Tempetation Exploration

[matt]

I'm trying to get some fixed wheel miles into my legs before the big event in November, and also want to check out the route, so I was planning on riding the fixie out to Camden and back along the Tempetation route this Saturday the 13th or next Saturday the 20th of October. Anyone interested in coming along?
Round trip should be 100 to 120kms depending on where we turn and I was hoping to start out at about 6am.

[Simon Llewellyn]

Training for a novelty event? Gees I didn't even contemplate that there was a need. I though it was just about suffering on the day. Made even more difficult by the amount of beer consumed the night before.

I don't suspect it is actually going to be that difficult, with multiple food breaks. With a hamburger, chips and 600mls coke per 60kms, that's 10mls of coke per km of the ride! It should be fairly comfortable...Easier than waterfall even....a bit longer...

[mikesbytes]

Matt mentioned the concept of me not riding a fixie at all, so my first ever fixie ride was the 160k itself.

[matt]

You guys can suffer as much as you like, at least I'll know where I'm going.

[mikesbytes]

I'm off to Al's now to buy my rear sprocket, think I need 17t for 74inch ?

Gear chart using Gear Inches
For 700 X 23 / 23-622 tire with 165 mm cranks
With Custom Sizes Cassette
48
14 90.1
15 84.1
16 78.8
17 74.2
18 70.1
19 66.4
20 63.1
21 60.1
22 57.3
23 54.8

[matt]

Got a flip flop hub?

[weiyun]

...so my first ever fixie ride was the 160k itself.

It hasn't happened yet...

[mikesbytes]

Got a flip flop hub?

Nope.

Just got back from Al's with the 17t. He didn't have any half links.

[Simon Llewellyn]

Hey Mike your gearing is 2 inches off. here's the chart..

http://dhbc.org.au/index.php?pr=track5

[mikesbytes]

It hasn't happened yet...

Yes, I was quoting the past tense phrase, as would be heard over and over again in the future.

"You boys are soft nowadays, way back in 2007 my first ever fixie ride was 160k, now where did I put my walking frame"

[mikesbytes]

Hey Mike your gearing is 2 inches off. here's the chart..

http://dhbc.org.au/index.php?pr=track5

Interesting, is Sheldon Brown incorrect, or did I push the wrong button?

[weiyun]

"You boys are soft nowadays, way back in 2007 my first ever fixie ride was 160k, now where did I put my walking frame"

How many inches is that walking frame?

[T-Bone]

I'm guessing he got that from Sheldon Browns site, Always seems 2inches out compared to other charts.

[Simon Llewellyn]

Yeh for some reason sheldon is off. I don't know why but if you ask anyone at the track what 48/14 is they will tell you 92 inch. & same with the charts Terry gives out at Rocky point rd & Al as well. I'm no mathematician so I can't tell you why sheldon is different but he is, Lindsay has had this problem before. But it doesn't really matter because if sheldon is right, no one in sydney will agree anyhow...

[matt]

Its because sheldon brown's calculator defaults to a 27 inch wheel

[weiyun]

Its because sheldon brown's calculator defaults to a 27 inch wheel

If you select 700x23, it'll still give you 90 inches for 48/14.

[mikesbytes]

But I've specified the wheel size 700*23.

Anyway, the real question is whether 48*17 is too big or not?

[matt]

Might be biggish with 165 cranks, depends on how big a gear you usually climb with.

[mikesbytes]

I can climb in the big ring if I want to. There are other factors to consider

[T-Bone]

48-17 should be alright, it's not likely anyone will be riding up razorback. When i make my 3 speed fixie wheel it might be possible.

[weiyun]

Yeh for some reason sheldon is off. I don't know why but if you ask anyone at the track what 48/14 is they will tell you 92 inch. & same with the charts Terry gives out at Rocky point rd & Al as well. I'm no mathematician so I can't tell you why sheldon is different but he is, Lindsay has had this problem before. But it doesn't really matter because if sheldon is right, no one in sydney will agree anyhow...

Ok, I've found the reason and it would appear that the trackies quoting 92 inches are still living in the past.

According to Wikipedia's entry on Gear Inches, old school guys quote gear inches strictly based on 27" wheels, ignoring the fact that 700c wheels are the norm these days. So that's where the extra 2 inches are from. If one is precise, feeding accurate physical data into the calculation, then 48/14 would give you 90 inches, as in Sheldon Brown's calculator. So staying with the 27" wheel convention may be adequate for mental comparative purposes, but the number won't be suitable for further calculations nor comparing with gearing calculations on different styles of bike.

I guess there is conservatism in the sport... So Sheldon was right and I agree with him.

BTW, I contacted Sheldon B and he alluded to similar. I've also suggested that he make a comment on his page to bring those traditionalists back into the 21st century.

