Front Tire Cupping

[frayne]

Just did a search and didn't find the answers I was looking for. The other day I was pushing the FJR around in the garage and felt some bumps on the front tire when I didn't have it exactly vertical. In looking over the front tire I did notice some even and uniform cupping on both sides of the front. I'm running Bridgestone B-20s. I rode about 250 miles yesterday and didn't notice much difference in handling while at speed but I did notice some front end tire noise while cornering. The front has about 10K on it and the back tire about 7K so I'm going to be in the market for some new rubber in the hear future. Couple of questions for the more experienced here;

Are there any safety issues with riding on a front tire that has some cupping ? I always check my tire pressure before each ride and keep the front somewhere between 36-42 psig and the back right at 40-42 psig. I am not quite down to the wear bars in either tire but probably will be in the next thousand miles or so.

What is a good long life tire for the FJR ?

And last but not least, any idea on what may have caused the cupping and what can be done in the future to prevent it.

I appreciate any and all responses.

 

[twowheelnut]

Yeah, it's okay... Annoying, but okay. I also wouldn't wander into triple digit territory too much. As for the longevity - I'd say you are about average with the mileage you listed. I'd swap them soon, IIWY.

 

[OrangevaleFJR]

BT 020's are renowned for their cupping. The BT 021's are much better in every way as far as I'm concerned.

The cupping on the 20 can be bad enough to make riding not as safe as it could be IMO. I'd change them.

Front tire should be at 40PSI. 1 lb makes a difference. 4 is too much variation imo.

 

[rainman]

I switched from Bridgestones to Metzeler because of the cupping I was getting with the BT020. I am now running Pirelli's as they seem to get more mileage. Only annoyance I experienced from the cupping was as you described. I don't think I have ever gotten 10k miles out of the front tire from any brand.

 

[racer157]

The cupping is normally a sign of underinflation. The tire distorts due to a lack of proper inflation. This can be even worse with a large wind screen that applies even higher loading on the front end of the bike. Check your tire inflation before every ride. What year is your bike and what is the total weight of you and the bike? What kind of tires are you running (brand)?You can calculate the proper inflation by taking the total weight of the bike and rider and multiplying it by 60% for the rear wheel and 70% for the front wheel. devide the number into the max load given on the side of the tire and multiply the result by the max tire inflation number and you will get a good starting point for good handling and wear. Here is a example.

Bike and rider wt 900lbs x 60%=540lbs max load on side wall of tire is 620lbs at 42psi . Devide 620 into 540 you get .87percent . multiply 42lbs times .87 you will get 36.5 or a starting point of 37 lbs of inflation as a starting point . Note if you add a passenger or weight in you bags add this weight to your 60% total and finish the calculation.

This is a method I and many roadracers have used over the years as well as many touring clubs. I hope this helps you. Wink Winckler AKA Racer157

 

[OrangevaleFJR]

bt020's cup no matter what. be done with them and move on to the next generation:

storm

p2

bt021

any of them

Or whatever anyone else supports.

but 020's aren't anybody's favorite.

 

[bramfrank]

1. My '06 says 42/39 for inflation - and you are supposed to use the manufacturer's specifications for air. That applies to cars and tires. Fill the front to 42 for best performance. If yours is another year and if the spec is different, then use whatever the manufacturer said to.

2. Check pressure regularly

3. Set pressure only with cold tires.

4. ALWAYS USE AN ACCUTIRE ELECTRONIC PRESSURE GAUGE. Mechanical gauges suck and some brands of electronic gauges simply aren't reliable. I have six Accutires and they all read exactly the same and it matches the five transponders in my car. The local Goodyear tire center changed to Accutire gauges after they changed the tires on the cage and I demonstrated the accuracy - and just how INACCURATE theirs were.

5. Cupping makes noise when you corner. If you have tread and the tire isn't cracking (which it almost certainly is not) then the only impact is noise. Ride it till it wears out.

 

[fossilrider]

Some information on Common Motorcycle Tire Wear Patterns, including cupping.

Tire Wear Article

john

 

[El Gordo]

BT020s fronts all cup and will cup faster if you run them soft. I ran mine for 15,000 km. (9375 mi.) It was quiet when running straight but made a lot of noise turning. I took them off when the front started getting squirrelly on tar snakes while turning. Instead of sliding a bit and hooking up, it started to slide then wobble a bit and give me feedback through the bars. My BT021s make some noise all the time but are a very confident feeling tire.

 

[jorstin]

Yea mine cupped to on my 05 i did not no any better and got a little spooked and changed to roadtec Z6 tires

Steve

 

[TruWrecks]

Cupping means the rubber is distorting to grip the road. The BT020's will distort with any pressure, but will distort faster if the pressure is too low. At 9000 my front tire was toast, and slightly cupped. The rear still some tread left, but I replaced it with the front to keep the rubber compounds the same. I like the front and rear to be predictable when grip matters.