Rigid fork ideas (modern)

[Sketchyxup]

For some time iv been playing with the idea of putting a rigid fork on my HT, iv got a full suss as well so will be doing it fo nothing more than a bit of an experiment really.

I was going to get a carbon one but had some reservations about it because im quite heavy and ride fairly hard, now the carbon would probably be fine but it would probably play on my mind.

My HT is a 2010 Saracen Kili titanuim which has more of a trail geometry rather than an out and out XC race geometry, it is designed for a 120mm fork and currently has a fox F120 on it. Ideally I want to maintain this geometry as I like the way it rides so based on my calculation I would need to run a rigid with an axel to crown of 470mm to do this. That is based on the fox having an a/c of 490mm and running 20mm sag would give me a dynamic a/c of 470.

I was thinking of these as a good subsitute to the carbon ones:
http://www.winstanleysbikes.co.uk/produ ... 29er_Forks? gclid=CMeV6dP1zLcCFSXHtAodQUIAsQ

They seem to be an ideal length and the steel should give a nice ride, finally i like the idea of running a pace fork on a saracen frame for the whole british thing. Those forks cant of been out that long as iv not seen them before and have been pondering this for a while?

Thoughts/ opinions please?

 

[jimplops]

You need to take into account fork sag, I fitted a set of the exotic ally forks ( bought off ajantom ) which you can get off eBay, and have to admit that they're a cracking piece of kit.

 

[suburbanreuben]

Is you bike 26" or 29" wheel?

 

[Sketchyxup]

26" its just a std 2010 kili titanium atm.

 

[Chopper the ex Copper]

Carbon forks won't be a problem. It's hard to find a decent modern road bike that doesn't have carbon forks, and riders of all weights fail to break them. Failure or a metal steered is far far more common than failure of carbon fork blades

 

[suburbanreuben]

Carbon forks won't be a problem. It's hard to find a decent modern road bike that doesn't have carbon forks, and riders of all weights fail to break them. Failure or a metal steered is far far more common than failure of carbon fork blades

THough Pace have a weight limit of 85kg on their carbon forks.
The Pace in the OP's link have an offset of 50mm while 38-41mm is more usual for 26" wheels. This may lead to funky handling...

 

[Osella]

Maintaining the geometry because of 'the way it rides' would surely be a moot point when you put a set of rigid forks on it and... totally change the way it rides.

If it's rigid you might find that a lower front end will be more beneficial as it may allow you to steer around objects you normally run over, or will allow you more room to lift the front over things.

 

[gavinda]

go 29 at the front?!?!

 

[jonnyboy666]

just rebuilt my 2007 clockwork, removed the 100mm travel reba world cup forks (460a-c) as they were dead, replaced them with an Exotic carbon fork (440a-c) feels fine and dandy and looks nice aswel. i'm also about 14 stone, so far from light!

 

[PurpleFrog]

Carbon forks won't be a problem. It's hard to find a decent modern road bike that doesn't have carbon forks, and riders of all weights fail to break them. Failure or a metal steered is far far more common than failure of carbon fork blades

Carbon has great strength per weight and fatigure resistance. The problem for a mountain bike is delamination. This means that after a crash a fork can look fine, but the bonding between layers has weakened and that at some point in the future the fork will suddenly snap, usually while under stress. This is a problem for crit riders too and there is some guidance for diy checking here (I suspect many bike shops will always tell you to buy a new fork, because the legal risk of doing anything else is too high - plus, sell fork = good):

http://www.bikeforums.net/archive/index ... 70450.html

08-10-10, 11:57 AM
If there's no obvious cracking damage showing there's still the issue of internal delamination that is hard to find. Two methods of checking it yourself come to mind. First off hold the fork by the steerer and using a screwdriver handle tap the legs all over and listen to the sound. Taps on each leg in the same place should sound the same. Any sort of drastic change in the sound is likely caused by some delamination. Assuming the fork passes the sound check then I'd move on to a flexing check. For this you need to grip the steerer in some manner that will hold it very firmly. Something like a block of wood with a 1 1/8 hole that is sawn through and then the blocks and fork are clamped to a door frame or in a vise attached to a heavy immovable bench. Once secured I'd flex the legs inwards, outwards, to the front and to the rear. What you're looking for is for both legs to flex equally. If one flexes more than the other then again there's very likely internal delamination. And if it snaps like a dry turkey wishbone then again you have your answer. Don't be gentle with it. You should be using enough pressure to flex the legs by about 1/2 inch to properly simulate the sort of load it'll see on the road. This will be quite a bit of tension and it may be hard for you to do this and still look for even flexing in both legs. So it may help to have a spotter watching and measuring things.

...As BCRider explained there's no reliable way to test. If it were anywhere else on the bike, I'd follow his methodology and make a judgment call, but it's a fork and I hold those to the highest standard

So basically, understand the issues - if you don't really need the weight saving and are an aggressive rider who pushes it and has the odd off, consider staying away from carbon unless you're willing to either chance snaps or replace forks. Otoh if you never crash and are loaded, much more attractive!