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Replace suspension fork with rigid
#1
Hi,

Picked up my dad's 2013 Marin Redwood bike.  I mentioned the bike in another thread, where he wanted the crankset replaced.

Anyway, as I see it, the huge problem with this bike is that it is HEAVY.  For example, the stock tires weigh 2 lbs each (1lb-15.3 oz to be exact).

Before I deal with the crankset, I plan to lighten the bike first.  I have already replaced the seat & seatpost with much lighter versions (approx 1.5 lbs saved).  Ordered new tires and tubes that shave more than 2-lbs off (combined).  Removed the Ergon GP5 fancy grips and replaced with lightweight standard grips -- approx 10oz saved.

NOW I want to replace the cheap suspension fork with a rigid fork.  I know that I need a "suspension-corrected" fork.

PLEASE HELP WITH SUGGESTIONS FOR A LIGHTWEIGHT (and affordable) RIGID FORK, PLEASE.

The measurements & specs:
  • the original fork is Suntour NEX4600 MLO, 63mm
  • I measured approx 450mm axle-to-crown length, measured with the fork locked out and very little sag
  • Headset: FSA, 1-1/8
  • rim brakes (although I am not opposed to a fork with rim+disc brake capability)
  • threadless stem

Lightweight and affordable are my primary interests.  Thanks.
rpesq
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#2
I went with this one for my Green GT:

http://www.amazon.com/Sunlite-Fork-Threadless-Black-Cro-mo/dp/B0013VNDIG/ref=sr_1_28?s=outdoor-recreation&ie=UTF8&qid=1428968997&sr=1-28&keywords=fork+26

Please note: plan on replacing the headset.

I went with this one:
http://www.amazon.com/FSA-141-2340-Hammer-Headset/dp/B003J7XCRO/ref=pd_sim_sg_or_3?ie=UTF8&refRID=15DPJZ1R7MPETG4SXJZW
Nigel
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#3
Hi Nigel,

The 250mm, is that just the top part of the fork? 

I can't seem to find any specs on that fork.  How do you know that it would replace a fork with axle-to-crown of 450mm?  The Sunlite website doesn't give any specs for the fork.

Also, why would the headset need to be replaced?  I don't mind doing that, cost is cheap, but is the old one not compatible?
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#4
(04-14-2015, 01:35 AM)rpesq Wrote:  Hi Nigel,

The 250mm, is that just the top part of the fork? 

I can't seem to find any specs on that fork.  How do you know that it would replace a fork with axle-to-crown of 450mm?  The Sunlite website doesn't give any specs for the fork.

Also, why would the headset need to be replaced?  I don't mind doing that, cost is cheap, but is the old one not compatible?

Not a pro but here;s my 2 cents. The headset, the top part if the fork needs to be the same size as the head set on the suspension fork. Then you need the fork size that fits the size of your wheels so the brakes match up to your wheel rims. Make sure the new fork will take your existing brakes. 
"Where ever we go, there we are"
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#5
And to add a couple more bits.

Headset's crown race needs to match the fork, you did not specify the crown race inner diameter that you currently have....so safest to get a new one that does match - make sure they match before you order, or get the fork and measure.  I lucked out and had a suitable new headset in my stock.  I converted from threaded to threadless at the time.

63mm suspension travel is practically zero, so minimal worries there.

250mm is the length of the steerer above the crown race (approximately).

You will need a new star nut.  You are probably going to need some more spacers too.
Nigel
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#6
Found the info on that Sunlite fork.  It is only 393mm axle-to-crown, which works out to a 2.25in drop from my current setup.  I think that is too much.

I found a Kona Project 2, has 440mm A-C.
Kona Project 2 fork

Not sure if I would need a new headset or not.
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#7
Update:
Thanks to everyone for their initial guidance that helped me to understand what I would be getting into in swapping the fork on this bike.  With the Kona fork, the geometry remains the same, and all I needed to do was to swap the crown race from the old fork onto the new one, and install a new star nut.

I thought that I would follow-up with how my dad's bike project turned out.

Here is a photo:
[Image: marin.jpg]

The changes enabled a grand total of 107.4oz of weight loss, or 6.7 lbs.  That includes adding a Greenfield kickstand (by request).

The biggest weight savings were from the new Kona fork (a full 3 lbs less), then the tires/tubes (2.5 lbs less), and finally the seat & seatpost (1.4 lbs less).

Now I am tweaking my own ride.
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#8
(04-25-2015, 09:26 PM)rpesq Wrote:  Update:
Thanks to everyone for their initial guidance that helped me to understand what I would be getting into in swapping the fork on this bike.  With the Kona fork, the geometry remains the same, and all I needed to do was to swap the crown race from the old fork onto the new one, and install a new star nut.

I thought that I would follow-up with how my dad's bike project turned out.

Here is a photo:
[Image: marin.jpg]

The changes enabled a grand total of 107.4oz of weight loss, or 6.7 lbs.  That includes adding a Greenfield kickstand (by request).

The biggest weight savings were from the new Kona fork (a full 3 lbs less), then the tires/tubes (2.5 lbs less), and finally the seat & seatpost (1.4 lbs less).

Now I am tweaking my own ride.

Very nice job. Looks like it just came new from the factory.
"Where ever we go, there we are"
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#9
Thanks.  I guess with that many new (or gently used) parts, it does look rather new.  I don't think the previous owner rode it much.  Frame and cranks have some minor scratches.

It was probably more effort and money ($150) than was practical for this caliber of bike, but I wanted to bail him out and it was a good learning experience as I had never swapped a fork before.

He still may want the crank replaced, so the project may not be done, but I hope that it is.
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#10
Very Nice job!. Thank you for the update
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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