# AMP Research fork questions



## SStrailrider (Dec 4, 2006)

Hi Everyone! Just registered on this forum, thought I'd say hello.  

I am currently building an older Slingshot frame ('96-'97 give or take a year.) I always liked the looks of the AMP forks and was thinking of using an F3 or F4 if I could get my hands on one. Before pursuing this any further, I just wanted to know if anyone here has used these forks and if there are any problem areas associated with them. Also, what size are the steerer tubes and are they threaded or unthreaded? I know that AMP had thier own version of disc brakes in the 90's, so I'm sure most of these forks have some type of disc mounts on them. But are they compatible (mount wise) with today's common disc brake mounts? And what about tire size? What's the largest front tire I could use? Exactly how much travel did these forks have?

I know I am asking a LOT of questions here, but any info is appreciated. Heck, give me a history lesson on the forks and frames, I'm into that sort of thing. I saw some of the pics on the Slingshot thread, which is were I got the idea to use the AMP Research fork. I had my doubts about these even being compatible with a Slingshot frame due to the fork linkage and frame cable/spring assembly interfering. This appears to not be an issue. But if someone has tried this and had poor results, please let me know. That's what this post is all about!!!! Thanks!!! hh.


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## DeeEight (Jan 13, 2004)

Amp forks only work with Amp discs, but Rockshox disc brakes being improved versions of the Amp calipers will fit the Amp mount adapters (and vice versa, you can use the rockshox I.S. bolt pattern adapters with Amp calipers), and Amp still makes the adapters for their forks and brakes. I don't know if Amp still has complete brake assemblies or not but they probably do. They still make replacements parts for everything else they did previously (you can't say order a complete frame, but you can get creative and build one ordering all the parts for one in sub-assemblies).


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## JmZ (Jan 10, 2004)

SStrailrider said:


> Hi Everyone! Just registered on this forum, thought I'd say hello.
> 
> I am currently building an older Slingshot frame ('96-'97 give or take a year.) I always liked the looks of the AMP forks and was thinking of using an F3 or F4 if I could get my hands on one. Before pursuing this any further, I just wanted to know if anyone here has used these forks and if there are any problem areas associated with them. Also, what size are the steerer tubes and are they threaded or unthreaded? I know that AMP had thier own version of disc brakes in the 90's, so I'm sure most of these forks have some type of disc mounts on them. But are they compatible (mount wise) with today's common disc brake mounts? And what about tire size? What's the largest front tire I could use? Exactly how much travel did these forks have?


Amp forks were available in both 1" and 1 1/8" threaded and threadless. Most that pop up on E-Bay ar 1 1/8 threadless or 1" threaded. Bummer, I need a F-3 1" threadless.

The disc mounts are Amp specific - just as D8 says, but if you have friends who work at a machine shop, you should be able to get 'em to work with ya to get an adapter made. There were a few that made their way to E-Bay.

The F-3 was a hair over 2" of travel, the F-4 was an 80mm fork.

Good luck,

JmZ



SStrailrider said:


> I know I am asking a LOT of questions here, but any info is appreciated. Heck, give me a history lesson on the forks and frames, I'm into that sort of thing. I saw some of the pics on the Slingshot thread, which is were I got the idea to use the AMP Research fork. I had my doubts about these even being compatible with a Slingshot frame due to the fork linkage and frame cable/spring assembly interfering. This appears to not be an issue. But if someone has tried this and had poor results, please let me know. That's what this post is all about!!!! Thanks!!! hh.


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## DeeEight (Jan 13, 2004)

1993 the fork was known only as the Amp Link (or Concept Link for the ones sold by Univega), and came in 1", 1 1/8" or 1 1/4" steerers. You found them usually on Mongoose Amplifiers, Amp B-2s, and Univega hardtails. Travel was 2", Crmo lowers, CrMo steerer, Al crown/linkage. Univega forks were often 1" steerer as Univega clung to the standard headset size till the late 90s. 

1994 the fork became know as the Amp 1 and Amp 2-DH forks (the DH model got a second thru-shaft damper on the left side of the crown/linkage). Same construction as the previous year but the 1 1/4" steerers were discontinued and instead Amp offered the part #B754 which was basically a set of headtube reducers for the frame to accept 1 1/8 headsets. Travel was still 2" for both versions, and you could get a thickwalled aluminium steerer for the 1 1/8 threadless forks. The steerer lengths for threaded models were 130mm, 165mm, 200mm and 235mm in both 1" and 1 1/8". Ride hight was given as 16.75" unloaded, and 16.5" with rider sag, rake is 1.95".

