Brompton P Line: Stock Wheel Weights and Chain Ring Bolts

Although the Brompton P Line uses a titanium front fork and rear triangle to save weight over the regular C Line (similar to old M6R that I had), those are probably not the only areas where weight reduction can be found.

From my experience, there can be quite a lot of weight savings to be found from the wheelset and also the tires mounted on it. At the same time, I was curious about the 4 speed components used on the P Line, and wanted to take a closer look at them.

Most importantly, I didn't like the Schrader inner tube valves that came with the bike. All my other bikes use Presta valves, while my Lezyne Sport Gravel Floor Drive only has Presta pump head. Therefore it makes sense to have all my bikes use the same type of valves to avoid having to switch pump heads or use adapters. This means I need to change the inner tubes on the P Line to the Presta valve type, which will involve disassembling both wheels from the bike.

After removing the front quick release axle, a steel plate can be seen holding onto the hub axle. This is a secondary feature which prevents the wheel from falling out of the dropout if the quick release axle comes loose.

This axle retaining plate is not commonly seen on other front forks of other bikes, as the more common design is to have a raised lip to perform the same function.

The reason Brompton uses this design with an additional part is to balance the other side of the front fork, where there is a steel bracket to support the front hook.

Steel bracket with dual function: Prevent hub axle from falling out, and also to hold the bent steel wire bracket of the front hook.

Next, I removed the tires from the wheelset, as I wanted to check some specifications of the rims. The lightest 16" wheelset that I have used was on the United Trifold, where I upgraded the stock internal hub wheelset to the super lightweight Elosix wheelset which weighs only 951 grams!

Brompton P Line rim internal width is about 17.6 mm, which is a decent width and not too narrow.

For some reason I forgot to measure the external rim width and rim height, but I guess those can be measured easily without dismantling anything.

Tire weight is 220 grams which is decent as well, although not as light as the Schwalbe One which is just 174 grams each.

Stock butyl inner tube weighs 87 grams. I could save at least 50 grams per wheel by using lightweight TPU inner tubes, but the frequent tire pressure top up is not worth the hassle in this case.

New Schwalbe butyl inner tubes, which is slightly lighter at 82 grams each. They are of the Presta valve type which is my whole objective of changing out the inner tubes.

With the front wheel done, I moved on to disassemble the rear wheel. This is where it gets more interesting, with the 4 speed external drivetrain to be studied in more detail.

Rear derailleur hanger is made of aluminium, and looks well designed and made.

Removing the rear wheel is tricky, as it involves sliding the rear hub axle rearwards, where it is being blocked by the rear mudguards.

4 steel sprockets of sizes 11-13-15-18T, and secured by a Sunrace lockring.

The 4 sprockets with spacers plus lockring weighs 81 grams.

There is a plastic spoke guard at the back of the largest sprocket, to prevent the chain from going into the spokes if the rear derailleur low limit is not set correctly.

There is a 2 mm cassette spacer behind the largest sprocket as well. Different from the usual 1.85 mm spacer found on some Shimano cassettes.

The plastic spoke guard itself has a thickness of about 0.9 mm. This means there is additional 2.9 mm of space behind the largest sprocket in stock condition.

Stock rear quick release axle weighs 35 grams. It is basically an extra long bolt with a nut at the end, so technically not quick release as an Allen Key is required.

Front wheel weighs 447 grams, about 50 grams more than the super lightweight Elosix front wheel.

Rear wheel with the short freehub body weighs 628 grams, about 70 grams more than the Elosix version with full length 11 speed freehub body.

Finally, Presta valves on the Brompton P Line!

In conclusion, my verdict for the stock Brompton P Line wheelset is excellent. It is lightweight at 1075 grams for the front and rear wheels, and it is hard to go much lower than that. No point swapping out this wheelset unless you are looking for something different, like a flashy carbon wheelset (like what I did for the Birdy AXS).

I'm pretty sure the lower cost C Line uses a cheaper but heavier wheelset, but I can't be sure. Drop me a comment if you have more information on this!

Another small modification I did for the Brompton P Line was to change the chain ring bolts. As you may already know, for nearly all my other bikes (such as Birdy AXS 12 speed, Fnhon Ultegra Di2 12 speed, kids bike Bestrider Pump Pro 20), I used multi coloured chain ring bolts on the 4 or 5 arm cranksets, inspired by the Marvel Infinity Stones which come in 6 colours.

