confused by measurements tyres and tubes

[beatmeoutame]

and replacing the rims is not an easy task (for a novice) and would cost more than buying new wheels

yea thanks for everyones advice. I just went back into the garage and tried blowing the tyre up a few times and squeezing the tyre making sure it was seated etc. managed to get it inflated to 80 psi without any visible signs of it coming off the rim, tried riding it around a little and seems fine.

Bit worried though as last occasion it came off just after I had been cycling quite fast on a main road and had to stop sharply to avoid the tube bursting. Bit of a random time for it to come off but hey

 

[swee'pea99]

Sounds to me like you've done the right thing.

Fact is, tyres - even ones with identical measurements - vary. Some are an absolute swine to wrestle on (and require levers, inviting pinch-punctures), others 'the same size' go on nice and easy. Sounds to me like you've just got one of the slightly looser ones. My advice to you would be to do pretty much like what it sounds like you've done - take it up to quite a low pressure - 10psi or something - then look at it quite carefully to see that it's sitting evenly all the way round, shifting it with your thumbs if necessary to make it so (you may need to let out a little more pressure to allow you to manipulate it like this). Once you're confident that it's all sitting evenly, take it up to, say, 30 psi, and look again. Still even? Then go up to 90.

Then ride it round the park for half an hour, so if it does pop, you're not going under a bus. If it's going to pop, it'll probably (not definitely, but probably) do it within half an hour. If it doesn't, you're probably ok.  (Oh by the way, when I say 'pop', I don't mean burst, I mean come off the rim. It's not going to burst whatever you do.)

 

[beatmeoutame]

thanks swee pea 99

 

[ian turner]

thanks swee pea 99

Still sounds like someone replaced the original rims with ones for a hybrid (my giant cypress has 622-19s with 700x40 tyres) then
stuck road tyres on them (my secteur has 622-14s with 700x25 tyres) in some warped attempt to make it multi purpose.
Nip down a local bike shop (not halfords) and see what they think.

 

[HLaB]

don't listen to HLaB - you would need to get narrower tyres, but I still think your 700x25 will fit.

I thought the OP had 18mm rims and going by Sheldon a tyre between 26 and 38 will be optimum, excuse me if I have read it wrong. I'm sure Sheldon said somewhere that his recommendations are conservative, so I agree the OP will get away with a 25mm. Surely a new tyre is cheaper than a new rim if the OP is having bother

 

[MacB]

If these are old steel rims aren't they worth replacing?

The ERTO system is actually pretty good but there does seem to be a peverse desire to stick to, and mix with, older measurements and descriptors. I know I got really confused at first because of this, basically:-

XXX-XX indicates diameter and width, when applied to a rim it's the internal width, when applied to a tyre it's the widest point. So, once you've identified the rim then the tyre you choose should match for diameter, ie 622 rim needs 622 tyre, but the width of tyre is partly judgement. Sheldons guidelines are very good and a lot of the rim manufacturers sites give permissable tyre sizes for each rim. You will see variations in the recommendations for equal rim ERTOs, for example:-

Mavic Open Pro and Open Sport are both 622-15 rims, but the first is rated for 19 to 28mm tyres and the second 19 to 32mm. This is to do with the sidewall strength, the OP is a lighter rim so squeezing a larger tyre in will apply more pressure sideways.

Mavic A719 and Rigida Sputnik are both 622-19 rims but the first is rated 28 to 47mm and the second 28 to 62mm, again the sputnik is a heavier, stronger sidewalled, rim.

MTB rims 559-xx can often cope with wider tyre to rim width ratios as the rims themselves are stronger.

As I say Sheldons guidelines are a good starting point, there's also a lot of info on the CTC pages re this subject. Obviously there are also limitations around what will physically fit in your frame and still allow your brakes to work.

 

[beatmeoutame]

Thanks for the feedback it has been helpful
im gonna upload some photos of my bike in the relevant place

thanks again