Topic: Front end vibration

[Scott S]

 1971 CB500

 I'm experiencing an odd front end vibration. Not always there, though I can't remember off the top of my head at what speed it comes and goes. This is an UP/DOWN oscillation or vibration, not a side to side "tank slapper". I can loosen my grip or even take my hands off the bars and the bike tracks straight ... but the suspension vibrates up and down.

 - New tires. IRC GS-11's in 3.25-19 and 4.00-18. The shop that mounted them is always good about telling me when they find out of round rims, tires, etc. They didn't mention anything and the tires didn't take an excessive amount of weights to balance.

 - Rebuilt front forks with new seals and fresh oil. Stock rear shocks.

 - Chain is adjusted and rear wheel aligned using a tape measure to double check.

 - I did not change the steering bearings or wheel bearings. The wheel bearings felt fine to me and the bike only has 12K miles on it ,BUT .... it had a Vetter fairing on it when I got it and sat for about 25 years.

 I mention that because I'm wondering if the wheel bearings have a flat spot in them from sitting? Especially the front, with all the extra weight on the front end. I'll probably change wheel bearings this winter, but I was wondering if you had any other ideas?

[scottly]

I doubt the bearings have a flat spot from sitting. Did the problem start after replacing the tires?

[Tracksnblades1]

Did your new tire beads center completely around the rim…

I’ve had trouble with the tubeless tire beads fully seating on the spoked rims. Requiring some lube to get them seated without over pressurizing the new tire…

Is your front tire dribbling at a certain speed before settling down at a faster speed ?

[Scott S]

I doubt the bearings have a flat spot from sitting. Did the problem start after replacing the tires?

 Well, yes ... but the bike was a non-runner with dry rotted tires when I got it.

[BenelliSEI]

Did your new tire beads center completely around the rim…

I’ve had trouble with the tubeless tire beads fully seating on the spoked rims. Requiring some lube to get them seated without over pressurizing the new tire…

Is your front tire dribbling at a certain speed before settling down at a faster speed ?

+1 to this. Look closely at the markings on the tire. Check the sidewalls are equally buried on both sides. The slightest outage creates what you describe. Break the bead, lubricate and reseat until it’s perfectly round.

[scottly]

  Try putting the bike on the centerstand with the front wheel off the ground and spin it to see if it has any wobble or bobble. Also, you might try removing the caliper, spin the wheel, and mark the spot at the bottom with chalk after it coasts to a stop, then spin it again and see if it stops at the same place. (checking balance) While you're at it, take a small wrench and "ring" the spokes to check the tension; a loose spoke will ring a lower sound than a tighter one, and if it's really loose it won't ring at all. Lastly, have you checked the air pressure?

[Scott S]

Did your new tire beads center completely around the rim…

I’ve had trouble with the tubeless tire beads fully seating on the spoked rims. Requiring some lube to get them seated without over pressurizing the new tire…

Is your front tire dribbling at a certain speed before settling down at a faster speed ?

 These are not tubeless tires. I can see that the raised "rib" is a little further from the rim on the front, at the valve stem. Pics don't look like much, but the gap from the rib to the rim is about 7mm at the valve stem side. If I check it 180 degrees around, on the other side of the rim, it's about 4 or 5 mm. That's also the area where the weights are. It also seems to "bulge" a little more on the LH side of the tire/rim than the RH side.

 Rear seems to be even all the way around.

[Scott S]

 I'll have to wait until I get a helper to spin the front tire. I'll also check the spokes.
 It looks like it may be something with the bead seating ... see my previous post.

[BenelliSEI]

Scott….. That is definitely not centred. Deflate, break the bead. Spray a bit of windex where it’s less popped out an reinflate. It needs to be even all around. .

[scottly]

It looks like it may be something with the bead seating ... see my previous post.

Yeah, that may be the problem.

[Scott S]

Is your front tire dribbling at a certain speed before settling down at a faster speed ?

 Yes, but I can't remember exactly what speed right now.

[Scott S]

Scott….. That is definitely not centred. Deflate, break the bead. Spray a bit of windex where it’s less popped out an reinflate. It needs to be even all around. .

