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650b conversion questions

Old 11-05-11, 10:46 PM
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650b conversion questions

I just got back my 1995 Trek 730 and I plan to use it both as my main rider and as a project bike. I've always thought the frame is a bit on the small side for 700c tires and since I'm open to replacing any and all parts and definately plan to replace the wheels and tires, why not consider a 650b conversion?

I followed the guidelines on Rivendell Bicycle Works website to get a general idea of whether it would physically work on my bike and it seems like going by their criteria, it would. However, I know nothing about bike mechanics so I may be misinterpreting this.

If a 650b conversion would work and I do it, what differences might I expect in the way the bike rides? More stable? Less stable? I plan to put relatively fat tires on it regardless of what I do. Will fatter 650b's make up for the rougher ride from smaller diameter wheels?

Are there other major (or minor) factors that I'm failing to consider?

I'm just in the planning stage right now with no decisions made so I would be interested in experienced folks' input.

I recently came across this 17" Multitrack (mine is 19") that is converted to 26" wheels and the proportions now look very good!





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Old 11-05-11, 10:53 PM
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I don't think you have anything to gain from going to 650B. You can already mount fatter tires and fenders.

What you propose is not a typical 650B conversion.
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Old 11-06-11, 07:18 AM
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How do you plan to handle the brake reach problem? The radial difference between 700C (ISO 622) and 650B (ISO 584) rims is 19 mm and most brakes don't have nearly that range of adjustment.
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Old 11-06-11, 08:10 AM
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Rivendell's information indicates that anything up to the 380's will work with one of the brakes they sell. I can only take their word for it but anyway, right now I'm just looking for general information or other people's experiences. If I decide that I'm likely to go this route I will probably take to the bike to a local shop and start getting really specific on what needs done.
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Old 11-06-11, 09:34 AM
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I agree with Puget_Pounder. What do you hope to gain by this conversion? Beside the brake challenges and tire selection and availability constraints you will impose, you will lose bottom bracket clearance and increase the probability of pedal strike. What, exactly, is the upside? There may be I just can't identify it. I'd be interested to hear your rationale.
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Old 11-06-11, 10:20 AM
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I guess I'm trying to figure out if there are any upsides. I guess what I'm hoping for is better handling and a smoother ride based on the changing geometries. Also, aesthetics come into play although they are secondary to function.
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Old 11-06-11, 12:28 PM
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Aesthetics are kind of a wash, but function is going to be the real problem. You appear to have cantilever brakes, which usually don't have the adjustment needed to do a 650b swap.

If you can already mount larger tires, I don't see the purpose. The change in geometry isn't really worth it, bikes usually ride better when they are ridden within the parameters they were designed for.
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Old 11-06-11, 12:57 PM
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Originally Posted by corwin1968
I guess I'm trying to figure out if there are any upsides. I guess what I'm hoping for is better handling and a smoother ride based on the changing geometries. Also, aesthetics come into play although they are secondary to function.
650b isnt some magical thing. it just allows wider tires.
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Old 11-06-11, 01:57 PM
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are you sure the frame isn't just small for you? I also agree I see little to gain from the 650 bit and also brake reach (unless you plan to abandon the cantilevers) will be a huge headache
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Old 11-06-11, 05:23 PM
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The frame may well be too small. It's a 19" and LBS sized me to it back in 1995 and another LBS sized me to a 20" Trek 7.2 FX in 2007, which is a very similar bike. Since the sizing changed between the two models, the LBS's were pretty consistent in sizing me. I would like to try a 21" multitrack but finding one local or nearby has been difficult.

It sounds as if there really isn't any upsides to going 650B so I guess that pretty much answers my questions.
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Old 11-06-11, 06:00 PM
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I would also wonder if the bike is too small. THe seatpost is waaa-aay out of the frame, and you seem to have changed the bars and jacked the stem all the way up to keep it high enough.

Just curious - do you ever feel like you have too much pressure on you hands, or do your hands go numb often whey you ride?

