Ride Height And Now Frame Geometry

Posted: Mon Mar 18, 2019 10:21 am

Out of curiosity, can someone throw a tape measure on your bike (preferably a stock suspension bike) and tell me the length from the center of the swingarm pivot to the ground with the bike straight up and no one sitting on it? I'm trying to figure out some suspension stuff and I just want to make sure I'm not out in left field or that when I get done setting the rake and trail I'm not going to be so low I scrape on everything when I ride it or something silly like that.
Thanks guys.

Also, whats the stock wheel base axle to axle?

Posted: Mon Mar 18, 2019 1:10 pm

Hi Nat
this is my reference cad model ... well it comes from a 3d model found on GrabCad (Thanks Fabnorman)
I just put it in 2d and added wheels, shocks and forks ... I drafted some for different ride height set ups.
The pivot should be 411 mm from the ground

Wheelbase should be 1520 mm
Ivan

Posted: Mon Mar 18, 2019 6:02 pm

That's perfect Ivan! Thanks you!

Posted: Tue Mar 19, 2019 1:16 am

This is what I have so far. I appreciate any input.
Tires are 180/55/17 rear and 120/70/17 Front
26 degree steering head
CBR F4I front forks (I can't say that number is 100% accurate but I found that online somewhere. I haven't put my forks back together yet.)
Right now I have the forks even with the top of the top triple clamp.
Swingarm is longer I know...

What else do you guys see that I need to address???

CB1100F Joined: Feb 17, 2009 Posts: 2111 Location: Oz

All I'll add is that all measurements should be taken with the bike jacked up so that both tyres are just kissing the (level) ground. That should be your reference.

Posted: Tue Mar 19, 2019 9:19 am

if you get the weight on wheels - you could add how the cog in the horizontal is shifting with your changes - given your kinda fixed on the front rake and offset mod. - you could use this to determine rear arm length for a target fwd / rear weight bias

Posted: Tue Mar 19, 2019 2:44 pm

nlovie wrote:

if you get the weight on wheels - you could add how the cog in the horizontal is shifting with your changes - given your kinda fixed on the front rake and offset mod. - you could use this to determine rear arm length for a target fwd / rear weight bias

I think Brent's bias is 52/48, he'll correct me if I misquoted. I have a feeling he was going to extend the rear swingarm even a bit more to get more weight over the front and try keep the front from wheeling so easy.

On my last build, I used 17 inch tires front and rear (180), with Oz Racing Gass wheels. The swingarm was 20 inches (508mm) from pivot to rear axle. The lower engine case was set in the frame first and all was adjusted such that the case surface was set level. The swingarm droop was set at 12.5 degrees with both wheels "just" touching the ground. Front triple clamp offset of 40mm with 210 mm fork spacing (43mm forks). Front OHLIN forks at 800mm total length, ended up setting flush to the top surface of the triple clamp to maintain the level crankcase and rear swingarm droop at 12.5 degrees. I ended up with a final assembled weight bias (riderless and I am sure it only had a "bit" of fuel in it) of 51/49 front to rear using two individual scales (225lbs front and 218lbs rear, 443lbs total weight). The frame was stock 900F geometry.

Nathan you should be pretty happy with that geometry and with 95mm of trail.

Posted: Tue Mar 19, 2019 5:11 pm

Darren
A whole lot of facts and numbers ...
what about shock length? Would you mind me drafting a drawing with your setup?
Ivan

Posted: Tue Mar 19, 2019 5:31 pm

ivan_the_terrible wrote:

Darren
A whole lot of facts and numbers ...
what about shock length? Would you mind me drafting a drawing with your setup?
Ivan

365mm eye to eye ..... mounted to upper OEM mount location. The lower mount location adjusted to achieve the 12.5 degrees droop. This was with a GSXR600 SRAD swingarm which is taller than the OEM swingarms as well.

Posted: Tue Mar 19, 2019 9:49 pm

DonR wrote:

All I'll add is that all measurements should be taken with the bike jacked up so that both tyres are just kissing the (level) ground. That should be your reference.

I disagree due to the fact that there are endless variables with it. There are none when the level case method is used as its the one common denominator that can be replicated in any build or building analyses situation.

Captain

CB1100F Joined: Feb 17, 2009 Posts: 2111 Location: Oz

Captain wrote:

DonR wrote:

All I'll add is that all measurements should be taken with the bike jacked up so that both tyres are just kissing the (level) ground. That should be your reference.

