Coop500

Yesterday I was given a Specialized Rockhopper FS, research online makes me believe it is a 1994 model. It is in great shape except the forks, they just collapse under their own weight. They are SR DuoTrack 8001. I can't even see how you could take them apart to try to lock them out so I would like to replace them with rigid forks. The bike has cantilever brakes and a 1" threaded steer tube (well the quill stem measured 1"). Am I going to have a hard time finding inexpensive forks to fit this bike? I can ride it as is so it's not a big deal if I can't, but figured since they don't work it might be lighter to ditch them. Plus a mounting point for fenders or a rack would be nice.

I only plan to use it as a rails-to-trails bike and short on-road rides around my house.

The bike:

FBinNY 

You could replace the fork (singular) with a standard rigid 26" mtn fork, there come at all price and quality levels. There is a drawback in that it'll lower the front end by about 2-1/2" from the original design height. Dropping the front end makes the bike about 1-2° steeper, approximating the geometry of a road bike, but also drops the handle bars by that amount, so you may want to switch to a taller stem.

Or if you want to keep the front end at the design height, there are suspension corrected forks built with added height to maintain the same overall crown to axle length of suspension forks. These are more of a niche item, and the selection tends to me more limited to better quality forks at higher prices.

Cheap, self serving plug follows. I have a decent stock of Chrome-moly suspension forks built by Viscious Cycles in various heights that I'm looking to close out at $150 or so inc, postage within the US. PM me if interested.

Coop500

I did already plan on a high stem and bars so a lower fork won't bother me. Thanks for the offer, but I am on a pretty tight budget, hence accepting the free bike in the first place.

For the record, I know it's fork not forks, but it's an old habit. As a kid in the 80's I was big into BMX and magazines used to call them forks and that got me started adding the 'S'. Also I used to be a motorcycle mechanic and even have had manuals that call them forks, so it's hard for me to remember to not add the 'S' . I'll try to get better about it haha.

LesterOfPuppets

If the quill diameter measured 1" then you have a 1-1/8" steerer.

I'd probably just go threadless if I were you. If you have a bike shop with used parts nearby that would help, could get a fork for quite cheap, it's easier if you get headset and stem first so you know their stack heights, this way you can get a long enough steerer tube.

Pricepoint.com has cheap stems, around $12 usually. They probably have some $20-25 headsets too.

FBinNY 

Don't worry about the S, as long as you don't try to put two forks on one frame. You shouldn't have a problem finding a good value in a rigid fork, as long as you don't limit yourself to suspension ready models.

Don't forget that you do have to limit yourself to forks with canti bosses, or disc brake mounts if you want to invest there (might make sense if this is intended as an all weather commuter. Some forks have both canti- and disc brake mounts which (if there's not a big upcharge) might make sense by providing for a future upgrade.

OTOH, if you're on a budget, you should track down a manual for your fork, which I believe is a simple elastomer shock fork, and either replace the elastomers with a super stiff set, or see if there's a way to bond the system as a rigid fork, possibly substituting wooden dowel rod in lieu of the elastomers. You can also mix stiff and pliable elastomers to make a fork that has limited travel, yet can take up some of the smaller bumps of poor roads.

Coop500

Thanks! I was already looking at the wrong parts. I think I will go out now and pull the forks off and get some better measurements.

FBinNY thanks for your help and advice. I did a little search last night and couldn't find anything on this fork. It doesn't have caps, it looks like the legs are pressed into the crown so I was trying to find the manual to see how to disassemble them. No luck yet though.

Retro Grouch 

Lower height isn't the issue. It's the head tube angle. Lowering the fork height very much will give you a steeper head tube angle which will affect your bike's handling. I'd be looking for the rigid fork that has the longest dropout to crown race length.

FBinNY 

The upper struts are pressed into the crown. You need to pull back the boots and look for a way to allow the lower strut to come off the end if you want to service the fork.

There's no need to remove the fork to measure anything. The steerer is either 1" or 1-1/8" and can easily be measured indirectly by measuring the OD of the quill, which will be 7/8" or 1" respectively. 7/8" is the same as the handlebar, so you can eyeball it, or make a gauge caliper out of cardboard and confirm.

The threaded vs threadless change can take you beyond your budget, since you're replacing both a stem and headset, but if you're replacing the stem anyway might make sense, by increasing the fork choices, and simplifying fitting.

BTW- you might want to start a new thread "servicing DuoTrak forks" and the headline might catch the eye of someone who can help.

JanMM

One of the posts on this thread claims Due Track forks are filled with lead: https://www.bikeforums.net/archive/in.../t-261931.html

FBinNY 

This is a valid point, but not as critical as you might imagine. Dropping the head 2-1/2" steepens the head angle by about 3°, but given that mtb head angles tend to be shallower than road to start with, there's some room to play with. Overall the experience of folks who replace with standard forks is that they mostly don't notice the difference when riding.

I'm a believer in trying to maintain geometry, but for non-high performance use find it barely matters to most people.

Coop500

I wanted to check the grease in the bearings anyway (pretty dry so I am glad I did). The steerer is 1-1/8", the quill 1". I have dial calipers I was using to do the measuring. So it does change my option some as I was thinking it was a 1" steerer.

I will head the advice about not getting a fork that is too short. This fork (extended) from the dropout to crown race is right around 16". The steerer is 5-5/8" from the crown to top of threads. 5-1/2" if I go from the top of the crown race.

Coop500

The inquisitive mechanic in me couldn't resist. I took a long look and figured out how to take this fork apart. No springs like I expected, also no oil like I expected. I mainly did this for curiosity purposes because I definitely want to replace them with a rigid fork with mount points and chuck these in the dumpster haha.





After looking at this it seems someone was inside this fork and removed some parts. no wonder it doesn't work at all. (3/4 down the article is this fork).

https://www.mtb-kataloge.de/Bikekatal.../SunTour93.pdf

FBinNY 

It sounds like the prior owner removed the springs or elastomers. If the fork is otherwise OK elastomer kits are available and very inexpensive, or you can mix a length of wooden dowel with elastomer for a limited travel suspension. That would be much less expensive than replacing the fork.

BTW- if you do replace the fork, and want to approximate the original geometry, don't forget to add about 2" or so to the collapsed length of the fork to get the original riding height.

Coop500

I just made some 1.5" spacers for now and the fork is rigid. I don't think I want to put any money into this fork I would rather buy one that better fits my needs.

Thanks again to everybody that posted with advice and help.