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What am I trying to correct?


CornerCarver

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I've spent hours researching offsets and trail numbers and reading Race Tech's Motorcycle Suspension Bible. The data shows most of the best handling bikes have around a 30mm offset with high 90s to low 100s trail values (CBRs, GSXRs, R1s... early R1s and RC51s are exceptions) and rakes of 23* to 24*; this was also confirmed by a reliable suspension expert.

The stock 5th gen VFR chassis geometry doesn't cut it for this application... and it wasn't designed too. No fault, no grandiose claims that I can engineer better than Honda. Just me attacking a challenge to take something I love and adapt it to a new, more specific application.

Based on this, and some more expert input, I'm going to shoot for an initial set-up of 30mm offset, around 102mm trail, and ~24* rake on my 5th gen track bike. My '09 ZX14 50/54 USD forks are scheduled for delivery tomorrow... so I can start the measuring and wrenching and stop the jabbering!!! Build thread to follow...

To modify your rake to work within the design parameters of above mentioned GSXR/CBR are you going to cut your headstock from the frame and weld it back at that desired 24* angle?

If not, perhaps an eccentric in the steering stem mount will allow for enough rake correction.

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I've spent hours researching offsets and trail numbers and reading Race Tech's Motorcycle Suspension Bible. The data shows most of the best handling bikes have around a 30mm offset with high 90s to low 100s trail values (CBRs, GSXRs, R1s... early R1s and RC51s are exceptions) and rakes of 23* to 24*; this was also confirmed by a reliable suspension expert.

The stock 5th gen VFR chassis geometry doesn't cut it for this application... and it wasn't designed too. No fault, no grandiose claims that I can engineer better than Honda. Just me attacking a challenge to take something I love and adapt it to a new, more specific application.

Based on this, and some more expert input, I'm going to shoot for an initial set-up of 30mm offset, around 102mm trail, and ~24* rake on my 5th gen track bike. My '09 ZX14 50/54 USD forks are scheduled for delivery tomorrow... so I can start the measuring and wrenching and stop the jabbering!!! Build thread to follow...

To modify your rake to work within the design parameters of above mentioned GSXR/CBR are you going to cut your headstock from the frame and weld it back at that desired 24* angle?

If not, perhaps an eccentric in the steering stem mount will allow for enough rake correction.

I'm hoping with a little elevation of rear ride height, and possibly lowering the front a little, I want to see what kind of rake I can achieve... I'm hoping to get down from the stock 25.5* to close to 24*. I can calculate and spreadsheet it to death, but until I have the parts assembled and start tweaking it is all theoretical.

I'm not currently looking at cutting and re-welding the frame... that is kinda outside the scope and budget of my modest attempt :)

For me, it will be easier to tell what can be achieved when I have a rolling chassis... i uncrated my engine and swapped the lower cushion for a 6th gen today... the real fun starts next weekend... temperatures permitting, I don't have a heating solution for my 2 car garage.

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I recommend a couple of 1000

Watt halogen work lamps for garage heating.

?

Nice!

Kill two birds with one lamp... heat and illuminate :D

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