[weiyun]

Hey Mike your gearing is 2 inches off. here's the chart..
http://dhbc.org.au/index.php?pr=track5

Guess this chart should be updated for current 700c wheels, or at least an explanation made that this table is based on old styled 27" wheelset standard.

[matt]

Nice one weiyun, that makes a lot of sense.

[weiyun]

Nice one weiyun, that makes a lot of sense.

But you were right too, just the reverse.

[Huw]

Interesting! Thanks for pursuing this Weiyun!

[Simon Llewellyn]

see this issue is problematic because even though our gearing is wrong,it is what everybody in Sydney uses. So if you rock up to the track stating 700cc gears no one will understand what your on about. So it may be wrong but it's universal & it's trackie language...

[weiyun]

see this issue is problematic because even though our gearing is wrong,it is what everybody in Sydney uses. So if you rock up to the track stating 700cc gears no one will understand what your on about. So it may be wrong but it's universal & it's trackie language...

Gear inches is defined mathematically that relates to the ratio of chainring, cogs and wheel size. It makes no sense to stick to a number that is out of touch with reality.

Gear (in) = Wheel (Dia in) × Chainwheel ÷ Sprocket

For a 700c wheel with 23mm tyres, the diameter is 26.3".

Maybe the old bikers should update their reference or change their terminology and I would bet that those professional sports scientists aren't using 27" wheels for their detailed calculations. In any case, it's about time young cyclists are properly educated on the math and science of their sport and made sure the language they use makes sense.

Another useful formula for gear, speed and cadence. Without the proper gear calculation, the calculated speed would not be accurate.

Speed (mph) = Gear (in) × Cadence (rpm) ÷ 336

Or maybe people should learn the European "Meters of Development" reference, a measures the distance travelled with each turn of the crank.

MOD (m) = Wheel Circumference (m) × Chainwheel ÷ Sprocket

[T-Bone]

Good work. This means i can stick to using sheldon browns calculator.

[Simon Llewellyn]

I don't disagree with you Weiyun, if the gearing charts are all wrong we should be using the right gearing charts. The only outside reference I can think of is in one of the old ride magazines referred to Anna meares Gears. That would judge if the whole track world is living in the past. I just can't find the magazine...

[weiyun]

Yes, I can see what you are saying too. Given the differential b/n 27" and 700c is just under 3%, it's just convenient to not bother with relearning the gear inch chart. Further, given the numbers are typically not compared with other styles of bikes or used with riders' power data, there's no real incompatibility to initiate a change. As you suggested, it's an entrenched culture. The part that really surprised me was the fact that with all the track experiences we have here, the cause of the discrepancy was not fully recognized.

[Simon Llewellyn]

I've found that in the states they just don't really use the inch role out. This cuts out the confusion, they tend to use the chain ring and cog instead. I found two forum posts, one using the 27 inch formula and one using 700c. I was expecting to see the 700c formula on both but it seems some have moved forward and some remain behind the times...

"The Difference between a 48 X 14 and a 51 x 15 is less than 1% ( 92.5 vs 91.8 ).
I ride a 51 x 15 at MTV, as it appears 'MarianTrackie' does too (Is this Tom From Marian?).

Gearing is more an issue of your abilities and preferences.

In the Worlds final, Bayley and BOS were using 96.4 and 98.3 inches.
Figure a 10.5 sec 200m in a 96 inch gear is an average RPM around 155 rpm. "

http://www.fixedgearfever.com/modules.p ... ght=inches


"Typically at the track, you will see the cogs chainged more often then the chainring.
I have a 49-15 on my bike right now. If I threw a 13 on that I would go from 85.8 gear inches all the way up to 99 gear inches."

http://www.fixedgearfever.com/modules.p ... ght=inches

So maybe the best way to go is with the majority and talk chainring/cog rather than in inches....

[weiyun]

So maybe the best way to go is with the majority and talk chainring/cog rather than in inches....

The problem with just the cogs is that it goes back to the days before gear inch calculation, in that you can't easily compare the various combinations. Along the same line, it doesn't give a clear picture of the gearing for people who move b/n road, MTB, track and other disciplines.

As noted earlier, the Europeans supposedly use MOD for this purpose. Did you see any evidence of that in your search? It's metric. I guess they may all be in non-English forums.

The other interesting point of reference would be the AIS. It would be interesting to find out what they use.

[Huw]

Fixies at the Paris-Brest-Paris earlier this year here!

[matt]

Another issue apart from wheel size when comparing gearing on different bikes is crank length. I tend to think that Sheldon Brown might have it right with his "Gain Ratio" method. I recently changed from 170 to 175 cranks on the fixie and it made a noticable difference. I have also read articles that consider other factors including bar width when discussing gear selection, the idea being that wider bars will help you climb by giving you more leverage so you can use a bigger gear.

