The Dahon Curl I8 is one of the most ingenious and innovative bike designs of the decade, but its also very dangerous. I bought this Dahon Curl I8 to see if it would be a good, inexpensive alternative to my American made folding bikes I could recommend to people. The short answer, hell no!
Executive summary
Pros: An ingenious and innovative folding design makes it more compact when folded than any other bike. Its telescoping handlebar mast and seat post make it adjustible for both short and tall people. The Shimano Nexus-8 internally geared hub gives a great gear range for both climbing big hills and going fast on the flats.
Cons: Inadequate braking makes it very dangerous to ride at anything over a jogging pace. The manufacturing quality is poor meaning lots of trips to the bike shop.
Follow the money
It’s important you examine the motivation of people giving reviews of the Dahon Curl I8 as this review will no doubt be a LOT more negative than other you have read, why is this? Follow the money! When you google for “Dahon Curl I8 Review”, the first few pages of results will be from people who Dahon sent free bikes for review or from people who work for bike shops and are selling them. The people who get sent free bikes to review for free need to give glowing reviews or they will never be sent another bike for review. People working for bike shops need to give glowing reviews because their job is to sell bicycles. You will note that all these types of reviews show people biking around parking lots rather than in the real world under real world situations.
Me on the other hand, I buy my own bikes. I have been a travel bike enthusiast since the very early 1990’s when I bought on of the original BikeFriday New World Tourist travel bikes. I love bicycles and I love doing multi-week bike treks. I push my bikes hard and demand the ultimate in quality and reliability because I am often in desolate locations where a mechanical breakdown could be very serious. My goal is to get people to love bike commuting and bike trekking as much as I do and so I want to make sure they get the right bikes. I have owned two types of BikeFridays, one awesome Co-Motion, and this Dahon Curl I8 which I returned after owning it less than two weeks because of safety concerns.
Note: I have no affiliation with any of the bike companies mentioned on this page except as an ordinary customer.
Dahon Curl I8 – the good
This bike is a reverse engineered Brompton. Brompton had the market cornered when they introduced their innovate dual hinge folding bike. The problem is, their design is stuck in quicksand and the incremental innovation we come to expect these days is just not happening which left an opening for Dahon. Dahon look at the Brompton and made all the design changes that Brompton should have done years ago. The biggest problem with Bromptoms is the archaic drivetrain but also the fact that the handlebar mast does not adjust. The Dahon Curl I8 did an amazing job of bringing Bromptons design into the next century.
The folding is quick, easy, and it folds more compactly than any other bike. The wheeled bike rack that turns the bike into wheeled “luggage” is brilliant. The fact that its an internally geared hub means you never have to touch the chain when you fold it and it never comes off. Unlike the main hinge of a Brompton that rattles and makes you a bit uneasy, the Dahon main hinge is solid.
The handling of the bike is pretty amazing. It feels almost like a road bike and the steering is solid. Going up steep hills, it is extremely well balanced when you stand on the pedals to honk up the hill. Count on a top speed of about 22mph at 80rpm in the 8th gear, way too fast for safety on this bike but more on that later. If you pump up the tires to 100psi and ride on really smooth pavement, I would estimate that this bike is only about 20% less efficient than a good road bike. By 20% less efficient what I mean is that if you put the same number of watts of energy into the pedals of a Dahon, it will go 20% slower than the same amount of power being put into the pedals of a road bike. Given its a folding bike with tiny tires, the fact that it approaches the efficiency of a road bike is pretty remarkable.
Dahon Curl I8 – the bad
The Dahon Curl I8 has the feel of something that was rushed into production. You can tell that they have not got everything sorted out yet. The manufacturing process for the rack, which is one of the major selling points of this bike, clearly has not been perfected yet. Whatever jig they are using to bend and weld it is not right because to assemble the wheel axle onto it requires the rack be bent.
