STIFF COMPETITION

Just how stiff should a wheel be? Reynolds product director Todd Tanner has the answer

‘In a wheel there’s radial stiffness [the ability for a wheel to stay circular under load], lateral stiffness [the ability of a wheel not to fold] and torsional stiffness [the ability of a wheel to not twist under forward drive],’ says Reynolds’ director of product development, Todd Tanner. ‘People talk about making a wheel “stiffer” by increasing spoke tension, but tightening spokes beyond what is considered a normal tension [eg factory tension] makes no detectable difference. The biggest factors in stiffness are spoke number and rim stiffness. More spokes and a deeper rim profile usually mean a stiffer wheel all round.

‘The confusion is that a deep rim wheel can often rub on the brake pads, and that means a flexy wheel, which is bad, right? Not necessarily. A bit of vertical and lateral compliance in a wheel can be good – it’s more comfortable and tracks bumps in corners instead of skipping over them. But moreover, just because your wheel rubs when you climb out of the saddle doesn’t mean it’s not stiff. If anything it’s because it’s so stiff, or at the least the rim is. A shallow profile wheel will bend slightly at the bottom under side load, leaving the top of the wheel where it is. But a really stiff rim won’t yield so instead the hub, spokes and thus the frame will move across to meet the rim, and you get brake rub.

‘It’s therefore a balancing act. A wheel that’s very stiff vertically will be strong but uncomfortable, and a wheel that is very stiff laterally and torsionally will accelerate crisply but might not track the road so well through corners, and might rub on the brake pads. It’s all about purpose. When we used to race downhill mountain bikes in the 1990s we’d slacken our spokes to the point where the wheel was almost ready to collapse. We’d sacrifice precision and longevity, but gain vertical compliance in order to try and prevent pinch flats, which would be game over.’