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Pedals to low , is there any way to extend front forks ?

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    Pedals to low , is there any way to extend front forks ?

    Hi first post. Here is my bike build. I have run into some problems , I added 20 “ fat tyres (it originally had 26” tires. I added smaller crank arms. But the pedals are still to near the ground
    Last edited by Del15476; 07-14-2018, 04:22 PM.

    #2
    The front forks are bent when I bought it so I want to add suspension forks. Is there any way to raise the fork higher ? To raise the bike. Not handle bar raiser but a way to raise the fork stem ? Thanks

    Comment


      #3
      If the front fork is bent at all, you need to replace the fork. That fork is 100% knackered. You absolutely cannot have a fork offset (rake) in that direction.

      I just bought some new Surly forks. They were about $150 each.

      As for raising the front end, headset spacers are not designed to work below the head tube. I have included exploded views of headsets with both sealed cartridge and cage bearings. I'm sure your headset has sealed cartridge bearings. Headset spacers go between the seal (marked Tange Seiki) and top cap in the first diagram.

      Proper head set installation is a critical safety issue, particularly for the rider, as is front hub installation. If these parts fail, you go over the handlbars at the speed you were travelling.

      If you cannot make it work with short crank arms, you need to put back on the 26" tires. Going to a larger diameter tire is the best way to raise a bike.

      Click image for larger version  Name:	21f6b66dc7d37adca7102d2f8938f5dd.jpg Views:	1 Size:	52.6 KB ID:	69310Click image for larger version  Name:	Bicycle_headset_exploded_view-en.png Views:	1 Size:	338.3 KB ID:	69311
      Last edited by commuter ebikes; 07-14-2018, 08:05 PM.

      Comment


        #4
        “””If the front fork is bent at all, you need to replace the fork.”””

        Comment


          #5
          Hi buddy I did say I am replacing the fork with suspension fork As for raising the the forks you where right that’s wat I was hoping I could do add spacers at the bottom of the cup to raise the bike , will suspension forks not raise the front end a bit ? Ta

          Comment


            #6
            Originally posted by Del15476 View Post
            Hi buddy I did say I am replacing the fork with suspension fork As for raising the the forks you where right that’s wat I was hoping I could do add spacers at the bottom of the cup to raise the bike , will suspension forks not raise the front end a bit ? Ta
            Good that you are getting a new fork so that you will have a nice long uncut steer tube to work with.

            You can make a custom spacer with the same dimensions (on both ends!) as the bottom of your head tube (which appears in your photos to accept an EC44 headset) such as the one 2/3 of the way down this article: http://www.ransbikes.com/library/int...ticles/itr064/

            Here is a picture:

            Click image for larger version  Name:	Spacer2.jpg Views:	1 Size:	39.0 KB ID:	69316

            For your custom spacer, you could use a new steel head tube (I buy mine here http://www.paragonmachineworks.com/f...bes/steel.html). This would set you up to have the bottom of your custom spacer already at spec for (head tube) reaming and facing. Understand that your lower head tube bearing race will be pressed into the bottom of your custom spacer, thus the head tube reaming and facing. Paragon's shortest EC44 (at the ends, will measure 50.00mm O.D. and 44.50mm I.D. when you receive it) head tube is 90mm http://www.paragonmachineworks.com/f...-headtube.html. Note that this head tube is 50mm O.D. on both ends and 48mm O.D. along its length. Of course, you would never try to ream and face this head tube anywhere where it is 48mm O.D. Ream and face only at the ends.

            If 90mm is too long, a machinist (using a lathe and quality 4130 chromoly steel 50mm tubing with a wall thickness equal to or exceeding that of your existing head tube) could make you one with your desired length. If it is an EC44 headset, you need to ream it to between 43.95 and 44.00mm https://chrisking.com/files/public/c...anualinset.pdf, so not a lot of room for error.

            If it were me (with a steel frame), I would properly TIG weld the custom spacer (whether it was made from a new head tube or a machined 50mm tube) to the bottom of the existing head tube.

            As far as clamping in your custom spacer goes, the cap bolt (top of first diagram) threads into the star fangled nuts which are themselves press fit into the steer tube. If the attachment between the cap bolt and the star nut fails (as they may do if somebody overtorques the cap bolt and pulls the star nuts out of the steer tube), the rider is still holding the handlebars which are bolted to the stem which is bolted to the steer tube. When you tighten the cap bolt, it pulls the steer tube up tightly to the top cap which rests on the stem.

            The point here is that the clamping force for normal headset spacers occurs between the star nuts (inside the part of the steer tube that lies inside the head tube) and the top cap.

            For a lower custom spacer, you are still depending on the star nuts being securely attached to the inside of the steer tube, but the aforementioned clamping force is occurring several inches above where you want to clamp. As long as the star nuts are pressed firmly in the steer tube, tightening the cap bolt will pull up the steer tube, same as it does for normal headset spacers.

            You put the bike on the ground (not in a repair stand) when you tighten the cap bolt.

            Welding the custom spacer to the head tube essentially creates one (longer) head tube. This is best for safety at the high speeds achieved on ebikes. If you were never to exceed 5-10mph, just throwing it together might be okay.
            Last edited by commuter ebikes; 07-14-2018, 09:35 PM.

            Comment


              #7
              Also, a 29er fork would be taller.

              Although it was written 6 years ago, this can get you started looking for short crank arms: https://www.slowtwitch.com/Tech/Shor...base_2862.html.

              Getting back to the top cap and star nuts, I always tighten my cap bolt (see diagram) just enough so that I cannot turn the headset spacers by hand. This is a good thing to check every so often: that you cannot rotate the headset spacers around with your thumb and fingers.

