Converting derailleur to IGH
 

Ok, I did a quick search and didn't see this already, so sorry if I missed a thread on this topic.

I'm debating between two bicycles- same frame-style, but different drop-outs. One is a 7 speed utilizing derailleurs (and thus, vertical drop-outs), the other has a 3-speed IGH and horizontal drop-outs.

I am heavily leaning to the 7-speed, because I need those extra gears to tackle my town's hills. Also, its $100 cheaper than the 3 speed (because of the 3 speed's IGH). What I want to be able to do is get the 7-speed and use it until the derailleurs fail, then convert it to an 8speed IGH.

Problem is, as I'm looking into how this is done (I'm a newbie, patience please if I get this wrong!), it seems that I would not be able to do that, because derailleur systems use the vertical drop-out types, but IGHs need horizontal ones (something to do with chain tension?)

So, is this doable? Has anyone here converted a derailleur system to an IGH, and if so, how? Or will I have to spend the extra $100 for the 3 speed bike, and struggle with the lack of additional gears until I can save up for an 8 speed IGH? Obviously, I really don't want to do that...the 7 speeds would be greatly appreciated in the interim as I save up for the 8 speed IGH.

*also, please don't advise that I just find another bike. I really like this one and its the one I want! :P

Thanks in advance!

I guess I should also add that as I am a student, cost is a significant part of the consideration. So, while the 3 speed is $100 more, would it cost me *more* to make the necessary adjustments/buy additional parts for an 8spd IGH to fit vertical drop-outs? Obviously this is disregarding the cost of the 8spd hub itself, because I would have to buy that for either bike.

*Edit- I did find another post that briefly talks about this. However, I'm still slightly confused, and the concern about cost remains. So if anyone is willing to talk me through it still, and give approximate costs, that would be much appreciated! Thanks!

I don't see any major problems -- the chain tension issue can be dealt with by using a chain tensioner (basically a derailleur that doesn't shift).

But unless the derailleurs are utter garbage, I suspect they'll last a good long time with a little TLC.

Using a IGH in a bike with vertical dropouts requires some method of tensioning the chain. If you're lucky, you can get the right # of teeth on the front chainring and rear cog, and it will work out right, the magic combo. A half link in the chain might be required. There on some online calculators that you can use to determine the right combo. The chainstay length is a variable. Otherwise you'll need to use a tensioner. This would allow you to use 2 chainrings and a derailleur up front, if you wanted more gear range.

You will be able to make the switch in either case, but if you go with the 3sp, check to make sure the frame is either 130 or 135 mm spacing at the rear dropout.

If you start with the three speed, you won't have to get a chain tensioner.

If you go with the 7sp, you can use the existing derailleur as a tensioner.

Only issue is aesthetics of a chain tensioner on a IGH bike--if you want the clean look and no unnecessary complications, the three speed would be better; if you can live with a tensioner, the 7sp will suffice.

Also, the three speed might have better existing cable routing and guides for future IGH cable/housing.

Just when you do decide to upgrade, get the anti-rotation washers to match you dropout style.

Or, you can get and eccentric bottom bracket which allows some chain adjustment with vertical rear dropouts.
Prices vary. Here is one.
http://www.philwood.com/products/bbpages/eccentric.php
You still might have to use a half link, depending.

Thanks for the info all! This is very helpful; it looks as though when the day comes to make the conversion, it should be pretty simple and not as expensive as I expected (sans the cost of the IGH itself).

Thanks again!