Thursday, May 24, 2018

Tyrell IVE - Geometry and Folding Comparison with Brompton and Dahon

In the first part of this Tyrell IVE review, the overall bike features were shown, followed by the second part which studied the folding mechanism in detail.

For this third part of the review, the geometry and folded size of the Tyrell IVE will be compared to my two other folding bikes, the Dahon MuEX and the Brompton M6R. This will give us a good idea of where the Tyrell IVE stands when compared to a typical 20 inch folding bike and the super compact Brompton.

In my case, I did not resort to more precise measurements such as using a measuring tape to check the actual dimensions. It is more of a rough gauge by eye, to see if there are discernible differences. If I cannot find a difference by looking at it, then it is probably not different enough to be felt.

Starting with the 20 inch Dahon MuEX, which is equipped with 406 sized wheels, let's compare the bike geometry and the folded size with the Tyrell IVE.

Putting the bikes side by side first...

As always, I align the centreline of the bottom bracket to each other as this is the datum for the whole bike.

Rear end of the bike (at tire circumference) is almost the same, despite the difference in wheel size. 

As the Tyrell IVE has a longer chainstay, the rear hub axle is further back from the bottom bracket compared to the Dahon, which results in the rear length being similar even though the wheel is smaller in diameter.

As for the front end, the Tyrell IVE front hub is also slightly further in front compared to the Dahon. Overall, this means that the Tyrell IVE has a longer wheelbase (about +30mm) compared to the Dahon.

When folded, the Dahon is longer, as the 20 inch wheel sticks out more. The other end of the folded package is aligned for a fair comparison.

The Tyrell IVE has a wider folded package, as the handlepost folds outwards instead of inwards like on the Dahon.

Overall height of the Dahon is taller, mainly caused by the saddle sticking out on top.

Moving on to the Brompton, let's do the same thing and compare the geometry and folded size. At the end of this post, I will summarize everything and draw a conclusion.

Putting the Brompton and Tyrell IVE side by side. Tyrell IVE has a higher top tube and also has a down tube, compared to the Brompton which only has one large top tube.

Once again, align the centreline of the bottom bracket before doing any more comparison.

Tyrell IVE has a longer chainstay length compared to the Brompton, with an additional 20mm (estimated).

Can't really see it clearly here, but the front hub is at about the same position.

With the front hub in the same position, and the wheel sizes being similar (349 for Brompton vs 355 for Tyrell IVE), the front edge of the tire is at the same distance from the bottom bracket.

Comparing the folded appearance, the Brompton obviously looks neater, with no slanted angles like on the Tyrell IVE.

Folded length of the Tyrell IVE is longer, as the bottom bracket of the Tyrell IVE is behind the seat tube, as compared to the Brompton which has a bottom bracket in front of the seat tube.

For folded width, the Tyrell IVE is much wider, as both the handlebar and front wheel sticks out quite a bit.

Another view of the folded width comparison

As for the folded height, the Brompton and Tyrell IVE have the same height, with the saddle being the highest point.

Overall Length (front tire to rear tire)
Dahon (406 wheel) > Tyrell IVE (355 wheel) > Brompton (349 wheel)

Wheelbase
Tyrell IVE > Brompton > Dahon

Folded Length
Dahon > Tyrell IVE > Brompton

Folded Width
Tyrell IVE > Dahon > Brompton

Folded Height
Dahon > Brompton = Tyrell IVE

In summary, the Tyrell IVE has a surprisingly long wheelbase, which corresponds to the stability that I feel when riding it at higher speeds.

As for the folded size, the Tyrell IVE is shorter and lower than the Dahon, but wider due to its more clumsy fold. The Brompton comes out the champion again for having the most compact fold.

If you absolutely need the most compact fold, the Brompton is the choice to get. However, if you don't need the most compact fold, the Tyrell IVE is a good choice as it is cheaper than the Brompton, given the same spec (9 speeds vs 6 speeds on Brompton), is slightly more lightweight (11.5kg vs 12.3kg), but folds slightly larger. There are also other pros and cons, such as shifting, braking, which will be elaborated on in the next post.

