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Not to be confused with the time-trial and women's-specific 650C wheel, the 650B wheel is all about comfort, versatility, and speed over varied terrain. The key to this is all in the tires. A 650B rim with a 38mm tire inflated to 45psi can deliver an astonishingly comfortable ride over rough roads and loose surface materials. And yet, it is surprisingly fast as compared to a similar 700C configuration. This 650x38B setup is about the same diameter as a 700C wheel with a 19mm tire, so although there's a large tire on the 650B rim, the extra weight is located closer to the axle where it is easier to spin-up. And the 650x38B setup rolls better over uneven surfaces than a smaller 26inch road bike setup. The 650B is a nearly perfect, mid-sized wheel option.
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650B Wheels and 26 inch Forks |
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Written by Joel D
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Tuesday, 14 October 2008 |
650B Wheels in 26" Suspension Forks - Things To Consider
Now that the 650B mountain bike wheel has gained some popularity and press, more people are calling us to get a set of wheels to put in their 26 inch mountain bike. If you have already done some studying, you'll already know that a 650B tire doesn't always fit in 26 inch suspension fork - here are things to keep in mind when considering a wheel upsize...
 The problem with going to a bigger tire/wheel size on a standard 26" suspension fork is there can be clearance issues with not only the fork brace but with the fork crown itself. The tire clearance under the fork brace is easy to check by just putting the wheel fully in the fork dropouts. The important thing to remember is that when a suspension fork is fully compressed, the fork crown can actually be lower than the fork brace. That could cause a potentially dangerous situation if the crown dives into the front tire.
To test it you are best off removing the air or coil from the fork and compressing it all of the way. There is currently a thread on MTBR covering this subject that may help as a reference (link at bottom), but always keep in mind that there are sometimes different versions of the same thing when it comes to forks. For example, the Fox Float R that came on your complete new bike (OEM) may be slightly different in specification to one sold aftermarket (again, that is just an example, those could well be exactly the same).
In the images to the right a Panaracer Neo-Moto is set up on a Velocity Synergy rim, it cleared a fully compressed 08 Fox Float 32, but the crown on an 07 Rock Shox SID pushed into the tire. There is no magic number when deciding clearance - but just for reference, the Fox Float fork I tested had an approximate measurement of 350mm from the hub axle to the bottom of the crown when fully compressed leaving a few mm of clearance over the tire.
While some would say that you hardly - if ever - see that last bit of travel, I would argue that if you are in a situation that you are bottoming out the fork the last thing you would want to happen is have the tire jam against the crown. The important thing is to try it out when you get the wheel so you know what to expect when you launch off that little boulder you always have to hit on your favorite trail. Don't forget, this situation only applies to 26" suspension forks, 29er and the few 650b forks available won't have the crown interference issue. |  | | So, How Fast Can You Jump Over Your Handlebar? |
 | | Fork With Clearance |
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See the Related MTBR Thread Here (this will open MTBR.com in a new window)
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; "So, How Fast Can You Jump Over Your Handlebar?")
; "Fork With Clearance")
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