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TOPIC: Saturday cycle? Those oh-so embarrasing questions!

Re: Saturday cycle? Those oh-so embarrasing questions! 18 Mar 2015 13:25 #6457

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This is an excellent thread! Well done guys. On buying a bike and aerodynamics, I found dropping 20kg far more beneficial then any bike upgrade or aero this and aero that. Particularly on the hills. There's a lot you can do with your body that will save your euros for a while. That said, I still upgraded, most recently to my very much loved Canyon road bike. Again, super thread.
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Re: Saturday cycle? Those oh-so embarrasing questions! 19 Mar 2015 10:44 #6463

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Thanks Anthony. The thread is really intended to get some discussion moving particularly within the new to tri group. Sometimes a question can seem so obvious that it is embarrassing to ask!

Occasionally the theory works and last evening our cycling leader Colm passed back some questions about gearing, how to best use your gears and how or when to shift with which derailleur?

"Derailleur!?!?" I hear you say... "What in God's name is a derailleur?" OK then, back to basics. Our bikes use a process of chain-shifting to match the cog on the rear wheel to the chain ring on the pedal crank to give us the ideal mechanical advantage to turn the pedals. By ideal, I mean a gear ratio that allows you to match your leg revolution rate or "cadence" to the terrain you are cycling over and speed you are moving at. People are different but this will most often mean turning the pedals over at a cadence of 50 - 120rpm but probably about 80 +/- 10 rpm most of the time.

This all means we need a mechanism to lift the chain from one ring to the other on the front chain rings. This is often called the "Front mech" which is short for front derailleur mechanism. We will have a row of cogs on the axle of the rear wheel also giving us a range of speeds available from each of the front chain rings. This row of cogs is often referred to as a "rear cassette" as this would traditionally be fitted as a unit to a pro-race bike to suit the terrain. We need a mechanism to lift the chain from cog to cog on the rear axle also and this is known as the rear derailleur mechanism which is abbreviated to "rear mech".

How to use the gears? As a rule you will use either of the front chain rings to select a "mode" of riding and you can simplify this to slow and fast. The smaller chain ring on the front will allow you a range of speeds between cruising and climbing where the larger ring on the front would suit only faster cruising speeds or descending hills. Already you should be able to see how this is not something you will typically change every few metres along the road, more likely in fact that you will crest a hill and then move to the large ring to come down the other side. What is important to notice is that there is a big jump in the gearing from the small to large ring on the pedal crank whatever gear your chain is over on the back axle.



The rear mech will typically get all the exercise as this is the way you tune your leg-speed or cadence to the terrain. Let's assume your chain is on the correct chain ring at the front, then you will be changing the rear cog as often as you need to to maintain a steady speed and cadence. How often you will change depends a lot on your physical strength. Speaking for myself, I volunteer that I am not particularly strong so never seem to leave the chain on any cog for very long. I am continuously moving the chain up or down the rear cassette to keep my cadence up at 80-90rpm on the pedals.



Hint: Consider your chain line! Yes, something else to think of while you are already thinking hard about which gear to be in. In an ideal world your chain will only use the left half of your rear cassette while in the smaller (on the left side) chain ring of your pedal crank. This avoids the loaded part of the chain (the tangent on the top from the casette to the chain ring) from following a "S" path as it weaves left to right. Similarly when your chain is on the big ring (the right hand ring on the front) you will typically use the smaller cogs on the rear casette, again keeping as straight a line as possible along the top of the chain. Most bikes will in fact have an overlap where the lighter one or two gears on the big ring are similar to heavier one or two on the small chain ring. This is in most cases to allow the chain to be kept as straight as possible. So what is wrong with a bad chain line? It is very hard on the links of the chain putting all the tension along one side of the chain or the other. You can expect accelerated wear or premature failure if you persistently do this to your chain. Similarly the chain is moving on and off the chain rings and rear cogs at an angle so will wear the sides of the sprocket teeth on these cogs. Your chain will normally let you know if you are being nasty to it by making quite a racket when the chain line is bad. The image below may explain what I mean:



Now to be very fair, you are new to group cycling and already you are being bombarded with "look here", "cycle there", "shout this" and "carry that". There is a lot to think about compared to tootling around on your own. Practice shifting the gears as often as you can to get a feel for the pedalling effort. Get an idea of what sort of power you can put out at what sort of pedal cadence as this will find your "sweet spot" where you should aim to be on gear selection. If you practice this enough not only will it become totally reflex with your hand automatically changing up or down one or two gears at a time but you will find yourself selecting a climbing gear before you feel the strain or a longer ratio as you feel the bunch speed up along the road.

