daven1986

Hi all,

Just built my first wheel - it is an 8 speed 36 spoke 3x rear wheel. I have taken it for a test ride and made sure I hit a nice bump to see if it'd knock it out of true, but when I checked it, it was fine.

However I do feel that the spoke tension is low compared to other wheels I have (none are 3x though). Is it ok to ride it and just check for trueness occasionally or will I suffer catastrophic failure if the tension is too low?

The rim, hub and spokes are all new.

Thanks

Daven

greyghost_6

How low is the tension? Is this because the spokes you purchased were too long? You could tighten all the spokes starting with a quarter turn to see if that helps. Im sure you could probably tighten them up if you can easily squeeze the spokes at the cross easily.

dabac

If tension is too low the spokes will fatigue prematurely, usually one by one. This is rarely catastrophic in terms of sending you to the ground unexpectedly, but it's annoying and a waste of time and build material.

fietsbob

Hard to quantify relative tension with out calibrated tension gauge to put it in standardized numbers ..

You could remove the tire and put it back in the truing stand and give it another round of tension increase and dish re checking , If you think the tension is too floppy .

stress relive the wheel leaning on it hand ons the rim , axle against the floor .
all the way around , both sides , unloads the spoke tension a bit on the opposite side. and torque windup remaining in the spokes should be reduced.
then double check true-ness.

daven1986

Spokes are a good length, I could certainly tighten them up more. Will probably do this at the weekend - thanks

How do I know that I'm getting close to high enough tension?

davidad

If you are not using a tensiometer then use the overload method. Tension the wheel and then stress relieve it. (Take opposite parallel spokes and squeeze them). Continue adding tension and relieving until the wheel takes a warped state. Back off of the tension a 1/2 turn and stress relieve. Your wheel is finished.
I prefer the tensiometer because rim makers usuall have a reccomended upper limit on tension.
I tension to 110kg on 36 and 32 spoke wheels. LOwer spoke counts require higher tension.

Al1943

It is unlikely that you'll get them too tight.

Check to see that the rim is centered. Reversing the wheel on a truing stand is a good way to check.

On a multi-geared rear wheel the non drive side spokes will have typically about 60 to 63% as much tension as the drive side.

Be sure your spoke wrench holds all 4 corners of the nipples firmly so that you don't round the shoulders off.

Squeeze adjacent spokes to compare tension with someone's custom built 3X wheel.

At about $60 a Park tension meter is a good investment.

daven1986

I am probably going to buy a tension meter when I go to New York - August! The rim is centred correctly, and is very true laterally and vertically. I think I'll give them 1/4 or 1/2 a turn all round just to make sure

mrrabbit 

To test for a clear case of OVERTENSIONING:

1. Mount tube and tire.
2. Inflate to normal pressure.
3. Spin the wheel and observe.

If it goes out of true in a rather well defined s-wave fashion...

1. Deflate.
2. Remove tire and tube.
3. Spin the wheel and observe.

If it seems to have returned to a relatively true state...then you have too much tension and need to back off a 1/4 or 1/2 turn for starters.

=8-)

Al1943

I don't think that is a conclusive test.
Raising the pressure reduces the tension of all spokes and the rim will move slightly toward the drive side, whether over tensioned or not.

In the first place, the final lateral truing needs to be done with the tire mounted and tube fully inflated to riding condition. After all, that's how you're going to ride the wheel.

I do agree that an overtensioned wheel can develop a sin or "S" curve, and this can show up in the brake wear pattern on the rim, with the drive side spokes on the convex side of the "S". I've seen that more than once.

Retro Grouch 

Take a wheel that you are confident about - borrow one if you have to. Test the spoke tension with your hands - listen to the musical note the spokes make - whatever. Try to mimic that in your new wheel.

I own a Wheelsmith tensiometer and I use it but lots of perfectly adequate wheels were built before budget priced tensiometers came into common use. This ain't rocket surgery.

mrrabbit 

Notice the qualifier "clear"...

Have been using that test for over two decades...been extremely reliable. It is also a very reliable test to determine if a rim that has had years of miles put on it is fatiqued or not. A fatiqued rim whether it is overtensioned, properly tensioned, or slightly undertensioned will do the same when the tube is inflated to normal pressure. When a rim is fatiqued - while the spokes and hub are still up to the job - it simply doesn't have the base strength to resist the forces being put on it anymore in an stable and equalized/balanced manner.

(Of course, we're talking steel and alloy rims here...)

The result is similar with an overtensioned wheel - the rim is being asked to do too much and and the s-wave that results simply exposes the unstable result that has occurred.

With a wheel that is slightly overtensioned...(in the 120-130 kgf average range) it won't be so obvious.

What I offered to the OP was a test for a "clear" case of an overtensioned wheel. Otherwise as many have already noted - a tensionmeter really helps for all else.


Of course, as you and Operator already know - I'm more concerned about undertensioning which is the more common gremlin and source of most spoke issue wheel related threads here at BF.

Nice chatting with you as always...


=8-)

Al1943

mrrabbit,

If a wheel goes out of true by pumping the tire and tube up to riding pressure what it means to me is that the wheel wasn't true to begin with. I always do a final lateral true and dish (rim centering) with the tire and tube at full riding pressure.
I agree with the rest of what you have said.

Cheers