Alex's custom-specced Marin Alpine Trail E2 ebike

When Marin launched its first electric mountain bike, the Alpine Trail E2, at the very tail end of 2020, I was lucky enough to swing a leg over one of the first test samples in the country to bring you all a full review.

I was seriously impressed with the Californian brand's debut attempt at electrification.

Its top-notch spec, reasonable price tag and awesome performance meant I awarded it 4.5 stars in my Marin Alpine Trail E2 review, which in turn earned it a place in our list of the best electric mountain bikes currently on sale.

Of course, I wouldn't be a technical editor if I didn't think there was some room for improvement.

This edition of BikeRadar Builds kicks off with the Alpine Trail E2's already stellar performance, and looks to build on it with a number of choice upgrades and changes designed to coax out every last drop of available performance, and make this ebike truly mine.

The perfect starting point

Having raved about the bike in my review, I put my money where my mouth is and purchased this Alpine Trail E2 from Marin with my hard-earned cash.

Along with using my heating even less to finance the purchase, it also meant I had a great starting point from which to begin my customisation journey.

At the heart of the E2 is Shimano's DU-EP800 motor and large 630Wh capacity battery. Heavy-hitting parts such as Fox's venerable 38 fork and DHX2 rear shock also feature, bolstering the Marin's exceptional value.

The frame boasts internally-routed cables, chain slap protection and space for a water bottle within the front triangle.

It has a linkage-driven single-pivot rear suspension system offering 150mm of rear wheel travel, and is roughly 17 per cent progressive.

All these elements are combined with near-Goldilocks mountain bike geometry.

The head angle is around 63 degrees, while the seat tube angle sits at 78 degrees.

The size large I own has a 485mm reach figure and 435mm chainstays. These combine with a 1264mm wheelbase and a seriously low 686mm standover height, plus a short seat tube with a large insertion depth for long-travel dropper posts.

A full bike, modified

From the first time I rode an Alpine Trail E2 I was convinced it had more to give, and being able to buy one has given me the perfect opportunity to make all the modifications and changes I wanted to prove that theory.

Mullet massacre

Let's start with the biggest and most important change first.

In an attempt to provide full disclosure I wouldn't say I dislike mullet bikes (29in front, 27.5in rear), and I've certainly loved riding several in recent times (keep your eyes peeled for our 2022 Ebike of the Year reviews, which include loads of mullet-wheeled monsters).

But if given a choice, I'd always fit 29in wheels front and back to one of my personal bikes.

The wagon-wheel setup is arguably quicker, gives more grip and provides a smoother more stable riding character.

I'd also argue the mullet setup doesn't 'create the best of both worlds' (in terms of stability and agility) because a bike can only really be one thing. It's either stable, agile or somewhere in between, but can't be simultaneously the most stable and agile.

And that's why I went feet-first into tuning up Alpine Trail E2's pet hate of mine: its 2.8in wide, 27.5in diameter rear tyre and wheel.

I swapped out the stock wheels for a set of Roval's Traverse Alloy 29in wheels front and back, with the latter fitted with a normal-sized 2.5in wide Maxxis High Roller II, to de-mullet it.

I've specced the DoubleDown casing, 3C MaxxTerra compound version of the popular rubber because I feel it offers the best balance between traction, wear rate and carcass stability.

Up front, I've fitted an EXO+ casing Minion DHF, but had to forego the preferred 3C MaxxGrip compound as this isn't a combination available in my preferred 29x2.5in size.

Geometry stability

So what has changing out the rear 27.5in wheel for a 29in hoop done to the marvellous geometry? Well, not all that much.

To get a flavour of the changes, you only need to look to Marin's human-powered Alpine Trail XR. This bike has 29in wheels front and rear from the factory, but because the two bikes share almost identical geometry, the swap to a big wheel on the E2 brings it very close to the XR's figures.

The head angle now sits at 63.5 degrees, while the wheelbase has extended to 1,283mm and BB lifted marginally to 339mm – which is still seriously low.

There's more than enough tyre clearance at the rear of the E2 to take the 29in wheel and 2.5in rubber... it's almost like the brand designed it to be both 27.5in and 29in compatible.