From this comparison, you will be able to find the folding bike that best suits your needs, in terms of folded size.

For the final part of the review, I will share my opinion on the ride quality and other aspects of the Tyrell IVE.

Sunday, May 20, 2018

Polygon Cozmic CX3.0: 1x11 Speed Drivetrain

I hardly ride my Polygon Cozmic CX3.0 mountain bike (MTB), as I have many other bikes that are better suited for riding on the road. With the Canyon Endurace road bike, Java Freccia mini velo, Avanti Inc 3 commuting bike and the Dahon MuEX folding bike, I am spoilt for choice when I need a bike to ride fast on the road.

Of course, a MTB is meant for riding off road, but with the lack of good trails and good weather in Singapore, off road sessions are rare for me. Unless you stay near a trail or really enjoy riding off road, most people will choose to ride on the road as you can start your ride as soon as you are downstairs.

Nevertheless, I will still jump at the chance to upgrade the MTB if there are suitable components that constitutes an upgrade. The current setup is a 3x10 speed drivetrain with a mixture of Deore XT, SLX, and Deore grade components. All of them work well together as they are all from the Dynasys 10 generation of components.

Current setup of 3x10 speed drivetrain on the MTB. I found that the chain is a bit slack in the front low - rear top combination, but I did not notice it before as I don't ride in this gear combination.

Deore XT Trekking shifters SL-T780 with Deore brake levers BL-M615.

With a 3x10 setup, the gear range is wide. The Deore XT M780 triple crankset has a combination of 42/32/24T, while the rear 10 speed cassette is 11-34T. With a 26" wheel, this gives a low gear of 18.4 gear inches and a top gear of 99.3 gear inches. Having a low gear that is easy enough is always important for off road riding, where the terrain can be slow and steep.

However, the top gear of 99.3 gear inch is quite redundant on a MTB, especially if you only consider off road riding. My Java Freccia mini velo, which is a fast bike with drop bars, has a top gear of 88 gear inches. This is sufficient for 99% of the time except when I want to pedal downslope. With a cadence of 100 rpm at the highest gear, 37km/h is achievable on the mini velo. The gear range on the mini velo is perfect for me as I don't need a lower or higher gear ratio.

On this MTB, there is no need for such a high gear ratio, unless you plan to cycle fast on road. It is redundant to have higher gear ratios on the MTB than the mini velo, especially when the mini velo can go faster and yet rides perfectly fine with a lower top gear ratio.

Therefore, there are hardly any downsides to using a front double or even front single drivetrain on the MTB, as long as you can get a sufficiently low and high gear range that is suitable for off road riding.

Changing to a front single drivetrain is easy. The idea is to use just a single front chainring, and use a wide range cassette to get the range of gears you want. Increasing or decreasing the size of the front chainring shifts the whole gear range up or down respectively, depending on your riding ability.

With a front single setup, the front derailleur and front shifter is no longer required. However, you do need a special front single chainring to prevent chain drops, and a capable rear derailleur to shift properly across the wide range cassette.

The more speeds you have, the wider the gear range possible, without making the gear steps too big. At this point in time, the SRAM Eagle 12 speed system has the widest gear range, with a gigantic 10-50T cassette. However, it is also very expensive and requires a special XD driver freehub to use the XD cassette.

Going to 11 speeds is quite sufficient. With a 1x11 speed setup, you can also get a wide gear range that should be suitable for most conditions. A 3x10 drivetrain has about 14 unique gears, while the 1x11 speed drivetrain obviously has 11 unique gears.

After doing some calculations, I found that a front single chainring size of 34T, together with a rear cassette size of 11-46T will give me a suitable gear range. With this setup on a 26" wheel, the low gear is 19.2 gear inches, while the high gear is 80.4 gear inches. This range can be shifted upwards or downwards by using a bigger or smaller chainring.