1995 came the fork being called the F-21, with a change to aluminium lowers instead of CrMo and the availability of the disc mounts on the forks (for Amp discs of course). Travel is still the same but the aluminium lowers shed about 3 ounces of weight from the fork going from 2.6 Ibs (with the shortest steerer) to 2.4 Ibs (my Amp 2 fork with 1 1/8 threadless Al steerer cut 7" long and SFN installed was 2.75 Ibs).

1996 was the final Amp fork redesigns, the F-3 XC replacing the F-21 with an increase to 55mm of travel, and the option of carbon legs to cut the weight down to 2.2 Ibs and the new F-4 BLT being their "long travel" model, also with al or carbon leg options, 81mm travel, 2.9 Ibs claimed weight, and dual coil springs and thru-shaft shocks (springs being moved to the sides and around the shocks, instead of under the crown between the links with all the other forks). 

All Amp forks used a linkage geometry that added what they called their patented Kinematic lockout which resisted pedal induced bobbing. Basically shoving downwards on the bars, like you would when sprinting, tried to push the legs straight down also. Except Amp forks didn't respond to straight up/down forces very well because of the linkage paths. To get the Amp fork moving, you need a bump to hit the wheel in such a way that it pushes BACK and UP at the same time. In terms of reviews by mag writers/editors, they often complained that the forks didn't respond well to jumping and such like oh, rockshox forks did, but they did handle square-edge impacts like tree roots and rocks better than telescoping forks did.


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## Bigwheel (Jan 12, 2004)

While the AMP fork is good, and I have spent considerable time on an F4 myself, they do tend to wear out pretty fast in the bushings. Easy enough to replace them though and the shock absorbers themselves are also easy enough to rebuild too and as mentioned the parts are still available. I used to claim though that I would rather ride my AMP hosed than a well tuned tele fork as the action for my style of riding is just that much better.

But for the same type of action (Parallelogram/Linkage Fork) that is lighter and has much greater longevity you should look around for a Fournales fork. They are on eBay quite often for example brand new. They are a different execution, more like the Girvin's/Noleens, but use real bearings at the pivots and have a decent air shock as that is mainly what Fournales is noted for. They are headtube specific though and you need to get either a small, med. or lg. depending on the length of yours. Plus they come either able to run V or disc brakes (standard mount).

They are no longer being made and the closeout pricing on them is about a 1/3rd of their original cost. 

But having also spent a good deal of time aboard a 'Shot in the past I have to say I prefer riding them with a rigid fork over any type of suspension fork as the "Sling Power" just works better that way for me. In fact I stopped liking the SlingShot I had in 90' when I switched to a front shock and didn't really realize why at the time but after I ran my 29" AMP F-4 conversion on a Big Shot here a few years ago and while I liked it better than the WB fork the bike never felt as good as when it had a rigid fork on it and that is the way it ended up although I have moved on from it as I didn't like the whole package as a 29"er as much as I thought I would.


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## stan4bikes (May 24, 2006)

great info! you guys are awesome for us novices trying to learn. thanx....


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## sgltrak (Feb 19, 2005)

Bigwheel said:


> While the AMP fork is good, and I have spent considerable time on an F4 myself, they do tend to wear out pretty fast in the bushings.


I second the wear on the bushings, but I thought at one time they offered a bearing upgrade.

I like the ride a bunch, running a F3 on my '93 Team Paramount for 9 years. The shock was best for larger, front initiated impacts, and didn't react well to small, or stutter bumps.

I sent it back to them twice for rebuilds and found them friendly and helpful. Even though they do not still sell bike stuff, they still support the product they did sell. I broke the coil spring about a year and a half ago, and the shock was blowing oil, and they fixed both. Mine is completely re-conditioned and sitting on my workbench, waiting to be re-installed, but I got used to the Ritchey rigid fork again and haven't taken the time to put the F3 back on.


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## SStrailrider (Dec 4, 2006)

WOW!!!! Thanks so much for all the info. I never would have thought that I would get such informative and intellegent responses. (Based simply on replies I have gotten on other forums in the past. -not MTBR, by the way.)

One other question, though. What is the largest tire that can be used with this fork. It may just be in my head, but I have a 2.35 front tire on my trail bike at the moment and like the larger volume tire as opposed to the 2.0 that I was using before. Of course these are different model tires, I use differnent air pressures, blah, blah, blah..... so lots of reasons they could ride differently.

BUT, if I wanted to use a 2.3 tire, would it fit without any contact with the linkages under compression?

Thanks again for the responses, you guys are awesome!!!


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## ROG30Y (Sep 10, 2004)

I remember having one on my Univega......never was very compliant compared to the mag 21,squeeked pretty bad most of the time and i bent two steerer tubes.

i still think its a cool looking fork though and am looking for one myself for my steel hardtail.


