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Ships within 48 hours · Estimated delivery Jul 26 - Jul 31
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Description
e fat mountainbike ELECTRIC FAT TIRE E-BIKEIntroducing the all new Keystone Electric Fat Tire Bike. Since 2013, Borealis has specialized in lightweight, high end fat bikes. The Keystone is our first ever Class I electric bike. The frame geometry is optimized for riding just about anything with clearance for up to 5 wide tires. Paired with the most technically advanced components in the industry, the Keystone sets the standard for premium quality Electric fat bikes. HIGHLIGHTS Color: Gunmetal
Introducing the all-new Keystone Electric Fat Tire Bike. Since 2013, Borealis has specialized in lightweight, high end fat bikes. The Keystone is our first ever Class I electric bike. The frame geometry is optimized for riding just about anything with clearance for up to 5” wide tires. Paired with the most technically advanced components in the industry, the Keystone sets the standard for premium quality Electric fat bikes.
HIGHLIGHTS
- Color: Gunmetal Grey with Cobalt Blue Graphics
- Weight: 56 lbs. as shown.
- Standard features include Shimano EP8 Drive Unit, Shimano 630Wh Battery, SRAM G2 RS brakes, Mastodon Pro EXT 120mm suspension fork, carbon handlebars, dropper seat post, durable Sun Ringle Mulefüt rims and your choice of tires.
- Frame geometry provides responsive handling, offering maximum control for varying conditions in snow or sand.
- Tire clearance up to 26x5” and 27.5x4.5”.
- Lightweight, 6000 series aluminum frame comes with internally routed cables, 1-2 bottle cage mounts and lizard skin protection.
- Keystone Frames are backed by our LIMITED LIFETIME WARRANTY.
ASSEMBLY
Some assembly required upon receipt. Your bike will be completely assembled and tuned by Borealis, then partially disassembled for shipment. The remaining assembly will require installation of the rear derailleur, chain, fork, seat post, wheels, and handlebars. A kit will be included with your order that has all the necessary tools assemble your bike, including a multi-tool, torque wrench, and shock pump. If you are not familiar with this level of assembly, we recommend having your local bike shop complete the assembly.
Stay tuned for our step-by-step assembly video.
WHEELS AND TIRES
- All bikes come standard with tubes.
- If you order rim tape with your Mulefut rims, we will tape the rims and install the tires with tubes.
- Tubes must be removed and tubeless valves installed for tubeless set up. We recommended to have this completed by a professional bicycle mechanic.
SIZE CHART
BUILD SPECS
| Frame | Borealis Keystone Aluminum 15", 17", 19", 21" |
| Drive Unit | Shimano DU-EP800 |
| Battery | Shimano BT-E8036 (630Wh) |
| Display | Shimano SC-EM800 |
| Assist Switch | Shimano SW-EM800L |
| Speed Sensor | Shimano EWSS300L540A |
| Fork | Manitou Mastodon PRO EXT 120mm, 51mm offset |
| Headset | FSA w/ Star Nut |
| Stem | Borealis 50mm |
| Handlebar | Borealis Carbon |
| Grips | Ergon GP1 |
| Saddle | WTB Volt Medium Steel |
| Seat Collar | Borealis Bolt-On |
| Seatpost | KS Lev Integra 125mm (SM, MD) / 150mm (LG, XL) |
| Brakes | SRAM G2 RS |
| Rotors | SRAM HS2 200mm front / 180mm rear |
| Shifter | SRAM AXS Pod Contoller Right Bridge w/ MMX Clamp for GX Eagle Transmission |
| Derailleur | SRAM GX Eagle Transmission Derailleur |
| Cassette | SRAM GX Eagle Transmission Cassette 10-52T |
| Chain | SRAM GX Eagle Transmission Flattop Chain |
| Crank Arms | Samox 170mm |
| Chainring Mount | Samox 104 BCD for 75mm chainline |
| Chainring | SRAM Eagle Transmission E-Bike MTB Chainring 104 BCD 36T Steel |
| Rims | Your choice of SunRingle Mulefüt SL - 26x80, 27.5x80, or 27.5x65 |
| Spokes | Straight Gauge 2.0 Black |
| Hubs | Borealis Gen 4 15x150 / 12x197 |
| Tires | Your choice. All tire options are listed online. |
