11. Tyres: removal and refitting

  1. It is strongly recommended that should a repair to a tubeless tyre be necessary, the wheel is removed from the machine and taken to a tyre fitting specialist who is willing to do the job or taken to an authorised BMW dealer. This is because the force required to break the seal between the wheel rim and tyre bead is considerable and considered to be beyond the capabilities of an individual working with normal tyre removing tools. Any abortive attempt to break the rim to bead seal may also cause damage to the wheel rim, resulting in an expensive wheel replacement. If, however, a suitable bead releasing tool is available, and experience has already been gained in its use, tyre removal and refitting can be accomplished as follows.
  2. Remove the wheel from the machine as described in Sections 2 or 3, as appropriate. Deflate the tyre by removing the valve insert and when it is fully deflated, push the bead of the tyre away from the wheel rim on both sides so that the bead enters the centre well of the rim. As noted, this operation will almost certainly require the use of a bead releasing tool
  3. Insert a tyre lever close to the valve and lever the edge of the tyre over the outside of the wheel rim. Very little force should be necessary: if resistance is encountered it is probably due to the fact that the tyre beads have not entered the welt of the wheel rim all the way round the tyre. Should the initial problem persist, lubrication of the tyre bead and the inside edge and lip of the rim wilt facilitate removal. Use a recommended lubricant, a diluted solution of washing-up liquid or french chalk. Lubrication is usually recommended as an aid to tyre fitting but its use is equally desirable during removal. The risk of lever damage to wheel rims can be minimised by the use of proprietary plastic rim protectors placed over the rim flange at the point where the tyre levers are inserted. Suitable rim projectors may be fabricated very easily from short lengths (4 - 6 inches) of thick-walled nylon petrol pipe which have been split down one side using a sharp knife. The use of rim protectors should be adopted whenever levers are used and,therefore, when the risk of damage is likely.
  4. Once the tyre has been edged over the wheel rim, it is easy to work around the wheel rim so that the tyre is completely freed on one side.
  5. Working from the other side of the wheel, ease the other edge of the tyre over the outside of the wheel rim, which is furthest away. Continue to work around the rim until the tyre is freed completely from the rim.
  6. Refer to the following Section for details relating to puncture repair and the renewal of tyre's. Check with the importer or with a BMW dealer for a list of approved makes and types of tyre before purchasing; fit only those recommended. See also the remarks relating to the tyre valves in Section 13.
  7. Refitting of the tyre is virtually a reversal of removal procedure. If the tyre has a balance mark (usually a spot of coloured paint) indicating its lightest point, as on the tyre's fitted as original equipment, this must be positioned alongside the valve. Similarly any arrow indicating direction of rotation must be fitted pointing the right way. If only one arrow is found this must be fitted pointing in the direction of rotation on rear wheels, but opposite to the direction of rotation, to accept braking loads, on front wheels. Where two arrows (marked 'Front wheel' and 'Rear wheel') are provided, fit the tyre as indicated by them.
  8. Starting at the point furthest from the valve, push the tyre bead over the edge of the wheel rim until it is located in the central welt. Continue to work around the tyre in this fashion until the whole of one side of the tyre is on the rim. It may be necessary to use a tyre lever during the final stages. Here again, the use of a lubricant will aid fitting. It is recommended strongly that when refitting the tyre only a recommended lubricant is used because such lubricants also have sealing properties. Do not be over generous in the application of lubricant or tyre creep may occur.
  9. Fitting the upper bead is similar to fitting the lower bead. Start by pushing the bead over the rim and into the welt at a point diametrically opposite the tyre valve. Continue working round the tyre, each side of the starting point, ensuring that the bead opposite the working area is always in the well. Apply lubricant as necessary. Avoid using tyre levers unless absolutely essential, to help reduce damage to the soft wheel rim. The use of the levers should be required only when the final portion of bead is to be pushed over the rim.
  10. Lubricate the tyre beads again prior to inflating the tyre, and check that the wheel rim is evenly positioned in relation to the tyre beads. Inflation of the tyre may welt prove impossible without the use of a high pressure air hose. The tyre wilt retain air completely only when the beads are firmly against the rim edges at all points and it may be found when using a foot pump that air escapes at the same rate as it is pumped in. This problem may also be encountered when using an air hose on new tyre's which have been compressed in storage and by virtue of their profile hold the beads away from the rim edges. To overcome this difficulty, a tourniquet may be placed around the circumference of the tyre, over the central area of the tread. The compression of the tread in this area wilt cause the beads to be pushed outwards in the desired direction. The type of tourniquet most widely used consists of a length of hose closed at both ends with a suitable clamp fitted to enable both ends to be connected. An ordinary tyre valve is fitted at one end of the tube so that after the hose has been secured around the tyre it may be inflated, giving a constricting effect. Another possible method of seating beads to obtain initial inflation is to press the tyre into the angle between a wall and the floor. With the airline attached to the valve additional pressure is then applied to the tyre by the hand and shin, as shown in the accompanying illustration. The application of pressure at four points around the tyre's circumference whilst simultaneously applying the airhose wilt often effect an initial seal between the tyre beads and wheel rim, thus allowing inflation to occur.
  11. 11 Having successfully accomplished inflation, increase the pressure to 40 psi and check that the tyre is evenly disposed on the wheel rim. This may be judged by checking that the thin positioning line found on each tyre wall is equidistant from the rim around the total circumference on the tyre. If this is not the case, deflate the tyre, apply additional lubrication and reinflate. Minor adjustments to the tyre position may be made by bouncing the wheel on the ground.
  12. Always run the tyre at the recommended pressures and never under or over-inflate. The correct pressures for original equipment tyre's are given in the Specifications Section of this Chapter; check with the tyre manufacturers (if non-standard tyre's are fitted) and use their recommended pressures, if different.

photo 11.7a
11.7a Spots of paint usually indicate tyre's lightest point (check with manufacturer) - align with tyre valve on refitting

photo 11.7b
11.7b Arrows on tyre sidewall indicate direction of rotation - see text

Fig 9.6
Fig. 9.6 Method of seating the beads on tubeless tyre's

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