You pretty much listed the options in bang-for-buck order. Here is my rough-order-of-magnitude listing of performance upgrades and what they could get you in a 40K TT. This is not perfect, but it does give you a directional sense of what you might gain and what it would cost. It is roughly ordered by cost per benefit

1. Aero Helmet - $100 - 1 minute
2. Clip-on Bars - $250 - 2 minutes
   
3. Fast tires & Latex Tubes - $120 - 1.5 minutes
4. Skin Suit - $250 - 2 minutes
5. Wheels - $1,200 - 1 minute

Edit: fixed the time savings to 40K from 112 miles...

I assume you already have good race wheels for the road, so getting a disc and possibly deeper front wheel is one of the worst bang for your bucks you can get.

Depending on what bike you have, you could potentially clip on aerobars, swap in a low rise stem, swap seatpost and saddle for a more forward position and split nose saddle.
You would need to play around a bit to figure out that fit conversion, but that’s probably your best bet for easy swapping between TT and road race setup - especially if you do a morning a TT/afternoon road race type of day.

Then, a solid aero helmet and good fitting suit. That will get you to 90% of the full blown TT racers in the field.

---

Alex Arman

Strava

just buy a cheap used TT bike and be done with it.

Search my username in this forum, I have a thread going.

I’ve got about $200 split between sale items of:
Galibier skinsuit
Giro Adv 2 helmet
Clip on bars

That’s good enough for damn close to a 24min flat 10 miler on about 240w.

I’ve got position photos in that thread also.

I just can’t fully tap my roadie power yet in the position. But more has come with each attempt.

Solid list. I took the advice from here:
http://www.bikeroar.com/...ke-into-a-tt-machine
which is essentially the same, but I will also say: don't do just the aero bars. Do the whole list, get your position sorted properly. Use a saddle that has long rails that you can get a long way forwards and you can sit on the tip of (within the limits of the 5cm setback rule). ISM are good for this.

Also, unless your bike is a pig to recable I would strongly suggest adding a base bar and brake levers. That way your whole cockpit is a bolt-on affair and won't need adjusting each time. Bolt on cockpit. Bolt on saddle and post. Connect cables and tune gears. Done. Much less work than swapping a stem each time (at least for me with external cables...).

Wrap tape around the seatpost and you'll have it marked to the same height each time. (If you have an aero/asymmetrical seatpost you're out of luck in finding a replacement that you can offset forwards sorry. Hope it's round...)

Here's my converted road bike that I've spent a total of <US$300 modifying:

3 mins for wheels? FLO says 55 secs over a 40km time trial.

Your first clue that those values are made up might have been that adding them all up nets you 11 minutes.

^this... position that a proper fitting TT bike allows you to be in for the long haul is everything.

Doh, I forgot to fix that one... I pulled them from a table that was all index to full IM bike distance. I probably did not divide some of them back down to 40K for the quick fix. Going back to edit the times in the list.

I think something's off in your table or the conversion. You had 11 minutes originally and you have 7.5 minutes now. Since a 40k is about 22.2% of the iron distance, if your original 11 minutes is correct, then I would expect the 40k savings to be a tad less than 2.5 minutes - unless I goofed the math.

Back in the day, when the only aero helmet that was available to the masses was an LG (can't remember the model), there was a test that showed it saved more time that a Zipp 404 front wheel. This was when a 404 front was $600, I think.

Post deleted because I'm a retard!

Isn't that what it says?

However in OP's case, you wouldn't get much benefit over an Evade helmet.

Wow, I must have been really tired when wrote that!! Yes, it is! And I agree, not much benefit over an evade. Clip on bars is definitely the best way to go.

Only some of the times were off. I just re-copied most of the numbers from this article:

   

pretty sure others have determined sure shoe covers are worth ~0 or less in most cases.

eg: http://forum.slowtwitch.com/...ost=3513839#p3513839

if you insist, i think the wisdom is to use something very tight and rubberized. not sure if there is any data on velotoze other than what they paid for themselves here: https://bikeboard.at/...m-Windkanal-th218146

Some of the things suggested will cost as much as scrounging together a tt bike and still be nowhere near as fast.
A used alloy frame that gets you into a good position with the wheels you road race on will get you ~98% of the benefit of a latest generation bike (if you are careful about parts choices).
If you wish to compete (or not lose too much time in tours) in TT then switching around your road bike is not going to do the trick (with exceptions of course)

have you checked http://www.aeroweenie.com/aero-assistant.html ?

Wow. This is all so helpful. I really appreciate the chart of $/second gained :)

I should add - I do have a 2018 tarmac with Roval wheels. So it's not a venge, and not full-disc wheels, but I had a little help. The trick is that I bought the aero-fly bars and I couldn't fit the pair of borrowed-clip-on aero bars. I think if I wanted aero bars, I'd have to completely change the cockpit?

Thanks. What's the source for that article? Some of the numbers are in line with what my old brain is remembering. Others "seem" a bit off. The shoe covers is a good example. I'm thinking that someone here who tests stuff posted that shoe covers were negligible and can increase drag in some instance. But it could easily be that my memory is off.

It came from https://cyclingtips.com/...ime-trial-equipment/. I did not call out the shoe covers, but the other items had been generally supported in other threads here. As I said in my original post, this gives a rough order of magnitude, directional guide. The comment about latex tubes and fast tires came from comments made by Tom A., Thomas Gerlach, and others. The wheels # came from FLO.