evaluations over a whole range of conditions don't appear to exist yet.  However, Avon have recently released the Storm 2 Ultra based on the VP2 technology, only with sport-touring compounds so those are the ones I've just had fitted. Ok, so no-one has done a full-life evaluation on these either, but the purchase decision was based on the considerable experience mentioned above with the forerunners of this tyre.

In the dealer's workshop for new tyres

Far too early to comment on them other than saying that they feel very predictable and directional changes are rapid.  More performance comment to come in due course but for what it's worth, here's a  photo of the front hoop taken at the end of the delivery trip home.  As previously mentioned, the Storms have a deserved reputation for exceptional wet weather performance and that's a feature I'm particularly keen on!

Avon Storm 2 Ultra front tyre

From personal experience, its clear that all the major manufacturers are heavily investing in continuous improvement and that's great for us as consumers.  It probably doesn't matter at all what major brand you choose as long as it's matched to the type of riding you do and whether it's suitable for the bike in question; particularly whether carcass construction will adequately support the dynamic loads imposed by heavier bikes.  The real test is does it "feel" right and give you the confidence to ride in the conditions that you normally encounter.  For me, as previously mentioned; the decision to stick with Avons at least this time round, is largely based around my historical experience of their performance.  Incidentally, I was so used to the performance of the Avon Storms that it was possible to tell when tyre pressures were as little as 2 psi different from my normal settings!

I also mentioned earlier about being anal with tyre pressures.  This comes from bitter experience of gas station gauges which are notoriously inaccurate and correct pressures have such an impact on both grip and tyre life.  I carried an analogue AccuGage brand on the bike for some years.  These are bourdon tube devices constructed like a barometer and are very accurate.  Sadly, it slid off the seat at a gas station forecourt and that was the end of that!  I now have a reasonably expensive digital gauge which looks a bit more robust!

Whilst on the subject of tyres, some small CO2 cartridges and plugs for emergency repairs are normally carried.  Thankfully, they've never been used yet but I've always fretted about whether the 3 cartridges would be sufficient for a full inflation, especially when you're a long way from home.  They're no good of course for small pressure adjustments on the run either.  What I did recently was modify one of those cheap 12V compressors that you buy in automotive accessory shops.  They have large plastic cases which would be a pain to carry on a bike but the internals are very compact.  The case was removed and the accessory plug replaced with crocodile clips to attach directly to the bike battery.  Stick it in a plastic bag and instant air when needed!  The compressor gauge is ignored as it's just as inaccurate as those at gas stations.  My trusty digital gauge is in the photo too.

Mini-compressor for the bike

Finally, it's worth reiterating a comment from the earlier post on aftermarket suspension.  After the OEM Blackbird rear suspension was swapped for a top of the line Penske unit and the fork internals were replaced with upmarket components from the UK, the average improvement in tyre life was close to 2000km.  This is almost certainly a result of  the tyres having less dynamic stresses due to the suspension doing its job effectively.  Something else to ponder on!

Addendum: For an update on Michelin PR3 performance, click HERE




8 comments:

  1. Hi Geoff,

    The idea of converting the small 12v compressor to use on the bike is a good one - never thought of that!!

    I have one of the CO2 & plugs repair kits that I carry with me - luckily I have only had to use it once, and that was at home after pulling a nail out of the tyre.

    Loved your comment about the Blackbird still being safe even with doughnuts on the rims...

    Cheers,
    Anthony.

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  2. Geoff:

    you Engineering types are too smart for me. I carry around a compressor, plastic case and all, and I squeeze it under my seat. I also have CO2 cartridges but they are only good to "seat" the tire.

    I know you are the expert when it comes to tyres and different compounds and I agree with everything you say

    bob
    Wet Coast Scootin

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  3. Anthony & Bob:

    Driven by desperation really. I've never had cavernous storage space on any bike I've owned and my zip-together Ventura packs are usually full of other "stuff" on a trip away. I do have a small manual 2-way pump for my mountain bike which could be pressed into service but fear I'd fall down frothing at the mouth with a cardiac arrest inside the first minute.

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  4. Geoff:

    you're a Braggart. You probably couldn't last 30 seconds.

    the problem with those small, dual action, high pressure, pumps is their short valve extension. You are forced to hold it in mid air while you put it into action.

    I just had a brilliant idea. but I should patent it first or get you to make up some drawings. Put the manual pump inside the tubular frame with a foot mechanism.

    bob
    Wet Coast Scootin

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  5. All right Bob, I'll 'fess up - 15 seconds more like.

    Absolutely, and whilst the pump is waving around due to enthusiasm and then fatigue; I'm busy removing skin from my knuckles.

    That's a brilliant idea Bob - makes you wonder why no-one has thought of it before. Guess the world hasn't seen anyone so darned smart before.

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  6. Good bit of history on how tyres have improved over a few years. I was interested in how the Blackbird was hard on the front tyre whereas the Busa is light on the front.

    I have had Avon Storms on two bikes, liked them but don't think I will go back now I have a BT016 on the rear of the Busa. Wear is better than expected and hardly any flattening; I will be ready to report on this in a few weeks - depending on how much riding I get in.

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  7. Very comprehensive report Geoff. I was particularly interested in what you had to say about the Avon Storm Ultras because I am considering them for my Street Triple. I've gone through 2 sets of Dunlop Roadsmarts, and they are a good allrounder, but they have let go a couple of times in the wet when it is cold. We've had a lot of rain in Sydney this winter and the Storms have a good rep for wet riding.

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  8. Thanks Jeff. If you'd like the full reports I did for the importer, use my email function and I'll mail you them.

    I've done some more k's now and I love the Ultras even more now - very reassuring in all conditions. I'd happily stick with them but next time, I'll probably go with a Storm Ultra rear and a VP2 Sport front combination just like I had on my Blackbird. For the type of riding I do and the area we live in, it's probably the best combination.

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