This pretty much sums it up. With 650B, you can take an off-the-shelf 700c road frame with a geometry you like, shrink the wheel diameter slightly and make up for it with puffier tires. That's about the only advantage of 650B.

This has probably been beaten to death before, but doesn’t a larger tire patch equal more rolling resistance therefore the trade-off being; more comfort, slower ride. This seems like a no-brainer, but I’ve skipped through posts that suggest that this is not necessarily so.

It's actually been shown that wider tires have less rolling resistance.

The length of the patch has more of an effect, since you have to rotate that wheel over the flat length of the patch. Since the wider patch may result in less width it would be more efficient. Trains are efficient because steel wheel do not deflect much so there is no flat part of the patch to overcome. Another argument goes that the comfort being greater on the wider wheel allows the rider to be less fatigued over longer distances.

Arguments to the contrary are that narrow tires can generally take higher pressure which also decreases the length of the flat part of the patch. Narrow wheels are also lighter, but then so are smaller wheels. There less loss to side casing of flex.

In the past I have put Big Apples on a couple of bikes where there was enough clearance for them. The comfort level improved with no noticeable change in speed.
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Interesting, and well informed, Schwinnsta . Makes me think about this topic in a whole new way

Sounds like a great build, I take it this is a frame you're building yourself right?

The picture I posted after your comment (post #20) is of my 650B conversion, for which I used Velocity Synergies with Ultegra rear hub (130mm) and Shimano dynamo hub, shod with 41mm Hetres. I also was concerned about ruining the "vintage" look but I am pleased with the overall outcome, and I've also since that photo updated some of the comps to more modern ones. After a while, one comes to appreciate better technology over vintage aesthetic, and every once in a while the two can come together harmoniously.

Indeed. When properly thought out and executed, as with my PX-8, a full-on modernization can really add legs to a bike that would otherwise end up unused. BTW, I'm not implying this was a 650b or 650a conversion, I'm just trying to show what kinds of results can be had with an old bike, a little planning and some attention to detail.


P1010517 by Sallad Rialb, on Flickr


P1010514 by Sallad Rialb, on Flickr

Honestly a look through that list still only leaves me with one decent 650A tire choice. It seems pointless to me to ride a 23-25mm tire in this size, and the 35-37mm ones are all garbage except the CDLV. OK, maybe the Conti 650Ax37 is decent as well but I wouldn't want Cheng Shins or Kendas or Schwalbe

+10. There are no great 650A tires and few good ones.

I didn't say they were all good choices but was trying to show that there are choices available in 650a. There is some belief by many on this forum that 650a is not a decent candidate for a 27" or 700c conversion, but it is a viable low cost alternative due to the readily available tires and rims in that size.

This is my argument, with me, it is always about the cost.
In converting a 27 x 1 1/4" frame, I worked out that no brakes would reach to 650b without having studs brazed on, which was a non-starter.
Converting to 650a went very well with inexpensive Tektro brakes, and an inexpensive all-alloy wheel set.
The Kenda tires are good enough for my use. I am saving for a set of CDLV, and agree, they seem to be the best to be had for 650a.

Justin,
what is the reach on those front brakes? and I thought I remembered reading that extra long reach brakes don't brake as well. have you found that to be true on this bike? If you're happy, that this might be the piece of the puzzle I've been looking for!

thanks!

Not to answer for Justin, but I've been swapping my Bridgestone 300 back and forth, 650a wheels and Tektro 800A extra long reach brakes, and 700c wheels with dia comp 500 short reach brakes.
The long reach brakes, probably because they are dual pivot, are much better stoppers.

JP, those are just modern Dia Compe 750s. I needed a drop link for the rear caliper. Had I not wanted this bike to look original aside from the wheels I would have went with Tektro dual pivots. David's right, they're just superior to single pivots or centerpulls. They even make some crazy dual pivots for balloon tire bikes with 90-110mm reach or somesuch crazy number.

I have man hands so I don't really have trouble braking with centerpulls and non-aero levers. That said, I prefer the mechanical advantage of aero levers and I don't usually waste time with brake pads that don't have a toe in adjustment feature. I love old school bikes, but adjustable pad holders are a marked improvement and aren't usually an eyesore.

OOO, Justin, that pic belongs in the "one part" thread.

that is a beautiful bike

Thanks himespau... In spite of it's French attitude (or maybe it is because of it), I'm quite fond of this bike and would like to ride it more than I do.

Justin, did you make the drop link or is that something you can get off the shelf?

I didn't make it. It was gifted to me by my odd part benefactor, fender1. I think he found it on a vintage Paramount. It's steel, I just polished it. I think it was intended to be used the other way around, but I scratched my head and looked at hit really hard and figured out how it'd work for me.

I suppose the same could hold true for a 27 to 700 conversion - a little more room for tires and mudguards.

Yes but much less so. The nominal difference in radius between similar width 700 and 27" tires is only a few mm.

Some touring and sport touring bikes from the 80's have higher bottom brackets than others. Miyata and many bikes made by the such as Univegas and some Specializeds had higher BBs than Treks.

Weinmann and Dia-Comp 750 centerpulls have sufficuient reach on many frames built for 27" tires. It all depends on where the holes in the fork crown and the rear brake bridge are.

wow, really? I've never tried a Trek tourer but its hard for me to imagine a BB lower than on a Miyata 1000LT. I'd feel like I was really draggin azz!

The 1984 Miyata catalogue lists the BB drop for their touring models as 65mm. Trek 620s and630s, had a drop of 72mm. Miyata 1000s are not good candidates for conversion because they are pretty close to perfect the way they are.