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Wobble in Conti Grand Prix Classics

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Wobble in Conti Grand Prix Classics

Old 08-29-20, 06:44 AM
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MaxDB
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Wobble in Conti Grand Prix Classics

Hi all,

I've been restauring an old bike and one of the last things to get done was buying some good clinchers for it. I stumbled on these Grand Prix Classics that are supposedly really good but I can't seem to have the bead to sit properly straight.

See video I have made of the issues:

I've refit them about 3 times now (completely off and back on), reinflated a dozen times, tried seating the bead better but the front tire seems to keep having this wobble from left to right on the same spot, and the rear some kind of bump which makes me have to put the wheel too far back in the dropouts to clear the front mech hanger from the bump.

Wheels are true, no bump on them without the tires on.

Any suggestions?

Thanks in advance!

Max
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Old 08-29-20, 07:07 AM
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Looks like a defective tire off the assembly line.
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Old 08-29-20, 10:51 AM
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I hand that happen on older Grand Prix tires. Toss them. Buy Conti 4000 IIS or 5000 next time.
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Old 10-10-21, 01:59 PM
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Has anyone experienced a tire developing a wobble like that after considerable time?

A Hutchinson of mine did so recently. It was ~3 years on the bike, only a few 100s of road miles, maybe same equivalent on rollers. I noticed on a flat family ride and didn't worry, but I'm not comfortable with it on a descent.
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Old 10-11-21, 09:46 AM
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Pump it up to 120 to make sure the bead is set.
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Old 10-11-21, 10:12 AM
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Originally Posted by popeye View Post
Pump it up to 120 to make sure the bead is set.
,

…then, if the issue still exists deflate til slightly soft and then rotate the misaligned segment in the direction you want it to go & see if it starts to conform…, the re-inflate to 120 yet again.
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Old 10-11-21, 11:10 AM
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Originally Posted by tgot View Post
Has anyone experienced a tire developing a wobble like that after considerable time?

A Hutchinson of mine did so recently. It was ~3 years on the bike, only a few 100s of road miles, maybe same equivalent on rollers. I noticed on a flat family ride and didn't worry, but I'm not comfortable with it on a descent.
Yes. I think it's broken cords.
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Old 10-11-21, 11:24 AM
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Originally Posted by Carbonfiberboy View Post
Yes. I think it's broken cords.
Time to try something else. Has anyone else noticed that clinchers are harder to set the bead on TLR rims? And the channel is shallower making it harder to mount the tire?
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Old 10-11-21, 05:59 PM
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Originally Posted by popeye View Post
Time to try something else. Has anyone else noticed that clinchers are harder to set the bead on TLR rims? And the channel is shallower making it harder to mount the tire?
Yes. Getting a tire up onto the TLR shelf is tough. With a tubed tire, the tube is likely to sneak under the tire and pop during that process. And some of them do have a shallower well. The solution is pretty simple: don't run tubed clinchers on TLR rims. Use tubeless instead.
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Old 10-11-21, 06:17 PM
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Originally Posted by Carbonfiberboy View Post
Yes. Getting a tire up onto the TLR shelf is tough. With a tubed tire, the tube is likely to sneak under the tire and pop during that process. And some of them do have a shallower well. The solution is pretty simple: don't run tubed clinchers on TLR rims. Use tubeless instead.
TL does not pencil out for us as they do for your circumstances.
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Old 10-11-21, 06:41 PM
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Originally Posted by popeye View Post
TL does not pencil out for us as they do for your circumstances.
Ah, you've seem my post in the other current tire thread: Myths of the road tubeless (or Go back to clinchers)
I'm still ambivalent about this. They say that Orange Sealant will hold at 100 lbs. It's super time consuming just to get my clincher off that shelf if I flat. I have to pry it over with a metal tire iron. I have better luck mounting them with butyl tubes. I use Velo Plugs instead of rim tape to help with mounting. I think two layers of Krapton tape would have worked better.
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Old 10-13-21, 01:44 PM
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Originally Posted by masi61 View Post
,

…then, if the issue still exists deflate til slightly soft and then rotate the misaligned segment in the direction you want it to go & see if it starts to conform…, the re-inflate to 120 yet again.
No change. I'm going to bin it. Thanks for the suggestion.
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Old 10-14-21, 10:11 AM
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Was there anything notable in how the tire rode? If it rides good I'd just keep watching the road in front of me and not get so caught up in the mesmerizing visuals of my tires.
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Old 10-16-21, 01:04 AM
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I've ridden Conti GP Classics with the reddish-brown skinwalls for two or three years on a couple of bikes, no problems. Excellent tires in my experience.

Any time I've had a wobble or irregular looking tire, it was user error -- I was using rim tape that was too wide for the rim. If the rim tape or strip covers the walls of the rims it'll hinder seating the bead. After switching to narrower rim tape, just enough to cover the spoke holes, the tires seated properly, no wobble or bulge.

This might be less a problem with thinner rim tape, such as some tubeless tapes, or rim strips. But cloth tape like Velox is thicker and can hinder seating the bead if the cloth tape is wide enough to cover some or all of the walls of the rim.

Also with older rims be sure there's nothing stuck to the insides of the rims, especially the bead hooks. If obtained some older rims on which the original rim tape or strip deteriorated, leaving gummy and hardened residue that needed to be carefully scraped out. Otherwise it could interfere with seating the tire properly. I had one 20-25 year old wheelset with the original plastic rim tape or strip that deteriorated so much it seemed to have melted and hardened onto the rim. I had to use a combination of hard plastic scrapers and aluminum picks to laboriously remove the material. Took a couple of hours while sorta watching a movie.

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Old 10-17-21, 07:51 AM
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Tire isnt seated properly. A little talcum powder makes tires, tubes less "sticky" and tires seat easier.
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