Topic: Max run out for rear tire?

[1976cb750f836]

I'm back chasing my bounce. I have the rear wheel off on stand. My tire run out is almost 1/8 in. What's allowable run out? Wheel is dead on. No run out, or side run out. The tire rings look equal spaced all way round. Run out in center of tire.

[TwoTired]

That's fine if you don't mind a bit of wiggle at certain speeds.

If rim is true and tire tread is not, then either a defective tire (unlikely with top brands), or the tire just isn't seated on the rim properly.

Cheers,

[1976cb750f836]

I'm changing tires anyway, just thought I'd measure Run out on old tire. Before change.

[maxheadflow]

I wouldn't allow over 0.050" runout.  When you remove the tire, check the wheel to make sure it's definitely less than 0.050.  Bike in the pic looks to have comstar wheels.  Check the rivets where the spokes meet the rims.  If you are getting a gray/black dust, they are likely coming loose.  If they are wire spoke, you should be able to ture to less than 0.020".

[1976cb750f836]

Wheel is a NOS comstar I bought 20 years ago at a local Honda dealer,  he had it a while and cut me a deal . As best I can tell with a steel rod and my eyes on stand theirs almost 0 Run out. I'm check again when dissassembeled. I've always ran tubes, but am thinking bout trying tubeless. These are tubeless wheels aren't they?
May have found some of my bounce problem, lower shock bolts were smaller than the swing bushing ID hole by a tad over 1mm, I've tapped the hagon and installed 10mm bolts, no play now. And my swingarm was so tight, I could not move it by hand with shocks off, I've set it correctly now also.

[maxheadflow]

Mag wheels should be able to go tubeless but I really don't know about the early stuff.   Mags started about the same time I was retiring from being a mechanic.   IIRC the early comstar stuff still had tubes. I don't remember when they switched over.  I would look at the hole for the valve stem in the rim.   Will it take a tubeless tire valve? I guess you can get metal stems that might fit. 

[TwoTired]

The early Honda comstars were tube type, as they had no machined tire bead seat feature, which locks the bead in place on a true tubeless rim.  That's why they pop during installation on a true tubeless rim.   While you can put a sealed stem in the tube type and allow the pressure to hold the bead in place, it is not considered to be very secure or safe.  Low pressure and side loads can release the bead seal and then you have a sudden loss of all pressure.  Slow leak turns into a blow out while under stress.

Not guaranteed to happen, of course, but possible.  Just how much of a rebel are you to accept increased unnecessary risk?

Decide for yourself if the risk is worth not adding a tube that it was designed to have.  It's just your bones and skin, after all. 

Cheers,

[rotortiller]

My tire run out is almost 1/8 in.

Tires have run-out so check the rim. The rim tolerance is generous at about a couple mm, but less is best.

[maxheadflow]

Of course it's a good idea to check the bead seat.  The line on the tire should be even around the edge of the rim.  Common issue is getting some of the tube under the bead. Not sure how long it would last tho..

[RAFster122s]

Comstars are marked to indicate if they are tubeless. My 78 cx500 has them, first year for ComStar in US if not world, and they are tubeless.

[1976cb750f836]

My wheel has, J18 x 2.15   278   DOT   , DID   JAPAN. Around the rim on one side where the spokes are riveted. Says nothing bout tubeless! And no bead lock raised section inside? So I better scratch the tubeless idea? 
Ps- every time I remove one of these wheels, I think damn these things are HEAVY! 

[TwoTired]

Of course it's a good idea to check the bead seat.  The line on the tire should be even around the edge of the rim.  Common issue is getting some of the tube under the bead. Not sure how long it would last tho..

You do know that is not the bead lock, right.  Tubeless rims have a raised ridge inside to keep the tire bead from moving inward. 

None of my Cb750 F comstar rims are tubeless type.

Cheers,

[HondaMan]

I'm back chasing my bounce. I have the rear wheel off on stand. My tire run out is almost 1/8 in. What's allowable run out? Wheel is dead on. No run out, or side run out. The tire rings look equal spaced all way round. Run out in center of tire.

Runout should be no more than 0.5mm, or else keep the speed below 55 MPH. (Circa 1970.)