The gears are there to match your strength at your ideal pedalling cadence to the terrain you are riding as I said at the beginning. Don't be afraid to use them. If they are not shifting correctly then get them looked at or ask somebody for their opinion. I am a bit nuts (yes, happy to concede this) about a clean chain and gears and nice gear shifting, it simply drives me mad when I am flicking up and down trying to quietly shift to a new gear. Maybe it is because I never stop changing gears but it is without doubt the better of two evils!

Relying again on the lads in GCN, here is an other great vid to have a look at, "how to improve gear selection".



Enjoy and talk soon

Garry

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Re: Saturday cycle? Those oh-so embarrasing questions! 20 Mar 2015 18:33 #6474

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The chaps at GCN published a new video today. Unfortunately waaaay above my pay grade! Anyone?



Thinks I will just go with the Neanderthal look...

Garry

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Re: Saturday cycle? Those oh-so embarrasing questions! 23 Mar 2015 17:25 #6478

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At the risk of complicating things with regard to gears and how to use them, here is an other pair of videos from GCN which will explain how to best change gear and then a technical look at what components are likely to be on your bike and why.

How to change gears:


Understanding the gear ratios on your bike:



Keep an eye on this thread for more later this week. As a pointer we have yet to look at some very important issues such as:
  • How to repair a puncture
  • What to carry with you on a spin
  • What to eat (or not) on a cycle
  • How to prepare your bike for a race

If you have any particular questions regarding any of these or indeed any other aspect of cycling please do post a comment or question here. As with all of my posts, I will again urge you to show up on Saturday mornings, get stuck into the group cycles, and start chatting to others. This has to be by far the best way to learn!

Enjoy the vids and talk soon

Garry

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Re: Saturday cycle? Those oh-so embarrasing questions! 06 Apr 2015 20:31 #6552

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And more on gears! I did state unashamedly that I am a bit anal about keeping the chain and drive train clean for nicer gear shifting. Kept clean and adjusted correctly with all the moving parts of your cables and derailleur mechanisms lightly oiled there is simply nothing better than just flicking your shifter and not giving a thought to it any further. When in good order the gear change will be something between silent and a click, even under light power.

So how does one keep everything clean?

Option 1:
WD40 and a cloth! Many would shoot me on the spot for mentioning the stuff but I have used it for years as a very powerful cleaner (I don't use it as oil). It really is superb at cleaning grime. I spray WD40 onto a cloth and wipe the chain and the chain rings (the big sprockets up front). I then use the oily cloth afterwards to, well, sort of floss in between the sprockets of the rear casette. If need be, I will spray a little WD40 on the casette and keep flossing until it is clean.


Option 2:
Engine cleaner and soapy water B)
This photo shows the whole kit from 5litres of engine cleaner (a group buy from a trade motor factors is probably best), a Lidl chain cleaner hooked up on the chain and a cut down paint brush with a jam jar.


A couple of minutes turning the pedal cranks backwards with engine cleaner in the chain cleaning widget does most of the work. I do it in two stages taking a break to attack the sprockets with the paint brush and a little engine cleaner. This stuff comes off very easily with water, even easier with hot soapy water (fairy liquid is good). The photographs below show a car wheel cleaning brush I use to get into corners.
[attachment:2]Brush_Cassette.png[/attachment]



Time to give the whole bike a going over with soapy water. I hate the sound of grit grinding away at the wheel brake surfaces so give the brake pads a good few stabs of the wheel cleaning brush while I have it in my hand as plenty of crud collects in the grooves of the brake pads.


Not much more to it but to hose off and then dry excess water from the drivetrain. If I can I leave the bike in the house overnight after a clean like this to dry off then re-oil the chain and any moving parts on the derailleurs before the next cycle.




