Deciding between two DT swiss aluminium rims

[robertbb]

Analysis paralysis, help needed.

I've got some DT 350 Centrelock hubs (28h/28h) and looking for a tubeless DT rim to use with them.

(Yes I know there's Easton, and Hed, and Kinlin, and, and, and... so please don't go there. I am looking at DT swiss rims because I can get them far more easily).

My riding is 65% paved tarmac, 35% smooth champagne gravel (think rail trails) and the very occasional rougher gravel section.

I weigh 70kg, the bike would vary between 8-11kg depending on load carried.

DT RR421: Assymetric. 20mm internal. 24mm external. 21mm height.
DT RR481: Symmetric. 22mm internal. 26mm external. 25mm height.

Smallest tyre I will run will be a 30mm. Largest will be a 35-38mm. Though there mayyyy be a chance I will ride a 40-42 in the future (currently no bike in my stable with clearance for that).

Which rim and why? Granted the RR481 has slightly more modern dimensions but would the RR421 build into a better wheel considering the asymmetric profile?

Bonus question: DT aerolites x28. Sufficient? I went with the extra 4 holes per hub after reading something from November Dave (and others similar) basically saying never rely on spoke gauge to do what spoke count should be doing. I think for my weight and riding style, something like an Aero Comp would be overkill but open to suggestions (e.g. Aero Comp rear drive side? Does this depend on which rim I choose?)

Thanks!

[Peter P.]

Asymmetric rims for the win!

I have built many with O/C rear rims; they last longer and flex less laterally.

I'd also stick to round spokes and brass nipples.

Aero spokes reduce that lateral stiffness and any gains are marginal.

Brass nipples because they won't gall or crack like aluminum nipples.

[robertbb]

Originally Posted by Peter P.

Asymmetric rims for the win!

I have built many with O/C rear rims; they last longer and flex less laterally.

I'd also stick to round spokes and brass nipples.

Aero spokes reduce that lateral stiffness and any gains are marginal.

Brass nipples because they won't gall or crack like aluminum nipples.

It'd be a no-brainer if I could get the asymmetric rim with the RR481 dimensions. I'm just concerned that a 20mm inner width (nor a 22mm outer width) wide enough for where bikes and tyres are going...

[Xrslug]

Given your use case, I’d go with the wider internal width rims. But I would also ping member Peter Chisholm (OldPotatoe) for his advice as I know he builds with DT rims (I am a happy customer):
https://forums.thepaceline.net/member.php?u=28701

[coffeecherrypie]

Originally Posted by robertbb

It'd be a no-brainer if I could get the asymmetric rim with the RR481 dimensions. I'm just concerned that a 20mm inner width (nor a 22mm outer width) wide enough for where bikes and tyres are going...

Just a data point for you, on my gravel bike I run 38 mm tires on A23s which have an internal rim width of 18mm and it’s fine

[Wunder]

Originally Posted by coffeecherrypie

Just a data point for you, on my gravel bike I run 38 mm tires on A23s which have an internal rim width of 18mm and it’s fine

20mm internal also isn’t exactly narrow. It’s not crazy wide but for rim brake alloy it’s about as wide as it ever got (HED+ are 21), yes I know discs can go wider. 20 or even 18 can certainly support a 30-40mm tire well.

On the asymmetric bit I have more experience with rim but I thought their value was reduced with disc brakes. A disc rear has much less difference between the two flange widths as you now have a rotor on the NDS. I thought for disc wheels you actually are more likely to use an assym up front and use a symmetric rear (the opposite of how they were used for rim brake wheels).

What are the rim weights?

[Mark McM]

Originally Posted by Wunder

On the asymmetric bit I have more experience with rim but I thought their value was reduced with disc brakes. A disc rear has much less difference between the two flange widths as you now have a rotor on the NDS. I thought for disc wheels you actually are more likely to use an assym up front and use a symmetric rear (the opposite of how they were used for rim brake wheels)

Modern rear disc brake rear wheels (135mm overlocknut or 142mm Thru-axle) still have a lot of dish, and still benefit from offset spoke hole rims, but as you say, not as much as rim brake wheels did. Fortunately, offset spoke holes are more common for disc brakes wheels than they were for rim brake wheels - with disc brakes manufacturers can make a single offset spoke hole rim that can be used for front or rear, whereas with rim brakes manufacturers had to make separate non-offset rims for front and offset rims for the rear.

