Our tech experts walk you through fitting a cableoperated dropper post, give you the lowdown on coil shocks and answer queries about tyre pressures, lenses and looking after cleats
Your questions answered
FEEL THE PRESSURE
I’m wondering whether you have any hard and fast rules for getting tyre pressures spot-on. I usually just stick some air in and hope for the best!
Mark, Gower
It’s difficult to recommend a specific tyre pressure as it depends on a host of variables – your weight, riding style, tyre carcass, rim width and tyre size, for starters. We can give a few pointers to help you, though. It largely comes down to feel. If the pressure is too low, when you hit corners you may feel the tyre ‘roll’ on the rim, giving a vague feel, and on the flat when pedalling you may get a little bounce going on (if you can separate that feeling from any rear suspension). It’ll also feel squirmy and vague over rocks and roots, and you may notice jolts as the tyre gets squashed so much that the impact transmits through the rim. If the pressure is too high, you’ll feel the tyre pinging off rocks and roots, and the bike won’t feel composed on rougher tracks. In corners you may struggle to hold a line – in carspeak, it’ll understeer.
Our tech ed Tom weighs 76kg in riding kit. The rims on his long-term bike are 30mm wide (internally) and fitted with 29x2.4in tyres with tough casings. With that set-up, he runs 22psi at the front and 24psi at the rear, on mixed terrain. If you have narrower tyres and/or rims, are a few kilos heavier or ride mostly rocky or bike-park-style terrain, you may want to add a couple of psi. On muddy rides or with 2.6in tyres, you’ll likely want to drop the pressures slightly.
There’s no golden rule – it comes down to experimentation and working out what works best for you. Getting a decent digital pressure gauge is a good shout, as is taking notes of the changes you make and where you end up.
LENS TECHNOLOGY
I’m thinking about treating myself to some nice riding sunnies this summer, probably Oakleys. Are their Prizm lenses polarised?
Steven, Rochdale
There’s a difference between a polarised lens and Oakley’s Prizm technology (and equivalent tech from brands such as Alpina and Smith). Polarised lenses feature a chemical treatment or coating in which the molecules are arranged so that lightwaves that hit the lens horizontally are blocked out, while vertical lightwaves are allowed through. This helps darken what you see, by reducing light transmission, and also cuts out glare, such as from a puddle on a sunny day. It can also help make things crisper, as there’s less ‘noise’ distorting what you see. However, polarised lenses
can block light from LCD screens (such as your car dashboard) and can make seeing phones and smartwatches trickier.
Oakley’s Prizm lenses (and similar) use dyes to emphasise the colours they think you need to see in certain situations – hence the various Prizm lenses for different applications. The Prizm Trail lens, for example, is designed to boost reds and browns, as well as make greens more vivid. Oakley say that the mirror tint on the outside of the lens is there to reduce glare, as not all Prizm lenses are also polarised.
CLEAT CARE
Following your pedals grouptest last month, I’ve bitten the bullet and bought some SPDs. Any tips on keeping the cleats in decent condition – they must be in the firing line of all sorts! Tom, via email
Good luck with your new pedals, Tom. Cleats are fairly hardy things, but they will wear out eventually. They’ll feel loose in the pedals and start making clicking noises as you pedal if they get really bad. Thankfully, they’re relatively easy and cheap to replace, so this isn’t the end of the world – although it can feel like it when you’re trying to get them off your shoes! When you first fit them, it’s a good idea to use grease or an anti-seize compound on the Allen bolts. The bolt heads can also fill with dirt – I scrape them out with a small Allen key periodically, as you want full engagement to avoid rounding the head. Some people even fill the bolt heads with a smear of silicone sealant or some candle wax to help prevent this. Otherwise, keep the area around the cleat clear of dry mud, grit and stones, as these can impede clipping in and out.