Tire defect
Tire defect describes the defect of a tire. This usually means a pneumatic tire on a motor vehicle; sometimes a pneumatic tire on another vehicle (e.g. bicycle tires , aircraft tires , commercial vehicle tires , motorcycle tires ).
Use of language
A flat tire is called in most of Germany a " plates ", formulated as "have a flat tire," probably as a shortening of "a flat tire have". In Austria, on the other hand, a tire defect is called a " slap ". There is also the German minor variant " Flatfoot ".
Breakthrough
A puncture or pinch hole is used for tires that contain a tube if the tube has been perforated by the tire hitting an edge or a stone. If the air pressure is too low or the speed is too high, the tire tread will be pushed through to the rim when the edge hits. The tube lying close to the jacket is folded up, clamped between the jacket and the rim and punched through. Since the tube, like the jacket, is doubled when the tire is compressed, two characteristic holes are created that are relatively close to each other and often look like short cuts. In English, such a breakthrough is called a snake bite , as the two adjacent holes are reminiscent of a snakebite. Breakdowns are more likely to occur in bicycle tires that have a relatively thin jacket, since the compression here is concentrated in a small area.
causes
The following can cause a tire failure in a pneumatic tire:
- A leaking valve can cause slow pressure loss .
- Damage to the rim flank can reduce the seal against the rubber of the tire to such an extent that the tire slowly loses pressure - a common problem with aluminum rims that are driven too hard on curbs.
- Damage to the weak tire flank by driving onto the curb at an acute angle. The resulting cracks in the carcass can lead to an abrupt loss of air. The cracks can often only be seen from the inside.
- Damage to the weak tire wall from snow chains. Under unfavorable circumstances these chain links can dig into the soft tire sidewall and break out parts of the rubber.
- Operating pressure in the tire is too low . This causes the tire to overheat at higher speeds as a result of walking, with the result that the tread becomes detached.
- Aging of the tire. The week of manufacture and the year can be seen from the DOT number on each tire (e.g. 1910 = 19th calendar week 2010). In the case of little-moving vehicles (e.g. caravans ), the tire tread is not worn; nevertheless the tire ages . Outdated tires can be recognized by fine hairline cracks and embrittlement of the tread.
- Faulty tire valve or missing valve cap. At higher speeds, the centrifugal force can cause the valve to open easily. The valve cap can protect against short-term pressure loss due to a defective valve.
- Penetration of foreign objects (nail, screw, glass, etc.). In vehicles without tubular tires (tubeless), the air escapes slowly; It usually takes 2 minutes until the pressure is completely lost. With tubular tires, the air usually escapes faster.
- Parking the vehicle for too long (a few weeks or more). If the tires are always on the ground at the same point on the circumference of the tire during this time, they will permanently deform at this point, and what is known as a “flat tire” is created. The process is faster, the higher the ambient temperature. The driving comfort is impaired as a result, the tire runs out of round. It can also burst, as the tire often becomes very hot when driving with a flat tire. A stand plate on vehicle trailers, such. B. caravans or boat trailers represent an increased risk of accidents, as it can skid. After a while of driving, this problem usually occurs in cars. The tires only have to be replaced in extreme cases. Air-filled tire cushions , for example, offer protection against standing plates , which distribute the contact force over a larger area. The safest way to avoid standing damage is to completely relieve the tires, e.g. B. with axle supports.
Excessive air pressure does not lead to a tire defect. The bursting pressure of a modern car tire is over 10 bar . However, if the pressure is significantly too high, the tire will wear unevenly (and usually also overall higher): it will be more worn in the middle than on the edge, since the middle part of the tread bulges outwards. In addition, the wear and tear on the chassis increases because the tire bounces less. In addition, grip is significantly reduced.
Exceeding the prescribed pressure by only 0.2 to 0.3 bar does not, however, lead to such problems; Instead, it reduces the rolling resistance and wear of the tire and is therefore recommended; the (suspension) comfort is a bit worse.
repair
Car tires
Damage to car tires can usually be repaired as long as the tire was not damaged too much by the loss of pressure and use. The resulting hole is technically called the branch canal , or damage canal . The tire is properly removed from the rim for repair . A safe repair is made with plasters and wads. On the inside of the tire, a plaster (so-called. Is at the damage site repair patches ) mounted after the fresh cleaned and roughened branch channel was sealed with a rubber stopper. The puncture canal can be closed with a pre-vulcanized repair body or with raw rubber. The raw rubber must then also be vulcanized for a certain period of time under pressure and temperature supply from 98 ° C. Instead of plasters and plugs, a combination repair body is often used, also known as a "repair mushroom" due to its shape. This is pulled through from the inside of the tire to the outside and seals the puncture channel through the shaft and the inner core (also called inner liner) through the ceiling plaster. The protruding length of the shaft is cut off at the height of the existing profile. Repair bodies vulcanize chemically at normal ambient temperature. For this purpose, a binding layer on the surface of the repair body must be brought together with a suitable vulcanization fluid. Combination repair bodies may only be used in the tread of the tire, within the belt package.
