Dropped fork, rules of thumb needed!

Discuss light weight issues concerning road bikes & parts.
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Valy
Posts: 152
Joined: Tue May 29, 2012 11:16 pm

by Valy

Hello, I have a pickle and wonder if you have a "rule of thumb" advice please.

Was installing a fork into the frame whilst it was hanging in the bike stand. Inserted the fork into the ht and seals had enough resistance to just about hold it in place. (have not rebuilt a bike in a while)

Walked a little away from the bike and of course the fork slides out and hits the floor.

It's an aluminium steerer / carbon blades / aluminium drop outs type from a Genesis Equilibrium 2014

It weighs around 800g all together with the caliper I'd guess, and fell about 1 meter onto a thin bit of rug (~1.5 mm cotton) and concrete floor underneath.

There is not any visual deformation or cracks, nor has the paint suffered. It's just worrying me whether the drop could have stressed the drop outs to compromise, as when they landed, it was just on the tip of the drop out and it feels quite violent for such a small area.

Anyone's had experience with similar mishaps? What were the outcomes?

Thanks a lot.

by Weenie


dudemanppl
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Joined: Fri Feb 22, 2013 5:09 am

by dudemanppl

Zero need to be worried.

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Valy
Posts: 152
Joined: Tue May 29, 2012 11:16 pm

by Valy

Yeah I know what you mean, it's just that the impact was over a very small patch so it's not what the drop outs are designed for. My bike once fell from about 1.5m onto the saddle and the Ti rails got bent to the point of ruining saddle.

I'm worried about the drop outs only here.

sungod
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Location: it's raining, it must be uk

by sungod

even a thin rug can considerably reduce the shock load

i'd just give a careful visual inspection, then use finger/hand force to load the various bits, plus the tapping test above

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cyclespeed
Posts: 585
Joined: Mon Jun 06, 2016 8:45 am

by cyclespeed

I dropped a breezeblock as hard as I could onto my Sworks fork steerer* (it was a warranty return).

It made not the slightest impact.

*visible in my 'Cutting open an Sworks fork' vid.

BdaGhisallo
Posts: 1929
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

cyclespeed wrote:I dropped a breezeblock as hard as I could onto my Sworks fork steerer* (it was a warranty return).

It made not the slightest impact.

*visible in my 'Cutting open an Sworks fork' vid.



It is amazing how tough modern carbon forks are. A while back, after trimming and installing a new Enve 2.0 fork, I put the sawed off portion of the steerer tube into my vice and started to tighten it. I used all my strength and even employed a cheater bar on the vice handle, and I couldn't deform the piece of steerer tube. To say I was amazed would be an understatement!

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Valy
Posts: 152
Joined: Tue May 29, 2012 11:16 pm

by Valy

sungod wrote:even a thin rug can considerably reduce the shock load

i'd just give a careful visual inspection, then use finger/hand force to load the various bits, plus the tapping test above

Yeah that's true. I'm wondering how'd be best to estimate the pressure out if interest.

Might be a good workout solving it)

GothicCastle
Posts: 116
Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

RobotGuy wrote:Flick each fork leg in various spots with your finger and it should resound with a nice clean sound. Any cracks or delamonations will sound a hollow thud or even a sick sort of vibrating sound.


This isn't quite correct. 1) you'd need to tap it with something a bit more dense, like a coin and 2) all delaminations won't be obvious from simple tapping. Some will, others are more subtle.

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Valy
Posts: 152
Joined: Tue May 29, 2012 11:16 pm

by Valy

Delamination is not the concern. The fork fell on the front bit of the aluminium drop outs.

huffington
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Joined: Sun Nov 29, 2015 3:29 pm

by huffington

I'll leave this here

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Valy
Posts: 152
Joined: Tue May 29, 2012 11:16 pm

by Valy

Sure. My concern is not about the application strength of the dropouts, I'm sure they've been engineered exactly for that scenario. Not for point load without anything in them.

I'll try it out soon enough but a lot of people have misunderstood what I meant. I know it seems odd to ask about it, but trust me when you see a ti saddle rail completely bent from falling just 1.5m you realise a few things.

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Valy
Posts: 152
Joined: Tue May 29, 2012 11:16 pm

by Valy

Yeah maybe I did not phrase it clearly enough. I'm not bothered about the fork bring able to cope with the stress - that is fairly safe. Especially when you remember all those pot holes you have hit at 30mph! :D

I'll give it a ride and keep a look out. Thanks for the replies everyone!

by Weenie


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