Author Topic: Bouncing front end after new tire CB750 K3 (Read 5131 times)

Sigop · « **on:** May 04, 2017, 08:57:18 PM »

Replaced old tires on front and back of bike with stock size Avon Road Riders AM26. Prior riding it had ridden smooth and straight. After putting new tire on now between about 15 and 40 MPH front end hops up and down accelerating and decelerating.

No other change to bike after replacing front tire. New tire was changed and balanced by a shop.

Ideas? Can a new tire be out of round?

BomberMann650 · « **Reply #1 on:** May 04, 2017, 11:26:13 PM »

Probably didn't seat on the rim correctly. Balancing machine would not have noticed that. Take it back to the shop for re-seating.

flatlander · « **Reply #2 on:** May 05, 2017, 12:05:02 AM »

let out the air, roll it around a bit, pump up again. that should smooth it out. most guys in the shops these days don't know any more how to deal with tyres that use inner tubes.
pump it up to the tyre manufacturers spec. the old honda pressure spec is too low for modern tyres.

turboed13b · « **Reply #3 on:** May 05, 2017, 12:20:36 AM »

I bet the rim isnt true. Wrestling the tire off will knock the rim out of round if it hasn't been trued in a while.

Sigop · « **Reply #4 on:** May 05, 2017, 04:00:07 AM »

Thanks guys. Will try all 3 with simplest first. One of the posters on here talked about the front disk grabbing some; would that cause the same symptom?

PeWe · « **Reply #5 on:** May 05, 2017, 05:08:18 AM »

That''s almost standard for me when getting new tire on my bike. Deflate and pump again with much higher pressure until it will seat correctly on rim. +50% pressure no problem.
I had one tire once that had to be ridden on bike on a clean road with almost no air 100-200m, then pump again.
Lubricate the tire where it seat to rim when completely deflated will help, floating soap or similar.

Desert-SOHC · « **Reply #6 on:** May 05, 2017, 11:33:01 AM »

Mine did the same thing and the tire wasn't seated on the rim correctly

Sigop · « **Reply #7 on:** May 06, 2017, 04:19:26 PM »

So I bled it low and refilled up to 40 psi. Still the same bounce--like a pogo stick between 20 and 40, as someone has said before (for some who know what I refer to).

I'm going to go out on a limb and guess that it is not seated properly. See pics. Note the difference in distance from the beading. Think that is the issue? (Just a hassle to take it back to the shop that didn't pay attention.)

evinrude7 · « **Reply #8 on:** May 06, 2017, 06:01:25 PM »

Quote from: PeWe on May 05, 2017, 05:08:18 AM

Lubricate the tire where it seat to rim when completely deflated will help, floating soap or similar.

+1

andy750 · « **Reply #9 on:** May 07, 2017, 09:47:19 AM »

As others have said deflate then reinflate to 80-100psi to get seated correctly. I have done this successfully!

Sigop · « **Reply #10 on:** May 07, 2017, 09:51:27 AM »

Andy750,
Will try that. Did not know tire/tube could take that much inflation. No experience in tire work.
Thanks.

lrutt · « **Reply #11 on:** May 07, 2017, 10:09:58 AM »

Make sure when you put the wheel and axle back together you leave things loose, get it back on the tires then pump the front end to make sure forks aren't binding then tighten up. You can easily get things off just a little which will bind forks and you can get a bouncy front end as a result.

Sigop · « **Reply #12 on:** May 07, 2017, 06:38:24 PM »

lrutt. I'm sorry, I'm not following. Don't mean to be thick. Are you saying the tires would expand so much they would contact the forks, and also that I should first have the axle nut loose before inflating?

Thanks.

Sigop · « **Reply #13 on:** May 14, 2017, 07:23:36 AM »

Update, regrettably. Have had the tire reseated which looks right now. Rebalanced with about 1 ounce less so there was something going on. Replaced all front bearings. Changed and replaced fork oil and changed brake fluid. Not much left but still get a #$%*in' bounce between 30 and 40 mph. Touching the brake smoothes it out. Spikes all ping pretty well when I tap them with screwdriver. What's left? Check tire round with a box or board or something in front while jacked up. If tire good then thinking only thing left is bad rim, which first shop might have dinged when ironing off the first tire.
Happy for additional thoughts but will update as/when I solve this. Hard to enjoy a curve at 40 with a bounce in it. Uh, yeh.

Stev-o · « **Reply #14 on:** May 14, 2017, 07:34:06 AM »

If you are certain there is not an issue with the install of the new tube and tire, this now points to a defective tire.

Although I doubt this as Avon manufactures excellent tires, it is possible.

Sigop · « **Reply #15 on:** May 14, 2017, 12:22:25 PM »

Yes. Will have another shop recheck tube and tire. I agree. A little hard to believe the Avon would be defective.

evinrude7 · « **Reply #16 on:** May 14, 2017, 12:30:27 PM »

sigop, maybe someone has mentioned this but could you have brake drag at the front brake? mine does and it sort of hops a bit around a curve around 40-45 mph.

Sigop · « **Reply #17 on:** May 14, 2017, 12:33:20 PM »

Evinrude7
Didn't you have a similar issue? I have seen that on here but it spins pretty clean and quiet when up on the jack. Not sure how else to test that.

evinrude7 · « **Reply #18 on:** May 14, 2017, 01:15:54 PM »

yeah man mine drags and i feel it around a curve. i think if your's spins free then that's not the issue. just popped into my head as a possibility. i worked in my dad's goodyear tire shop growing up and the only things i can think of tire related is the wheel is not round or the tire is defective. other than that maybe it's a front suspension thing. it didn't happen before you changed the tire but you had the tire off the bike to do that. perhaps something came loose or readjusted during removal/mounting of the wheel. keep us posted.

Bodi · « **Reply #19 on:** May 14, 2017, 01:32:20 PM »

Tires can be defective. Lift the front end and rotate, see if the tread moves in and out as it turns. It should run VERY close to true, a couple of mm might be OK but not much.
If the wheel rim runs true, the tire's bead line is equally spaced from the rim all the way around, and the outside of the tire goes up and down: demand a replacement tire.
If some runout exists check that the bead line to rim distance isn't following the tire runout: if it is, the thing is still not seated properly. It can be a mental hella hard job to fully seat a tubeless tire on our tube-type rims.
If the wheel has been balanced and the weights are strangely large, suspect either incomplete seating, a bad tube (cheap tubes can be way out of balance because the rubber thickness varies too much) or a bad tire. You can't see the bad tube, and it won't cause problems once balanced... but poor seating or a bad tire can give you the radial runout that will cause bouncing.

Stev-o · « **Reply #20 on:** May 14, 2017, 02:37:49 PM »

Good point about the tube, was that new too?

evinrude7 · « **Reply #21 on:** May 14, 2017, 03:48:34 PM »

Quote from: Stev-o on May 14, 2017, 02:37:49 PM

Good point about the tube, was that new too?

sigop do you know if they put the correct size tube in there?

754 · « **Reply #22 on:** May 14, 2017, 04:14:31 PM »

If your rim is bent, you will see it if you spin it. 30thou is acceptable.

Sigop · « **Reply #23 on:** May 15, 2017, 09:59:27 AM »

New tube but not sure of size. If I place a straight line across front of tire when jacked up, I get a variance between highest and lowest spots at middle of tread as it spins of at most 1/8 inch. Is that a significant amount?

Bodi · « **Reply #24 on:** May 15, 2017, 12:23:46 PM »

1/8" = 125 thou... over four times what 754 considers acceptable.

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Author Topic: Bouncing front end after new tire CB750 K3 (Read 5131 times)