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FourMat
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Old Hard Rock Fork Conversion ??'s
06/25/13 at 6:00pm
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I was able to scavenge an old Specialized Hard Rock Sport steel frame (looks like a '95) that's in really great shape.  It's missing the fork, and uses a 1" steerer.  I was considering turning it into a rigid 69'r, slapping some cross or narrow tires on it and using it as rail trail gravel psuedo time trial bike for the New River Trail Triathlon.  Kind of a fun frankenstein with drop bars or TT bars.  I've got lots of spare parts to mix and match with.

The big thing that I'm stuck on is that I can't find a 29'r/700c threadless fork with a 1" steerer and disc caliper mounts....  Anyone have any idea where I might find something like that, or other suggestions for options?  Am I SOL when it comes to bearings/cups to go with it also?
« Last Edit: 06/25/13 at 6:09pm by FourMat »  
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Captain Awesome
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Re: Old Hard Rock Fork Conversion ??'s
Reply #1 - 06/25/13 at 8:07pm
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FourMat wrote on 06/25/13 at 6:00pm:
I was able to scavenge an old Specialized Hard Rock Sport steel frame (looks like a '95) that's in really great shape.  It's missing the fork, and uses a 1" steerer.  I was considering turning it into a rigid 69'r, slapping some cross or narrow tires on it and using it as rail trail gravel psuedo time trial bike for the New River Trail Triathlon.  Kind of a fun frankenstein with drop bars or TT bars.  I've got lots of spare parts to mix and match with.

The big thing that I'm stuck on is that I can't find a 29'r/700c threadless fork with a 1" steerer and disc caliper mounts....  Anyone have any idea where I might find something like that, or other suggestions for options?  Am I SOL when it comes to bearings/cups to go with it also?



So you want to intentionally stick with the 1" steerer or are you just not wanting to go thru trying to find the right bearings to fit a 1 1/8 fork up in there?


I put an old 1 1/8 Rock Shox Judy on my Schwinn Heavy Duti frame and even had a 120mm travel SR on it for awhile. Coaster brake/suspension fork/twin top tube Franken-cruiser. Finding the right bearings to make it all fit up tight just required me scavenging thru old parts bins until i found the right set


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stateprez
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Re: Old Hard Rock Fork Conversion ??'s
Reply #2 - 06/25/13 at 8:44pm
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You're probably going to have to find a 1" cross fork with disc tabs.  You won't be able to run a 29er mountain tire though since it will be too narrow.

Even if you did get it to work, it will probably steer like crap due to the frankenstein head angle and fork rake.  I do encourage all frankenbike attempts.

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Captain Awesome wrote on 06/25/13 at 8:07pm:



So you want to intentionally stick with the 1" steerer or are you just not wanting to go thru trying to find the right bearings to fit a 1 1/8 fork up in there?


I put an old 1 1/8 Rock Shox Judy on my Schwinn Heavy Duti frame and even had a 120mm travel SR on it for awhile. Coaster brake/suspension fork/twin top tube Franken-cruiser. Finding the right bearings to make it all fit up tight just required me scavenging thru old parts bins until i found the right set


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BMX and Cruiser 1" is a different standard than 1" mountain/road.  You would have to get your headtube reamed for a mountain 1" to work with a 1-1/8 fork.

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« Last Edit: 06/25/13 at 8:51pm by stateprez »  
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Re: Old Hard Rock Fork Conversion ??'s
Reply #3 - 06/25/13 at 9:54pm
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stateprez wrote on 06/25/13 at 8:44pm:
You're probably going to have to find a 1" cross fork with disc tabs.  You won't be able to run a 29er mountain tire though since it will be too narrow.

Even if you did get it to work, it will probably steer like crap due to the frankenstein head angle and fork rake.  I do encourage all frankenbike attempts.

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BMX and Cruiser 1" is a different standard than 1" mountain/road.  You would have to get your headtube reamed for a mountain 1" to work with a 1-1/8 fork.

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I just threw a caliper on my old GT frame and its 1" headtube measures 30.2 id so I can only assume a 28.6 shaft will fit. Obviously its a crap shoot on bearings and cups, but I encourage one to try.
  
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Re: Old Hard Rock Fork Conversion ??'s
Reply #4 - 06/25/13 at 10:10pm
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Get an old steel, 1" steer tube road fork and throw a set of hybrid 700x28 tires on it.  Use a 26 in the back if you want rear brakes. Smiley
  
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FourMat
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Re: Old Hard Rock Fork Conversion ??'s
Reply #5 - 06/26/13 at 2:39am
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Thanks guys.  stateprez, I missed finding that one on your google link.  Looks like a good inexpensive alternative.  I also found a carbon cross fork with 1" steerer on Nashbar for $119.

