DT’s XM551 rims are designed with chubby tyres in mind. They’re wide – but not in this context enormously so. They have an external width of 44mm, and an internal width of 40mm. So in the context of regular wheels, very wide indeed. But for chubby tyres? Not so much. We’ve ridden plenty with an internal diameter exceeding 50mm, after all. But we’ve tested rims this wide with regular tyres before, and we’ve come away impressed, although we did find tyre choice slightly limiting; tyres with pronounced shoulders become too square in profile to work properly, although more rounded ones work excellently. But for this review we’ll focus on the XM551’s suitability for chubby tyres.
The rims are, as you’d expect from DT, very well constructed. There are a couple of clever ideas nestled within, too. They’re made with the PHR Pro Head Reinforcement system, which is a cunning way of getting rid of eyelets – the system replaces it with a special washer and nipple system. This lets the nipple pivot within the washer, and apparently makes building and truing easier, as well as reducing spoke breakage.
None of this was something that we needed to worry about, however, as our rims came ready attached, via 32 straight gauge spokes, to a pair of DT 240s hubs. Plenty has been written about these before – essentially they are DT Swiss’ top-flight hubs, which come complete with its Ratchet System – two star ratchets, which are held together with a pair of steel springs. This makes for a very simple, reliable freewheel mechanism, which is handily serviceable without tools.
In use, the wheels performed faultlessly. I shod them tubeless with a Vee Trax Fatty 2.8 on the rear and a Schwalbe Nobby Nic 3.0 on the front. I was curious to see what difference installing a 2.8in or 3.0 tyre on a 40mm internal width rim would make compared to a 50mm or wider one. As expected, the tyre sidewall was slightly more angled inwards and the tyre was fractionally narrower.
But performance-wise I detected very little difference, even when running at sub 15psi pressures. Charging through rocky sections of trail, there was minimal deflection, helped by the 32 straight gauge spokes – and in any case, the tyre carcass is always going to be the more malleable in this relationship. The tyres didn’t seem to squirm any more than they do on the wider rims.
The hubs performed flawlessly, as expected. The freewheel has a lovely, almost tactile ‘burr’ to it, and the bearings held up well to the worst that Yorkshire could throw at them.
Weight-wise these wheels came in at a smidge over 1980g; weight could be further removed by switching to butted spokes, and running the 28h spoke rims and hubs instead of these 32h versions. But I think I’m happier trading a little weight for increased strength in any case, even if some of that weight is at the rim (where rotational inertia means it counts for more).
Overall: If you’re toying with dipping a toe into chubby territory, these rims are well worth a look: they’re relatively light, and they’re perfectly wide enough, but you can still run many more ordinary tyres with aplomb if you so choose. And our examples are built onto DT’s – admittedly pricey – bombproof, solid and serviceable 240s hubs.
|Product:||XM551 Rims and 240s Hubs|
|Price:||Rims: £89.99 each including nipples and washers. Hubs: £149.99 Front and £299.99 Rear|
|Tested:||by Barney for Four weeks|