Question re: Forks

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Question re: Forks

Postby rich100 » 26 Sep 2012, 12:05pm

Thinking of buying a frame to make up into a bike for the other half.

If I was to buy a second hand frame minus the forks, what considerations are there for getting a set forks apart from the following?:

Steerer dimensions, ie 1 1/8th inch, and suitable steerer length for the headset and stem etc
threaded or ahead
dropouts, would be standard 100mm I guess
Brake mounts to match the rear, ie canti

Are forks of a standard length, so would be ok so long as set up for 700c not 27 or 26 inch?

Is it best to match steel type with the frame? (Although I'm sure my Panorama forks are not 725 like the frame).

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Re: Question re: Forks

Postby NUKe » 26 Sep 2012, 12:11pm

The only thing I can think of was the frame designed for a suspension fork(MTB/ATB), otherwise they are fairly standard.
Why does the frame not have forks would be my question to the vendor though. If accident damage then the frame needs a carefull check

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Re: Question re: Forks

Postby rich100 » 26 Sep 2012, 12:55pm

It's a touring frame so no suspension to think of on this model.

I take your point about potential damage, the one I saw which raised the question in my mind is on ebay, old stock sold by a shop so presumably forks are missing in action - but a worthwhile question none the less.


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Re: Question re: Forks

Postby stewartpratt » 26 Sep 2012, 1:11pm

Axle-crown lengths do vary a little. With canti brakes this is rather less of an issue since the length doesn't affect the brake mounting position as it does with calipers, but you will still see some variation. In reality, though, it's unlikely to be enough to significantly affect the geometry of the bike and any 700c canti fork will do the job.

Other than that I think you have it covered: they'll all be 100mm and have the brake bosses in the same place so it's simply a case of getting one with the appropriate steerer dimensions. (And making sure they have mudguard eyelets and/or lowrider bosses if you need those.) No need to worry about the steel type, at least assuming you get some flavour of cromoly rather than cheap hi-ten stuff.

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Re: Question re: Forks

Postby Brucey » 26 Sep 2012, 1:14pm

length varies with wheel size, 'suspension correction', mudguard clearance etc.

Obviously canti-boss height varies with intended wheel size, but also check canti-boss spacing. They are mostly the same in this respect but there are no guarantees.

Other parameters include;

-Crown race fitting dimension- should be standard... but....
-offset (should be matched to head angle for desired trail setting)
-blade shape
-blade tubing gauge
-lawyer's lips
-axle slot width; (mostly 10mm these days but check)
-axle slot orientation; can be vertical, in line with the steerer, or in line with a curved fork tip
-'flange clearance' (i.e. how far the fork blades protrude inwards from 100mm- can affect running clearance with some hubs and wheels)
-'carrier clearance' how much the fork blade tips poke outwards sideways- thus how they interfere with a front carrier.
-mudguard eyes
-carrier eyes on dropout
-carrier eyes on fork blade
-eye threading- usually M5x0.8mm but this can vary, some bikes have plain eyes and some are threaded M6x1.0mm.
-crown drilling ; hole dia and position.
-breather holes in fork blades
-TIG /MIG/ Brazed etc construction
-steerer; internal butting (if there; if so, how thick and how long? )

obviously some of these things are more important than others, but even some of the less important ones can be more than a little irritating if you get them wrong.



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Re: Question re: Forks

Postby deliquium » 26 Sep 2012, 1:15pm

Also consideration to the size of tyres and mudguards re the width of the fork crown and hence gap between fork blades in that area.
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