Tires are divided into many categories which include mountain bike tires, road bike tires, gravel bike tires, and conventional bike tires, and all of them stretch some may stretch more than others, and sometimes if you don’t take care of your tires much they might stretch to an extent of not fitting on the rim properly
The direct answer would be that.
Tires do stretch even if they are new or old they stretch naturally but you can stretch the tires more or less with your own interventions as well with or without you knowing like keeping the tires at higher pressures would stretch them too much if you keep the tire pressure too high for a longer period of time (2 or 3 days).
conventional tires do stretch but road and mountain bike tires would not stretch too much because these are tubeless and tubeless tires have been made on the basis of their rim beads and when we talk about their rims then their rims have also many categories two of them, are hookless and hooked rims, all these small and deep things would matter a lot for tires stretching, tire comfortability and tire seating on the rim beads.
tubeless tires are made in such a way that they would not stretch too much because that would make the tire come off the rim or blow out on trails.
the material contains carcass, nylon, and cloth. these materials are different depending on the quality of tires and according to the price range of tires, those tires which are too cheap have cheap material used in their manufacturing but those tires which are expensive and are used for aggressive and rough terrains and these are quality brands with higher price ranges have better material and these would not cause stretching, their sidewalls are strong and hard and the threads and cords(a.k.a TPI) of these tires would hold the tire tightly in summer and winters.
Tire Streching depends on the tire’s bead as well :
beads of tire contain two long metal wires which would not allow the internal rubber or the tire to cause stretching from bead places but a carcass, cloth fiber, nylon, and threads of tires would cause a little bit of stretching especially when the tires become old after running long mileages. including the material of the tire, stretches also depends on the position and location of the tire on rim beads and the comfortability of the tires on the rims, if the tires are properly seated on beads then after a long time tires width of tires remain same.
Using lubes or oils on the tire beads in wrong way can make the tires stretch as well :
Stretching also depends on the bleeding of the tire beads, if these are lubed in a higher or lesser amount, then it will also distract from their actual rim bead position, and in this these tires will continuously start slipping left to right from their actual positions, as a result, the material of the tire is badly affected and the tire would not be able to move in a comfortable condition.
Oiling the tire beads is not a very good idea Always remember to use something that can easily and quickly dry off otherwise the tire will not properly sit on the bead and may come off when to run them that can be potentially really dangerous.
More important tires are different in the carcass, their ar half tire brands have a thick layer of the carcass, and the other brands have thin layers of the carcass, and the rubber used in the manufacturing of the carcass layer of tires also has a noticeable differences.
A stretching tire in a sense is not always a bad tire it’s when the tire starts becoming brittle and hard that it becomes a matter of more worry and becomes useless, but remember that stretching to an extent is okay if the tire is stretching unusually it can quickly become useless as well.
I also did an article on
New tires do stretch here’s WHY :
Newly branded tires usually come in folded state and when these are installed on rims They are really hard to get on the rim and they do need some stretching and the best way to do so is to
Leave the tires for the first 24 hours pumped up to high pressure, and then leave them inflated and remember not to ride them in this state just leave them be as they are.
new tires when left on high pressure for 24 hours will start stretching from 1mm to 3mm due to the higher internal pressure which is perfectly fine and you don’t need to worry about such behaviour.
tire pressure is maintained at 30 to 35 psi for mountain biking, same happens for road biking gravel biking and other bikes the take away here is to not blow the tires to the maximum pressure they can hold but pump them high enough that you dont see any wrinkles in the tire and it seats properly on the rim.
The internal layers are stiff and will shrink in the beginning when these are installed on bike wheels, so inflating at a higher pressure for new branded tires is better for the very first time.
Why Tubeless Tires Do Not Stretch :
Tubeless tires are manufactured in such a way that tire beads have long thin metal and steel wires on both left and right sides of the tire.
even if the tire is old and worn, still, their beads would not cause stretching but the sidewalls and the inner layers of the rubber material of the tire which are expanded all over the tire cause stretching.
and the tires internal space cause stretching just because of the carcass and casings due to which the inner diameter and width of the tire would cause stretching of 1mm to 2.5mm in normal conditions when the tires have been run for long mileages, if you are seeing stretching more than this than there could be some problem with the tires material or it’s just too old.
And the internal cords (Threads under the casing known as TPI,threads per inch) which are hidden within the tires do not cause stretching because these are totally supporting the tightness of the tubeless tires but when the cords became visible on the surface of the tires then these would not be able to keep and maintain the tightness of the tires.
