Is a 30mm rim "aero" enough

Walrus said:

I'm considering a set of "aero" road wheels and want to get some opinion on whether 30mm rims offer a reasonable aero advantage? I would be riding these wheels on flat, straight roads. I currently ride 22mm rims...will I notice a difference going to 30mm? Should I look for something bigger, like 40 or 50? The reason I ask is that there are some very affordable wheels with 30mm rims, but anything bigger seems to jump a lot in price.

Is there any literature on how high the rim needs to be before benefits can be worthwhile?

I would have a look at 50mm rims if you want the aero effect. I think the HED Jet 50 is a pretty reasonable $995.

hedcycling.comjet50.phpOpen ↗

Perhaps John can answer your question. cycling.net.aut350127.htmlOpen ↗

You would need to couple them up with skinny 19-20mm tyres to have the best effect. I use Velocity Deep-V on my Try bike with 23mm tyres, its slightly faster than standard wheels but for me its not worth paying $$500 more (for Hed).

Walrus said:

I'm considering a set

I guess the bottom line is that you're unlikely to notice much difference with a 30mm deep rim. If you do buy some, and they feel faster, it would most likely be coz you'd have brand new hubs, and the fact that 30mm rims are noticeably stiffer.

531Aussie said:

I guess the bottom line is that you're unlikely to notice much difference with a 30mm deep rim. If you do buy some, and they feel faster, it would most likely be coz you'd have brand new hubs, and the fact that 30mm rims are noticeably stiffer.

My 30mm rims are all faster than my 20-24mm rims...however the 30mm rims have less spokes which is probably the reason.

kleng said:

I would have a look at 50mm rims if you want the aero effect. I think the HED Jet 50 is a pretty reasonable $995.

hedcycling.comjet50.phpOpen ↗

I like the Jet's, but they are 4.5 times more expensive than something like Easton Vista's which you can get for $220 a set. So the question is, given there are such cheap 30mm rims available, will there be any significant aero effect. Obviously hub quality etc comes into it as well.

Walrus said:

I like the Jet's, but they are 4.5 times more expensive than something like Easton Vista's which you can get for $220 a set. So the question is, given there are such cheap 30mm rims available, will there be any significant aero effect. Obviously hub quality etc comes into it as well.

The problem with aero rims above 30mm is that there is often a weight penalty, so if your'e not doing tt's or flat road riding I think going something like the HED I suggested is overkill. I don't think there is any difference from aero point of view between a 30 and your22mm rims. If your not too heavy I think a light set of hubs and rims would be a good place to get the performance gains your seeking or even changing your tyres and tubes can reduce weight and rolling resistance.

kleng said:

The problem with aero rims above 30mm is that there is often a weight penalty, so if your'e not doing tt's or flat road riding I think going something like the HED I suggested is overkill. I don't think there is any difference from aero point of view between a 30 and your22mm rims. If your not too heavy I think a light set of hubs and rims would be a good place to get the performance gains your seeking or even changing your tyres and tubes can reduce weight and rolling resistance.

Reynolds Stratus DV Tubulars: 46mm deep rim; sturdy and everyday useable; and at 1258g (actual weight for my set), no weight penalty. Muy nice.

According to Zipp and Hed, you need more than 30mm to get aero benefits (the Zipp303 are more than 30mm deep, despite the naming convention, and 40mm seems to be the favored rim depth). Of course, even with 24mm or 30mm rims, you can get some aero benefit by reducing spoke count, but your question related to rim depth. But as has been pointed out, deeper aluminum rims carry a weight penalty, and I doubt you would see any benefit by going from 24mm to 30mm rims, unless you drop spoke count in the process. The deeper aero wheels are all carbon fiber, which is why the price jumps up; unfortunately there is a lot of truth in the old "you get what you pay for."

alienator said:

Reynolds Stratus DV Tubulars: 46mm deep rim; sturdy and everyday useable; and at 1258g (actual weight for my set), no weight penalty. Muy nice.

Is there a price penalty though ?

palewin said:

According to Zipp and Hed, you need more than 30mm to get aero benefits (the Zipp303 are more than 30mm deep, despite the naming convention, and 40mm seems to be the favored rim depth). Of course, even with 24mm or 30mm rims, you can get some aero benefit by reducing spoke count, but your question related to rim depth. But as has been pointed out, deeper aluminum rims carry a weight penalty, and I doubt you would see any benefit by going from 24mm to 30mm rims, unless you drop spoke count in the process. The deeper aero wheels are all carbon fiber, which is why the price jumps up; unfortunately there is a lot of truth in the old "you get what you pay for."

Let me offer a direct comparison. I have a very nice wheelset, and I know that these aero's I'm considering won't compare in quality to what I currently have...I'm interested in whether I'll notice a difference in effort required on flat roads due to the aero profile. Also, having these wheels will mean I'm riding my "good" climbing wheels less during training.

Current Wheelset: DT Swiss 1450 22mm rim, 32 spoke, 1450g, std profile
Proposed Wheelset: Easton Vista = 30mm rim, 20/24 spoke, 1797g, parobolic aero profile.

To investigate, I've used this calculator (2peak.compowercalculator.phpOpen ↗) substituting my DT's for Mavic SL's (very similar) and the Eastons for Citec 3000's (also very simliar). The result was that at 30kph, I would only save 3 watts by riding the aero wheel. Not much, but when you consider there's a 350g+ weight difference...it shows that there is a benefit.

kleng said:

Is there a price penalty though ?

I think he was just disputing the comment that rims above 30mm weigh more. Obviously the Reynolds are more expensive.

Only 3 watts!!! :eek:

As I said in my earlier post, a smooth skinny tyre at the front will do more, Conti Attack or GP4000. 🙂

Remember at 30kph the top of the tyre is doing 60kph, so tread drag is important.

gclark8 said:

Remember at 30kph the top of the tyre is doing 60kph, so tread drag is important.

Good point. Those tyres you mentioned would be my first choices. 😉

3 watts is basically nothing I know, it's just interesting that despite the weight diff, the aero's still outperform.

Walrus said:

Good point. Those tyres you mentioned would be my first choices. 😉

3 watts is basically nothing I know, it's just interesting that despite the weight diff, the aero's still outperform.

Traveling at a constant speed over flat ground, excess bike weight has almost no effect on drag, as it makes up such a small part of rolling resistance; so I'm not surprised that you save energy with the aero wheels. You'd likely notice more of a qualitative difference in how the wheels behave under dynamic conditions e.g., when accelerating or climbing.

The DT 1450's you have right now are a great wheelset; the vista's are fine but not exactly a top shelf wheel. I'd stick with what you've got and work on your body position on the bike if you want to get more aero, since that's where most drag comes from.

tetsuryuu said:

Traveling at a constant speed over flat ground, excess bike weight has almost no effect on drag, as it makes up such a small part of rolling resistance; so I'm not surprised that you save energy with the aero wheels. You'd likely notice more of a qualitative difference in how the wheels behave under dynamic conditions e.g., when accelerating or climbing.

The DT 1450's you have right now are a great wheelset; the vista's are fine but not exactly a top shelf wheel. I'd stick with what you've got and work on your body position on the bike if you want to get more aero, since that's where most drag comes from.

A lot of what you say makes sense and I've read similar research elsewhere to back it up so thanks! This is definitely a "training" set...just toying with the idea of an aero wheelset to i) be faster on flats and ii) save my other wheels from being ridden all the time.

Thanks everyone for their input.