Monday, January 31, 2011

Visit to MBS

Went to MBS again today, to try to solve the issue of the mysterious self-puncture of the tubes on my bike. After consulting KS and Joseph and Jai, the reason for the punctures is still unknown.

1) Bad batch of tubes: Possible but unlikely, since the tubes are different (SV6 and SV6A, one bought from CRC and one from MBS).

2) Rim tape: Although the rim tape seems ok, but it might not have been thick enough to stop the tubes protruding through the rim holes. Perhaps the tube has been stretched too much when it was pressurised and squeezed through the rim hole. Possible cause.

3) Overpressurization. Max PSI rated for the Kojak is 95PSI, but that is for the tire. The tube does not really have a max PSI rating. Usually I pump to 95-100PSI, have not had a problem so far for 6 months since I changed to Kojak. Possible reason.

To try to prevent a similar problem from happening again, an extra layer of rim tape was placed on the rim. This made the rim slightly bigger, and it made the mounting of tire really difficult. It was super tight and took a lot of effort and skill to mount the tire. Can't imagine what I would do if I get a puncture. Too difficult to change the tire already.

Right now the tire is pumped to 90 PSI. Shall not go above this next time. Hope the tube holds! It really worries you when the tube can self-destruct when the bike is just sitting at home. Makes you wonder when it will next blow.

The poor man's bike stand. Take care not to damage the rear derailleur!

Sunday, January 30, 2011

Rainy Days and Mysterious Tube Punctures

Been raining since Sat morning. Still raining here at Bukit Batok. Could not join Taiwoon and friends for the City Ride on Sunday morning because the rain was just too heavy. Apparently the weather at Lavender was pretty good, not raining at least.

Discovered that my rear tire was punctured on Sat night. Quite strange because I cycled a bit on Sat morning, and there was no problem. In the afternoon I checked the tires and found that they were alright. However at night just before I went to sleep, I checked the tires and found that the rear tire was flat!

Had to remove the rear wheel to find the cause of the puncture. Struggled quite a bit to get the tire off the rim, because its quite tight. Found that the puncture was on the inside of the tube, on the side resting on the rim tape.

Small cut, as can be seen from the picture above. Usually this will be due to the spokes poking through the rim tape, but then I checked the tape and it was perfectly fine. Also checked the inside of the Kojak tires as a precaution, nothing found. Luckily I had a spare tube, left over from the Pengerang ride. Before putting the new tube on, I also taped the inside of the rim with duct tape, for extra protection on top of the rim tape.

Put the tires back on the rims and the wheel back in the bike. Went to sleep, woke up at 5+am in the morning to check the weather. Still raining heavily. Had planned to cycle down to Lavender from Bukit Batok to join the ride, but the weather was just lousy over here. Went back to sleep instead.

Then today, on Sunday morning, I decided to take out my front wheel and put extra duct tape on the inside of the rim also, to prevent the same problem from happening. Again, checked the tires and rim tape, no problem. Duct taped the front rim and put back the tube and tire.

I was in my room in the afternoon, when suddenly I heard a pop followed by hissing. Didn't know what it was, so went out to check. Realised that the front wheel had gone flat! What is going on?

Removed the front tire and tube. Saw a long cut on the inside of the tube, somewhat similar to that of the rear tube but much larger.

This is really mysterious la, because the bike was just sitting there and it can puncture by itself. Once again, checked the tire and rim tape. Nothing detected. Also checked the inside of the rims for anything sharp, nothing found.

Decided to take out both my front and rear rims, tires and tubes, and make a trip down to MBS to see if anyone can help me solve this problem. Right now the rear wheel is holding up fine with the new tube, but I have let air out of the tube just in case.

Some possible reasons for the mysterious self-punctures:

1) Batch defect with tubes? Tubes are at least a few months old, tires even longer. Rims are less than 2 months old. Been through quite a bit of cycling on these wheels, no problem so far.

2) Wire bead of Kojak tire. The rubber on some parts of the bead has peeled off, leaving the bare wire exposed. But the wire is not sharp, and the cut was on the inside of the tube anyway, and not the side where the wire bead is.

3) Cold weather?

4) Tire levers may have damaged the tube when I tried to remove the tire. Unlikely as I have changed many tubes and tires before without problem, but still a possibility.

Summarizing the story, both my front and rear tubes have been punctured while the bike was just sitting there. Both were caused by cuts on the inside of the tube, on the side of the rim tape. Reasons for puncture might not be the same though. Hopefully the people at MBS can help me solve the mystery.

Friday, January 28, 2011

Journey of the Boardwalk: Part 1 (Kinetix Comp & Avid Brakes)

Shall now document the upgrading of my Boardwalk, from its humble beginnings to its current version, Boardwalk Z9, where Z stands for Zhng, haha.

Some pictures of the almost stock Boardwalk, with 7 speed cassette, Grip Shift, original brakes, and Dahon Neos derailleur. The saddle was the first to go, bought a Biologic Aria saddle, still using it even now. This was followed by the brake pads, switched to Gigapower brake pads.

One of the first components that I upgraded was the pedals. Very smooth and nice looking MKS FD-6 folding pedals. Still using these pedals now.

Soon the poison began to seep in. Out went the stock wheels, in came the Kinetix Comp rims and the Marathon Racers. Got the rims second hand, so it was a good deal. Together with the new tires, there was a significant improvement in the ride! These fast rolling tires and wheels enabled my top speed to increase by at least 5 km/h, even riding casually seemed to take less effort. Plus, the 3M reflective strip on the sidewall of the tires look good too!

Next, the brakes were changed. I did not like the mushy feeling of the stock brake calipers, which seemed to flex too much. Also, the brake levers had too much play up and down, and did not feel assuring. Found that the Avid Single Digit 7 calipers and Speed Dial 7 levers have very good reviews, and are reasonably priced. As a bonus they come with stainless steel hardware, so I no longer have to worry about rusting on the brake parts.

Again, this upgrade proved to be worth it as the brake feeling has improved tremendously. The brake levers feel very solid, and the brake calipers rotate very smoothly on its bushings. The levers also come with a red knob to modulate the braking power, where you can control the force transmitted to the brake calipers. In the end I did not use that feature as all, just left it as it is.

Most importantly, the brakes also look good! In the next part of the Boardwalk Journey I will be describing the switch to 8 speeds and also the Ergon grips.

XT Shifter vs X9 Shifter

Just got a new set of XT and X9 Shifters, and thought it would be a good chance to compare the performance of these shifters.

Test parameters:

Same cassette and chain is being used for comparison, albeit on two slightly different bikes. Shifting performance is based on shifting while in the repair stand.

Cassette: Custom SRAM 9 Speed Cassette, 12-13-14-15-16-17-19-23-28
Chain: SRAM PC-971/951 chain with Powerlink

XT shifter is paired with an Ultegra 6700 RD (Short Cage), while X9 shifter goes with the X9 RD (Short Cage).

Installation: Cable Routing

The gear cable for the XT is much longer than the one that comes with the X9, at least 50cm longer. This proved to have a big effect on the cable routing required.

Above, X9 shifter cable routing, and below, XT shifter cable routing

Note that for the X9 equipped bike, because of the short gear cable, the cable housing needs to be much shorter in order for the cable to reach the RD. This is despite the fact that the Ultegra RD needs a loop at the back for the cable to enter the RD.

Additional Info: XT shifter comes with a gear indicator, but it can also be removed if desired.

Installation: Attaching Gear Cable to RD

Much easier to connect gear cable to the Ultegra RD. Straight forward and visible. On the other hand, the X9 derailleur has an extra guide at the back to route the gear cable. Cable fixing bolt is hidden under/behind the RD, making it difficult to see and fix the cable.

Strictly speaking, this is off topic as its not about the shifter, but its something to take note when installing shifter and RD.


Downshifting means shifting to a lower (easier) gear, or in other words going to a larger sprocket. Downshifting for both shifters is accomplished by pushing the thumb lever (silver coloured).

Downshifting for the XT lever seems a little more laboured, as it takes more effort to push the lever compared to the X9 shifter. But this could be because of the different RD that is being used, perhaps the spring in the Ultegra RD is stronger than the X9 RD spring.

X9 wins in this case, as the shifting is pretty effortless, and X9 employs this technology called Zero Loss, which means that the lever engages the moment you push it. There is no free play before engagement, unlike the XT shifter which has a bit of free play.


Upshifting means shifting to a harder gear, higher gear number, smaller sprocket, what ever you call it. This is where the shifters are different.

The XT shifter uses a long black lever to actuate the upshifting. The cool thing about this XT shifter is that upshifting can be done either by pushing the black lever with your thumb, or pulling it back with your finger. Upshifting is fast for the XT shifter because Instant Release is used, where pushing the button releases the cable immediately. Whereas for the X9 shifter (and many other shifters), pushing the lever/button only releases half the cable, and only upon releasing the lever/button then the rest of the cable is let out.

SRAM Shifters also differ from Shimano and other shifters in that both up and downshifting are actuated by the thumb, while Shimano uses the thumb and finger separately. I personally like the thumb-thumb shifting, because its possible to downshift and brake at the same time.

On the other hand, some people are used to the Shimano thumb-finger shifting way and cannot get used to the SRAM style of shifting. I guess in the end its down to personal preference and adaptability, its not about whether one is better than the other.

General Shifting:

The XT shifters seems to be slightly slower in downshifting, while it is faster in upshifting. The X9 shifting is good up or down. Also, its much easier to calibrate the shifting for the X9 shifter, where the alignment is perfect all throughout the gears.

As for the XT shifter, the alignment seems to be slightly off at the lower gears, where cable tension is highest. It still works but not as good as the X9 shifter/RD combo. It may be because of the Ultegra RD, which seems to struggle a bit to reach the 28T sprocket.


No conclusion yet! Still need to test ride the bikes and try the shifting while riding the bike, will update once the testing is done! Meanwhile, more pictures!

The conclusion of "Shimano XT Shifters vs SRAM X9 Shifters" is now up! Read the second part here.