Mountain bike forks

April 1, 2007 6:31 PM

How difficult is it to change suspension forks on a mountain bike to rigid forks?

I have been given a nice mountain bike by my dad, it's brand new. I don't know much about bikes at all, but I know it cost about 300 euro. It's got fat, knobbly tires, which I'm assuming is for "off road" action and it also has some fancy looking suspension on the front fork.

When I'm cycling it on the road, it feels like cycling through treacle. I want to use it on the road for some recreational, keep-fit cycling during the summer. I'd like to replace the knobbly tires with some slicks and replace the suspension fork with a rigid one.

1. Is this actually possible with a 300 euro bike?

2. If so, how difficult would it be for me to do it?

I'm a complete novice at this kind of thing, but I'm good with my hands. I checked out a previous MeFi post about doing this kind thing and those guys seemed to be quite experienced. I am not :)

posted by ReiToei to sports, hobbies, & recreation (11 comments total)

Can you 'lock out' the suspension, effectively creating a rigid fork? Check the top to see if there's a dial. If they're brandless cheapos, this may not be an option.
posted by pullayup at 6:49 PM on April 1, 2007

It can almost certainly be done (to be sure, we'd have to know what kind of bike it is, so let's say 'almost certainly.') But if you're a complete novice at this kind of thing, there's a good chance you don't even have the tools, let alone the expertise, to handle the job safely. And you could buy the tools, but they're not cheap, and considering how often you'll probably use them, you're better off just taking it to a local bike shop.
posted by box at 6:54 PM on April 1, 2007

This is the bike right here. There's no dial on the fork that I can find. There's one under the cross-bar, which I assume stiffens the rear suspension(?).

I'd kind of like to have a go at doing it myself, for curiosity sake, but if there's a chance I could mess it up and wind up in hospital, then I'd most definitely take it to a bike shop.
posted by ReiToei at 7:10 PM on April 1, 2007

Er? The tools for removing/replacing the fork aren't that unusual or expensive. Try dialing them first... almost all suspension forks will let you do that. You should be able to check out a mountain bike repair book from the library that'll detail how to remove the fork - Zinn and the Art of Mountain Bike Maintenance is the book that I have, & I like it quite a bit.

The wheels aren't a problem - look at getting 'hybrid' wheels, which will be smooth on the top with knobs on the sides. They're not ideal for either road or dirt, but they'll let you go over quite a bit more than a roadie would let you do.
posted by devilsbrigade at 7:19 PM on April 1, 2007

The "cycling through treacle" effect is most likely due to the rear suspension, not the front suspension. If that dial does in fact adjust the rear suspension, adjust it as far as it will go and give it a try to see if it is better. There may be some other way to lock out the rear suspension, but it is pretty hard to tell without having a look at the bike. You might have some luck asking at a bike shop. If you can't get the rear suspension adjusted enough to be happy riding the bike, you are out of luck. Used road bikes can be quite cheap.
posted by ssg at 7:44 PM on April 1, 2007

Replacing a fork is possible, but if it's your first time it might give you a headache. You have to remove the crown race which sits on the fork crown, which is a brute force operation unless you get the (expensive) Park tool, or make your own. You also have to cut the head tube on the new fork to the correct length, which is easy, but also easy to do wrong, ruining the fork.

Getting a bike store to do it is a good idea.

However...

1. The bike is going to ride REALLY funny if you do that, though, since the rear suspension will still be active. There is no lockout on that rear suspension.

2. Even the cheapest rigid fork you can get is going to cost you $100 for the fork plus $50 on the install, which is half the cost of the bike more or less.

You'd be MUCH better off saving your pennies for a rigid hybrid.
posted by unSane at 7:46 PM on April 1, 2007

NB you may be able to put stiffer springs in/on both front and back suspension which will firm up the ride. Is it worth it? Probably not.
posted by unSane at 7:47 PM on April 1, 2007

Lots of good advice so far. At the risk of overexplaining, here's my take.

You're on the right track for getting rid of the squishiness. You need to look at your tires and front and rear suspension. You might not be able to get this bike as stiff as you want; so keep that in mind and be prepared to cut your losses by purchasing a decent used road bike.

Tires: IMO you'd be better off with knobless tires for road riding; the narrower the better. Two reasons: the knobs' flexing eats up a lot of energy and narrower tires run at higher pressure meaning a more responsive/less sloppy ride. Switching to a fairly treadless, higher-pressure tire will quell some of that treacle effect - with the higher pressure taking care of more of it. Even if the bike is still floppy with knobless tires, you should be able to go noticeably faster for the same amount of effort.

Look for something like these. Though none are suitable for real off-roading, all of them except the slicks should also give you pretty good traction on the occasional dirt/sand/gravel patch. Somebody else mentioned hybrid tires -- though the theory sounds good I've yet to find one that delivers on the promise (YMMV.)

If you are a total newb, changing your own tires is a good thing to learn. The folks at Park Tool do a good job explaining how. This is their bike repair help guide home page - a really excellent resource. After you've changed the tires, check Sheldon Brown's article on tire pressure to make sure you're pumping 'em up enough -- again, higher pressures here will mean less of a gooey feeling.

Fork: From the picture it looks like your bike has a threaded fork, which would be a big job to replace yourself if you don't have much bike repair experience, and will almost surely end up costing more than a good used bike closer in line with your needs. So probably that isn't your best option. Also it would only take care of part of your problem (the rear is probably as big a part of it.)

Your best bet, as others have said is to try to stiffen the front fork - look for knobs at the top of each stanchion as described here. The site explains the process; the idea is to increase the preload as much as possible. If you can do this, though it won't be anywhere near as stiff as a fixed fork, it might be enough for you to live with.

Rear suspension: This is probably responsible for a lot of the treacle. You definitely want to tighten up the rear suspension, though I'm not sure how you'd do that on your bike (or even if you can.) You want whatever adjustments you make to leave the coil spring surrounding the damper as short/compressed as possible. This will maximize the stiffness (though it may be uncomfortable if you take it off road a lot.) Even if you can't adjust the preload here, a good shop might be able to replace the spring with an ultra stiff one but again it won't be anywhere near as stiff as a hard tail and will cost a few bucks. Get an estimate though; if it's cheap enough it might be worth a shot.

In summary, get skinny/knobless tires and stiffen the front and rear susp as much as you can via whatever preload adjustments you can. If that isn't good enough find out how much stiffer springs would be, but probably you'll find you'd be better off saving for a good used dedicated road bike. Swapping the fork will only solve part of your problem; again, for a similar cost you can get a good used dedicated road bike. Given it's a ~300 euro bike, I wouldn't put any more than 75-100 euros more into it.
posted by Opposite George at 8:49 PM on April 1, 2007 [1 favorite]

Thanks a million for all the great info. I've decided, for the sake of my own sanity and a decent ride, that I might just take the bike into a shop and trade it in/up for proper road hybrid. Again, thanks all for the awesome advice.
posted by ReiToei at 2:36 AM on April 2, 2007

That sounds like a really good decision.
posted by unSane at 5:39 AM on April 2, 2007

Good call. Be sure to do it in a way that doesn't hurt Dad's feelings. Also, now that you know what you don't want in a bike, make sure you take a good ride on each of the ones you try to find one that fits the bill (a couple of circles in the parking lot doesn't count.)
posted by Opposite George at 7:21 AM on April 2, 2007