About Ready To Give Up Bikes For Good - Please Help

[*PHIL*]

This might end up being a longish post so please try and read the main parts of it... My sanity is at steak here........Steak?? or stake??

Anyway, on with the show.

It all starts a year ago. I bought a specialized hardrock. Rode it about for a year. Then something really annoying happened... At random times when riding the pedals would slip a quarter turn as if the chain lifted off the chain ring or whatever. This usually resulted in my foot coming off the pedal, ending in a crash. (i wasn't riding trials then i was just riding normally)

So I had it in the bike shop about 3 or 4 times and they couldnt find out what was wrong with it. Many parts got replaced like cassette, chain and the freewheel I think but nothing fixed it. I decided to just give up with it and sell it as i wanted a trials bike anyway...

2 weeks later, and I have a trials bike. An Onza T-Rex. Much to my annoyance, on the first ride, it happens again!! The pedals slip round about a quarter turn. I just got back from a ride where it did it 4 times. The first 2 like normal and the second 2 the chain came off the rear chainring/cassette (not sure what to call it as its a singlespeed).

Ok so... Take a look at these 2 photos:

And... spot the difference!

Now I don't know about the old specialized but I have a theory on why this is happening on the T-Rex.

The red line on the second picture... That derailleur thing is touching the frame where the red line is and can be kinda wedged under it or resting against it. So I reckon, when I do a hop or something, it moves up or down and causes the chain to move side to side, sometimes pulling it off completely.

I really don't know that much about this area on bikes so I could be completely wrong. but it does seem odd that the derailleur/chain tensioner thing is touching the frame. I didn't make the bike it was built by someone else.

My question is also... as it is a singlespeed, do I actually need any of the chain tensioner/derailleur stuff? I'm thinking if I just remove it, it would eliminate that part as the cause of the problem and if it still persisted, it would have to be maybe the bottom bracket/hub.

My friend jokingly said; maybe its you're riding style... I'm staring to think it might be but I don't see how that could affect anything.

So thats my story. Hope you all enjoyed it and have lots of ideas and suggestions for me!

PHIL

[scousertrials]

Get yourself a guset chain tensioner from tarty. Bin the draleur and shorten your chian if you can.

[Andrex]

You might just need a new sprocket and chain. That what happened on my bike and now its fine.

[*PHIL*]

Get yourself a guset chain tensioner from tarty. Bin the draleur and shorten your chian if you can.

I think that is my plan like...

Also if you or someone doesn't mind could you explain how chain tensioners work? I get their purpose and that but, what... they're springy or what??

You might just need a new sprocket and chain. That what happened on my bike and now its fine.

Sorry I may be an idiot... just to clear this up... what is a sprocket? The rear cog the chain goes round?

Also, not saying your wrong but what would a new chain do?

Edited May 1, 2007 by himynameisphil

[dave85]

I would disagree with what scouser says. Fit the second wheel back in the mech and get the whole lot back up under the dropout as you have it. That picture shows a distinct lack of chain wrap around the rear sprocket, using the mech as designed would at least take one variable out of the equation.

[Simpson]

To me your mech doesnt look right it just curled up with no tension on the chain... i always pushed my mech down into tension then tightened it all up

Even that looks pretty slack to me. Its not supposed to be curled?

[Krisboats]

I'm not suprised really, you have so little chain around that cog. Take some links out

EDIT: I'll get some pics of the chain line on my t-rex in a minute, using a mech with a single cog. Its good brb.

Basically though, the theory of whats happening is you have so little chain around the rear cog that it actually just slides off it and jumps round a bit. Its like it has a brief moment where it isn't attached and then catches up again when it lands on the next link. Mine was doing it the other day when the chain was too slack, it only happens while peddling because the chain reaches a point as the cog turns where theres only 2 or 3 teeth holding the chain in place, this results in it jumping off.

Edited May 1, 2007 by Krisboats

[Simpson]

Yea to get your mech to look more like my old 1 take about 4 links out? should do it?

[*PHIL*]

Thanks for all your help I have a better understanding of it now.

I would however like to get rid of anything unnecessary around there. I see some bikes with just the sprocket and a chain tensioner. Is this not the simplest way?

And taking links out, I dont see how that would make more contact with the sprocket without something being removed... am i wrong?? i assume im wrong

also if anyone wants to just tell me on msn what needs doing my address is thomas_delonge@hotmail.co.uk anyone feel free

Edited May 1, 2007 by himynameisphil

[basher]

The problem looks to be yoou deraliear or how ever you spell it. Either get a fixed tensioner (look on tarty and you will see what one is) and shorten chain or sort that deralier out so your getting more chain rap on rear sprocket. My guess is that if you ran the deralier with 2 jocky wheels and ran it properly so the chain went through it like an s shape as thet are supose to then the problem would stop.

[*PHIL*]

Ok this is great, its going in the bike shop on thursday anyway so i can get them to sort it...

my main question now is, what do i actually need on the bike?

if possible id like to get rid of that derailler and just have a chain tensioner.

any suggestions?

[Krisboats]

If you've got enough money to waste in the bike shop getting them to fit a chain then i'd recommend a rohloff.

Here's my chainline. You want something like this in a perfect world, but i'm just lucky with this, you want to get between mine and simpson (probably a little more towards mine )

[*PHIL*]

If you've got enough money to waste in the bike shop getting them to fit a chain then i'd recommend a rohloff.

Here's my chainline. You want something like this in a perfect world, but i'm just lucky with this, you want to get between mine and simpson (probably a little more towards mine )

hang on.... looks to me like yours is exactly the same as my setup only your chain goes over the tensioner and mine goes under..

could it be that i just need to put the chain on the top of the tensioner?

thanks for getting that pic by the way!!!