 It's actually MORE popped out right there by the stem. The RH side is pretty even all the way around. The LH side has that "bulge" near the stem.

 The rear wheel seems seated evenly side to side, though I do detect the slightest drag of the tire on the garage floor when the area where the stem is comes around.

 Front spokes all ring nicely and sound the same.

 I'll run it up to the shop that mounted them and have them take a look.

 What tire pressures do you recommend fot the IRC tires?

[Mark1976]

   It's doesn't seem to be seated evenly, you may have a bit of the tube pinched in there, I've had a very similar experience myself, mine was the tube. Broke it down, re lubed the p!$$ out if it and re inflated it, all was fine.

[Tracksnblades1]

Is your front tire dribbling at a certain speed before settling down at a faster speed ?

 Yes, but I can't remember exactly what speed right now.

Your pictures are what I was referring to. Seems to be more of an issue for me since tires went to the metric size.

My front tires seem to be the issue. The newer 21” front tires on dirt bike seem very troublesome to center. Tube talc powder just doesn’t do it anymore…

Glad you may have found your problem..  that front wheel dribble is the tell tale out of round….

[Scott S]

 Thanks everybody. If I attempt this myself, I'm guessing it's best done off the bike?

[Deltarider]

A tip in general. When you're to replace a tyre, first remove eventual rust from the rim's inside. Once a 'kwikfitter' would not put a new tyre on, not before I had removed the rust crust with a steelbrush...

[BenelliSEI]

Thanks everybody. If I attempt this myself, I'm guessing it's best done off the bike?

You can do it on the bike. On the centre stand with a scissors Jack under the oil filter works for me. Just enough so you can spin the front tire. Pop the bead off with a tire iron (after removing the valve and ensure the air is all out). Spray soapy water (I just use Windex) and inflate again. Go to the max pressure stamped on the tire. If it doesn’t look evenly seated, do it again…. Can be frustrating, but it will eventually go where it belongs.

[BenelliSEI]

Got it sorted?

[Tracksnblades1]

😇

[grcamna2]

A tip in general. When you're to replace a tyre, first remove eventual rust from the rim's inside. Once a 'kwikfitter' would not put a new tyre on, not before I had removed the rust crust with a steelbrush...

This.

 I've even used a large,sharp-edge screwdriver-type tool to scrape/chip-away at the crusty/rust build-up in the bead areas of an old rim to allow the tire beads full depth all the way around;then finished-up with a vigorous wire brushing.

When an old rim(42 yrs.)has a build-up of rust along where the tire beads seat,it can cause that problem;either that or you have a dent in your rim from hitting a sharp hole,etc. in the road with a tire under-inflated from the PO's past.

I would remove the tire and check for a dent in the rim first;put the wheel in a truing stand to detect if it has a flat spot in the rim,then after you've determined that,scrape/chip away all the rust out of the tire bead areas.  I use Murphy's tire bead sealant when installing new tires.

[Scott S]

Got it sorted?

 Nah, haven't messed with it at all yet. I'll try to pull the wheel this week.

[Scott S]

 Got everything ready today and the bike is just a bit too wobbly when I start jacking it up. My wife is out of town for a couple of days, so I have to wait for help. I'm about two minutes and half an inch of clearance from getting the wheel out!

[BenelliSEI]

Scott……. If you can see the area that is stuck too far in on the rim, point it forward. Let the air out, break the bead in that spot. Spay some dish sop and water in there and inflate! No real need to take it off if it pops out…….

[Tracksnblades1]

Scott……. If you can see the area that is stuck too far in on the rim, point it forward. Let the air out, break the bead in that spot. Spay some dish sop and water in there and inflate! No real need to take it off if it pops out…….

And a tire sunning in the hot sun is a lot more pliable than a cold one…

[Scott S]

Scott……. If you can see the area that is stuck too far in on the rim, point it forward. Let the air out, break the bead in that spot. Spay some dish sop and water in there and inflate! No real need to take it off if it pops out…….

 The area that's different isn't too far IN, it's further OUT than the rest of that bead that runs around the tire. And it's in the area of the valve stem. And 180 across from the weights on the tire.