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PostPosted: Mon Jan 14, 2013 2:40 pm 
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Joined: Sat Jun 06, 2009 7:28 am
Posts: 479
This is a weird question but anyway...

I have some mad plans to take a stab at the 24hr velodrome world record later on this year. Shit's gonna get real.

I will be doing this indoors on an olympic velodrome, because fast.

I will have access to a very, very fast road TT bike (Trek SC 9 with Zipp 808 FC/Sub9 wheels etc) and from what I can gather this is a faster setup than all but a few very spendy track bikes.

My question is if anyone has ridden an 8cm bb drop TT with 172.5mm cranks bike around a 43* banked velodrome?


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PostPosted: Mon Jan 14, 2013 2:57 pm 
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Location: Vienna, AUT
I have seen people riding geared TT bikes on the track in Moscow (Krylatskoye) and it was painful to watch. Yes, I saw a few people pack in pretty hard. It seemed to be a local triathlon club or something. I am not certain that the BB height and crank length was to blame for the crashes I saw. It seemed to be more rider error than equipment. It seems like you could do it, assuming the velodrome allows geared bikes, but your riding style would need to be adapted to the angles/environment.


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Posted: Mon Jan 14, 2013 2:57 pm 


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PostPosted: Mon Jan 14, 2013 3:07 pm 
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Location: Shetland, Scotland
Cervelo P3 and T3 are presumably the same geometry though?
Are you looking at building a track bike using a TT frame, or is gearing allowable for this record?
I remember someone posting that the Trek SSC in particular had a lower BB, and so the general issue might be worse for that specific frame.


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PostPosted: Mon Jan 14, 2013 3:34 pm 
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If you know your velocity and the radius of the velodrome you can calculate your lean angle.
If you know the cornering clearance of the bike and banking angle of the velodrome you'll be able to predict whether you'll be hitting the wood with your pedal.

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PostPosted: Mon Jan 14, 2013 3:50 pm 
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Location: Calgary
P3s and P3SLs were pretty common on the track a few years ago and were used for all types of track events, although usually by endurance riders rather than sprinters. I seem to remember them even at steep tracks like Burnaby (200 metres). I've certainly seen them racing pursuits, scratch races and points races on 250 tracks with no problems. There are a few things to keep in mind:

- you're talking a 24 hour record so you're going to ride on the bottom line where tracks are usually at their shallowest
- you're not going up and down track where he might have a problem with pedals bottoming out
- 172 cranks and even 175s have been used by world class riders. The Austalian Ride magazine had something on track bikes a few years ago. I seem to remember the Aussies might have been riding 175 and I think Marianne Vos used 172s
- I'm pretty sure you won't be allowed to ride with gears. For a 24 hour attempt you don't want them anyway because you're riding on a completely flat track at a constant speed and it's easier to keep up a steady cadence if you're not shifting all the time
- rear dropout spacing will be a challenge. When you switch that Zipp disc to fixed, it will have 120 spacing. You'll need to get a special axle made. When P3s were the thing around here, there were lots of axle kits
- 808 front won't cut it for a 24 hour record. You'll be giving up a lot of time to riders who used front discs. Indoors, world class competitors all use front and rear discs

In the end, it won't be about the bike as much as it will be about your ability to withstand pain for a long time. If you're planning for your record to go into some record books, make sure the bike is UCI legal. Some TT bikes made for triathlon don't meet current UCI standards.


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PostPosted: Mon Jan 14, 2013 3:53 pm 
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Location: Santa Cruz, California, USA
I've ridden a mtb with platform pedals and 175mm cranks around a velodrome.
As long as you're going a reasonable speed on the banking it's not a problem. Just don't try to track stand or go really slow like a match sprinter.


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PostPosted: Mon Jan 14, 2013 5:26 pm 
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I used a P3C last year on a 44 degree track with 170 cranks and had no problems.
Setting up a rear disc is a pain bc of the spacing but can be done. I used my Zipp disc with a track axle conversion kit (can be hard to find) and then added extra nuts on each side to accomadate the wider spacing. The short drop outs are also a pain and generally require multiple chains if you are doing different track events but for 1 event you will know what gearing you will be using so you will only need 1 chain. I even used my road cranks (SRAM Red) and used the road 53 tooth front chainring (took off small chainring and used the shorter track chainring bolts). You can also buy smaller chainrings (48, 49, 50, 51) for road cranks (130 bcd).


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PostPosted: Mon Jan 14, 2013 5:43 pm 
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Fastest way around the track is the black line at the bottom. Like someone above said, its the shallowest too. Cranks shouldn't be an issue. Stray too far off the black line and you add distance and increase time.