| Included | Shimano ECE80042 Battery Charger, AXS Power Pack, Kickstand, UDH Hanger, Key for battery release, Borealis Rear Thru Axle, Remote Battery Charging Adapter |
| Weight | Size Medium w/ Mulefut 27.5x80 & Terrene Yippee Ki Yay 4.3" Tires: 56 lbs. |
FRAME SPECS
| Wheel / Tire Size | 26 x 3.8–5.0" on up to a 100mm rim / 27.5 x 2.8-4.5 on up to a 82mm rim / 29 x 2.25–3.0 |
| Susp Fork Travel | 120mm |
| Fork Offset | 51mm |
| Headset-Upper | IS41 |
| Headset-Lower | IS52 |
| Seatpost | ø31.6mm |
| Seat Collar | ø34.9mm |
| Dropper Compatible | Internal - 125mm for SM & MD / 150mm for LG & XL |
| Front Derailleur Type | Not Compatible |
| Bottom Bracket | Shimano EP8 |
| Crankset (Max Ring) | Chainline 75mm / 1x (38t) |
| Rear Brake (Rotor) | 74mm post (160–180mm) |
| Rear Spacing | 197 x 12mm thru-axle |
| Rear Axle | ø12 x 222L, TP= 1.0, TL = 16 |
| Derailleur Hanger | SRAM UDH |
| Bottle Mount | Small & Medium: 1 (downtube) / Large & XL: 2 (downtube & seatube) |
| Rear Rack Reccomendation | Old Man Mountain Divide Fat |
| Rear Rack Mounts, Upper | Yes |
| Axle to Crown | 531mm |
| Steerer Tube Size | 28.6mm |
| Steerer Style | Tapered |
| Crown Seat Diameter | 40mm |
GEOMETRY CHART
| Small 15" | Medium 17" | Large 19" | X-Large 21" | |
| Effective Top Tube | 630 | 645 | 660 | 665 |
| Seat Tube Center to Top | 381 | 432 | 482 | 533 |
| Head Tube Length | 160 | 160 | 175 | 190 |
| Head Tube Angle | 69° | 69° | 69° | 69° |
| Seat Tube Angle | 73° | 73° | 73° | 73° |
| Chainstay Length | 480 | 480 | 480 | 480 |
| BB Drop | 60 | 60 | 60 | 60 |
| Reach | 420 | 435 | 445 | 446 |
| Stack | 688 | 688 | 702 | 716 |
| Standover Height | varies based on wheel and tire size | |||
| Wheelbase | 1187 | 1207 | 1223 | 1229 |
| Fork Offset | 51 | 51 | 51 | 51 |
FAQ:
| Can I use the Keystone in cold temperatures? | It is okay to use your Keystone in the operating temperature range, suggest by Shimano: -10 - 50°C |
| How do I remove the battery? | Each Keystone will come with a set of keys. Make sure to save your spare key and safe location. Insert the key fully into the lock cylinder on the non drive side of the downtube until it stops. Rotate the key clockwise until the battery drops from the downtube providing access to the latch release mechanism. Use your index finger to gently depress the spring which will fully release the battery. Use caution to support the battery when removing it so it does not fall to the ground. |
| How can I file a warranty claim for the drive unit and other electronic components? | Contact an authorized Shimano STEPS dealer. |
| Can I change my motor/power settings? | Yes, you can customize your motor settings via the app as well as update the firmware. You'll need to download the Shimano E-tube mobile app. |
| Can I change the max speed? | No. Depending on where you've purchased your Keystone it will either have a max assist speed of 20mph or 25km/h. This setting cannot be modified by the user or a dealer. |
| Can I purchase an extra battery? | Yes, you can purchase a spare battery kit with a spare downtube cover directly from Borealis. Spare battery kits may not be available in all markets. You can also purchase a spare battery from Shimano, but it will not include a battery cover. |
| Can I ride the Keystone without the battery? | No. This will void your warranty with Shimano and cause damage to the motor system. |
| Do I need to update the firmware / software? | Firmware can be updated via the Shimano E-tube mobile app. |
| How do I use walk mode? | Hold the upper button (down assistance level) for 1 second until the display turns blue and displays WALK mode. Press and hold the same button to power the rear wheel. |
| How long does it take to charge the Shimano 630Wh Battery? | With the included EC-E8004 charger, the battery can fully charge in 6 hours. |
