Egg-shaped Contis

opus25

Hi all,

I've just picked up some GP4000s II tyres and, no matter how much I try to massage the tyre, at various pressures, I just can't seem to get the tyre to fit snugly all the way around - there's always a small 'dip' around 20cm (ish) in circumference length where the tyre doesn't rise up to clinch the rim regardless of my efforts to 'pull' it up. My other tyres, Rubino Pro Slicks, are easy to push/pull back into shape if I change tubes and get an uneven fitting.

I've tried the same two sets of tyres on other wheels (Racing 7s) and get the same thing: egg-shaped Contis but perfectly round Rubinos. Maybe the Contis are a touch smaller or need stretching out a touch (?).

I'm putting it down to me being a bit rubbish so am hoping some wise old head can help.

mercia_man

You could try smearing the beads and rim with some washing up liquid and water as a lubricant and then try pumping up to a very high pressure of say 130 plus. Bouncing the inflated tyre on the ground can also help.

Bozman

I had a similar problem on Racing 7s and I tried everything I could think of but they just wouldn't have it, I swapped tyres, used talc etc but it wouldn't have it so I had a word with a quality mechanic and...
The answer was to put more pressure in the tyre and it should pop on to the rim and it'll sit perfectly, just remember to lower the pressure before you use the bike but you really have to put some pressure in the tube for it to happen.

alihisgreat

New tyres give me nightmares - especially conti GP4000s. There is a trick to getting them on, although really tight ones will still be awful.

if you let the air out of the tube you can push the bead down into the center of the rim on the side opposite to the area you're struggling with - this should give you a bit more length to work with.

You can also 'roll' the tyre on, using the palm of your hand/base of fingers - either pushing from under or pulling over the top.

If all else fails then you might have to use a tyre lever, and even then it might need a fair bit of force.

Bar Shaker

Mine weren't sitting right on first install until I got about 80psi in them. Then they slid into place. I suspect that the rubber is so grippy that it doesn't want to slid into the rim bead voids. It really is a soft grippy rubber to touch.

I have since deflated and re-inflated to check if this was a one off and they need a bit of pressure before settling into shape.

If they are really stubborn, some soapy water is the answer.

neilo23

Had this last week with new Conti 4 Seasons. Pumped 'em hard, let the air out again and massaged them a bit. Never had it before.

littledove44

Mercia Man wrote:

You could try smearing the beads and rim with some washing up liquid and water as a lubricant and then try pumping up to a very high pressure of say 130 plus. Bouncing the inflated tyre on the ground can also help.

That worked for me.

opus25

Thanks for the tips - I will give them another try later. They weren't playing ball at 90 PSI so I'll give them more and try washing up liquid if needed.

EDIT: an extra 40 PSI did the trick. Was about to reach for the washing up liquid before they both went "dink". No more eggs - thank you!