That said: you'll have to convert to FG somehow. If you have trackie friends borrow a track disk and fix the spacing/axle issue.

You can run an 1/8th" chain on 3/32" rings, but it isn't optimal.

Good luck!

M


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PostPosted: Mon Jan 14, 2013 5:44 pm 
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Just to be clear, lots of references being made to P3s in this thread. The Speed Concept is different from the P3 in two ways:
1. It has vertical dropouts
2. The SC has about 2cm more bottom bracket drop than the P3

I don't have an answer to the OPs question though


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PostPosted: Mon Jan 14, 2013 7:12 pm 
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Location: Latvia
Don't do this if you haven't done your homework. If you want to attempt the record, you should not ask that stupid questions on the forum.
Other than that, you can read a thing or two here.
I have some even more badass plans, but let's not discuss that ;)

http://www.markobaloh.com/en//index.php ... itstart=55" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

To beat this record, you should average 230-250w for 24h given that you have perfect aero position.

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PostPosted: Tue Jan 15, 2013 12:54 pm 
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I
Kasparz wrote:
Don't do this if you haven't done your homework. If you want to attempt the record, you should not ask that stupid questions on the forum.
Other than that, you can read a thing or two here.
I have some even more badass plans, but let's not discuss that ;)

http://www.markobaloh.com/en//index.php ... itstart=55" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

To beat this record, you should average 230-250w for 24h given that you have perfect aero position.


I've done my homework. I've ridden a fair few 24hr mtb races and many 12hr races. I'm planning on doing this to test as a test of my strength after an 6 month bike tour. The last time I did this, by the last month of the trip I was averaging 230km/day, 6 days a week, on a 60kg bike with 38c tyres, with less than ideal recovery conditions (sleeping in a tent on a beach, eating street food). I never tested power outputs after I got back but I wouldn't be having a go if I didn't think it was within my reach.

I don't see how it's a stupid question, I've seen cannondale slices and cervelos used on the track. The aero benefits of a SC outweigh the 2-5watt benefit in drivetrain efficiency gained by riding on a track bike. The SC has a lower BB, I was asking if anyone had ridden one on a velodrome before I potentially bin it on (someone else's) demo bike.

UMCA regulations permit the use of either a fixed gear or a geared bike for velodrome records.


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PostPosted: Tue Jan 15, 2013 2:35 pm 
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Location: Canada
I would tend to agree that this is not a stupid question.

While it is typical to run 165mm cranks on the track, I often run a 172.5mm track crank. If you are running for a record, 100% of your time will be spent below the sprinter's line, so you will not be on the banking. As you can run a geared bike for record attempts, I would recommend it, as you will be better able to manage the wind (assuming you run outdoors). Even if you have access to an indoor track, a geared bike would be an advantage as you get tired.

@kasparz :shock:


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PostPosted: Tue Jan 15, 2013 3:47 pm 
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Location: Latvia
Stupid because there is a lot of info about track record. If you read all the info about Marco - there is no more questions!
Track cranks are fine for high cadence track events. 24h with short cranks and low cadence and you'll be dead before you even get close to the record. You won't beat record on outdoor track, don't even think about that. Key to these records is very precisely measured effort, when to take water, gels, how much and what speed/power you should average for every hour.
Yes, geared bike is the only way to go, as you'll get tired, you will drop a gear or two definitely. One thing I haven't read in the rules is brakes. Sure you can remove front derailleur and small ring, but you might remove the brakes, use bolt on skewers and do as much aero tweaks as you can as it is not UCI record and UCI rules does not apply there. Don't go too far as I believe record won't be accepted with Boardman Lotus machine.

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PostPosted: Tue Jan 15, 2013 6:36 pm 
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Uhm, the banking is the same whether you are at the bottom of the track or the top of the track...........


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PostPosted: Tue Jan 15, 2013 11:10 pm 
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Kasparz wrote:
...Track cranks are fine for high cadence track events. 24h with short cranks and low cadence and you'll be dead before you even get close to the record...


Board statement with no real physiological basis. The best crank is the best crank for the riders body dimensions and comfort. Power output won't be affected on this choice unless stupid short or stupid long (below 140mm or greater than 220mm). There has been some evidence that lower cadence is better for long distance in terms of sustained power output.

Have a look at Alex Simmons blog in relation to an athletes he coached for the hour record. Some of the info could be relevant.

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Posted: Tue Jan 15, 2013 11:10 pm 


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