What is fork stretch?

I've been told by a Bike shop that they don't want to drill a front brake hole in my forks because the "fork stretch" will compromise the safety of the forks.

Has anyone else ever heard of this and, more to the point, what does it mean?

Cheers

They probably mean the flex under braking.

It's easy and safe* to drill most forks, perhaps they don't want to due to liability issues. If they are original track forks it might be best to replace them with some cheaper drilled ones to cruise around on. Once drilled they cannot be undrilled and you will often get a higher re-sale price for an original undrilled frame.

*This advice is worth what you paid for it.

Less material = possibly weaker, depending on the fork's construction.
I can understand them being wary about such a move. DIY

Cheers guys, could this be because they're carbon legs with an alu steerer? Is this a common problem with these types of forks?

Common is people not drilling forks. Buy a set with suitable parameters that have a brake hole already.

If this is a CX/MTN fork it would likely have its own bosses for a cantilever setup. Use that. Why drill a fork unless you made yourself, thus know the fork inside out?

i worked in a bike shop for about a year and a half, never heard 'fork stretch' before.

While the phrase is probably bullshit, and the thinking sounds a bit half-arsed, the sentiments are very much true.

If you want to fit a brake, buy forks that have been designed to have a hole in them.

^This post makes no sense.

My Fuji Track Pro came with a fork that was undrilled, I had it drilled (friendly chap with a pillar drill- more accurate than me holding the fork down with a foot and having at it with the hand-held) and it has been fine.

It is a carbon fork with an alloy steerer, you are welcome to have a look/go if you wish.

Many of these forks are also available drilled- so the material of the fork has been designed to accomodate a hole from the outset.

I was thinking of you when i wrote that neil! How weird.

I'm not saying that you can't do it, and that for all intents and purposes be left with a perfectly usable set of forks that won't fail, or suffer from whatever fork stretch is.

I guess what I meant to say was that drilling forks means you're dealing with unknowns: some forks come in drilled and undrilled versions, the difference being only the hole and whether or not there is one, others don't and could be structurally compromised by drilling them. Finding out which your forks are can be difficult and we certainly dont know.

And thats not even touching on the fact of the chance of you ruining a perfectly good set of forks by drilling them askew, for those of us without a friend with a pillar drill.

My first line was intended to refer to Skylarks post, not yours.

Your post makes perfect sense.

Thanks for your input guys. TBH, I'd rather not have the expense of having to buy new forks, hence me wanting to drill what I've already got. I'd never heard of fork stretch either, although the concept sounds very plausible. Dammit, thanks for the offer to have a look. How long have you had it drilled? I assume even if it was to compromise the integrity of the strength of the fork, it would show some sign of stress long before it failed.

Drilling a hole into carbon fibre, then applying the forces of a brake to an area which is not designed to take the strain is a bad idea*. A really bad idea.
Making a hole causes a weak point in the weave, then the compression of the brake bolt apply force to this weak area, and the force of braking will almost certainly be more stress than the fork can handle, resulting in failure/probably serious injury. Forks designed to take a brake are reinforced in the necessary areas, and designed to take the loads applied under braking.
I work with composite materials on a daily basis, and as a professional, strongly advise against it.

*If the fork is reinforced to take a brake, but then left un-drilled, this does not apply. What forks are they?

I agree that drilling into Carbon fibre isn't the most sensible of ideas, but I'm talking about a aluminium steerer attached to CF fork legs, which I hope would be a lot stronger?

PS the forks are Moda Forte.

Does the steerer come right through to the bottom of the crown then? Photos of the fork, particularly the crown area, will help a lot.

judging by this photo I found online

I would say they are fine to drill.

Like These?

They look like they've been designed to be drilled, judging by the flat section. Make sure they are done accurately though.

judging by this photo I found online

I would say they are fine to drill.

They be the very same ones

ha, Sam Doman. I win.

PS, Sam Doman, I'll post a pic, when I can, of the inside of the steerer tube from the bottom, just so you can see how much material there is. Cheers

Fork Stretch. You've been warned.

Some pics;

http://www.flickr.com/photos/50049236@N08/6028460483/
http://www.flickr.com/photos/50049236@N08/6028460775/

Does this still look good for drilling?

have you considered asking the distributor for advice?

http://www.eurobike.uk.com/contact.aspx

I have, and they've referred me to a bike shop who already do some drilling to other bikes. Just trying to glean as much info as I can before getting it done.

I suppose if they've referred you to a bike shop which does drillings, it kinda means it's ok. They seem like they could hold it. I've never heard the fork stretch, though, sounds funny :)