Wheel Bearing replacement | The Easy way
Wheel bearing replacement on a dirt bike is an occupational hazard. On road bikes you can go years without ever needing to think about replacements, but once you venture off road it’s a different story. The constant bashing from the terrain coupled with the additional vibration when those knobbies are on the tarmac means that those little bearing races have a pretty tough time in their short life.
This was the case with the trusty KTM EXC250 which managed to totally lunch it’s own bearings on the last day of a three day sortie into the Cantal region in France. Only twenty or so miles from home there was a worrying wobble and a distinct lack of feel to the front brake, so the bike was nursed to safety and consigned to the support van for the last section.
So with a complete new front wheel repair kit purchased from KTM at an eye-watering £45, it seemed like an idea to run through how we go about replacing bearings. OK – we know everyone does it a bit differently, but this is our way …
FIRST STEP – WHEEL OUT AND REPLACEMENT KIT PURCHASED. THIS HAS BOTH BEARINGS, DUST SEALS, CENTRAL SLEEVE AND THE TWO SIDE SPACERS
BEFORE WE DO ANYTHING, WE TAKE OUT THE BEARINGS, SLIP THEM INTO A SEALABLE BAG AND PUT THEM IN THE FREEZER FOR AT LEAST AN HOUR. THIS CONTRACTS THE METAL TO ENSURE AN EASY FIT
SO WE START OFF BY REMOVING THE DUST SEALS WITH A SCREWDRIVER – IT DOESN’T MATTER IF WE DAMAGE THEM AS THEY ARE TOAST
NEXT, STARTING FROM ABOVE, WE LINE UP A SOFT METAL DRIFT – ALUMINIUM OR BRASS – AND BEGIN TO KNOCK OUT THE OLD BEARING, SLOWLY TAPPING AWAY AND MOVING THE DRIFT ROUND. TAKE YOUR TIME AND DON’T HIT TOO HARD. IF THEY ARE NOT MOVING, WE SOMETIMES NEED TO SUPPORT THE HUB AND USE A BIT MORE FORCE
ONCE BOTH SIDES ARE REMOVED, WE THOROUGHLY CLEAN THE BEARING SEATS AND GENTLY DRESS THE SURFACES IF THERE IS ANY DAMAGE
OK SO NOW WITH THE BEARINGS BUSY COOLING DOWN IT’S TIME TO HEAT UP THE HUB TO EXPAND THE METAL. WE USE A HAIRDRYER FOR TEN MINUTES OR SO, BY WHICH TIME THE HUB IS ALMOST TOO HOT TO TOUCH – IDEAL
CAREFULLY WE DROP THE NEW BEARING INTO THE HUB, ENSURING IT IS ENTIRELY STRAIGHT
USING A HIDE MALLET OR EQUIVALENT, WE TAP THE BEARING IN SO IT SITS FLUSH, AND THEN USING A VERY LARGE SOCKET – PREFERABLY THE SAME SIZE AS THE OUTER BEARING SURFACE – WE CONTINUE TO TAP THE BEARING DOWN UNTIL IT SITS ON THE BOTTOM SEAT. WITH THE BEARING COLD AND THE HUB HOT, THIS SHOULD BE RELATIVELY EASY
ONCE THE ONE SIDE IS DONE, WE DROP IN THE INTERNAL AXLE SLEEVE. IT’S IMPORTANT NOT TO FORGET THIS AS YOU MAY DAMAGE THE BEARING IF IT NEEDS KNOCKING OUT AGAIN JUST AFTER INSTALLING THEM – YES, WE’VE BEEN THAT GUY …
WE THEN DROP IN THE SECOND BEARING AND REPEAT THE SEATING PROCESS. IF THE SOCKET IS NOT THE EXACT SIZE, IT MAY NEED MOVING ROUND AS THE BEARING IS TAPPED INTO PLACE
NOW THAT BOTH BEARINGS ARE CORRECTLY SEATED, THE DUST SEALS CAN BE FITTED WHICH SHOULD USUALLY JUST PUSH INTO PLACE BUT SOMETIMES NEED A LITTLE FORCE
IF THE BEARING IS FULLY SEATED THE TOP SURFACE OF THE DUST SEAL SHOULD BE JUST BELOW THE TOP SURFACE OF THE HUB
NOW WE GREASE THE DUST SEAL AND INSERT THE OUTER SPACER. THESE ARE NOT HANDED SO IT DOESN’T MATTER WHICH IS USED FIRST
WE THEN TAP THE SPACER INTO THE BEARING ON THE ONE SIDE UNTIL IT IS FULLY SEATED
THE FINAL PART IS TO FIT THE SECOND SPACER AFTER GREASING THE DUST SEAL, BUT AS WE TAP IT INTO PLACE WE MAKE SURE BOTH SPACERS ARE PROPERLY POSITIONED INSIDE THE INTERNAL SLEEVE. ONCE IN PLACE THE JOB IS DONE – TIME FOR A CUP OF TEA AND THEN REFIT THE WHEEL
So that’s the wheel bearings replaced and good for another load of off-road tomfoolery.
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It will be the best decision you make today ….
PLEASE NOTE: THIS BLOG IS PRESENTED AS AN INDICATION OF HOW WE CHANGE OUR BEARINGS ONLY AND SHOULD NOT BE USED AS A DEFINITIVE GUIDE. ONLY ATTEMPT ANY MAINTENANCE ON YOUR MOTORCYCLE IF YOU ARE COMPETENT TO DO SO AND HAVE SUFFICIENT KNOWLEDGE AND THE CORRECT TOOLS TO COMPLETE THE TASK SAFELY.
IF IN DOUBT, TAKE YOUR MOTORCYCLE TO A QUALIFIED MECHANIC.
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