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light weight rigid fork vs suspension

Old 01-09-21, 06:10 AM
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thehammerdog
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light weight rigid fork vs suspension

my gary fisher wahoo build is coming along nicely. now going 1 x 7 as no desire to spend more to upgrade just yet.
heavy steel fork is beastly but i enjoy how it feels. thus any good lighter rigid options that offer some flex.... Carbon?
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Old 01-09-21, 10:34 AM
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thehammerdog let me contribute some of the conclusions I've arrived at based upon real experience.

First I think your intuition is good in making two true assessments when you wrote "heavy steel fork is beastly but I enjoy how it feels".

1. Steel fork is heavy
2. Steel fork rides enjoyably

Lighter rigid options in carbon and aluminum and composite, titanium, and maybe lighter steel forks exist. And there are options that offer some flex.

Refer back to #2 above, a steel fork does ride enjoyably because it tracks well, feels secure, fits the geometry of the bike as intended (if it's original). Of course the ride is not plush, because it is a rigid fork. My experience is that in general, with notable exceptions, all rigid forks feel rigid, and regardless of the material it's not going to provide something anyone could describe as a plush ride.

Tire choice, bigger tires, are going to provide more practical "compliance" than anything. It is also possible to choose grips and handlebars to help offset the initial hammerblow effect of rigid forks to a small but significantly detectable amount in my experience.

Some old steel forks aren't good looking because the paint is all scratched up. That could be a good reason to replace one with something lighter. Some steel forks are so old and well used that we don't really know how abused they might be. I have crashed very badly riding on an old steel fork that broke in half while I was basically riding downhill on a trail as fast as I could. So I know this does happen. It was on an old Ross bike of which I was the original owner, the fork was a heavy straight tubed 4130 fork. Luckily I was not really hurt much, but had a 15 mile hike out in the dark.

I'd replace a really old fork on a used frame if I planned on riding hard on it.

It's not hard to paint an old fork black. Black goes with everything.

Furthermore, in my experience, the ride feel of a steel fork is pretty much what I now consider, after decades of experiment, the "ne plus ultra" or ideal rigid fork characteristics that I would seek in a replacement fork, be it carbon or whatever. So really it comes down to weight and looks, plus there is the opportunity to tweak the geometry. Also depending, it's a way to get better brakes if you change an old bike to disc (but the wheels too then) which is one of the reasons I have swapped forks on a lot of 26" frames.

In a lot of ways it comes down to weight.

Carbon forks are not all the same. They have different feels, from one to the other, which are huge, and are difficult or impossible to evaluate looking at them. There is a wide range of construction, material, and weights to choose from.

Don't take my opinions as a definitive guide, but here goes.

Carbon steerers are okay and do save a lot of weight but they are critical to the safety of the rider. They take a lot more attention to properly install. Forks with carbon steerers are more expensive.

Carbon drop-outs are okay, even those with QR 100.

However, I do feel more carefree on forks that do not have the expensive attributes of carbon steerers and drop-outs.

Round carbon tubes are generally more flexible than blade shaped tubes. The longer the tubes are, the greater the potential "give". Thereby a longer "suspension corrected rigid fork" might add some perhaps negligible effect.

Another serious consideration is the fork bridge or crown construction area. A lot of carbon forks are bonded, essentially glued together, while others are molded in one piece. I'm not an engineer, so take that into consideration, but it seems to me that both of these methods are valid yet also prone to failure for various reasons. Maybe your choice comes down to aesthetics.

There are different brands out there. Obviously choosing a well known brand is a sensible thing to do.

There a lot more to say about carbon forks (certainly covered in great detail on the web).

My experience dictates that a bladed fork shape while making for a less compliant ride is better because of a phenomenon I call disc brake shudder. Round carbon tubes tend to flex but not snap. When the brake is applied on a steep technical downhill trail the fork does move backwards at he hub, but at a certain point it will not budge and then at a certain place it will rebound. This action does not enhance the ride.

It is possible and possibly likely for a bladed fork to have more side to side flexibility than a wider round tubed fork. You have to take into account the rider's weight. The side to side load is much less then the fore-aft force, so that if the fork is uniformly made, the deflection potential of these axes will correspond differently. That is, the side to side deflection is probably not going to effect the ride negatively, however if the rider is heavy it is possible to detect disc brake rub under certain distortions.

Here I will that if I were north of 200# I wouldn't ride a carbon fork.

So then designers make the fork more robust to make the fork resist this force, and of course it can be done with thicker tubes, better carbon layup etc, but then overall effect is unavoidably less compliant. The result are the high-end offerings in carbon which offer major reductions in weight compared to steel, but offer little in ride improvement over steel.

