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15 Dec

650C wheels

Posted by Bold Apps

The range of rims on offer in 650c is quite poor. Hense I bring in these from the USA. The velocity A23 which is 23mm wide.

This set is built with bitex RAF/RAR12 hubs and Sapim CX-rays to create a 1360g wheelset in 20F/24R spoke count. That's enough for the riders if 650c wheels. 

Cost £408

20 Nov

BORG45 Disc wheelset with specialised SCS hubs

Posted by Bold Apps

A customer called with a problem. Specialised in there infinite wisdom created the SCS standard for reason no one else could understand they also forgot to tell anyone so only there roval wheels fitted. Specialised then prompltp dropped this rear wheel stamdard and have now stopped making the rival wheels for it. 

So take one pair of SCS hubs in 24h drilling  and lace them to the BORG45disc to create the BORG45 DISC SCS.

This set with tape and valves is 1745g. So that's approx 100g more than the standard wheelset with the BORG DX hubs but the customer now has wheel that are useable. 

If what you need is not listed give me a bell. There is normally a solution.

 

 

 

 

 

 

05 Nov

New gravel wheelset BORG30 -1452g

Posted by Bold Apps

The photos are quick ones better shots to come.

Gravel and XC MTB riding are similar enough that rims should be no different.

The BORG30 is light, stiff and fun to ride. 

Wheelset weight with Sapim Force spokes and BORG DX hubs is 1450g. 

The rims are tubeless compatible and hookless. Tubed tyres can be used but why would you want to. The internal width of the rim is 25mm. External width is 30mm.

Gravel wheels are not aero wheels.  40mm tyres put a kybosh on that so it should have round spokes. Also ditch the need for aero rims a wide shallow rim can be used. With the right profile this can still be radially and laterally stiff. 

The hubs are 12mm thru axle compatible and reliable. They are made for centrelock rotors but 6 bolt adapters are available.

One important aspect of tubeless compatibility mean to me a tyre that will remain seated with no air pressure. The BORG30 passes that test. This means once a cut is sealed with tyre plugs or sealant you can reinflate with a hand pump. The wheel can be used with inner tubes but I can't think why you would do that to yourself.

Enter the BORG30.

  • Front wheel weight 650g (bare)
  • Rear wheel weight 802g (bare)
  • Total bare weight 1452g
  • 700c and 650B wheel size.
  • 370g carbon rim
  • 25mm internal width
  • 30mm external width
  • 20mm deep
  • Asymmetric rim (2.5mm offset)
  • Triple butted Sapim Force black spokes
  • 24F/24R spoke count
  • BORG DX or Carbon Ti hubs
  • 100x12mm, 100x15mm, and 142x12mm or QR compabile.
  • 40mm  to 70mm tyre with.
  • Cost £830
30 Oct

How quickly do IRC tyres wear?

Posted by Bold Apps

Well not very quickly is the answer but there are a number of factors that affect tyre life span.

IRC Formula Pro tubeless tyres  like the Formula Pro X guard and the Formula Pro RBCC tubeless tyres have a harder compound in the the centre section. The shoulders have a softer compound as this area suffers less wear. The shoulders use a file tread pattern to improve wet grip (I am not sure on the exact reasons why but IRC do insist that the thread pattern works).

The pictures of the front and rear Formula Pro RBCC are from a tyre after 1900km. The rider weighs 112kg and wrote the reviews. 

Front tyre showing little wear.

IRC RBCC front

The rear tyre showing more wear but the thread depth marker is still visible. This tyre is not worn yet. 

IRC RBCC

Riders that ride in straight lines in the Fens get alot of miles out of most tyres. 

Riders that put out alot of power tend to wear rear tyres fasters.

Heavy riders wear tyre more quickly,

Wider tyres tend to last a bit longer as the contact pattch is bigger.

Riders that climb alot tend to show faster rates of wear.

How the tyre wears is a good indicator of the suitability of the pressures used. The photograph of the rear tyre show a tyre wearing evenly. The pressure used is correct (this load dependent). If the pressure is too high if the centre wears only. If the pressure is too low you will see premature squaring off and wear in to far into the chevrons. 

Tyres also get damaged by UV light and will crack. Natural rubber tends to crack more than artifical rubbers so don't store your bike in sunlight. Ozone also affects tyres and again they craze. So avoid Ozone exposure.

So how long to they last. Well for me quite a long time. On my commuter bike, a Genesis Equilibrium disc Ti with two rear Ortleb panniers (bikes weighs 15kg) and all 86 kg of me a IRC Formula Pro RBCC or X-Guard tyres  on the rear wheel lasts 6000-7000km. 

If you get less than me mileage wise then the above will explain why. 

17 Oct

Aero test BORG50C are in.

Posted by Bold Apps

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 dio it here for sensible money. 

 


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