Pedal Problem

For discussions about bikes and equipment.
Tim DH
Posts: 12
Joined: 21 Jan 2014, 11:09am
Location: Scott Hall....... LEEDS

Pedal Problem

Postby Tim DH » 20 Jun 2020, 8:37pm

Our Tandem goes in a suitcase (Circe Helios). We frequently remove/replace the pedals. On two occasions, whilst riding, a pedal has worked loose and stripped out the last bit of thread in the crank.

Because its an alu crank it is not possible to drive the pedal through from the wrong side to re-tap the thread. The crank is too wide. The pedal thread cannot reach the damaged thread of the crank.

Fortunately, on both occasions, this happened near home....

Does anyone know of pedals with longer threads which would reach through? With such pedals I would be able to attempt a repair, should it happen out in the wilds. Also, given that two of the cranks now have damaged threads I'd be a bit more confident with a deeper anchor for the pedals.

Tim DH

tatanab
Posts: 4091
Joined: 8 Feb 2007, 12:37pm

Re: Pedal Problem

Postby tatanab » 20 Jun 2020, 8:43pm

What sort of pedals are you looking for? Rubber, flat, toeclip, clipless. Back in the mists of time, certainly into the 1970s, pedals were available with short threads for steel cranks and slim aluminium ones like Campag, and also a long thread for thicker aluminium cranks like Stronglight 49D. So if you want toeclip compatible pedals then you might find some on eBay.

Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Pedal Problem

Postby Jdsk » 20 Jun 2020, 8:57pm

How about rebushing the crank threads with inserts?

Jonathan

pwa
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Joined: 2 Oct 2011, 8:55pm

Re: Pedal Problem

Postby pwa » 20 Jun 2020, 9:02pm

Alternatively you might use MKS Ezy pedals which you can remove without a tool, leaving a short stump in the crank. And the bit left in the crank for transportation could be bonded in, given that the cranks are already damaged. Even using this approach, though, restoring the threads first would be essential for security.

https://www.mkspedal.com/?q=en/product/term/4

alexnharvey
Posts: 1112
Joined: 10 Jan 2014, 8:39am

Re: Pedal Problem

Postby alexnharvey » 20 Jun 2020, 9:24pm

I'm curious about why it is happening. Is it the stoker's cranks or does it happen on both?

Thread inserts could be a good solution. I would guess solid inserts would be better than the spring like coils for repeated inserting.

Brucey
Posts: 39500
Joined: 4 Jan 2012, 6:25pm

Re: Pedal Problem

Postby Brucey » 20 Jun 2020, 10:10pm

photos?

I'd also want to know why it has happened more than once.

Could you use folding pedal instead?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Tim DH
Posts: 12
Joined: 21 Jan 2014, 11:09am
Location: Scott Hall....... LEEDS

Re: Pedal Problem

Postby Tim DH » 20 Jun 2020, 10:23pm

Hi Folks,
Thanks for the responses.
First time it happened just after a rebuild.. Stoker right pedal.. I assumed I hadn't driven it home properly, in the rush to get going.
Second time it happened.. Captain right pedal.. After at least 20 miles since previous rebuild.

Can't think of any useful photos to take!

Most pedals seem to have just seven turns of the thread.. Some 'Crank Brothers' pedals appear to have nine looking at pictures online.

Tim DH

Brucey
Posts: 39500
Joined: 4 Jan 2012, 6:25pm

Re: Pedal Problem

Postby Brucey » 20 Jun 2020, 10:35pm

possibly you could modify some pedals (by grinding the shoulder on the spindles) so that the threads nearer the back of the crank are used, and the threads near the front of the crank are not. Might this at least partially address the issue?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

gregoryoftours
Posts: 1221
Joined: 22 May 2011, 7:14pm

Re: Pedal Problem

Postby gregoryoftours » 21 Jun 2020, 12:17am

Tim DH wrote:
Most pedals seem to have just seven turns of the thread.. Some 'Crank Brothers' pedals appear to have nine looking at pictures online.

Tim DH


Only trouble is the threads of the pedal might be more secure but the rest of the 'crap brothers' pedal might not last! Speaking of negative experiences with the longevity of crank brothers products.

iandusud
Posts: 331
Joined: 26 Mar 2018, 1:35pm

Re: Pedal Problem

Postby iandusud » 21 Jun 2020, 9:29am

pwa wrote:Alternatively you might use MKS Ezy pedals which you can remove without a tool, leaving a short stump in the crank. And the bit left in the crank for transportation could be bonded in, given that the cranks are already damaged. Even using this approach, though, restoring the threads first would be essential for security.

https://www.mkspedal.com/?q=en/product/term/4


I have no experience of the durability of these pedals but would suggest that they would be good idea rather than regularly removing and refitting 'normal' pedals. IME crank threads in alloy cranks don't respond well to having pedals regularly removed and refitted.

alexnharvey
Posts: 1112
Joined: 10 Jan 2014, 8:39am

Re: Pedal Problem

Postby alexnharvey » 21 Jun 2020, 10:08am

I had wondered if the stoker wasn't pushing hard enough and so the pedals were seeing a reverse precession load. Apologies to your stoker and all the others who have been accused of not putting enough effort in! :lol:

The EZY pedals could be a good solution. I have the older style EZYs on a folding bike and found them quite good but some people find they can detach during use which is quite a big problem. The EZY Superior versions are supposed to be better. Discussed recently here viewtopic.php?f=5&t=93622 I think they are better than most folding pedals.