I have ridden a Kinesis aluminum mountain bike fork with disc brakes for thousands of miles until it bent backwards under hard braking to the point that the front tire nearly rubbed the down tube. It didn't snap, and I rode it home about 12 miles that way. I wouldn't choose an aluminum fork. It bent at the bottom of the steerer tube.

Titanium sounds great but I haven't tried it because it is expensive and I don't want to trust it on the kind of riding I do.

Once I had a Specialized Chisel carbon fork, which had the most unforgiving ride. I weigh 140#. If I were 190# it would've been better. I hated it. I went to a round steel fork and I loved it.

I ride single speed mountain bikes a lot, so that's where all the fork experience comes from.

Steel is better all around for a rigid fork.

I have one bike that I made a 26+ front wheel using a WTB Scraper rim and a 2.8" tire. This wheel in itself creates the best rigid fork ride I've ever had, and if I can get one (it will fit my fork) when it wears out I would get a 3" tire.

Safety is a huge consideration. I do not distrust any of the materials in themselves. You just have to ask yourself and make your choice.

Honestly what are we talking about here/ The weight of a water bottle? In a lot of situations a heavier fork feels more planted on the trail than a light whippy carbon fork. I honestly think for most situations a steel fork is a better choice.
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Old 01-09-21, 11:33 AM
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Originally Posted by Sorcerer View Post
Titanium sounds great but I haven't tried it because it is expensive and I don't want to trust it on the kind of riding I do.
Excellent write-up.

I singled out this statement because I would think the material itself is not suspect, but the design and manufacture may be. It probably also yields the least amount of weight savings over steel. I would think, if done properly, it would be possible to make the ride quality superior, albeit only slightly, but at a tremendous additional cost.

It will be interesting to see if 3D printing will overcome the traditional manufacturing limitations of working with titanium. It will probably always be a boutique market, as carbon is able to provide a cost effective, solution to stiffness/flex and weight.

John
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Old 01-09-21, 05:18 PM
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sorcerer u nailed it

the feeling of control and direct feedback is great on the rigid fork. i get a real sense of connection from bike to trail.
but dam thing is oversized steel kinda size of the 1990's cdale pepperoni fork... but heavy. If i could find one would be great..stem is old school steel quill so heavy front end.

new tires improved ride.
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Old 01-10-21, 07:51 PM
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Nice old bike!

Does the chain stay on? I'd add a cheap chain guide.

Other than that, it's lovely.
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Old 01-11-21, 09:45 AM
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In theory, you might make some small gain in weight and ride quality from a well designed CF fork,

But finding a high quality one for 26 with v-brake/canti bosses could be an issue. Also, is that a 1 or 1-1/8 steer tube?

First place I would start is running bigger tires. It is really a matter of what your fork and brakes will clear. Are those 2.1s?. If so, going up to a 2.4 with appropriate drop in tire pressure will make a world of difference, more than any CF fork will.

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Old 01-13-21, 04:58 PM
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This is for 700c/29er but it gives you an idea of the kind of weight you might really be looking at. 1 lbm = 453.6 grams. The lightest aluminum suspension forks are about 3 lb, barely more than chromoly; and the heaviest are about 6.

There are superlight steel forks that deflect a lot, but they are not appropriate for a mountain bike.

Enve carbon road fork 370 grams
Salsa Waxwing fork (carbon gravel bike) 520 g
531SL fork (one example) 734 g

Surly Cross Check fork 1050 g
Salsa firestarter fork (heavy duty chromoly) 1200 g
RS SID SL (premium XC fork): 1326 g
RS Reba (nice XC fork): 1586-1662
RS Judy Gold (inexpensive but ok): 2009 g
RS Zeb (heavy duty enduro): 2230 g

Marzocchi Bomber Z1 Coil (trail fork) 2,525 g
RS Judy TK (steel stanchions, coil spring) 2545 g
Suntour NEX (coil spring, hydraulic lockout): 2550 g
RS 35 Silver - have not found a listing, but surely north of here
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Old 01-15-21, 01:48 PM
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Originally Posted by Sorcerer View Post
Nice old bike!

Does the chain stay on? I'd add a cheap chain guide.

Other than that, it's lovely.
yes...not sure if SS is going to remain...fun but limiting
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Old 01-15-21, 01:49 PM
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Originally Posted by Sorcerer View Post
Nice old bike!

Does the chain stay on? I'd add a cheap chain guide.

Other than that, it's lovely.
yes...not sure if SS is going to remain...fun but limiting
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