[weiyun]

Another issue apart from wheel size when comparing gearing on different bikes is crank length. I tend to think that Sheldon Brown might have it right with his "Gain Ratio" method. I recently changed from 170 to 175 cranks on the fixie and it made a noticable difference.

Very interesting. My Ridley runs on 170 vs 175 on the Bianchi. I have to say that I was rather ignorant of the change. Yet again, they are CT and triple respectively.

Given what we have here already, I think the track fraternity would really get turned upside down if people try to push Sheldon's Gain Ratio into their midst! I am staying out of this one...

[mikesbytes]

Don't you guys sleep;
Simon 2:56am
Weiyun 5:39am

Perhaps we are just been a little picky, apart from rollout for Junior rules, its more about understanding the relationship between the rings and the cog.

We could just change the heading of the gear ratio chart to include the word "traditional"

[matt]

I have hardly ridden at all on the track, and the trackies will probably bite my head off but maybe there are different issues between fixed on the track and fixed on the road. On the track you dont have to consider climbing or descending and variation in crank length is limited to avoid bottoming out. So a simple standardised method of comparing gearing works.

Maybe a couple of inches change on the track doesn't make so much difference because its flat? After riding 73" for a while i tried 75" and was amazed at what a difference it made, and that's less than a 3% change.

[mikesbytes]

Fixies at the Paris-Brest-Paris earlier this year here!

The bloke who's going to ride 300k on our fixie ride rode in this, but the horrid weather prevented him from finishing, as it did for many other riders.

[Simon Llewellyn]

Another issue apart from wheel size when comparing gearing on different bikes is crank length. I tend to think that Sheldon Brown might have it right with his "Gain Ratio" method. I recently changed from 170 to 175 cranks on the fixie and it made a noticable difference. I have also read articles that consider other factors including bar width when discussing gear selection, the idea being that wider bars will help you climb by giving you more leverage so you can use a bigger gear.

Crank lenght is not really such a great issue on the track because if you want to use the banking your limited in the crank length you can use. 170mm is the longest standard length. Anything longer has the potential of clipping the banking. They use 175mm for pursuiting standard but pursuiters rarely go up the banking...

I don't think that crank length changes the gearing or cadence or anything it just uncramps your legs a bit for the tall guy. The longer the cranks the closer it is to walking.... I actually prefer 170mm cranks over 175mm cranks because i'm used to them. I can spin a much higher cadence...But I hear 175mm are much better for climbing with the leverage...

[weiyun]

Don't you guys sleep;
Simon 2:56am
Weiyun 5:39am

Working...

[weiyun]

I don't think that crank length changes the gearing or cadence or anything it just uncramps your legs a bit for the tall guy. The longer the cranks the closer it is to walking.... I actually prefer 170mm cranks over 175mm cranks because i'm used to them. I can spin a much higher cadence...But I hear 175mm are much better for climbing with the leverage...

Have to disagree on this one. The whole purpose of this gearing equation is to simplify the expression of the overall mechanical advantage of the system. This mechanical advantage ratio can be used direct to an applied force at the pedal axle and extrapolate the resultant energy transfer through the full system. When looked at from a fit point of view, that's starting to take into account of body variables.

Talking about 170 vs 175 cranks. The leverage difference is also just under 3%, right on the difference a 27" and a 700c gearing chart gives. So if Matt is feeling the difference at that percentage and others are suggesting "much better", then there's something to really think about.

[weiyun]

Here's a follow up to this gearing discussion. I contacted AIS and asked them what they use and in response, they sent me the Excel spreadsheet they use, which is a rollout/development calculator in metric units. I note also that it has two tables, one for 630mm diameter wheel and the other 672mm. It would appear that the 672mm diameter number corresponded to the external tyre diameter of a mounted 700c wheel. Not sure what the 630mm diameter wheel referred to. 26" wheel?

Anyway, it would appear that the AIS is full metric and uses development rather than gear inches.

[Kieran]

Developement is a good measure to use as you can turn cadence straight into speed very accurately. This is how your speedo works. If you find the manual it usually has a circumfertence chart, note that even thicher tyres can make a significant difference.

You can then get speed by
Speed(kmph)= 3.6*Cadence*wheel development(meters)*chainring size/cog size

Mechanical advantage would be a good system as it is probably the best indicator of the difficulty of pushing the gear.

The problem with using the mechanical advantage as a measure is it doesn't help compare exact setups, in other words you have too many variables to be able to interpret the number back into a chainring-cog combination. I'm sure people who ride the track after a while know exactly what a number means as there is only one combo possible to get that number. Give them a leverage factor and there may be several ways to get a very similar number. You know, if you gave your mechanic a demand for a 20.75 ratio, do you really want a 51 15 with 175mm's or a 49 with 170,s, or some other oddball way to get to that sort of number.