| How long will my battery last? | The remaining battery capacity is affected by temperature and cycle count. Generally, it decreases approximately 5% a year. This means roughly 95% capacity remains after 1 year, and 90% after 2 years. |
| How should I store my bike and or battery? | Charge your battery to approximately 70% before storing for long periods of time. Store in a cool, indoor location with a stable temperature between approximately 10 - 20 C / 50 - 70 F. No direct exposure to sunlight or rain. |
| Are the electronic components waterproof? | Yes, the STEPS system is waterproof as long as all components of the system, including the battery and battery cover, are installed correctly. We recommend not using a high-pressure washer to clean your Repeater, but riding in the rain and regular cleaning are okay. |
| My bike won't turn on, what do I do? | First, make sure all cables are plugged in, if they are then try removing and reinstalling the battery. If it still won't turn on try charging your bike for a few hours. If your bike is too hot or too cold, it might not turn on. If your bike still does not turn on, contact a Transition or Shimano dealer for support. |
| Should I only charge my battery when it's completely drained? | No, simply charge the battery any time you need it, frequent charges actually help battery longevity. Avoid letting the battery discharge completely. Charge to 70% before storing for long periods. |
| What are the different error codes and what do they mean? | Whenever you encounter an error code, first cycle the power off and then back on. If the code persists, remove the battery and then reinstall, which will hard reset the system. If neither of these steps resolves the issue, please reference the Shimano error code list. If you cannot resolve your error code via your Etube mobile app please visit your nearest Shimano STEPS dealer or contact Shimano STEPS customer support. |
| What is the range and how can I maximize it? | There are many factors that affect battery range, such as, how much effort the rider is providing, the gradient of terrain, ambient temperature, and rider weight. The best way to maximize your range it to spend more time in Eco and Trail modes, and minimize the amount of time spent in Boost mode. |
| What is the widest tire the Keystone can fit? | 26x5.0" or 27.5x4.5" |
| What kind of maintenance is needed on the drive unit and how often? | The drive unit is sealed and cannot be serviced. If there are any issues with the drive unit, it will need to be removed and sent back to Shimano for service or replacement. The drive unit along with the battery is designed to last over 1000 charge cycles. Assuming you're getting 30 miles (48Km) per charge, the drive unit should last 30,000 miles, or much longer than pretty much any other part on your bike. |
| Why does my bike stop giving assistance over a certain speed? | Depending on where you've purchased your Keystone it will either have a max assist speed of 20mph or 25km/h. This setting cannot be modified by the user or a dealer. |
| Will environmental temperature affect battery life? | The battery life will be shorter during cold temperatures, this is not a sign of a problem. |
| Will my bike be delivered with a charged battery? | Your Keystone was shipped in a "sleep" mode with the battery at approximately 30% charge. It is recommended to fully charge your battery before the first ride. |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.4 ★★★★★
Based on 29 reviews
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Product Reviews
★★★★★ 5
Easy Approval Process and Great Rewards
I’ve had a very positive experience with the Amazon Store Card so far. The application and approval process was quick, simple, and straightforward. Managing the account through the Synchrony app has also been very easy, with a clean layout that makes it simple to view balances, make payments, and track purchases.
