Nothin’ new in t’ world - linkage forks...

[2manyoranges]

goodness....everyone's thoughtful text and comprehensive photographs have turned this into a kind of reference/catalogue thread, which might be very useful for people in the future. Worth sticky-ing or archiving....?

 

[TheAwesomePossum]

definitely my favorite linkage fork (albeit just from the looks)

Well when it comes to beautiful linkage forks i would definitely put the AMP F4 BLT in first place. It manages to warm my heart everytime i look at it. And in my opinion it's still a serious 3.25" travel lightweight option in case you're rollin' on twentysixes

 

[Dr Dremel]

Can´t argue with that, AMP definitely up there also, especially in combination with the frame. Gorgeous bike! Interesting to hear your thoughts on the performance. I would love to take these later ones to the test, I have one of the earlier forks (one piece steel) myself.

 

[danson67]

The biggest difference between the early and later versions of the AMP fork is the geometry of the linkage.

You can spot an F1 by the steel legs, and the preload screw underneath the linkage, not on top, working on a forward sloping spring.
Also available as a rare F1 DH, with dual dampers.



There was an F2, which is fairly rare, which used this same linkage box, but with the later familiar aluminium legs.



This early linkage box gave a falling rate, so they tended to collapse under heavy load and braking.

The falling rate was sorted by a change in the linkage positions and a realignment of the spring position on the F3.
The F4 BLT has a scaled up version of the linkage, to give longer travel, but the big change was the two shock units with 3 different springs available.
Loads of tunability from 2x3 spring weights, options for oil weights in the dampers and adjustable preload from small clip rings on the damper bodies.



Then there are the carbon-legged versions of the F3 XC and F4 BLT.

Come and join us at the AMP-oholics Facebook Group.

All the best,

 

[Dr Dremel]

Excellent write up, especially regarding the geometry old vs new. Thanks again!

 

[2manyoranges]

I loved the AMP forks - later path = excellent, tunability = good for time, beautiful machining.... but ....

Actually early legs in steel were great - solid and dependable
Later legs in alloy were as solid as fitting the front wheel to the frame using overdone spaghetti - very scary

The manic pursuit of lightness at the expense of sensible strength was a 90s problem I think. Like Colin Chapman and Lotus during the 60s. I have never heard of a failure of the AMP legs - but they are scary nonetheless....

 

[yakboy]

I love my Mk 1's too. Only give 35mm of travel but it's very sensitive and really irons out the lumpiness of a trail. Also I had magura mount's brazed on so braking is great too.

 

[danson67]

I loved the AMP forks - later path = excellent, tunability = good for time, beautiful machining.... but ....

Actually early legs in steel were great - solid and dependable
Later legs in alloy were as solid as fitting the front wheel to the frame using overdone spaghetti - very scary

The manic pursuit of lightness at the expense of sensible strength was a 90s problem I think. Like Colin Chapman and Lotus during the 60s. I have never heard of a failure of the AMP legs - but they are scary nonetheless....

Agreed, I have a set of carbon F3 XC which don't save much weight (50g IIRC), but are much stiffer. I presume this was also why AMP switched to fatter tubes for the legs on the F4 BLT.

Maybe a set with the F3 linkages, but steel legs wound be optimum?

All the best,

 

[TheAwesomePossum]

Can´t argue with that, AMP definitely up there also, especially in combination with the frame. Gorgeous bike! Interesting to hear your thoughts on the performance. I would love to take these later ones to the test, I have one of the earlier forks (one piece steel) myself.

Thanks! I find it has quite smooth action, especially when set up properly. Like Dan said you can fiddle around quite a lot with spring rates + preload and oil viscosities. Havent experienced any bottom outs but tops out when bushings are worn out and dampers lack oil.
To be honest i'm struggling much more setting up F1s/F2s/F3s to my liking, maybe it's time to renew all the bushings

Maybe a set with the F3 linkages, but steel legs wound be optimum?

I think i've read once that the steel legs were made out of Tange Prestige tubing, but could be nonsense. With the little increase in travel + progressive action it might be an interesting option, especially in optimizing the performance of a ~period correct AMP B2 build in a subtle way. I also had the feeling that the DH dual damper setup had smoother action, maybe thanks to the symmetry

 

[syncrosfan]

Great thread!
Here's my addition: Kestrel Monolith show-bike, and a Monolith frame with Rebound fork (no connection with the Kestrel aside from the naming coincidence)