wheel truing question

[onewheeldave]

the wheel is the 700 c Nimbus rim of my 29-er.

It's never been entirely true, and it's a close fit with the 2.1 tyre in a round Nimbus 28" frame; but it works without rubbing.

However it's got a couple of obvious wobbles that it would be nice to straighten out.

The wheel is shimmed (at the bearing holders), without which it would rub, but that's probably due to a slightly imperfect frame- I'm assuming that I should be able to get a true wheel with a shim in?

I'm OK with the right direction to turn the spoke key to tighten/loosen, and the basic theory.

I've located the wobble by a combination of spinning the wheel whilst holding a finger tip against it, and also a felt pen to mark the spots.

My problem is that at the point it's being pulled in, the relevant inner spokes are already too loose for my liking, and the outer ones too tight.

i.e. logically it's the exact opposite of what it should be!

In fact one of the reasons I'd like to get the thing truer is because of my concerns about the looseness of a couple of the spokes, but it seems I can't tighten them because it pulls the wheel further out of true.

Is it possible that the wheels a lost cause?

Should I take it apart and rebuild it (I hope not!)?

Obviously I've got options as, like I say, it's been this way for some time and seems to work ok; also I could take it to a bike shop.

But I thought I'd post this to see if anyone has had this can of illogical situation with wheel truing.

[onetrack]

when truing a wheel, I never looesn spokes. Since you have already loosened some of the spokes, I would take the tire, tube, and rim strip off. Then I would loosen all the spokes till they are all at the same tension. Now one by one gradually retension the spokes. Reply if you need/want more details.

mike

[onewheeldave]

At the risk of sounding naive, couldn't I get the same effect by just tightening the spokes I've loosened?

I'm concerned that if I loosen them all off I could end up with a mess that I can't fix, whereas at least now my wheels still functioning.

[tom_edmonds]

you should PM mike hinson, havent seen him online or on the forums for a while, buts he done a great job with the wheels es built and repaired for me, and seems to know alot about them

onewheeldave Wrote:
> the wheel is the 700 c Nimbus rim of my 29-er.
>
> It's never been entirely true, and it's a close fit with the 2.1 tyre
> in
> a round Nimbus 28" frame; but it works without rubbing.
>
> However it's got a couple of obvious wobbles that it would be nice to
> straighten out.
>
> The wheel is shimmed (at the bearing holders), without which it would
> rub, but that's probably due to a slightly imperfect frame- I'm
> assuming
> that I should be able to get a true wheel with a shim in?
>
> I'm OK with the right direction to turn the spoke key to
> tighten/loosen,
> and the basic theory.
>
> I've located the wobble by a combination of spinning the wheel whilst
> holding a finger tip against it, and also a felt pen to mark the
> spots.
>
> My problem is that at the point it's being pulled in, the relevant
> inner
> spokes are already too loose for my liking, and the outer ones too
> tight.
>
> i.e. logically it's the exact opposite of what it should be!
>
> In fact one of the reasons I'd like to get the thing truer is because
> of
> my concerns about the looseness of a couple of the spokes, but it seems
> I can't tighten them because it pulls the wheel further out of true.
>
> Is it possible that the wheels a lost cause?
>
> Should I take it apart and rebuild it (I hope not!)?
>
> Obviously I've got options as, like I say, it's been this way for some
> time and seems to work ok; also I could take it to a bike shop.
>
> But I thought I'd post this to see if anyone has had this can of
> illogical situation with wheel truing.
>
> A better way to see and fix this problem is to tape a piece of
> cardboard,a q-tip ,or anything to the fork that can be used to gauge
> trueness .Sometimes 2 or 3 spokes before and after must also be used to
> coax the wheel into round. Also make sure the LOOSE spokes or ajoining
> nipples are not stripped.


--
cheechee

"onetrack" <onetrack@NoEmail.Message.Poster.at.Unicyclist.com> writes:

> when truing a wheel, I never looesn spokes.

More power to you, but this is not an approach I'd recommend. I don't
believe you can get the wheel dished (centered), round, laterally
true, and at proper tension if you refuse to loosen spokes. To be
fair, It might seem like roundness isn't very important with a 2" tire
riding on top, but I just don't like the idea of an out of shape rim
and worry that you can't get even tension that way.

