Wheelbuilding design decisions

I finished my first deep section carbon wheelset last week and gave it a go this weekend, and altough I couldn’t really push it hard because of a booster vaccination on Friday that left my heartrate all over the place, I’m quite content with the noticeable responsiveness of the wheels - but I do get some brake rub when sprinting / climbing out of the saddle, so it is not perfect.

This is for a rim brake CAAD12, so it is possible there’s nothing I could have done to avoid this, but I’m rather a novice in this art (this is just my fourth wheelset) and if more experienced wheelbuilders would take some time to critically comment on my design decisions and choices I would be thankful. Please be patient if this is a bit detailed (or just skip it and give me a hard time anyways, I’m a big boy)

Let’s start with noting that I’m a climber locked in the body of a track sprinter - with 95kg at 186cm height it is just as well that I’m not racing. Mid-fifties, busy work schedule and just a couple of hours to get into cycling on the weekend. I started building wheels because I figured that could be a way to change the riding experience without filling the garage with different bikes (it’s also more fun than knitting). I regularly measure peak power outputs slightly above 1200 W and can hold above 1000 W for 12 sec on a good day - that’s the kind of effort that I usually look forward to on a ride (I love punchy short climbs that can be sprinted over). My average speed on a 3h ride is between 27 and 29kph depending on elevation gain (it’s rolling hills where I live)

For this build I picked tubular rims from Carbonal, because I do like how tubulars ride and I would expect these to behave well in crosswinds with 25mm tubs (I’m not that fast, so handling under greater yaw angles matters…)
38mm front and 50mm asymmetrical rear. I planned to mount 25mm right from the start, because I know I usually don’t miss the additional comfort 28mm would give me.
asymmetricroadtubularrim_360x
carbonrim38mmtubular_360x

I also wasn’t quite ready to trust cheap Chinese clincher rimbrake wheels - and if I want to go where I’d better not take tubulars, I still have different choices.
But there’s a first question for you: Does this rim choice make sense to you? I know there are very subtle differences in shape that may have an impact on aero performance, so “it depends” counts as an answer :slight_smile:

For the hubs, I chose a set of Miche Primato Syntesi. They seem to be quite popular with a couple of pro wheelbuilders for budget builds because of their reliability, adjustability and geometry, and I like that the freehub is basically silent and that the rear axle is steel. They were also dirt cheap at € 80 the pair including shipping from a Dutch online retailer. There’s no laser engraved logo but a sticker to be peeled off, so the money seems to be spent on functionality, too.

28 spokes rear 3x and 24 spokes 2x front.

According to Freespoke that gives 7.7° NDS / 4° DS bracing angles rear at 52% tension distribution. My understanding is that this will make a stiff wheel with an acceptable compromise reg. strength. On the front wheel, I get 7° bracing angle - going radial would get this to 7.3°, but I was afraid that with 24 spokes, this would be a bit tough on the flanges - and I like the look of a crossed spoke pattern better than radial.

Any comments on the choice of hubs, lacing pattern or recommendations for future builds? € 80 for a set of hubs is not my upper limit, but for the intended purpose (changing between wheelsets according to mood and route, no racing) I certainly don’t need anything boutique.

I picked Sapim Race spokes for the front and DS rear, Lasers for NDS rear. I have built an aluminium front with 24 Laser spokes before (and am happy with it) but chose Race here to get a construction where the stiffness of the spokes matches the increased stiffnes of the carbon rim. My thinking is that brake rub would be less with a stiffer connection between rim and hub, as carbon rims seem to “tilt” around the hub rather than “flex” below the hub, as shallow aluminium rims apparently do. I was also a bit biased by listening to a Shimano representative explaining that they went to 1.8mm spokes on the front due to pro’s input whith their latest generation of wheels.
This is the part of my decision making I’m least convinced of, so I really would like some comments from more experienced wheelbuilders here.

Nipples are aluminium for the colorful bling against better judgement. I decided against using a combination of CX-Sprint and CX-Ray because I read in a Novemberbicycles blog that they tested the difference at 1 Watt for a front wheel, and Flo had it at 9s over 40km - so that wouldn’t be worth the huge price difference - considering I am building this in my own time and don’t have to pay for the increased hassle of round spokes winding up easier than bladed ones.

Spoke tension front and read DS is ~ 120kgf according to my Unior tensiometer. The rims seem to be quite even, and so is the tension across spokes (should be less than 10% distribution).

For the record: These wheels weigh in at just below 1500g w/o skewers and cost me € 420 including shipping to Germany from China (rims) and Holland (hubs, spokes from two different retailers)

Pictures below show them with PMP titanium skewers - I put them in because the color contrast is strikingly beautiful, but probably they are the source of the brake rub and I should rather get some good heavy Ultegra ones for € 20 the pair.

So - what do you make of this?

I don’t know too much about hub geometries, but considering that you weigh 95kg, I think you need a build slightly more robust than the average rider. I weigh 60kg and I get rear brake rub with 24 CX-Rays. I have to run my brakes fairly wide to avoid it. This is with DT hubs and 56mm rims, if that matters.

I think rear wheel aero doesn’t matter nearly as much as the front. I’d start with rebuilding the wheel with Sapim Strong or something, and if that isn’t enough, then consider a hub with better geometry and/or more spokes.

AFAIK, the Miche Primato’s give a slightly “better” geometry than DT hubs - if better means larger bracing angles and therefore increased lateral stiffness.

As brake rub with carbon rim brake wheels seems be a result of tilting a construction that is more stiff than aluminium around the hub axle, I’m not sure if having even more or stronger spokes will help: it’s probably a function of the stiffness of the flanges or the axle or the hub-shell or finally the frame’s rear triangle.

