Tire Questions & Answers | Shop Talk

Got a question? Try to stump Mark at zimmemr@aol.com

Got a question? Try to stump Mark at zimmemr@aol.com

Tire Hijack

I have a 2009 Victory Kingpin in need of new rubber, and my dealer told me I have to put bias tires on the bike (a Dunlop 180/55 B 18 in this case). Is there another tire I could use instead? The Dunlop tire I mention is exclusive to Victory bikes and I can't buy it anywhere else but the dealer, which is going to cost me an arm and a leg. Also, can you tell me the difference between a bias and a radial tire?
Fernand Goguen
Via e-mail

The difference between radials and bias belt tires has to do with the way the tire belts are wrapped; unfortunately, that’s too lengthy a subject to explore here. If a tire manufacturer has radials that fit your bike and lists them as such in their catalog then I see no reason you can’t use them, or any other brand of bias belts you prefer.

To find the appropriate tires without going through the dealer, use one of the tire locator charts on the Avon, Dunlop, Metzeler or Michelin etc., web sites to find what you need. I like Avon Cobras, and they make them for your bike. However I’d check all the sites just to see what’s out there.

Under Pressure

I remember reading about tire pressures in Motorcycle Cruiser magazine and how to tell which pressure is right, but I don’t remember what issue it was. I have Avon Cobra tires on my 2007 Kawasaki 1500 Vulcan Classic. I weigh 235lbs. My front tire pressure goes up 2 psi from cold to riding. My back tire goes up 5.5 psi from cold to riding. Didn’t the article say that the pressure is only supposed to go up 2 psi if it is properly inflated?

Also, how accurate is the maximum psi reading on the sidewall? The front tire says "Maximum 40 psi", but Avon said to inflate it between 40-42. It is at 41 psi. The rear says 42 psi, but Avon said to inflate it to between 46-50 psi. I have it inflated to 48 psi.
Scott Daly Via email

First, understand that the maximum pressure rating on the tire’s sidewall is just that; the maximum pressure that the tire is designed to safely use. Normally it should only be used when the bike is fully loaded (for example, with two riders and a full load of luggage). Under normal riding conditions the tire pressure should be something lower than the maximum, and yes, the max pressure warning should be taken seriously. That being said there are times, under special circumstances, when it can be exceeded, but only if the tire manufacturer allows it.

The rule of thumb (and that’s all it is) concerning tire pressure is that when a tire is properly inflated, the difference between cold and warm pressures should be between two and three pounds. Due to the excess heat created, an underinflated tire will show more of a rise, while an overinflated will show less. In your case it would appear that the front tire is close to perfect while the rear is somewhat underinflated, so all things being considered I’d say leave the front alone and up the rear by a pound or two and recheck everything.

However I’m a little concerned with two things. The first is that your pressure recommendations don’t jibe with the Avon website listing of 33 psi (front) and 38 psi (rear) for a solo rider on a Vulcan equipped with Cobra tires. In light of your weight that’s understandable, but I’d have thought somewhere around 34 to 36 psi in the front and 38 to 42 in the rear would have been fine.

Secondly, they’re higher than the maximum load pressure, which is unusual, though not unheard of. If it were me, I’d go back and recheck your source, but if the pressures you’re using were recommended by Avon, then I’d have no problem with using that. Assuming that’s the case, I would increase the rear pressure to 50 psi and see what happens.

Check Please!

I am having a small issue with my 2005 Suzuki C50. Since I bought it, the LED readout on the speedometer has been flashing a CHEC light. When I told the dealer what was going on, he told me that that was just a fluke with that make of bike, and not to worry about it. At the next service I mentioned it again, and this time the mechanic found a faulty wire. He changed it out, which seems to have cured the problem for a while.

Then I went to another dealership and mentioned the “CHEC” problems. The shop foreman called Suzuki, and they warrantied the part even though the warranty had expired.

This new wire has lasted about two years. Now I have the same thing happening all over again. After all this time, I would feel funny calling Suzuki, and expecting them to make good on words spoken two years ago.

Any advice?
Terry Becthold
Via email

The problem with your C50 is a fairly common one, which is why the original dealer just happened to have the correct part “on hand.” Apparently the front cylinder’s ignition coil creates a magnetic field around the portion of the wiring harness that passes by it, which sets off the check engine light. Suzuki has tried several fixes, including relocating the appropriate section of the harness and replacing it with a shielded piece. I would contact Suzuki’s customer service department and explain the situation; whether or not they stand behind their promise, especially on a seven-year old motorcycle, I can’t tell you, but it’s worth a shot.