3x10 drivetrain: 18.4 - 99.3 gear inches
1x11 drivetrain: 19.2 - 80.4 gear inches

With this 1x11 speed drivetrain, I have a low gear range that is almost similar to the one on the 3x10 drivetrain. At the other end, I lose 2 higher gears of 84 and 99.3 gear inches.

3x10 speed drivetrain on the MTB 

1x11 speed drivetrain on the MTB

As Shimano MTB 11 speed cassettes can be fitted directly on 8/9/10 speed freehub bodies, there is no need to change the rear wheel. Just remove the 10 speed cassette and install the 11 speed cassette!

Changing the crankset is also easy as the Hollowtech II system makes it so convenient to swap the entire crankset effortlessly. As for the rear derailleur, the mounting method is the same, using the Direct Mount rear derailleur hanger that is found on this frame.

1x11 speed drivetrain!

SLX M7000 crankset with 34T chainring

The gigantic 11-46T M8000 cassette! With a big jump of 37T to 46T in the lowest gear, it is more like a bailout gear when the terrain gets really steep.

Top level XTR M9000 11 speed rear derailleur to cope with the extra large cassette. Adjustment of the B tension screw is required to get the setting dialed in.

XTR M9000 11 speed shifter, with the super slim clamp band. Still using the Deore brakes as there is no need to change it.

Chain path when using the largest 46T sprocket. Looks really stretched out.

The rear derailleur looks almost straightened out! However, the chain cannot be lengthened any more...

When using the smallest 11T sprocket, the rear derailleur is almost fully contracted.

The chain is almost touching the guide pulley when using the 11T sprocket.

With this super wide range 11-46T cassette, the rear derailleur just manages to cover the whole range. The chain length is also just nice. It cannot be lengthened as there will be chain slack when in the 11T sprocket, and yet it cannot be shortened or the rear derailleur will be overstretched when in the 46T sprocket.

This 1x11 speed drivetrain setup simplifies everything. Shifting is easy as there is only the rear shifter to operate. With the low gear of 19 gear inches, it is sufficient for off road riding. As for the top gear of 80 gear inches, it has been tested and is also OK for road riding. At a cadence of 100 RPM, in the highest gear combination of front 34T and rear 11T, it will give a speed of about 38 km/h which is enough. On a mountain bike, this speed is only attainable on down slopes and is not sustainable on flat roads.

As for the gear steps, it is larger compared to using a road cassette. However, I did not feel that it was a big issue as compared to on a road bike. Not sure the exact reason why, but I guess it is because I am mostly using only the highest 3 or 4 gears when riding on road.

Wednesday, May 16, 2018

Tyrell IVE - Folding Mechanism and Design

Having done the brief introduction to the Tyrell IVE, here is a more detailed look! For today, we shall focus on the folding mechanism and folding design used on the Tyrell IVE. After all, this is a folding bike, and the folding design definitely matters a lot.

The Tyrell IVE is an interesting bike, as it combines the folding design from different brands, creating its own unique folding method.

For example, the rear triangle folds below the frame, similar to that used on the Brompton. The handlepost design is similar to the Tern design, with a long clamping length for extra stiffness. Handlepost clamp lever is a quick release type like Dahon's design, which is far easier to use than the Brompton type which needs to be turned. Finally, the Tyrell front fork also folds, which I think is a Tyrell original design, first seen on their Tyrell folding mini velo, the Tyrell FX.

Let's check out each of the folding components in detail!

Big red lever mounted on the left side of the handlebar, which is used to release the rear triangle from the frame. 

I have never seen a remote lever used as part of the folding mechanism, so this is new to me. If you press the lever during riding, nothing will happen as your weight still keeps the rear triangle and frame together. However, if you lift up the bike and press the lever, the rear triangle will detach and swing downwards.

