Red crank loose pedal insert repair (DIY) step by step

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josemari220
Posts: 12
Joined: Sat Nov 05, 2011 9:52 pm

by josemari220

Hello everybody.
Sadly i am another victim of the carbon crank pedal insert loose. MIne are Sram Red. Not so usual like FSA, but the same consequence. Many post asking for solutions or repairs, but seems that almost nobody do it. Some of them tried to put some glue through holes, but nobody tried to do a real repair, so I have done it. Looking for practice more than do a real repair. This is my first attempt with carbon fiber, so I don´t mind which will be the final results.
So here you have the proccess with some pics to see real step by step.

First is to discover the pedal insert. You can do it easilly with a grinder. I opened a window in the front face.
1 red crank insert view comp.JPG


Then the insert can be taken out to clean the old epoxi and carbon residues.
Because of the unbonded, the insert is a bit loose, so it is necesary to add a thin layer of carbon where it sits to fill the gap. The good thing is that the inside of the arm has a shape where the insert sits perfectly, so is in no possible to vary the position, angle, lenght, etc.
To avoid epoxy goes to the pedal thread, I put thick grease in it, and cover both holes with a rouded piece of adhesive tape, just to cover the hole.
2 red crank insert out comp.JPG


With the insert out, you can see the hollow inside of the arm. Hi-tech.
3 red crank insert hollow arm comp.JPG


I designed some pieces with paper, with the shapes of carbon to do the layers. It is necesry to
wrap in differents directions, and it is complicated because the rouded shape of the arm end.
I also cut an small piece of poliuretane foam to fill an smal gap between the insert and the arm. The carbon must to be pressed, and, if is nothing under it, the carbon will fall into the hole and it will be not well compacted.
4 red crank planning carbon pieces comp.JPG


I have done the work with carbon cloth and epoxi resin bought in ebay.
Epoxy comes in two parts, so it is necessary to mix them in the right percentage.
5 epoxi mix comp.JPG


Apply the carbon pieces and soak with epoxi. It is not easy because they tend to loose the
position when you try to add the next piece in other direction.
6 apply carbon layer and  epoxi mix comp.JPG


When you have put enough layers, it is necessary to give pressure to the carbon-epoxi to force
the excess of epoxy to go out and achieve the carbon ends up very tight and with no air inside. There are some ways. This is a DIY, so i have used a tyre inner tube, opened along the middle. I gives you a wide, flat and elastic, rubber, that wrapping it, gives homogeeous pressure, and works very well.

First you need to wrap with carbon with some porous plastic. I have done with food film, holed with
an small nail.
7 holed film wrap comp.JPG


Then you need to put a layer that absorve the excess of epoxy. A piece of an old trouser do the work fine too.
8  cloth wrap comp.JPG


Stretch and wrap the inner tube trying not to move the added carbon layers. Before give pressure, all is very loose.
9  stretched rubber wrap comp.JPG


This is the final look after wrapping.
10  stretched rubber fully wrapped comp.JPG
Last edited by josemari220 on Tue Sep 13, 2016 4:11 pm, edited 2 times in total.

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Rick
Posts: 2034
Joined: Sat Aug 29, 2009 4:30 pm

by Rick

Of course it is your crank, and your health at risk if a pedal fails, but I would highly recommend against do-it-yourself crank repairs like this unless you are really confident of your experience in stress analysis and carbon fiber repair.
Most commercial carbon fiber bonding is done at high pressure and high temperature.
Surface prep is also critical, and just the tiniest bit of grease on the bonding surface can ruin the whole thing.
Please be careful.

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josemari220
Posts: 12
Joined: Sat Nov 05, 2011 9:52 pm

by josemari220

Thanks for your care. I know and i asume the risk. If i thought it could fail in any moment, i will not ride them. There must be pioneers to reach higher summits.
In fact, i think there is more risk to fail before repair, with the insert loose than now.
Time ago, carbon frames were un-repairables, and now lots of them are running. I have seen "professional" repair shops with vacuum or presurized ovens, that finally were a door under stairs with am electric heat radiator in.

This work is for practice and investigation purpose. If it works, perfect. If no, perfect too.

i¨m not encouraging nobody to do this. I only tell you that is possible.

