650c rear wheel

Jon_H said:

The bike I own was originally for 271/4 inch wheels I have changed these for
700c wheels is their any problems with running a 650c rear wheel as a fixed
wheel (no rear brake) other than the change in geometry of the bike while
keeping the front at 700c or would it be wise to try and source a new pair
of forks and fit a 650c on the front.

cheers
Jon_H

Change the gearing also but it is possible.

Jon_H said:

The bike I own was originally for 271/4 inch wheels I have changed these for
700c wheels is their any problems with running a 650c rear wheel as a fixed
wheel (no rear brake) other than the change in geometry of the bike while
keeping the front at 700c or would it be wise to try and source a new pair
of forks and fit a 650c on the front.

cheers
Jon_H

Its just geometry, but that's everything.

Besides handling changes (what I guess you meant)
the 650 rear will lower the BB and cranks about 15mm
increasing the chance of a pedal strike as you pedal
through a turn (no choice fixed). 650c in the front
drops another 10mm.

For that est. I used Sheldon Brown's gear calculator:
http://www.sheldonbrown.com/gears/
w/ 52/13, MPH to est the fractional change in tire radius.
BB is about 40mm/100mm forward of the rear axle, so
about 60/100 of the rear axle drop is seen at the BB.

Shorter cranks (155mm instead of 170) could recover
some ground clearance if you're willing, but two 650c
seems out of reach. Remember that 27 to 700c lost
a few mm clearance anyway. Best to stick to 700c.

Ed

"Ed" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Jon_H said:

The bike I own was originally for 271/4 inch wheels I have changed these

for

Quoted message said:

Quoted message said:

700c wheels is their any problems with running a 650c rear wheel as a

fixed

Quoted message said:

Quoted message said:

wheel (no rear brake) other than the change in geometry of the bike

while

Quoted message said:

Quoted message said:

keeping the front at 700c or would it be wise to try and source a new

pair

Quoted message said:

Quoted message said:

of forks and fit a 650c on the front.

cheers
Jon_H

Its just geometry, but that's everything.

Besides handling changes (what I guess you meant)
the 650 rear will lower the BB and cranks about 15mm
increasing the chance of a pedal strike as you pedal
through a turn (no choice fixed). 650c in the front
drops another 10mm.

For that est. I used Sheldon Brown's gear calculator:
http://www.sheldonbrown.com/gears/
w/ 52/13, MPH to est the fractional change in tire radius.
BB is about 40mm/100mm forward of the rear axle, so
about 60/100 of the rear axle drop is seen at the BB.

Shorter cranks (155mm instead of 170) could recover
some ground clearance if you're willing, but two 650c
seems out of reach. Remember that 27 to 700c lost
a few mm clearance anyway. Best to stick to 700c.

Ed

I think I'll give it a miss as it has 170 cranks at the moment and changing
these to 155's would be a bit strange and wouldn't have the desired effect.
Damn there goes that cheap 650 disc wheel

cheers
Jon_H

Don't let these guys scare you.

OK, so it lowers your bottom bracket slightly. So what?

Does your frame have a high bottom bracket right now, or a low one?
Your advisors don't know this, yet they are advising you.

How ever much the smaller wheel lowers your rear hub, your BB will only
lower about half that amount because it is about halway between the 2
wheels.

Riding a fixie can be an amazing experience (I am reminded of this
almost evry day) and I would hate to see you miss out on it.

Lewis.

*******

Jon_H said:

The bike I own was originally for 271/4 inch wheels I have changed these for
700c wheels is their any problems with running a 650c rear wheel as a fixed
wheel (no rear brake) other than the change in geometry of the bike while
keeping the front at 700c or would it be wise to try and source a new pair
of forks and fit a 650c on the front.

there may be handling and pedal clearance issues but if I
owned such a wheel I'd install it and go for a ride looking
at those two things. If acceptable, leave it in.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

"A Muzi" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Jon_H said:

The bike I own was originally for 271/4 inch wheels I have changed these

for

Quoted message said:

Quoted message said:

700c wheels is their any problems with running a 650c rear wheel as a

fixed

Quoted message said:

Quoted message said:

wheel (no rear brake) other than the change in geometry of the bike

while

Quoted message said:

Quoted message said:

keeping the front at 700c or would it be wise to try and source a new

pair

Quoted message said:

Quoted message said:

of forks and fit a 650c on the front.

there may be handling and pedal clearance issues but if I
owned such a wheel I'd install it and go for a ride looking
at those two things. If acceptable, leave it in.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

too late, the wheel has gone I'll stick with my 700c wheels. It was a 650c
carbon disc on ebay but it's gone and I chickened out as I would only have
to sell it again if it didn't fit.

cheers
Jon_H

Quoted message said:

Don't let these guys scare you.

OK, so it lowers your bottom bracket slightly. So what?

Does your frame have a high bottom bracket right now, or a low one?
Your advisors don't know this, yet they are advising you.

How ever much the smaller wheel lowers your rear hub, your BB will only
lower about half that amount because it is about halway between the 2
wheels.

Riding a fixie can be an amazing experience (I am reminded of this
almost evry day) and I would hate to see you miss out on it.

Lewis.

Lewis: Riding a fixie *can* be an amazing experience! Many new ways to screw
up besides the inevitable ooops-forgot-I-can't-coast and get launched over
the handlebars. Specifically, cornering has to be done quite differently so
the cranks don't scrape (since you cannot coast and keep the relevant pedal
"up"😉. This is something that's no doubt second-nature to you by now, but
even with a "high" bottom bracket (11 inches; rarely would you see higher
than that) this can still happen if you're not careful. Dropping that
distance by changing the front wheel from 630mm to 571mm could make the
experience far more thrilling than intended.

Creating "fixies" is all the rage, and I'm all for it. But we do get quite a
few customers coming in scraped up and bruised.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

Good post, Mike.

I guess I've been lucky as I have never had a wreck on a fixie and,
although I don't ride fixed all the time, its been well over 50 years
since I put my first one together.

Kind regards.

Lewis.

*********

Quoted message said:

I guess I've been lucky as I have never had a wreck on a fixie and,
although I don't ride fixed all the time, its been well over 50 years
since I put my first one together.

Well then you just haven't had as much fun as many! :>😉

I remember a club ride back in the 70s, and this very experienced track guy,
Ken Spears I believe, was with us up on Skyline Blvd (2500ft) in a heavy
rain. No brakes. On the descents, he was literally grabbing onto some of us
to help slow down. Can't experience that type of ride on a bike with gears &
brakes!

Quoted message said:

Kind regards.

Lewis.

--
--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA
<[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Good post, Mike.

I guess I've been lucky as I have never had a wreck on a fixie and,
although I don't ride fixed all the time, its been well over 50 years
since I put my first one together.

Kind regards.

Lewis.

*********