Iím thinking about installing some Pacenti (PT-1D) track ends on my Peugeot bike. Doing this will lower my bottom bracket along with making the geometry of the bike slope (ie the top tube will be at an angle upwards). The back wheel looks as if it will drop about 1 to 2 cm with the ends installed. Will this slanting affect anything besides visually seeing it? Will it even be noticeable?
Any tips on installing the track ends? Alignment is my biggest fear right now.
As for your geometry, lowering the rear that much would slacken the frame angles about a degree and it would lower the BB a bit too- how noticeable it is is pretty subjective, it's really up to you how much it matters. There are ways to compensate by positioning the new end furthur down, changing the angle of the slot, etc.
One tip for keeping the ends square with each other is to bolt them both to a dummy axle, lay the assembly on a flat surface, and rotate one side until you can get four points on the ends to touch simultaneously. Keep them bolted together until all your brazing is done.
On the alignment issue let’s say you put a wheel in place and align the drop-outs so that the wheel centers perfectly. Next you heat and braze the right (Drive side.) drop-out. Then you braze the left side. As you braze the left side, the right side is cooling and the seat stay is contracting. The result is when you are finished the wheel will be off center and slightly to the left.
The answer is to set the wheel off a smidgeon* to the right. Braze the right side first, then the left side, and when every thing has cooled, the wheel will be centered. Just tack braze first and allow to cool. If the wheel is off center, re-heat the brass tack to just below melting point (Dark red heat.) and the brass will become plastic and can be reset by pulling the wheel over at the rim.
Again you will have to over compensate to allow for the joint to contract as it cools. Once the drop out is tacked, allowed to cool, and the wheel centered you can remove the wheel and fully braze. The seat stays will now expand and contract equally and will stay in alignment providing you don’t get the joint so hot that you melt the whole thing and it moves.
Should you braze the whole thing and the wheel is out of alignment you could file the drop out. A few thousands of an inch off the drop out will not be noticeable but will make a big difference at the wheel’s circumference. Alternatively, you can try this trick. Heat the seat stay that you wish to shorten an inch or so above the brazed joint. When it reaches orange-red heat, tap the bottom of the drop out with a hammer. (One sharp tap is all you need.) This will compact the metal and shorten the seat stay. There may be a slight bulge left in the seat stay that you can draw file out. The seat stay wall thickness is substantial at the bottom end so structurally this should not harm it.
*A smidgeon is an undetermined amount that only comes with experience.
Last edited by Dave Moulton; 01-14-07 at 06:12 AM.