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Stability problemsHello, In the fall I purchased an older ('94) P-38. While riding at 30+mph, going downhill, I seem to be having a high degree of difficulty keeping the bike in a straight line. I consider myself a "newbie" and realize that I have not put the miles in to be effective for this bike. But for some reason I do not think that my inexperience is the sole reason that I am having too much "twichiness." 1) Could it be that I have a RANS handlebar with a RANS steering tube that is not entirely compatible with the bike? The LBS gave me the diameters of the parts and the difference but I forgot what they were...something about 1in and 1.25in. The steering tube has been tightened as far as it can go but it is not difficult to turn the handlebars when holding the front tire. 2) Would getting a 20in Lightning Fork help with stability? Currently, I have a 16in suspended front. 3) Is my problem just lack of miles? This winter has not been good for riding, but I have put in the miles with the recumbent excercise bike. I am anxious for spring! I am not sure why, but I have this feeling that I want to change to a 20in fork but I do...This really shouldn't have much to do with my stabililty problem. Thanks,
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Stability problems
I have a 10 year old P38 recumbent with a 20" fork. The fork steerer tube has either a 3/4" or 7/8" O.D. I got a slotted sleeve from Lightning which slides over the fork steerer tube to increase the size to 1". I am going to replace the standard P38 steering mast with one I bought from TerraCycle which has a 1" I.D. and a 1-1/8" O.D. With the TerraCycle mast you can use different length stems from other manufacturers for the fit you desire.
Barret, the sleeve that I bought from Lightning may also resolve your problem with the loose steering mast.
BikingAlan
RANS steering column / handlebar on Lightning P-38
Hello Barret,
Long-distance bike problem diagnosis is rather tricky. But what the hell - you did solicit our thoughts.
1) You write that "it is not difficult to turn the handlebars when holding the front tire." Though the RANS steering column is tightened down as far as possible. This is not good. You should not be able to do this at all, and if it is not difficult, something is amiss. The Lightning fork steerer tube is threaded with a compression slot cut into the top. At least that is how all the older P-38 bikes I have ever seen are built. The Lightning steering column / stem is inserted INSIDE the top of the fork, and a seatpost clamp is used to compress the steerer tube top, locking the stem portion in place.
If I am not mistaken, you are using a RANS flip-it stem that is tightened down around the OUTSIDE of the fork steerer tube, gripping the threaded part. This might be the source of the insufficiently tight connection. It might be possible to get a tighter fit by inserting a shim between the RANS stem and the fork steerer tube. Try taking a tin snips to a soda pop or beer can to make a shim. Keep thickening the shim until the fit is tight.
Maybe this will help, maybe not, but it would not be hard to try.
2) Have you checked to make sure that your headset is nice and tight? Sit on the bike and grip the front brake lever. Now try to gently rock the bike forward and backward. If your front brake is properly locked on the front wheel, but you can still get a little rocking motion going, you probably have a loose headset. Not a good thing. Get it fixed.
If you are able to a) get a tight and secure connection between your fork steerer tube and the RANS stem, and b) determine that the headset is properly adjusted, but you STILL get the instability feeling at speed, you need to take the bike to a competent recumbent-friendly mechanic.
Switching to a 20" fork might be a good idea for independent reasons. That depends mostly on your ex-seam. But the 16" fork / front wheel are not the source of your instability problem.
There are probably a variety of other things that may be causing your problem, but these two are what occur to me now.
Above all, do NOT ride the thing at speed until you get the problem sorted out. Hope this helps some.
Safe riding,
Joel Dickman