I did another solid article on higher and lower tpi if you had like to read more around this topic What is better a Higher TPI or a lower TPI for mountain bike Tires
Stretching Of Tires Also Affect The Size Of Tire :
When tires are stretched due to higher air pressure or if the tire has been run for longer mileages and now is old, then on normal basis tires make a difference in their sizes and width, which is simple if you have bought 2.2″ tire size width then it will go to 2.3″ size and if you have 2.4″ tire size then it tends to increase and it stretches to increase a point in its size and the new tire size would be 2.5″ which is pretty normal. the difference in a point in tire sizes is usually common if inflated at high pressures before riding.
If you have troubles seating the tires here’s an easy to follow guide Mountain Bike Tire bead(types,Bead Seating Tricks,Bead leak)
and for bead How do you break the bead or unseat the tire on mountain bikes Easy methods
The inner layers of tires sometimes tend to increase in their width and sometimes the casing layer of the tires starts growing and increasing its width from its usual size, all these results you would see at higher air pressures.
continuous change In Tire Pressures can Cause tire Stretching :
When you are continuously changing tire pressure after every ride and you are riding two to three times a week and after the first ride you have decreased the pressure from the recommended pressure while after the second ride you have increased the tire pressure from the past pressure, this changing would also affect the internal layers of the tires.
But too much frequent tire pressure changing can lead to unusual stretching of the tires so make sure that you keep that in mind, a little higher pressure in this case would be better than little lower pressure.
Once you figure out which pressure you think suits you best make sure you stick to it and do not make drastic changes to tire pressure because it may not show effects right away but as time passes the tire will strat showing problems like bubbling on the side walls and streching which is really not a good thing.
Single Ply And Double Ply Tire streching :
There are two categories of tire casings, singly ply tire casings and double ply tire casings, stretching level is also different for both kinds of tires due to the difference in casings and layers and the manufacturing of carcass and rubber material used in these tires.
Double ply tires have thick casings due to which their thickness would not allow these tires to cause less stretching because the rubber material has more power due to larger width, but single ply tires have a thin layer of casing due to which their casings have lower tolerance rate and these would not tolerate higher pressures, heat, cold and will stretch more due to which their width and size also increases.
Tubular Tires Stretch more than tubeless tires:
Tubular tires are most famous for stretching due to the inner material and casings which do not tolerate higher temperatures of both winter and summer seasons, and when you are running the same set of tires for both tires then when summer passes you will check the size and width of your tire, you will see a noticeable difference which happened because of stretching of the tires, besides this higher or lower internal pressure of tubular tires would also matter a lot mostly for tubular tires.
Drops And Whipping Can cause tires to stretch:
When you are flying your bike in the air while performing whips and drops on the trails, then many times it happens you will land on the ground by putting your pressure on side of the bead with a large force, as a result, this side of the tire will hit with a large force on the ground surface and many times it happens if the tire is old or with any defect in past, then it suddenly slip out from the rim.
it is a common problem when you are whipping on your bike or when you are skidding on the corner on trails because mountain bike rims are hookless and the air pressure is also low, the tire would suddenly cause stretching of 1mm to 2mm and unmount from the rim.
Tubeless Tires can cause Stretching With Tubes Inside :
Tubless tires or to be more specific tubeless ready tires will stretch more if there’s a tube inside the tires because you would want to run more pressure in the tubes and also for the reason that a tube is present in them it cause the tires to stretch especially in hotter environments tires do stretch alot and for tubelss ready tires when you use them with tubes they would stretch 1mm-2mm which is normal any more stretching than this could be harmful for the tires.
Signs Of Tire Stretching :
While installing tires on their recommended rims, you will notice the tire has been seated on the bead much easier without using any tool, or without using any soapy water which for tubeless tires is usually what we do.
or any spray material, it is the first sign and the other sign is that when you go for a ride on aggressive and rough terrains, these tires would slip from the rim beads and come out from the rim, if you are driving at higher speed on the trails.
both of these signs are clear indicators that tires have stretched too much and you may need to change them if the process repeats.
Conclusion :
Tires streching is not a big deal until they start showing abnormal growth the best way to see it is when you are setting up the tire on the rim or taking it off the easier it gets to get the bead on the tire the more loose the tire gets and the more chances there are that it would come off the rim.
So always pay attention to this kind of behaviour and make sure that you are not the one responsible for making it stretch