Edit: Also, seems like a lot of trouble to go through for a 16 year old Taiwanese made steel frame.
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Old 11-06-11, 08:55 PM
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Originally Posted by corwin1968
The frame may well be too small. It's a 19" and LBS sized me to it back in 1995 and another LBS sized me to a 20" Trek 7.2 FX in 2007...
Think reach.
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Old 11-06-11, 10:44 PM
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Bike has cantilever studs on the frame and fork. Since the reach is in the wrong direction, you cannot use any brakes that mount on the cantilever studs. Going from a bike designed for 650b with cantilever studs to any larger rim size can be accommodated with the appropriate brake (Paul Component's Moto-lite BMX for example) You can probably mount a side pull caliper style brake to the fork. There might be a mount in the brake bridge between the seat stays. You could have the cantilever studs moved by someone with competent brazing/welding skills, but a repaint would be necessary and you could probably buy whatever other frame there is to meet your needs for the cost involved.

You could use drum brakes. No reach problems there. Sturmey Archer has a cassette drum brake. They have front drum brakes. Choices in 650b rims is slim and expensive, though drum brakes would make for more choices rim wise (there are disc specific 650b rims). Consider 650a (iso 590) also. The don't have a lot of rim selection either, but there is the Sun CR-18 in that size now. Tire selection is also on the slim size.
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Old 11-07-11, 08:44 AM
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Originally Posted by krome
Consider 650a (iso 590) also. Tire selection is also on the slim size.
It's been about six months since I've run through this, but at that time I found the following ISO590mm a.k.a. 26x1 3/8 a.k.a. EA.3 a.k.a. 650A tires available on the web, at my LBS, at hardware stores or at big box stores:

Bell Sports Streetster (folding)
Chengshin C638
Continental City Ride
Hutchinson Junior
Innova Cloud Nine
IRC Super Gold
IRC Super Seed
IRC City POPS
Kenda gumwall
Kenda Cross (knobby)
Kenda K40 Street
Michelin World Tour
Nutrak Traditional
Nu-teck (airless)
Panaracer Col de Vie
Panaracer ST Daily Commuting
Pyramid gumwall
Pyramid Sunlite Hybrid Nimbus
Raleigh Record (NOS)
Rubena Flash V66
Schwalbe Delta Cruiser (available in cream color)
Schwalbe Marathon
Schwalbe Marathon Plus
Schwalbe Speedway Pro (knobby)
Specialized TriSport
Vittoria Randonneur
Vredestein Perfect Tour
Vredestein Dynamic Tour
Vredestein Classic

hth
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Old 11-07-11, 11:26 AM
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Originally Posted by tcs
It's been about six months since I've run through this, but at that time I found the following ISO590mm a.k.a. 26x1 3/8 a.k.a. EA.3 a.k.a. 650A tires available on the web, at my LBS, at hardware stores or at big box stores:

Bell Sports Streetster (folding)
Chengshin C638
Continental City Ride
Hutchinson Junior
Innova Cloud Nine
IRC Super Gold
IRC Super Seed
IRC City POPS
Kenda gumwall
Kenda Cross (knobby)
Kenda K40 Street
Michelin World Tour
Nutrak Traditional
Nu-teck (airless)
Panaracer Col de Vie
Panaracer ST Daily Commuting
Pyramid gumwall
Pyramid Sunlite Hybrid Nimbus
Raleigh Record (NOS)
Rubena Flash V66
Schwalbe Delta Cruiser (available in cream color)
Schwalbe Marathon
Schwalbe Marathon Plus
Schwalbe Speedway Pro (knobby)
Specialized TriSport
Vittoria Randonneur
Vredestein Perfect Tour
Vredestein Dynamic Tour
Vredestein Classic

hth
I meant slim as in 650b slim. There might be more selection in 650a, but both 650a and 650b have what I would call, slim selection, in comparison to 700c or 559 (26" MTB). I have some 650a tired bikes and 650b tired bikes. Tire selection, on the whole is slim. I'm perfectly happy with what is available, but I still consider those sizes, along with others (not iso 622 or 559) as having a slim selection.
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