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DT Swiss GRC 1400 Spline 42 wheelset review

19 Feb 2021
Verdict:

The DT Swiss GRC 1400 Spline 42 wheelset are tough enough for gravel and fast enough for road

Cyclist Rating: 
For 
Innovative • Reactive • High quality build • Aero road performance
Against 
Real-world aero advantage off-road is hard to discern

DT Swiss was one of the first brands to consider the value of aerodynamic efficiency for gravel wheelsets and its GRC 1400 Spline 42 wheels, released in mid-2019, are the result of that development process.

The wheels use a rim shape developed in conjunction with the aerodynamics specialist SwissSide, a brand with which DT Swiss has a close, long-standing working relationship. The wheels are 42mm deep, with a 32mm-wide external and a 24mm-wide internal profile.

Yet despite those oversize dimensions DT Swiss has kept the wheelset’s weight to a respectable 1,634g, thanks in part to features like the GRC’s hookless rim design. Hookless is a simpler shape than hooked or ‘crocheted’ rim walls.

The rim wall extends straight up and relies on precise fitment to retain a tyre, rather than curling over to physically prevent a tyre bead from blowing off a rim. This means the rims can be made lighter and to tighter manufacturing tolerances.

 

The move to produce a wide, deep-section gravel wheel has since been followed by the likes of 3T, Bontrager and Hunt, helping prove the credence in DT Swiss’s school of thought.

As the DT Swiss GRC 1400 wheels near their second birthday, it could be said that competing wheels have now taken the concept further (3T’s latest Discus C45 40 wheels are a whopping 40mm externally and 29mm internally), yet that should not detract from the originality of the GRC’s design.

Buy the DT Swiss GRC 1400 Spline 42 wheels from Freewheel now

Especially so considering how well these wheels continue to acquit themselves across a broad spectrum of riding environments. I have been able to ride these wheels in several guises on both road and gravel bikes over an extended period of time.

The GRC 1400 wheels’ feature set lends itself to both gravel riding and road riding with equal aplomb in a way that plenty of competitors don't match.

 

We need to talk about aero

Somewhat counter-intuitively I have come away thinking that the GRC 1400’s original USP – aerodynamic efficiency on gravel – is not the wheels’ biggest success story.

DT Swiss’s published wind-tunnel testing shows that despite being ‘optimised for 35mm gravel tyres’, the wheels are at the most slippery with 30mm wide slick tyres installed, and that a considerable amount of the aero advantage is lost when 42mm knobbly tyres are swapped in.

That is hardly the fault of the wheel – more likely the tread pattern of the tyres ‘dirtying’ the airflow before it has had a chance to flow cleanly over the rim – but I would contest that lattermost tyre shape is a significantly more common choice for gravel riding than a lower-profile 35mm option.

Therefore users are likely to find the aero advantage of the wheels is undermined slightly when making realistic gravel tyre choices.

What’s more, testing was done at 45kmh, which is a speed most riders very rarely achieve on gravel. At slower, more realistic off-road speeds the wheels’ aerodynamic advantage is likely to be reduced further.

 

When questioned about this, Simon Hugentobler, a project engineer at DT Swiss, said the brand had indeed tested at lower speeds to reproduce more realistic riding conditions and found the wheel was still able to ‘contribute positively to the total aerodynamics of the system consisting of rider and bike’, but again that was with 35mm ‘low-profile’ gravel tyres installed.

Consequently, using wider tyres more suited to the conditions I ride in, I can’t say anecdotally that the wheels felt any faster than less aero-focussed gravel designs. I will concede that the gravel riding I do – amateur speeds, around technical lanes and bridleways – is perhaps not the correct environment to best extract the wheels’ intended aero performance advantages.

Buy the DT Swiss GRC 1400 Spline 42 wheels from Freewheel now

At race pace on hard-packed gravel roads – where those slimmer 35mm tyres are more appropriate – in the US or Australia it could well be a different story and the advantage would be tangible, but for the vast majority of riders and riding conditions in the UK I would say the wheels’ aero benefits would be hard to discern.

That isn’t to say I think the aero shaping is to the wheels’ disadvantage however. Their deeper rim imparts several bonuses not often found in gravel wheelsets.

DT Swiss has effectively made a racy road wheel tough and wide enough for gravel use, meaning several of DT Swiss’s fantastic road wheel attributes have been carried over in the GRC 1400 wheelset.

They have a direct, punchy feel as a result of their light weight and deep rim (and correspondingly shorter spokes and their wider bracing angles) that makes them notably responsive when accelerating up steep off-road ramps or through boggy ground. They make any time on tarmac linking gravel sections more zippy and less wallowy too.

I didn’t find the aero rim section made the wheels noticeably harsher than I would otherwise normally expect either. With gravel-volume tyres wrapped around them, I believe extra give in a gravel wheelset is often not essential.

 

I felt that the aerodynamic efficiency of the GRC 1400 wheels came into its own in the traditional sense when I swapped to 30mm road tyres. Following the brand’s wind-tunnel data results and just like other contemporary aero road wheels, the GRC 1400s imparted a subtle feeling of being able to hold high speeds more easily than a shallower rim.

What’s more, with the wheels’ increased rim width properly supporting the sidewalls of wider tyres (both road and gravel alike) I was afforded the grip and comfort of lower tyre pressures with none of the squirm that can afflict wide tyre/narrow rim combinations (narrow rims pinch wider tyre beads together, creating an unstable ‘lightbulb’ shape that can move and undermine handling).

So while I’m not convinced about the pure drag-reduction advantage of the wheels with regular gravel tyres on at real world speeds, the GRC 1400s are nonetheless an accomplished gravel wheelset with several neat features created by their forward-thinking design. Better still, they serve admirable double duty as fast road wheels too.

Buy the DT Swiss GRC 1400 Spline 42 wheels from Freewheel now

Finer details

The DT Swiss GRC 1400 Spline 42 wheelset performance characteristics are made all the sweeter when some supporting details are recognised. DT Swiss’s 240s hubset is well-proven to be essentially beyond reproach in terms of durability and serviceability.

The rims were consistently painless to set up tubeless, plus DT Swiss ships the wheels with high quality MilkIt valves and sealant syringe (a device that revolutionises sealant insertion).

Considering the DT Swiss GRC 1400 wheels’ general build quality, performance attributes and finishing touches as a whole, ultimately I would say they are an unusually versatile proposition that still perfectly suit a gravel bike’s do-anything remit.

Price: 
£1,864.98