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

07 Sep

Pillar spokes

Posted by Malcolm Borg

Due to lengthening delivery times from Sapim, The Cycle Clinic will  be distributing Pillar Spokes.

Pillar manufacturer excelent spokes from the same wire stock that Sapim use - Scandvik T302 18/8 stainless steel. 

We will be importing triple butted spokes. These offer a better fit in almost all hub which commonly use a 2.5mm dimater spoke hole. Also a thicker elbow -2.2mm - means longer fatigue life for the spoke.

PSR TB2016, PSR TB2017 and PSR TB2018 spokes are on order in silver and black. J bend only.

These spoke have a 1.6mm, 1.7mm or 1.8mm centre section. 2.2mm spoke elbow and 2.0mm after the elbow.

The other spoke we are bring in is the Wing 20 and Wing 21 in J bend and straight pull and  silver and black.

All spokes will be bought as blanks and cut and thread to order in the shop. Pillar use a 30mm barrel so each blank has a 10mm spoke range it can be cut too. 

 

07 Sep

New BORG Wheels hubs

Posted by Malcolm Borg

Hub supply is an issue so it make sense to get my own made for all our wheels.

So the first that will arrive are the new disc brake hubs.

These share the same bearings and freehub as the 2:1 hubset.

Flange size is large at 59mm which reduces the spoke tension changes when compared to a small flange design. The hubs flange spacing is kept as wide as possible to maximise spoke bracing angles.

The bearing used are from NTN. NTN are one of the world's top tier bearing companies and these bearing are used solely in our hubs. The Cycle Clinic is also an NTN bearing distributor. The bearing used in the hub shell are 6902 to ensure decent life.

The freehub uses 4 independently sprung pawls running in a 36T ratchet ring.

This same bearing arrangement for the rear hub and the freehub is used in the new rim brake hub. The front hub you already know. It the same as used in the 2:1 hubset.

Rear flange spacing is 16/39mm to ensure stiff rear wheels. Finish will be black and silver. The same bearings offered in the 2:1 hubset and the freehub is the same as the 2:1 and disc brake hub.

28 Feb

Rim width and tyre width.

Posted by Malcolm Borg

Rims are getting wider. Thats a good thing to a point. There are some aero wheels on the market now that have got too wide in our view. 21mm or wider internal widths are marketed for 25mm or wider tyres. Cannondale fit a 23mm vittoria tyre to 32mm wide Knot64 wheels. Brontrager suggest road tyres can be used on  there 25mm internal width rims and trek fit a 32mm tyre to these wheels for there bikes.

So let pick this apart by starting with the basics. A wheel is nothing without a tyre and a tyre is useless without a wheel. A wheel should be designed to get the most out the tyres they are intended for. That means standards and sticking to them. ETRTO set these standards and they are not just about safety.

Whats the perfect tyre shape? Well circular just like a tubular. Thats why tubs handle so well. Tyre type

Clinchers or tubeless clinchers will deviate from that perfect shape. How much will determine how much the handling is affected. If the rim is to narrow and tyre too wide the tyre can light bulb and give vauge handling in the bends.

If the rim is too wide for the tyre the tyre ends up shorter and wider but the crown is flatter and the sidewalls straighter. In the case of knot64 wheels, the tyres Cannondale supply are stretched so much the sidewall curves inward from the bead. 

A tyre thats stretched will not handle as well as if it wear mounted to a rim of the ideal width. That is the

Now such combinations of a over wide rim and narrower than ideal tyre is often paired to lower aerodynamic drag. This however one aspect of the wheel, tyre system.

The move to wider tyres does make some sense. On perfect road surfaces they should show higher rolling resistance but roads are not perfect are they.

Wider rims mean less sidewall flex which in turn lowers rolling resistance and less sidewall flex can improve tyre handling. There are limits though. Sidewall flex also impacts tyre feel. Reducing flex too much can make tyre tyre feel snappy. Tyre flex is your road feel. Stiffer sidewalls still flex but the snap back harder. The result is sudden loss of grip at the limit with little warning. Just like on some cars which give no feedback to the driver. Too much sidewall flex is a problem also. If the the tyre becomes too stretched rolling resistance can increase. Remember the shape of tubular tyre.

