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fork replacement, need help

Old 11-20-16, 01:34 AM
  #1  
csport
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fork replacement, need help

Hi
I am converting a Hardrock Sport (1999 or 2000) to drop bars since I am using it mostly for commuting/touring. I am thinking of swapping the stock Suntour SR-6200 fork with 80mm travel for some rigid fork like this one:
Nashbar Rigid 26" Mountain Bike Fork
It actually resembles Surly 1x1 fork, only it costs half as much. These forks are ``suspension corrected'' for 100mm travel. Will it make a big difference given that mine is 80mm travel? Assuming 1cm change in the fork length and a wheelbase of 1m, this would amount to roughly 0.5 degree angle, probably not a big deal. My concern is that the default (unsuspended) fork length has changed somewhat in the last 15 years. Thanks for any advice.
I understand that for this conversion I would need to convert to threadless and swap the headset/stem, no problem.

Edit: have done some homework, measured the Suntour fork axle to crown length as specified on Sheldon Brown's site: https://www.sheldonbrown.com/rinard/forklengths.htm
It is about 450mm. Does it mean I am looking for an unsuspended fork with 410-420 mm lengh?

Edit 2: Looking at the Surly fork specs here: https://surlybikes.com/uploads/downlo..._Fork_Info.pdf
Indeed, 1x1 80mm suspension corrected is 413 mm axle to crown. Other ones are much longer, and LHT fork is too short (376mm). The difference between 80mm and 100mm suspension corrected forks is 40mm, not 10mm as I expected (413 vs 453).

Last edited by csport; 11-20-16 at 04:38 AM.
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Old 11-20-16, 08:41 AM
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I think the 413 fork is actually 10mm too short. If you don't mind a slightly more forward leaning position with the same height adjustments of your handlebars, it's probably OK.
Something like a 425mm fork would be more correct in my opinion.

https://www.carboncycles.cc/?s=0&t=12&&q=fork_selector&

I actually swapped my susp. fork out with a rigid one the previous weekend and have been riding my "exotic" 465mm for a week now. I just hope it holds up since it seems a bit fragile with it's thin alu. tubes glued to a rather sleek crown. I am probably worrying too much.

Last edited by Will Wheeler; 11-20-16 at 08:53 AM.
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Old 11-20-16, 08:55 AM
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Forks are generally designed for 25% sag. So, for 450mm currently, subtract 20mm you're looking at a 430 axle crown to match the original geometry.
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Old 11-20-16, 10:30 AM
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rake/offset matters too , its Trail you want to bear in mind, the handling 'feel' geometry comes down to that,
the data, facts on the ground..
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Old 11-20-16, 12:20 PM
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Originally Posted by csport View Post
Hi
I am converting a Hardrock Sport (1999 or 2000) to drop bars since I am using it mostly for commuting/touring. I am thinking of swapping the stock Suntour SR-6200 fork with 80mm travel for some rigid fork like this one:
Nashbar Rigid 26" Mountain Bike Fork
It actually resembles Surly 1x1 fork, only it costs half as much. These forks are ``suspension corrected'' for 100mm travel. Will it make a big difference given that mine is 80mm travel? Assuming 1cm change in the fork length and a wheelbase of 1m, this would amount to roughly 0.5 degree angle, probably not a big deal. My concern is that the default (unsuspended) fork length has changed somewhat in the last 15 years. Thanks for any advice.
I understand that for this conversion I would need to convert to threadless and swap the headset/stem, no problem.

Edit: have done some homework, measured the Suntour fork axle to crown length as specified on Sheldon Brown's site: Fork Lengths by Damon Rinard
It is about 450mm. Does it mean I am looking for an unsuspended fork with 410-420 mm lengh?

Edit 2: Looking at the Surly fork specs here: https://surlybikes.com/uploads/downlo..._Fork_Info.pdf
Indeed, 1x1 80mm suspension corrected is 413 mm axle to crown. Other ones are much longer, and LHT fork is too short (376mm). The difference between 80mm and 100mm suspension corrected forks is 40mm, not 10mm as I expected (413 vs 453).
Well, oddly enough, I can give you first hand advice! I have an early 2000s Hardrock that came with the 80mm Suntour fork. I also happen to have the Nashbar rigid fork you linked to. The Nashbar fork had been on a previous bike and I just had it sitting around. When I picked up the Hardrock, I too wanted to replace the worn out suspension fork. I Switched out to give the Nashbar a try and..... it's definitely too long! The general steering and "feel" of the bike was way off with all the extra axle to crown length. I have in the past changed forks on other bikes that were off a little as far as length and rake are concerned, and gotten away with it, adapting to the change pretty quickly. Unfortunately, the Nashbar is just not close enough to the original Suntour.