I disagree due to the fact that there are endless variables with it. There are none when the level case method is used as its the one common denominator that can be replicated in any build or building analyses situation.

Captain

That's OK. You use your method and I'll keep using the method developed by the established chassis design professionals.

https://motochassis.com/DocumentFiles/SetupManual.pdf refer pages 9, 57 and 58.

Posted: Wed Mar 20, 2019 5:23 pm

petrat wrote:

nlovie wrote:

if you get the weight on wheels - you could add how the cog in the horizontal is shifting with your changes - given your kinda fixed on the front rake and offset mod. - you could use this to determine rear arm length for a target fwd / rear weight bias

I think Brent's bias is 52/48, he'll correct me if I misquoted. I have a feeling he was going to extend the rear swingarm even a bit more to get more weight over the front and try keep the front from wheeling so easy.

On my last build, I used 17 inch tires front and rear (180), with Oz Racing Gass wheels. The swingarm was 20 inches (508mm) from pivot to rear axle. The lower engine case was set in the frame first and all was adjusted such that the case surface was set level. The swingarm droop was set at 12.5 degrees with both wheels "just" touching the ground. Front triple clamp offset of 40mm with 210 mm fork spacing (43mm forks). Front OHLIN forks at 800mm total length, ended up setting flush to the top surface of the triple clamp to maintain the level crankcase and rear swingarm droop at 12.5 degrees. I ended up with a final assembled weight bias (riderless and I am sure it only had a "bit" of fuel in it) of 51/49 front to rear using two individual scales (225lbs front and 218lbs rear, 443lbs total weight). The frame was stock 900F geometry.

Nathan you should be pretty happy with that geometry and with 95mm of trail.

Darren,
this should be your setup, including the 40mm upper tree, translated into a drawing ... sorry for the size
Of course it may cbe not reflect the reality , but shouldn't be too far ?
Ivan

Posted: Wed Mar 20, 2019 7:34 pm

ivan_the_terrible wrote:

petrat wrote:

nlovie wrote:

if you get the weight on wheels - you could add how the cog in the horizontal is shifting with your changes - given your kinda fixed on the front rake and offset mod. - you could use this to determine rear arm length for a target fwd / rear weight bias

I think Brent's bias is 52/48, he'll correct me if I misquoted. I have a feeling he was going to extend the rear swingarm even a bit more to get more weight over the front and try keep the front from wheeling so easy.

On my last build, I used 17 inch tires front and rear (180), with Oz Racing Gass wheels. The swingarm was 20 inches (508mm) from pivot to rear axle. The lower engine case was set in the frame first and all was adjusted such that the case surface was set level. The swingarm droop was set at 12.5 degrees with both wheels "just" touching the ground. Front triple clamp offset of 40mm with 210 mm fork spacing (43mm forks). Front OHLIN forks at 800mm total length, ended up setting flush to the top surface of the triple clamp to maintain the level crankcase and rear swingarm droop at 12.5 degrees. I ended up with a final assembled weight bias (riderless and I am sure it only had a "bit" of fuel in it) of 51/49 front to rear using two individual scales (225lbs front and 218lbs rear, 443lbs total weight). The frame was stock 900F geometry.

Nathan you should be pretty happy with that geometry and with 95mm of trail.

Darren,
this should be your setup, including the 40mm upper tree, translated into a drawing ... sorry for the size
Of course it may be not refleNei paesi anglosassoni, la festa del papà ricorre a Giugno e non ha alcun legame con alcun santo; in Olanda, viene festeggiata il 18 Giugno. Secondo questa stessa tradizione, riconosciuta anche dai Paesi Bassi,ct the reality , but shouldn't be too far ?
Ivan

Ivan, that is awesome thank you.

Posted: Wed Mar 20, 2019 10:08 pm

Ops Darren please remove the part in Italian from my quote...
Nothing nasty but an unintentional cut and paste !

Posted: Thu Mar 21, 2019 12:12 pm

Well Happy Fathers Day Ivan.

Posted: Thu Mar 21, 2019 2:16 pm

Ivan,

What is the rolling radius for Darren’s 120/70 front wheel? Does this figure change depending on the manufacturers tire that is selected?

Thanks,

Todd

Posted: Thu Mar 21, 2019 3:06 pm

Ha djhurayt
yes I did a research on Fathers Day in Holland .
My son lives there ...
Ciao
Ivan