Changing tyres

Changing the tyres on a kart can be extremely frustrating (as well as a lesson in patience) if you’ve not seen it done before by someone who knows the drill.  Those who know the in’s and out’s make it seem like a walk in the park, particularly if one has the correct tools at hand.

Suggested tools

Apart from the more obvious bits such as a compressor to inflate the tyres once mounted, and a tyre pressure gauge to check the levels of inflation, it is nigh on impossible to remove the tyres from the rims (without doing damage) unless you have access to a bead breaker as shown below.  Another useful tool is a set of tyre tongs that are used both when removing and/or fitting tyres to the rim.  Some of the more experienced folks can get by using their knees and a bit of brute force, but a set of tongs really makes the job a lot easier for the novice.  Another useful tool is a valve key that can be used to both deflate a tyre quickly, or to replace a worn out valve that is leaking.  Lastly, some tyre grease on a rag, or a spray bottle with some dishwashing liquid makes tyre fitment onto the rim so much easier.

Removing an old tyre

Firstly, remove the rims c/w tyres from the kart.

Step 1.  For rims that are fitted with bead screws as indicated by the arrow in the Step 1 picture below, these must be removed completely, and this will automatically cause deflation of the tyre.  On rims not fitted with them, removal of the valve does the same job.

Step 2.  Place the tyre plus rim onto the bead breaker (Step 2A) and then break the beads on both the rear and front sides of the tyre respectively as shown in Step2B.

Step 3.  Place the rim on a flat surface with the rear side uppermost (valve is now facing down and out of the way), and fit the central disc of the tyre tongs into the rim as shown in the picture.

Step 4.  Push down on the tyre to give a good gap, and insert the tip of the tyre tongs into the resulting gap, noting that the nylon clips on the tongs must be furthest away from you.

Step 5.  Pull the handles of the tongs towards you so that the jaws slide over the rim itself.

Step 6.  When the tongs are finally lying flat, insert the pin into the central hole of the disc.

Step 7.  Open the handles of the tongs as shown, and the tyre will pop free of the rim.

Step 8.  Remove the tongs and the central disc – you may need to use the pin to free it up.

Step 9.  Flip the rim and tyre so that its axis is horizontal, and then crunch up the tyre onto the outer edge of the rim (the valve side) as shown.

Step 10.  Lay the tyre flat, twist the rim to an angle of about 45° and pull upwards.

Step 11.  Maintaining an upward pull on the rim, roll the rim out of the tyre completely.

Repeat the above steps for the rest of the tyres, and you’re done with the removal.  Whilst you have all the rims off, give them a good clean and inspect each valve stem (that’s the rubber part that fits through the rim to the outside world) for damage or cracks.  Replace if necessary.  Also inspect all the O-rings on the bead screws for damage and replace as required – this is a potential source of air leakage that can lead to a flat tyre and is not something you want happening when you’re out in front leading the field.

Fitting a new tyre

Step 1.  Commence by applying some tyre grease with a rag to the beads on either side of the tyre.  A spray bottle with some dishwashing liquid works just as well.

Step 2.  Put the tyre on the ground with its axis horizontal and use your knee to dimple the outside of the tyre in two places opposite each other.

Step 3.  Ensure you start the mounting operation with the rear side of the rim (refer picture) i.e. the side away from the valve stem.

Step 4.  Angle the rim at about 45° and push the rear edge of the rim into the rear face of the tyre as shown.  Bearing in mind which corner of the kart the wheel is destined for, ensure you get the rotation arrow on the sidewall of the tyre correct for the rim in question because you will need to start from scratch if it is incorrect – refer note at the end of this chapter.

Step 5.  The rim should then drop easily into the tyre as shown in the picture.

Step 6.  Flip the rim and tyre over, and insert the disc of the tyre tongs into the rim – note that you are now working on the rear side of the rim i.e. the side away from the valve stem.

Step 7.  Lay the tongs flat on the tyre and fit the pin.  Then depress one side of the tyre and insert the shaped nylon clips of the tongs into the resulting gap, ensuring that they are gripping the underside of the edge of the rim as shown by the arrow.

Step 8.  Commence opening of the jaws and continue until they are fully open.  Sometimes it is easier to tip the assembly slightly upwards to aid this process (refer pictures 8A and 8B).

Step 9.  Reinsert all the bead screws into the rim but only by a thread or two.

Step 10.  Check they are not screwed in too far by pushing down on the tyre as shown otherwise they will damage the tyre when you inflate it.

Next, inflate the tyre until you hear two pops – one for each side as the tyre seats against the edges of the rim.  Immediately remove one of the bead screws so that the tyre deflates.  Alternatively, if there are none on the rim, then remove the valve or drop the pressure by some other means.

Once the tyre is deflated, tighten the bead screws into place ensuring the O-rings are firmly seated.  Then re-inflate the tyre to the correct pressure and check there are no leaks at the valve or the bead screws.  Do this by using some water over the screw heads or the valve stem and checking for bubbles which indicate the presence of a leak.

Repeat for all the other tyres, and its job done!!

Note on direction arrow

As you offer the rear side of the rim into the tyre, then the following applies.

• If the direction arrow is facing clockwise, the wheel is destined for the RHS.

• If the direction arrow is facing anti-clockwise, the wheel is destined for the LHS.

Emile McGregor - MSA Technical Consultant