Worst is the wheels. There are two kinds of wheels, machine made and hand made. Normally cheap bikes come with machine made wheels where the spokes are installed and torqued by a machine. The wheels made this way are OK but not nearly as good as a hand made wheel by an experienced bike mechanic. The Dahon Curl I8 comes with hand built wheels which you might think is a good thing but not in this case because the person building the wheels is clearly has no idea what they are doing. My wheels were delivered true but with some spokes that had no tension on them at all and some others that were over tensioned. What this means is that unless the wheel is completely rebuilt and all the spokes replaced, the wheel will never be reliable. In fact, if you look at a lot of the customer complaints you will see that its because of wheels falling apart for this very reason.
The smaller diameter the wheel, the more sturdy and bulletproof it is. I have owned two BikeFridays with 20″ wheels shipped to me directly from the Oregon factory. Both bikes lasted more than a decade without needing a single wheel truing despite constantly carrying heavy packs on the cobblestone streets of Europe. The fact that the Dahon requires that you get the wheels trued by a bike mechanic to “activate the warranty” is completely ridiculous cover up of their horrible quality.
If it was just the wheels and the rack, I would just replace those with quality ones from my local bike shop because the design is so cool that it is worth it. The problem is that there is a dangerous design defect with the brakes.
Brake 101
There are two basic kinds of brakes – rim brakes and disk brakes. Rim brakes have the advantage of being cheap and very light weight but the disadvantage of being far less effective when wet or when they get hot from prolonged braking. Disk brakes are much more bulletproof but they are more expensive and heavier. Disk brakes have better stopping force as well as being unaffected by water or heat-fading.
The Dahon Curl I8 uses rim brakes. The stopping distance with rim brakes is determined by a number of factors:
- the weight of bike+rider. Weight is proportional to stopping distance. A 200 pound rider will take twice as long to stop as a 100 pound rider.
- the distance from the axle to the rim. A given rim brake can apply a fixed amount of friction. The stopping torque of the brakes is proportional to the radius of the wheel. Using the same brakes, the tiny 16″ wheel of a Dahon Curl I8 will take nearly twice as long to stop as that same brake put on a road bike.
- the presence of water. Water drastically increases stopping distance with rim brakes, twice the stopping distance when wet is a good benchmark
- the slope of the road. The steeper you are going downhill, the harder it is to stop – pretty clear. What is not so clear is how rider weight interacts with the slope. While a 100 pound person could stop safely doing down almost any slope, a 280 pound person could literally find themselves unable to stop at all going down a moderate 6% grade.
The problem with Dahon brakes that makes the braking dangerously ineffective is the short distance from the axle to the rim and the very high load limit of the bike (280lbs). Remember that stopping distance is proportional to weight. Going downhill, the effects of the weight are even more drastic. Because of this issue, other bikes in this 16″ wheel category responsibly limit the weight to about 190lbs. Even that I feel is too high.
I nearly killed myself on the first ride up my local hill by flying off the side of the road. The ride up was awesome but on the way down I found the brakes frighteningly ineffective and my stop took a scary-long time even though the pavement was dry, the slope only 5%, and I am only 220lbs when the bike is spec’ed for 280lbs. In that same spot, my mountain bike stopping distance is 1/5 that. Dahon either needs to put disk brakes on this bike or make it clear that:
– it is not designed to be ridden on hills
– it is not designed to be ridden over 10mph
– it is not designed to be ridden when pavement is wet
– it is not designed for anyone over 190 pounds (current limit is 280)
This inadequate braking is nothing that a bike mechanic can fix, its a defective design. The brakes should NOT be rim brakes, they should be disk brakes.
