Vertical Dropouts

Oh and BB height isn't really an issue (unless you're riding a touring frame design for 27" wheels), just choose the right pedal, i.e. not those wide BMX one that's likely to scrap the floor when cornering slightly.

Is there a difference between vertical and semivertical dropouts when considering converting?
e.g. does a semivertical dropout give you more change for a magicgear to work compared to a vertical one?

Is there a difference between vertical and semivertical dropouts when considering converting?
e.g. does a semivertical dropout give you more change for a magicgear to work compared to a vertical one?

Yes.

Vertical = I

Senivertical = /

Really?
The dropouts on my TT frame look like this:

Do you think i can make this work without an Eno Eccentric Hub and just by finding my magic gear using " http://eehouse.org/fixin/formfmu.php " ?

Does anyone have any ideas on how to measure the chainstay length btw? I'm measuring a different length almost every time with a 2 mm. difference...

You should (just) be able to run any gearing you please using a half link chain, and being careful when getting the chain to the right length IMO.

Yeah that should be fine.

Mine dropout is like that if not more vertical, I use a half link chain and it's fine.

wow, that's better news than expected...
but still, if i take a look at my FixMeUp-Graph, i can't really run (just almost) any gear right?
I would still be limited by the vertical blue line, but then maybe with a difference of 1 or 2 mm.?

Was thinking about using my 52 chainwheel, but that would make skidding pretty hard won't it?
Want a bike with a little more speed in it than my other bike (46x16)...
(sorry 'bout the large graph, couldn't attach for some reason)

Think that's bollocks to be Honest. however I ride 52x18 and think its perfect for riding round the hills of Yorkshire, tough at times but perfect.

google rabbit calculator, that will sort your skid patches etc and combos for relevant gear inches. In general a prime number of teeth on the rear is best for skidding.

52:18 is almost the same as 46:16 (76.2 inches vs 75.8)

I think the semi-vertical dropouts are designed to have the axle right at the back. They are not meant for adjusting the effective chainstay length. The nut will start losing contact area quite quickly if you move the wheel forward.

Why's that s.walrus?

semi vert drop outs are designed so you can get the wheel out quickly for punctures

Why's that s.walrus?

Because it would be rather poor engineering. All the weight of the bike+rider, and every bump will be trying to push the axle up, which would stretch at the chain, and cause lots of wear and loss of power. Also if the axle is knocked upwards, there is a reasonable chance it will turn and the nut can loosen. Also, as I said, as you 'adjust' the axle down and forward you very quickly start getting less contact area for the nuts.
Straight vertical drop outs will slightly tighten the chain as you drop the wheel out, whereas semi-verticals will loosen it slightly, so would be ideal for fixed gears / non-tensioned hub gears with ecentric BB or hubs. I can't see any advantage either way with deraileurs or other tensioners. If you want to be able to move the axle back and forth, horizontal movement is what you want.

(disclaimer - this is speculative and largely based on experience with nuts and bolts in general, rather with axle nuts and dropouts specifically)

i want to do this for my olmo?
anybody know anywhere in london to get this done?
and how much roughly?

Oak Cycles... Ask for The Colonel...

Family sized bucket please.

First, I know there are a few threads on this theme around the forum - I have read them, and hope that this post doesn't upset too many people by going over covered ground.

Right, to the issue... I've just finished doing a fixed conversion with the aim of creating a city runaround that won't look too desirable for someone to steal, but is secretly a lovely bike. However, the frame has vertical dropouts with almost no wiggle-room whatsoever, so I've had a really tough time getting the right chain tension.

Using a half-link I've managed to get it to a rideable tension, but any indecision or sudden change in cadence and the chain has a tendency to fall off - so I need to do more work to tighten it up.

I don't want to buy an ENO hub unless I really have to, and want a solution that's a little more flexible than finding a magic gear ratio - so the only other option I've been considering is filing the dropouts a bit. However, I'm really nervous about doing this, so thought I'd post this thread with a picture of the dropouts just to check with you guys that it would be OK to go ahead with this plan.

Taking the extra half-link I've used out again makes the chain too short, and with it in then it's slightly too long - so I'm assuming that I only have to move the axle back maybe 8 or 9mm to fix the problem. There should be just enough room for this (see attached picture), but I'm really concerned that this will cause the dropouts to fracture in the near future. What do you think? Is there anything I've overlooked that could be problematic in filing these back?

Also, is there anything else I could do instead that would be less destructive?

Thanks in advance for any comments - I've been viewing this site for a while, but this is my first time asking a question.

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Whats the frame? You might be able to get a new hanger ?

http://www.evanscycles.com/categories/bike-components-bike-parts/derailleur-hangers

Any reason you don't want to use a chain tensioner? Looks?

Huh, definitely hadn't thought of that. It's a Diamondback frame from about 10 years ago - good condition, but cosmetically in a bad state (hence the hope it won't get stolen...) so I can't determine any details as to the exact model. I believe it was originally intended as some sort of standard hybrid type frame but may be wrong. Any idea on compatibility issues with the hangers listed? And wouldn't replacing the hanger just give more room on one side of the axle?

Any reason you don't want to use a chain tensioner? Looks?

I thought chain tensioners were only an option for single-speed; am I wrong? Definitely want to keep it fixed...

Oh aye. My bad.

Huh, definitely hadn't thought of that. It's a Diamondback frame from about 10 years ago - good condition, but cosmetically in a bad state (hence the hope it won't get stolen...) so I can't determine any details as to the exact model. I believe it was originally intended as some sort of standard hybrid type frame but may be wrong. Any idea on compatibility issues with the hangers listed? And wouldn't replacing the hanger just give more room on one side of the axle?

True, hadn't thought of that... what does the other side look like? i would imagine that willl be thinner / more likely to crack than the drive side?
I would say it is unadvisable to file away the dropouts, especially a removable one (which is designed to break in order to save the frame in a big crash).

I would say, just keep looking for a magic gear, ask around, borrow some chainrings / sprockets and play with it...

What's the chainline like? If you can get a perfect chainline then a slightly slack chain might be ok, depending of course on just how slack... any pics?