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Replacing suspesnion forks for rigid with 700c wheels

_Brun__Brun_ Posts: 1,740
edited May 2018 in MTB workshop & tech
Err, wasn't sure where to post this, suspension presumably being a dirty word in the road section, and 700c likewise over here. Guess that's what you get for buying a hybrid. :oops:

Anyway, I thought this would be a previously discussed topic but despite searching I've not found any relevant threads. What I'm hoping to do is replace the front sus forks on my 2007 Scott Sportster P4 with rigid ones, reason being that the lockout seems stuck and rather than get them repaired I fancy a rigid fork since it's pretty much a commuting bike.

Reason I'm after advice here is that I'm struggling to find a suitable suspension corrected fork with v-brake mounts for 700c wheels. I've measured the axle-crown length at 450mm, but as the forks are currently stuck, I'm not sure whether I should knock off a few mm for 'sag' when looking for a replacement. I've emailed both Scott and Suntour to try find the correct A-C but so far no reply. Suntour specify the travel at 63mm by the way, although Scott reckon it's 50mm.

Surly do a 700c cyclo cross fork at 400mm, which my calculations reckon will change the head angle from 71 to approx. 73.5 degrees and drop the bb about 20mm. These figures don't sound excessive but I've honestly no idea what effect they will have on the handling.

The other (rather more expensive) option looks like the Kinesis X MAX which is disc only, but with optional v-brake mounts which can presumably be located to fit 700c rims. Again, I can't find the A-C length (it's not on their website and I've had no reply via email) but it's apparently corrected for 100mm travel so could be too long.

That's all become very long winded, so you can probably guess I'm rather confused by it all. Any help or advice would therefore be very much appreciated, cheers.

B

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    TBH the easiest way will be disc hubs and 700c rims as i can not think of any suitable forks with V mounts for 700c rims and sus corrected.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
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  • SplasherSplasher Posts: 1,528
    Kona do a 700c P2 with V-bosses. You'll need to search out a stockist but you can see the product on the Kona US site here http://content.konaworld.com/webstore/i ... gory_id=25

    Click the drop down box and select "700c rim only."
    "Internet Forums - an amazing world where outright falsehoods become cyber-facts with a few witty key taps and a carefully placed emoticon."
  • _Brun__Brun_ Posts: 1,740
    Cheers for the replies.

    I'd considered disks but was hoping to avoid the cost and complexity. Besides, seeing as I'm trying to simplify the bike into a commuter/tourer, adding a front disc seems a bit counter productive. If and when Kinesis get back to me about the length of their rigid fork I may go down that route, despite it also costing more then I was originally intending. Does look nice tho' :)

    Splasher, I'd seen the Kona forks already but it looks like the 700c version is only 390mm axle to crown which is too short.
  • SplasherSplasher Posts: 1,528
    I don't think it is too short. It does steepen up your steering, but not that much and effectively converts your sportster to a speedster:

    79b88X8J9EvP6N82srS194B9CO6n8tH5.jpg

    The sportster has a head angle of 69 - 72 degrees depending on the frame size and the speedster has a head angle of 70.5 - 73.3 depending on the frame size.
    "Internet Forums - an amazing world where outright falsehoods become cyber-facts with a few witty key taps and a carefully placed emoticon."
  • _Brun__Brun_ Posts: 1,740
    Yeah that makes sense Splasher, I stand corrected.

    According to the specs on Scott's site, the head tube length is 170mm on the Speedster vs 140mm on my Sportster, so the 400mm Surly fork I mentioned in the top post could be a decent fit. I reckoned that steepens the head angle to about 73.5 degrees which doesn't sound unreasonable given the figures you quoted.
  • SplasherSplasher Posts: 1,528
    You always take a bit of a risk when you mess with your bikes geometry but as long as it's a calculated risk it normall works out. Here's what we did to my wifes MTB when she entered a dualthlon. It normally runs a 100mm Reba so the head dropped 100mm and whilst it's mad looking (mainly because of the 13" frame and the 700c wheels) it was pounds lighter and much faster and handled like a road bike.

    2532864995_856b05019d.jpg

    One other thing, don't be too quick to cut the steerer tube. This is for 2 reasons, first, you may want your bars higher up to compensate slightly in your riding position. And secondly, if you try it and you decide it wasn't the right thing to do, it's a lot easier to sell a fork with an uncut steerer.
    "Internet Forums - an amazing world where outright falsehoods become cyber-facts with a few witty key taps and a carefully placed emoticon."
  • _Brun__Brun_ Posts: 1,740
    Job done :)

    No real need to bump this thread other to say thanks again for the help and post evidence of the finished article...

    CIMG1017_small.jpg

    Went with the Surly CC fork which I've had since Monday but decided to wait till the weekend before doing owt to make sure I didn't rush it and balls stuff up. Fork crown race was being a stubborn censored but that was sorted by the very helpful folk at Highbury Cycle Surgery who installed free of charge while I grabbed some lunch. The adjustable stem caused me a bit of confusion, hadn't seen anything like that when reading up on the net.

    Having picked up the old forks when removing them, it's no surprise that the bike now feels a lot lighter. Very noticeable change in weight distribution too. Reckon the front end is about an inch lower than previously, but to be honest I couldn't tell the difference from the saddle. Steering is definitely quicker tho', which could take a few miles to get used to.

    Will save a lengthier test ride till tomorrow, right now it's time to kick back with a beer and watch some football.
  • ksisksis Posts: 2
    Hi

    how did the bike go after the fork replacement ?

    I am thinking about doing the same on a ktm life one 2012 i have

    but the change seems big in numbers

    i calculate

    a change of trail from 79.38 to 51.7mm
    for flop from 24.97 to 13.3 mm

    and a 3 cm drop of the bottom bracket.

    if i change the Suntour fork to Surly Cross Check
  • JBAJBA Posts: 2,772
    Great thread resurrection!
    It has been dormant for over 9 years and the OP hasn't posted since 2012 so I doubt he'll answer.
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • ksisksis Posts: 2
    yeah thought it would be funny to wake thisone up
  • nick67nick67 Posts: 111
    I appreciate this is an old thread, but am looking to do the same thing for a Scott Sportster P2. My wife has got into cycling a little bit so is using my old Scott, but would prefer a lighter front hence the exercise.

    Any guidance much appreciated
  • The RookieThe Rookie Posts: 27,748
    Have a look at Mosso forks on ebay, check the A2C (Axle to Crown) height matches the current with +0 to -20mm and that it has the right brake mounts for whichever brake your P2 has (rim or disc).
  • nick67nick67 Posts: 111
    The Rookie wrote:
    Have a look at Mosso forks on ebay, check the A2C (Axle to Crown) height matches the current with +0 to -20mm and that it has the right brake mounts for whichever brake your P2 has (rim or disc).

    Thanks for this pointer, I might invest the money into a new bike as my son is also keen to cycle in the summer holidays
  • figbatfigbat Posts: 680
    Out of intr st, what is keeping that fork in place in the picture? There appear to be no spacers beneath the stem and no locknut for a threaded stem. I’m hoping to do a MTB project with rigid fork and 700c/29er wheel.
    Cube Reaction GTC Pro 29 for the lumpy stuff
    Cannondale Synapse alloy with 'guards for the winter roads
    Fuji Altamira 2.7 for the summer roads
    Trek 830 Mountain Track frame turned into a gravel bike - for anywhere & everywhere
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