Ride UK Tech Columns

#70 Wheel Truing

(This article first appeared in Ride UK issue No. 70 and is reproduced here by kind permission of Ride UK.)

With Tex taking a very 'tech' approach this month I thought I would go back to some basic stuff and do a good old fashioned tutorial.
I always said I wouldn’t do this. I always said that it wasn’t really possible. What I meant was that I didn’t think I could face it.
Truing wheels is an essential skill for anyone wanting to look after their own bike, yet there is no easy way to learn. Most people learn from their mates and from trial and error, but I am feeling cocky so fug-it lets have a pop at writing it down.

Now this isn't going to be easy to follow but I will do my best to break it right down and if you just stop every now and again to get a cup of tea and think about it, you will soon see that really it’s a piece of piss. I used to hate it when people tell you to do something without explaining why, so this is going to be more of an explanation of why truing your wheels works at all. If you can stick with it and understand the theory then there is nothing to "remember" you can always just stop look at your wheel and "work-out" what to do.

So first the theory.
Triangles rule. Triangles are super strong, as we all know, and spoked wheels are made of loads of triangles. This is where they get their lovely properties from and it is also why they can look so daunting to a novice wheel-monger.
The reason triangles are so strong and useful is that they are so easily defined and constrained.
If we know any three things about a triangle then we know pretty much everything about it.
If we know one angle and two sides or two angles and one side or three angles or three sides then we have the bastard nailed.
The most interesting of those is the three sides. Locking out an angle is pretty hard normally, but turn it into a triangle and lock the lengths of the sides, and that angle isn't going anywhere.
Stick your arm out to the side and try to keep it at 90 degrees to your body, if someone else tries to move it up or down then you will find it very hard to resist and even under its own weight you can feel the lack of rigidity. Turn the angle into a triangle by nailing your hand to one end of a bit of wood and the other end to your thigh (you might need some help with this part) and you will feel the improvement in rigidity.
The angles are controlled by the lengths of the sides. If those sides are adjustable then the angles are adjustable.
OK now get yourself down casualty and get those nails removed…

Looking at a bike wheel from the side you will see a shed load of triangles, but ironically these are almost irrelevant so forget about them, they will look after themselves. The triangles we are interested in are harder to spot because they don’t meet up very well in the corners and are funny shapes.
The triangle we need to think about is the triangle formed between two adjacent spokes at the rim and the hub.
Imagine your rim and tyre cut through in two places, leaving a short section of rim with two spokes in it, viewed head on this forms a triangle, and this triangle is the basis of all wheel truing.

If the spokes stuck straight up from a single hub flange then the rim would be like your hand at the end of your arm in the above example, the wheel would be ludicrously weak unless you used massive stiff spokes. But by using two spaced flanges we create a triangle, and triangles rule! remember.
Because spokes are adjustable in length (by screwing the nipple up and down the thread of the spoke) this triangle is adjustable so by controlling two sides we can control all the angles. And that is the basis of truing your wheel. Look at Fig1.
usefull picture
If you shorten the spoke on the left then the rim moves left, shorten the spoke on the right and the rim mover right. Simple. So as long as you think about what you are doing wheel truing is easy and obvious…
Well maybe not. There is a certain feel that you get after some practice that helps you judge what you are doing, you will eventually develop this feel but until you do things can be tricky.
Assuming that your wheel is pretty tight and true then taking out a little wobble is easy, but if you have let things slide a bit and the spokes are now fairly loose then you need to get some basic tension into the wheel before you start thinking about the little wobbles.
This is where people usually get bogged down. If you set off tightening spokes by feel without a lot of experience you will end up shifting the whole rim over to one side of the wheel. Keeping the hub central in the rim is difficult and requires that the spokes are not just the same TENSION but the same LENGTH.
Luckily there is a good work round for this that requires no skill or experience.

SIDENOTE:- Lets be absolutely clear about which way we are turning the nipples. I am constantly amazed by seeing people trying to tighten and loosen nuts and bolts who don’t seem clear which way they should be turning things. That’s not unreasonable, I tend to spend a lot of time tightening and undoing various nuts and bolts so it is instinctive but if you don’t its easy to get confused.
So here is a simple rule to help you out:-
Most threads are "right handed", so take your right hand  and stick your thumb out like you want to hitch a lift or condemn a man to death in ancient Rome (Lets get this straight too, thumbs up meant "waste the fucker", thumbs down meant "let him go". Yes the movies are wrong!).
So with your right hand point the thumb the way you want the fastener to go, then just turn the spanner the way your fingers are wrapped. Simple.
Now there are only a few places on a bike where you might find a "Left hand thread"; the left pedal and the left hand cones on a 1 piece crank; and left hand drive freewheels/cassettes. In those cases use your left hand in the same way.

But nipples are right handed so if you get confused whip out your right hand and use it. The nipple is like a nut on the end of a very thin bolt remember.

