csport

Hi
I have recently rebuilt the rear 32H 700c wheel on my Bianchi hybrid because of upgrading the hub from Shimano RM-30 to Deore T-610. The rims are Alex SSP220, double wall. The bike is Bianchi c-sport 1, it is similar to Trek FX or Specialized Sirrus series. I am 250 lbs. I would be greatful for any advice on the DS/NDS spoke tension. I have seen some people saying not go beyond 110 kgf DS.
On the other hand, a LBS my friend bought another bike from (one of the few LBS's which actually do tighten the spokes when assembling the bike) has tensioned them to 150-160 kgf DS rear and 110-120 kgf front. Is it too much? The latter bike is Bianchi Torino, a city hybrid with 36H 700c wheel and rims slightly wider and heavier than mine.
Is about 120-130kgf on the rear DS typically acceptable? I am going to ask LBS as well.
Thanks for any help.

sstorkel

It all depends on the rim! Most of the rims I'm familiar with suggest 110-120 kgf as the maximum spoke tension. 150-160 kgf sounds quite high!

You can use the DT Swiss Spoke Calculator:

https://spokes-calculator.dtswiss.com/en/

Or Damon Rinard's spocalc spreadsheet:

Damon Rinard's free spoke length calculator

To figure out what the NDS tension should be based on the DS tension.

csport

Thanks for the reply! I have visited the LBS today, and the reading of their TM-1 is lower than that of mine by 0.5 to 1 unit (e.g., 24 where I have 24.5 or 25). Good to know as it means that my TM-1 is on the safe side. They have confirmed that the maximum is about 120 kgf (which means up to 25 is OK with 2mm spokes).

FBinNY 

If you haven't rebuilt yet, you might consider using DB spokes, at least on the left flange.

Optimal spoke tension includes a number of considerations, including what the rim can tolerate. One of the most important ones is how much the spoke is stretched under tension. As the rim deflects under load, the spoke is stretched less and loses tension. It can only function while under tension, and once it loses tension down to the relaxed state it can't contribute any more.

So, you have options. You can use a deeper rim, which deflects less under radial loads, or you can use a thinner spoke where the tension won;t be as high, so it stretches more, and can continue to contribute as the rim deflects (or both).

You are capped on left side tension at 50-60% or so of right side tension, so assuming 120kgf on the right, you're looking at 60-70kgf on the left. A lighter spoke will make that tension adequate whereas it might be low for a heavier spoke. That added stretch under load is the real (and most misunderstood) benefit of butted spokes, and how when it comes to wheels, less is often more.

GravelMN

Agree that 150+ is too high. My DS with butted spokes and double-eyeletted rims run 115-120. Front is 100-105. I weigh about 230# and have had no problems at these tensions.

sstorkel

The other option for increasing tension on the NDS is to look for rims with an offset drilling. I used Velocity's Synergy OC wheels for my touring bike, which have a 4mm offset. On the rear wheel, NDS tension was 84% of DS tension. Sadly, the Synergy OC has been discontinued, but I believe Velocity is still selling an OC version of the A23.

chaadster

It has been addressed, but I think it's worth stating plainly that spoke tension is not to do with rider weight.

csport

Thanks for the advice. I have already rebuilt, using the same rim and spokes (they were practically new, with about 300 miles on them). This was my second build. The first one was when I was trying to true and old MTB wheel without much success (anyway, the rim was bent). I am going to use the different spokes if I do a build myself some time in the future.

FBinNY 

Not true. Rider weight is a consideration, though not the major one. Heavier riders mean more rim flex, and so must be considered in choosing rims, spokes, and tension. With wheels, as with any structure, dead load (unloaded), payload, and dynamic load must be considered in deciding what's required.

If using the same rim for a light and heavier rider, I'll tension the heavier rider's wheel closer to or even exceeding the rim makers tension limit, while leaving more upside room for the lighter rider to spare the rim the stress of a high dead load.

chaadster

Yes, heavy riders can benefit from higher tension, but I meant simply to say that rider weight does not dictate DS/NDS tension variance as seemed to be expressed in the OP.