Here is a test on a 5% slope showing the braking effectiveness of the Dahon Curl i8 as compared to a basic mountain bike with cheapo mechanical disk brakes. The mountain bike stopped in an impressive 2.0 seconds. The Dahon Curl i8 on the other hand kept going and going and going despite a near death grip on the brake handles and took a whopping 21 seconds to stop. The way I did this test was to start rolling down hill at the same point, built up speed, then applied the brakes at a pre-determined point. The speed at the time of braking was approximately 20mph. Here is the video:
Now, you might be thinking “whats the big deal? It still stops doesn’t it?” True that. The problem is that the world is not an orderly place. Because the braking on this bike was so pathetic, I knew to start applying the brakes 30s before I needed to stop. The problem is that in the real world, emergencies happen all the time. Cars routinely run red lights and blow thru stop signs. When you have good brakes like a mountain bike has, you can stop in 2s and live to curse the driver out. On the other hand, the pathetic braking action of the Dahon Curl i8 will just allow you a few more seconds to review your life before you get crushed by their car.
Dahon Curl I8 – recommendations
The Dahon Curl I8 is one of the most ingenious and innovative bike designs of the decade, also the most dangerous and suffers from poor qualtiy – dont buy it.
A Dahon Curl I8 is about $1600. For $300 more you can get a bike that is much better quality, is much safer, is custom built for your body, AND is made in America. The Bike Friday Diamond Llama Disk 24 is the bike I would recommend instead.
More about biking and bike touring
folding bike buyers guide
Best bike tours in China
Lower stress with bike commuting
Bike touring
Full Dahon Curl i8 review video on YouTube
Safety concerns raised to Dahon and Sports by Sager
On August 14, 2019 when I returned the bike to Sports by Sager who sold me the bike, I notified both Sports by Sager and Dahon of the safety problems with this bicycle. As of September 5, I have received no response from either Dahon or Sports by Sager and neither the Dahon website nor the product description on amazon.com has not been corrected to warn consumers of the serious safety issue about braking as I suggested above. Here is the email I sent them:
Date: Wed, 14 Aug 2019 11:56:12 -0700
Subject: Safety issue with Dahon Curl i8
From: Scooby Werkstatt
To: [email protected]
Cc: [email protected]
Hi Gary,Not sure if the Amazon messages are getting thru to you but this is in regarding the return of my Dahon Curl i8 order number 114-6445553-5136269. I am copying Dahon on this because there is a serious safety issue that they need to resolve.
I completely understand your return policy where you only refund 50% of the purchase price; however, in this case I feel that Dahon misrepresented the bikes capabilities in stating that it was appropriate for riders up to 280lbs. I am only 220lbs and found the braking so inadequate that it was too dangerous to ride at anything above a slow jog pace.
I have written a review that fully explains the issues, its on page 1 of the google search “DAHON CURL I8 REVIEW” or you can find it here:
https://scoobyswork.shop/2019/08/13/dahon-curl-i8-review/When Dahon fixes these quality issues and the braking safety issue, I will gladly buy the Curl again and review it because it is truly a remarkable design.
Sincerely,
Scooby Werkstatt
Update
So I did hear back from Sports by Sager and below is their response. They are completely unconcerned about the safety of the bikes they sell as is made completely clear in the following email I received from them:
From: Gary Snellenberger <[email protected]>
Date: Fri, 6 Sep 2019 08:32:02 -0400
Subject: Re: partial refund of Order# 114-6445553-5136269
To: Scooby Werkstatt</[email protected]>Scooby,
Amazon has policy for used items and returns, you were fully aware of
this prior to returning the bike. The bike was to be taken to a bike
shop for assembly and inspection prior to riding it to validate the
warranty. This was offered to you 3 different ways. In the owners
manual, in the 3 sheets of paper with assembly and warranty
information we put inside the box that were returned to us and printed
on the box.This is a very expensive bike, weather you feel it is safe or not is
really irrelevant. We follow the Amazon policy and expect buyers to
do the same.
The bike was returned in a used condition and we can not sell this as
new, therefore the transaction was processed within the Amazon
guidelines.Sincerely, Gary
There you have it, the safety of the products they sell is not relevant. This seems to be an odd, and potentially very expensive attitude for a sporting goods store to have. I hope Sports by Sager has really good attorneys on retainer.
Purchasing a bike online
Please see my article about “buying a bicycle online“.