Suntour SR chainring - 'short' teeth

Shadowduck

I'm never sure whether to post in road or MTB, with the bike being a hybrid. Anyway...

My chain's hopped off the sprocket at the front a couple of times lately. With it being a single chainring there's no gearchange to be causing problems, so I've just taken the sprocket off and had a look at it - four or five teeth were bent slightly over to one side! Not a clue how that's happened but I've eased them straight in the vice and all seems well.

While I've got the sprocket off, I've noticed there are two pairs of teeth, on opposite sides of the sprocket, which are half the height of all the others. So my question is - is this normal? It's definitely been made that way (rather than worn or damaged) as the black finish extends right the way to the tip of the short teeth. The whole sprocket looks like a very cheaply made piece of *expletive* so I wouldn't be surprised if it's just a manufacturing defect, but if there's some good reason (easier gear changing?) I'd be interested to know what it is!

onbike 1939

<While I've got the sprocket off, I've noticed there are two pairs of teeth, on opposite sides of the sprocket, which are half the height of all the others.>

The teeth in question are designed that way, usually to assist changing from one chain-ring to another. Even although yours is a single chain-ring I would imagine that this is the case. I'm taking it to mean that by "sprocket", you mean "chain-ring".

Shadowduck

onbike 1939 wrote:

<While I've got the sprocket off, I've noticed there are two pairs of teeth, on opposite sides of the sprocket, which are half the height of all the others.>

The teeth in question are designed that way, usually to assist changing from one chain-ring to another. Even although yours is a single chain-ring I would imagine that this is the case. I'm taking it to mean that by "sprocket", you mean "chain-ring".

Aye - I learnt what a sprocket was a long time before I learnt that they're called "chain-rings" on bikes, so I tend to forget and use the generic name. My apologies and thanks for the answer. :oops:

acorn_user

Is that an Edinburgh bikes bike? If you need a replacement ring, you should look into the TA Specialities cyclocross single rings. They are not ramped or pinned.

Shadowduck

acorn_user wrote:

Is that an Edinburgh bikes bike? If you need a replacement ring, you should look into the TA Specialities cyclocross single rings. They are not ramped or pinned.

It is indeed - a Revolution Courier Race, though how you deduced that from the information above I'll never know! :shock:

After my attempts to straighten the chainring, the chain now comes off within a few hundred yards if I try to use 7th or 8th gear - I think I overcompensated a little so I'm going to have another go at straightening it today. Oddly enough, coming home with only six gears and stopping three times to put the chain back on, I was only 45 seconds over my personal best for that run! This makes me think I'm doing something wrong normally, though the route is fairly hilly so the top gears don't get that much use.

It does look like I may be needing a replacement so if I can find anywhere selling the TA cyclocross rings I'll take a look. The only supplier of TA I can find in the UK is Dotbike but they have a baffling array of chainrings which doesn't appear to include cyclocross ones. The current one is a 4-arm 44T fitted inboard of the crank, but I'm not at all sure what I should order to replace it. Fingers crossed I can sort the one I've got.

And to think I chose a single chain ring on the basis that simple = reliable. :roll:

andrew_s

4-arm single chainrings from St John St

Shadowduck

andrew_s wrote:

4-arm single chainrings from St John St

Ooooh, that looks just the job - cheaper than most I've looked at, too!

Thangyew berry much!