[Mark McM]

I agree with most of what most of OldPotatoe says. The difference in weight (430 grams vs. 485 grams) is quite a bit, in terms of rim robustness. All else equal, a wider and deeper rim will also be be more robust. Also as OldPotatoe says, offset spoke holes on dished wheels do increase reliability, all else being equal. However, 28 spokes isn't a lot for a 430 gram, fairly shallow aluminum rim. Despite not having offset spoke holes, the deeper, heavier rims might make for slightly tougher wheels. A rider who rides "light" may be able to get away with the lighter rims, but a rider who is a "wheel wrecker" would probably want the heavier rims.

[robertbb]

Originally Posted by coffeecherrypie

Just a data point for you, on my gravel bike I run 38 mm tires on A23s which have an internal rim width of 18mm and it’s fine

Do you find that they bulb too much? I know it'll work but I guess tyres perform best when the shape is correct for the tread. I don't care about aero.

[coffeecherrypie]

Originally Posted by robertbb

Do you find that they bulb too much? I know it'll work but I guess tyres perform best when the shape is correct for the tread. I don't care about aero.

I can't say that it looks (or feels) particularly bulby to me, to have 38s on 18mm internal width.

[macaroon]

Originally Posted by robertbb

It'd be a no-brainer if I could get the asymmetric rim with the RR481 dimensions. I'm just concerned that a 20mm inner width (nor a 22mm outer width) wide enough for where bikes and tyres are going...

I used to use Mavic XM719 rims (19mm internal width) with 2.3 and 2.5 inch tyres, for downhill mountain biking. I don't understand the anxieties road/gravel riders seem to have when it comes to a couple of mm between rim widths.
FYI, I use a set of wheels with the RR421 rims and they've been bulletproof.

[Peter P.]

According to my Sutherland's Manual,

"Wired-on tires with an ISO section width of between 1.45 and 2 times the rim width (measured in millimeters between the inside of the flanges) should fit well. Hooked edge rims hold tires with a section width of up to 2.25 times the rim width. In practice, and in the quest for lighter weight, many companies have mounted fat (MTB) tires on narrow rims. ISO has not updated it's standardss during this time, but real-experience has shown that for MTBs, 3.0 times rim width works. 3.25 or 3.5 times are possible, but most companies back off from such extremes, and we would not recommend them."

[marciero]

i22 for the win. Asymmetrical is nice but the reality is that non asy work just as well.

[mstateglfr]

Originally Posted by robertbb

It'd be a no-brainer if I could get the asymmetric rim with the RR481 dimensions. I'm just concerned that a 20mm inner width (nor a 22mm outer width) wide enough for where bikes and tyres are going...

If you are going to use 32mm - 42m tires, then it really doesn't matter where the industry is going with tire width. They may go narrower or may go comically wider, but that doesn't need to be a factor for you in this situation.

For a 22mm to 42mm tire range, I wouldn't hesitate to select rims that are 20mm wide internally and 24mm wide externally.

- They are lighter, so since neither rim gives aero gains, you may as well higlve lighter wheels.
- They are plenty wide to easily and competently handle your tire width range.
- They are offset and allow for a better build.

For years I used H+Son Hydra rims on my gravel bike- it's 20mm internal and 25mm external, and 23mm deep. So pretty similar measurements as the RR421. I used 42mm WTB tires and 43mm Panaracer tires and never thought twice about tire width compared to rim width when I was actually riding.

[Mark McM]

Originally Posted by Peter P.

Asymmetric rims for the win!

I have built many with O/C rear rims; they last longer and flex less laterally.

That's incorrect - using off offset spoke holes on dished wheels decreases wheel lateral stiffness. The reason is because contribution of spoke bracing angle to wheel lateral stiffness increases with the square of the sine of the bracing angle. The reduction in lateral stiffness due to the decrease in bracing angle of the left spokes is greater than the increase in lateral stiffness due to the increase in bracing angle of the right spokes. There are very good reasons to use offset spoke holes on highly dished wheels (including better durability), but increased lateral stiffness is not among their advantages.

Originally Posted by Peter P.

Aero spokes reduce that lateral stiffness and any gains are marginal.

That's also incorrect. It is true that flattened spokes have less stiffness in bending - but spokes aren't loading in bending, they are only loaded in tension. Only the longitudinal stiffness of the spoke matters. For spokes of the same length and material, longitudinal stiffness is affected only the cross-sectional area, not the cross-sectional shape. A 1.5mm diameter round spoke has the same cross-sectional area as a 1mm x 2.2mm aero spoke, so wheels built with either will have the same stiffness.