A repair appears sensible and justifiable if one works with experience, specialist knowledge and non-obsolete repair material and solvents. The person performing the work ( vulcanizer ) is responsible for the repairs carried out. The legislator has created a basis for a regulation in §36 of the StVZO . The “Guideline for the Repair of Pneumatic Tires” (Federal Traffic Gazette Document B 3620) gives more precise information. Since June 1, 2008, there are no longer any restrictions on the tire's speed index; ZR tires can also be repaired. However, there are restrictions imposed by the tire manufacturers and repair material manufacturers. There are also restrictions on car insurance that must be observed. In accordance with the specifications of the repair material manufacturer, no repairs should be carried out in the bead zone of car tires if the fabric is also damaged. Pure rubber injuries on the bead can be repaired. Sidewall repairs can be repaired with warm vulcanized rubber in the worked out damage and a ceiling plaster with fabric reinforcement (only by specialists with appropriate training according to HwO ). The breakdown assistance available on the market should only be viewed as a makeshift solution. Inserting an air tube to seal a damaged tire is not permitted. Assessing a repair site without removing the tire and checking the inside of the tire is negligent .
Bicycle tires
In contrast to car and motorcycle tires , which are usually tubeless, the tires on bicycles usually have a tube . In contrast to car tires, it is not the "coat" that is paved, but the tube.
The repair can usually be carried out by the cyclist himself on the way. You may need tools to dismantle the wheel and jacket, as well as a repair kit for the bicycle tube and an air pump.
First, the tire should be lifted out of the rim in order to scan the inside for any foreign bodies that may have entered. You should also watch out for small shards of glass that have stuck to the outside of the jacket material and may only puncture the hose when it is loaded. If a foreign body is found, the hole in the tube can be easily located if the tube is still in the tire. Alternatively, if the hose is to be removed for a more thorough examination of the jacket, the position of the valve on the jacket can be marked while the hose is still in the jacket.
If the hole cannot be found in this way, the air escaping from the hole when the hose is inflated can be felt more easily if the hose is guided past a sensitive part of the body, such as the lips. Very small holes that do not produce a noticeable draft can be found by submerging the hose under water.
Before applying the patch, the smooth rubber surface around the hole should be roughened until it appears uniformly matt. Seams and burrs from the manufacture of the hose must be largely abraded to ensure that the patch is applied evenly and airtightly. Care should be taken here, however, not to accidentally sand through any protruding folds or edges of the hose. With older hoses in particular, sandpaper should be used instead of the rasp-like sheet metal that is included with some repair kits.
Then a drop of vulcanizing liquid is applied to the hole and distributed with the (clean) fingertip. This is the easiest way to achieve an evenly thin application, which is the prerequisite for rapid drying of the adhesive and immediate adhesion of the patch. As with contact adhesives , the contained solvent must evaporate in order to allow crosslinking of the rubber material (cold vulcanization). After the patch has been applied, any remaining solvent can only very slowly diffuse out through the material .
The patch should therefore only be applied after a few minutes of drying. Occasionally it is recommended to check with the back of a clean finger whether the adhesive is actually completely dry. The protective film is only peeled off immediately before the patch is applied in order to avoid contamination of the adhesive layer. The more pressure is exerted on the patch, the greater the initial adhesion of the patch. For this purpose, the patch can be pressed on with a screw clamp or tapped with a hammer. If necessary, a stone can be used to knock on the road.
The patch will take a few hours to fully adhere to it. A replacement tube should always be carried with you on longer bike tours, which will be used in the event of a breakdown. The patch on the repaired tube has time to vulcanize.
Patches made of plastic, which are equipped with a strong pressure-sensitive adhesive and do not require a vulcanizing liquid, are also increasingly being offered. Depending on the manufacturer, more or less thorough cleaning or roughening of the damaged area is recommended. After the patch has been affixed, the tube can be used again immediately.
