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Spiral scrape on rear tyre.

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Expand view Topic review: Spiral scrape on rear tyre.

Re: Spiral scrape on rear tyre.

Post by rongood on Wed Nov 19, 2008 7:58 pm

I recommend shaving off the lip formed on the crankcase housing that narrows the gap between the tyre and the housing. This narrow gap causes even a very slightly stretched chain to get caught and cause damage to the tyre, or break the chain, or even tear up the bearings. If you shave off that lip, the chain can safely drop as it stretches, causing no damage. It is not unusual for bicycle chains to stretch and it is normal to allow tolerance for such stretching. I shaved mine off using a Dremel rotary tool with a grinding bit, but you could just file it off. Be sure to take the housing off the bike before doing the work to avoid getting shavings up in the gears.
Attachments
abike fix 8D.jpg
this is after i removed the lip. Now there is just enough room for the chain to fit between wheel and housing
abike fix 8D.jpg (26.99 KiB) Viewed 9181 times
abike fix 9D.jpg
here is the lip,or ridge, to the left of the chain in this photo, before being shaved off
abike fix 9D.jpg (35.6 KiB) Viewed 9376 times
abike fix 7D.jpg
another view showing that the lip is now gone.
abike fix 7D.jpg (37.33 KiB) Viewed 9197 times

washers

Post by Leo on Wed Feb 20, 2008 5:25 pm

hi people

after a couple of kilometres of riding, I experienced the same notches in my back wheel.

when pulling down the chain, it became evident that it had stretched (worn out) and as soon as i would drive over a bump, would be loose enough to jump down and get caught between the tire and the plastic (causing marks).

so i adjusted the tension to "H" and, as expected, the wheel would not run too smooth anymore, basically stop at a certain position.
I figured it would be due to the higher chain tension, and a faulty back axle that now, unlike before when the chain was loose, stopped the wheel.

however, after loosening the screws again, the wheel turned easier (without braking every half turn).
I decided putting the screws in without the little metal rings (washers, shims??) that go between the screw head and bearing.

well I never had a smoother-turning wheel before. seems that the rings grind against the casing of the bearing when installed. (bad design)

Nevertheless i put them back on, as without them the plastic mounting is allowed to move too much and i dunno if that stresses the parts and causes early wear.

Conclusion:

well thats hard. if your back wheel is not turning lightly, try removing them and see what happens. Or maybe install new ones (I have none that fit jet). If you have the time, just post if you experience the same problem, as I am interested if its just my bike.

enjoy riding!

Leo

Post by Timbo in Essex on Tue Oct 16, 2007 5:00 pm

Dear all,

I promised in my last message i would let you know how I got on with my wheel scrape problem.

I e-mailed "support@mayhem" but received no answer what so ever - they really do need to sort out their e-mails - so I phoned and got immediate service. I took my bike back to Mayhem at North Acton and they willingly replaced both the chain and the back tyre. There was a bit of a misunderstanding about what work needed to be done and an incorrect re-fitting, by Mayhem, of the inner tube but this was sorted out with good humour and in the spirit of true customer service. I was very impressed with the service I got from Keith and Matt at Mayhem and I now have my A-Bike back on the road.

I would recommend that should anyone have a similar problem they contact Mayhem BY PHONE and get their bike repaired before futher damage is done.

Regards to you all

All the best

Post by newcross on Tue Aug 14, 2007 12:11 pm

Oh, dear. Timbo's bike also got the spiral...

In my case, as I mentioned earlier, the chain was stretched, but wasn't loose enough to accept the tighter tentioner setting. Maybe it only comes to contact with the rim of gearbox while riding...

I got some replacement parts from Mayhem and open up the gear box to replace them by myself just before the first london meet. Interestingly, the chain (was secondhand) is just the same length as the previous one. After a week of rather intensive riding, I noticed a sign of the scrape's coming.
However, two weeks since then, there isn't any progress of scrape so far.

I think there are many aspects contributing to cause this problem as dcool and gold682 suspects.

Rider's weight, looseness of the chain, air pressure, road condition and flex of gear box (2-3mm flex that is) etc.


Mis-aligned gear wasn't evident in my case, but maybe more close inspection will help(?) :roll:

BTW, I'm rough on my A-bike, but not as rough as putting my full weight on a pedal, and I'm about 65kg.

Post by 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

Post by 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

Tim W-W

Post by 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)

Post by 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.

Kevin

Post by 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

Post by 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..

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

There was A-bike Maintenance Meeting in Korea on Jul. 22, 2007.
Image

At the day, I opended three gear-boxes and I saw the spiral scrape for the first time in Korea.
Image
Image

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.

Post by 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

Tim W-W

Post by 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....)

Post by Binch Shin on Tue Jun 26, 2007 1:26 pm

This is my second opinion.

Image
Image

Post by 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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