Wheel bearings etc

November 17, 2009 by mike.cox

Technical. No 2.
Getting the wheels set-up properly and in line.
 
How are the bearings?
Fit the wheel to the bike without any brake assembly, or set the brakes so there is no binding whatsoever.
Spin the wheel. It should rotate for 1 to 2-minutes or more and never come to the same place when it stops.
If the bearings are shot or too tight, you need to fix this before carrying on.
Most new bearings are sealed, but the older models are not.
Washing the bike, especially with a pressure washer it forces water into the bearing. No matter how much grease is in there, water will eventually cause pitting.
 
A spoked wheel relies on a few spokes to carry all the weight. On a 40 spoke wheel only the 6 or 8 spokes at the top carry the weight, the rest are carrying nothing. They do however keep the rim aligned to the hub.
Spokes should be tight but not overtight. When tapped with a metal object, each one should ‘ring’ the same as the others.
Over-tightening spokes leads to spokes snapping and distortion of the rim.
A spoke thread is rolled onto the end. You cannot use a die nut to repair a spoke.
A wobble or weave in a rim indicates spokes that have been incorrectly tightened, or the bike went over a curb in a previous life.
 
Then your tyres should be on the rims correctly. In that I mean, the rib running around the side wall should be the same distance from the rim edge all the way round and the same both sides.
When you use a front tyre on a rear rim, it is recommended that the front tyre used on the rear should be fitted backwards. This is to stop the possibility of the laminations separating under hard acceleration or braking.
 
Tyres have a dot placed on them when manufactured, showing the heavy point.
This usually goes opposite to the innertube valve.
When everything so far is correct, you can balance the wheel.
 
 
What about tyre pressures?
It is recommended that when we ride on a track, the pressures checked cold should be around 1.9 to 2.1 bar. No more. This is for medium to heavyweight machines.
If you purchased a pressure gauge for less than R100.00, how accurate is it?
If it’s laid in your toolbox for donkeys years and been bashed about, can you trust it?
Check your gauge against somebody else’s gauge on the same tyre for peace of mind.
Checking hot is a no, no.
I can send you the formulas for the combined gas laws involving and the interaction of pressure, temperature and volume if you really want to do this accurately when hot!
 
 
We all have different methods of checking wheel alignment, but some methods are far better than others.
Using the marks on the rear swingarm is for sedate road machines. When you are looking for the best handling possible, you need something better.
 
A welding rod bent into an elongated ‘C’ is a foolproof method of checking the wheel is aligned properly.
I have mentioned this before, but it’s worth mentioning again.
Place the short bent end onto the centre of the swingarm shaft and the other onto the centre of the rear wheel shaft.
Bent until both ends are in the centre of both shafts.
Now go to the other side of the bike.
Loosen and adjust the rear wheel until the distances are identical.
 
The front end is a different kettle of fish.
The wheel should be in line because the fork mountings for the wheel shaft are un-adjustable.
However the distance between the wheel on one side to the other is often way out.
You need spacers to get this right.
 
If the wheel is pointing off to one side, this points to a fork stanchion that is bent.
I use a piece of string fitted around both wheels, as close to the spindles as possible without touching anything else.
Rotating the tyre slightly causes the string to become tight. There must be the same amount of gap on both sides of the tyres. This can only be done once the back wheel has been aligned.
A long straight plank can also be used, but storing a piece of string is easy. Try putting a 6ft plank into a drawer.
 
 
Front end shakes.
When we put on brakes, it’s usually at the last second and hard.
If we only have a braking system on one side of the forks, the forks will and do twist slightly.
Using a single brake causes the whole assembly to try and pivot around the braking point and it can also cause an out of balance gyroscopic affect as well.
If you don’t have a strong front mudguard, a fork brace will get rid of most of the front end shakes and stabilise the steering into corners.
Some members have specially made fork braces that are made for their particular machine, however you can have some aluminium plate bent up to fit between both forks and use the mudguard mounting bolts as attachment points. I used 8mm plate, but this maybe a bit of overkill?
Cost? I think I paid R12.00.
 
So I hope your wheels are now true and set up to the best of your ability?