29er to cyclocross -> Geometry issues?

email hidden said:

I'm looking into making a cyclocross bike out of a Redline MonoCog
29. I only want to run it as a single-speed cross bike with
cantilevers. 700c wheels, probably Formula flip-flops spaced out to
135 rear.

Frame:
http://www.redlinebicycles.com/adultbikes/monocog-29er.html

Here's my question - The fork that comes on the 29er is 80mm
suspension adjusted, but what does that relate to axle to headset?
I'm hoping that I can run the Redline carbon cross fork, but I know
there's going to be some strange geometry to handle there.

Fork:
http://www.redlinebicycles.com/adultbikes/carbon-fork.html

The head angle on the 19" is 72deg, but if I get rid of the extra 80mm
of suspension adjusted fork height, I imagine I'm going to get a much
steeper head angle. I haven't tried to get into the math, mainly
because of the unknown axle to headset measurement. With that even be
ridable? I'm looking for a more road-like ride, but I don't need a
80deg head angle. Anyone have any experience here?

What don't you like about the fork that comes on the Monocog?

For a suspension-corrected 29er fork, you're probably looking at
something like 470mm axle to crown. I doubt that the bike would handle
well with a cyclocros fork. Certainly the experience of mountain bikers
going the other way (putting suspension forks on frames not designed for
them) has not been positive. If you really need to replace the fork,
look at rigid 29er mountain bike forks rather than cyclocross forks. I
don't see what you'd gain though -- if you need cantilever studs, you're
going to end up with something a lot like the stock Monocog fork.

Steve Gravrock said:

On 2007-07-09, [email hidden]

Quoted message said:

I'm looking into making a cyclocross bike out of a Redline MonoCog
29. I only want to run it as a single-speed cross bike with
cantilevers. 700c wheels, probably Formula flip-flops spaced out to
135 rear.

Quoted message said:

Frame:
http://www.redlinebicycles.com/adultbikes/monocog-29er.html

Quoted message said:

Here's my question - The fork that comes on the 29er is 80mm
suspension adjusted, but what does that relate to axle to headset?
I'm hoping that I can run the Redline carbon cross fork, but I know
there's going to be some strange geometry to handle there.

Quoted message said:

Fork:
http://www.redlinebicycles.com/adultbikes/carbon-fork.html

Quoted message said:

The head angle on the 19" is 72deg, but if I get rid of the extra 80mm
of suspension adjusted fork height, I imagine I'm going to get a much
steeper head angle. I haven't tried to get into the math, mainly
because of the unknown axle to headset measurement. With that even be
ridable? I'm looking for a more road-like ride, but I don't need a
80deg head angle. Anyone have any experience here?

What don't you like about the fork that comes on the Monocog?

For a suspension-corrected 29er fork, you're probably looking at
something like 470mm axle to crown. I doubt that the bike would handle
well with a cyclocros fork. Certainly the experience of mountain bikers
going the other way (putting suspension forks on frames not designed for
them) has not been positive. If you really need to replace the fork,
look at rigid 29er mountain bike forks rather than cyclocross forks. I
don't see what you'd gain though -- if you need cantilever studs, you're
going to end up with something a lot like the stock Monocog fork.- Hide quoted text -

- Show quoted text -

Redline Carbon fork is 395mm (Crown to Axle). All of the other cross
forks I've found are 390-405

I'll have to do the math to see what the head angle is with 470. The
reason I'm hoping to go with a more traditional road fork is that my
riding position is much lower than mtn. My saddle to bar drop is ~5"
and with a high-rise fork like the Monocog, I imagine I'd have a have
a hard time getting that fit.

I may end up going with a custom frame, but at the price of the
Redline Monocog 29er, it made for a compelling option.

Quoted message said:

Steve Gravrock said:

On 2007-07-09, [email hidden]

Quoted message said:

Quoted message said:

I'm looking into making a cyclocross bike out of a Redline MonoCog
29. I only want to run it as a single-speed cross bike with
cantilevers. 700c wheels, probably Formula flip-flops spaced out to
135 rear.

Quoted message said:

Quoted message said:

Frame:
http://www.redlinebicycles.com/adultbikes/monocog-29er.html

Quoted message said:

Quoted message said:

Here's my question - The fork that comes on the 29er is 80mm
suspension adjusted, but what does that relate to axle to headset?
I'm hoping that I can run the Redline carbon cross fork, but I know
there's going to be some strange geometry to handle there.

Quoted message said:

Quoted message said:

Fork:
http://www.redlinebicycles.com/adultbikes/carbon-fork.html

Quoted message said:

Quoted message said:

The head angle on the 19" is 72deg, but if I get rid of the extra 80mm
of suspension adjusted fork height, I imagine I'm going to get a much
steeper head angle. I haven't tried to get into the math, mainly
because of the unknown axle to headset measurement. With that even be
ridable? I'm looking for a more road-like ride, but I don't need a
80deg head angle. Anyone have any experience here?

Quoted message said:

What don't you like about the fork that comes on the Monocog?

