Flatballer

Unless you're on something steeper than 45* or so (shorter than 250m) I wouldn't worry about it. Yes, people strike pedals, but usually only because they're going too slow on the roll out lap. Sprinters drop to the band in the corners when going slow, so it isn't even really a problem for them, although they're the only ones who tactically it makes any difference at all.

calamarichris

Thanks Koogar and Flatballer.
I'm 6'2" and have been spinning 175 & 177.5 on the road at 120+ sustained with no problem, so was considering building up my bike with a 172.5. Will probably experiment with shorter cranks and higher rpm soon, but I'm currently having better times and more competitive with that 172.5 and a slightly taller gear (50-15).
It's a GT Pulse, and I found one source (admittedly unconfirmed internet scuttlebutt) that said the bottom bracket has only a 40mm bottom bracket drop, and I'm using Shimano SPD pedals, and riding on San Diego's 333m concrete track.
We'll see what the Pulse's actual BB drop is when I get it this weekend.

Currently riding a Leader 735 loaner, which has about 55mm BB drop and 172.5 cranks. Had the whole drome to myself yesterday and wasn't able to get the left pedal to hit despite several stupid attempts, even nudging steeper while riding in the blue at full squirt.

700wheel

Just for info:
Some tracks specify crank length and BB height. For example see the Manchester Velodrome requirements here:
Track bike specification - National Cycling Centre

I do not know if any US tracks have similar requirements.

I have the feeling top riders are not held to these requirements at Manchester.

calamarichris

I can see how indoor 250 wood tracks would want to protect their boards.
I don't foresee actually getting good/serious enough to travel up to Carson (my nearest indoor drome), and San Diego makes no mention of crank length (or any other bike requirements at all), so I might experiment with 172.5 & 175 cranks.

Next question: not advisable to adjust the bottom bracket cups to tune the chainline and reduce the chain noise?

Using Phil Tenacious on the chain quieted it a little, but that aluminum Leader frame is like a megaphone for any chain noise. I prefer not to broadcast my moves.

Koogar

I've got some bad news, man: you're riding around the track in the wrong direction In all seriousness, I think I get the gist of what you were trying to do and I'd suggest being careful with these experiments. On a lower friction surface like a wood track, you could easily slide before you get a (right) pedal strike, and you might not be able to catch it in time. Both are most likely to occur when you're slow and in (or entering) a turn.

I don't know anyone who does this. Track bikes are often noisy. First it bugs you, then you ignore it, then you start wanting to get a disc wheel in part because of the woo-woo sound, even though you'll tell everyone it's because it's worth 0.1s in the 200 or something like that....

dunderhi

A tight chain is a noisy chain, so bit of play helps.

It may not matter since in track racing, surprises are rare - we're a vocal bunch.

gycho77

This is so true

700wheel

Lots of beginners ride Carson. Take a class or certification. It is so neat to ride on an indoor track. The first thing I noticed riding there was the noise my helmet straps made.

By the way there is a world cup scheduled for Carson Feb 25 & 26 next year. I plan to attend then get some warm (hopefully) weather training in either San Diego or Palm Desert.

taras0000

You are right about large diameter aluminum magnifying your bike's noises. Also, tight chain will be noisy, as well as a new one (along with new cogs and rings). If your set-up has less than 100 miles on it, then you will get some more noise than normal. A little bit of synchronous wear will really quiet your set up.

How is your chainline? What sort of gear makes up your driveline? How much slack do you have in your chain?

happybday29475

Crank Length Anecdote:
I'm 6'2" also, and I rode on the road for years using 175mm cranks, and loved them. Also had 175mm on my MTB and CX bikes.

Then I got into track, and learned that trackies used shorter cranks, and arbitrarily chose 170mm for the track bike. Around the same time, I got a second road bike, and, due to a temporary injury, was recommended a shorter crank on that, too...and went 172.5mm.

Now, I switch back and forth between road bikes...but I can hardly stand the longer 175mm cranks; they feel awkward and slow. Also, my max cadence is hugely higher on the 172.5mm.

All this for 2.5mm...it's surprising when one considers just how tiny 2.5mm is...

calamarichris

That's cool! I'm going to have to come spectate in February.
We've got some pretty spectacular roads here in North San Diego County, if you want to meet for a spin while you're here. (Most of our microbreweries are regrettably still on this overhopped IPA fad.) I've got a few spare road bikes laying around if you aren't another of these chocolate factory employees.

Do these indoor tracks have a fast-track to certification if we've already gotten certified on another track? I'm nearly done with my classes at San Diego. They're going to close it next month for resurfacing, and I'm looking forward to a nice smooth track in October.

calamarichris

It's not "just 2.5mm", that's an additional half centimeter added to the diameter (or an extra ~33mm added to the circumference) your legs are traveling! I have no problem spinning my 175 for minutes at a time, but my knees start bouncing off my collarbones with the 177.5 at 120rpm.
Funny how much easier 175 seems to spool up after trying to do it on the 177.5's.

queerpunk

There are usually two things to certification. One is, knowing how to ride your bike on a track: knowing what the lines are for, how to move, etc. The other is understanding how to ride on a steep 250. Some indoor tracks can do away with the latter but will still ask new riders to go through a class on the former before racing or training.

carleton

+1

Further, the surface of the ADT/Home Depot/Carson/whatever it's called track is similar to a wooden basketball court. Any dust on the tires will allow them to slip.

if you slide out on a concrete track, you only damage your bike and maybe your skinsuit. If you slide out on a wooden track, you also damage the track. Which may gouge the wood which could make splinters and/or be expensive to repair. So, you'll see track director of nicer wooden tracks be real hard-asses about that kind of stuff...for good reason.