But thanks for your comment, anyways: I don’t know about your W/kg peak ratio, of course, but if you experience the same issue at 60kg the performance of my homemades is probably still okay.

A pity this thread doesn’t seem to take off.

Is there any chance the flex is in the frame and you are noticing it because your wheels are stiffer and thus flexing the frame more? Seems like a pretty stiff wheel.

It’s a lot stiffer radially and certainly stiffer laterally than my shallow aluminium wheels - accelerating really is a lot of fun! So it can be the frame (can’t do anything about that) or the skewers (easy) or the wheel (complex and interesting)

Agreed. I don’t have the knowledge to contribute anything useful, unfortunately, but I am following with interest.

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Shimano internal cam skewers are a good call - much higher clamping force.

I’ve never built deep carbon wheels so I can’t comment on this build. All rims are different and so there are so many variables in the mix which have so many different results. Deeper wheels have shorter spokes and results in a shorter triangle in relation to the flanges, further increasing strength.

Your build looks pretty stout and my personal belief is that additional front wheel lateral stiffness is important for good control, especially if you are a heavier rider. Choosing round spokes as you did should make for very stiff wheels.

I owned some Velomax Ascent II’s which were an old model for climbing and it had round spokes as well as an asymetrical rear rim. Those were really light and laterally stiff. I wish I hadn’t sold them.

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Found an old rant from @James_Huang where he said as much - and as I won’t dump the frame and Ultegra skewers are as available as they are cheap, I might go there first.

If this doesn’t help I’ll have an excuse for a new wheelset project - unless a real expert turns up and confirms there’s just no way this can be done with reasonable effort and expenses.

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A good screwer is indeed a good place to start :slight_smile:

Edit: skewer dammit ^^

French Freudian finking :stuck_out_tongue_winking_eye:

Damn, I’m butchering my th again!

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I had to google some but think I found those Velomax Ascent II (but Velocity rims, indeed)

They remind me of my pmp RS04, 20/24 spoke aluminium at 1340g the set. Incredibly fun to ride even at my weight - these are the wheels that convinced me that changing the hoops once in a while really makes a big difference in the entertainment value of a well known route.

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:laughing:

You hefe to be careful vif fat “th” :stuck_out_tongue_winking_eye:

Note that in French the same sentence with “corkscrew” instead of “screwer” (or skewer) works even better :wink:

More seriously, when I was a true weight weenie, I used light skewers (39 grams a pair precisely). Once I was lazy and used the heavy Dura Ace ones that were mounted on the winter wheels instead of changing them, and I could tell the difference. I only use Dura Ace or Campa / Fulcrum skewer (Shamal or Bora style)now, both are heavy and efficient, and the bike feels better, even if it’s 80 or 90 grams heavier ^^

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I must admit that you lost me here completely. It’s been a while since I regularly spent time in France, and I may have missed it anyway - but I’m absolutely not aware of any suggestive meaning in tire-bouchon.

“The French prefer a glass of claret” ?

I ordered some Ultegra corkscrews yesterday, let’s see how that will work out.

Edit: just noticed your edit.

The Comedie of Errors

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No suggestive meaning associated with corkscrew, but also none with screwer, or skewer …

Just meant that in France a corkscrew is a good way to start because we like a good drink for any occasion really.

I like the “Ultegra corkscrews” :laughing: If that doesn’t work, you’ll be left with a big Campa corkscrew to forget about it all :slight_smile:

With respect to quick releases, I was previously pretty skeptical about rigidity differences between brand/designs. However, I recently acquired a lightly used set of Zipp 404s with their very light/delicate feeling Ti shaft QRs and was experiencing minor noises from the rear wheel with hard efforts on steep inclines (I am ~85 kg). Not sure what was the source of the noise but put on a set of old style Campagnolo QRs (Al heads/levers but not the newer Zonda/Bullet/Scirocco design) and the noises disappeared. So my anecdata aligns with other’s comments regarding impact of presumably more rigid QR.

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Funnily enough the Zipp Ti skewers were the only lightweight ones that I found were any good but I’m 20kg lighter than you to be fair.

All other lightweight ones were rubbish and would cause creaking.

Otherwise aside from Shimano/Campag skewers, I also had good experiences with DT Swiss RWS skewers.

Sorry, are people suggesting that there’s a difference between skewers made of the same material in terms of how much the hub is allowed to move? I would hope that if you can achieve sufficient clamping force to remove all slop, then all steel skewers would perform similarly. IMO the primary benefit of an internal cam skewer is that it doesn’t seize.

Ti skewers don’t work as well simply because Ti is about twice as stretchy. No amount of extra clamping force is going to change that. The spring rate of metal is mostly constant.

Corrections are welcome.

EDIT: Oh my god my reading comprehension is garbage. The original post mentions Ti Skewers. Yes, please get some steel skewers before rebuilding the wheel. Ti skewers are barely advisable for light riders.

:wink:

I’ll check with recommended and stock steel skewers this weekend and report.

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…but for now, here’s some reading material that indicates there’s a difference in clamping force over closing torque that can be quite significant between designs (I’d say up to double the clamping force for the same closing torque)

http://kuktl.dept.ku.edu/bicycle/QRReport1.pdf

Methinks this is mostly a function of the diameter of the skewer axle and the geometry of the closing mechanism.

Oh there’s a huge difference in clamping force. I have no doubt about that. But the counterintuitive thing about a constant spring rate is that no matter how much preload you put on it (within a small range), the amount of stretch caused by a given amount of additional force is the same.

The main reason you want higher clamping force is that it increases the amount of friction between the hub and dropouts, so you’re less likely to eject a wheel. But that’s not a huge concern unless you use garbage skewers so loosely that they don’t require effort to open.

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