OK so back to this wheel.
Start off by loosening all the spokes until the first thread is just emerging from the nipple. If you do this to all the spokes (and they are the same good spokes throughout) then you now know that all the spokes are the same length. Now to get tension into them you can just add the same number of turns to each spoke nipple but DO IT SLOWLY. Do not be tempted to bung some huge number of turns onto each spoke because by the time you get back to the valve hole you wont be able to do it, the spokes on opposite sides of the wheel will be fighting each other and you wont have left enough slack to do it. So to prevent this put half as many turns on as you think it needs. Say 4. Work round the whole wheel from valve hole back to valve hole putting just 4 turns on each spoke. If the wheel is still super slack try another 4, if it seems to be coming tight cut back to one or two turns. Don’t worry about going too slow, put on a quarter turn if you feel unsure its only going to take a bit longer.

Now while you are doing this there is a very good chance that you will be interrupted. Somebody will knock at the door to ask if they can have the Betterware catalogue back; the phone will ring; you will desperately need a piss; and you will remember that the beans are on the hob at "full bollocks" and need turning down. At this point it is really easy to get lost. You put the wheel down or forget which way you were working and when you come back to it you cant easily pick up where you left off. So be prepared. When the door-bell goes, take the wheel with you, keep your fingers either side of the current spoke and your thumb pointing the direction you were working round the wheel. If you do fuck up and forget go back and start again.

OK so now you have a reasonably tight wheel, with the rim pretty much centred round the hub. Good. Now you have a good starting point for getting it really true and really tight.

First you need to deal with any "up-and-downers", these are harder to deal with than side to side wobbles but are still pretty simple.
Spin the wheel and look at it from the side, this is easiest to do in the frame by the way.
Does the rim spin smoothly at a constant height? If so good, nothing to do here and you must have done a good job in the earlier stages. If not then something somewhere is a bit out and needs fixing, but first you need to identify the problem better. Does the rim rotate nicely then do a little jump or does it slowly rise up then sink down as it turns?
If it is a little hop then it might well just be the weld or somewhere you have whacked the rim and given it a flat spot. If it slowly rises and falls then either you messed up or the hub is "off". To check the hub look in at the inner ends of the spokes. DO the holes in the hub flange also rise and fall as it spins? If so then there is your problem. This is fairly common (on cheaper hubs) and nothing to worry about it just means that you need to make a slight adjustment to all the spokes.

Either way we proceed in much the same way. Find the high spot and mark it. An easy way to do this is to spin the wheel and slowly bring a marker-pen in, until it just touches the rim on its highest points as it passes the pen.
Now if this is most of the rim (because it’s a weld dip or a flatspot) then you will need to start by slightly loosening ALL the spokes that meet the rim where it ISNT marked, before you tighten the spokes in the rest of the wheel. This will give the low point the slack it needs to move outwards. Work with say a single turn off each spoke, then put just a quarter turn on to the "high" spokes. You can see that the spokes you have loosened will take on all the movement from all the other spokes hence the disproportionate number of turns. This sort of "wobble" is the hardest to correct and you can't expect to get it perfect, so don’t go overboard on it, just do what you can then stop and live with it or get a new rim.
If the rim is off centre due to an eccentric hub then you ned to grade the number of turns you put on and take off. Its very obvious if you think about it. Just take a full turn off at the lowest point and put a full turn on at the highest point. In between "fade" the number of turns down to zero at the mid point between high and low. Keep re-marking the rim to check your progress after each set of corrections and it should soon come true.

Now we just have the side-to-side wobbles to deal with and this is easy. Thinking back to our triangles we know that we just need to tighten (shorten) the spokes on the side we want the rim to move towards, and, if it’s a bad wobble, loosen the spokes on the side we want it to move away from. For an obvious wobble you can work in half or even full turns but as they get smaller (and away from the centre of the defect) you can work down to quarter turns or even less.

Finally a word or two about tools and parts.
For a full true at home, just take the tyre off and use a flatbladed screwdriver on the inside of the rim to adjust the nipples, once you get the wheel tight you might want to switch to using a spoke key. If you are gteeing a spoke key get a good one that FITS your nipples really well, spoke keys come in a whole range of sizes so check it fits before you buy.

Spokes are just bits of wire (hopefully good quality stainless steel wire, but wire none the less) with a thread on one end that fits a special nut with a funny name, but the difference between good spokes and bad spokes is huge. A bad spoke, like Primo spokes for example, will stretch and stretch causing your wheel to loose tension and killing your rim and hub. Spokes are supposed to share the load all round the wheel but when they get loose they allow stresses to concentrate in small areas of the rim and hub flange. This is why keeping spokes tight and wheels true can mean the difference between a wheel lasting a month and 3 years. If you are getting a custom wheel built use high quality spokes or you are just wasting your money. 48spokes and nipples weigh just over half a pound, yet they take every force that the bike ever feels and spread it smoothly round the wheel, they are like the cables in a suspension bridge and they cannot do their job if they are loose, so keep them tight!


If you have a question, and you cant find the answer on the site then you can mail me direct by clicking HERE

Copyright © 2003 G-Sport.  All Rights Reserved.   The content of this website may not be reproduced or transmitted in any form in whole or part without the written permission of the owner.