FRANKENHONDA II the 1982 DOHC CB 750F2 Build

LightsOut said:
When you say not rideable, do you mean because the forward lean decreases rake angle and thereby trail? To some extent that would be countered by the smaller offset, right?

What is the offset in the GSXR triples? I believe stock is 45mm?


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Yes and no. The rake is going to be shit most likely. No offset on the world is going to fix that. It will be extremely quick.
 
My knowledge about this is mostly theoretical, but from what I understand rake angle in itself doesn't affect handling that much? What affects handling is primarily the trail number (which is of course a product of rake angle). In the "Tony Foale test" (https://tonyfoale.com/Articles/RakeEx/RakeEx.htm) they experimented with even using even 0 degree rake angle and found it handled pretty normally as long as the trail was kept the same.

..just saying that if the decreased rake angle results in less trail (and thereby twitchy/dangerous handling), then a smaller offset in the triple would pull the trail in the opposite direction. Could be like jag767 says it's way too small difference to compensate for the result of the decreased angle though.

Measuring rake angle with the current setup sounds like it'd be a good idea to put numbers on the change? (good luck getting the wife to do that ;) )

Does the forward lean have other implications than rake/trail? Would weight distribution change and affect handling?
 
LightsOut said:
My knowledge about this is mostly theoretical, but from what I understand rake angle in itself doesn't affect handling that much? What affects handling is primarily the trail number (which is of course a product of rake angle). In the "Tony Foale test" (https://tonyfoale.com/Articles/RakeEx/RakeEx.htm) they experimented with even using even 0 degree rake angle and found it handled pretty normally as long as the trail was kept the same.

..just saying that if the decreased rake angle results in less trail (and thereby twitchy/dangerous handling), then a smaller offset in the triple would pull the trail in the opposite direction. Could be like jag767 says it's way too small difference to compensate for the result of the decreased angle though.

Measuring rake angle with the current setup sounds like it'd be a good idea to put numbers on the change? (good luck getting the wife to do that ;) )

Does the forward lean have other implications than rake/trail? Would weight distribution change and affect handling?

He is using the 17 up front, the offset is fine for that wheel. He can add rake to the triple, but that will only make the bike lower, which is already an issue
 
Not sure I understand what the triple tree offset has to do with wheel size?

Rake angle, offset, fork length and wheel size all affect trail of course, but given a 17" wheel, different offset would give different trail.

Not suggesting he goes chopper with raked triples :)


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LightsOut said:
Not sure I understand what the triple tree offset has to do with wheel size?

Rake angle, offset, fork length and wheel size all affect trail of course, but given a 17" wheel, different offset would give different trail.

Not suggesting he goes chopper with raked triples :)


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Maybe im wrng but isnt the offset of the triple match to thr wheel size? Honestly, a few degrees of rakr on a triple with more offset and a drop could fix the issue, potentially. Id actually have to figure out the numbers. Getting someone to design and cnc it wil be expensive.
 
Ok so Devin the legend from conito moto sent me this
4330fa182f9436ead788749a6cfc4b36.jpg


Those numbers arent too far from stock trail but i still need to work out rake, and like you said Lights out first my pregnant wife would have to install the motor rebuild the frame put the wheels on and then somehow understand how to work out the rake ....chances are slim

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LightsOut said:
My knowledge about this is mostly theoretical, but from what I understand rake angle in itself doesn't affect handling that much? What affects handling is primarily the trail number (which is of course a product of rake angle). In the "Tony Foale test" (https://tonyfoale.com/Articles/RakeEx/RakeEx.htm) they experimented with even using even 0 degree rake angle and found it handled pretty normally as long as the trail was kept the same.

..just saying that if the decreased rake angle results in less trail (and thereby twitchy/dangerous handling), then a smaller offset in the triple would pull the trail in the opposite direction. Could be like jag767 says it's way too small difference to compensate for the result of the decreased angle though.

Measuring rake angle with the current setup sounds like it'd be a good idea to put numbers on the change? (good luck getting the wife to do that ;) )

Does the forward lean have other implications than rake/trail? Would weight distribution change and affect handling?
Very interesting read

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If i read that right (hard to read on my phone) youve gone from 27 to 23? Thats a low number. Lots of different stress on the frame it wasnt designed for. If a custom triple is on the table, im thinking do a 1 inch drop, increase the offset, and add 2 degrees of rake in the triple. At that point I'd wager youd be ok. The rake in the triple is a chopper thing, but i see not reason just adding a tad would hurt. If someone knows better please correct me.
 
Devin at cognito moto said that this particular set up would improve the handling although i was unable to provide him with tye rake so he was only going of the information i could provide

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cb250nproject said:
Devin at cognito moto said that this particular set up would improve the handling although i was unable to provide him with tye rake so he was only going of the information i could provide

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I just reread. And yea, you don't need more offset with a 17. The rake is an issue though. And the ground clearance would be a potential worry for me. Can you drop the rear an inch without the rear tire hitting the seat?
 
jag767 said:
I just reread. And yea, you don't need more offset with a 17. The rake is an issue though. And the ground clearance would be a potential worry for me. Can you drop the rear an inch without the rear tire hitting the seat?
10ca6336a8086025704d965dd7e60d66.jpg


I don't think the tyre will hit the seat



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I was asking if you could go with shorter shocks, which you definitely cant. Basically at this point in the game your only option is a custom triple.
 
jag767 said:
I was asking if you could go with shorter shocks, which you definitely cant. Basically at this point in the game your only option is a custom triple.
Definitely cant i think the rear is at its limit plus i dont want to lower it anymore for fear of clearance issues :/ hmmm

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If you are worried about ground clearance and rake, Cognito moto make a nice stepped top triple clamp, a cheap way of raising the front end. I suggest you put the bike back together then worry about the problems as they arise. ie if the bike has ground clearance issues raise the front or rear, IF the front end is nervous then fit a steering damper. Unless you fit a progressive damper or linkage it will make slow speed (traffic) maneuvering heavy. Most road bike owners with steering dampers are just trying to show off, how aggressive do you ride on the road?. I say go with what you have, looking great by the way, and later work out the problems or issues YOU do not like. Often I find things I expect to be a problem are not and others I had no idea cause me much swearing!!! Good luck
 
Popeye SXM said:
If you are worried about ground clearance and rake, Cognito moto make a nice stepped top triple clamp, a cheap way of raising the front end. I suggest you put the bike back together then worry about the problems as they arise. ie if the bike has ground clearance issues raise the front or rear, IF the front end is nervous then fit a steering damper. Unless you fit a progressive damper or linkage it will make slow speed (traffic) maneuvering heavy. Most road bike owners with steering dampers are just trying to show off, how aggressive do you ride on the road?. I say go with what you have, looking great by the way, and later work out the problems or issues YOU do not like. Often I find things I expect to be a problem are not and others I had no idea cause me much swearing!!! Good luck
Cheers for that i think that may be the best course of action. Trial and error until complete

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Agree with Popeye, try it out! I'd probably also measure rake, trail, ground clearance and swingarm droop just to put measured numbers on those things rather than calculated ones.

Did some calculations with the numbers available and didn't see a dramatic change in trail. Could of course be way off, but my bet is that when you get to ride it, it'll feel and handle well!


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Trail isn't the problem. His nemesis will be speed bumps, and being stable at 55mph ;D

Don't feel bad, I screwed up a bike so bad I had to cnc a new oil pan, and fab a new exhaust just to have sufficient ground clearance to clear ant hills. It happens lol.
 
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