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Time Trial Postioning: Bodies and Equipment
- By Steve Hogg
- Published 01-May-08
- Time Trialing
- Unrated
Aerodynamics
Aerodynamics is one of the most powerful marketing tools in the bike industry. There is often a message to the effect that speed can be purchased by having the right wheels or aero bars or helmet or whatever. To some extent this is true but equipment will not make up for lack of training and application.
Reducing frontal area and smoothing the flow of air over the rider is important and anyone who is half serious should use aero bars and a tightly fitting skin suit. A reasonable substitute for a skin suit is a snug fitting jersey tucked firmly into knicks.
Probably the next most important thing is aero wheels. You could be excused for thinking that every manufacturers aero wheel is more aerodynamic than every others manufacturers’ aero wheel when you read all the adverts but as a rule of thumb, choose wheels that have a depth to width ratio of 3 to 1 or greater. This includes the tyre, meaning that if using a 20mm tyre, try and use a rim of 40 mm or more depth. The 40mm deep rim and 20mm diameter tyre give a total height of 60mm which is 3 times the width of the tyre itself. Less spokes of aero section is good and a rear disc is ideal if the budget will stretch. If you compete on a windy course, sometimes it can be faster to sacrifice a bit of rim depth on the front to be buffeted less by side winds and hence spend more time driving the bike hard and less time just trying to stay upright on it.
There is no point in having fast wheels if using slow, dead tyres and tubes. In clinchers the fastest TT tyre out there at the moment is the 130 gram Veloflex Record. These don’t like glass strewn roads but cope with coarse blue metal road surfaces well. An honourable mention also goes to the Continental Supersonic in 18 or 20mm width.
Once you have these things, you can pay attention to the smaller things like TT shoe covers which are like tight fitting non insulated booties. Standards approved aero helmets are available from several manufacturers but come at a price. Some things that you can do at no cost other than a little time, is to make sure that cables are tucked in as much as possible, quick release skewer levers are positioned horizontally rather than upright and that unnecessary bidon cages are removed for the event.
Reducing frontal area and smoothing the flow of air over the rider is important and anyone who is half serious should use aero bars and a tightly fitting skin suit. A reasonable substitute for a skin suit is a snug fitting jersey tucked firmly into knicks.
Probably the next most important thing is aero wheels. You could be excused for thinking that every manufacturers aero wheel is more aerodynamic than every others manufacturers’ aero wheel when you read all the adverts but as a rule of thumb, choose wheels that have a depth to width ratio of 3 to 1 or greater. This includes the tyre, meaning that if using a 20mm tyre, try and use a rim of 40 mm or more depth. The 40mm deep rim and 20mm diameter tyre give a total height of 60mm which is 3 times the width of the tyre itself. Less spokes of aero section is good and a rear disc is ideal if the budget will stretch. If you compete on a windy course, sometimes it can be faster to sacrifice a bit of rim depth on the front to be buffeted less by side winds and hence spend more time driving the bike hard and less time just trying to stay upright on it.
There is no point in having fast wheels if using slow, dead tyres and tubes. In clinchers the fastest TT tyre out there at the moment is the 130 gram Veloflex Record. These don’t like glass strewn roads but cope with coarse blue metal road surfaces well. An honourable mention also goes to the Continental Supersonic in 18 or 20mm width.
Once you have these things, you can pay attention to the smaller things like TT shoe covers which are like tight fitting non insulated booties. Standards approved aero helmets are available from several manufacturers but come at a price. Some things that you can do at no cost other than a little time, is to make sure that cables are tucked in as much as possible, quick release skewer levers are positioned horizontally rather than upright and that unnecessary bidon cages are removed for the event.
