Rear drop-outs question..

[morphix]

I'm hoping someone with a bit of experience maintaining bikes can help me with this one, couldn't find any definitive answers online...

I've just changed the tyres on my bike and also adjusted the gears (previously downgraded from 21-speed to 7-speed)... now, when I put the rear wheel back in the drop-outs, I found that it was too close to the frame (almost touching) and also the brake shoes (V-brakes) were too high and slightly above the rim..

My solution to these two problems was to bring the rear wheel more forward in the horizontal drop-outs and that has nicely solved both problems.. however the wheel is quite a bit more forward now than I'm perhaps comfortable with, and I'm wondering if this risky at all?

Here's a couple of pictures so you can see what I mean..

Maybe I'm worrying about nothing?

Here you can see the space between the wheel and the frame with the wheel where it's position above on the drop-outs. Putting the wheel any further back causes the space to become too close...

 

[Mussels]

I can't see a problem with that, your chain tensioner will take up the slack.

 

[flecc]

Yours is really the wrong sort of frame for derailleur gears, they are usually with frames that have a true drop-out, a vertical slot with no adjustment, since no chain adjustment is needed. Your frame is the type used with single speed or hub gear bikes to give chain adjustment.

However that's not a big problem, neither is the position of the spindle in the slots since they are meant for mounting anywhere along them.

The correct ways to adjust for the two problems you observed are these:

For the brake pad position, adjusting them in their slots to register correctly with the rim.

For the rim too much to one side, re-truing the wheel by spoke adjustments to "dish" it so that the rim is slightly out of line with the hub centre but central in the frame members. However, make sure that the rear wheel is straight in line with the front wheel first and not at an angle to the rest of the bike before taking this action.

Your bike will work ok as it is, but the correct solutions are better.
.

 

[morphix]

Thanks guys, that's reassuring to know.. I should of explained better that I did try adjusting the brake block position but even at the very bottom of the slot it was still too high so then bringing the wheel forward seemed the only way..

I figured I might need to true the wheel as I checked it and it didn't look very true to me, but I was reluctant to try as I never done that before..guess there's always a first time will have to give it a go when I have time..

I have removed the forward gears derailleur cage since I removed the forward gears..it just seemed to be redundant and getting in the way..

I also have set the chain on the middle chainset sprocket which I believe is correct for a full range of gears..

 

[flecc]

Yes, middle sprocket chain alignment is the norm if the full range of gears is used, though on e-bikes I like mine set slightly to the smaller sprockets since lower gears get less use on power assisted bikes.

If you haven't done wheel building before, it's best that dishing the wheel is done by a bike shop mechanic. Shops that bias to the sport bikes the lycra brigade use are very familiar with doing this since their bikes often have a large offset. Here's a motor wheel on my bike that has a large side offset for the rim, well out line with the hub centre to get the rim central in the frame:

 

[Mussels]

The front cage might not beer redundant as it helps stop the chain coming off.
Why do you think your wheel is out if true?

 

[morphix]

The front cage might not beer redundant as it helps stop the chain coming off.
Why do you think your wheel is out if true?

Hi Mussels, I haven't had any probs with chain coming off so far, but early days..

I think the wheel is not perfectly true, how much out it is, and how much difference truing it would make to the frame proximity problem I don't know, it doesn't look too bad to me and my instinct is it won't make much difference to the problem.

Flecc said the frame is not designed for derailleur gears, and looking at the frame at the rear I have to agree that 7 gear cogset looks to be too much for this frame width.. I could fit 3-speed hub gears but I'm not sure it's worth the cost on this particular bike, on a 20" build I definitely would.

Also, I prefer to ride in 6th or 7th gear under power, using 6th for hills and 7th for the flat. I like a lot of torque and the largest chainset cog works best for me..although this makes for a fast, easy to ride bike under power, it also results in a completely impossible to ride bike without power.

I can't ride the bike comfortably with the chain on middle cog in the cogset which would provide the full range of gears and the flexibility of a powered and unpowered ridable bike. There's just not enough torque there. Maybe tightening the chain will solve all, and then middle cog will be ok.

 

[morphix]

The front cage might not beer redundant as it helps stop the chain coming off.
Why do you think your wheel is out if true?

Hi Mussels, I haven't had any probs with chain coming off so far, but early days..

I think the wheel is not perfectly true, how much out it is, and how much difference truing it would make to the frame proximity problem I don't know, it doesn't look too bad to me and my instinct is it won't make much difference to the problem.

Flecc said the frame is not designed for derailleur gears, and looking at the frame at the rear I have to agree that 7 gear cogset too much for this frame.. I could fit 3-speed hub gears but I'm not sure it's worth the cost on this particular bike, on a 20" build I definitely would.

I prefer to ride in 6th or 7th gear under power, using 6th for hills and 7th for the flat. I like a lot of torque and the largest chainset cog works best for me..although this makes for a fast, easy to ride bike under power, it also makes for a completely impossible to bike without power.

 

[morphix]

Is the chain too loose?

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Here is a quick video I made showing the slack in the chain... do you think it's too loose?

 

[NRG]

In a word.....no....

 

[flecc]

That's fine, not excessive at all. It's impossible to vary the chain tension by wheel adjustment with derailleur gears anyway, that's controlled by the rear mechanism.
.

 

[morphix]

Thanks

Thanks guys!