[1976cb750f836]

It's all apart, the wheel has just under .05mm Run out at the spot where the tire had bout 1/8in. Could I buff some of the rubber off the bead where it's high? Could I file or sand some of the alum off the bead rim at the high area? The high part of the rim is about 14in in length. Or I might have access to a lathe, could the inside of the rim be trued? I'd like to do something while it's apart.
Or anyone got other ideas?

[RAFster122s]

Time for a new wheel. Tough to find a lathe big enough enough to turn a wheel.

[1976cb750f836]

Time for a new wheel. Tough to find a lathe big enough enough to turn a wheel.

No,no,no,  gotta try some hillbilly engerning first.  I got almost no Run out now less than .25mm.  Hears what I did. I cleaned inner wheel rim where bead goes with bench grinder wire wheel, both sides. I then marked the high spot, bout 12in in length, both sides. I then took off a few thousands with a bench grinder dingel berry sander, it's coarser than wire wheel.
Now to the tire. The lip that goes on the rim bead to center the tire had some rubber flash from moulding. I had marked the tire high side before teardown. I used 3 different rasp, files to attack the flash, and removed a few thousands hear also. Assembled tire on rim in the same place it was. To my amazement, almost 0 Run out. Finger nail thickness maybe.
Not the funest job I've ever done, but it seems to have worked. Filing and sand buffing the tire edge where it centers on the rim was the hardest part. When I buy another tire, I'll try to true the rim some more, I don't like cutting on tires.

[maxheadflow]

It's not a good idea to remove anything from the inner shoulder where the tire bead seats.  The tire needs to be a tight fit there or it can slip on the rim.

[1976cb750f836]

Only removed a few thousands, and the ridges on the side should keep tire from slip. If this helps get rid of the bounce I've benn chasing, I'll be happy .

[RAFster122s]

Did the rim have the internal ribs to prevent the bead from moving towards the center of the wheel?
I would not have done what you did, in my book it was a risk for something bad to happen as a result I would not want to take... The price of another wheel is not worth the potential for an accident or worse if things go pear shaped from the " modifications" you made.

[754]

 Most steel rims have noting to keep bead from moving over , yet people run them with tubes.
 Are you guys worrying about hitting something hard enough to break the bead to unseat the tire, and then expect to keep riding ? or are you worried about an impact , momentarily moving the bead enough to lose most of your air pressure.

  Having a blowout on a steel tubes rim  usually results  in bead unseating, and tire moving around.

[RAFster122s]

He has Comstars right? If he runs them tubeless then unseating the bead is more catastrophic.
Most ComStar wheels were tubeless.

[maxheadflow]

Only removed a few thousands, and the ridges on the side should keep tire from slip. If this helps get rid of the bounce I've benn chasing, I'll be happy .

Removing a few thou from inside the rim will only make a few thou difference on the runout of the outside of the tire. If you are out 1/8 inch it won't make any difference.  Reseating the bead might help.  Cleaning a pile of leftover crap off the bead should help also.

[1976cb750f836]

Did the rim have the internal ribs to prevent the bead from moving towards the center of the wheel?
I would not have done what you did, in my book it was a risk for something bad to happen as a result I would not want to take... The price of another wheel is not worth the potential for an accident or worse if things go pear shaped from the " modifications" you made.

No internal ribs. I did wire wheel the inside until I saw clean alum all way round. I might have taken off 15-20 thousands on the high side . It still shows slightly high on that section( the high is centered over a spoke). I am running tubes. I may have taken closer to 50 thousands off the flash on the tire. Something worked, Run out is minimal now. I appreciate the worry about safety. But I can't see anything I've done to be a safety issue. The problem might have benn trash or tiny piece of tube in the bead area. I think it was out of round, tire and wheel stack up, high side of wheel lined up with high side of tire. At about a quarter of a MM now, it should be in spec.

[1976cb750f836]

Short 2mile test late yesterday, before dark. Now I live on a painted county road, not as smooth as a state road, so it's hard to tell if it's all gone. But it rides better than before, no extra bounce when in the old 45mph bounce zone. Hope to ride more today, and I think I forgot to set psi in rear tire after I blew it up the second time to seat tire, around 40psi, ?
I'll set today before test ride. I'll probably start next season with a new rear tire anyway, I really like the Pirelli rout I put on front, have never benn satisfied with this shinko ride or look. Before spring I can c a Pirelli on rear to match.
Ps-recomended safe minimal air pressure in rear, 180lb solo rider?