One of the best features is the 5% rewards on Amazon purchases for Prime members. The cashback adds up quickly if you shop on Amazon regularly, and the rewards are easy to redeem during checkout.
I also appreciate the special financing options that are sometimes offered on larger purchases, along with helpful account alerts and security features. Overall, this card is convenient, user friendly, and a great option for frequent Amazon shoppers.
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Reviewed in the United States on May 22, 2026
★★★★★ 5
Great card to have highly recommend
Like using the card for everything. 5 to 7% cashback credit is awesome.
No interest is even better.
I put almost all my purchases and bills on my credit accounts or credit cards and pay them off monthly.
Now that I'm a senior citizen I don't like to go to 20 different stores to find the best prices.
The card made my life less busy and I don't have to worry about paying for the many, many things I need right away. Even though I pay off all my accounts every month.
If I need a big ticket item, like a new flat-screen television I can get it and not worry about the cost by paying over time if I need to.
Having another credit account has also improved my credit score by the hundreds. I was in the 500s for decades until I started the secured card on Amazon. Now I am nearly at an excellent score in the high 700s and don't need secured credit cards.
I can use my account at Whole Foods and have my phone scanned for payment. It's just so easy to use
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Reviewed in the United States on May 6, 2026
★★★★★ 3
Credit limit drop without cause, Synchrony?
Hey Synchrony, I've about had it with your services, I have 2 cards I use through you through Walgreens and Amazon. You lowered My credit limit on both cards causing me to go over on one because of stupid interest when I had 500 left and I had quit using the damn thing, and my Amazon store card I just Made a 200 Payment on! Lowering my limit and leaving me blind, You should call your customers leave a voicemail or text for heck sake ill read them, I don't read my emails usually for 2 or three weeks, well you did it again, but this time to card I just paid 200$ on too!, Your company sucks, I hate your practices, and I want you to know that. I also want Amazon to know that!! I spend a Boatload of money through amazon, as does my entire family, all ya gotta do is look!! Well I have never felt more unappreciated, insulted, like I stole something or like dirt ever ever in my adult life like you made me feel. Like i'm doing something wrong. Well guess what Synchrony Bank? I'm not doing anything wrong, at all!! I've never been late or missed a payment with my Amazon card or any card I have with you, Synchrony. Your Faceless Corp in its infinite wisdom, decided it would be a great idea to screw over an actual good customer just because some stupid algorithm reported my credit limit was too high and I was a risk, and lowered my limit from where it had been for the last 3 years and then sent a Quiet email about a letter that you put on my online account, please read it, just like that, no Urgent header nothing not that. I don't even read my email that often. I DO read texts or my regular mail, or listen to my phone messages!! I meant what I said NEVER LATE not even once, and NEVER MISSED a payment NOT once!!! The ONLY time I ever had to deal with any kind of problem was the one that lowering my limit on my Mastercard were the cause of, Synchrony!!! when you dropped my credit limit without me knowing and I went over my new dang limit because interest charges were coming in!!! I new where I was and had it handled and would have been able to ride the storm but no you had to mess with my account. Oh and I dont give a Crap if you quote me "we have the right to raise or lower you limit whenever we want", It's a BS excuse to screw over your customers, I know about the terms, however in all of my 54 years, you are the only credit card company that has ever lowered a limit one a CC I had EVER! and I've dealt with some Super sketchy Dirtbag Why did I ever agree to this card, charge me for everything Companies. Mostly when I was young but not even they cut my limit, without me missing payments or being late .....Now 30 years later much older and I thought wiser better CC much better 2500$ limit I've had for years and expect that limit to stay in place or like my Prime Store Card 2000$ limit to stay in place!! not dropped by 500$, for hells sake!!!! Well today I get the old hey your payment option for your try before you buy order needs addressed, and why do you think that