Web version of the Jump Stop instruction sheet:

  Thank you for choosing the Jump Stop chain guide.  From now on, you will be able to downshift with confidence because this guide covers the entire engagement zone  with stainless steel.   Also, the inner limit adjustment on your front derailleur need no longer be a compromise between performance and safety.  After your Jump Stop is installed, you can adjust your front derailleur for maximum performance downshifts and let the Jump Stop make sure your chain hits the small chainring perfectly every time.  If your chain should do a reverse derailment (a whiplash derailment starting at the bottom) the Jump Stop is designed to catch the chain at the top and hold it in contact with the small chainring.  In most cases,  simply pedalling forward will thread the chain back on.  Note:  The Jump Stop is not for the sort of chain suck where the chain fails to disengage at the bottom and wedges up between the chainring and frame.  There are other products to address that problem.  However, chain snarls and jams which are a direct result of derailment (eg. BB wedgies and knobby suckdown) are, of course, eliminated along with the derailment problem.

Fit:  The Jump Stop will fit most, but not all, derailleur bicycles.  It mounts on the same frame member as the front derailleur, directly below it.  The Jump Stop needs to have about 3/4 of an inch (18 mm) of tube length free of obstructions and the frame member needs to be in one of three diameters: 1-1/8, 1-1/4, or 1-3/8 inches. (approx. 29, 32, or 35 mm).  Please make sure the size marked on the header tag matches the outside diameter of the frame member below your front derailleur.  The Jump Stop is not recommended for strongly ovalized tubes if it cannot be mounted above the oval tube section.  For best results, the inner chainring should have less than 5/32 inch (4 mm) total side-to-side movement at the top (e.g. due to bearing play, ring warpage, or crank flex).  However, your chainrings do not have to be round.

The Parts of the Jump Stop

Installation:  1) Clean the frame tube below the front derailleur.  Wrap the clamp around this tube at the same height as the top of the smallest chainring.  If installing in cold weather, it is recommended you run hot tap water over the clamp first.  (Do not use flame to warm the clamp.)  Avoid clamping any control cables or speedometer wires against the frame.  The “N-GEAR” mark should be right side up, and the ends should almost meet on the chainring side of the seat tube.

CAUTION  The mounting clamp is fiber reinforced.  While this provides added strength, it does reduce flexibility somewhat.  Avoid flexing the clamp backwards, twisting the clamp, or bending it sharply as this will only break fibers unnecessarily.

2) From the front, fully insert the screw through both ends of the clamp.

3) Install the guide bracket on the rear of the clamp.  A few screw threads should protrude through the slotted arm on the guide bracket and the ramped guide face should be running forward alongside the chainring.

4) Secure the guide bracket to the clamp by threading the toothed nut onto the end of the screw.  The locking tooth should fall into the slot on the guide bracket.  (If you find the tooth is limiting your side-to-side adjustment, rotate the nut a half-turn so it points away from the closest end of the slot.)

Adjustment: 1) Shift the chain to the smallest chainring and largest freewheel cog.  Slide the clamp up or down the frame tube until the chain link pins run between the two tracks shown below.  The Jump Stop handles reverse derailments better toward the upper track, but is fully effective against forward (normal) derailments throughout this range.


Upper and Lower Tracking Limits for
Chain Link Pins

2)  Slide the bracket left or right until there is a 1.5 to 2 millimeter gap (the thickness of a penny and a nickel respectively) between the chain at its closest point and the front of the guide bracket.  This gap is primarily for handling reverse derailments, so it can be less if this is not a consideration.  Also, the gap may be smaller toward the rear of the guide so long as the chain does not rub during pedalling.

3) Secure the bracket in place by tightening the screw with a 4 mm or 5/32 in. hex key (included).  Once the screw is tight enough the bracket won't slide from side to side, the clamp will be secure.  Additional tightness is unnecessary.  Give the crank a spin to make sure the chain does not rub against the guide.  (Recheck this clearance whenever you service the right crankarm.)  That concludes installation and adjustment.  It is now safe to loosen the inner-limit set screw of your front derailleur for maximum performance downshifts.  If you are unsure how to make this adjustment, consult your favorite bike shop.

No-Hassle Warranty:  The Jump Stop is meant to be a permanent fix for suicide downshifts.  If any part of your Jump Stop fails—for any reason—just tell me what replacement part you need and where to send it.  (Remember to specify the size if you need the clamp.)  If you have questions or problems, I can usually be reached at:

(800) 659-4607   or   (830) 755-4607
303 Whitworth Rd.
Boerne, TX 78006-8559