Stock steel chain ring bolt on the left is shorter than the usual 8.5 mm chain ring bolt (right) I use on my other bikes.

This means I need to use the shorter 6.5 mm chain ring bolts, but I don't have them in multiple colours.

Stock steel chain ring bolts (4x) weighs 18 grams. There is one hidden chain ring bolt at the back of the 5 arm crankset which I will not be swapping.

Due to the lack of shorter coloured 6.5 mm chain ring bolts, I used the longer 8.5mm coloured "bolt" for the front, and the shorter 6.5 mm "nut" for the back. Weighs 7 grams for a set of 4.

New coloured chain ring bolts installed! Only the 4 visible ones are changed, the hidden one behind the crank arm remains the same.

Picture of the Brompton P Line with the coloured chain ring bolts! Not obvious at first sight, unless you take a closer look.

Fnhon Ultegra Di2 12 Speed: Ascent Cirrus Elite Birdy Wheelset with Ashima Rotors

Two more blog posts to finish writing about the upgrade of the Fnhon Ultegra Di2 12 speed folding bike. The bike itself is already very good, however I decided to transfer some components from another bike over to this Fnhon bike. After all, we can't let a good carbon wheelset go to waste.

When I changed the wheelset on the Birdy AXS 12 speed to the Suncord 4 spoke carbon wheelset, the Ascent Cirrus Elite carbon wheelset was taken off the Birdy. Although the Ascent Cirrus Elite wheelset was meant to be a Birdy-specific wheelset, I realized that it can be fitted to normal folding bikes with the clever use of an adapter.

With an offset adapter for 6 bolt rotors, the brake rotor position on the Birdy-specific hub can be adjusted to match that of a normal front hub. That is the adapter that I will use to fit this Ascent Cirrus Elite wheelset (Birdy-specific rotor position) onto the Fnhon bike (standard 100 mm front OLD).

Note that the Fnhon was previously using a lightweight aluminium wheelset in 451 size, which was inherited from the original Fnhon DB12 in flat handlebar. This is the exact same Fnhon Tornado frame that was used to build the Fnhon Ultegra Di2 12 speed with a 3 way swap.

Now, the wheel size will be reduced to 406, since the Ascent Cirrus Elite wheelset is of a smaller 406 size instead of 451.

Ascent Cirrus Elite carbon wheelset in 406 size, with new tires and inner tubes ready to go.

New Panaracer Minits Lite tires in 32-406 size, exactly the same as what I am using on the Birdy AXS 12 speed.

A normal butyl inner tube weighs 104 grams...

...but a lightweight TPU inner tube only weighs 25 grams!

Ashima Ai2 super lightweight rotors! More holes than material on it. These have a diameter of 160 mm and 140 mm.

Here is the small adapter which is 5 mm thick, used to push the rotor position 5 mm outwards to make it compatible to normal bikes.

Adapter goes in between the rotor and the hub, to be fixed with a longer rotor bolt.

I used these black titanium bolts which needs to be longer than usual, due to the adapter. Bolt heads are rather big but still fits.

Rotor bolts cannot be too long either, or it will interfere with the hub shell or spokes.

Adapter sandwiched between the hub rotor mounting and the 6 bolt rotor. The rotor position is now at the standard position, instead of being 5 mm inwards as found on a Birdy.

Tires, inner tube, rotors all mounted!

Lightweight rotor ready to be tested

Ascent Cirrus Elite 406 carbon wheelset ready for installation onto the Fnhon Ultegra Di2 12 speed folding bike.

Since I was removing the old 451 wheelset and installing the new 406 wheelset, I decided to do a weight comparison as well. Not a completely fair comparison as some of the components are different, but it is an accurate representation of the weight difference due to this wheelset change.

451 aluminium rear wheel including tire, inner tube, rotor, weighs 1092 grams.

451 aluminium front wheel including tire, inner tube, rotor, weighs 970 grams.

406 carbon rear wheel including tire, inner tube, rotor, weighs 936 grams.

406 carbon front wheel including tire, inner tube, rotor, weighs 844 grams.

