Converting from 700c to 650b
#1
Converting from 700c to 650b
So I just got a aero frame road bike in the smallest size avail and the top tube still touching my privates but at least I can stand over it but I would like a like some clearance so I'm gonna put on 650b tires to drop the frame a little bit. I just got some mavic wheels in the mail and got some 27.5 x 1.5 tires so I'm hoping it'll fit cause I'm just playing it by ear. The main concern I'm having is the brakes cause the ones I have on there now are very short arm ones so I'm wondering what size do I need to reach if I can even do that cause these wheels I got just say disk brake wheels and I donno if I can use pads on those rims but they say they are s6000 double wall aluminum so shouldn't that be strong enough? I might be able to put on disk brakes and I already ordered all the disk brake hardware for it in case I wanna do that but the thing is the bike doesn't have the built in holes to mount the stuff so I ordered disk brake adapters that clamp onto the frame and spindle thingy to provide the two holes but I wasn't sure about that cause I was reading where people have said it might bend the frame cause the frame isn't ment to support that force or something so I was thinking should I just put on long arm brakes to do a rim brake even if the rim doesn't specifically say it can do that cause it's not like I'm going to be doing some serious speed and hard stops anyways and I would think if braking is done on both wheels it's not like one side is getting all the force anyways and I feel same thing can be said about the disk brake adapters too. So what should I do? I'm so confused.
#2
Senior Member


Joined: Apr 2007
Posts: 4,129
Likes: 56
From: Munising, Michigan, USA
Bikes: Priority 600, Priority Continuum, Devinci Dexter
What you are talking about doing does not seem safe. I would not use adapters to force disk brake calipers onto a frame and fork not designed for them, nor would I run rim brakes on a wheelset without a braking track.
Last edited by JonathanGennick; 08-13-18 at 08:44 PM.
#4
Senior Member

Joined: Aug 2011
Posts: 22,676
Likes: 2,643
From: CID
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
So I just got a aero frame road bike in the smallest size avail and the top tube still touching my privates but at least I can stand over it but I would like a like some clearance so I'm gonna put on 650b tires to drop the frame a little bit. I just got some mavic wheels in the mail and got some 27.5 x 1.5 tires so I'm hoping it'll fit cause I'm just playing it by ear. The main concern I'm having is the brakes cause the ones I have on there now are very short arm ones so I'm wondering what size do I need to reach if I can even do that cause these wheels I got just say disk brake wheels and I donno if I can use pads on those rims but they say they are s6000 double wall aluminum so shouldn't that be strong enough? I might be able to put on disk brakes and I already ordered all the disk brake hardware for it in case I wanna do that but the thing is the bike doesn't have the built in holes to mount the stuff so I ordered disk brake adapters that clamp onto the frame and spindle thingy to provide the two holes but I wasn't sure about that cause I was reading where people have said it might bend the frame cause the frame isn't ment to support that force or something so I was thinking should I just put on long arm brakes to do a rim brake even if the rim doesn't specifically say it can do that cause it's not like I'm going to be doing some serious speed and hard stops anyways and I would think if braking is done on both wheels it's not like one side is getting all the force anyways and I feel same thing can be said about the disk brake adapters too. So what should I do? I'm so confused.
#6
Senior Member
Joined: Oct 2006
Posts: 4,770
Likes: 369
From: Orange County, CA
People convert to 650B all the time, especially to run Road Plus tires like WTB Horizons and WTB Byways. However, you will need a bit of tyre clearance to run anything larger than 1.2" which is not very likely on an aero bike.
#7
Senior Member




Joined: Dec 2004
Posts: 15,427
Likes: 8,344
From: Seattle area
Bikes: Bikes??? Thought this was social media?!?
So I just got a aero frame road bike in the smallest size avail and the top tube still touching my privates but at least I can stand over it but I would like a like some clearance so I'm gonna put on 650b tires to drop the frame a little bit. I just got some mavic wheels in the mail and got some 27.5 x 1.5 tires so I'm hoping it'll fit cause I'm just playing it by ear. The main concern I'm having......
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Vintage, modern, e-road. It is a big cycling universe.
Vintage, modern, e-road. It is a big cycling universe.
#8
rebmeM roineS

