Tyre fitting: What to do if the tyre won't fit on the rim

On one of the last warm Friday evenings of the season, my neighbour Annette sat cursing in the courtyard with the dismantled front wheel of her gravel bike in front of her, surrounded by tyre levers and an air pump. Now Annette is someone who actually knows a thing or two about bikes. The fact that she still asked if I wanted to try to force the new tyre I had ordered especially for a long weekend trip onto the rim was rather unusual. It was also my failure: until then, I had been a bit proud of being able to fit practically any tyre without tools. Not a chance! Even with tyre levers, the beast wouldn't fit, there was easily a centimetre missing from the top edge of the rim. To save the honour of both parties, we agreed on a production error, she put the worn tyre back on and returned the new tyre.

A few weeks later, an annoyed MYBIKE reader sent us an email: After a puncture on his bike trip, he had to drive the defective bike 25 kilometres to a workshop. Mending tyres with on-board tools, like in the old days? Not possible, the tyre was too tight. Did we want to write about it? And then I finally got it myself. For a bike trip with an off-road component, I wanted a used gravel tyre instead of the smooth road tyres on my touring bike. It steadfastly refused. So what to do? What advice do the experts on the net and in the real world have for fitting tyres that are too tight?

What you can do with tyres

There is obviously little to do about the tyre itself. Of course, the tyre size must fit, and it must be the size specified in the ETRTO. The "European Tyre and Rim Technical Organisation" specifies the exact diameter. For example, if the tyre says "40-622", it should fit on a rim that has a diameter of 622 millimetres at the point where the tyre bead sits when the tyre is inflated. The ETRTO measurement is much clearer than the previously used measurements in inches. If a new tyre is too tight despite having the correct dimensions, you can mount it on a different rim and leave it inflated overnight to the maximum permissible pressure. Sometimes a new tyre stretches in the process and is then easier to fit on the desired wheel. There is not much more you can do to the tyre. High-quality tyres in particular, which are also suitable for tubeless mounting, must fit tightly in order to remain leak-proof.

A tip for maturing has turned up after all. Online editor Sandra Schuberth succeeded with the help of the warm summer sun.

Sandra Schuberth: "Some time ago, I had one of those monstrosities of a tyre that no trick would help. I finally put it out on the balcony in the blazing summer sun in the hope that it would make the tyre a bit more supple. Once it was properly heated up, the tyres worked - not well yet, but better than before."

Tricks with the rim

There may be more options on the rim. A super-simple trick from the internet is to use the thinnest possible rim tape. I have measured it: The light blue plastic tape closed into a circle in my touring bike is 0.5 millimetres thick, the self-adhesive tubeless tape for my road bike is only 0.1 millimetres. The diameter multiplied by the number pi gives the circumference of a circle. The result of the calculation: the circumference is reduced by just under 2.6 millimetres with thin rim tape. This is unlikely to make much difference in most cases, but there are also said to be rim tapes that are one millimetre thick. Then the exchange would be more relevant.

The second check is for the rim well: is it a tubeless rim? You can tell if it is a tubeless rim by the fact that it has a deep circumferential groove in the rim well, but is completely flat further out where the tyre bead sits. A standard for this type of rim stipulates that the groove must be between 2.6 and 3 millimetres deep. If this groove (the so-called drop centre) is present, it provides considerably more clearance than a thinner rim tape. The rim well is also curved inwards on almost all other rims. This is crucial for tyre mounting. It is therefore always important to push the largest possible part of the tyre bead into the centre of the rim, where the diameter is smallest, so that the tyre can ultimately be balanced over the rim flange at another point.

Tyre fitting

The tip of levering the tyre over the rim near the valve first has never really made sense to me. If you do it this way, you have to push the valve inwards at the end so that the tyre doesn't bulge outwards. However, the "valve last" variant definitely has an advantage with tight-fitting tyres: the tyre bead can be pushed into the centre of the rim over almost the entire circumference of the tyre, i.e. to the lowest point of the rim well. To ensure that the bead remains there during tyre fitting, the finger strength of a nice person or a strap or cable tie can help if necessary.

This can also help to fix the part of the tyre that has already been fitted while you continue working elsewhere. The friction between the tyre and the rim flange is particularly high in the last few centimetres. If necessary, a mounting fluid, a kind of optimised soapy water, can be used here. In principle, rinsing water will also do. After lubrication, however, you will only be able to continue with tyre levers, as it will be too slippery to fit the tyres by hand.

Back to my case: with a combination of various tricks and three tyre levers, I finally managed to force the gravel tyre onto the touring bike rim. But perhaps I should have checked the fitted inner tube first. It had a small hole in it that cried out to be inflated every day - and removing a tyre that is too tight is even more difficult than fitting it ...

I finally got round the problem and filled the inner tube with tubeless milk. Now it is tight for the time being and should hold the air as long as there is tread on the tyre. Then I'll cut the tyre bead with a sharp pair of pliers and throw the unfortunate combination in the bin.

Tubeless for everyone?

Tubeless tyres are actually old hat: practically every car drives without an inner tube. The air pressure presses the tyre against the rim and thus seals the system. The technology has also been widely used on high-end mountain bikes and many gravel bikes for years. However, for physical reasons and due to the more sensitive tyres, sealing milk is also used on bicycles. It seals the transition between tyre and rim and closes small punctures automatically. Tubeless tyres often have advantages on these sports bikes: Tubeless tyres can be ridden with less pressure without risking a puncture, which would damage the inner tube. And less pressure means more grip and more comfort.

Stefan Franken, Product Manager Touring Tyres, SCHWALBE: "Some manufacturers also use the actually advantageous, wide tubeless rims from mountain bikes on touring bikes. This is not a problem if all the dimensions are correct. However, if the unavoidable tolerances of rims and tyres happen to add up on such a fully developed system, it can become a little more difficult to fit."

Advantages and disadvantages of tubeless

But what are the benefits of tubeless for touring cyclists travelling with normal air pressure on reasonably well-maintained cycle routes? The increased puncture resistance against small cuts and punctures speaks in favour of the technology - but these are rare with suitable tyres anyway. The weight saving without a tube is not overwhelming either: a medium-weight tube for average-width tyres weighs around 120 grams, the Sealing milk about 60 to 90 grams per tyre. One argument that particularly appeals to racing cyclists is the reduced rolling resistance. Because a tubeless tyre deforms more easily when rolling than the combination of tyre and tube, a few watts can apparently be saved: Some professional teams at the Tour de France rode tubeless tyres.

On utility bikes, however, practical reasons tend to speak against tubeless. This starts with tyre fitting: tubeless tyres have to be filled with a lot of air immediately to ensure a tight seal. This requires a compressor or a special pump with a pressure container. Filling the sticky sealant and removing a tyre filled in this way can turn into quite a mess. In addition, the sealant must be topped up every few months to ensure a reliable seal in the event of punctures (without punctures, even dried milk will keep a seal). Last but not least, a tubeless tyre also requires more frequent re-inflation than a good butyl tube, and the valve also sticks easily.

Our conclusionTubeless is currently not the right technology for carefree bikes. Tubeless is only a step forward for particularly thorny touring terrain or optimised sports bikes.