I have a racer street bicycle without gears. I want to convert that into a geared one. For that I will need to modify the rear part of the frame where the wheel goes in. Is it advisable to do so?


Depends on just what bicycle it is, but its probably possible to add gears in some way. But it may be expensive or complicated.

First thing to check is the frame spacing, ie the width between the rear dropouts. Many singlespeeds use 120mm wide hubs, whereas modern geared hubs are 130mm (road) or 135mm (mountain bike). If it is a steel frame, then it is usually possible to spring it out a bit, up to about 5mm or so, to fit a wider hub.

If the frame is only 120mm, then your options are limited. There are some internal hub gears for 120mm frames, eg from Sram or Sturmey-Archer. But they are fairly expensive, or have a limited range of gears.

If your frame is wide enough for a 130mm or 135mm hub, then you can use a standard road or mountain bike hub with a cassette.

Then you will need to attach the derailleur. If the frame is designed for singlespeed, it won't have a derailleur hanger. But you can bolt one on, depending on what type of droputs you have. eg if you have horizontal dropouts, you could use this DMR Chain Tugs & Mech Hanger.

Also the frame probably won't have guides for the gear cable. You can buy clamp on cable guides, or you could just use zip-ties to hold the cable in place.

Whether all this is worth it is another question. As you will have to buy quite a few parts (wheel, cassette, derailleur, gear levers etc), which could get expensive. Plus quite a bit of work fitting it all. It may be easier just to buy a bike with gears instead.

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Modifying frame is usually not worth the trouble. Maybe your bike was previously equipped with gears, and it has necessary provisions (derailleur hanger)? If not consider a hub with internal gears. If that is too expensive, consider a new bike.

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  • No, it was never equipped with gears, so it doesn't have provisions. – WedaPashi Jul 15 '14 at 9:58
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    Unless it is emotional issue, like you want to have your grandfathers bike with gears no matter what is the cost, than it is either hub with internal gears, or new frame. – Davorin Ruševljan Jul 15 '14 at 12:11
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    @WedaPashi Just because it didn't come with gears doesn't mean it doesn't meet the necessary requirements. Many bikes are set up and sold as single speeds but easily accept gears. – jimchristie Jul 15 '14 at 18:47

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