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Spiral scrape on rear tyre.

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Spiral scrape on rear tyre.

Postby newcross on Sat Jun 23, 2007 12:05 pm

Please refer an entry in Abike Central Blog http://www.abikecentral.com/blog/?p=79 for detail, but

DOES ANYONE ELSE HAVE THIS SYMPTOM?

I'm curious. :shock:

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Postby Binch Shin on Mon Jun 25, 2007 4:01 pm

woops..
Maybe this is the first case over the world.

If every pin of chain touched the tyre, the scrape lines would be more complex. So I guess that just one pin is out of his position.
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Postby newcross on Mon Jun 25, 2007 4:18 pm

I'll check it out later. Thanks! :wink:
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Same problem!

Postby PeKaPro on Tue Jun 26, 2007 5:39 am

Newcross,

I definitely have the same problem! The loose chain is the cause (see topic http://abikecentral.com/forum/viewtopic.php?t=225.
It causes the chain to be stuck between the 'casing' and the wheel.
I haven't contacted the dutch supplier yet. I am curious abou t the answers you are getting.
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Postby newcross on Tue Jun 26, 2007 9:26 am

>Chain-pin

I checked it and there was no pin out of ordinary. I found that the scrape scar exactly matches with the path of every pins on the lower-half of the secondary chain, though. mmm

>loose chain

The thing is that my A-bike's chain is not so loose... :? I had to pull the chain very hard to expose it for the photo in my previous post in this topic.
I couldn't find any solid evidence of "stuck between the 'casing' and the wheel" in my A-bike at the moment. I'm checking it without riding, so the result might differ when the bike's on the move (or warmed up).

I also suspect that this could be because the rear wheel's axis or cog went off alignment, but not sure.
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Postby Binch Shin on Tue Jun 26, 2007 1:26 pm

This is my second opinion.

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Postby newcross on Mon Jul 02, 2007 11:19 pm

I haven't managed to find enough time to open-up gear-box yet, but I hope that's not the case...hee.. :(

(The axis of middle gear is just an GF plastic pin extended from the case itself. Yeah, It did look fragile....)
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Postby Timbo in Essex on Tue Aug 07, 2007 10:22 am

Just to let you know; I am also getting this problem after about 6 months of riding the A-bike pretty well every day. I am not mechanically-minded so I am wary of taking the bike to bits but it is obvious that the chain or part of the chain has shifted and is now rubbing on the rear wheel causing similar scoring to that shown in the photographs above.

For the simple minded, is there anyway of curing this easily or is it better to let Mayhem deal with it as the bike is obviously still under warrenty?

Many thanks in advance for any help.

Reegrds

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Postby Binch Shin on Tue Aug 07, 2007 11:53 am

There was A-bike Maintenance Meeting in Korea on Jul. 22, 2007.
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At the day, I opended three gear-boxes and I saw the spiral scrape for the first time in Korea.
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In this case, the reason was exactly the loose chain.
I exchanged the chain and the A-bike recovered.

Of course, the inside of gear-box was clear without any damage.
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Postby dcool on Wed Aug 08, 2007 2:14 am

Hi,

may i suggest something ? I think it will be good if those who are having this problem to state 2 things :

1. their weight.
2. the way they hop onto the bike.

My theory is that if your weight is on the high side ( 80 plus kg ), most likely the chain will get stretch after a while of ride, probably ard 5 mths ?

And also how you get on the bike maybe another reason, for eg, i know there are some people who step on one of the pedal with his or her full weight before sitting on the seat when moving off. By doing this over a period of time, the chain will stretch even faster.


Of course normal riding will also stretch the chain but not to the extend that its prematurely.

This just a thght..
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Postby Timbo in Essex on Wed Aug 08, 2007 8:22 am

In reply to dcool:

I weigh somewhere in the region of 11 to 12 stones (approx 77 Kgs) so I am well within the manufacturers guidelines.

I normally start to ride by sitting on the saddle, pushing off with one foot on the road and then peddling.

Even so I am a bit worried that this will stretch a metal chain within only about 5 months of cycling and what do I do to remedy it? Presumably everybody will sooner or later have the same problem depending on their usage of the bike?

All the best
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Postby jkevinwolfe on Wed Aug 08, 2007 3:53 pm

Both my chains appears to be lose. The looseness started after the first few miles I had the A-bike. I have opened it up just to make sure the center gear is seated correctly. I can't have imagined that the chains would have stretched that much.

I am just under the weight limit and and am very gentle with the pedals. I have never put my full wieght on them.

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Postby gold682 on Wed Aug 08, 2007 8:50 pm

Just a thought but could it be the tyre itself slightly under inflated, thereby with the extra factor of the rider sitting on the bike, causes the tyre to bulge at the side walls and therefore pressing against the chain.

This would seem to make more sense than a loose chain, because surely a loose chain would just move in the vertical plane (ie up & down). Where as the scraping to the tyre must be cause by a continuous "pressure" against the sidewall.

Hope that makes sense. What do you think ?

Cheers
Paul

(don't currently own an a-bike, but waiting for my £150 in Currys vouchers from my Goldfish Visa to get myself one)
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Postby Timbo in Essex on Thu Aug 09, 2007 12:47 pm

I am careful to ensure that my tyres are kept fully inflated to the correct pressure.

I am a bit sceptical about the loose chain theory. It would only be loose on the lower part of the chain anyway as the top part would always remain under tension and I simply cannot believe that a loose chain could cause this deep scoring of what is a quite thick, rubber tyre.

To my simple non-technical mind, the problem seems to suggest that somehow either the rear wheel or the central gear have become mis-aligned. I may try and, reluctantly, open the bike up this weekend and have a look. Does anyone know if this would invalidate the warrenty as I am minded to take the bike back to Mayhem?

Regards to you all

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Postby Timbo in Essex on Sun Aug 12, 2007 1:43 pm

I have now had a look at the rear wheel of my bike and despite my earlier scepticism I do now believe the tyre scrape is indeed caused by the loose chain.

When the bike is the right way up, the loose chain gets caught between the casing of the bike and the tyre. If the bottom of the chain was under tension, then it wouldn't hang low enough to get caugh by the casing.

I have sent an e-mail to "support" at Mayhem and will report on any response I get back.

I am not curently using the bike as I consider it to be potentially dangerous design/manufacturing fault. I also do not wish to destroy my back tyre

It is my view that this problem is caused by inferior quality components - how on earth does a metal bicucle chain stretch and after only a couple of months?

Many thanks for all the help from the A-bike community.

Regards,

Tim W-W
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