It is probably in my head but I feel the bike is easier to ride when it has just had a deep clean like this (which is about once every 2-4 weeks in the winter, 4 weeks or so in the summer). It certainly shifts gears easier and with less grinding, crunching and click, click, clicking!

Coming soon: Two more installments, firstly how to repair a puncture and then one on what to eat on a Saturday spin.

I hope you're all enjoying the Easter sunshine out on your bikes?

Talk soon

Garry
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Saturday cycle? Those oh-so embarrasing questions! 15 Apr 2015 10:59 #6573

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Feeling deflated?

Puncturing out on your bike, it is going to happen to all of us at some time as sure as night follows day so it really is something that we should all know how to deal with. It is embarrassing when you are in a group and suddenly that loud hiss and like a parachute the bike slows underneath you. Step one is “Don't panic!”. It is a good idea to run through the next few items in your head now in the calm of home as you will have to react quickly the instant your tyre goes down.

Shout out loud “Puncture!” to be sure nobody in the group runs into you.
Move out of the way of others or gesture them past you so you can stop.
Unclip your foot and stop wherever it is safe as soon as you can
Ask somebody to stop and help you, even if you are a tyre changing expert.

The process of repairing the flat tyre is very straight forward if you understand a couple of points so once again, keep calm! Repairing the puncture with a patch on the roadside is not a good idea as it takes time, doesn't always work and is fiddly. Remember that in all probability you will be cold or wet or drowned in sweat or all of the above (unless you are on holidays abroad!) so a quick remedy is the order of the day. Be sure to carry at least one and ideally two inner tubes with you. It will take five minutes at least to repair your tyre so to avoid getting very cold arrange for the rest of the group to cycle on along the planned route for five minutes, u-turn and come back to see have you fixed the tyre. All going well you will pick them up coming the opposite direction in only a few minutes having repaired successfully.

So you have a helper, the group has cycled on gently to stay warm and you are about to repair your puncture. The list below is a step by step how to:

Remove the wheel with the punctured tyre
You should have a quick-release hub/skewer on your bike for quick puncture repair so know how to remove the wheels. Practice this with a helper before or after a Saturday spin if you don't know how. Your rear wheel has the chain over the casette sprocket and through the rear derailleur mechanism. You really should practice how to remove the wheel in a calm moment, you will be glad you did! Your front forks will have “lawyer tabs” which are raised ridges to prevent your front wheel coming off accidentally should the quick-release open. You will have to open the skewer enough to clear the lawyer tabs so know that they are there. This photo shows them quite clearly



Release the tyre bead and remove the inner tube
Almost all of the tyres you will possibly use are of a “Clincher” design where a raised bead around the outer rim of the tyre is engaged in a groove in the profile of your bike wheel rim. Words don't explain this very well so have a look at a cross section of the wheel and tyre borrowed from Wikipedia

1. Wheel Rim
2. Rim Tape
3. Braking Surface
4. Bead Tensile Core
5. Inner Tube
6. Tyre Carcass
7. Tyre Tread


I will refer to this diagram again so be aware of the items numbered in the list!
It is clear in this image that the inner tube presses the tyre bead very snugly into the groove of the wheel rim. Two things to note:
1. If the tyre is soft but not completely flat it will be difficult (or impossible) to release the bead
2. If the tyre has been fitted for a long time this may feel like it is glued on.

In any case with all the air out of the inner tube, pinch the tyre close to the wheel rim all the way around to be sure the bead has released. The bead tensile core is either steel wire or an aramid fiber such as kevlar (what bullet proof vests are made of) so DOES NOT STRETCH! It is therefore essential that you put the tyre bead as deep into the bottom of the wheel section (where the rim tape is) around as much of the wheel circumference to allow you stretch the opposite side of the tyre bead over the wheel rim to access the inner tube.
How to do this:
1. Pick up the wheel at 3 and 9 O Clock
2. Bend over a little and place the wheel against your breast bone at 12 O Clock
3. Move your hands to the 6 O Clock position keeping the wheel against your ribs
4. Pinch the tyre rim and working your hands around the rim, pull the bead of the tyre into the bottom of the trough in the wheel rim. Pinch – Pull – Pinch – Pull etc. It helps to have strong fingers!
5. With the tyre pulled deep into the trough in the wheel rim as far around as you can, see can you put a tyre lever or two under the bead of the tyre and gently lever over the rim of the wheel. The person who stopped with you is worth their weight in gold right now, 3 hands are good!

