Tuesday, July 9, 2013

DIY Aero Wheel Cover Tutorial

For the bike leg of a triathlon, AERO (aerodynamics) is KING. Aerodynamics affects everything from water bottle placement on your bike to the type of wheels you use when racing. Hell, I purposely have a triathlon jersey that I race in that is one size too small, so I know it's not going to be flapping in the wind, slowing me down.

Since I got my new bike, I've been really considering everything I could do to make my bike even more aero.  I've purchased an aero race helmet (and look like an alien), taped down wires and cables to hide from the wind, and have removed a saddle bag.  I've been scouring forums on Slowtwitch for ideas to make my Cervelo aerodynamic and light (weight is important, too). And I found my next idea: a disc wheel cover.

Disc wheels in general help you ride faster. I don't know how, or care.  All I know is you ride faster with a disc.  Now, carbon disc wheels are crazy expensive... To get around the insane price tag, there are wheel covers that you can place on your existing training wheelset. They are still around $115, but MUCH more affordable.  This still wasn't good enough for me.  I wanted to make my own custom wheel cover.  And after exploring TONS of forum posts on how to best do it, I started my process. And here's how you can, too!

The soon to be "disc"

What you'll need:

  • Rear Wheel (mine was my training wheel with 30mm depth rims)
  • Blue Painter's tape
  • 2 ABS plastic discs precut to specified diameter (more on this)
  • 1.5 inch circle drill bit
  • ABS Cement (usually found near plumbing supplies)
  • Scotch 3M 33+ Super Vinyl Electrical Tape 
  • Rubbing alcohol
  • duct tape
  • utility knife
  • about 2 hours

To start, you'll need to find someone that has ABS plastic, preferably .04 thickness. The best I could do was .05 thickness at Regal Plastics in Kansas City. I wanted a bit thinner, but they cut the sheets into circles for me, which saved some time. Since my wheels have a 30mm rim on them, I measured to see what the diameter of the circle should be, and thought 23 inches would be fine.

After getting the discs, I was ready to get going. 

First, cut a hole in the EXACT center of each disc using the 1.5 inch circle drill bit and drill.  The plastic cuts incredibly easily, so if you don't have a drill, you may be able to use a utility knife.

After the the circle holes are cut, you will now need to cut a straight line along the radius of the disc. 

Be sure the disc fits onto your wheel before 'dishing'

Once the radius of each is cut, you now lay the disc on you wheel (with the cassette and quick release removed) and tape the disc down on the wheel.  You will notice that there should be a bit of overlap of the plastic.  Tape down the seam with the painter's tape, and cut the extra plastic off using the utility knife. Doing this wheel create a completely flush disc, and now should also resemble a somewhat "dish", ie not completely flat.

This was all I removed from each. Depending on your wheel size, it might be more...

Now you need to bond the seam back together.  Put the cut disc back on your wheel and retape it again with the painter's tape.  I made sure to do multiple layers, as I didn't want the cement coming through.  Once taped, just apply the cement and let it dry for a few hours.

After the cement dries, it should look like this:

Nice and strong seam
You may also be able to see the "dish" aspect to the wheel cover:

Now all you need to do is tape it to your rim! Start with the drive side (side with your chain and derailleurs). Tape down the cover to your spokes using duct tape, as this prevents the disc from rubbing on your cassette once you reinstall it.

Overkill with the tape. 
Next, clean the wheel cover and rim with rubbing alcohol, as this creates a clean surface for the electrical tape. Lastly, apply the electrical tape, being sure to not stretch the tape AT ALL while you apply it.  I unraveled the tape about 8 inches, let the tape relax, applied the tape, unraveled more, let it relax, applied more, etc... until the wheel cover was fixed.  

Eventually, you'll be done with the drive side.

The last step is to do the same to the other side, but you won't be able to duct tape the wheel cover to the spokes.  

And you are done! It probably cost me $40 to make, but I did need to buy all the tapes and rubbing alcohol, which may be more common household items.

All in all, this process isn't too difficult. I don't consider myself a big DIYer (my future father in law will attest to this).  But I was able to get it done in a reasonable amount of time! 

Pure aeroness

Taping is the most important part, and is probably the part that scares me the most, as I don't want my cover coming off at 30mph. So far, I've put almost 100 miles on the disc, including a 45 mile ride this weekend in the rain and had no problems.  I do feel the extra weight on hillier routes, but I still think the  aero benefits outweigh (not literally) the extra weight of the wheel.  I now feel comfortable with the tape job. 

Also, I have noticed ZERO changes in my handling, despite riding in 15-20mph headwinds, crosswinds, and tailwinds.  I think the handling difficulties with a disc wheel is kinda bull, as all your weight is under the rear wheel. The front wheel is probably more important for handling in the wind...

I plan on racing it this weekend at the Shawnee Mission Triathlon, and will let you know how it holds up!

Hope this tutorial helps! And if you have any questions, just leave a comment!

Thanks for reading, #trilife


Ryan Falkenrath said...

So... how long did it take to make? You have to factor in time and wages to account for the cost of making a wheel. Time is money. ;)

Interested to see how it holds on the chip seal to the "dam hill". They need to repave that section asap.

I expect this will nab you the illusive AG 1st place after 2nd for two years running.

Mark said...

It was probably an hour of actual work, and 2 hours to let the cement dry. Thus, about 3 hours...

Yeah, I have ridden it at SMP a few times already and it's held up fine. Although I don't know if the hilly course justifies the extra weight. But yeah, I'm racing with it regardless...

Cory Michie said...

Just came across this and am thinking about making my own, do you think .06 ABS plastic will work?

anthony hay said...

Great Info! Do you have any updates on longevity? How many miles do you have on it now?

Harper smith said...

This blog is really very good and very educational. I really enjoyed reading every bit. Thank you for sharing. carbon fiber bicycle frame