How much tire width gain to justify 650b conversion?

[Andy Beichler]

I converted one of my 71 Raleigh Internationals to 650bx42 from 700cx35 to give me easier fender clearance and a little more cush. I also converted it to low trail. At some point I will have cantilever bosses and a few other frame tweaks.  I am having fun with it.

I now have a Raleigh Super Tourer that takes 700cx40 with fenders. The clearance isn't great with fenders but it is enough.  Since I already have the 650bx42 wheelset available, I put them on the Super Tourer to check the clearance.  They fit and created better fender clearance, but I don't think it is with the trouble to convert it permanently to add 2mm of tire. 

All this left me curious of what other folks consider enough width gain to justify the conversion?

[Dan Vee]

The bb height will lower considerably going from 700x40 to 650bx42. Whether that is a positive or negative is up to you. The handling will also be different.  

--
You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/650b/1e437505-cc32-4b2b-bf2a-18c01692fc2en%40googlegroups.com.

[randal...@gmail.com]

8mm+, the smaller wheel has to overcome lower rollover ability so I don't consider anything less. 650bx42 feels nothing like 700cx42 and much more like 700cx35, IMO.

[Guy Jett]

I'm converting my '74 Raleigh Competition from 27-inch rims (originally tubulars). I would like to go to 650b, but have concerns with brake reach. The longer original Weinmann 750s are a bit too short. 

Any recommendations for caliper-type brakes that might fit?  I've come up blank on the Internet. 

My other alternative is to go to 700cx38, but the 650b's would lower the bottom bracket 1/2 inch to match my Homer and give slightly lower gears. 

Thanks to all,

GAJett

To view this discussion visit https://groups.google.com/d/msgid/650b/CAAA20G4zL6R3073TaAvhp2UvMf23PvaxQt_18hdkOFOphBWn1Q%40mail.gmail.com.

Guy

[Andy Beichler]

I can’t guarantee it will work in your competition, but in my International, I am using Tektro 559’s with b dop pad droppers. They work great but eventually I will add cantilever bosses. 

[Bernard Duhon]

If you get B drop Pad droppers, be careful if your tire is too wide the pad holder will wear through the tire.

I have modified the droppers by grinding off part of them. Also, I’ve found an extra thick brake pad that keeps the pad holder away from the tire. Of course I had to modify the pad to fit in the B drop. A lot of BMX pads  are extra thick, but don’t necessarily fit a road brake pad holder unless modified

Get Outlook for iOS

---

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Andy Beichler <andybe...@gmail.com>
Sent: Sunday, December 14, 2025 2:37:46 PM
To: Guy Jett <guy4...@gmail.com>
Cc: Dan Vee <dane...@gmail.com>; 650b <65...@googlegroups.com>
Subject: Re: [650B] How much tire width gain to justify 650b conversion?

 

To view this discussion visit https://groups.google.com/d/msgid/650b/CAJUNOY%2BQe66fDkVFsi4MfPnLAZog-CfWL2xqNS1TGdCuTCWJ%3Dw%40mail.gmail.com.

[njh...@gmail.com]

On Monday, 15 December 2025 at 4:50:09 am UTC+11 guy4...@gmail.com wrote:

I'm converting my '74 Raleigh Competition from 27-inch rims (originally tubulars). I would like to go to 650b, but have concerns with brake reach. The longer original Weinmann 750s are a bit too short. 

If it was originally running tubulars then those rims are the same size as 622, not 27". Those Raleigh Competitions had quite good clearance under fork crown and brake bridge, so I reckon you should be able to fit 35mm tyres provided there's sufficient clearance between the chainstays.

Nick Payne

[Andy Beichler]

Excellent reminder about checking clearance on the Bdop pad holders.  I had to take a little bit of material off the tops of them to clear the tires on my International.  

[David Pertuz]

For me it's around 8mm. My "road bike" is a Vendetta custom that was designed for 700c x 25. I loved the handling, but hated the skinny tires. I converted it to 650b and it transformed the bike for me. I usually run 33mm tires, but it will fit up to 40mm. It's a joy to ride. 

David

Chicago

--

[Andy G]

I had a Soma Stanyan that held 700x32 or 650b x 38mm. That wasn't terribly different in width but was slightly more comfortable. I didn't notice the BB drop, but others might be more concerned with that. I only made the conversion because I wanted to built up 650b wheels and eventually buy a proper 650b frame.

I don't really enjoy 700c over 40mm. It just feels large and I don't care about the angle since I don't do MTB. I do currently have 700x45 on the ebike commuter, but that was a smaller than the 50 it came with and the frame would probably look silly with even narrower. I still have tubes on everything, and the extra weight of large 700cs didn't provide me any advantages.

