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I would like to convert an old (Raleigh A3) mountain bike to fixed gear bike.
But dropout seems to be vertical (or diagonal).
Does such dropout is suitable for fixed gear?
Does "chain tensioner" needed?
The fixed gear with tensioner is it a good idea?
Single speed and a chain tensioner will work no problem
In general, fixed gear in these situations is not a good idea.
It could work if you use a half-link chain and choose your rear cog and front chainring so the size works perfect with the chainstay length. But this will fail over time as the chain wears out and the fit becomes loose.
The issue with chain tensioners and fixed gear is that when you use a spring tensioner and apply forward pedalling pressure, there is no problem, but when you apply backwards pressure, the chain will becaulse loose and will most probably come off. When you stop the forward pressure, the chain will become tight at the bottom (yellow arrow on the picture) and loose at the top.
If you try a non spring tensioner, such as the DMR STS, the forces you generate are stronger than the bolts on the tensioner, so you will be constantly re-adjusting the tensioner.
In my experience, as I already tried this, you would have to fine a chain tensioner which works on the bottom of the chainstay when you pedal forward and one on the top when you put pressure backwards. And non spring tensioner just come loose very easily. I suggest you go down the single speed route and not the fixed gear route.
Good luck and well done for fixing up that frame.
If you really want to do this fixed, the way with no downside other than cost is to get a White eccentric hub.
The "magic gear" setups (using a gear combination in vertical dropouts that's based on exactly ideal gear combinations for the chainstay length) are the other option. It's a little problematic because it's easy for chain stretch to bring you out of the zone where you can get tension, but these setups are capable of working. Start by double checking you would have access to a gear that works for you and avoids skid patch lowest common denominator issues (which may not even be a concern depending on how much you skid).
The White Eccentric Eno hub route may seem extravagant but I enjoyed having one around during the time when I was making random bikes into fixed gears. They're one of those components where once you've handled and ridden it, it's hard to regret buying. You can get endcaps for them in whatever spacing. And, these days it wouldn't be too hard to get one off ebay and resell it when you're done.
That kind of dropout is not suitable for SS fixed. You need at least a little room to adjust the fore/aft of the rear wheel.
I did find these on ebay: https://www.ebay.com/i/154026454119 with a title of
Dropout Adapters Fixed Gear Fixie Road Track Bike Adapter Vertical to Horizontal
Might be worth a try.
A friend of mine tried refabricating the drop out to be same as in the fixed gear frames. It's much better to bring it on a certified frame builder that makes those kind of drop outs so there will be much problem. Hope this helps.
