Front Tire Bounce

[DGXSER]

IMO, that is ALOT out of round for a tire.

As to getting a mail order shop to honor warranty, good luck. We bought tires once....ONCE...from Tire Rack. One had a slipped belt. They told me I had to purchase the new tire, have the old one shipped back to them as well as pay for shipping the new one to me. Then they would evaluate the old one and let me know what if any they would pay after pro-rating it. I told them I could get a new tire locally for less than the shipping fees and they were not going to reimburse any of those no matter what.

[bikerphil]

Yep, 3/16" seems like a lot. I just checked the vertical runout of the front tire on my Standard for comparison. I get 3/64" on this Shinko 712 with 5K miles on it. Seems like there is a 12" long section of the tire with this larger gap. I'm gonna check my buddy's rim for vertical runout with a dial guage also. It could be partially the rim's fault.

[Electronhammer]

I may be way off base here, but someone once told me that worn neck bearings can cause wheel/tire bounce. I was told that over a long period of time the bearing(s) can develop a detent. Again I may be way off base, but thought I would throw it out there.

[CatatonicBug]

3/16" is more than enough to make it bounce. That's about what I had, and it shook the knobs off the radio!

[bikerphil]

Here's what I've found out on the runout of my front tire. You have to check when the tires are warm. There will be a flat spot on a cold tire from the bike sitting. Took the bike out for a good ride, then immediately checked it. The 3/64" from before went down to about nil. Maybe the tire on my buddy's bike needs to be run in.

[tcoop]

I had this same tire bounce when I put my new Kendra on they 78. I had a tube in (I think it got twisted and caused a bulge). I took the tire of that rim and put it in a tubules one, it still bounced for a couple of miles but started to smooth out some. I removed the faring and the bounce went away completely. It may have just needed a few more miles of riding.

[Crusty Snippets]

Bounce

My initial thoughts were that the tyre is out of round. I am still thinking that way.
If you want to go fast the tyres and rims must run true for wobble and balance. The steering head must be friction free with no play in it. The front forks must be straight and parallel, the dampening and rebound must work properly, the rear shocks must work properly, the swing arm must be straight and with no play and no friction, and the back wheel must follow the front wheel.
I am thinking 1 / 32 of an inch maximum for rims and tyres, otherwise you get a squeezy feeling at 125 mph and up.

Crusty

[planedick]

Runout

3/16" runnout is a lot and would surely cause a bounce. Also I have found that most balance machines are not accurate and if they add lots of weight there is a real problem. I always supervise the balancing of my tires and when the guy is finished I tell him to remove the wheel and reinstall it 180 degrees from the last and run it again. There has never been a balance machine that didn't require more balancing at that point. I've been working at a professional balance shop for industrial equipment for years and have learned lots about balancing.

[bikerphil]

Yep, I balanced the tire myself and it balanced fine. I will re-check it though. If it was out of balance, I'd think 30 MPH wouldn't be fast enough to cause such a drastic problem. I haven't got a chance to go over and work on the bike yet, hopefully this week. Thanks everyone for your input.

[bikerphil]

Ok, an update: The front tire on this bike is still hopping on smooth road at speeds of 25-40 MPH after 150-200 miles. It's fine at all other speeds, high speed of 90, rides solid. I'm thinking the steering head might be the cause, .

[crazy steve]

Ok, an update: The front tire on this bike is still hopping on smooth road at speeds of 25-40 MPH after 150-200 miles. It's fine at all other speeds, high speed of 90, rides solid. I'm thinking the steering head might be the cause, .

At that low a speed, I would suspect a 'tire' problem rather than a balance problem, although it may be related. I'm assuming you static-balanced the tire. How much weight did it take to balance it? Have you tried rotating the tire 180 on the rim and rebalancing it? I've ran into cast rims that have considerable imbalance. Another thing to try is rather than using weight in one place to balance it, try using two weights 'spread' apart on either side from where you have the current weight. This was the recommended way to apply weights when doing a static balance with the old 'bubble' balancers.

It could be a combination of a 'spot' on the tire along with an issue with the neck bearing causing this too. I doubt that the bearings alone would cause this if the tire were turning true.

Did you ever try a tire/wheel swap to see if the problem stayed with the bike or the tire?

[bikerphil]

Not running that much weight for the balance, not more than usual. Tire was spin balanced on 2 jack stands with a bolt thru. I haven't tried the rim swap yet, no time on the owners part. That would answer a lot of questions. He did say the new forks have helped the handling quite considerably. I personally think his rim is bent. Although the rear tire did require a sh!tload of weight, with those bolts in place of those "rim locks".

[DGXSER]

Tire problem is my guess. If it were the rim it would have shown before now, unless something really bad happened to the rim.

We recently took a long trip in our minivan. Time we got home I was convinced I was looking at new CV joints the way it vibrated and actually shook the steering wheel moving the tires side to side. Felt just like bad CV joints. went away at higher speeds. We put four new tires on it and the problem went away.

[bikerphil]

Yeah, it's strange, it had a heavier 110/90 on it before with a tube and didn't do it.

[cywelchjr]

Yeah, I just changed the front tires on our malibu. The front end was pulling strongly to the side. After putting on the new tires it tracks perfectly now.

Several years ago I have a 76 Vega that I swore had bad wheel bearings, and it too was strangely worn tires. Changed the tires and the grumbling went away. So tires can look just fine and be bad.