was? Hmmm? Well, Ill tell you!! Because you Dropped my limit, by 500$ Now if Amazon dropped it then Ill chew them out too, but I don't think it was them, cuz you did this on my Walgreens card too!!! I just made a 200 payment on my Amazon card as well jerks! Not one of the several companies ive had previous Cards with NOT Cap one Cred one, citi, Community bank, american express, discover you name it, and Ive probably had it at one time or another dozens upon dozens over my adult life at this point anyway. Well, not even the Sleaziest Dirtyiest Gutter Scum CC company with fees for just looking at your card has ever lowered my credit limit not in 34 years Especially when I wasn't late or missing payments ever, always been on time and never missed a payment not 1 time, Except SYNCHRONY, and I think you suck for that!! The only reason I gave 3 stars is Amazon doesn't deserve a 1 star review because of your company! I love amazon, I love their products, their deals their delivery Amazon Prime, im ride or die with Amazon, my kids do all their shopping on amazon they even use it for groceries and stuff occasionally, but I really, really don't like how you treat customers Synchrony, especially customers, that pay on time and even early, oh and on auto pay for Christ sake!!! Now I know why some young dumb kids and people say screw it and stop paying CC bills, cuz the Corporations that pass em out like candy to kids, I might add, are SCUM bags, thats why!! It's all about the GREEN, more, and more and more money its never enough!! Well, when you dropped my credit limit without me knowing and I went over the limit of a different card I had with you, it was because of interest fees coming in. I expected and knew about these fees, however, I also thought I had 500 more than I had available on my card!! What a great day that was, let me tell ya!! I didn't even miss a payment I just didn't make a big enough one to cover the interest that came in, and I also never just pay the minimum payment with these cards either!! Your practices are shady, and the crap you pull against loyal customers that pay on time and even on Autopay are so Scummy!! You know when you dropped my credit limit without me knowing and I went over my limit because of interest, I even reached out to my current lawyer about Bankruptcy choices and stuff and if I should deal with you that way, but I got over bein mad! You know if I was late all the time and a crappy customer missing payments I wouldn't blame you for anything and at least Id know my cards were lowered and probably locked ...but I didn't want to do that, I wanted to try and slide right back into auto pay and get back on track and to deal with a recent Identity theft issue im having and not stop paying my bills OH..yeah, you smellin what i'm sellin? Well because of some terrible thing I must have done in a Past life, I guess. Several months ago now when I was dealing with the death of my mom very suddenly. I also noticed my credit score started dropping and I had no idea why, well turns out i'm MR popular. I had all sorts of crap in my name most of it local where I live and surrounding locally. 100 points in like 5 months!! I digress, Whatever! I don't care anymore, cancel my cards if you want, I'm done! This world is goin to hell in a hand basket, Civil War is almost immanent, a Faceless mob can destroy peoples lives just by canceling them on the internet at a whim. When its true I agree with the mob but when there isn't any proof and someone's life is upturned and then it turns out to be a total lie or they said something 12 years ago and its dug up? Good God, I probably said some haynous stuff when I was 25, but I can assure you when I was 37 I was not that person anymore, my views had changed on many things,,,,that stuff is crazy, and so am I for thinking I can do a damn thing,,,, my mom died 5 months ago, I was just recently laid off from my job I had for 17 years last month, and now you drop my limit again when i've been on time and auto paying and almost screw up my Amazon account!!so screw it!! Eat It Synchrony Bank,Eat It! Sorry about 3 Stars Amazon.
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Reviewed in the United States on March 24, 2024
★★★★★ 5
Well made
I like that it’s lightweight very vintage looking
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Reviewed in the United States on May 17, 2026
★★★★★ 5
Well made & sturdy
Size: 6.5x10ft, Color: Red
I have it in the umbrella stand however I haven’t used it yet as it hasn’t been sunny where I live.
Once I begin to use it, I’ll update this review.
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Reviewed in the United States on May 15, 2026