My approach to trueing wheels is to get a semblance of proper dish and
roundness at modest tension first, then approximate lateral truing
using equal turns clockwise and counterclockwise on adjacent spokes
(thus saving roundness). Now that the wheel is semi-true, I can get
it good and round (say within 1mm, closer if I'm using a dial gauge)
without bringing it out of true. Next comes fine-tuning of the
lateral trueing and dishing, followed by tensioning, tension
relieving, and final touchup. There's room for some improvisation in
the proces, but that's my basic strategy.

My point is that you can't keep the wheel round, dished, and true if
you don't loosen spokes during the wheelbuilding process.

Anyway...

If I were onewheeldave, I'd try to get rid of the shims. Unless the
fork arms are of different lengths, shimming the wheel to prevent
rubbing is the wrong solution. Here's what I'd do...

1. Measure the fork arms to make sure they are they same length. If
not, shim one of the bearing holders to make them the same.

2. True and dish your wheel. Use a dishing tool to be sure you got
it right. Don't worry about tension at this point. If you can't
get the wheel true with loose spokes on one side, you may need a
new rim (i.e. see a professional).

3. Now mount the wheel and make sure the frame is straight. The gap
between rim and frame should be the same on each side. If the
frame is bent, bend it back. I think there's an article on
unicycle.uk.com on fixing bent frames.

4. Now that the unicycle is straight, the tire will be properly
centered without any funny business that might put it offcenter
where it touches the road. Finally, you should finish truing the
wheel. Like I said above, I am careful about roundness as well as
lateral true and I'd be doubly careful to make sure everything is
just right on a difficult wheel like yours. So, bring up the
tension, keeping the wheel dished, round, and true.

Good luck.

Ken

[cyberbellum]

Originally posted by onewheeldave
the wheel is the 700 c Nimbus rim of my 29-er.

... it's a close fit with the 2.1 tyre in a round Nimbus 28" frame; but it works without rubbing.

Presumably you are shimming to give the tire room? If so, keep the shims or get a smaller tire.

If it's dished wrong then follow the above advice to get the dishing right and toss the shims. Bike dishing gages won't work, so you'll need to rig some sort of dishing tool or other means to measure the dish of the wheel.

Originally posted by onewheeldave
I'm OK with the right direction to turn the spoke key to tighten/loosen, and the basic theory.

My problem is that at the point it's being pulled in, the relevant inner spokes are already too loose for my liking, and the outer ones too tight.

i.e. logically it's the exact opposite of what it should be!

Sounds like you've got a bashed in rim. It's going to be virtually impossible to true until you re-round the rim. This is a dicey thing to do, so my advice is to buy a new, round rim.

To round the rim, mark the flat spot and de-tension the wheel. Get all the spokes nice and slack. You'll have to Rig up some sort of press. Good bikes shops have a tool for this, but most ordinary ones don't, so I would just get creative with a 2X4, some blocks
and a really big clamp. Try not to twist it when you pull it round. Then just tension and true the rim as normal.

Originally posted by onewheeldave

Is it possible that the wheels a lost cause?

Should I take it apart and rebuild it (I hope not!)?

If you don't mash that spot again it should last quite a while. It won't work all that well with brakes anymore, but it will be rideable.

If it were me I'd buy a new rim, tape it to the old one, transfer the spokes, then true and tension.

"cyberbellum" <cyberbellum@NoEmail.Message.Poster.at.Unicyclist.com> writes:

> If it's dished wrong then follow the above advice to get the dishing
> right and toss the shims. Bike dishing gages won't work, so you'll need
> to rig some sort of dishing tool or other means to measure the dish of
> the wheel.

What's wrong with bike dishing tools? I used one and thought I got it
right. If the bearings are not pressed on evenly, I'd measure off the
bearing surface (using a homemade spacer if needed).

Ken

[cyberbellum]

Originally posted by Ken Cline

What's wrong with bike dishing tools?

The dishing tools I'm familiar with are long, slightly bent pieces of metal with a sliding gage in the middle . You loosen the sliding part, set the frame onto the wheel with the two ends on the rim and the sliding part on the axle of the hub, tighten the set screw to hold the position of the sliding part, then flip the wheel over and check the other side. If all three parts touch exactly then the rim is dead center between the shoulders of the axle.

The ones I used to work with wouldn't have the range to cover a unicycle spindle. Then again, I'm an old fart and am familiar with 25 year old Campy tools. Perhaps the newer ones have more range in the sliding part.