If I were you I would keep looking and not consider the Nashbar at all.
Bruce
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Old 11-21-16, 05:29 AM
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Originally Posted by Will Wheeler View Post
I think the 413 fork is actually 10mm too short. If you don't mind a slightly more forward leaning position with the same height adjustments of your handlebars, it's probably OK.
Something like a 425mm fork would be more correct in my opinion.

https://www.carboncycles.cc/?s=0&t=12&&q=fork_selector&

I actually swapped my susp. fork out with a rigid one the previous weekend and have been riding my "exotic" 465mm for a week now. I just hope it holds up since it seems a bit fragile with it's thin alu. tubes glued to a rather sleek crown. I am probably worrying too much.
Probably these guys are too weak for me, especially with the load

Originally Posted by gsa103 View Post
Forks are generally designed for 25% sag. So, for 450mm currently, subtract 20mm you're looking at a 430 axle crown to match the original geometry.
Thanks! I am looking for a steel fork as I am a heavy rider and I want to use the bike for loaded touring. All I was able to find so far are the 413mm (Surly 1x1 80mm) and 453mm (Nashbar or Surly 1x1 100mm) forks. In between them are Kona Project Two (440mm) and a 430mm Origin 8 fork (actually a 29-er fork, will not work with the rim brakes on 26 inch wheels). Will keep looking.
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Old 11-21-16, 05:52 AM
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Originally Posted by sarahbruce View Post
I Switched out to give the Nashbar a try and..... it's definitely too long! The general steering and "feel" of the bike was way off with all the extra axle to crown length.
Hi Bruce, thanks for sharing your experience. Was the steering too difficult and unresponsive with the Nashbar fork?
The best I have found so far are Surly 1x1 (413mm) and Kona P2 (440mm). May need to keep looking...
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Old 11-21-16, 06:28 AM
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Originally Posted by csport View Post
Hi Bruce, thanks for sharing your experience. Was the steering too difficult and unresponsive with the Nashbar fork?
The best I have found so far are Surly 1x1 (413mm) and Kona P2 (440mm). May need to keep looking...
I wouldn't really call it "too difficult and unresponsive" but it just didn't feel "right".

The only other option I see is the Surly Big Dummy fork. It looks to be about the right size, and it's pretty cool how many mounts it has, making it appropriate for touring. The negatives being- It's heavy and probably pretty stiff, and $110.

If I were you and really was set on using the Hardrock. I would probably go with the Big Dummy fork and run wide tires to make up for the stiffness of the frame and fork.
Bruce

PS: You should post some pics of the bike! ( No specific reasons, I just like threads with pics)
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Old 11-21-16, 07:31 AM
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csport
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Originally Posted by sarahbruce View Post
If I were you and really was set on using the Hardrock. I would probably go with the Big Dummy fork and run wide tires to make up for the stiffness of the frame and fork.
Bruce

PS: You should post some pics of the bike! ( No specific reasons, I just like threads with pics)
Definitely, here is a picture from September:



For now it is OK for me. The tires here are Marathon Plus Tour 2.0 or 1.9 inches wide.
Even with the Big dummy fork this bike will be cheaper than the bare LHT frame
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Old 11-21-16, 07:47 AM
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Originally Posted by csport View Post

For now it is OK for me. The tires here are Marathon Plus Tour 2.0 or 1.9 inches wide.
Even with the Big dummy fork this bike will be cheaper than the bare LHT frame
Man that looks great! I would absolutely put a Big Dummy fork on there and a good quality front rack to distribute the weight of your stuff. It would be a bombproof commuter/tourer/utility bike.
Bruce
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Old 11-21-16, 08:38 AM
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csport, have you ever considered converting to disc brakes on the front? There will be a lot more options for you with all the 700 forks out there in all kinds of lengths and materials, and possibly cheaper than getting a 26" which seems to be pretty rare unfortunately.
Having a proper front brake is nice to have anyway...
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Old 12-14-16, 06:03 PM
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Originally Posted by sarahbruce View Post
I would absolutely put a Big Dummy fork on there
Got the Big Dummy fork from a LBS on Black Friday with 30% off. Took some time for it to arrive. Installed FSA mallet headset, Promax drop bars and Shimano bar end shifters. So far rides great.

Thanks for the help!
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Old 12-14-16, 06:10 PM
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I'm diggin' it! Looks good on there.
Bruce
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