Also, riding a 250 will give you the willies. I came from DLV (37 degrees) which is really steep, but not 44 degrees. Riding on my first 250 (Frisco Superdrome) gave me the willies for the first few laps. It just does.

This is why you can't just say, "I'm good." and hop on a 250. They want to make sure you are good. The $10-20 entry fee you pay that day won't be enough to cover damage you do to the track if you slide out.

calamarichris

Good poop, thanks trackies!

I know you guys've probably been answering these annoying noob questions for years, but I appreciate your taking the time to teach me new stuff.

calamarichris

Sorry I missed your questions before Taras. It's a loaner Leader 735 with pretty-well-worn FSA chainring and unknown-brand cogs. It's a dual/flippable hub with 16T & 15T cogs. It's noticeably louder on the 16T.
I'm not sure how to check or to tune the chainline, (short of ensuring that rear wheel is absolutely centered when tightening down the axle nuts), but most people chuckle and blow their bangs off their hipster foreheads when I ask; (I suspect they don't know either.)

I'm also not sure how much slack in the chain is enough. Anyone have any specific guidelines or links?
Most of the guides I've found so far been a little imprecise for my tastes. Been a roadie & motorcyclist for years, have always done my own meticulous wrenching, and have developed the completely irrational idea that noise = squandered energy.

Thank you very much for sharing your guidance about the new drivetrains Taras.

queerpunk

It's easier to show than to tell how much chain slack is right. You should be able to touch the chain where it's halfway between the ring and the cog, and it should have I'd say about an inch of vertical play.

Another way to test to see if your slack is too much is to push on the chain where it meets your chainring. Try to push it up and over a tooth - ie, try to derail it. If you can't, then, it ain't coming off. If you think you maaaaaybe can, then, well, it's probably not coming off.

queerpunk

Oh, and, how to check the chainline is to measure from the center of the seat tube to the center of the chainring teeth. it should be 42.5 - almost every track hub in the world puts a cog at 42.5mm.

There's not a lot of finetuning a chainline - for the most part, people buy the BB that matches their cranks, and just set it up - and the ring goes where it ought to.

Koogar

"Loose is fast." Colby Pearce's primer on this subject is good:

Track Chain Tension Primer - Pearce Coaching and Fitting

(Ignore the silly carbon frame in the picture)

calamarichris

It's probably starting to sound stale at this point, but THANK YOU again!

What do you think about using a straight edge/level to check the chainline? Holding a 6-foot level flush against the chainring and seeing where it lines up in relation to the cog? I've been doing this with motorcycles for years to good effect--my chains typically last twice as long as anyone I know, and still have some life left when I replace them compared to many of the neglected chains I see still in use.
Some folks call it OCD, I prefer to call it Mechanical Empathy.
As a wise man once said, "A clean, well adjusted, well-lubed bike goes faster, lasts longer, and looks nicer."

Bandera

That was the Old School Step 4 after:

1) Face BB shell
2) Check frame alignment (we used a flat table being really old school in our shop).
3) Check track end alignment/parallel w/ proper "dropout" tool (pic)
4) Position the straight edge on the chainring center and cog center of the race wheel
5) Listen for that sweet-spot "whirr" w/ chain installed & tensioned
6) Race

-Bandera

calamarichris

Sorry running a little late with the Noob Question of the Day: Any reason not to cut a link out of the chain to bring the rear wheel up closer to the seat tube for improved aerodynamics?

And is it safe to assume that doing so would bring the wheel about one linkplate's length forward?

seau grateau

Seems like it would limit your options for easily changing gearing, and I doubt any potential aero benefit would really be worth it.

700wheel

You would have to remove two* links to use most connectors or to install rivet. (*then the wheel would move 1/2" forward.)
Another way to decrease wheel/seat tube clearance is to use a different chain ring/sprocket combination.

There are much better ways to reduce aerodynamic drag.

carleton

Ever watch a rear derailleur on a road bike? Ever notice how it takes and gives chain based on what chainring/cog is chosen?

Now imagine if you had no rear derailleur and a single track chain from your big front chainring to your small rear cog. What happens when you want to put the chain on a different chainring or cog? You either have too much chain or not enough. So, you'd need a chain for each gear combination.

This is why track ends (aka: track dropouts) are horizontal. To give or take slack to optimize the chain length...if the chain is long enough. If you cut your chain to the shortest length usable you just shot your self in the foot and undermined the entire system.

The shorter answer is: Go ahead and try your idea. You'll find out soon enough why it's a bad idea

The only people that can get away with it are single speed / fixed gear riders who never change their chainring/cog combination.