              Even more important is to check that your stem bolts are torqued to spec. If your stem is not secured to your steer tube, the wheel will flop all the way to the left or right and send you over the handlebars. Most things that go wrong in the front will send you over the handlebars.
              Last edited by commuter ebikes; 07-14-2018, 08:07 PM.

              Comment


                #8
                Originally posted by Del15476 View Post
                Hi buddy I did say I am replacing the fork with suspension fork As for raising the the forks you where right that’s wat I was hoping I could do add spacers at the bottom of the cup to raise the bike , will suspension forks not raise the front end a bit ? Ta
                A suspension fork will help your crank arm problem at low compression, but make your crank arm problem worse at full compression.
                Last edited by commuter ebikes; 07-14-2018, 09:22 PM.

                Comment


                  #9
                  Thanks buddy That’s exactly info I needed. As for the crank arm Iv went from 170 to 140. Cheers

                  Comment


                    #10
                    I hope you have the parts laying around. It costs more for parts to fix an old bike than it is worth. A fork not made for the bike's geometry will not handle well.

                    Comment


                      #11
                      Lol negative Nancy

                      Comment


                      • Rider
                        Rider commented
                        Editing a comment
                        But oh sooooooooooooooo... true. ;-)

                      #12
                      Some forks are taller than others. A Surly Ice Cream Truck vs. a Surly Moonlander for instance. The 135mm QR versions are different only in the 'axle to crown' measurement. Thats the spec you want to look at to determine your fork length. The Ice Cream Truck qualifies as a 'suspension corrected' fork as its about as tall as a suspension fork, so if your frame was made for one you can use the Surly ICT as a rigid replacement.

                      (p.s. the Surly forks have a quirk in how they mount the brakes that make then unsuitable for someone just looking to plug and play, so don't buy one unless you understand the issue and know how to deal with it safely).

                      Comment


                        #13
                        Originally posted by MoneyPit View Post
                        Some forks are taller than others. A Surly Ice Cream Truck vs. a Surly Moonlander for instance. The 135mm QR versions are different only in the 'axle to crown' measurement. Thats the spec you want to look at to determine your fork length. The Ice Cream Truck qualifies as a 'suspension corrected' fork as its about as tall as a suspension fork, so if your frame was made for one you can use the Surly ICT as a rigid replacement.

                        (p.s. the Surly forks have a quirk in how they mount the brakes that make then unsuitable for someone just looking to plug and play, so don't buy one unless you understand the issue and know how to deal with it safely).
                        Good point about the Ice Cream Truck fork being extra tall. I have those forks on all five of my ebikes. They are 150mm thru axle https://surlybikes.com/parts/forks/i...truck_150_fork. Note that the torque spec for the thru axle is about 16Nm depending on what hub you have; overtorque that bolt and you ruin the hub bearings.

                        I have installed about 9 or 10 disc brakes on Surly forks, but I have never encountered the brake mounting issue that you referred to. What is the issue, that the fork is set up for ISO mount brakes? I have used 180mm and 203mm rotors using an ISO to post mount adapter. I have only used Avid BB7 (mechanical) and Tektro Dorado HD-E710 http://www.tektro.com/products.php?p=35 (hydraulic) brakes, though. Ideally, the company that sells you the brakes would ask if you are running ISO or post mount so that they can ship you the right adapter.

                        The part number of the (ISO to post mount) adapter to fit a Tektro Dorado HD-E710 caliper using 203mm rotors on an ICT or Moonlander fork is D-F203. The “D” is for Dorado, the “F” is for front, and the “203” is the diameter of the rotor.

                        The part number for the rear is D-R203. If you decide to use these adapters, grab some spares while you can in case they ever get stripped; I stripped one of mine because I overtorqued a bolt (steel male going into aluminum female, too much caffeine and blowing off the torque wrench). These particular Tektro brand name adapters are not as easy to find as you may think. I bought my spare adapters from Matt Hughes at EMPowered Cycles.

                        Click image for larger version  Name:	snip.PNG Views:	1 Size:	898.1 KB ID:	69645
                        Last edited by commuter ebikes; 07-18-2018, 07:00 PM.

                        Comment


                          #14
                          Originally posted by commuter ebikes View Post

                          I have installed about 9 or 10 disc brakes on Surly forks, but I have never encountered the brake mounting issue that you referred to. What is the issue,
                          Apparently only applicable to the 135mm version, which is what I need to use with my front motor'd bikes, the spacing for the brake mount is meant for a rear hub. Surly talks about it in the Compatibility link accessed from here.

                          The Surly Ice Cream Truck Fat Bike Fork is ready for trail use and offered in both 135mm quick-release and 150mm thru-axle versions.


                          To adapt them, stories vary. I have heard (MTBR forum posts) you need to remove about half of the width of the brake mount at its base. I have a friend with one connected to my same fat Bafang geared hub motor whose mechanic stated you only need to take off 1-2mm and the pics I saw of the installed fork looked like he didn't take off much more than the paint.

                          I'll know myself soon enough as I have a 135mm Ice Cream truck fork in hand to be used as part of my frame replacement project for the project I mentioned in your brazed frame thread. I have to say that just looking at it and comparing to another fork I have sitting in the garage... I don't see a difference other than a very beefy adapter mount, which doesn't strike me as a bad thing.

                          Comment


                          • commuter ebikes
                            commuter ebikes commented
                            Editing a comment
                            Very informarive about the Surly weirdness.

                          #15
                          This is a fat bike frame 20” by 4” wheel tyres. 29” front forks would be a good idea.
                          Last edited by Del15476; 07-20-2018, 05:20 PM.

                          Comment


                          • Edwin
                            Edwin commented
                            Editing a comment
                            That's exactly what I would suggest, 29" forks but you may have to go with the 29+ or even 27.5+ to get the width right. Not positive though.
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