gumpt1oo
Scrambler
A friend of mine told me about this mod, so I thought I would share it here.
The standard bonneville front forks have no adjustment as standard, but my mate found out that the Thruxton preload caps fit the bonnie forks, with a little bit of modification, giving them up to 17.5mm of adjustment!
First I bought a pair of adjustable preload caps ( part no T2049013)
and a pair of fork disc washers (part no T2049019)
Total cost £74.
Before I started, I checked the static sag (the amount the fork compresses under the bikes weight) which was 37mm, then the static sag plus my weight, which was 52mm.
I checked this by using a cable tie around the fork.
Static sag.
Static sag plus rider
As you can see from the photo, the adjustable preload cap is longer than the standard cap.
Because the fork spacer is flush with the fork tube when the standard cap is removed, 21mm has to be cut off the spacer in order to fit the preload cap.
21mm piece cut off spacer to allow preload cap to fit.
While I had the bike in bits I also fitted a pair of Hagon progressive fork springs.
The picture above shows the shortened spacer, disc washer and preload cap ready for fitting. The top spring is the Hagon and the bottom spring is the stock item for comparison.
I checked the sag again on completion, static sag is 32mm, and with rider sag is 48mm.
I have now got +12.5mm/-5mm of adjustment to play with.
This is how they look fitted.
Another point worth mentioning is the amount of oil to put in the forks. The haynes manual states with the springs removed and the forks compressed the oil should be 120mm down from the top of the fork tube. The Hagon instruction states 150mm. I phoned Hagon's who said that because the progressive spring displaces more oil than the standard spring, less oil is required.
And finally I found one of these really useful to get the oil level exact!
The standard bonneville front forks have no adjustment as standard, but my mate found out that the Thruxton preload caps fit the bonnie forks, with a little bit of modification, giving them up to 17.5mm of adjustment!
First I bought a pair of adjustable preload caps ( part no T2049013)
and a pair of fork disc washers (part no T2049019)
Total cost £74.
Before I started, I checked the static sag (the amount the fork compresses under the bikes weight) which was 37mm, then the static sag plus my weight, which was 52mm.
I checked this by using a cable tie around the fork.
Static sag.
Static sag plus rider
As you can see from the photo, the adjustable preload cap is longer than the standard cap.
Because the fork spacer is flush with the fork tube when the standard cap is removed, 21mm has to be cut off the spacer in order to fit the preload cap.
21mm piece cut off spacer to allow preload cap to fit.
While I had the bike in bits I also fitted a pair of Hagon progressive fork springs.
The picture above shows the shortened spacer, disc washer and preload cap ready for fitting. The top spring is the Hagon and the bottom spring is the stock item for comparison.
I checked the sag again on completion, static sag is 32mm, and with rider sag is 48mm.
I have now got +12.5mm/-5mm of adjustment to play with.
This is how they look fitted.
Another point worth mentioning is the amount of oil to put in the forks. The haynes manual states with the springs removed and the forks compressed the oil should be 120mm down from the top of the fork tube. The Hagon instruction states 150mm. I phoned Hagon's who said that because the progressive spring displaces more oil than the standard spring, less oil is required.
And finally I found one of these really useful to get the oil level exact!