Few people are sufficiently aware to pull the bead deep into the wheel section but a few minutes watching car tyres being removed or fitted will explain that they are designed to be changed easily but this process is a must!

Remove the punctured inner tube
Calmly work the inner tube out from inside the tyre but try to keep the tube, tyre and wheel in the same relative position to each other for a moment. There may be a threaded ring screwed onto the valve to hold it snugly into the wheel rim. Have a look at the inner tube now to see if you can identify an obvious source of the puncture. If so, then look carefully at the wheel rim for any object that may have punctured your inner tube. If something has penetrated the tyre tread and carcass it WILL BE VERY SHARP so be careful not to cut your fingers! If you can find a piece of glass, wire, metal or stone then bending the tyre carcass tightly can expose enough to pick the object out. If it punctured one inner tube it will puncture the next one so it has to be removed. Be aware that a wheel spoke may have penetrated the rim-tape or a sharp object may have found its way inside the tyre so be vigilant and find anything that may have caused the puncture.

Fit a new inner tube
Take the valve cap and locking ring off a new inner tube and ideally put one or two shots of air into the tube using a pump, just enough to put a slight shape into the inner tube. Pull the tyre bead back enough to put the valve through the hole in the wheel rim. Carefully work the tube into the tyre all the way around. Starting at the valve, push the valve back into the tyre as far as you can, pinch the bead of the tyre and start to work the bead inside the wheel rim. Once again the objective is to work from 6 O Clock all the way around the rim of the wheel pinching and pulling the tyre bead as deep into the wheel section as you can. This is the only way to have enough tyre bead to stretch around the wheel rim when you get to 12 O Clock. Most tyres can be stretched over the wheel rim without tyre levers if the bead is pulled deeply into the wheel section. If you do need a tyre lever to help the bead over the wheel rim be very careful not to lever against the inner tube, pinching it against the wheel rim. You will puncture the new tube if this happens so keep calm and be careful.

Inflate the tyre
This is best done in two stages. It is possible and quite easy to pinch the new tube between the tyre bead and the wheel rim. When this happens all appears to be good until the tyre is almost fully inflated or sometimes a few metres up the road. The pressure on the tube will cause it to fail with a big bang... not good!
Inflate the tyre partly, just enough to take up it's final shape but not so hard that you can't pinch the bead to check for pinch points. Work your way around the rim pinching the tyre near the bead to be sure there is no sign of the inner tube. If you are happy that the tube isn't pinched anywhere then continue to inflate the tyre. This can be hard work with a mini-pump so our helper is key here too! If you use a gas cannister and valve adaptor, spend the money on a spare gas can or get your hands on an empty can and get somebody to show you how to use this. There is absolutely nothing worse than letting the gas out of the can and completely missing the inner tube!

Refit the wheel
This should be as simple as reversing the procedure that took the wheel off. Be careful not to dislodge the brake pads from your brake caliper. Once the wheel is re-fitted be sure to close the quick-release on your brakes, lift the wheel off the ground and spin the wheel to be sure the brakes are not rubbing. Move the caliper left or right a tad if you need to to make sure all is clear.


Things to think about:
Did you hit a pothole or kerb? - This can cause a pinch flat where the wheel's rim punctures the inner tube
What tyre pressure? - Soft tyres permit objects to penetrate the tyre carcass (80 – 120psi is normal)
Do you carry two inner tubes? - Two inner tubes is a must on group rides, don't assume anything, ever!
Have you changed a tyre? - If you haven't, then you should. The kitchen or the garden on a quiet day is the place to try it out. The side of a mountain in the pouring rain is where you will appreciate this!

Though this video relies on the tyre levers above moving the bead deep into the rim to make extra slack it is a good example of how little is involved in fixing a flat. Just keep calm and think as you go.




Talk soon

Garry

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