A word on wheels…

Howdy

Was out on a ride this morning (it’s the middle of summer down here in New Zealand) and was at the back of a biggish bunch when a heard a loud BANG – and then had to take evasive action as a rider in front was obviously struggling to control his bike – and get it to a stop.  Ended up in the grass on the side of the road – no harm done.

Turns out – he’d broken a spoke on his rear wheel – and the wheel was so badly buckled that it wouldn’t turn without rubbing hard on the frame – so it was completely unridable.    Nothing to be done – but to get the cell phone out and get someone to pick him up.

But it got me to thinking about spoke counts and heavy riders…  Not that he was heavy – pretty tall but was a skinny Swiss guy.  But he had a low spoke count and one of those lacing patterns where there are 3 spokes close together – then a good sized gap – then another 3 etc etc…  He told me that this was the third time he’d broken a spoke with the same result each time.    He looked like a pretty handy rider too – which was lucky – as a lesser experienced rider might have gone down – and taken others down too – which would really have spoiled our Boxing Day ride…

As I’d stopped – we got to talking and he looked me up and down and asked if I’d had problems with broken spokes.   (I’m 198cm and 127kg – so I guess I looked like a likely candidate).  But I was happily able to answer him – that I used to break spokes (and frames) regularly- but since I’d had my Zinn bike and the wheels that they put together for me – I hadn’t broken a single spoke in 3 years and a lot of kms.

For someone my size – this is a big statement! (especially since I race on the bike a lot and I only have the one set of wheels – so they are my racing/training/commuting wheels)

When I bought my bike – my brief was something like “give me the best and most robust wheels you can for around $400 ” (this was all the budget would allow)  I knew that they specialised in big bikes and big riders – so I put my trust in them.   What they put together has been absolutely bullet proof.  DT Swiss TK 7.1 36 hole rims (front and back)  laced up to 36 hole Ultegra hubs.  And they have just been outstanding.

The only time they’ve ever had to be looked at – was when I got involved in a coming together on a descent – and ended up riding down a ditch at fairly high speed – and the net result of that was the slightest of buckles in the rear wheel – that was fixed at the local bike shop in a jiffy.  ( the other guy on the other hand went over the handlebars and snapped his forks in two!)

As I said – they are my everything wheels – race/train/commuting – and they haven’t missed a beat.  And that is hugely confidence inspiring…   I know now that I can get out of the saddle and sprint or climb – and that nothing is going to break.

Anyway – that’s my observations and experience from 3 years with a set of wheels that Zinn Built

Boxing Day in NZ.

29er Wheel strength for Big and Tall Riders

This is from the last issue of our Quarterly Newsletter

As essentially all of our mountain bikes for years have been 29ers, and as the vast majority of our customers are taller than 6’4″ and well over 200 pounds, we at Zinn Cycles have a lot of experience with 29er wheels for big riders.

The quality of the build is critical, and the rim, spokes and spoke count must be chosen appropriately for the rider. Due to availability, prior to 2006 or so we only used 24mm-wide road trekking rims of around 550 grams, namely Mavic A719 and DT Swiss TK7.1, and we only built 36-hole wheels for big riders. However, those rims were insufficient for 6’8″, 250+-pound North Shore riders who had problems with pinch flats on such narrow rims, as the available tires only had thin, cross-country casings. For these riders, we use Kris Holm Unicycle.com rims, which are 38mm wide and around 900 grams, reducing pinch flats and wheel failures, even off of big drops with big riders. There are also now some other in between options for all-mountain 29er rims.

While higher spoke tension makes the wheel neither stronger nor laterally stiffer, it is usually necessary with larger rider size to avoid so much deformation of the wheel while rolling that the bottom spoke becomes completely de-tensioned, leading to nipple loosening and rim and spoke fatigue. The lifetime of the wheel is higher with more uniform spoke tension, and a professional wheelbuilder with a lot of experience can give you that.

While I believe that you can trust most of the name-brand pre-built wheels to be safe, most of them will have too much lateral flex for a big rider to be able to sprint confidently or steer precisely on sharp downhill turns at speed. Fatigue will also be an issue; the rim will develop small cracks at each spoke hole on the rear wheel, often just after the 6-month warranty has expired, and spokes may break as well. This is a common problem we have seen from bigger riders before we set them up on a custom built wheel.

I believe that a big rider with an aggressive riding style ought to not buy factory pre-built 29er wheels at this stage in their development. In 26ers, there’s a wide range of pre-built wheels made for downhill, freeride, and all-mountain, but most pre-built 29er wheels are made for cross country, which won’t cut it for a big dude.

For big riders, I recommend through-axle hubs in both the front and rear. 20mm, 9mm, or QR15 up front and 10mm or 12mm in the rear. The nice thing about the 10mm through axle, is that it can be used on a standard quick release dropout. The 10mm axle fills the entire space of the dropout providing much better dropout support. Both ends will track better by virtue of the stiff axles tying the fork legs and swingarm members together, and the rear through-axle will prevent the hogging out of the right rear dropout that can happen with a big, strong rider under high torque in low gear. You will know about this if you cannot keep your rear wheel from pulling over to the left chainstay, no matter how tight you keep your quick-release skewer.

Secondly, I would recommend high spoke counts – at least 32, and preferably 36, with high-quality, double-butted 2.0/1.8mm (14/15-gauge) stainless steel spokes with (brass) thread-locked nipples to prevent them from loosening up (we use DT Competition spokes with DT Pro Lock nipples). The stretchier, double-butted spokes make for a longer-lasting wheel than would straight-gauge 2.0mm (14-gauge) spokes of the same quality. As the spokes stretch, they move some stress concentration from the weakest points at the elbow and nipple, and the nipples stay in contact with the rim under high wheel deformations (often occurring under somebody big), reducing rim fatigue.

The Mavic A719 has been replaced by the TN719 disc-brake specific rim, and the DT TK7.1d is also a disc-brake version; these rims are narrower than I think is ideal for 250+-pound riders, but they are plenty strong if built up well with 36 spokes and through-axle hubs and make for a light, fast wheel for riders under 250 pounds. For aggressive riders over 220 pounds, I would recommend 27-30mm-wide all-mountain rims, like Halo Freedom 29, Sun Ringlé MTX 29 (585-gram) or Equalizer 29 (540-gram), or, for riders over 250 pounds or for getting air, Kris Holm 34mm-wide rims are the best option.

For pre-built wheels, if the rider is under 200 pounds, and especially if running tubeless tires, the Mavic C29SSMax is a great wheel and is available with a front through-axle. For riders over 200 pounds, I’d recommend the Sun Ringlé Charger 29 with the 20mm through-axle option. It has the narrower and lighter (27mm, 490-gram) Equalizer 27 rim and 32 spokes, but it should still hold up very well as long as you’re not doing a lot of hucking.

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