As pwa says, unless the threads are totally knackered you might be able to secure EZY mounts in the cranks with threadlock or even some epoxy? A picture of the outer crank threads to see the damage might be useful if you can get a good shot of them.

That might well be cheaper than having the threaded inserts fitted to both sets of cranks and a better overall solution in the long run. Another option would be to carry a pair of pedal taps, these can be bought quite cheaply. However, I think neither those nor longer pedal thread really address the root of the problem.

Samuel D
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Location: Paris
Contact:

Re: Pedal Problem

Postby Samuel D » 21 Jun 2020, 11:47am

alexnharvey wrote:I had wondered if the stoker wasn't pushing hard enough and so the pedals were seeing a reverse precession load.

Very good.

Pedal threads should be greased and screwed in tight. Tighter than many people think. Shimano specifies 35–55 Nm for most (all?) pedals, for example. I see no reason not to aim at the top end of that. It would take a tough hand and mechanical coordination to achieve that with a regular-length 8 mm Allen key. Pedal spanners aren’t much better since they are often made of cheese (e.g. Park Tool) and deform at torques lower than 55 Nm.

A torque wrench is a good guide.

Good threads in the crank are a first requirement for this.

Brucey
Posts: 39500
Joined: 4 Jan 2012, 6:25pm

Re: Pedal Problem

Postby Brucey » 21 Jun 2020, 12:04pm

a second requirement for reliable pedal installation is that the pedal spindle should either

a) have a full shoulder or
b) if of the incomplete shoulder type, pedal washers should be used.

Precession can only work if the spindle is able to move in an unhindered fashion; unfortunately if the spindle hasn't got full shoulders, and a pedal washer isn't used, the spindle is usually obstructed by a burr raised on the crank.

Image
MKS spindle shoulder; a poor feature on an otherwise excellent pedal; fortunately pedal washers are not expensive

There are quite a few pedals which are otherwise very good (e.g. lots of wellgo models, MKS sylvan etc) where the pedal spindle has an incomplete shoulder and won't precess easily.

IME if the pedals have full shoulders on the spindle, and the threads are greased/in good condition, they will self-tighten when subjected to normal pedalling loads (not with cranks fitted oddly or a stoker who is dragging their feet). Witness the typical scene at the airport on the way back from training camp; smug people with pedal spanners who can undo their pedals, and other folk sweating and cursing with allen keys ("I am sure I didn't do them up this tightly" etc etc)

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Tim DH
Posts: 12
Joined: 21 Jan 2014, 11:09am
Location: Scott Hall....... LEEDS

Re: Pedal Problem

Postby Tim DH » 21 Jun 2020, 1:10pm

Thanks for all the help

With regard to

alexnharvey wrote:
I had wondered if the stoker wasn't pushing hard enough and so the pedals were seeing a reverse precession load.


I AM THE STOKER!!! (So that might explain why the Captain's pedal dropped out!!!!!!)

With regard to an incomplete shoulder: How does a pedal washer resolve this? Doesn't the incomplete shoulder just push up against the washer in the same way as the shoulder pushed up against the crank? Either way, since I'm concerned about the effective length of thread I have remaining, I'm not keen on a washer holding the pedal further out!

I'm don't really want to have to carry pedal taps whenever we go out.

With regard to
the typical scene at the airport
We usually travel by Megabus (Hence the fierce reluctance to carry taps, or pedal spanners etc. etc... because of weight limits) On one occasion I had to resort to using a seat tube to get extra leverage on an Allen Key!!

Tim DH

Brucey
Posts: 39500
Joined: 4 Jan 2012, 6:25pm

Re: Pedal Problem

Postby Brucey » 21 Jun 2020, 1:17pm

pedal washers are hard (unlike cranks) so don't raise a burr so easily. Even if they do, the other side can still move easily vs the crank. They are only ~1mm thickness; not even one thread on 20tpi. Cranks which are designed for pedal washers often have a recess for them; such a recess could be added to any crank but it isn't a straightforward operation.

The MKS spindle can be ground back as I suggest upthread because it is constant section. However pedals with a full shoulder cannot usually be ground back very far before the shoulder starts to disappear. So I would suppose that if you try the 'grindback' route you will end up with a modified spindle of the pictured MKS type, and a pedal washer would be a good idea.

BTW isn't the rider with the (functional) handlebars always the captain? Or is there a different protocol?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~