Racer Advice/Question: "Modifying" a TT Helmet

[nate2351]

Anyone have thoughts on cutting the back off an old TT helmet? I have a Giro Advantage (see pic) helmet from 2011 and was thinking about cutting the back off to shorten it and make it more aero. Is this a terrible idea? Will this make the helmet not USAC legal?
http://www.7hundred.co.uk/images/MAD/cg2013276-78.jpg?width=458&height=358

[Fixed]

I would not
But that is me ,every -time I try to modify something l screw it up
Cheers :)

[Louis]

Anyone have thoughts on cutting the back off an old TT helmet? I have a Giro Advantage (see pic) helmet from 2011 and was thinking about cutting the back off to shorten it and make it more aero.

The tail is there for a reason - it makes it more aero. If you shorten the helmet and remove the back it will be less aero. I can assure you 100% about that.

[Bruce K]

Actually it only makes it more aero if you can maintain the proper position, keeping the tail in contact or almost in contact with your back/shoulders. Studies in the MIT wind tunnel have shown that one of the most aero helmets in aall different positions was the old, smaller Garneau helmet but it was much poorer (when every watt "counts") in a straight line.

That is why TT helmets are trending away from the long tails - almost no human can maintain that position for the whole ride. We look down, turn our heads, etc and at that point the long tail is a wind brake. The "stubby" helmets may be slightly less aero in the normal position but during the overall ride they are much better.

Cutting the back off your Giro presents several issues:

1. You aren't equipped (tools and aero engineering knowledge) to make the cut at the proper location or shape for that helmet to create what you want. Most of the stubby helmets have smooth, rounded backs.

2. You may be damaging the crash integrity of the helmet.

3. You might cause the helmet shell to delaminate from the crushable liner.

SO as Fixed said, I'd leave it and if you really want a stubby helmet go buy one.

BK

[Tandem Rider]

Anyone have thoughts on cutting the back off an old TT helmet? I have a Giro Advantage (see pic) helmet from 2011 and was thinking about cutting the back off to shorten it and make it more aero. Is this a terrible idea? Will this make the helmet not USAC legal?
http://www.7hundred.co.uk/images/MAD/cg2013276-78.jpg?width=458&height=358

It will make the helmet non-legal for USAC racing. Drag out the rule book, 1N1 tells us when to wear them and leads us to the Appendix, USAC Policy 1 section 1 and 2. If you are still with me yet, this means the helmet must have a DOT sticker and still meet the standard.

If you modify it, you will have to get it re-certified, it may be cheaper to buy a helmet factory than pass certification. You will be faster to buy the helmet you want, and just spend the hours you would have spent modifying doing some intervals.

I have been checked at TT's, RR's, and Crits, so Officials do look (as they should). Disclaimer, Mrs. TR is a USAC official, so this information is readily available.

[Charles M]

There's a big dif between hacking the back off an existing design and any of the shorter TT helmets getting more use now...

There's almost no chance that your current design can be cut to create a proper kamm tail solution and the alternative will absolutely be less aero (as well as resulting in a structural change that voids it's approved competition use...)

[Fishbike]

Please don't mess with the integrity of your helmet.

And don't put shoe-goo on a worn tire.

There's clever and then there's stup. . .well, not so clever. Making a shim with a soda can is clever. Messing with your head and connection to the road, not so much IMHO.

[tiretrax]

Get a new Giro or a KASK.