Mel’s Tech Tips
How To Measure:
- Chain Ring Bolt Pattern
- For a Front Derailleur
- Seat Post
- Hubs
- Steerer Tube
- Read Dropout
How to measure your chainring bolt pattern
The 2 most common bolt patterns are:
110 Bolt Pattern = 65mm center to center (actually 64.7mm)
130 Bolt Pattern = 77mm center to center (actually 76.4mm)
Chain Ring Dimensions (all 5 bolt) Bolt Diameter
How to measure your seatpost
Remove your seat post from the frame then take a rag and clean off all dirt and crud so you can read the numbers. Check size using caliper tool. If you don’t have a caliper tool, you can always use a “poor man’s” caliper by taking an adjustable wrench and use it like a vernier caliper. Once the wrench is open to the correct size, measure the opening with a metric ruler.
Remove and clean seat post
Check size with a Park Tool DC-1 caliper tool
(see cost on our Tools page)
Check size with a “Poor Man’s Caliper”
(adjustable wrench)
How to measure your fork steerer tube
Measuring a Steer Tube at 28.4mm means 1 1/8″ standard threaded head set. Note: inside of steer tube has a star nut (aka star fangled nut) pressed in to hold the fork together to the stem.
How to measure for a front derailleur
Measuring for a front derailleur, this example measures 28.7mm and will utilize a 28.6mm (or 1 1/8″) clamp.
How to measure your hubs
This White Industries Hub is an excellent choice to replace a wheel that is from an older tandem which is 140mm spacing. New for this year and will allow you to run more than 6 or 7 speeds. 8, 9 and 10 speeds are available. Exclusive to Tandems East.
How to measure a rear dropout
Take the rear wheel out of tandem and measure inside to inside of dropout. It’s important to know which one of four sizes (135mm, 140mm, 145mm or 160mm) you need if you want to order a wheelset.
