Best track rim profile

Everything about building wheels, glueing tubs, etc.
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LouisN
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by LouisN

HI all track racers,

I will be building two track wheelsets for next season.
The riders finally can get whatever rims they want (they were limited as U17 cat. to 38mm alloy rims before).
The riders are 17 yrs old girls, they weight 115 lbs ( 53kg).

Now I'm looking to get the best carbon rim profile for all events.
So wich profile would be best ( depth, width )? I'll definitely build them as tubular.

I'm thinking either 60-60 mm X 21 mm width, or even 60-90 mm.
Low spoke count, big spokes.

Louis :)

TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Why not a disc rear? Or is this a particularly windy outdoor velodrome?

by Weenie


hambini
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Joined: Tue Nov 15, 2016 8:13 am

by hambini

I would get a disc on the back, 80mm on the front.

The rim profile doesn't make as much difference as the depth. It's a basic law of physics, beyond approx 12 degrees the flow will detach. If you have a bigger rim depth then it will travel further along the wheel before it detaches.

Hambini

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LouisN
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by LouisN

Disc is an option, but it exceeds my wheel building skills :lol: .
I've been looking at some Zipp 182 conversion axles for a long time without success ( I have two older Zipp 900 road discs) :( ...
And I'va got some 20-24H track hubs at home.
So deeper is better right ? Cool :thumbup:
EDIT: Hambini, I read and watched your stuff, interesting !! Coincidence, a retired friend of mine used to sell bearings as a job for industrial purposes suggested I used NTN LLB-C3 bearings, and remove the seals, that it would be better and cheaper than buying Ceramicspeed ;) .

Louis :)

hambini
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Joined: Tue Nov 15, 2016 8:13 am

by hambini

LouisN wrote:
Wed Aug 01, 2018 11:03 pm
Disc is an option, but it exceeds my wheel building skills :lol: .
I've been looking at some Zipp 182 conversion axles for a long time without success ( I have two older Zipp 900 road discs) :( ...
And I'va got some 20-24H track hubs at home.
So deeper is better right ? Cool :thumbup:
EDIT: Hambini, I read and watched your stuff, interesting !! Coincidence, a retired friend of mine used to sell bearings as a job for industrial purposes suggested I used NTN LLB-C3 bearings, and remove the seals, that it would be better and cheaper than buying Ceramicspeed ;) .

Louis :)
I would agree with your friend! Although if you are removing the seals, you might as well buy an unsealed bearing.

Marin
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by Marin

Hmm I disagree, track tests have shown that at 0° yaw the biggest factors are width and spoke count. Ideally, you'll get front hubs with narrow flange spacing, few spokes and realatively narrow rims.

Still, tall rims will help to lower the spoke count and by keeing the spokes short.

gramsqueen
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by gramsqueen

How are the max power outputs of these riders? Maybe going too deep would hinder their acceleration

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LouisN
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by LouisN

They are road riders looking to improve their speed on the track.
They can already be "fitted" in the endurance track racers category.
So track work will mostly be from the 500m TT and 2km pursuit (women's junior distance) to the bunch events, more than for specific sprint events.
5sec. = 17 Watts/kg
2 min. = 6.5 Watts/kg
And so on...
I doubt that even the deepest 90mm carbon rim wheel will be harder to push than their original 2kg+ shallow Felt TKR wheelsets :) .

Louis :)

istigatrice
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by istigatrice

Ok, so this goes against everything that you've outlined,

I really hate low spoke count deep rims - they're not stiff enough once you're up to speed on the banking. I think it's related to the fact that the rims are super stiff, but the spokes aren't so you obtain a lot of flex in the spokes. I'm sure Hambini et al will be able to explain the physics behind this, but I swear what's stiff enough for road is rarely stiff enough for track (centripedal force or whatever).

Hence, even if you're allowed to ride whatever, I'd still get some H+Son Archetype rims laced with a lot of bladed spokes to Dura Ace or Campy Record pista hubs (depending on budget). I'm not sure which hubs you've currently got, but unless you're very lucky and got your hands on some 20/24 DA or DT swiss hubs they're probably junk - I'd sell them to some hipster fixie rider. Veloflex (if it's outdoor/indoor) or Vittoria pista tyres (purely indoor), latex tubes. Clinchers and fairly shallow, but they don't have the same problem with super stiff rim + few flexy spokes. If you're patient with the hubs you can get them running super smooth, and despite what people say, clinchers are fine indoors (and probably faster if any of these rolling resistance tests are to be believed).

I might be going a bit overboard though, but I think there's a lot more to a good track wheel than an aerodynamic rim and few spokes. It isn't like road and at the very least if you're looking for speed I'd recommend making sure you have some 'proper' hubs. I'd also suggest 24/24 thick bladed spokes as a minimum, but I'd still recommend either 32 or 36. Then again, if you're really looking for speed on a budget just get a FFWD 5 spoke and disc.

