Lump in tubular tyre

indyjones

Hi all

I have got a lump on my rear tubular tyre, I think by the valve. Is this anything to worry about please?
I have only taken the bike up and down the road since the rebuild and could not 'feel' it but the ground is pretty rough.

Apparently it's fairly common by the valve? It does shake the bike quite a lot on the stand when spinning the wheel. The tyres are Continental completion 25mm

Thank you

bernithebiker

I take it you mean an uneven ness in the tyre as opposed to a 'blister' in the tread?

If so then, yes, the area around the valve is the hardest part to glue correctly.

You need plenty of glue around the whole area, on both rim and tyre.

Then, when the tubular is on, push down hard on the wheel with the valve at the bottom. This helps seat it and squidge* the glue around.

When inflating up to very high pressure (160psi helps to seat the tyre and straighten it), keep finger pressure on the valve area so the pump does not force the tyre off the rim.

I would take it off and try again.


*sorry for the technical terms

dgunthor

is the valve straight? if not it's a sign the tyre isn;t mounted quite right. as above, try it again

CYCLESPORT1

Photo please

bernithebiker

CYCLESPORT1 wrote:

Photo please

I very much doubt you'd see anything in a photo.

If it's like I think, it's an almost imperceptible raised area where the valve is that is tricky to spot with the naked eye.

Spin the wheel however, or ride it, and the unevenness becomes apparent.

sungod

indyjones wrote:

Hi all

I have got a lump on my rear tubular tyre, I think by the valve. Is this anything to worry about please?
I have only taken the bike up and down the road since the rebuild and could not 'feel' it but the ground is pretty rough.

Apparently it's fairly common by the valve? It does shake the bike quite a lot on the stand when spinning the wheel. The tyres are Continental completion 25mm

Thank you

the latter is simply imbalance, probably weight of the valve stem, with a light bike it only takes a few grams to do this on the stand, on the road it'll be imperceptible

what's the nature of the lump? is it taller? wider? lopsided? etc. is the valve stem straight and 'loose' in the hole or is it hard against one side?

as above maybe mounting was not so good, if the bit around the valve was too slack it'll be uneven when inflated

indyjones

The 'lump' is taller. You can notice it by looking though the brake caliper as you spin the wheel.
I fitted the tyres using Jantex tub tape as this is my first time with tubs. I followed youtube guides doing a bare tyre 100PSI prestrech then seated them centrally on the rim and pulled away the tape.
I think the front tyre also has bump but it's barely noticeable, the rear looks significant.

indyjones

Took it out for the first spin last night and boy was the tubs fast!
I could not 'feel' the lump from riding. Is there any chance it will settle or do I need to pull the tyres off and start again?

Cheers

thegreatdivide

It'll be fine.

sungod

unless it's due to not being in contact with the rim i doubt it'll settle

some rims have a slight chamfer around the valve hole, others are just 'flat', many tubs have a slight bump around the valve and it's also the area where basetape overlaps, so if the tub is mounted without enough tension at the start its easy to get the bump

fwiw i glue mine (veloflex), correct tension at the start of mounting avoids this effect, but mounting with tape as described you will not be able to control tension, perhaps that contributes to the problem

you could try deflating then use fingers (or a smooth+blunt thing) to push this area of the tub into the rim bed *hard* (this way you'll be able to apply much more pressure to the area than when inflated and with you on the bike)

as long as the tub is secure and you cannot feel any iregularity when riding i wouldn't remove it

indyjones

Thanks