When the crown of the tyre is flattened off by mounting on a rim that too wide, the tyre wears in unfamilar ways. When cornering the tyre still ends up wearing the centre more than it would if the tyre is mounted to a narrower rim. In testing various rims i have had 25mm IRC Formula pro tyres and Continental GP5000 tyres mounted to 20mm internal with Velocity aileron rims and wider rims. The wider the rim the more noticable the excess wear in the centre section of the tyre is. 28mm tyres did not show this problem on 20mm internal width rims. Therefore to keep my road wheels compatible with 25mm tyres the internal width are no wider than 19mm. Essentially a narrow tyre on a too wide rim will square off sooner and have a shorter life.

Rims that are too wide also expose the side walls of the tyre and the rim itself to damage more frequently. There is nowt slower than the tyre with a damaged sidewall or a wrecked rim. Pinch flats on stretched tyres are more likely.

In order for a tyre to be made for a rim that really wide it shape has to be altered. Because a bicycle tyre has no shape without air pressure (this keeps tyre weight down) we will not see tyres shaped like you do on cars or motorcycles any time soon. You can alter tyre thread thickness at various points on a tyre though to optimise the crown shape for ultra wide rims. However such tyres then are not optimised for narrower rims and so far there are no road tyres made that way. 

Tyre manufacturers mostly make tyres (unless they state) that meet ETRTO specifications. While the tyre size chart can be a stretched a bit without consequence for example a 25mm tyre on a 19mm internal width rim many of the the current wheels offered by many manufacturers are more than pushing the envelope. Even for those that make tyres and wheels thoe tyres  will  be made to ETRTO specifications. 

This is why our road wheels are 19mm internal width not 21mm or wider because wider maybe more aero but thats too focused. 19mm is wide enough for 25mm tyre to 40mm while preserving the tyre shape the tyre manufacturer intends. A good wheel has to balance characteristics.

Our gravel wheels there for start at 23mm internal width to stop road tyres being used on them (I hope). Gravel wheels use rim widt that are used for MTB's.

I hope you can see tyre shape is key to how a tyre preforms and wears. Since the tyre is what keeps you upright get the most out them. Pick the right rim.

 

 

 

 

28 Feb

Set up of BORG DX hubs

Posted by Malcolm Borg

BORG DX rear hubs use bearing preload adjustment. This has to be set with the wheels fitted and secured to the bike.

The rotor and any adapter must be removed. Use a 1.5mm allen key to undo the grub screw on the left side of the hub and undo the adjuster.

Fit the wheels and secure them normally to the frame or fork. Advance the adjuster till there is just no side to side play. Secure the grub screw.

Remove the wheel and refit the rotor and the wheels can be refitted. 

To inspect the bearings or remove the freehub use a 12mm hex key on the left side and a 17mm spanner and undo the left end cap. At this point you can replace the axle, freehub or carry out any other maintenence job.

 The front hub has no preload adjustment. The end caps are push fit. There are two bearings in a shell. Therefore to inspect the bearings just remove the end caps.

 

20 Oct

BORG rim brake hub maintanence

Posted by Malcolm Borg

These BORG rim brake hubs are simple to service. Take apart for the following reasons

1) to replace bearing

2) to replace freehub body 

3) to add grease to freehub mechanism.

Bearing require changing when they are not longer smooth. When the bearings spin with noise they are worn. They will spin freely at this point but there will extra drag with rider load on the wheel. Bearing life should be long. 

Insert 2x 5mm allen keys into end caps. Normal right hand thread and undo. One end cap will undo.

Insert a 10mm allen key into the axle and with the other 5mm allen key remove the other end cap.

 

 

The freehub bearings should be removed with a blind or collet style puller and refitted. 

Freehub pawls and springs are a spare part and can be replaced.

To remove axle knock it out with a rubber mallet from the drive side. The nds bearing will push out of the shell.

 

 Use a bearing puller to remove drive side shell bearing and a bearing press to fit new NTN 6902 bearings. 

The freehub bearings are NTN 6802. 

Pictured here are shell bearing with contacting seals and a freehub with non contacting seals.

The hubs are made with the tight tollerances that NTN bearings provide. Therefore use of other brands of bearings while possible may affect bearing life and hub performance. 

 

 


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