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## sgltrak (Feb 19, 2005)

Measurements on my '95 F3 Aluminum

Axle center to crown is 13.75" or 350mm. Compressed linkage shrinks this very little. Narrowest part of fork at crown, just above leg insertion, measures 2.75" or 70mm.
Distance between cantilever mounts is 2.25" or about 57mm.


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## DeeEight (Jan 13, 2004)

I think you measured to the bottom of the crown there, its supposed to be to where the fork race goes.

As to the bushings, the original forks had these hard annodized aluminium shafts with just delrin bushings on the ends, held together with circlips. The delrin was exposed to the elements and wore fast, as did the annodizing on the shafts (which then shrunk their diameter) and you'd get lots of play in only six months or so. The bearing upgrade (which I did on mine) is to stainless steel hollow link pins, and proper Bronzelite DU bushings which last MUCH MUCH longer.


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## sgltrak (Feb 19, 2005)

DeeEight said:


> I think you measured to the bottom of the crown there, its supposed to be to where the fork race goes.
> 
> As to the bushings, the original forks had these hard annodized aluminium shafts with just delrin bushings on the ends, held together with circlips. The delrin was exposed to the elements and wore fast, as did the annodizing on the shafts (which then shrunk their diameter) and you'd get lots of play in only six months or so. The bearing upgrade (which I did on mine) is to stainless steel hollow link pins, and proper Bronzelite DU bushings which last MUCH MUCH longer.


D8,
You are correct. I measured from the center of the axle to the underside of the crown, in order to give the OP a tire clearance measurement.

Thanks also for the reminder on the bushing upgrade. I now remember having that upgrade done in 1997, and again in 2005, along with the spring and shock replacement.


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## SStrailrider (Dec 4, 2006)

Can you still get the bushing and shaft upgrades? Do these come from AMP?


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## sgltrak (Feb 19, 2005)

SStrailrider said:


> Can you still get the bushing and shaft upgrades? Do these come from AMP?


I think so.

http://www.amp-research.com/build/bikes.asp

My contact there for my repairs was Brion.


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## itsdoable (Jan 6, 2004)

I've ridden a F4-BLT for several years, but it's currently off bike. They are light, but require regular maintenance. I think I was servicing the shock units every 3-6m when I was riding it regularly, and the bushings once a year min. I made my own disc mount adapter for it since they do not sell one for ISO discs. There were several reports of injuries from broken forks, but those most likely had to do with exceeding it's design parameters - having a long travel fork made people think they could free-ride it, and there are no sub 3lb forks that are rated for that. This was true with thier frames too, which worked fine in the XC field.


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## DeeEight (Jan 13, 2004)

I got parts for my frame a month or so ago, brion still handles the Amp bike stuff.

[email protected]


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## AndrewTO (Mar 30, 2005)

Quick Q - what did the carbon legs loos like? Where they a carbon fiber appearance or plain black or ..... ? (maybe like itsdoable's?)

Also, if one were to find an Amp with dual coil-overs does that mean it's the BLT or was there another version ..... or maybe it's been bastardized?


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## alohachiimoku (Apr 7, 2006)

Its looks like plain black legs unless you look closely.
Dual coil version called F4 that longer travel than F1,F2,F3.
I can up some pic,if you like.


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## JmZ (Jan 10, 2004)

alohachiimoku said:


> Its looks like plain black legs unless you look closely.
> Dual coil version called F4 that longer travel than F1,F2,F3.
> I can up some pic,if you like.


The F-4 had dual shock on each side. This is the 3" Travel version.

The older version F-?? had a dual damper, but a single spring version. This is th 2" and change version. The earlier ones were a falling rate design, and the later ones were a rising rate design.

The carbon is pretty subtle, but is a carbon weave. Don't think Kestral Carbon bar, closer to Easton (without a bunch of graphics). Still running my F-4 Carbon on the hardail.

JmZ


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## AndrewTO (Mar 30, 2005)

Okay, so, there was one version, the BLT, with dual coil-over (and 81mm travel) and another version which was single coil/dual damper (55mm travel)? And this same single coil/dual damper fork had the single spring under the steerer tube? Is that correct?

Also, the pic of the fork in itdoable's post is clearly an aluminum-legged piece, right? Doesn't show any sign of a carbon weave whatsoever. (thanks JmZ)

aloha - yeah, sure it would help at this point. Just be sure to let us know if it's the carbon version or not ..... i'm lost enough already. :lol: Thanks!


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## DeeEight (Jan 13, 2004)

I described all the models, the Amp-2DH is 51mm travel, single coil, double dampers. Looks like every other Amp fork EXCEPT the F-4 BLT and from the right side, would probably be mistaken for the original Amp-1. They didn't actually put F codes on the first two forks, but it isn't neccessarily out of line to call them F1s and F2s for simplicity, especially since the called the 3rd version was called the F-21 (it was an airforce reference, this was mid-90s remember and the air force was developing the ATF program... lots of brands picked names for bicycle parts with aerospace references).