Red lever activates the inner cable which runs to the rear triangle. This releases the latch that holds the rear triangle to the frame.

View of the metal latch on the rear triangle, which catches onto the frame. Activating the red lever moves the latch.

The part which the metal latch hooks onto. Although the black part looks like a rubber suspension (like on the Brompton), it feels quite stiff and probably does not flex much.

Roller wheels on top of the rear triangle, which supports the bike when the rear triangle folds below the frame. Design borrowed from the Brompton.

Metal rear fender with a small roller wheel mounted on top, which will also support the bike when the rear triangle is folded.

Small roller wheel in use. Small clearance between the fender and the ground, might have problems rolling if pushing the folded bike over uneven ground.

Initially, I was skeptical of the idea of having a remote lever activate the rear triangle folding mechanism. Is it worth mounting a lever, running an inner cable and outer casing all the way from the handlebar to the rear triangle, just to activate the folding mechanism? Not only does it add weight and complexity, it also adds additional cabling which will clutter up the bike's appearance. It could easily be replaced by a lever on the folding mechanism itself, similar to the Brompton design.

However, after using it for a while, I find it quite useful. For example, when I am rolling the bike along (unfolded), and I need to stop and park the bike, I just need to press the red lever and fold down the rear triangle. Since my left hand is already on the handlebar, right hand holding the saddle, it is super convenient to press the red lever and swing down the rear triangle in the same motion. There is no need to bend down and look for the folding lever, like on the Brompton.

Convenient? Definitely yes. Unnecessary? Maybe. A more low profile remote lever will probably appeal more to me. I will be fine with no remote lever at all.

After folding down the rear triangle, this is how it looks. Parking mode.

As seen from the picture above, the front wheel needs to be turned to the side to avoid the rear wheel. This direction is opposite from the Brompton, so I was initially confused until I figured it out.

Also, you can see that the the rear wheel actually ends up beside the frame, instead of directly under the frame like on the Brompton. This is partly limited by the triangular mainframe which cannot accommodate the rear wheel directly underneath it.

How does the rear wheel, which is initially aligned with the frame, end up beside the frame when you fold it? This is made possible by a rear triangle hinge that is angled towards one side, as seen below.

The special rear hinge that is angled to the side, allowing the rear wheel to swing to the side of the frame.

Although it is ingenious, I don't think it is an elegant design. From an engineering point of view, it is difficult to control the angle during manufacturing. Straight profiles are always easier and cheaper to manufacture, compared to special shapes or dimensions. That said, Tyrell does not do things the easy way, that is what makes them special.

Moving on to the front fork, I think the Tyrell folding front fork is an original Tyrell design. The Brompton has a folding main frame, just behind the head tube. With a folding front fork, the length of the folded package can be shortened. Let's see how it works.

Loosening the clamp will allow the bottom half of the fork to swivel down, with the pivot located at the rear as shown here.

There is a secondary pin that passes through both the upper and lower part of the folding fork. This prevents accidental folding if the front clamp loosens, which can be catastrophic.

After loosening the clamp, the pin must be pulled out, to allow the fork to fold.

The safety pin has a button at the end, which must be depressed to allow it to be pulled out or inserted into the fork.

Having the safety pin is a reassuring safety feature, however it can be quite easy to lose the pin, especially if you forget to insert it back after removing it during folding. Another problem is that the pin tends to rattle within the fork, as there is some free play. I had to use a rubber band to put some tension on the pin, so that it does not rattle when I cycle.

There is a plastic catch on the non-drive side of the rear triangle, which will be used to hold the front fork when folded.

Front fork folded, but not placed onto the plastic catch yet (located on the rear triangle).


Top down view. As you can see, the front fork rests on the plastic catch which is located on the rear triangle. This holds the front fork to the frame, preventing it from swinging open.

Handlepost design, with a chunky base that looks very similar to the Tern design. The lever design is something different from Dahon or Tern though.

