When it comes to putting up a brand-new bicycle, one of the most essential phases is determining where the seat will be positioned on the rails. This step is often referred to as the “saddle setback.”

Remember to take notes on your optimum seat placement after you’ve found it out, and make sure you have a method that allows you to replicate that position easily, whether it’s on a different bike or during the ride you’re currently on. When switching frames, make sure that you are aware that not all bikes have the exact same angles, and that you will need some method to compare the geometries of one frame with the other. If you do not have this method, you should not move frames.

You will, of course, realise that you cannot use the same position on the saddle rails between the two bikes once you have realised that different frame geometry will mess with your saddle setback. This realisation will come after you have realised that your saddle setback will be affected negatively.

This write-purpose up’s is to provide you with the knowledge and tools necessary to recreate your perfect saddle setback on any bike. After the break, I will provide a few pointers that, if followed, will make the procedure less fraught with difficulty, and I will also demonstrate how to construct a bespoke setback tool that will make it simple for you to place your saddle.

The easy method for measuring saddle setback

Dropping a plumb bob from the top of the saddle and marking with masking tape or a felt-tip pen where the string crosses the frame or crank is a simple way to determine the amount of setback that has to be adjusted. After that, you will be able to take measurements from the place that was designated to the centre of the bottom bracket spindle. The string always moves around and gets caught on the frame a little bit while I’m trying to take the measurement with this method; basically, I never really know if the spot that the plumb line settles on is really the right one. Despite the fact that this method is straightforward and relatively inexpensive, I’ve also found it to be one of the more challenging ones.

The do-it-yourself saddle setback tool

I pieced together this gadget out of discarded materials after getting the idea from a discussion thread on roadbike review. The fundamental concept that underpins the tool is that all of your measurements should be referenced from the BB axle. Because the instrument may be moved from one bike to another, it is simple and straightforward to precisely transfer measurements to a number of different bicycles.

The saddle must be the exact same on each of the bicycles in order to follow this strategy. To get the do-it-yourself saddle setback tool ready for use, you must first remove one of your bicycle’s crank arms, and then thread the tool into the BB axle that was previously placed.

If you don’t want to remove your crank arms, you can modify it to work with them in place by using a different method for attaching it onto the BB. The tool I saw on the forums used an 8mm allen wrench that had been cut down to a stub and glued to piece of wood. If you use 14mm crank bolts you could take a socket head and glue it into a piece of wood.

Also note that my measurement is actually being referenced off one of the faces of the angle bracket and not the actual center point of the BB spindle. This measurement can easily be determined by measuring from the center point of the tool (which represents the center of the BB axle) to the edge of the angle bracket.

  • Materials
  1. You need something long and thin to connect to the BB. I used a piece of aluminum angle bracket I found next to a dumpster at work.
  2. You’ll need a level or something to ensure that you have the unit perfectly vertical when you measure to the saddle. I used a cheap bubble level.
  3. You’ll need a method of attaching the unit to your bike. Either directly onto the BB axle, or onto a crank bolt. I just drilled a hole in the angle bracket and used a crank bolt.
  4. Finally you will need some sort of ruler to make the actual measurement. I used a square which allowed me to use the angle bracket as a reference point to measure accurately to the tip of the saddle.
  • How to use it

Attach the unit to the bike. For me, this part can be a bit of a a pain because I have to remove the crank arms and attach it directly to the BB. After you’ve attached the tool to your bottom bracket, rotate the unit until your level says that it is perfectly vertical.

Next, place the t-square against the side of the angle bracket, slide the ruler until it just touches the tip of the saddle, and then lock the t-square down. As you continue, remember to keep the t-square / ruler locked because its measurement was taken from your original saddle position; it is this dimension that you want to replicate on your other bike.

After you’ve established your point of reference, transfer the unit to your second bike. Place the t-square on the angle bracket and rotate the unit until the ruler touches the tip of the saddle. Check to see if the level indicates that the tool is vertical before sliding the saddle fore or aft until the ruler hits the tip of the saddle.

This tool will help you get very close to matching your saddle positions between multiple bikes. While it is crude, and with a few modifications it could be even better, it does the job.