Tyre with a stubborn 'lollop'

[Transporterman]

Hi everyone,

I was a member a while back but my email provider (Orange) closed so now I can't receive a password reminder with my new address.

Anyway I was just wondering if anyone can help me with a rat bike I bought cheap with tyre problem. It is an old mountain bike which had a rear tyre with a huge 'lollop' in the rear wheel as you rode. At speed it was almost like riding a horse! It looked like the tyre was misshaped perhaps or fitted badly. Anyway, I found a big split in the side wall so I decided to replace it with a new one (cheap from Decathlon in Spain) and it was exactly the same!

When I took it off again I could see that rather than the usual not seated down fully problem, it was the opposite and sinking too far into the rim in one place. I could see that the datum line or whatever it's called has disappeared below the rim edge in a six inch section. I checked the rim by spinning without the tyre and it's fine. I took it off numerous times and tried pull it back up but it seems it always wants to sink into the rim whatever I do. The rim tape isn't perfect but surely rim tape can't be there to hold the tyre up can it?

The original tyre was a 26" and I replaced with the same and it seems to have the same fault. Apologies for the long post!

 

[fossyant]

Talc the inside of the tyre, and also the tube. This helps them seat properly. You could also use soapy water. I prefer talc.

 

[raleighnut]

You could try partially inflating the tyre then using your thumbs to coax the recalcitrant bead up onto the shoulder, BTW I'd talc it too.

 

[Ming the Merciless]

Can you post a photo of the bit of rim it sinks into.

 

[Transporterman]

Thank you everyone. I tried lowering the pressure and pulling and working the tyre with my hands and even bouncing it on the ground in order to even up the sunken section but nothing worked. I would understand if the problem was that the tyre was high in one point because something was stopping it seating but this seems to be the opposite in that the tyre sinks too far into the rim in one place. I'm back in England now but I did take some phone pics of the new tyre at least so I will find them and post them up tomorrow.

 

[gbb]

Tyre size fitted ? 26x ? Is it compatible with the rim ?

 

[Globalti]

New tyres are sticky so they need talc on the beads as a dry lubricant to help them settle correctly on the rim.

 

[Transporterman]

Tyre size fitted ? 26x ? Is it compatible with the rim ?

I wish I knew! The original tyre was was 26-1.95 (and that had the same lollop) but I could only get a 26-2.0 I did wonder if neither tyre was correct for the rim and that was why the fault was the same with both but how to tell? I'll post the pics later and hopefully someone will spot something.

 

[Transporterman]

Unfortunately for some reason I don't have a pic of the actual sunken section of the tyre. But here is the bike and the new tyre. I have no idea what the bike is, it is just a cheap wreck to save me hiring two bikes for couple of months.

In the tyre pic the line height looks good but there is a section where the line is so low it goes out of sight.
Could talc really fix it when the problem isn't that the tyre won't go into the rim but rather that it goes in too far? (in one place).

Any comments would be welcome!

 

[confusedcyclist]

Yes! The tyre bead won't lift out when you inflate your tube, friction and uneven distribution of the tyre bead between the rim and tyre is to blame. I've had better luck with soapy water. One or two more attempts to seat the tyre if it's gone wrong should be all it takes. Make sure to fully remove the tyre and wipe down the bead with the soapy water, seat one side of the tyre bead in the rim, partially inflate the inner tube, just enough that it holds shape, insert the valve stem into the rim, carefully insert the rest of the tube into the tyre, then carefully and evenly seat the other bead in and inflate.

 

[Transporterman]

Thanks for that. I used neat washing up liquid and but come to think of it, I only coated the side I was going to have to press over the rim. I'd always thought the reason for using soap was just to ease the tyre to go over the rim (without tyre levers if possible). It does seem odd that whoever put the original tyre on had the same problem though.

 

[raleighnut]

Thanks for that. I used neat washing up liquid and but come to think of it, I only coated the side I was going to have to press over the rim. I'd always thought the reason for using soap was just to ease the tyre to go over the rim (without tyre levers if possible). It does seem odd that whoever put the original tyre on had the same problem though.

It could be a slightly 'big' rim but not by much, I've had better results with Talc but you need a fair bit of it, all over the tube (I've got a plastic bag with half a tin of Talc that I chuck the tube in and give it a good shake)

A VAR tyre lever might help too.

 

[Transporterman]

I think an oversized rim could be it. It's the only thing that really fits. I do wonder if it's even fixable. I had even removed the new tyre and pumped it up slowly whilst holding the low part of the tyre up to no avail.

As my previous incarnation I was 'Podge' and got some great help with another rat bike I have in the Canaries (I don't have a girl in every port but a rat instead!) I bought a new rear wheel dirt cheap and together with a new chain and dérailleur it transformed my much loved old 21 year old Sarecen Hardtrax. https://www.cyclechat.net/threads/where-to-buy-rear-derailleur-for-saracen-hardtrax.195821/ so I might do a new rim for this old rat.

Thanks again to everyone and also to Pat 5MPH who offered to resurrect and merge the two accounts. I have left it for now to save confusion.