Edited May 1, 2007 by himynameisphil

[Krisboats]

Over? No mate, my little cog is attached to the end of the mech arm and is pulling the chain "downwards". Its just REALLY REALLY tight

EDIT: Probably a better angle for you. I've angle grinded the arm off so its out the way and just attached the first cog onto the arm. The chain isn't rubbing on the arm where the other cog used to be.... its just vry close to it... like this close > ||

Edited May 1, 2007 by Krisboats

[*PHIL*]

Over? No mate, my little cog is attached to the end of the mech arm and is pulling the chain "downwards". Its just REALLY REALLY tight

ehhh im sure that picture just changed!! what was i thinking?!?

so what you reckon i should do? keep the derailler and just shorten the chain?

or get rid of derailer, shorten chain and just use tensioner?

[Krisboats]

ehhh im sure that picture just changed!! what was i thinking?!?

so what you reckon i should do? keep the derailler and just shorten the chain?

or get rid of derailer, shorten chain and just use tensioner?

keep the mech for now, pinch the chain links together while its still all attached to get an idea of how many you'd need to take out. It looks like you could get away with taking 3-4 links (pairs of link, the bigger outer plate AND the smalller inner section) out. The mech will work fine as a tensioner for now, and you can look at a different tensioner later.

[*PHIL*]

ok that sounds good but why wait? if thats the best way to have it then fine but i cant see the derailer doing any good as it is rubbing against the frame now and will not stay in place. it keeps moving in and out and i think this is causing the problem..

whats wrong with just removing it?

[basher]

It almost looks like the deralier isnt stretched out enuff. try fiddleing to get it more like in the pic above, by taking links out. And to stop it moving just stick a zip tie around it and the chain stay.

[Krisboats]

ok that sounds good but why wait? if thats the best way to have it then fine but i cant see the derailer doing any good as it is rubbing against the frame now and will not stay in place. it keeps moving in and out and i think this is causing the problem..

whats wrong with just removing it?

take the spring out the mech where the bolt is for the mech hanger. Literally spin the c clip round on the threaded side of the bolt, wedge it off with a flat bladed screwdriver. watch everything try and fly out everywhere. Take the spring out, stick a washer on the end then attach it back to the mech hanger. Stops it bouncing round and making noise... making the bike feel a lot smoother and quiter.

Like this:

And for making the mech easily adjustable and to stop it bouncing entirely, follow my old guide i made a while back. mech bodge guide

Edited May 1, 2007 by Krisboats

[*PHIL*]

It almost looks like the deralier isnt stretched out enuff. try fiddleing to get it more like in the pic above, by taking links out. And to stop it moving just stick a zip tie around it and the chain stay.

i understand that but if i manage to stretch it out there is still gonna be the same contact between the chain and sprocket.

take simpsons picture above for example, the contact on that cant be more than it is on mine right? or is it because its tighter? im just judging by the angle the chain is at when it leaves the sprocket

take the spring out the mech where the bolt is for the mech hanger. Literally spin the c clip round on the threaded side of the bolt, wedge it off with a flat bladed screwdriver. watch everything try and fly out everywhere. Take the spring out, stick a washer on the end then attach it back to the mech hanger. Stops it bouncing round and making noise... making the bike feel a lot smoother and quiter.

sorry to be a pain but im really not that knowledgeable on this stuff. without being cheecky could you explain it in idiot terms for me?.. i.e.. whats a mech? whats a c-clip? where does the washer go??

[Lawnmowerman]

You've got about a 3rd of your chainring being used, shorten your chain, get a shimano dx cog and a kool chain off tarty and it should sort it as the teeth are a lot deeper.

[Krisboats]

Well the difference in your picture is that your mech (rear mech, rear derailleur, rear gear changing device) looks to be all bunched up which means the arm is tucked up into a point where its not tensioning the chain by pushing down on it physically, but by pushing down on it by trying to fold up into itslef. Taking links out will give it a better cahin tensioning ability.

Okay step by step guide.

Take the rear mech off the mech hanger.

Look at the side where the thread is, the bit that goes into the mech hanger.

At the bottom of the threaded section theres a little flat metal clip, thats roughly in the shape of a C

Pry this little clip off by spinning it round to the bit where theres a gap and wedging the flat bladed screw driver into it. It will just slide off.

Slide off the little plate with the screw attached and pull out the spring thats inside the mech body.

Slide a couple of washers over to replace the parts you just took out like the washers on my mech bolt in this picture:

Proceed to attach the mech back onto the hanger, Holding it in place and tightening it up until it wont move in any direction.

Congratulations you've just "locked out" your mech

[Concussion]

Too tired to read all the thread... why is it you don't just run the chain through the mech as normal?

I run two sprockets, normal mech set-up as per millions of bikes, works a treat! Hope you get it sorted... you didn't run your mech like this on your old geared Hardrock did you?

[*PHIL*]

Too tired to read all the thread... why is it you don't just run the chain through the mech as normal?

you didn't run your mech like this on your old geared Hardrock did you?

i dont like the idea of having a derailer if i dont really need one..

and no i had a normal setup on the hardrock, the chain was really loose though

[scousertrials]

Look mate people will tell you all sorts of bodging tips n stuff but best way is to get a specific tensioner ( i do recomend gusset from tarty) shorten your chain to its max, do this befor you put tensioner on as it will allow you to get your chain really short. fit your tensioner. shortening the chain will allow more of the chain to wrap around the sprocket thus more contact between chain and sprocket. BE WISE...

Plus you your bike will shead loads of weight. feel the weight of your drealiuer and compare it to the weight of your tensioner. Aslo the gussett tensioner will attach to both the wheel axle and mech hanger creating a stronger area so if you land on it less chance of snapping your mech hanger. win win situation