Truing wonky tyres (now more concern with why one's come off the rim!)

[wafter]

Today I received some discounted old stock tyres; reduced (with full disclosure) because they're a bit old and wonky.

I've got them on the rims and had had reasonable success in keeping them straight by partially inflating them then trying to align the outer edge of the bead / grip surface with the rim. I'm sure they're perfectly useable as is, but when spinning freely have maybe 1-2mm runout radially and axially; which I'd like to get rid of.

I'm guessing that the longer I leave them inflated on the wheel the less obliging they're likely to be toward and further straightening - so while the iron's hot, does anyone have any tips for squaring the tyre on the rim please?

Ta

 

[Dave Davenport]

Put some talcum powder or soapy water on the tyre wall and inflate them as high as you dare.

 

[Gunk]

Put some talcum powder or soapy water on the tyre wall and inflate them as high as you dare.

This ^^^^

 

[mickle]

This also ^^^^

 

[Drago]

Put them on a lathe.

 

[Pale Rider]

I reckon inflating them rock hard could just as easily push them further out of shape.

If you've wrangled them as much as you can, I don't think there's a lot more you can do.

 

[wafter]

Cheers guys!

Unfortunately as of tonight's test ride things have taken a disconcerting turn

Aware that the tyres weren't quite running true I did a lot of coasting to see if I could feel any lateral movement. At first it appeared fine but then seemed to get worse, accompanied by the back end feeling a bit vague and squishy to the extent that I stopped for a quick check over and to ensure the axle nuts were tight (which they were).

A bit further on I started to hear an intermittent rubbing from the rear so stopped again, to find that one side of the rear tyre had completely unseated from the rim and the tube was visible between the two; the rubbing being the tyre on the mudguard stay

I tried to sort the situation but the tyre cannot be persuaded to stay on the rim and now it looks like the tyre has stretched; with pretty normal, even positioning relative to the rim for most of its circumference but for maybe 15% the entire bead being visible because it's lying outboard of the rim.

Full disclosure; the rims were originally fitted with solid tyres, however I've been led to believe that the section will also take standard tyres. The front tyre looks absolutely fine, although obviously that takes less load so might be less prone to such issues..

So... what do we reckon is the cause? So far I'm thinking one or maybe more:

- Defective tyre (reinforcement compromised, allowing it to stretch circumferentially)
- Defective tyre (existing deformation when fitted causing bead from seating properly - it did take a lot of manipulation during fitting)
- Incorrectly fitted tyre (it wasn't all over the place when fitted.. too much or too little pressure perhaps..?)
- Incompatable rim
- Displaced / misaligned tube
- Rim tape issue

I recall being able to screw the tube's valve nut on quite a bit when fitting the tyre, suggesting that I might have pulled it downward beneath the bead; so perhaps instead of forcing the bead into the rim it might have actually acted to push them apart instead? Regardless I backed the nut right off, pushed the valve / tube in as far as it would comfortably go but this didn't seem to help.

Also I did wonder about an issue with the rim tape as the size I was recommended is (IMO) a bit on the wide side - the channel in the centre of the rim is a shade under 15mm wide while the tape is 20mm; meaning that it rides up the sides of the channel; possibly allowing the tube to roll about its axis and pull the tyre off its bead..?

I'd like to see how easily the tyre comes off the rim completely; if this happens very easily compared to fitting this might suggest it's stretched somenow. That said it's on the back of the bike so a bit of a pain to get the wheel off..

I've never had this issue with any other tyres and am pretty stumped tbh - fap knows what's going on!

Anway, that's all for tonight - I'm hoping I'll wake up to a raft of quick and easy easy fixes, but nothing's ever simple, is it?

 

[Gunk]

Sounds like the tyre is too big for the rim, are you sure they’re the correct size.

 

[wafter]

Sounds like the tyre is too big for the rim, are you sure they’re the correct size.

Thanks - on paper yes they're correct - the rim is unmarked but the solid tyre that came off is marked 26" / 559mm, as are those that went on in replacement..

Another thought - what about compatable rim width? The rims are a little under 19mm wide internally (at their narrowest point, measured across the inner edges of the lip) and the tyres are 35mm. Doesn't seem excessive to me but then I'm used to usually just fitting the same size as whatever comes off..

 

[Pale Rider]

Is the rim - like the solid tyres - some obscure Chinese brand?

It may be it's not properly designed to take clinchers.

The combination of that and your out of shape tyres has led to the problem.

Put another way, you might get away with the rim if you used properly round tyres, or you might get away with the tyres if you used a properly designed rim.

 

[wafter]

Is the rim - like the solid tyres - some obscure Chinese brand?

It may be it's not properly designed to take clinchers.

The combination of that and your out of shape tyres has led to the problem.

Put another way, you might get away with the rim if you used properly round tyres, or you might get away with the tyres if you used a properly designed rim.

Thanks - certainly a possibility. Irritatingly I can't find much in the way of rim cross-sections / measurements / standards to compare my rims to so I'm struggling to confim their suitability for clinchers..

 

[Pale Rider]

Thanks - certainly a possibility. Irritatingly I can't find much in the way of rim cross-sections / measurements / standards to compare my rims to so I'm struggling to confim their suitability for clinchers..

Aye, that would be well beyond my expertise.

You could get a clincher rim and carefully compare the two, side by side.

I would look particularly at where the bead of the tyre contacts the rim.

Might give you a pointer.

By the way, well done for not crashing earlier.

A tyre blowout is a cycling calamity waiting to happen.

 

[wafter]

Aye, that would be well beyond my expertise.

You could get a clincher rim and carefully compare the two, side by side.

I would look particularly at where the bead of the tyre contacts the rim.

Might give you a pointer.

By the way, well done for not crashing earlier.

A tyre blowout is a cycling calamity waiting to happen.

Ta - I happen to have a 700c rim awaiting tomorrow's tyre, but I think it's sufficently different in nominal size to be pretty useless for comparison. Unfortunately I don't have access to any similar 26" rims.

I think I was certainly lucky to avoid a blowout regardless, however as it was it was pretty progressive and obvious (should have noticed sooner really, from the bike's behaviour) and thankfully wasn't on my road bike so speed was unlikely to be an issue

Not had much luck with tyres in the last week; had a blowout on my road bike last weekend but thankfully it was yards from home on the return journey. Likewise this time it was only a 20-ish minute walk; worst-case it would have been about five times that!

 

[Pale Rider]

Isn't there meant to be a hook on the rim for the bead to grip?

If so, that should be the same on any size of rim.

 

[Milkfloat]

I am a bit confused, are you trying to mix up 26” and 700c wheels and tyres and the same bike?