The black block holds the upper part of the handlepost to the lower part when the lever is closed, by pressing it down firmly. It can be adjusted by turning the lock nuts on top and below of the black block.

One major advantage of having a tall clamp portion is that there is a larger interface between the handlepost and the steerer tube, which will improve the stiffness of the handlepost. Is it effective? This will be revealed in a later post on Ride Quality.

There is a small little metal stub on the other side of the handlepost. What does it do?


When the handlepost is folded down, the metal stub goes into the black plastic catch, which prevents the handlepost from swinging open. Similar in design to the Brompton.

With the front fork and handlepost folded, the fold is almost complete!

The final part of the fold is to lower the seat post, which works the same way as other folding bikes. Release the seat post clamp, and push down the seat post into the seat tube. For this bike, the fitting between the seat post and the seat tube is rather tight, therefore it takes a bit of force to push it down.

What is the purpose of this little plastic knob, and the strange semi-circle frame design?

The semi-circle frame design is to avoid the seat post when it is lowered. Some may call it clever, but I feel that it looks more like a workaround.

As for the plastic piece, it will rest against the seat post. This holds the rear triangle in place, instead of having it swing down when the bike is lifted. Similar to the Brompton design.

Final folded package. Quite wide and long, and looks quite untidy to me.

Side view of the folded size. Still looks OK.

As you can see from the folded package, the fold is not compact like the Brompton, neither is it neat like the Dahon. It has a relatively wide size, which also makes it harder to carry around. The folded size comparison will be done in the next post.

Although there are roller wheels under the bike, it is difficult to roll it around as it seems too wide, while steering it is also difficult. It is much faster and easier to carry the folded bike around using the top tube.

There are many little cutouts and special frame designs on this Tyrell IVE, with the purpose of enabling the fold without interference. Some people may like this kind of design, calling it clever, but I personally don't like it.

It feels like "since there is interference here, let's just create a depression on the frame to avoid the interference". This is done many times on this frame as I will show in more detail below. Not only is this not elegant, the special design also spoils the clean aesthetics and increases the production cost.

Depression on side of front fork. This is for fitting into the plastic catch on the rear triangle (shown earlier). Comes with a thick rubber patch to avoid scratches.

Depression on right side of down tube, behind the chainring. This is to avoid the rear tire when the rear triangle is folded down.

As shown here, the depression on the down tube is to avoid interference with the rear tire.

Another depression on left side of the down tube, near the headset.

This is to avoid interference with the front mudguard stays when the front fork is folded.

With all these special designs on the frame, the fold is made possible, although it is still not compact compared to the Brompton. Anyway, it works, although not in an elegant way that I would prefer.

The final thing that annoyed me is that the bottle cage bosses on the down tube is practically unusable. Although there are two threaded holes, and you can mount a bottle cage on it, you can't fold the bike!

When a bottle cage is installed on the down tube, folding is not possible as the rear wheel will interfere with the bottle cage.

Even if I just install the portable pump, the front mudguard stays will still hit the pump.

In summary, the bottle cage can only be used if the bike is not folded! You basically need to choose between folding the bike, or having a bottle cage BUT cannot fold the bike. This is quite ridiculous to me as this is a folding bike, and if you can't mount a bottle cage AND fold the bike, you might as well leave out the bottle cage bosses.

If the bottle cage prevent the full fold, but still allows the half fold (swing down rear triangle to park the bike), then it might still be acceptable. However, the bottle cage interferes with even the half fold, meaning that I cannot even swing down the rear triangle to park the bike.

Therefore, in the end I am forced to remove the bottle cage and pump mount as it just cannot be used together with folding the bike. The two bottle cage bosses are practically useless to me as I cannot use them. Do take note of this if you plan to mount a bottle cage on the Tyrell IVE.

With that, the folding mechanism and design has been shown. The next post will compare the folding design and geometry of the Tyrell IVE with my other folding bikes, the Dahon MuEX and the Brompton M6R.