Replacing front shock with rigid fork, on 26er ???
 

Apologies for asking what's probably been asked a few times before. I have a 10-year-old 26" Trek mtn bike that's set up and used as a road runner, and it has some lower end Rock Shox that may or not be long for this world, and I'm looking into going with a rigid fork (that's disc compatible).
My concern is that the new fork will significantly lower the front end, as I've read elsewhere. So I'm looking for advice and info on the pitfalls of doing this, as well as any recommendations on a source for decent,economical rigid forks. The Nashbar carbon 26" seems to be about the best option, but again, I'm concerned about lowering the front end too much. I took a brief look at 29" forks, but they were all much more expensive, and before wasting any more time searching the interwebz, I figured I'd better just ask The Matrix.
Any good info is much appreciated......

Measure the axle-to-crown length. This is from the center of the dropout, to the bottom of the lower headset bearing. Your replacement fork just needs to be close, it doesn't have to be exact. You will need to look for one that is 'suspension corrected' meaning it's got the extra length figured in.

The Nashbar Carbon MTB fork has a 385mm Axle-to-crown, and their Cro-mo 26" has a 453mm Axle-to crown. That's a difference of roughly 3 inches, which will affect things like the head angle, BB clearance, and basically rotating your whole riding position forward and down.
The description on the carbon fork states that it's intended for bikes that were originally full rigid, or had short-travel (<80mm) forks.

It also helps to know what you're dealing with other than a '10-year-old Trek' with 26" wheels. Model, pics, or description would help.

+1), the slightly compressed Suspension fork(with you on the bike) gives the frame a designed head tube angle.

it is that head tube height and angle you try to maintain, by finding

a suspension corrected rigid fork, with an appropriate blade length ...

OK, sorry, I didn't think that much detail would be needed. It's a 2007 trek 6000, with Rock Shox Dart.
https://archive.trekbikes.com/us/en/...k/6000/details
I just measure from the bottom of the drop-out to the bottom edge of the headset cup, and it's 19 inches (so, subtract half an inch since I didn't measure from the axle.).
And yeah, I already figured I should probably steer clear (pardon the pun) of the no-name Chi-com forks on ebay.
Thanks again !

Millimeters are a better measurement to use.

Your fork has about 480mm a/c
Subtract 25mm off that measurement for sag and you'll need a fork with about 455mm a/c

453mm a/c:
https://surlybikes.com/parts/forks/1x1_fork
https://www.bikenashbar.com/cycling/...rk-ns-cmf-base

A few mm's more or less won't matter.

I did this when I converted my mountain bike to a cargo bike with an Xtracycle attachment and a rigid fork. It worked perfectly to the point of not needing a single adjustment (including the kickstand) after assembly.

https://cimg6.ibsrv.net/gimg/bikefor...631d8841dc.jpg

Thanks again,guys ! And thanks for those links cobba, that hooks me up !! :thumb:

I have exactly the same bike and also converted to rigid. My fork is not one I'd recommend. There's been a link to surly above, check out their other forks, as well. A few will fit. I recall that salsa has similar offerings in this department IIRC.

Hey, thanks for the reply, but I'm not sure I'm following you. Are you saying you have the same Trek 6000 i have, and used the nashbar fork recommended above, and not to use that one ?

Oh sorry. I have a 2007 Trek 6000. The fork I am using is a Mosso fork (you can find them on ebay). They aren't super bad, but not at a level that I would recommend them to a friend. They flex a little bit much for my taste, I'm not expecting a very long life and am keeping a close eye on.
I have no experience with the nashbar fork. A Surly fork is earmarked as possible future replacement.
Hope this makes more sense.

The Nashbar fork should be a good budget option. Soma MTB 26" forks CrMo 26? MTB Disc Fork | SOMA Fabrications which are advertised as suspension corrected for 100mm travel have axle to crown length of 453 mm, which confirms the calculation.
I did a similar replacement for a Hardrock, but it had 80mm travel, and I needed a different axle to crown length (went with Big Dummy fork).

I have converted 2 mtbs to rigid. 1 was a gt avalanche the best model. it had a 130mm fork. I put a 425mm salsa cromoto disc on it. the 425mm model. it was the shortest they had. it rode like road bike after that. very good comfort in this fork. but it was a little long. The longer the fork gets the more flexy it gets back/forward when braking. also judder.

then my next provect was a chromag sakura. and that was designed round a 150mm or so fork.
i put a 395mm for on it. a surly 1x1 disc. banana shaped, non tapered.
The 395 has no judder and absolutely no flex front/rear. this is as good as it gets imo.
I also built this bike up as a road bike with drop bar. it handles extremely well. low speed stable. (like putting a jacket in your backpack no hands, going up hill. no problem) also very securely feeling at high speed. like 60km/h or so.

I wouldnt put a longer fork than a 425 on any 26er no matter what it came with from the factory. it turns the bikes in to boats.

I have done 2 conversions. and those worked well. they handle just as good as my 2cx bikes and my pure road bike. they feel almost the same. you get used to the handling in a few hours. then its like you never ridden any other bike.

Well damn, it looks like nashbar has removed that fork from their web page (no mention of back-orders or any future return to inventory). But, Carlos makes an interesting point about a long rigid fork "turning the bike into a boat". The low-end Rock Shox currently on it are working fine (as just a fork), and since i don;t really do any off-roading, they might hold up indefinitely. I was mostly thinking here about preventative maintenance for when they do blow up on me. None of this is critical (yet), and I do kinda like having the suspension option, so i may keep an eye out for a deal on a better quality suspension fork.
Anyway, thanks again to all for weighing in.

The thing with suspension forks is that they are not at maximum extension all the time. they are usaully sagged from the start. and then they get shorter when you ride up and down bumps.

so there is no need to look for a very long fork to replace with.
when you go down in millimeters from like 470 to 400 or so, the head angle will become 2-3 degrees steeper. and this is good, this is what you want, and now it works on the road.

All my bikes seems to ended up at 72-73degrees HTA, and the trail is adjustable with rake. there is a trail calculator online. where you can put in whatever values you like. and see what happens.

but its all irrelevant imo. you put on a new fork and ride it. and in like 3-4h it feels like you have never ridden any other bike.

HTA determines the RATE of steering, that is how much input is needed for certain result. and this can also be adjusted with stem length and handlebar length.

trail determines handling. short trail is low speed stable and high speed instable.
long trail is high speed stable and low speed unstable.
in between is a bit of both. or neutral handling!

you will get inbetween by default by getting any available steel fork for your suspension frame. imo.

Bicycle Trail Calculator | yojimg.net

http://upload.wikimedia.org/wikipedi...nsions.svg.png

So why couldn't someone take an existing suspension fork and replace the springs with pipe to make a rigid fork? Back in the day when putting extended forks on MC choppers we'd throw a correct length piece of pipe in when installing longer tubes.