Quoted message said:

For a suspension-corrected 29er fork, you're probably looking at
something like 470mm axle to crown. I doubt that the bike would handle
well with a cyclocros fork. Certainly the experience of mountain bikers
going the other way (putting suspension forks on frames not designed for
them) has not been positive. If you really need to replace the fork,
look at rigid 29er mountain bike forks rather than cyclocross forks. I
don't see what you'd gain though -- if you need cantilever studs, you're
going to end up with something a lot like the stock Monocog fork.- Hide quoted text -

Quoted message said:

- Show quoted text -

Redline Carbon fork is 395mm (Crown to Axle). All of the other cross
forks I've found are 390-405

I'll have to do the math to see what the head angle is with 470. The
reason I'm hoping to go with a more traditional road fork is that my
riding position is much lower than mtn. My saddle to bar drop is ~5"
and with a high-rise fork like the Monocog, I imagine I'd have a have
a hard time getting that fit.

I may end up going with a custom frame, but at the price of the
Redline Monocog 29er, it made for a compelling option.- Hide quoted text -

- Show quoted text -

I did the visio and it gave me 76degrees (!). That could be a little
harsher than I'm ready for. Maybe I can find a HS with some serious
stack height.

Quoted message said:

I did the visio and it gave me 76degrees (!). That could be a little
harsher than I'm ready for. Maybe I can find a HS with some serious
stack height.

You also get a ridiculous low bottombracket
--
/Marten

info(apestaartje)m-gineering(punt)nl

In article <[email hidden]>,

Quoted message said:

On Jul 9, 10:11 am, [email hidden] wrote:

I did the visio and it gave me 76degrees (!). That could be a little
harsher than I'm ready for. Maybe I can find a HS with some serious
stack height.

I'd also guess you're going to have clearance problems, have you
checked that the wheel will clear the downtube? A surly
X-check seems like a much better fit towards what you want.

_ Booker C. Bense

Quoted message said:

I'm looking into making a cyclocross bike out of a Redline MonoCog
29. I only want to run it as a single-speed cross bike with
cantilevers. 700c wheels, probably Formula flip-flops spaced out to
135 rear.

Aren't mountain bike BB shells wider than road bb shells? If so, this
might pose problems. My Formula hubs have a 42 BB chainline. That
might be tough to match with a wide BB shell. I'm not sure though.

\\paul

Booker C. Bense bbense+rec.bicycles.tech.Jul. said:

In article <[email hidden]>,

Quoted message said:

On Jul 9, 10:11 am, [email hidden] wrote:

Quoted message said:

I did the visio and it gave me 76degrees (!). That could be a little
harsher than I'm ready for. Maybe I can find a HS with some serious
stack height.

I'd also guess you're going to have clearance problems, have you
checked that the wheel will clear the downtube? A surly
X-check seems like a much better fit towards what you want.

_ Booker C. Bense

yeah - I considered that, but I'd rather not have all the bosses for
cabling. Custom may be my best option. Or a track frame with LOTs of
clearance and just tack on some cantilever bosses.

Quoted message said:

Redline Carbon fork is 395mm (Crown to Axle). All of the other cross
forks I've found are 390-405

I'll have to do the math to see what the head angle is with 470. The
reason I'm hoping to go with a more traditional road fork is that my
riding position is much lower than mtn. My saddle to bar drop is ~5"
and with a high-rise fork like the Monocog, I imagine I'd have a have
a hard time getting that fit.

I may end up going with a custom frame, but at the price of the
Redline Monocog 29er, it made for a compelling option.

Dropping 75mm off the fork axle-crown height??? I think
it would ride like [censored]. If you need to get the bars
down, a much better idea would be to use a somewhat
down-angled stem. However, a 5" saddle to bar drop
sounds very large for cyclocross (unless you are a really
big person, but it's still unusual). Many people have
the bars 2" or so higher on their cross bike than their
road bike. You don't need to spend a lot of time in
a deep aero drop and it helps with handling and balance
on rough stuff and descents.

Ben

In article <[email hidden]>,

Quoted message said:

On Jul 9, 1:40 pm, Booker C. Bense <bbense+rec.bicycles.tech.Jul.

Quoted message said:

I'd also guess you're going to have clearance problems, have you
checked that the wheel will clear the downtube? A surly
X-check seems like a much better fit towards what you want.

_ Booker C. Bense

yeah - I considered that, but I'd rather not have all the bosses for
cabling.

I run mine single speed and I've not noticed them.

Quoted message said:

Custom may be my best option. Or a track frame with LOTs of
clearance and just tack on some cantilever bosses.

It's your money, bosses come off easier than they go on.

Is there some reason you don't want to buy a Bianchi San Jose?

_ Booker C. Bense

Booker C. Bense bbense+rec.bicycles.tech.Jul. said:

Is there some reason you don't want to buy a Bianchi San Jose?

_ Booker C. Bense

There's a little more to the story.

Single speed cross will likely be it's primary use, but it is just one
incarnation for this bike:

1. Going to have it modified with S&S couplers to fit in a Ritchey bag
2. Setup an extra wheel with a Nexus 8sp rear to get gearing while on
vacation (road riding, not cross)
3. Fixed gear riding (flip/flop wheel) for fall training
4. Big If ~ Removeable canti bosses and race it on the track (29er not
so good there)

The reason I can't go with the San Jose is that because in a size 60,
it won't fit in the bag. I need to get a compact geometry frame which
is where the 29er idea came up. I may end up going with a custom
frame anyway, because to retrofit a $200 redline frame with a $400
coupler job adds up quick. Then again, getting a custom bike with
S&S, even in steel is $$$.

I've scoured the web for a 700c, compact rear dropout frame with
little luck. The On One Pompino is the closest I've found and it's
not quite right.