Always wanting more

Not satisfied, I wanted more. But this time from the front end.

Although the 160mm-travel Fox 38 fitted to the E2 has plenty of squish, and adding an extra 10mm doesn't seem like much, out on the trail that extra give meant a few things.

Firstly I could run the fork a bit softer than the 160mm version, while maintaining my preferred handlebar height without needing to add loads of stem stackers.

It also meant I could create a larger negative air vacuum within the fork's lowers, by releasing air from the lower leg bleed valves while the forks were compressed, without dramatically impacting ride height.

Releasing air from the bleeders improves small-bump sensitivity and traction, and produces similar results to increasing the negative air spring size or pressure by making the forks more eager to compress or suck down into their travel.

Swapping out the Fox 38 air spring was relatively simple, requiring only a few basic tools, some of the recommended Fox suspension fluid and a small amount of knowledge.

All Fox 38 forks can be changed between 160mm and 180mm of travel with an air spring swap. A new air spring costs £159.95.

Of course, if you're looking to change the fork travel on your bike, please check whether the longer distance is within your manufacturer's recommended travel specifications before fitting them to avert voiding your warranty.

Shimano EP8 spotlight

Shimano's EP8 motor offers impressive battery life, user tuneable modes, is relatively light and has proven to be seriously frugal. Combined, these virtues make me think it is the best electric mountain bike motor currently on sale.

But it's not without its faults.

The biggest of these, in the context of the Marin E2, relate not to the motor itself but to the e*thirteen e*spec cranks fitted from the factory. These cranks have been linked to cases of EP8 bottom bracket spindle failure.

Not wanting to suffer from this issue, I fitted a pair of Shimano's own EP8 compatible FC-EM600 cranks for the princely sum of £31.99.

With these cranks fitted from new, and installed according to Shimano's instructions, my EP8 motor warranty should be preserved if the worst happened.

A rather special spec

This wouldn't be a BikeRadar Builds bike without taking a look at each of the hand-picked, top-performing and hyper-functional parts, curated for my rather specific needs.

Shimano XTR M9120 four-piston brakes

Rescued from an old long-term test bike, my Yeti SB165, these are enormously powerful brakes, and are super lightweight too.

Swapping out the stock Shimano SLX M7120 stoppers for these was a doddle thanks to the like-for-like brake hoses and fittings.

A simple gravity method bleed – where the bleed nipple is opened, a full-of-oil bleed up is attached to the lever, and gravity is left to its work to pull fluid through the system – was required to get them working without having to do any internal cable routing surgery.

Unusually, however, I've paired the Shimano brakes with SRAM's CenterLine rotors (rather than the new HS2 which are fitted to my other bike). Although not officially recommended, I had no choice but to go for this pairing.

To the best of my knowledge Shimano doesn't make a STEPS ebike compatible six-bolt disc rotor with in-built speed sensor magnet. That means users of Shimano motors with six-bolt hubs need to get a little creative or change their hubs for Center Lock versions to fit official STEPS discs.

Using a widely available Bosch speed sensor magnet with the EP8, while not recommended, is common practice even among OE manufacturers – including for Santa Cruz on the Bullit.

Thanks to the shape of the six-bolt Shimano XT SM-RT86 Ice Tech rotors I wanted to use, I wasn't able to fit the magnet without it fouling the frame.

That meant using SRAM's CenterLine discs, where between each of the rotor's spokes is a large gap the magnet could fit into, was the only option.

OneUp Components Carbon bar, EDC stem and Dropper Post V2

These components from OneUp are all favourites of mine and have been fitted to many previous test bikes.

I love the shape and feel of the Carbon bar and have paired it with OneUp's EDC stem. This means I have the option of installing the brand's EDC tool inside the steerer tube without having to tap threads into it.

The OneUp Dropper Post V2 offers one of the shortest lengths for the most travel of any post out there. Plus it's really simple to service and has proven to be incredibly reliable after miles and miles of testing.

On the Marin E2, I've fitted the 210mm-travel version but have installed 20mm of internal travel spacers, taking post drop down to 190mm.

Although more travel is frequently better, I don't like to have my seat totally slammed on descents because I use the inside of my thighs against it to control the bike, something that isn't possible if it's too low.