Larger patches are also available, which are used to repair holes and cuts in the tire and for this purpose are glued into the casing from the inside. If you don't have such a patch at hand, you can make do with a somewhat larger, normal patch or cover the hole from the inside with sturdy adhesive tape. To prevent the hose from pushing through a damaged area in the jacket, paper or banknotes can be pushed into the jacket as a first measure.
A tire sealant or tire sealing gel can be used to prevent punctures. This can be inserted into the tube after removing the valve and prevents the air from escaping if the tire is punctured. As a rule, cracks or cuts cannot be sealed. The liquids contain a binding agent that hardens on contact with atmospheric oxygen, as well as fibers that increase the stability of the plug.
Breakdown kit
prevention
With the current technology, a driver has to reckon with a flat tire every 150,000 kilometers; on a bicycle there are often only a few hundred kilometers between two defective tires. Because of these very different breakdown probabilities, most preventive measures are aimed at bicycle tires - but the following two are also general:
- Sufficient tire pressure significantly reduces the risk of tire defects in all types of vehicle.
- Foreign bodies often work their way slowly into the tire only over long distances and do not immediately lead to defects. In the case of cars, a corresponding control of the treads at sufficiently short intervals is hardly practical, but in the case of two-wheelers this measure is easy to carry out and very effective.
Puncture protection for bicycle tires
Choice of material
The rubber of jackets and hoses loses its elasticity over time. In exceptional cases it can make a difference whether a hose comes fresh from production or has been stored at the dealer for two years. Older hoses, as well as hoses of lower quality, tend to perforate with little or no acute external impact. So z. B. when wide tires are used on particularly narrow rims. See: Ratio of tire to rim width .
"Puncture-proof" bicycle tires
Several well-known manufacturers now offer so-called "puncture-proof" bicycle tires. As a rule, the running surface is reinforced by an insert made of highly elastic special rubber , so that foreign bodies can no longer penetrate up to the length of a thumbtack. In addition, largely cut-resistant, close-meshed fabric inserts made of liquid crystal polymers with properties similar to spider silk are used. Bicycle tires with such equipment improve the puncture safety significantly, but cannot guarantee one hundred percent puncture protection, so the term "low-puncture" tires would be more appropriate.
Puncture protection tapes
In the bicycle trade, puncture protection tapes are also offered, which are placed between the tire and tube and, in contrast to the integrated puncture protection belt, can be used after a tire change (for example due to wear). However, assembly can be difficult, as they have to be brought to the exact center of the tread by walking before they are inflated. To avoid friction between the puncture protection tape and the resulting breakdowns, talc should be used and the tire should be driven with high tire pressure. Correctly installed, good quality tapes offer extremely good puncture resistance with a low weight and hardly any noticeable impairment of the driving characteristics.
Removal of broken glass for bicycle traffic
A common cause of bicycle tire defects is broken glass on cycle paths , cycle lanes and other cycle routes . If these are not removed by the sweeping machine at the regular cleaning interval , some bicycle-friendly municipalities are ready to quickly remove soiling with broken glass that has been reported by citizens. Many municipalities provide an online complaint form or a smartphone app for such reports on their websites; the incoming messages are often used at the same time to optimize the cleaning plans.
Clean the running surfaces
It is sometimes common among racing cyclists to place the palm of their hand (with cycling glove) on the tread of the tire when driving through shards of glass in order to remove the shards. The benefit of this measure is controversial. With modern frames with a small gap between the seat tube and the rear tire, the hand should not be placed on the tire, as fingers can be pinched in the narrow gap and dragged along.
It can be useful to inspect the tread ( protector ) of the tubular tire if you suspect a broken-in splinter and to pry glass fragments and the like out of the rubber with a sharp object. Remaining splinters can initially only adhere superficially to the protector and only work their way through the protector and finally the carcass over time.
See also
Individual evidence
- ↑ Third round - flat tire on the bike , Atlas on German everyday language (AdA), Phil.-Hist. Faculty, University of Augsburg, June 19, 2006.
- ↑ Georg Böger: Technology tips: tires and rims , section "Standard" with consequential damage ", May 2000
- ↑ 2009 (TÜV Süd)
- ↑ Video (in English) about the use of repair mushrooms : Maruni Plug-Patch ( Memento of the original from May 26, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ What you should know about tire repairs. ( Memento from December 29, 2013 in the web archive archive.today ) Reifenunion
- ^ Jobst Brandt and Sheldon Brown: Wiping Tires , In: SheldonBrown.com