Chapter 2. No possible to add more than 10 pics in 1 post.

The first impressions are fantastic. Very hard and smooth. I let cure one day long. Take off the tube, the cloth and the film is quite easy.
11 first layers cured comp.JPG


Obviously, it is necessary to sand a little to smooth the surface. The best is there are no big
wrinkles.
I prefer to do the job in some stages, to have more control in the way it is finishing, so, I have to put more layers to give thickness and a better leveled surface.
12 more layers to reinofrce and level surface comp.JPG


Finally need to open the pedal hole. A drill in the centre and then with care, and a dremmel, sand the carbon arround the hole where the pedal sits with a washer.
This is the final look.
13 finished without paint comp.JPG


Rear view
14 finished without paint comp.JPG


A final epoxy coat to the exposed carbon, to hard protection and give a glosy finish.
15 finishing epoxi coat comp.JPG


I have tested them uphill hard sprinting and they work as new, so, I´m happy. Will see in long therm use.

this is weight weenies, so I have checked them and they are now 7gr heavier. Doing the work with calm, doing the transitions between old and new carbon more progressive, and the finishing will be like new and no weight adds.

I hope somebody will be find all my efforts usefull.

Thanks for watching, and sorry for my low quality English.

Updated info. Today a long ride with steps, sprinting at full power with no issues. the feeling is to ride a like new crankset. Now I´ll take them off , and save them for spare, and ride the new one I bought after notice the problem. they are under warranty, so I have 2 years to stress them.
Last edited by josemari220 on Mon Sep 05, 2016 11:37 pm, edited 1 time in total.

Marin
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Location: Vienna Austria

by Marin

Jose, thanks for this, very interesting!

Do you happen to have pictures of your repair?

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josemari220
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Joined: Sat Nov 05, 2011 9:52 pm

by josemari220

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User avatar
josemari220
Posts: 12
Joined: Sat Nov 05, 2011 9:52 pm

by josemari220

Hello everybody.
This is a long term test conclusion about this carbon crank repair method.
I have repaired another pair of pedal insert loose cranks, right side FSA SL -K, and one Specialized. The owner, a big power biker, have ended the whole cx season with the repaired SL.k with no isues, but finaly fail... the oposite one, the left one, not the repaired, so I have done the same with it, and now, with both repaired, I hope they will last to the end of times.
For weight weenies, this repair have added 8gr to the left crank.
If any of you have this usual problem, look for somebody with the skills. It is posible to repair with full confidence. The cost is less than 20$
biela slk izquierda extraccion inserto.JPG
biela slk izquierda terminada detalle1.JPG
biela slk izquierda 144gr-152gr.JPG

jlok
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Joined: Tue Jun 30, 2015 3:30 am

by jlok

good work! always nice to see people repair stuffs instead of just throw it away.

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2old4this
Posts: 366
Joined: Mon Jan 13, 2014 7:26 am

by 2old4this

I have to admit, it is a very clean job.

I do not think I would do it though. Not that anything you did is wrong, I just do not know anything about the stress on the cranks...

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wheelbuilder
Posts: 1184
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

Nice work! I had a Red crankset warrantied for the same issue. They sent me a new crankset AND an extra set of chainrings! Your repair work is well done!
Never cheer before you know who is winning

alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

You are a skilled craftsman. Thank you for sharing your experiences. :)

/a

Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Thanks for posting this, inspiring!

maxpowers
Posts: 4
Joined: Wed Feb 06, 2019 4:10 pm

by maxpowers

This post and update is so useful. I found out Big Power and Red cranks don't hold up. I have the carbon resin dremel and a task now!

hadzray89
Posts: 3
Joined: Thu Feb 07, 2019 4:39 pm

by hadzray89

Hi jose, can i personally contact you on the repairs that you did? thanks ray
amazing job btw

MyM3Coupe
Posts: 374
Joined: Thu Nov 24, 2016 10:32 pm

by MyM3Coupe

You're either very brave or insane if you ride that crank. It's done. Make a wall decoration out of it.

by Weenie


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Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

MyM3Coupe wrote:
Thu Feb 07, 2019 8:40 pm
You're either very brave or insane if you ride that crank. It's done. Make a wall decoration out of it.
Why? It's a proper repair.

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