Thanks to the dropper lever's I-Spec compatibility, I've also managed to reduce some of the bar clutter and fix the compatibility issues I moaned about on the stock Alpine Trail E2.

This means I've cleared up a bit of space on the bars, fitting the motor controller between the brake lever and grip.

Fabric Funguy grips

Although these have officially been discontinued, with Fabric ceasing trading, remaining stock is still available to buy from certain retailers for reduced prices.

I absolutely love these grips. They're soft, comfortable, the right diameter and have just enough movement and flex to reduce vibrations and harshness rather than enhance them.

If you can find a set (that I've not already bought myself) then I would strongly recommend buying them.

Fizik Terra Aidon X5 saddle

I got a bit of a preview of the Aidon X5 saddle's comfort while I was doing the testing for 2022's Ebike of the Year, where I spent many hours sitting on the ebike-specific perch from Fizik.

Fortunately it proved to be incredibly comfortable and shot to the top of my 'must have' list when it came to building up my own dream-spec ebike. This alloy-railed version weighs 272g.

Mudhugger Evo (long)

Living in the UK, a fit-and-forget front mudguard is a must. While Fox makes its own mudguard for the 38 fork, I find it doesn't offer enough wheel coverage, allowing more mud to spit up onto my face than is ideal.

The Mudhugger Evo (long) is the solution to this problem, and this Evo version has received iterative changes over the old one.

Its stepped design now offers more crown clearance to stop it banging against the guard at bottom out. The lengthy rear portion provides plenty of mud protection to boot.

While this version is attached to my forks using zip ties, velcro straps are supplied with the guard and Mudhugger even makes a direct mount version that screws directly into the back of the fork arch.

Pedaling Innovations Catalyst flat pedals

My love for flat pedals started the day I took up mountain biking and has never waned.

These ludicrously sized (128(L)x95(W)mm) pedals represent a change in direction for flats, where the maker claims they'll revolutionise flat-pedal riding with unparalleled foot stability and traction

Testing is still ongoing – which is why they're fitted to this bike – but initial impressions are positive, where foot twist and clawing have virtually been eliminated.

Keep tuned for a full review soon.

Shimano drivetrain upgrades

Although the E2 comes fitted with a Shimano Deore XT M8100 rear derailleur that I've kept bolted to the bike, the shifter and cassette are from the Shimano SLX M7100 range.

On my quest to shave grams where possible and make functional upgrades, I saw these two components as easy targets.

I swapped the shifter for a Shimano XTR M9100 unit, much preferring the positive click of the lever, and lost three whole grams in the process.

The cassette – now upgraded to an XT M8100 10-51t tooth unit I had from an old test bike – saved a further 46g, but this time from the all-important rotational and unsprung mass of the bike's rear wheel.

Are these marginal gains? Yep. Do they offer a significant improvement in performance? Arguably, no.

They do look and feel good though.

Roval Traverse Alloy 29 wheels

Having recently tested these wheels – you can read my Roval Traverse Alloy 29 review – I was seriously impressed by the balance of comfort, steering accuracy and reliability they offered.

At just 1,939g for the pair, they shaved a significant amount of weight off the bike compared with the stock Marin hoops, hopefully without compromising strength.

Although the £650 asking price isn't cheap, it's still significantly less than the likes of the Zipp 3Zero Moto, ENVE AM30, and even the DT Swiss EXC 1501 Spline One wheels.

And as I already mentioned, these wheels are wrapped in Maxxis rubber with a DoubleDown rear casing and EXO+ at the front.

How much does my Marin Alpine Trail E2 weigh and cost?

As the bike currently stands – pedals and all – it tips the scales at 24.6kg.

Without pedals that drops to 24.07kg, only 1.37kg heavier than the mind blowing Specialized S-Works Turbo Levo (22.7kg), once I'd fitted GRID Gravity casing tyres to it.

In terms of cost, that's a tricky figure to pin down.

The initial £5,765 asking price of the Marin has clearly inflated somewhat, but quite a few of the parts I've removed I would be able to sell to claim some money back.

If I was just totting up the cost of the upgrades without spending time on eBay getting cash back I'd be looking at a total cost of £8,407.92.