To view this discussion visit https://groups.google.com/d/msgid/650b/CAD0zwNktEhrK5mWHU%3DfNPujrWrG%2BSW735x6uP_C4aAv39aUtCg%40mail.gmail.com.

[John Dewey]

A few years ago now I added a 650b to the rotation.

These days I find myself inclined to grabbing it first because it just seems to roll ‘faster’. All my tires are Continental 5000 @ 32mm. BTW, I’ve ridden wider but find that 32 is works  best for me. 

This doesn’t make sense to me. The steel frames I have are quite similar, so I don’t think that explains it. 

I guess I’m drawn to the great mystery. 

Jock

To view this discussion visit https://groups.google.com/d/msgid/650b/CAD0zwNktEhrK5mWHU%3DfNPujrWrG%2BSW735x6uP_C4aAv39aUtCg%40mail.gmail.com.

[Josh Zielinski]

To keep it shorter, 38mm has kind of become a cutoff size for me.  If a bike fits 38mm, regardless of wheel diameter, I don't bother converting it.

38mm feels good, gives enough confidence and comfort for lots of off or rough road riding, and has some nice tires available in the size.

As for difference gained?  I wouldn't convert to go from 35 to 38 or 38 to 42.  I would convert to go from 35 to 42 or 32 to 38.  Hope that makes sense.

This rule/threshold can (and has been) broken when parts on hand make sense: got a nicer pair of 650b wheels?  Put them on, convert it.  I've done this 2x, once for a 26" to 650b.  Wheelsets, especially nicer 650b, are a pretty big investment.

Cheers,

Josh Z

Oregon 

To view this discussion visit https://groups.google.com/d/msgid/650b/CA%2BkTrE7Y7p7-tWhHoxpOjtG%2Bxa3WZkywczjddmOdg8sCqiiSvA%40mail.gmail.com.

[fordb...@gmail.com]

Your Competition should be fine with little to no work going to 42mm tires and fit fenders too.

You'll need something like MAFAC RAIDS to stop them. Or the Rene Herse center pulls.

Ford

Ghent, NY

[Gary Helfand]

Can someone please point me to what a  "B drop Pad dropper" is? Googling brings up everything but.

Thanks,

Gary

[David Pertuz]

Someone added an extra 'r' in there a couple of messages ago:

https://bdopcycling.com/product/bdop-offset-brake-pad-holders-set-silver/

David

Chicago

--
You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/650b/6373c088-c1a2-4980-abd0-2d9ef1928e6an%40googlegroups.com.

[Guy Jett]

In addition to the link provided above by d.pertuz, BDop also carries a black version.

Beyond that there are a few alternatives:

*  BlueLug carries similar:  *BL SELECT* offset brake pad

*  Also search Amazon for "c brake extension bike".  You can find many similar to the BDop's and a number of possible alternatives.

GAJett

To view this discussion visit https://groups.google.com/d/msgid/650b/CAD0zwN%3DUg0ABZtaQkCJssX-K7vo%3DO7NEe09EZy0u7PjwGtfYCg%40mail.gmail.com.

[Bernard Duhon]

 in increasing your tire size from 32 to 38 may not be enough to justify the conversion 

being able to also add a fender may make the deal fly

Get Outlook for iOS

---

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Guy Jett <guy4...@gmail.com>
Sent: Tuesday, December 16, 2025 1:09:00 AM
To: David Pertuz <d.pe...@gmail.com>
Cc: Gary Helfand <garyh...@gmail.com>; 650b <65...@googlegroups.com>

Subject: Re: [650B] How much tire width gain to justify 650b conversion?

To view this discussion visit https://groups.google.com/d/msgid/650b/CAMHQv6VTscw5miiSNghSOQDPXW7fQ9sEfvjo0O0rCEfjJ8j2yA%40mail.gmail.com.

[Andy G]

I used something similar on my conversion. Brakes were something like 73mm reach and the 'dropped shoes' were an easy $10 item to get a couple more mm. 

But if a conversion turns into building a new wheelset, long brakes, dropped shoes, different size fenders, all to gain 6-8mm... it may be easier/cheaper to just buy a 650b frame.

To view this discussion visit https://groups.google.com/d/msgid/650b/CAD0zwN%3DUg0ABZtaQkCJssX-K7vo%3DO7NEe09EZy0u7PjwGtfYCg%40mail.gmail.com.

[Gary Helfand]

Thanks for the answers.

[Guy Jett]

Andy G,

You are undoubtedly correct but I love this old frame.  I'm changing the wheels anyway reusing my very early version (1975 or '76) Phil hubs.  They are already out to Phil for a rebuild.  (I also have a very early bottom bracket where the bearings were silver soldered into the assembly.  Phil says it cannot be rebuilt, but it'll still do.)  

