Modern e-MTBs are massive, fast and unfortunately also quite heavy. Thanks to integrated batteries and an increasing focus on downhill performance, the weight of the add-on parts that have to be able to cope with these requirements is also increasing. Until now, however, even the best e-enduro bikes were still fitted with conventional mountain bike forks, which sometimes looked a little out of place on stovepipe-sized head and down tubes. But Fox and Rockshox are creating alternatives.
Simply install double bridge forks? No, because the double crown would restrict trail riders too much due to the steering stop and also when servicing. A stiffer chassis and wider stanchions with a diameter of 38 millimetres with single fork crowns was the answer for both Fox and Rockshox. A positive side effect: the new forks also blend in well visually with many already wide E-MTB frames.
Rockshox Zeb vs Fox 38: The facts
But be careful. Is more weight being deliberately added to the bike in favour of looks? Or do the thicker forks also offer more capabilities? We carried out an extensive laboratory test to find out what the allegedly increased stiffness of the two forks actually means. And indeed: Both forks can add a good bit of stiffness compared to their conventional 35/36 millimetre brothers. Fox's 38 achieves 29.8 Newton metres of torsional stiffness, over seven and a half Newton metres more than its little brother the 36. Rockshox's Zeb is even stiffer (34.4 Nm) - almost 4 Newton metres more than the already excellent Lyrik. We tested the 38 forks in a 29-inch version with 170 millimetres of travel, while the data for the Lyrik still comes from the 27.5-inch version with only 160 millimetres of travel. In a direct comparison, the difference is therefore likely to be somewhat greater.
And in a comparison of the two big hulks? As is often the case, the Rockshox fork is ahead in terms of torsional stiffness. In terms of braking stiffness, the rivals have almost nothing in common (Fox: 269.4 Nm, Rockshox 268.2 Nm), but in both cases they put significantly more on the test bench than their little brothers, the Fox 36 (223.6 Nm) and the Rockshox Lyrik (224.9 Nm). The weight, on the other hand, is astonishing: despite slightly better stiffness values, the Rockshox ZEB is lighter at 2308 grams than the weighty Fox 38 (2461 grams). The comparison with the Lyrik and 36, both of which weigh a good two kilograms, makes it clear that the stiffness comes at the price of more material, although all the data for the Fox 36 does not come from the slightly stronger and therefore heavier e-bike optimised version.
What about the practice?
But how do the two thick forks perform in practice? Is stiffer really better? Or is there such a thing as "too stiff"? And how do the two rivals perform in terms of sensitivity, damping and adjustability? Can Rockshox also score points here? Or does the Fox 38 win the duel due to its better soft skills? You can read the detailed test in EMTB 04/20 - available from 18 August in specialist shops and in the Digital edition.
*Unlike Rockshox, