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The Cycle Clinic

Open Monday to Sat 9:30am till 6pm.

18 Oct

Aero test BORG50C are in.

Posted by Bold Apps
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Full details here. Test published by Hambini Engineering. 

Most aero tests have issues. A wheel or a wheel in a bike is tested with or without a dummy or rider. Sometimes with half a dummy. All these differences affect the significance of the overall result as it is impossible to tell the overall effect of the wheel in the system as a whole. Not to mention the air flow around the wheel is affected by the presence of a fork or the absences of it. 

Sometimes the wheels are static and a spinning wheel behaves differently to a static one. 

The final problem and this is a big one all aero tests you see are done by running the air flow at 50kph for a time at a static angle. Stop recalibrate and reset at the next increment. This does not predict real world conditions

As you ride the bike rocks, the front wheel and changes direction constantly. The changes in direction are small but if the front wheel did not do this you would fall over. Also when you pass gaps in hedge rows or buildings, even when cars pass on busy roads the airflow will osscilate sometimes widely.

Most wind tunnels don't simulate osscilating airflow. All this, means the results from most wheel aero tests are not that informative because the wheel behaves quite differently when the airflow oscillates and therefore behave differently in the real world. For starters you can spot the wheels that are at risk of speed wobble this way.

So when an engineer at airbus started testing wheels in there wind tunnel as an after hours project my ears pricked up. First the protocol has the air flow ramping up from zero degrees and holding at an angle for 15secs but oscillating +/- 2.5 degrees. A wheel is in a bike with a rider on it. The test is consistent for all wheels.

The error is +/- 2.5% 

The protocol was determined by 6 month of rider monitoring. 

 

 The above data is from the test rider riding down a straight road in the west country at constant speed. The yaw angle is anything but constant. 

So from lots of data gathered on yaw angle vs speed gathered from time trailists averaging 50 mph and road cyclist average 30 kph a protocol has been determined. The protocol does not represent one ride or how your wheels perform on a particular ride under certain wind conditions. What it does is sum wind conditions experienced over 6 month of U.K riding and therefore simulates how your wheel performs over a wide range of condition that would be experienced riding the wheels over a whole year. So this is more like giving a car mpg figure but for a bike.

The test is conducted with a rider on a road bike (the same bike and rider) in a road position (on the hoods). Below is an exaomple of one of the test protocols. 

The testing protocol is very different to manufacturer tests. It  mimics real world riding conditions in the sense it models transient (oscilating) air movement. Emphasis is placed on wheels which handle the separation and reattachment of airflow efficiently, very little emphasis is placed on riding a bike straight into a head wind at zero degree yaw - this is not realistic so why bother testing it. The wind tunnel used was temperature and humidity controlled.

The results

The figues for the BORG50C wheel with the reference Continental GP4000sII 23mm tyres fitted is 186W at 30 kph and 597W at 50 kph. I dont know about you I can't hold 50 kph on my road bike for very long. the 600W output for me is quite realistic. Remember the error is 2.5% so at 30 kph, the error is 4.675W so frankly the wheels that test better are within the margin of error. Also what is clear depth is king. Although profile is important too. 

So at 30kph all the wheels in the from about 183W to 186W are as good as each other. Cost spares availability, ease and cost of repair do vary though. 

If the rim is two blunt that increases drag although cross wind stability maybe better. 

What the detailed results show is most wheels show speration of air flow at 12 degrees yaw. The BORG50C is no different. That's physics. Some blunt profiles can extend this to 14 or 15 degrees but at the expense of drag. Those blunt wheels have one big problem once the airflow seperates it does not reattach well. 

What is shown in the detailed results is some wheels deal with the air flow flutter better than others. Mine do quite well, the wheels that don't deal with it poorly. Thats down to the profile. 

So in short for £800 the BORG50C is really a very good wheelset and has all the charastistics you need. It also benefits from a life of the rim warranty against faigue failures and manufacturing defects. The wheels are repairable as every spare is available and I will do it here for sensible money. 

 

10 Oct

PTN - Pepi's tyre noodles

Posted by Bold Apps
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October 6th @8pm saw the start of the One night in Thetford 12hr MTB race. It was also the first race outing for me using PTN - pepi's tyre noodles. The bike is an Orange stage4. the wheels have 35mm wide rims (29mm internal width). The tyres I use are IRC Mythos 29x2.1". On these rims they inflate to 54mm wide at 20 psi. The course was typical Thetford, dirt single track. With the small sized PTN fitted which was not too difficult and the normal load of sealant I was able to run 15 psi front and 18 psi rear which diffcultly. I normally run 22psi front and 24 psi rear. I did raise the pressure later in the race to 20 psi front and rear to see what that was like. I think I preferred the higher pressure on this terrain but the bike felt more stable than it does normally without PTN. Inserts work best if they fill a big proportion of the tyre volume like PTN does. Not only are the tyre sidewalls better supported allowing lower pressures to be run, the spring rate vs displacement is changed. The result are tyres that stay in more contact with the ground. You notice this more in ruts. Ruts with a tubeless setup without PTN can throw you off and down to the ground quite easily if you catch them wrong. With the insert if you catch the rut edge you can just ride up and over without issue. Essentially PTN makes it feel like you riding wider tyres. 

Which PTN?

There are three models now.

Race line, Rokkline and Revolution. They rank in order of stiffness with revolution being the stiffest. 

Revolution is therefore suited to gravity, enduro XC and CX use. The last is important. A small tyre need a firm insert so the air pressure does not squish to nothing. Revolution is the most impact reistant as well. It suits heavier riders  and E bike user more than the other two. Revolution has the best runflat potential and like most insert stops burping. Revolution allows the lowest tyre pressures.

Rokkline is the most versitile. Given its construction and material used it has excellent damping abilities and is impact resistant. It is diifuclt to break or tear it. It allows you to run your tyres flat with control and stops burping. It is well suited to XC riding as well as enduro riding. The stiff insert allows the rider to tune the feel of the bike with a wide variety of air pressures. Rokkline is the choice when the trails get narly. Its allow you to be faster than raceline over this sort of terrain. 

Raceline is the lisghtest but the least impact reistant of the three. The larger sizes are robust and suitable for enduro use but the rokkline or revolution will allow lower tyre pressures. Therefore Raceline I think is best suited to XC use and are East Anglia its all I need.


https://thecycleclinic.co.uk/products/pepis-tyre-noodles-ptn

22 May

Tubeless tyre and rim compatibility how to fit them and make it work.

Posted by Bold Apps
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Why tubeless, well lower pressures, more grip the possibility of self sealing punctures are all reason to use them. More space in your back pocket for important stuff like good is another. Gone are the days were I head out with 4 tubes in my back pocket. I am that unluckily.

Tubeless tyres have been around for a long time. Airliners landing gear have tubeless tyre at over 200psi so it not like tubeless tyres can't hold high pressures. While low pressure MTB tyres are more forgiving on the rims that can be used, the higher pressures in road tyres and the smaller air volume necessitates tighter tolerances. This is what this page is about. This is a generic tubeless tyre guide which is not brand specific or bike type specific. Tubeless tyres when done right are not faff. The faff starts when your setup is not really tubeless compatible.
What is tubeless compatibility?
Well think of a car wheel. When a car tyre punctures and flats, the tyre does not unseat from the rim. This is important because tubeless means tubeless all the time not done of the time.
A tubeless tyre that has flat but remains seated can be fixed externally most of the time permanently. This is alot easier if your not having to try to get the tyre seated at the side of the road.
A tubeless compatible retains the tyre well enough that it can be ridden flat or with very little air (5 to 10 psi) . Having done this for 10 miles then reinflating the tyre after fixing it, it certainly is a useful get out of puncture jail free card.
So what is about some rims that retains tyres while other let the tyre unseat with no pressure. Well let's start with a rim cross section.
The two images are of a Kinlin rim and a Mavic UST rim. Both are very tubeless compatible. All tubeless rim have the centre channel so when the tyre is mounted it sits in here. When you initially inflate the tyre is forced up to the larger diameter shelf. Now if the tyre is mounted to the Kinlin rim the bead moves under the bead hook and cannot unseat because the shelf is not flat. A Mavic UST rim use a bump next to the channel to ensure the tyre cannot unseat.

Mavic UST 

 

 

BORG/Kinlin XR22T/26T/31T

I hope you see what is in common. The rounded well sized bead hook that does not cut into the tyre and the uplifted inside edge of the bead hook is also an important characteristic. 

Sadly not every rim conforms. Here is a rim without these features. The tyre maybe retained but only by friction. This means if you have to plug the tyre it might unseat on you. Personally this sort of rim is not one I would define a tubeless compatible. You can run them tubeless of course but I am picky. The bead hook on this rim is also a bit small.

So the guide covers both types of rims. Those that retain the tyre and those that don't. Of course it is assumed you are using a tubeless compatible tyre. If your not and get faff well that was your choice.
Making your tyres tubeless compatible. If you have a tubeless compatible rim that has spoke holes you will need to fit tubeless tape. Two complete layers is required normally. Some rims can be a bit undersized and need more layers. More layer will normally insure the tyre retaining features do your back to friction alone holding the tyre in place. The tape should be pulled tight when fitting and pressed in place ( I use my thumb) do that the tape is bubble free and conforms to the rim.
On rims with deep channels this is harder to achieve than on rims with shallower channels. Of course a deeper channel can make tyre fitting easier. Next make a small hole with a sharp point coming up from the valve hole. Then using the closed presets valve push it through the tape and use a rubber mallet to tap the valve in place. Thread the collar tight and bingo the rim is sealed. The tape should be 2 to 4mm wider than the internal width depending on the depth of the channel.
How to mount a tyre and what to expect.
A tubeless tyre on a tubeless compatible rim should be fairly tight. As a rule of thumb if it can be mounted by handed it's probably too easy. First Make up a bottle of dilute soapy water and dribble over the rim. This is essential as it get everywhere. Mount the tyre and chase the slack before using tyre levers. Fitting the tyre dry is a mistake as if it tight you can damage the bead and end up with the join between the bead and the tyre carcass failing and separation. The tighter the tyre fit is the more secure it will be. This is a good thing.
Once the tyre is mounted, inflate. If a floor pump does not get the tyre up, try compressed air. A CO2 cartridge will also work. The tyre should seat and seal. Not all tyre Tim combination pop and ping when this is achieved. Inflate to a pressure where there are no low spots in the tyre. Let the air out. Then remove the valve core and inject 40ml if sealant for a 25ml tyre. Bigger tyres can use more. Then inflate again. If the rim retains the tyre this will be clean. If the rim dies not retain the tyre s tight fitting tyre means you won't have to use compressed air to reinflate and that less messy and better for the sealant.
Which sealant I hear you ask. There are three kinds.
1) latex free sealant
2) natural latex sealants.
3) artificial latex sealants.
My own experience tells me latex free sealants are useless. I use Effetto Mariposa or Maxalami sealant. Orange seal is good too. Stans is a mixed bag. It shall upto 30 psi. Beyond its hit and miss. Stans race cannot be reliably inject through the valve stem as it blocks it. Stans also forms latex balls which tyres have to removed which bring faff.
Now you should not be relying on the sealant. Its not going to seal everything. You also may find one day, as I have that the sealant had dried up and then you puncture and the tyre leave you feeling flat.
Now if your tyre is not retained by the rim or weakly retained, your best of packing a tube, a portable set of pliers ( to get the valve collar undone) and levers.
If your rim retains the tyre and if it is hard to push of by hand, don't bother packing a tube as you may find very hard to get it in anyway. Instead carry tyre plugs.
These tacky butyl rubber fibrious strips can repair a tyre permanently or fix a big slice well enough to limp home. Carry what I do, 1.5mm and 3.5mm thick plugs. Most punctures can be fixed permanently with these. If the plugs wants to push out use a lower pressure to get home. often the sealant will glue the plug so after 24hrs it can be more firmly held to allow normal pressures. If you get a 1cm sidewall slice then don't fret. A big plug or two can seal the hole and inflate to a low pressure and get home if somewhere safe. You'd be surprised how far you can go on 20 psi with plugs sticking out of the side. I carry a blade to cut the fat worms down before inserting. The MaXalami tubeless repair kit Had the two thickness of tacky plugs. You may think that the fat plugs are for MTB tyres and that's what the manufacturers say but I have found otherwise.
Through the life of a road tubeless tyre I generally end up with plugs shoved in the sidewall through the tread and they are in there for a few thousand km. I should really stop riding road tyres off road and down filthy lanes in winter but really where the fun in being sensible.
My tyre is deflating or loosing air over night? 
First of all check the simple stuff. Remove the valve core and seal up the the seal and reinsert. Check the collar is tight. If this is the case and the tyre is not holed you can do one of two things.
1) if your confident your taping is good add fresh sealant. This can seal up small holes in tyres.
2) leaks can be caused by poor taping. Time to do again.
Some tyres are porous though. There are two standards of tubeless tyres. One with a burly or latex lining. These should hold air well and sealant should last a good while in then. Then here are the tubeless eeasg tyres. Some of which hold air well but some dont. The tyres that leak air cause the sealant to dry up quickly and the latex can ball up. So come puncture time it's not there to help. 
One final thing. Leave a tubeless tyre in place. It takes very little bead stretch for it be difficult to refit so remove only if you really have to.
Tubeless tyres are not to be feared and if you do encounter faff it's probably user error. This guide has been written because I have learnt the hard way so you have an easier time.
Read this blog post on how to fix tubeless tyres at the road side. 

 

12 May

New IRC tyres - Gravel and road.

Posted by Bold Apps
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IRC have two new tyres coming. The first is the IRC Boken. This is a 700c 36mm or 40mm wide gravel tyre for that adventure rider in you. 

The thread pattern and compound means there is a good grip. Various local testers are tyring them out at present and I have many sample tyre here. If you want to try them for the cost of fitting I can let serious gravel riders have a go. The more feedback I get the better.

IRC Roadlite X-guard is IRC's latest road tyre for inner tubes. It has a dual compound and a puncture protection belt. The centre compound is harder than the one used on the tyres shoulders. So low rolling resistance in a stright line but when banking there is grip. The casing is nice and supple too. 

 

10 Apr

Campagnolo 12 speed is here

Posted by Bold Apps
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Campagnolo are not stuck in the padt. In may (expected) the first record and super record mechanical 12 speed groupsets will arrive. This shop has one if each reserved. More can be. If you want one read on and contact the shop for pricng. Prices are similar to the current groups. The disc brake and EPS components will be released later in the year.

 

The Super Record groupset is the best Campagnolo mechanical transmission. It is the choice that even top professionals rely upon for improved performance, reliability and precision.

The Super Record groupset is also extremely lightweight yet very durable. This new 12 speed incarnation is the very pinnacle of Campagnolo® innovation and the technologies, materials and craftsmanship with which the groupset is built, put it in a category of its own: Super Group.

Ergopowers

Campagnolo shifters have always been a one of the most innovative parts of the group set due to their near-perfect ergonomics. Campagnolo have refined the 12x models even further, slightly angling the brake lever blades to allow for greater braking control over rougher surfaces. The curve in the blade is more pronounced, offering greater comfort and aerodynamics. The groups are made even more accessible thanks tothree levels of adjustment where the lever can be set for riders with a different reach. The hoods have also been given an update and the Vari-Cushion technology has been further improved allowing Campagnolo to create a hood with different thicknesses giving greater grip, comfort and water dispersion. The shifters have also been enlarged for greater shifting control, with the upshift lever being brought closer to the brake lever blade creating a more aesthetically pleasing and easier to use shifter.

Inner and Outer Cables

Campagnolo have manufactured completely new inner and outer cables. The new versions drastically reduce friction and ensure a much longer life. Braking and shifting is impressive thanks to the new technology. Smoothness is maintained even when internally routed through the handlebars.

Front Derailleur

The front derailleur gives quicker and more immediate upshifting thanks to its new design and trajectory angle. The front derailleur also uses a dual position cable grip bolt to allow for use of tyres up to 32mm following current market trends. The inner cage shape has also been re-designed to enhance shifting fluidity and allow for accurate and fast movement.

Rear Derailleur

Dramatically different and elegant design for the rear derailleur produced in an ultra-light technopolymer with reinforced long strand UD carbon fibre. 3D Embrace technology is huge step forward from current derailleurs function. When you see how the derailleur shifts, you’ll notice that the jockey wheels are incredibly close to every single sprocket giving smooth, instant shifts and maximum efficiency. The derailleur also weighs less but maintains the same rigidity and durability. The trajectory curve has been optimized for 11-29 and 11-32 cassettes. A new upper body return spring has been redesigned to absorb road vibration and protects the derailleur from violent movement on the road. It can also fit direct mount and and standard systems making it easier to remove the wheel during the maintenence..

Cassette

With the additional sprocket on the cassette the need for a range of cassettes is eliminated. The extra gear allows for single tooth increments all the way up to the 7th sprocket. The shift curve on these new cassettes is so much smoother than competitor 11 speed brands. The cassette is an identical width to the 11-speed versions so they are compatible with all existing Campagnolo freehub bodies. The cassette's last two triplets are CNC'd out of one piece of steel for optimum stiffness Alloy spacers have been used for improved durability.

Chainset

The chainsets in both groups are a smoother, more aerodynamic design than the previous version with incredible aestheticics. The carbon spider on the Super Record version stretches all the way out to the chain ring close to the teeth, creating a cleaner more aesthetically pleasing and more aerodynamic design. The hollow carbon construction offers a low weight without sacrificing stiffness or reliability. The bolt design has also changed from four to eight, which enhances the chainsets stiffness further. Both models will be available in 165mm to 175mm lengths and compact, semi compact and race chainring options.

Chain

The chain is one of the most complicated components when redesigning a groupset simply due to the narrow width and strength required. Campagnolo’s new chain is thinner, lighter, engages quicker and offers the exact same durability as an 11-speed chain.

Brakes

The Super Record brakes have been completely upgraded. Campagnolo have created a powerful new option which is designed to work with up to 28mm tyres and are far more aerodynamic. The lever movement and bearings are completely new, this aid in modulation and increases smoothness. Braking power has notably increased.


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