Redishing questions for a fixie

[bobg]

Just had my first stab at it and it (eventually) turned out OK but I'd appreciate help with the following.. I have an ancient truing stand which is fine for resolving run out but no way ( apart from "eye") to measure ovality.
1. All the other stuff I read suggests centring the axle before redishing, I fear I'm having a senior moment, but why?? Surely the aim is to centre the rim ie remove bias on the driveside. Can't centring the axle can be done afterwards??
2. I was very careful to stacken off the driveside spokes one complete turn before tightening the other side a similar amount. No matter how careful I was with the driveside slackening, the wheel went out of true. Should I retrue it immediately before or after retightening the other side?
3. Is one spoke nipple revolution at a time too cautious? I had to repeat the process 6 times to finish the job
4. Does a dishing tool fit on to a truing stand or just bolt to the axle in some way? ... Has anybody made one??

Thanks in advance
Bob

 

[gwhite]

I would have thought that all that would be required for a fixed wheel is to reduce the dish. As a 9 speed block would usually need approx 3mm dish then I'd bring this down to round 1mm or less for the fixed. To do this I'd work with half a turn each nipple and do it one pair at a time. i.e. undo the drive-side spoke by half a turn while tightening the opposing non-drive spoke by the same amount. Better to work in small increments when doing this.
By changing the dish you invariably affect the radial trueness so the need for a dishing tool. The tool is used off the jig and measures the distance between the rim and the locking nut on both sides of the wheel. First place the tool on the non-drive side and the distance between the rim and the locking nut on that side is measured. This is your reference.The tool is then locked in this position. On the drive side this is repeated. On a wheel with no dish the two measurements should be the same i.e. the ends of the tool should be flat on the rim when the centre portion is down against the locking nut. On a dished wheel on the drive side, the amount of dish is the gap between the centre axis of the dishing tool and the lock nut with the ends of the dishing tool are flat on the rim. Make sure that you de-stress the spokes as if this is not done then the wheel will go out of true when it's used. The tension on the spokes on both sides of the wheel should be pretty even given the lack of dish. This is important if you want to prevent spoke breakages.
I'm aware that this sounds complex and someone may come along and explain it better than I can. It's much easier to understand when the process demonstrated. It is possible to make a dishing tool and the home-made jobs are usually made from wood. Google is your friend here.

 

[Ian H]

I don't use a dishing tool, just turn the wheel round to check the rim's centred over the axle ends. With this method, of course, the axle has to be in the right place first. Hence the advice you've read.

It should be easy enough to rig something to check roundness - can you just stand something near to the jig so that the rim runs very close past it?

 

[BigTone0777]

I dished mine on the bike, can't get a much better reference than the stay's it's gonna sit in

 

[bobg]

Thanks very much for all the info. I have it all clear in my mind now. Think I prefer to slacken all the drive side off and then tighten all the non drive side cos I found it easy to get confused doing it the other way