RAGS REPORTS ON TIRES
by Frank "Rags" Rago
Cold Tires No Air and the Jump
Late last Fall I saddled up on the CB 750 and took off down the road for an afternoon of twisty turns and a relaxing ride on a few of these Georgia back roads. Everything started out fine until I hit that first right turn and felt it, “The Jump.” What was that? That has never happened.
What happened was that when I took that right turn my back tire lost traction and my whole back end jumped a few inches to the left. My surprise was masked by instant transfer from road rider back to my dirt bike days. Keep the feet on the pegs, throttle steady, DON’T hit the brakes, and let the bike straighten out naturally.
I continued riding and had a great day in the mountains with no more jumping, but the question still remained. Why did my back tire loose traction?
After a bit of reading and research about tires, pressures, and heat I found out the answer. First there is such a thing as Cold Tire Crashes. These are motorcycle accidents due to cold tires. You see, tires need to warm up before they “grab” the road. Tires also have optimum operating temperatures for best gripping or stick to the road.
When tires are below the optimum temperature they will easily loose traction on a perfectly dry road that has no dirt or debris on the surface. In my situation I just did not ride long enough to allow my tires to heat up and “grab” the road. Other reasons for loss of traction are too much air in tires and not enough air in tires.
Too much air will decrease or make a smaller footprint on the road surface. A motorcycle footprint is really small to begin with so you want as much as possible when riding. Not enough air will increase your footprint on the road surface, but the chance of the tire going one way and the rim going the other may cause the tire to roll off the rim. This is not a good thing. Another factor that may cause a terrible riding condition is putting cruiser tires on a sport bike or vice versa.
This was interesting since I had been throwing around the idea of putting endure tires on the 750 to get more of a Scrambler look and possible dirt performance. I have since shelved this idea since I do enjoy twisty turning roads and really hate eating pavement.
One thing I have to admit that I do is to take my tires and air pressure for granite. How many times have I just jumped on the bike and took off not thinking twice about tire pressure. This has changed since reading and doing my homework for this article. When you ride and your tires hit the optimum temperature, the air in the tires can increase tire pressure upwards of 10%. For this reason you must check your tire pressure when the tires are cool. This is usually before you ride or 20 minutes to 3 hours after you stop. Yes, that seems drastic, 20 minutes to 3 hours but this is opinions vs tire manufacturer requirements. You need to make this call.
Here are a few tire checks for you to consider:
1. Check tire pressures on a regular basis. Weekend riders this can be once a week prior to hitting the road. If you are on a trip for the long haul then it is wise to check your tire pressure a couple times a day.
2. Always check your tires when they are cold. Prior to hitting the road is good and maybe after taking a lunch break would be smart. This will also allow you to check for foreign objects that you may have picked up.
3. Use a quality tire gauge. Do not bet your life on a tire gauge at the local service station that is thrown down, banged up, and probably out of calibration.
4. Stick to the tire manufacturer’s air requirements. I know of those who ride rigid bikes and let air out of their tires for a softer ride.
5. If you are riding on brand spanking new tires, give the tires 100 miles prior to getting on it in the turns. Tires actually have a break in period.
6. Never ever add air to hot tires. If you do you are risking over inflation and a blowout. I did this in a car and it was not fun. Wait the 20 minutes to 3 hours for safety.
7. **If you are riding on cold tires and have to take a tight turn, remember to accelerate after coming out of the turn when you are not leaning. If you hit the throttle in the turn you could lose traction and the bike may jump like it did on me, or worse.
It is 2015 and many of us have cell phones that have all kinds of apps and internet capabilities. One thing that I have done is to find my bikes spec sheet and saved the page to my phones home screen. The information highway or I can just look on the side of the tire. I would like to thank Rideapart.com and Sportbike.natkd.com for my tire education.