I guess the next question is the bearings and cups.  I measured the ID of the head tube and it's exactly 30mm.  I'm looking at 1" threadless headsets and the ones I can find have a 26.4mm race diameter.  Is the ID of the head tube also called the race diameter?  Do I need to find a set with a 30mm race diameter?

As far as the steering goes, I'm not really worried about the handling.  I would assume that the really weird head angle (more caster) would make it more stable in a straight line, which is what I'm looking for with the frankenstein TT build.
  
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Re: Old Hard Rock Fork Conversion ??'s
Reply #6 - 06/26/13 at 3:41am
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FourMat wrote on 06/26/13 at 2:39am:
Thanks guys.  stateprez, I missed finding that one on your google link.  Looks like a good inexpensive alternative.  I also found a carbon cross fork with 1" steerer on Nashbar for $119.

I guess the next question is the bearings and cups.  I measured the ID of the head tube and it's exactly 30mm.  I'm looking at 1" threadless headsets and the ones I can find have a 26.4mm race diameter.  Is the ID of the head tube also called the race diameter?  Do I need to find a set with a 30mm race diameter?

As far as the steering goes, I'm not really worried about the handling.  I would assume that the really weird head angle (more caster) would make it more stable in a straight line, which is what I'm looking for with the frankenstein TT build.

If you look at the Sheldon Brown Chart, 1" ISO has a 26.4 crown race ID.  The OD of the cups is 30.2. You should be fine.

Hypothetically it would be better in a straight line (like a Cadillac), but turn in will suffer (sluggish). Difference between a 29er and a 26er A-C is 30mm, and probably 1.5 deg HTA.   A cross fork (non-suspension corrected/shorter) will probably be as close as you can get to perfect.  

Captain Awesome wrote on 06/25/13 at 9:54pm:



I just threw a caliper on my old GT frame and its 1" headtube measures 30.2 id so I can only assume a 28.6 shaft will fit. Obviously its a crap shoot on bearings and cups, but I encourage one to try.

That leaves 1.6mm for bearings and cups.  If you look at the chart, all of the headset/steerer dimensions leave 4mm+ for the headset.  If you can trim 2.5 mm from the ID of your headtube, maybe it will work.  


« Last Edit: 06/26/13 at 3:42am by stateprez »  
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Re: Old Hard Rock Fork Conversion ??'s
Reply #7 - 06/26/13 at 11:44am
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stateprez wrote on 06/26/13 at 3:41am:

That leaves 1.6mm for bearings and cups.  If you look at the chart, all of the headset/steerer dimensions leave 4mm+ for the headset.  If you can trim 2.5 mm from the ID of your headtube, maybe it will work.  



It DOES work. Bolted that fork into that GT frame last night after going thru about a dozen sets of generic bearings and cups to find the right setup. Not perfect, but it's tight


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It's a mongoloid setup no doubt with some old no name (Walmart bike probably) cups and mix and match bearings from the parts bin, but lot's of people do it. Depending on the age of the frame it's worth a shot for anyone wanting to do it.


« Last Edit: 06/26/13 at 11:54am by Captain Awesome »  
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Re: Old Hard Rock Fork Conversion ??'s
Reply #8 - 06/26/13 at 12:48pm
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Some pics or details on what you used would probably be more helpful than an Anchorman meme.

Were you able to press a 1-1/8" headset into a 1" frame?  Did you use a 1" headset with 1-1/8" bearings?  ETC?
  
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FourMat
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Re: Old Hard Rock Fork Conversion ??'s
Reply #9 - 06/28/13 at 2:20am
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Ok got some parts on order.  I'll post photos and updates of the frankenbuild.  Should be a fun project.
  
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Re: Old Hard Rock Fork Conversion ??'s
Reply #10 - 07/11/13 at 2:19pm
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Ok, got the parts in and I'm ready for the next step.  I need to decide what front brake to put on this thing.  I was thinking about putting a 28 or 38 on one of my disc brake MTB wheels and running that.  both I have are 185mm rotors.  I have the cross fork with disc caliper mounts.  I was going to try to go for a mechanical caliper like a BB7 or BB5 but the only sizes that I've seen are for 160mm or 180mm.  Is the only difference between the setups, just the size of the spacer?

I haven't build up a caliper setup before, so if I got a 180mm setup, could I just space it out 5mm to run the 185mm rotor?

Anyone got an old BB5 or BB7 front caliper lying around they'd like to get rid of?

I'm also looking for a 32h front disc hub.  I have a spare rim that I might try to lace up if I can keep the cost down.
  
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