Ford, above, mentioned using longer reach brakes such as Mafac "Raid" or the Rene Herse centerpulls. In both cases, and I'll need to recheck, I don't think the R.H. brakes have enough reach and I couldn't find the reach for the Raids.  I did run across some long-reach Dia Comp's on eBay with and 80mm reach, but again, I'll need to double-check.  I do have a 650b front wheel that allows me to measure the reach.

So my decision is not based on the least expensive route but what will satisfy me.  650b if I can make the brakes work without spending and additional $150 to $250, 700c if not.  Right now I'm forecasting between $700 and $1,100 in replacement parts and labor (with most of the labor mine (free).

And my thanks to Andy Beichler and the group for allowing me to hijack this thread AND for  all the helpful input from everyone!

GAJett

To view this discussion visit https://groups.google.com/d/msgid/650b/05aa9e05-2b58-46fd-9669-6f667422c520n%40googlegroups.com.

[Andy Beichler]

Gary, if you really love the frame and want to go with 650b, you can always get a frame builder to add some cantilever posts.  There are examples of Competitions being converted to 650b. Peter Weigle has done a few. 

That being said, if you can get 700Cx38s in there with fenders, it may not be worth it.  

[Ford Bailey]

GA Jett-

I bolted RAIDs onto my 1973 Raleigh Competition. They were OK, but the pads sat at the end of the arms. I have since brazed on centerpull bosses. It does make for a wonderful 650b bike that can handle 42mm tires with fenders.

As Andy points out- cantilevers are a good choice if you're going to modify the frame. The cantilever bosses also provide a perfect perch for a rack, Pete Weigle's being the ultimate in form, function and sophistication. I went with centerpull bosses on mine because it was something I wanted to try, but I'll have to add rack bosses. Attached is a picture of the bike when I first built it up.

Ford

Ghent, NY

You received this message because you are subscribed to a topic in the Google Groups "650b" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/650b/ZWqu8qQnEZc/unsubscribe.
To unsubscribe from this group and all its topics, send an email to 650b+uns...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/650b/CAMHQv6UBJtvfYmbBA0nEp0Pm8qmWHFABp51bBVKESmQY1%3DVNnQ%40mail.gmail.com.

[Andrew Letton]

I have used neither, but MUQZI and ZTTO both make cheap drop pad holders, albeit only in black or red:

https://www.aliexpress.us/item/3256810100632370.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.2.3948mFwNmFwNqO&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40050.354490.0&scm_id=1007.40050.354490.0&scm-url=1007.40050.354490.0&pvid=e3718153-6ba3-4ae6-b0a0-543098e6d315&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:e3718153-6ba3-4ae6-b0a0-543098e6d315,tpp_buckets:668%232846%238107%231934&pdp_ext_f=%7B%22order%22%3A%2215%22%2C%22eval%22%3A%221%22%2C%22sceneId%22%3A%2230050%22%2C%22fromPage%22%3A%22recommend%22%7D&pdp_npi=6%40dis%21USD%2114.38%217.19%21%21%21100.62%2150.31%21%402101e8f317659485945757672e6f5a%2112000051796157449%21rec%21US%21928484858%21XZ%211%210%21n_tag%3A-29919%3Bd%3A1e6a0c4f%3Bm03_new_user%3A-29895&utparam-url=scene%3ApcDetailTopMoreOtherSeller%7Cquery_from%3A%7Cx_object_id%3A1005010286947122%7C_p_origin_prod%3A

and

https://www.aliexpress.us/item/3256806504136710.html?spm=a2g0o.productlist.main.11.3a2dJqMUJqMUON&algo_pvid=8ae1072c-43cf-4b57-9aa7-17bd44cc6ef5&algo_exp_id=8ae1072c-43cf-4b57-9aa7-17bd44cc6ef5-10&pdp_ext_f=%7B%22order%22%3A%229%22%2C%22eval%22%3A%221%22%2C%22fromPage%22%3A%22search%22%7D&pdp_npi=6%40dis%21USD%2110.83%2110.83%21%21%2175.79%2175.79%21%402101d49617659485795567073e78d3%2112000038020837881%21sea%21US%21928484858%21X%211%210%21n_tag%3A-29919%3Bd%3A1e6a0c4f%3Bm03_new_user%3A-29895&curPageLogUid=RlQq2x1cBxn3&utparam-url=scene%3Asearch%7Cquery_from%3A%7Cx_object_id%3A1005006690451462%7C_p_origin_prod%3A

cheers,

Andrew in Sydney

[Brad]

Yes.  The bottom bracket clearance will be roughly the same as going from 700 x 40 to 700 x 23.

584/2=292

292 + 42= 334

622/2 =311

311+23= 334

The increased drop will be 17 .   The width of 8 spokes plus a bit.  (14 gauge spokes are 2 mm)

Another way of thinking this out is "Could this bike be ridden with tubulars without disaster?"