EDIT: just saw the above post - definetley recommend the H+Son/Campy pista hub option. Solid reliable wheel that won't throw up any handling surprises at speed, and super quick under a quick rider as well :wink:
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

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LouisN
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by LouisN

Hummm :?
I already have some heavy, shallow alloy rims, with lots of big spokes, wheels.
Not sure I believe a 115 lbs U19W rider can bend a 80 mm rim built to some 220 mm straight gauge or thick aero spokes on flat wooden terrain.
The centrifugal force is wayyy higher IMO in a road race turn after a 75-80 km/h descent on bad quality tarmac.
And I doubt very much they will improve their 500m TT times, or their 2K pursuit times on the wheels you describe over some 80mm wheels.
Remember these are not for 90 kg sprint or Keirin specialists ;).
We don't have the same definition of budget. 5 spokes front and disc rear are worth more than a whole season funding for me, so pretty much out of the question... :oops:

Louis :)

1llum4
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Joined: Thu Jul 12, 2018 6:00 am

by 1llum4

Since track racing have limited yaw angle the most important aerodynamic aspect would be to match the tire actual width with the rim outer width with the 105% rule.Since most track frame can only take 23mm tire, that would mean 24 outer width rims minimum.

For lighter rider especially if they will be riding outdoor, I would go with a 60mm/60mm combo. One word of advice for track wheelset is to get a double side threaded hub so you can have 2 cog size on at all time to simplify gear selection during race day and training day.

Rim shape difference is less important than proper tire width fitting with the 105% rule in terms of aerodynamics.

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ergott
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by ergott

You can get something like a lightbicycle carbon rim in a higher spoke count, say 24/24 for them. That's probably a good balance between stiffness and aerosynamics on the track.

If you're patient, look for someone selling older, narrow carbon wheels/rims and grab to rears for the higher spoke counts. They have almost no resale value anymore and its true that the narrower rims will be more aero at 0 yaw on track. Look for Enve or Edge Composites 65mm rims, Reynolds SDV66 or similar. The rear wheels were typically 24 spoke or 20 spoke.

istigatrice
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by istigatrice

LouisN wrote:
Sat Aug 04, 2018 1:48 pm
And I doubt very much they will improve their 500m TT times, or their 2K pursuit times on the wheels you describe over some 80mm wheels.
Here's the key point, it's the rider that makes a bike fast, not the wheels. If you're chasing your best time don't bother with anything but campy/mavic discs, and if it's just to improve your road you'd argubably want just any old thing because it's the delta (change in time) that matters more.

If it's a (windy) outdoor track I'd suggest that 60mm is too deep (handling deep wheels on a swirling track at 60kmph is not my idea of 'safe'), and if it's an indoor track with a sensible banking then I doubt 20 spokes is going to be stiff enough (in fact the stiffer rim would make this worse). When you're cornering at 80kmph on the road I doubt you're ALSO applying maximum power through the bike (as you sometimes would on the track).

Basically, what I'm suggesting is that if you can't afford a high quality 5 spoke and disc, high quality hubs and rims would be a better purchase IMO. Cheap carbon with cheap hubs may seem more aerodynamic, but the overal performance will be lower (hub friction, stripping threads, stiffness, easier to change wheels). If you get/or have high quality hubs I do think Ergott's suggestion could be quite sound, Zipp 404 stallion rims could be another option. I do like the idea of mid-depth 50-60mm deep rims with thick 24/24 or 28/28 spokes on high quality hubs (pity you can't get campy or DA hubs easily in those options).

I know they're not 90kg, but if they take the 500m seriously they'd be putting a lot of force through the bike and I just don't think what you're suggesting will cut it. JW15 and JW17 can still flex/break wheels. At the same time, if they ride the 500m like roadies there shouldn't be an issue - but if the idea is to improve their strength you'd hope they weren't riding the 500m like roadies.

So my TL;DR is that I wouldn't spend more money chasing aero gains, if you have to spend the money, spend it on things that make the bike 'nicer' overall. If you needed the aero your local academy should loan you a Comete/Ghibili and iO :wink:
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

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LouisN
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by LouisN

Ha!Ha! If academies in AUS have these wheels hanging around, they're budget is better than our state or even national program ;)...
Our all-time best track racer had to buy her own tubulars and borrow wheels ( one from France and one AUS) at the 04' Olympics for her gold medal ;).
I will for shure check for different types of high profile rims and go from there :thumbup:
I really hate low spoke count deep rims - they're not stiff enough once you're up to speed on the banking
What kind of experience on the track do you have ? is it from the usual equipment ( of course, the equipment you mentioned all the academies should provide their pupils with ;) ) you see that's used on the local AUS tracks daily, or based on verified, compared data ?

Louis :)

istigatrice
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by istigatrice

My cycling club used to share training sessions with the local state academy (in fact our club coach became the sprint coach), so I've heard a lot of this from the mechanics/riders/coaches. My personal experience is with a road front wheel (with a track adapter) but soon learnt my lesson with that - the bike felt vague. I haven't used the expensive stuff mostly because I'm nowwhere near fast enough to justify it. The coaches/riders/mechanics here are willing to share their knowledge if you ask (and they're not busy with their riders) - I asked about race wheels they told me not to bother unless I could get a "quality" (which for them meant Mavic/Campy) disc and 5 spoke. Some of the athletes have used the FFWD stuff before and swear by them so I guess they're ok too. Mixed opinions about the Chinese stuff - some of the coaches/mechanics hate it (frames are too stiff, wheel rims aren't actually circular), while a minority of riders use it for training (with mixed reviews, the most positive ones I'm aware of are the Curve and TWE rims - I don't know where they source their stuff though, but have a suspicion it's Chinese). Exclusively 50-60mm rims (and clinchers) if that helps. So obviously not A priority race wheels, but for training and B priority races.

So a lot of third hand information :smartass: but from (what I presume are) credible sources. Hope it helps since (with my limited) knowledge about track it feels like you might want to err in a direction slightly differently to what you had originally planned :beerchug:
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

by Weenie


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