Silicon bear around Tire/Rim surface

Triathlon Forum
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Now, yes, i have a propensity for doing wild stuff to gain speed from my bike, in addition to hard training. A few months ago i think i saw an article/photos on cyclingnews or velonews about Tour mechanics putting a seam/smooth bead of silicon very small on the joint between the tire/rim, basically above the braking surface right where the two come together.

i know bontrager went to great lengths to build a clincher tire that had a little flap that comes down and fills that void. i know when i was in the MIT tunnel we tested my Zed999 Clincher vs a Zed 999tubular and from an aero perspective, the tubular was slightly better because of a smoother transition fro tire to rim.

i saw the article about the silicon, gave it no real though.

now a good buddy Dave L, who i race and train with, just obliterated (cat5 , but a hard core compulsive TTer), i mean obliterated an entire field of TT’ers including myself (m35 state Champion) and the P12 State Champion. 20minute TT, best times were like 20:11, 20:02. he was the only rider of a few hundred that was sub 20, 19:30. like me, he’s nutty about perfectng every aero thing he has going. he came to MIT as well, and he’s pretty slick in the tunnel. low drag. a bit lower than me.
he pushed 322 watts for this TT. i pushed 342. 21 minute effort. he bested me by 30 seconds, first M35 Thumping i’ve taken all year, though took 2nd with 3rd overall. he just smooshed the field.

wthout getting into the other things we do to try getting faster (again, in addition to heavy training), he tells me he “put a silicon bead on his tire/rim:”

So my question is: does anyone have any experiences with this, good or bad? how to do it? what to avoid? etc.
i have concerns that while silicon dries nicely and solid, under heavy braking , which i guess really doesnt happen n TT’s, it might bleed down onto the braking surface.

Dave is a specimen. he does an FT workout, full hour on that Stepmill full tilt. He trains 6 hours week but does hard core intervals every other day. like 3% body fat, long lean, powerful. he is really a spectacle on that bike. but we’ve always been far cose. i’m not saying tis teh silicon i’m just curious if the silicon works.

thoughts? ideas?

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…i know bontrager went to great lengths to build a clincher tire that had a little flap that comes down and fills that void…

Yeah…and then they molded it on a 60tpi tire…doh!

I think your friend is playin’ with ya…this chart referencing some old Chet Kyle data says it would be good for only 1 or 2 seconds over 40K. Your TT is much shorter than that. It’s not the silicone bead :slight_smile:

BTW, if he went 30s faster on 20W less over that short of a distance (what was it, 10 miles, 10K, something else?), he’s more than just a “bit lower” drag than you.

Assuming it’s relatively flat and you both use the same tires, if you guys both went the same speed, he’d be ~.020 m^2 lower CdA. The fact that he went 30 secs faster that would mean at least another ~.020 m^2 less or so. A total of .040 m^2 of CdA is pretty significantly less drag (for typical CdA values that would be ~15-20% less drag).

Then again, you didn’t say what tires you both are using…worst case, differences there could account for a LOT of the time differences…silicone bead or not :wink:

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“i have concerns that while silicon dries nicely and solid, under heavy braking , which i guess really doesnt happen n TT’s, it might bleed down onto the braking surface.”

calk would dry and work fine with no problem with heat
I would try it a small tube of clear silcone calk < $5.
It peels of nice to
cut the tube with a small hole on an angle and use your finger to smooth it
It is a mess if you use to much

some parts on your car motor use it for a gasket
as it can be bought for high temp at the auto store (orange color)
so you might try the auto parts store

Dirtball

4

i totally agree the 35 second gap to me, and 25 second to the nearest Pro 1-2 was not a result of the silicon bead. but when you see someone WHALING crazy times, with lesser watts, any good rider should inquire about whats what…and figure out what is working and what is not.
this guy is fast, and i mean slick. looks like a prototypical crazy TTers.
not suggest its not his aero, because he’s my teammate, and i’m PSYCHED for him to be whompin’ arse, but could also be:
overall better/lower drag
(we runsame tires i believe) i run a vitto evo cx 7x23 in rear, and zipptange dimpled , both clinchers, zedtech999set. he runs a HEd clincher set…i think they are same tires. maybe he’s running Veloflex.
but otuside equipment gains, could be a: improperly calibrated power meter; b)different weather conditions…it was raining nasty and windy, and he went out 40 minutes after me.

dont mistake my inquiries and comments. this guy is my teammate and i’m super stoked for him. we’ve done a ton together, went to tunnel. we have trade off wins,2nd places for most of the seaosn…

i really was simply inquiring about the silicon and hat the impact might be, and how it gets set up.

thx .

5

…could be a: improperly calibrated power meter; b)different weather conditions…it was raining nasty and windy, and he went out 40 minutes after me.

OK…now we’re getting somewhere. What PMs do you guys use? Also, obviously weather conditions can make a huge difference.

i really was simply inquiring about the silicon and hat the impact might be, and how it gets set up.

Well…it appears the impact would be tiny for the case you presented. If you think that booties/no booties is “lost in the noise” of utility, then the silicone is even more so.