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Old 07-21-10, 12:30 PM   #1
tm8703
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Converting from 18 speed to 5 (or 3)

Hi all,

I'm not much in the way of bike mechanics (although i'm starting to learn) so thought someone here might be able to help me out.

I would like to convert an 18 speed Trek 700 Hybrid down to a 5 or 3 speed. Is this possible to do...without spending what the bike is worth and being a master mechanic? I'd toyed with the idea of single speed but don't think this would work too well with the type of commute I have.

I don't know what I don't know so any help or advice would be most appreciated. Thanks.
T
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Old 07-21-10, 01:49 PM   #2
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..I would like to convert an 18 speed Trek 700 Hybrid down to a 5 or 3 speed....
Why? What are you hoping to gain by that? You won't be able to ditch any significant amount of hardware, so the bike will still weigh and look pretty much the same.

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... Is this possible to do....
Sure.

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......without spending what the bike is worth....
Depends on how slick you want the fix to be, there are several options:
1) turn it into a 6-speed. Leave the rear derailer as is, see if the end stop screws are enough to lock the FD in place over one chain ring. The middle might be your best bet. It is possible to remove the FD, but there's a risk that the chain will drop off with an annoyingly high frequency.
2) as an encore you can then twiddle the limit screws for the RD, tuning out a gear or two from either end. maybe reduce it down to 4-speed or whatever the limit screws lets you.
3) lock the RD in place, either by the limit screws or by using a short length of cable( one end clamped at the RD, the other resting against the in-line adjuster) and leave the FD alone. Instant 3-speed.

If you lock the RD down you can in theory remove a couple of sprockets, but IMO it wouldn't be worth the effort. Very little gains in aestethics or weight for some awkward work in disassembling a cassette/freehub and getting it back together again.

But as you see, that kind of fiddling isn't really doing much for you apart from reducing your options in terms of gearing range. Even going to an IGH is a so-so solution, and won't save you any particular amount of hardware unless your bikes have horizontal dropouts.
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Old 07-21-10, 02:34 PM   #3
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Thanks for the input. I am really just trying to reduce weight where I can.

Do you think going single speed would be a substantial reduction in weight? Any suggestions if not?

Thanks again
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Old 07-21-10, 03:20 PM   #4
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You won't see a significant decrease in weight by going single speed. At best you'll remove a few ounces.

If for some perverted reason you want to go to a 6 x 1 setup then you can ditch the big front ring and the small granny ring and run with the middle ring and no front derrailleur. I've been riding a bike set up this way for years now and I can't remember if it has ever thrown the chain on the road at all. It MAY have done so during a trail ride but that is so rare that I can't remember it doing this.

In my case I did it that way because I ran out of parts while building up this particular frame and found that I didn't need another front ring for the way this particular bike is ridden.

You want a suggestion for a lighter bike? There is only one that is worth the time and money. And that is to switch the tires over to a set of 1.25 to 1.5 inch smooth slicks such as Ritchey Tom Slick tires. Nothing else you can do to a basic bottom of the food chain 18 speed bike is going to do anything worth while. But switching to such tires will give you an amazing boost for road riding. If you trail ride then sorry. There is nothing to do other than selling your bike and buying something more costly and exotic. Removing a few ounces here and there won't mean diddly. Being an 18 speed it suggests to me that it is a very basic bike that comes with a very heavy frame and likely one made using high tensile steel. Moving up to a much lighter and at the same time stiffer chrome moly frame is what you need. But at the same time you would likely want to upgrade everything else. Hence the suggestion to save your money and invest in a better all around bike.
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Old 07-21-10, 08:23 PM   #5
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You won't see a significant decrease in weight by going single speed. At best you'll remove a few ounces.

If for some perverted reason you want to go to a 6 x 1 setup then you can ditch the big front ring and the small granny ring and run with the middle ring and no front derrailleur. I've been riding a bike set up this way for years now and I can't remember if it has ever thrown the chain on the road at all. It MAY have done so during a trail ride but that is so rare that I can't remember it doing this.

In my case I did it that way because I ran out of parts while building up this particular frame and found that I didn't need another front ring for the way this particular bike is ridden.

You want a suggestion for a lighter bike? There is only one that is worth the time and money. And that is to switch the tires over to a set of 1.25 to 1.5 inch smooth slicks such as Ritchey Tom Slick tires. Nothing else you can do to a basic bottom of the food chain 18 speed bike is going to do anything worth while. But switching to such tires will give you an amazing boost for road riding. If you trail ride then sorry. There is nothing to do other than selling your bike and buying something more costly and exotic. Removing a few ounces here and there won't mean diddly. Being an 18 speed it suggests to me that it is a very basic bike that comes with a very heavy frame and likely one made using high tensile steel. Moving up to a much lighter and at the same time stiffer chrome moly frame is what you need. But at the same time you would likely want to upgrade everything else. Hence the suggestion to save your money and invest in a better all around bike.
I have to disagree with this somewhat. I took a 32 lb nishiki century and rebuilt it and got it down to 24 lbs and took it to a 21 speed from a 10 speed. It's an old high ten frame. Turning his hybrid into a proper single speed will absolutely shave a fair amount of weight. No front or rear derailiers aswell as no shifters is gonna take a lot of weight down. new rear wheel without a full casette will shave weight. Many single speed guys only go with front brake so eliminate rear brake and you've stripped a lot down.

With that said, I don't think this is the bike to do it to. if you want a light single speed, do what most people do and look for a beat up old vintage frame and just build it up piecemeal. I'm sure there are times when all the gears on your hybrid come in handy. simply removing your front derailer isn't going to take enough weight off and you'll lose the advantage of lower gears for the hills and tall gears for the downhills.

If you only do on road riding with your hybrid, you could probably shave weight by going to a threadless setup and getting a carbon fork on the front and regular mtb style flat bars. if your trek is the bike i'm thinking of, I picture a humongous quill stemm sticking up with big riser bars. a more road like front end would probably work wonders. Drop bars even to get you aerodymanic and set it up like a cyclocross bike could work well too. I know that a lot of the speed i'm getting on my new bike is from aerodynamic improvement now weight.

I don't know how clear the pics will be but the first bike is what ibought for $40. The second pic is it in a near completed state. I spent a few hundred but i went overboard. you can remove the cranks and get a single crank up front off of ebay for under $50. New rear single speed wheel for around $80. I went with nashbar carbon threadless fork which was $75 bucks, new stem and bars and headset were only $50 bucks (ebay again)


If your bike is anything like the one here you could do what this guy did but it could start getting costly if you don't have parts already. going ot drop bars would be great but sti levers are expensive so you would probably want to go with barend shifters liek he did or downtube shifters.

I think there are a lot of ways you can go with this and there probably are some improvements that can be made to that existing bike but at the same time, it's probably never gonna be a world beater.
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Last edited by CPFITNESS; 07-21-10 at 08:28 PM.
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Old 07-21-10, 11:21 PM   #6
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CP, you did a LOT of extra work there. But really if you look at the weight of shifters, derrailleurs, crankset rings and rear sprockets and shortened chain removed we're talking MAYBE 2 lbs to swing over to a single speed. And more likely 1.5 to 1.7 lbs. In the grand scheme of things this is pretty much didly when we look at the weight of the bike and rider.

But I do agree that if it's done as part of an overall diet to the bike then some good things can result.
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