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Old 05-23-08, 05:04 AM   #1
CornwallJon
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Replacing Manitou suspension forks

Hi all,

I have a 1999 Klein Attitude Comp which came with Manitou SX suspension forks. For some years now, there's been something wrong with the forks and they won't lock out - a couple of mechanics have had a look and say they need a part which is hard to come by for various reasons. I am thinking of replacing the Manitous for non-suspension forks to make the bike lighter (though a couple of people have recommended that I will regret doing this!). The Klein uses a 1 1/8 inch headset. So my questions are:

1. Is it wise to replace the suspension forks to make the bike lighter?
2. Is it easy to do myself? I'd probably want to stick with the existing rim brakes.
3. Can I buy any forks to fit a 1 1/8 inch headset (I am guessing this is a standard size?)
4. Are some forks better than others in terms of lightness/responsiveness? I guess I want something with a bit of flex, although the majority of my riding is on roads or paths rather than proper off-road.

Thanks!
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Old 05-23-08, 05:35 AM   #2
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1. It's your call. Cheap, Light, Durable - - pick any two
2. It can be done by a home mechanic. Check out the Park Tools web site for advise there. I might suggest looking at your headset while you have it apart.
3. That is a standard size found most commonly.
4. You should be able to go with a mid level fork. Lock-out is hardly necessary on the bike the way you ride it so you can save some money there.
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Old 05-23-08, 05:51 AM   #3
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If you're not doing any rough off road riding then rigid forks will be fine. There's a number of nice options out that range from inexpensive to ghastly. For the most part almost any of them will work but if you want to maintain the present handling feel of the bike you'll want to match the fork leg length to your present forks.

One little detail to check though. When you're riding your weight slightly compresses the fork. So to get an accurate leg length what you want to do is measure the at rest length from the axle to the top of the crown where the lower headset is seated and then subtract the sag you have when you're riding the bike. To check that sag amount put a zip tie onto the stanchion tube so it's loose enough to move but will stay in place. Slide the tie down to the fork leg seal (take off the gator if you have them) and then ease yourself onto the bike and go for a 50 yard ride with no bouncing or pot holes. The sag during the ride will push the tie up a little. Measure that distance and subtract it from the full extension leg length. Now go shopping for a fork that lists that result as the axle to crown dimension or close to it.

If buying used be sure you get one that lists the steer tube as being at least as long as your steer tube is. Otherwise you won't be able to set up the stem and spacers the same as you have now. With a new fork this won't be an issue but you'll need to measure and cut the steer tube to match your present fork.

As you suspect the final spec you need to get is the 1 1/8 steer tube size.

On ebay right now there's a lot of inexpensive Chinese made carbon rigid forks for mountain bikes. They come in both disc and rim options. If money is no object and you want what many have reported to be the best then check out the Pace RC-30 forks. Carbon tube legs and aluminium fittings.

There's also some other aluminium and steel options that show up on ebay. With steel having a reputation as being more springy and shock absorbing you may want to stick with steel as an option. There is still some tapered and even butted tube steel forks available that would have been upscale back in the day. Again they will be more expensive but may suit your needs more.

Some of the various online stores have rigid forks. I know that www.webcyclery.com has a good selection and www.jensonusa.com has a decent assortment as well.
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Old 05-23-08, 08:12 AM   #4
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Quote:
Originally Posted by CornwallJon View Post
I have a 1999 Klein Attitude Comp which came with Manitou SX suspension forks. ..I am thinking of replacing the Manitous for non-suspension fork

1. Is it wise to replace the suspension forks to make the bike lighter?
There is more than the bike's weight that will change if you replace a sus fork with a rigid fork. But if you haven't got any issues with wrists, hands and shoulders, mostly ride fairly smooth surfaces and/or mainly short courses then you are likely to appreciate the increased responsiveness of a bike with a rigid fork.

Quote:
Originally Posted by CornwallJon View Post
2. Is it easy to do myself? I'd probably want to stick with the existing rim brakes.
Well, you shouldn't have any phobias about tools or getting greasy...
But yeah, it's fairly easy. Getting the crown race off the old fork and on to the new, seating the star nut and cutting the steerer requires a modest amount of skill.
Tools, and access to some stuff to improvise tools of (a vacuum cleaner pipe is often very handy to seat the crown race with), as well as a workbench and a vise makes it all a lot easier. It's not something I'd like to tackle in an apartment using only a Swiss Army knife...

Quote:
Originally Posted by CornwallJon View Post
3. Can I buy any forks to fit a 1 1/8 inch headset (I am guessing this is a standard size?)
Yes, no, maybe. The 1 1/8 is a very common size, although not the only one. Odds are good but you still have to check.
However there are more to forks than steerer diameter. Steerer length for instance is really important if you're buying a used fork that's already been cut.
Another measurement that is might be important to you is the axle-to-crown measurement.
I've never found the difference to be big enough to make the bike unrideable, but if you want to retain as much as possible of the current handling characteristics you need to find a fork whose axle-to-crown measurement is as close to what you have now, when you're on the bike.
Then of course you need to make sure that the fork has fittings for the brakes you plan to use.

Quote:
Originally Posted by CornwallJon View Post
4. Are some forks better than others in terms of lightness/responsiveness?
Sure, CR-Mo forks tends to be cheapest and heaviest, while aluminum forks are lighter and more expensive. Both will be lighter than your sus fork though. Haven't seen rigid CF forks for MTB in a while, but wouldn't surprise me if they're still around somewhere. My guess is that they would be continue the trend by being even lighter and even more expensive.
Might look financially lopsided to stick such a fork on an old bike.


Quote:
Originally Posted by CornwallJon View Post
I guess I want something with a bit of flex, although the majority of my riding is on roads or paths rather than proper off-road.
Every now and then you come across people who'll claim that CF has near-magical properties when it comes to damping road buzz, while others will tell you with equal fervour that it's all in the design rather than in the material itself. Either way it's not something that can be easily judged by looking or measuring for that matter.
Tire size and pressure is likely to have a greater influence on ride quality than the choice of fork, but opinions runs high on this matter.

If you really want a bit of flex you might look at changing to a nicer XC fork instead, fitting a flexing stem or simply run rather wide tires.
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