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## itsdoable (Jan 6, 2004)

AndrewTO said:


> Also, the pic of the fork in itdoable's post is clearly an aluminum-legged piece, right?


It is indeed alimunium, painted black stock.


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## fatchanceti (Jan 12, 2005)

AndrewTO said:


> Quick Q - what did the carbon legs loos like? Where they a carbon fiber appearance or plain black or ..... ? (maybe like itsdoable's?)


these aren't great, but my digi cam was pretty lousy back then:



and


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## fatchanceti (Jan 12, 2005)

found one more:


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## AndrewTO (Mar 30, 2005)

Dee - yes, it appears that while I read the description for 1994 properly I failed to "clue in". Sorry and thanks for the confirmation. :thumbsup: 

Its & fat - okay, got it! The pics are very helpful. The carbon appearance is very ..... carbony.   :thumbsup: :thumbsup:


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## AndrewTO (Mar 30, 2005)

Just wanted to pop-in quick to say thanks to everyone for the help. I am now the owner of an Amp F4 BLT. 

Sooooo, THANKS!!!!! :thumbsup: 

And some pics in gratitude. Tinker time!!!!!!!!!!!!!!!! :devil:

Oh, itsdoable, extra thanks for the adaptor pic.


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## DeeEight (Jan 13, 2004)

Now when you email Amp to order parts, remember to buy the bushing press tool also. Incidently you can order the crown/steerers also still, so you could get a longer one to use it on the Ti frame. Oh and is this a good time to mention I have a complete NOS Amp D-1 front disc kit (brake, hub, rotor, hardware) to fit those forks?

(I have to tease him since he bought the Ti frame off me and I didn't get a chance to ship it yet).


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## AndrewTO (Mar 30, 2005)

DeeEight said:


> Now when you email Amp to order parts, remember to buy the bushing press tool also. Incidently you can order the crown/steerers also still, so you could get a longer one to use it on the Ti frame. Oh and is this a good time to mention I have a complete NOS Amp D-1 front disc kit (brake, hub, rotor, hardware) to fit those forks?
> 
> (I have to tease him since he bought the Ti frame off me and I didn't get a chance to ship it yet).


Har har, very funny. Maybe I should show up at your door this weekend?

:lol: Nah.

Anyways - yeah, might be a good cantidate for the Eclipse. Gotta see about geometry yet, let alone fit and feel.

Remember Larry, out in the praries? He'll hook me up with what I need. Gotta get a steerer tube first. Not sure if i'll have one made at work or just buy one. Timing is a big issue right now.

My original intention was to simply fab an Amp~>ISO disc mount just like itsdoable's. When I saw his it was just favourable re-assurance that it'll work out fine. (but thanks for the Amp brake offer all the same!) I can also get the v-brake mounts easily enough and probably will - I like the option to switch if I feel it's wanted/needed.

Once I get a little time on it THEN i'll decide if I like it enough to get the "full monty" of bits and pieces - shock rebuild, all the bushings, stuff like that. Piss me off, though - one of the bolts is buggered up (the hex) and they're not metric. No ti/al upgrade.    WTF?!?!??!?!


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## richieb (Oct 21, 2004)

All these AMP pictures are flashing me back to '95...when I had 2 steerers come loose in the crown, bushing replacements every 2 months and chronic shock hissing...

The upside is the Modified Mag 21 I replaced it with was AWESOME!!!



rb

OH, and BTW, all the tire clearance issues I ever encountered with AMP forks had nothing to do with width or height in the fork blades themselves. The issue comes into play when the earlier forks are compressed/bottomed out over big bumps. The tire can actually buzz the spring preload screw under the crown, sometimes to the point of nasty things happening to the rider and/or bike. I think the instructions with mine said no more than a 2.1 inch tire, or something like that...

This wasn't an issue on the F-4, as the springs are side-mounted, and not in the way (you all will notice the machined clearancing under the crown, however, to address exactly this problem.)


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## itsdoable (Jan 6, 2004)

AndrewTO said:


> ...Piss me off, though - one of the bolts is buggered up (the hex) and they're not metric. No ti/al upgrade.    WTF?!?!??!?!


Those bolts are aluminium, so they round out very easily (btdt) - but you shouldn't worry about that too much, AMP's rebuild kits included replacement bolts - at least they did when I was still servicing the beast regularly.


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## JmZ (Jan 10, 2004)

Updated bolts are available, and they're steel so they don't round out like the older alum ones did. 

Worth a bit of extra grams.

JmZ


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