MTB Geometry (Part 2)

We have a favour to ask:

What’s inside this week:
1. Numbers leaving you baffled? Get familiar with MTB Geometry (Part 2).
2. Gadget of the week, a staple in the newsletter.
3. Shorts - is there a thing as too much chainlube?
4. Links I’d send you if we were friends.

Mountain Bike basics - Geometry.

Geometry refers to the collection of key measurements (lengths and angles) that define a particular bike configuration. These parameters have major influence on how a bicycle handles.

Last week we started a deep dive into geometry. Here’s part 2. You can read last week’s newsletter on our site here https://www.trail-insider.com/p/mtb-geometry-part-1 

Seat tube length - a shorter seat tube can give more manoeuverability when riding technical terrain (when you drop your saddle with or without the help of a dropper seat post), but could have shorter dropper post insertion length. A longer seat tube will contribute to a stiffer feeling frame when pedalling seated, but the trade off will be that you will sacrifice dropper post travel.
TLDR: Longer = dropper post full range; shorter = manoeuverability on descents.

Rear centre (chainstay) - the rear centre (also known as chainstay length) is the horizontal distance from the center of the bottom bracket to the centre of the rear axle. This measurement affects the bike's stability, traction, and handling. A shorter rear centre provides more agility and easier manoeuverability, especially in tight turns, while a longer rear centre offers better stability and traction, particularly on climbs and high-speed descents.
TLDR: Short chainstays = agility, playful pop and manuals; long = more stability and ability to plow through rough terrain.

Front Centre -A longer front centre (distance from your BB to your front axle) gives you more stability at high speeds, making your bike feel like it’s on rails when descending steep, rough terrain. However, it can make tight turns and technical manoeuvers a bit more challenging. A shorter front centre offers quicker, more responsive handling, which is perfect for navigating twisty trails and switchbacks, but it might feel a bit twitchy when you're charging down fast, chunky descents.
TLDR: The distance between your front axle and bottom bracket. More = stability; less = agility.

The wheelbase is the distance between the centres of the front and rear axles. This measurement significantly impacts the bike's handling and stability. A longer wheelbase generally offers greater stability at high speeds and smoother handling over rough terrain, making it ideal for downhill and trail riding. Conversely, a shorter wheelbase provides quicker, more responsive handling, which is beneficial for tight, technical trails and agile manoeuvering.
TLDR: Longer wheelbase = stability at speed; shorter = quick turns and tight manoeuvers.

Standover Height is exactly what it says - if you had to stand with both feet on the floor, can you stand flat footed without top tube / nether region contact. A lower Standover Height gives you more confidence and maneuverability, especially when you need to bail quickly or navigate tricky, technical terrain. It’s great for smaller riders or anyone who values that extra bit of clearance. On the flip side, a higher standover height might offer a bit more frame rigidity, but it can feel intimidating when you need to hop off the bike in a hurry or get low for aggressive riding. Where to measure this exactly on a frame differs from manufacturers, so make sure you check the specific diagram to see if it suits you.
TLDR: How much space you’ve got to clear the top tube. More = seated frame stiffness; Less = better for quick dismounts.

*Stem length & rise, handlebar dimensions, crank length, seat post offset, fork length & axle to crown measurement, trail, rear shock specifications, native brake sizes and even tyre clearance can fall under geometry tables. If you want the same info around those, please let me know and thanks for reading to the end!

That’s a geometry wrap-up and now you know just enough to get yourself in awkward geometry debates.

Gadget of the week: Ryder Bar Mounted Bullet - Pepper Spray

Sheesh, the last few weeks has been hairy for cycling - multiple cases of bike-jacking, attacks, attempted attacks and even stabbings.
I ride by myself often, and on slow road climbs, I feel like a sitting duck on my enduro bike. I’d rather have something for self protection and not need it, than need it and not have it.
This is a compact, slimline pepper spray that comes with- and mounts on the Slyder system. Its a spray and not a stream, which limits reach, but at this size and with how easy it is to access and use, I’d rather have that on my bike, than not carry some kind of self defense. And at R200 - its cheap!

Q. Is there a thing such as too much chainlube?
A. Yes.
I recently serviced a friend’s bike, who lubes his bike often. The only problem is that he does not strip the old lube off before applying new lube. So the build up, similar to that on a surfboard, is quite wild. This is not a dig at my friend, but it highlighted a real problem for many newcomers to the sport.
This creates extra friction on your drivetrain and causes sticky up shifts and delayed down shifts. Sand and grit can get stuck in the wax and start wearing away at your chainring and cassette. I know it is not a fun job, but every now and then, clean your chain and drivetrain - scrape the old wax off your chainring and your derailleur pully wheels, and wherever else you see build up. A chain cleaner and degreaser is a worthwhile investment for effectively cleaning your chain. Let it dry and then you can apply new lube.

About the author:
Hello, I’m Francoin, an Industrial Designer in the cycling industry based in Somerset West, South Africa.

Tools, lights, accessories and bicycle design is my daily graft.

This newsletter is to share some of the experience & industry insight that I pick up along the way, with fellow cyclists. If you are new to the sport, or been riding for many years, I plan to give you something of interest in every edition.

Thanks for subscribing and Happy trails!

FV

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