Overall, changing from the aluminium to the carbon wheelset (including change of tires, inner tube, rotors) saves 282 grams, which is pretty significant.

The wheel size is also reduced from 451 to 406, which means a reduction in overall gear ratio. That will be addressed separately through the drivetrain.

406 carbon wheelset on the left, 451 aluminium wheelset on the right. Big difference in rim profile and also overall diameter.

Ultegra CS-R8100 11-34T 12 speed cassette installed!

There is no issue converting the Ascent Cirrus Elite carbon wheelset from Birdy usage to general folding bike usage, all it takes is the small rotor adapter and some rotor bolts.

In the next post I will show the wheelset on the bike, along with some other changes to address the change of gear ratio due to the smaller 406 wheelset.

Birdy AXS: Suncord Wheelset Installation

The new Suncord 4 Spoke Carbon Wheelset was introduced in the previous blog post, now I will install the new wheelset onto the Birdy AXS 12 speed!

I will be transferring the Panaracer Minits Lite tires from the Ascent Cirrus Elite carbon wheelset over to the new Suncord wheelset. However, new disc brake rotors will be installed as the Suncord wheelset accepts Centerlock rotors instead of 6 bolt rotors.

Suncord rim vs the Ascent Cirrus Elite carbon wheelset, before removing the tire and rotor.

Big difference in appearance! The 4 spoke design makes the traditional spoke design look outdated.

Both use hooked rims, but the Suncord wheelset does not require rim tape as it does not have spoke holes on the rim bed.

Gloss vs matte carbon finish. Suncord rim height is 38 mm vs 45 mm on the Cirrus Elite.

Centrelock hub vs 6 bolt hub.

Tire and inner tube transferred over to the Suncord wheelset! Using the same lightweight TPU inner tube, which has a long 60 mm valve.

Putting on a used XTR MT900 rotor of diameter 160 mm.

Both front and rear rotors are 160 mm diameter. SRAM Force AXS 12 speed cassette installed on the XDR rear hub as well.

 

Suncord front wheel with rotor, tire and inner tube installed weighs 768 grams. Previous setup was 878 grams (+110 grams)

Suncord rear wheel with cassette, rotor, tire and inner tube installed weighs 1214 grams. Previous setup was 1285 grams (+71 grams).

After installing the new Suncord wheelset, I found that the chain is almost touching the rear triangle at Gear 1. There was a bigger gap with the Ascent Cirrus Elite wheelset.

Since there is nearly zero clearance, during movement the chain will scrape against the rear triangle and wear off the paint. Since all components (chain, chain ring, cassette) are the same, the cause has to be due to the Suncord wheelset.

It seems that the cassette is slightly more inboard on the Suncord wheelset, since there is still a noticeable gap between the 10T sprocket to the inside of the dropout.

Adding some spacers in the right places should solve the chain rubbing issue, this is not the first time I have made these kind of adjustments before. In fact I did a lot of adjustments when I was modifying the United Trifold folding bike.

Found some thin spacers for the freehub body. Intention is to place it behind the cassette to push it outwards slightly.

Left spacer is 1 mm thick, right spacer is 1.85 mm thick (the kind you put behind a 11 speed cassette when used on 8/9/10 speed freehub body).

XDR freehub body on the Suncord wheelset.

1 mm spacer placed on the splines, before installing the XDR cassette.

With the cassette installed, the silver 1 mm spacer can be seen sandwiched between the hub and the cassette.

However, adding 1 mm spacer on the cassette did not create enough clearance between the chain and the rear triangle. Since it is not advisable to add more spacers on the freehub body, I decided to add a spacer on the crankset instead.

These are smaller spacers that are designed to be placed on the Shimano crankset spindle of 24 mm diameter. Each spacer is 1 mm thick.

Used one piece of 1 mm spacer on the spindle of the Dura-Ace R9100 crankset. This will push out the chain line by 1 mm.

With both the front and rear chain lines pushed out by 1 mm, there is now additional 1 mm of chain clearance. May not be enough to completely eliminate chain rub, but at least it will minimize the occurrence and impact. 

Suncord 4 spoke wheelset has been installed successfully! Needed additional 1 mm spacers on both the crankset spindle and freehub body to push out the chain line slightly, but otherwise no issue.