Joined: Jan 2006
Posts: 16,231
Likes: 366
From: Metro Indy, IN
Bikes: Bacchetta Giro A20, RANS V-Rex, RANS Screamer
can you post a pic of the wheel sidewall? Now that you have 10 posts.
I'm using a double pivot caliper rim brake on a rear wheel with a disc hub and non-machined sidewalls. Works fine. But, if your rims' sidewalls do not have flat surfaces suitable for braking, you may be out of luck on rim braking with your new wheels.
Disk brake adapters might do the job for you but that's not a sure thing.
I'm using a double pivot caliper rim brake on a rear wheel with a disc hub and non-machined sidewalls. Works fine. But, if your rims' sidewalls do not have flat surfaces suitable for braking, you may be out of luck on rim braking with your new wheels.
Disk brake adapters might do the job for you but that's not a sure thing.
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Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Last edited by JanMM; 08-15-18 at 11:57 AM.
#9
Senior Member

Joined: May 2014
Posts: 2,547
Likes: 660
Bikes: yes
#11
Buuuuuuuuuuuuut I'm having one issue. So I went to put the rims on the bike and both rims fit but this tire I got which you see in the pics it's 27.5 x 1.5 and rubs the dies of the folk by a hair so I'll need to find a thinner tire so I need to know what kind AND so I put the tire on the rear wheel to see how it fits there but it's totally to far off center so the tire is really rubbing against the one side witch a big gap on the other side from the frame. So I reckon it has something to do with the axle thingy so I been mucking with it and I see one side were the poky turny thingy goes has a weird screwy thingy and the other side has a washer and a nut so what I did was I took out the washer from the other side and put it on the opposite side where it was to close to the frame so I'm thinking maybe that will center it better. I'm so confused.
#14
Senior Member
Joined: Oct 2006
Posts: 4,770
Likes: 369
From: Orange County, CA
Go to a bike shop and have them take a look at it. My guess is the wheel is too big for your frame as it is probably 142x12mm thru axle or 135mm QR while your frame spacing is 130mm. A 1.5" tyre is 38mm which is too big for most road frames. And you will need to install disc brakes and rotors to use that wheel as it is not designed for rim brakes.
What bike are you installing it on?
What bike are you installing it on?
#16
Senior Member
Joined: Oct 2006
Posts: 4,770
Likes: 369
From: Orange County, CA
No idea what bike that is but it doesn't look like a typical bike designed for 650B, disc brakes, or wide tyres. I would recommend returning the bike and the Mavic wheelset and buying a bike that fits. Something like this might be a good start:
https://www.bikenashbar.com/cycling/...try-drop-yb-sd
But your best bet is to go to a shop and get fitted
https://www.bikenashbar.com/cycling/...try-drop-yb-sd
But your best bet is to go to a shop and get fitted
#17
I ordered it from china! Im not sending it back. I orderes the wheels from Taiwan! Not happening. It fits ok but i just wanted the frame a bit lower.m so just trying some stuff. I already tried the new wheels on it and they fit fine the only issue is that particular tire being 1.5 is just a hair to fat for the front forks it will spin but theres a slight rub so i think i can find a slighty narrower one that will work and when i put it on the rear it fits and looks like itll be good there except for the wheel itself being not centered so imma try to adjust the axle to make the wheel move the the right a few mm
#18
Senior Member
Joined: Oct 2006
Posts: 4,770
Likes: 369
From: Orange County, CA
Those Mavic Crossride wheels are not designed for rim brakes. I doubt your current brakes can even reach the sidewall of the 650B rim. It is NOT SAFE to ride your bike with those wheels, especially if they don't even fit in the first place. Good luck.
#22
Senior Member
Joined: Jul 2018
Posts: 239
Likes: 1
From: Iowa
Bikes: Fuji Gran Fondo 2.1 and Scott Sportster P45













