The Marin San Quentin hardtail mountain bike family appeared five years ago and has won many fans. It was designed to be the big sibling to the Marin Alcatraz dirt jump bike, taking its generous standover and playful nature and splicing them with the DNA of a modern trail hardtail.

We came up with a bike that’ll happily take on anything from big mountains to backyard dirt jumps. The Marin San Quentin is capable, affordable and lots of fun.

When it was first released, the Marin San Quentin was built with 27.5” wheels. We’re now offering it with a choice of 27.5” (also called 650b) or 29” wheels, across the entire range and in all sizes from small to extra large.

You’re probably wondering ‘What is the best wheel size for a mountain bike?’ and asking yourself ‘What wheel size bike do I need?’.

Should I buy a 27.5” or 29” mountain bike?

Let’s start by looking at each wheel size. First, why a 29er or 29” mountain bike?

29” mountain bike wheels have been around for years, but only really became popular from around 2005 onwards. They polarised opinions when they started appearing on the scene, as they were often used to make up for the lack of suspension travel on cross-countryrace bikes.

29” wheels are still dominating the sharp end of XC racing, but are now the standard on an ever-growing number of bikes of all shapes and sizes, from downhill racers to bang-for-your-buck hardtail mountain bikes.

So are 29-inch mountain bikes better? Yes and no! Let's look at some of the advantages of 29" wheels.

First off, 29” wheels are obviously bigger.

One major advantage of larger wheels is that your tire will have a bigger area of contact with the ground, which means more traction for braking, cornering and climbing.

A larger wheel diameter also means that on rough, blown-out sections of trail, it’ll roll slightly better, and is less likely to get hung up in holes in the trail surface or rocky chunder.

A bigger wheel also has more inertia. That means that once up to speed, it’ll want to keep moving in that direction, which can definitely be an advantage for straight-line speed over rough ground. If you like to monster truck through techy sections of the trail instead of having to pick your way, 29-inch wheels will feel that extra bit more unstoppable.

But what about those 27.5” mountain bike wheels?

27.5” wheels were born as a middle-ground between 26” wheels and 29” wheels. 29" wheels were growing in popularity, 26" wheels were fading and 27.5" popped up to offer riders the best of both. A little more roll-over than 26" wheels, a little lighter and easier to chuck around than 29".

What's the difference between 27.5" and 29" wheels? Not much - they're just a little smaller.

So why 27.5” mountain bike wheels?

What are the advantages of 27.5" mountain bike wheels? Let’s start with the obvious one - weight.

Assuming that all the components used to build them are the same, a 27.5” wheel will weigh less than a 29” wheel. We’re not talking a huge difference here, just a handful of grams, but it will have a small effect on the way the bike rides.

Thanks to the laws of physics, weight on a rotating part like a wheel also feels more noticeable than a bit of extra mass on a non-moving part like a frame.

You’ll be more aware of wheel size and weight if you ride trails which involve a lot of acceleration and braking, or lots of sudden changes of direction. A bigger wheel can feel a fraction less nimble when things get really tight and twisty, and if you like to pop off stuff and play your way down the trail, 27.5” mountain bike wheels may be more your bag.

Are 27.5" Wheels Better For Jumping?

27.5” mountain bike wheels can also be a good choice if you like your air time.

Although all bike wheels can take a fair bit of abuse, shorter spokes are more forgiving of sideways landings and smaller rims won’t mind as much if you case the odd landing.

Smaller wheels are also a little easier to throw around, pump and jump - you’ll rarely see a 29” bike at the BMX track, pump track, dirt jumps or skatepark.

Are 27.5" or 29" Wheels Better Suited To Taller Or Shorter Riders?

The most common reason given for offering a particular wheel size is rider height and weight, and there’s definitely something in this.

For shorter riders, a slightly smaller wheel can make everything feel more in proportion, which is why some of our bikes use 27.5” mountain bike wheels for smaller sizes and 29" wheels for larger ones.

But it doesn’t have to be that way for everyone. Smaller, lighter riders may also prefer having a bigger wheel that doesn't get knocked out of line as easily when things get gnarly. Taller riders may enjoy the nimble feeling of a slightly smaller wheel. Some people, regardless of body size, find that a bigger or smaller wheel just feels right, and who are we to tell them they’re wrong?

For the Marin San Quentin mountain bike, we’ve made both wheel sizes available across all sizes, from small to extra large.

Taller riders who really want to stretch out may want to check out our high-end steel enduro hardtail, the Marin El Roy, which features super long reach across two sizes. Younger riders can take on serious trails on our junior-friendly San Quentin 24.

27.5" or 29" San Quentin Then?

So should you buy a 27.5” or 29” Marin San Quentin mountain bike? Yes, you should! But you’ll need to think about which best suits you, your riding and your trails.

Our recommendation would be to go for the Marin San Quentin 29" if you're into go-anywhere, ride-everything kinda rides. You want to cover some distance, tear-up some downhills and you're looking for a versatile, capable mountain bike.

We'd choose the Marin San Quentin 27.5" if you want all of the above but with a little more emphasis on shreddy, playful riding. More jumps, more tight-and-twisty berms, more tricks, more pump tracks and dirt jumps.

Either way, you’ll get an incredibly capable trail bike, with features like a plush suspension fork, powerful hydraulic disc brakes, tidy internal cable routing, reliable single-ring drivetrain, wide tubeless-compatible rims paired with tough grippy tires, and a dropper seatpost (on the San Quentin 2 and above). You even get a set of grippy Oso pedals included to get you shredding out of the box.

Fun times await, whatever your wheel size!