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I thought I would share with everyone how I managed to beat several PR’s (that I’ve never managed to better) by riding a bike that cost me only £500.
I live not far from an A road that offers a totally flat 4-mile ride to a roundabout. The round trip of 8 miles is a good testing ground for a 10mile TT and I would often ride to this stretch of road, tackle the ‘TT’ and ride home after work in the summer (it’s good for a hard effort when I’m short on time!).
I set PR’s in each direction (and over the whole route) on one such ride last summer on my Canyon Ultimate CF SLX Disc 8.0 – this bike is by no means a slouch, 47mm Mavic Cosmics and aero integrated bar and stem – really a fantastic ride!
Over the past 8 months, I’ve taken 10 attempts to beat this, but all have failed! In the last couple months, I’ve been lucky enough to get involved in R&D testing of bicycle wheels as well as developing bicycle component fairings. This got me really interested in seeing how much faster I could go on an aero bike.
Long story short, I bought a 2006 Specialized Transition Comp frameset on Ebay and I adorned it with second-hand components.
Here’s a full break down of the components
Components I bought;
- Felt Bayonet Aero Bars & Brake Levers –£30*
- Durace Ace Shifters £60
- Stem & Shims £15
- Elite CX Crono Bottle £16
- Frameset £200
- HED Trispoke & Conti Tub £135
- Mavic Rear Wheel £40
- Conti GP TT Tyre £40
- Vittoria Latex Tube £6
- 105 Brakes £30
- Garmin Mount £2
TOTAL £514
*I bought the Felt Bayonet bars with brake levers and Vision TT shifters for £30, I cleaned up the shifters and sold them on for £60!
Components I had spare
- Ultegra/105 BB £15
- Fizik Bar Tape £0 (saved from the bin having been taken off another bike)
- Look Keo Pedals £20
- 105 Cassette £15
- Ultegra 6800 Front Mech £15
- Ultegra 6800 Rear Mech £20
- Ultegra 6800 Crankset £150
- Ultegra Chain £15
TOTAL £250
I made the rear disc using nothing more than some 0.5mm plastic sheet cut and dished to the right size.
I ride using HRM and feel, following a series of turbo trainer rides I gingerly tested the TT bike on my usual flat route. I took it fairly easy at around 80% of an all-out effort, incredibly, I knocked a full 2 minutes off the 8 mile route.
I’m surprised! A bike that cost me just over £500 was 2 mins faster on an 8 mile circuit than my Canyon which cost several times more! The power of aerodynamics, I assume.
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Tell us more about this plastic sheet – rear wheel. The Mavic decals give it that pro finish; “home made; really?”Looks awesome. I too am intrigued by your plastic sheet shenanigans.
Haha, I didn’t expect this thread to get much interest, to be honest!
I CAD modelled the initial wheel (a second hand super cheap Mavic Kysrium) before CAD modelling the same rear but with a disc covering the spokes.
I put both the CAD models into ANSYS CFX and ran Computational Fluid Dynamics on each model (I did a mesh study, inflation layer and all that other fun stuff, if anyone wants to challenge the validity of the simulation!). I’ve calculated a drag reduction of around 5 watts at 25mph with 0° yaw angle (I haven’t tested any yaw angles).
In the CFD, the increased vorticity and flow separation are clear for the shallow rim when compared with the disc – hence the drag saving. (The skin friction was much greater for the disc and the boundary layer was able to grow much larger and become turbulent, but even so, the disc was still better overall due to less flow separation).
I used the CAD model to create drawings of the disc wheel and calculate the dimensions and the angle of the cut needed to dish the wheel properly. I purchased some really cheap (cost me about £7) 0.5mm styrene sheet and scored the circle needed to create the wheel, cut the angle for dishing it, bent it together and glued it.
The Mavic stickers came in the box of goodies with my Canyon, seeing as the wheel I used was a Mavic, I thought I’d stick a couple on!
All I did then was put the covers over the wheel (the non-drive side is secured on the inside with tape and the drive side fitted beneath the flange next to the freehub so was held firm) then used electrical tape to secure the outside to the rim.
It sounds incredible above about 20mph, combined with the trispoke up front it makes the bike sound like a helicopter (somewhere between a Chinook in the distance and a [hovering] V-22)
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