Wheels Need Help with Wheel sizes for my bike frame

Discussion in 'Bicycle Repair' started by StrontiumEthics, Sep 17, 2009.

  1. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    I believe i posted my last thread in the wrong section so Im posting it in this section just to be on the safe side. But I got a frame and refurbished it. It looks like it used 26" wheels. What I want to do is put a 20" wheel in the back and a 26" wheel in the front to archieve a "Chopper-Like" effect. I was wondering if I can do that with this frame. I am aware of the gearing stuff so no need to mention that. In addition, I would like to know if it will crack the frame or something when im riding. The frame is made of steel. and looks like its a frame from the 90's. Seems pretty sturdy when I lifted it. lol = 0

    Here are some pictures of it. I sanded it and primed it. Just need to sand is a little more to smoothin it out and then I can put my color.

    Tell me what you guys think about my predicament.

    Attached Files:

  2. ocscully

    ocscully Member

    I would think the only areas of concern would be, first maintaining a rear brake? If you are using a coaster brake wheel then you won't have a problem but the frame is built to have a side pull brake attached to the plate on the seat stays and you will have to add another mounting plate or reposition the one you have to get the side pull brake to reach the smaller rim. Second area of concern would be the ground clearance at the bottom bracket. Using a 20 in wheel you will be dropping the bottom bracket several inches and you may have problems with the pedals draging the pavement on turns.

  3. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Here I actually found time to put things together to see how it looks and take a picture. Here are the pictures I took. The pedals are like 6-10 inches off the ground. To low perhaps?
    Tell me what you guys think.

    Attached Files:

  4. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Sorry forgot the other picture = 0, = )

    Attached Files:

  5. banzo

    banzo New Member

    how's the chopper?

    I can't find any reasonably-priced 20", quality front suspension fork for my folding Downtube 20". I have the reverse option of adding a 26" front wheel to a 20" frame [or a 24"] IF I can find a suitable suspension fork that I can $$?

    I need to replace the front wheel anyway and upgrade to a 36-spoke rim. Doing both upgrades at the same time makes sense.

    Any comments on how the build handles -- can you tell anything is amiss?

  6. Chalo

    Chalo Member

    Changing the fork length or the diameter of either wheel will change the frame angles (and therefore the steering characteristics), weight distribution, and crank height, almost inevitably for the worse on all counts.

    I have built a bunch of long-forked bikes, and even when they have correct fork offset (which your bike will not), they possess sketchy handling and bad habits like front tire skidding.

    Folding bike handling has already been heavily compromised for the sake of foldability. Why mess it up further?

    You didn't mention whether you have a suspension fork now that you're not happy with, or a rigid fork.

    If you must use a mountain bike suspension fork (and I do not recommend this in your case), get the shortest one you can find, and pair it with a 20" (or even 16") wheel and a drum or disc brake.

    Even in the most common 26" size, cheap suspension forks are junk. I think you'll be far happier using a rigid fork with a big fat 20" tire at low pressure. Air is the lightest and most effective suspension of all!

    3G bikes makes a slick 20" tire called the Twenty G that measures about 2.7" wide (claimed size is 20x3.45). That's over two inches of quiet, reliable, lightweight, effective suspension travel right there. It's not expensive, and it's a decent quality tire. It may be a little difficult to find a 20" fork that fits the Twenty G. Fitting it in a 22" or 24" fork will be easier.

    If you use a superfat tire like the Twenty G, you'll probably need to combine it with a drum brake (or a disc brake if your fork is so equipped).

    There is another inexpensive tire called the Animal GLH that comes in a generous 2.25" width and will fit in most 20" forks. If you are willing to pay more (about $40), you can choose from a variety of lightweight Kevlar-beaded freestyle tires in the same size range, or the excellent Schwalbe Big Apple 20 x 2.35" city bike tire.

  7. banzo

    banzo New Member

    Thanks, Chalo!

    I value you sharing your experience with similar builds. I thought I was begging for unseen problems -- it usually happens whenever I get a "bright idea" that seems "simple." Your words about changing the weight distribution of the frame -- along with added, front-wheel-skidding -- makes sense.

    Fortunately, a Suntour rep informed me that a 20" version of the Swing-Shock is about to be released [09 or 10/11.] Hopefully, it will be in my price-range and will ably-replace my failing, cheap, original-equipment, pogo-stick-shock-fork. I like the fact that the Swing-Shock is designed with limited travel. Even car shocks with springs bottom-out on the chuck-holes!

    For those interested, here's a short video on maintenance of the existing sizes of the Swing-Shock:

    http://www.srsuntour-cycling.com/index.php?screen=tv.home&SearchWord=swing shock&task=search

    I can't understand why no one combines a "shock-absorber" handlebar stem to further absorb the vibrations of the road? My hands get numb quickly on longer rides; uncomfortably-so.
  8. Chalo

    Chalo Member

    Very interesting....

    I had not heard of that suspension fork. It's like an update of the AMP fork. That's pretty cool.

    Allsop and Girvin both did so in their day.

    The Allsop Softride stem had a parallelogram linkage, so the brake and shift levers wouldn't dive when the stem articulated. The Girvin Flexstem was a simple pivoted arm. Both of them went away when the growing suspension fork trend combined with a trend towards shorter stems.

    Your hand discomfort sounds like it could be addressed by handlebars with more sweep (e.g. Wald #8095, On-One Mary Bar), softer tires, broader grips (e.g. Ergon), higher bar placement, or a combination of these.

  9. DougC

    DougC New Member

    The only good 20" suspension forks I've seen cost $450-$550 or so.

    That depends on what you consider quality. Suspension without oil dampening is a waste of money, IMO.

    Rock Shox is what I would consider the minimum brand.

    The Dart-1 or Dart-2 is about $90, but has no dampening.

    The Dart-3 is $150 but has oil dampening.

    Marzocchi is the next-cheapest "decent" brand, starting at around $300.
  10. happycheapskate

    happycheapskate Active Member

    I had a Manitou elastomer sprung fork in the 1990's. When I was standing and pedaling, it was ok, but it froze in cold weather, and it always "topped out" when riding in the saddle. (When it hit a bump, it compressed, then sprung all the way to the stops, and it was annoying, plus sometimes the traction on the front wheel would be lost a little).

    I agree with the guy who said a rigid fork and a fat tire works great. I put a DH 2.25 front tire on my beach cruiser and it was a world away from the 1.95 all-terrain that I had on it earlier.