Surly Pugsley – 29er / 700c wheels

When buying my Pugsley I knew from the very start that I would build a light set of 700c wheels for it. Fat is rad, doesn’t mind snow, sand or boggy moorland (at least some of it). Yet most of the time fat tyres aren’t 100% necessary and I wanted to have a light & fast option. That’s not to say that Larrys are utterly useless on tarmac – they’re not.

Pugsley’s frame theoretically allows to enjoy both of the camps. The 135 mm OLD, which – contrary to the new 170 mm symmetrical fatbike standard – allows for use of common (cheap) parts, encourages experimenting. Building a well balanced wheel is certainly easier with a symmetrical 170 mm rear hub, but the price difference is enormous – not to mention (non)availability in certain European countries.
This doesn’t imply that building a strong 700c wheel for a Pugsley is all roses. The 17.5 mm frame offset means that by using a standard rim with symmetrically spaced spoke nipples, one’s on a straight way to a weak wheel. It’s not going to take abuse very well.
To illustrate this, it’s best to revert to some Freespoke calculations (note: the asymmetrical frame is a 17.5 Pugsley offset frame).

Symmetrical frame:
Velocity Synergy + Shimano XT M756 
Asymmetrical frame:
Velocity Synergy + Shimano XT M756 
From the above pictures, it is clear that the spoke tension distribution for an asymmetrical build comes up a lot worse, meaning a weaker wheel.  To compensate for this, the spoke attachment point to the rim should be offset to the drive side of the wheel. That’s where offset drilled rims come into play. Incidentally such rims can be used to build a stronger “symmetrical” wheel – as per it’s original purpose, before fatbikers and their problems came into play. Unfortunately  in recent years, the number of companies offering offset drilled 700c rims shrunk considerably. I was able to track only one manufacturer still producing those. Velocity offers it’s Synergy rim in a 4 mm offset drilled version. Surly recommends anything between 6-12 mm, but this will have to do.

Asymmetrical frame:
Velocity Synergy OC + Shimano XT M756
Spoke tension has improved a lot in this case, but it can be improved even further. SRAM offers rear hubs having a Hi/Lo flange construction. This means one of the flanges has a bigger diameter than the other, thus improving spoke tension distribution. Again, a solution meant for standard bikes comes to the rescue of fatbikers – can one still call himself that, running 32 mm “razor blades”?

Asymmetrical frame:
Velocity Synergy OC + SRAM X7

A comparison reveals that such a wheel is very similar (spoke tension wise) to the first build shown here (Symmetrical frame using Velocity Synergy and  Shimano XT M756 hub). There is but one difference, the higher tension spokes are now on the non-drive side of the wheel, where the disc brakes are.

During the weekend I got the chance to put this build to the test. Saturday I received my last parts and by the evening I had a complete wheel spinning in the dropouts before me. Sunday was spent on a 70 km test ride along the Welsh countryside. Tuesday I did another 50 km commuting to work. That allows for a good first impression as to the characteristics of such a build and Pugsley’s roadie-ability. I must say I’m very pleased with the results. Such a drastic change in rim, tyre and tube configuration made a tremendous impact on the bike’s handling. Pugsley proved itself as a fun to ride, fast and agile road bike – it doesn’t feel any different on the road than my symmetrical bikes. As a matter of fact I feel it’s faster than my Fargo with the same tyres – but that most probably comes down to the Fargo having a 2×10 drivetrain with lower gearing. The question that still remains open is the wheel’s strength and reliability.
This is how things look like in the real world:

It doesn’t get more
asymmetrical that that!

To sum things up. A Pugsley owner is a person, who bravely faces problems not occurring with other bikes. Thanks.

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