Saturday, July 24, 2010

Buying a New Front Tire for the Vulcan 900

Motorcycle tires are a great disappointment compared to car tires. One of the worst tires I ever had came on the rear of my new 1972 Yamaha 250, and lasted only 2000 miles before I needed a new one. Today, they last longer, but are still far behind cars for tire technology. My Vulcan 900 Classic is still using bias ply tires with tubes inside. Car tires can give me almost 100,000 km of use. Typical touring motorcycle tires last about 20,000 km on the rear, and 30,000 or so on the front. Of course, there are great variations in these figures, depending on the type of tire and motorcycle, and how it is ridden. I am talking about my own usage, where I drive pretty moderately, and I go for the longer lasting types of tire.

One reason motorcycle tires wear out so fast is the round profile that they must have to be able to balance and steer properly. Car tires can have a rectangular profile with a big flat part of the tire against the road. This would never work with a two-wheeled motorcycle, as they must be able to lean over and that means you must have a rounded cross section tread. With a round cross section, only a thin strip in the middle touches the road, and that strip gradually flattens out as it wears, until the tire is unusable. With a motorcycle, the tire usually becomes dangerous as much because of the flattened (or square profile) as it is because of lack of tread.

The rear tire almost always wears out faster than the front, not because of the extra weight, but because that is where the propulsion takes place. Some studies have indicated that adding more weight at the rear actually reduces the wear on the tire. As the rear tire pushes the bike forward, it slips a little against the road, which tears off a small amount of rubber on each rotation. After 15 - 20 thousand km., you usually need a new rear tire.

Front tires also wear out, mostly because of braking. Front tires have an additional problem, in that braking only works in one direction, and the resulting unidirectional forces may eventually produce uneven wear called cupping. This is almost like a series of scoops taken out of the tire, each about 8 cm. long. The rear tire is not affected as much, because it has force applied in two opposite directions, by braking or acceleration, which evens out the wear.

Another thing you may notice about tire wear (if you take it that far) is that the first part to wear out completely is not directly in the centre, but just off a little to the left (about 1-2 cm. in most cases.) This is because we ride on roads crowned in the centre, and we always ride to the right of the crown. Well, not always, but 90% of the time. Riders that drive on the left (like the UK) have this bald spot usually appear on the right of their tires.

Although many riders like to get two new tires at the same time, I prefer to get a new front tire only every second time I get a rear tire. Usually this works out well, but right now I have a new bike, and I made a miscalculation. I replaced the rear tire at 18,500 km, with a Metzeler ME880 tire. But by the time I got to 36,000 km and the front tire obviously needed replacing, the Metzeler was still looking almost new. After 21,000 km of riding, it still has deep treads, so I have bitten the bullet and ordered just a new front tire. This time I'm going with a Bridgestone Exedra G703.

The new rear Metzeler ME880 was a surprisingly long wearing tire, possibly the longest life of any motorcycle tire I have ever had. And in fact I might have preferred a tire with slightly more traction at the expense of shorter life. I have noticed several times, that this rear tire broke traction on me. One time when it was raining, and I accelerated from a stop sign onto a high speed road. Another time, the road was dry, but it was cold and I was going around a traffic circle. (actually that happened twice.) Then, a lot of times when I was braking only with the rear tire, even on a dry road, but maybe that was my fault. At the time I was trying to speed up the wear on the back one, so I could replace both together.

I would not want a tire like this ME880 on a sport-touring bike for three reasons. Stronger brakes, more powerful engine, and greater lean angles.

So, without much research I ordered the Bridgestone Exedra G703, which is a front tire. Even when I started motorcycling, tires were designed specifically for the front or the back. But today, it seems tires of one given size and type are also designed for the model of motorcycle.

Just like in the business of buying car tires, there are more complications. According to Bridgestone, the tire is available in tube type or tubeless, and I'm not sure why there needs to be a difference. It is also available in an H (210 kph) or S (180 kph) speed rating, and I will have to learn what these two unknowns are when it arrives. I probably should have done the research first, but then I actually ordered an S11 Spitfire, and I was called back to say it's on backorder and I could try a different (and more expensive) model. So I made a snap decision anyway.

This is what Bridgestone has to say about them "Designed primarily for American-type motorcycles, Exedra series provides long mileage, good straightway stability, easy handling and riding comfort."

Because this is "adspeak" you need a translation. "American-type"=Slow riding but carrying a lot of weight, "Long mileage"=about 30,000 km on front, "staightaway stability"=you can forget about taking corners at speed, "easy handling"=way better than hard handling, "riding comfort"=this tire is round.

Picture: I photoshopped a G703 tire on to My Vulcan (It has not arrived yet, but I want to see what it will look like.)


  1. OK, I admit it ... you faked me out with that shot of your front tire. I thought you'd actually gone and replaced that 'slick' you were running on our trip to Lake Huron!

    I keep procrastinating on my tire replacement decision. The OEM tires on my Kawi W650 are Bridgestone Accolade AC03/AC04. These supposedly are 'high performance tires' with the 'vintage' look in keeping with the 1970 Brit bike styling.

    However, although I find the tire's centreline groove reassuring in the wet, it does make riding over bridge gratings and repaving grooves a misery.

    So I remain conflicted between retaining the 'retro' look or replacing with something like Bridgestone's BATTLAX BT-45 with its oscillating centre groove.

    Or something else entirely ... although the 'retro' rim sizing does limit choices if one wants front and back tires of the same family :-(

    Enjoy your new tire, but don't forget to take it easy until that new tire residual mold release goo has been well and truly scuffed off ... LOL!

  2. I was going to suggest the Dunlop K70, which I used on my '72 Honda CL450. But it is only available in actual vintage sizes, like 3.25x19. The outside diameter of that tire (which is closest to the W650) would be 26.58 inches, while your original equipment tire is 26.34.

    Dunlop K70 Tires

    Also, the K70 still has a straight centre groove. But then I'm not sure that the squiggly centre groove really helps that much, maybe it's more psychological than real. In any case, once you get down to the cord, the tread pattern ceases to be much of a concern. How much riding to you do on grated bridges and grooved highways? Another problem with the K70, its speed rating is P (150 kph) not really a problem for the CL450, but way below your current tires which are H (210 kph)

    Those Battleaxe tires are rated V (240 kph) which may be way more than you really need. That might mean a stiff sidewall, I'm not sure. Probably means more expensive, but I didn't check the prices either. And they are only tubeless type, which I don't think you need, but again I don't know if it's a negative thing or just something factored in to the price.

    I never did care for the look of the ribbed front tires much, and the only ones I ever had were because they came with the bike. But that's just a personal thing, I'm sure they work just fine, maybe even better than most tread patterns on the front. I always imagined that they were bad on gravel, because you never saw a scrambler with ribbed front tires.

    It does seem like the W650 has limited tire availability because it has tires approximately the size of vintage tires, but not exactly. Anyhow it seems there are a few choices.

    Advrider Kawasaki W650 Discussion on Tires

  3. Thanks for the link to the W650 tire discussion - that helps.

    Yeah - I'd forgotten all about the tube issue. And that is an issue with spoke wheels.

    I've simply heard too many arguments about whether or not one should put a tube in a tubeless tire, so I'll have to see if I can discover some 'truth' about this question.

    Oh, sigh ... something to look into next winter ;-)