November 30, 2011

Yamaha SR and the Dunlop TT100 Roadmaster

Tyres are obviously an important feature on any bike and the final choice when buying them are often dictated by a mixture of performance, look and price.

There is a great variety of tyres for the SR, but after doing some research on various websites and forums, I eventually found there were 2 main competitors for the cafe racer style crown:
the Bridgestone Battlax BT45 and the Dunlop K81 TT100 Roadmaster. 

So what's the difference between the two tyres? The answer to that question is a very subjective one.
The BT45 is an excellent tyre and the first choice for SR riders all over the world due to it's outstanding grip, fast response and durability.
Dunlop Battlax BT-45

However, if you're an SR rider who appreciates the vintage design of the original Dunlop K70, but don't want to put up with it's vintage technology (read: dangerous), you might like the TT100 Roadmaster. 

The TT100 Roadmaster is by far the number 1 tyre choice in Thailand and I talk from personal experience when I say that it is indeed a great tyre. If you don't believe me, read the following reviews:

You have to be pushing it fairly well to get the TT100/K81 DUNLOP to slide or be on a poor/slippery surface. The key thing with these tyres are that when they do let go and start to slide, the whole transition from grip to slip is predictable. You can feel the tyre starting to get "squigglie" as you push harder through the turns and if you go a bit harder they will let go fairly "slowly". I have ridden on some tyres that seemed to go from full grip to absolutly no grip instantly, and they are the tyres that hurt, as you have to be real quick to catch the slide, and quite often when you do catch it, you end up going over the high side. With the low power output of the SR and the smooth easy way it delivers the power, it is quite easy to control a SR when it starts to slide, no matter what tyres are fitted.

I have fitted and ridden on DUNLOP TT100's (AKA K81's) almost exclusivly since I bought my first SR back in 1980. I tried PIRELLI Phantoms and a few other "performance tyres" in the 1980's but always went back too the DUNLOPS as being the best compromise between wear, grip and predictability . They don't give as good a grip as some of the newer tyres such as the BT45 Bridgstones, but they wear well and give more than enough grip for most riding situations that you will subject a SR500 too. Having said that they will let go and slid if you push them too hard, but if you are riding that hard you should give up the SR and buy a modern sports bike. When they do let go they are quite predictable. 
from SR500 forum

What inspired me first to write this blog entry, was an article about the TT100's history which I found very interesting. Here it is...

written by Jim Reynolds

One day in 1967, Dunlp's chief motorcycle tyre designer Tony Mills got a call in his Birmingham office. It was Doug Hele on the line, the man in charge of development at Triumph, who wanted to discuss a tyre for a new model being worked on. The 750cc three-cylinder Trident. Hele explained that the bike would be high performance model with ace tester and racer Percy Tait doing the testing.
Mills and his team of David Buck, David Lamb and Graham Barton based their thinking on the popular triangular section racing tyre and produced a 4.10in (104mm) section, in what David Buck called the Trigonic shape, to fit Triumph's standard 19in rim. It used a four-ply nylon bias-ply construction to accomodate the Trident's weight and for extra grip they used a tread compound similar to that in their race tyres. Named the K81, it was tested at the Motor Industry Research Association testing ground, near Hinckley, Leics, and got a strong thumbs-up from Percy.
Out on the road, including some very illegal speeds down the stretch of road known to the factory testers as The Meriden, it passed with flying colours. When the Triumph-BSA Group launched the new Trident and Rocket-3 modelsthey wore K81s and Norton's Commando did the same. It was unique in having a directional rotation arrow moulded into the sidewall to make correct fitting more simple.
Triumph entered 650cc T120 Bonnevilles in the 1969 750cc Production TT, wearing K81s because road legal tyres were compulsory.
It's a matter of history that Malcom Uphill was the hero of the day, putting the production lap record over 100mph for the first time and winning at a record 99.99mph race average. More than that, it was the first time a road legal tyre had put in a TT lap at the 'ton'; history made in two ways. It was too good a chance for Dunlop's publicity people to miss; they renamed the boot the K81 TT100 Roadmaster and a legend was born.
It went on to be produced in 18in rim sizes and a variety of widths up to 4.25in (108mm) at the rear and 3.60in (91mm) up at the sharp end, at Dunlop factories in England, France and Japan.
What's more, when the company produced a new race tyre for the 125cc class in 1977, it was called the TT100GP - that won several World 125 Championships plus National titles.
It's still in production, at Lucon in France, in the original 4.10x19in size, but continual development work has seen it changed from four- to three-ply construction. Forty-two years after it earned its title, the legend lives on.

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