[Brad]

The go to brakes for conversions are Mafac Racers (first thing to try) and then Mafac Raids (Rene Herse or Grand Bois Chouette).   There are also Dia Compe (or Weinmann) 750 brakes if you prefer that flavor (also closer to original spec).

On Sunday, December 14, 2025 at 12:50:09 PM UTC-5 guy4...@gmail.com wrote:

[guy4...@gmail.com]

Thanks for the input Brad.  All this is helpful
 
While tubulars were on '74 Competitions originally I converted mine to 27-inch by 1-1/4" wheels nearly 50 years ago when 700c was not widely known (at least not to me).  So the more appropriate comparison is from the 27's.  Here are my calculations based on yours.

Estimated radii (in mm):
27 x 1-1/4" (630 x 30) (nominal)
630 / 2 = 315
315 + 32 = 347

700c x 38 (622 x 38) (nominal)
622 / 2 = 311
311 + 38 = 349

650b x 38 (35 actual measurement)
584 / 2 = 292
292 + 35 = 327

650b / 42 (nominal)
584 / 2 = 292
292 + 42 = 334

Bottom Bracket drops and ...
     height above level surface for conversion
          (height is a proxy for bottom bracket drop):
27 x 1-1/4" = 10-inches (measured)
700c x 38   = 349 - 347 = 2mm higher or < 1/8" (a wash)
    or about 10 + 0.079 " = <10-1/8" height (nearly same as original),
650b x 35   = 349 - 327 = 22mm lower = -0.866" or ~13/16"
    or about 10 - 13/16 = 9-3/16" estimated new height.
650b x 42  = 349 - 334 = 15mm lower = -0.590" or ~ 5/8"
     or about 10 - 5/8 = 10-3/8" estimated new height.

Current A. Homer Hilsen bottom bracket drop = 9-1/2" measured.

So either 650b brings me closer to my current Hilsen setup and provides me the an extra 13/16" or 5/8" of standover clearance.

Also note both bikes have 170mm crank arms, so there is little difference in cornering angles converting to 650b.

[guy4...@gmail.com]

I've taken a second look at the needed brake reach for a 650b conversion.  The Raleigh Competition currently has the original Weinmann centerpulls, 610 in back and 750 in front.  Fitting a 650b wheel into the bike I find that the 750 is about 3mm too short at the bottom of the adjustment slot.  Looking at the brake reach specifications across many road and mountain bikes these Weinmanns and near identical Dia-Comps seem to represent the maximum reach of most brakes with a very few going to an 80mm reach.  And most of these are quite pricey.

Measuring my frame with a 6550b wheel in place, per St. Sheldon's advice, I see a front reach of 84mm and a rear reach of 81mm.  Looking at the MUQZI and ZTTO type extenders mentioned by Andrew Letton these seem to provide much more extention than I need.  On the other hand theBDop-type pad holders mentioned by Bernard Duhon look very promising, but I'd like to stay with KoolStop shoes.  Or I even revert to the ancient finned Mathauser brake pads I still have lying around!

That takes me back to building "drop bolts" following the examples by St. Sheldon.  I have some hard brass that should work quite well and some moderately thick aluminum plate -- either should work quite well.  If I do that, I'll move the 650 from the back to the front for greater mechanical advantage, and the longer 750 to the rear.

As to a rear rack, I'm already set with an original Jim Blackburn rack that bolts to the brake pivot bolt.  It's old enough that Jim, himself, might have built it.  It's from long before he sold the business.

G.A. Jett

[Ford Bailey]

The RAIDs (or equivalent) should get you there. Most likely without dropped pads. 

Ford

Ghent

You received this message because you are subscribed to a topic in the Google Groups "650b" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/650b/ZWqu8qQnEZc/unsubscribe.
To unsubscribe from this group and all its topics, send an email to 650b+uns...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/650b/b4940a1b-1890-442e-8a68-74cd25dbe476n%40googlegroups.com.

[fordb...@gmail.com]

https://bdopcycling.com/brake-pads-and-holders

Ford

Ghent, NY

[etorg...@yahoo.com]

I tried +and like) the Sheldon drop bolt.  I can now use a brake I have wanted to use for years.  Previously I had some mega long reach BMX brake that was a brake in name only.  Now I have a snappy brake.  

Eli

In all to warm Albuquerque 

[etorg...@yahoo.com]

A quick note on bb heights.  Although not a big change, remember that tire drop will affect this too.  A 15 percent drop (I am often at 20+) means that you lose about 3 additional mm going from 700x 23 to 650b x 42 due to the tire deflection.

.. Eli 

In all too warm Albuquerque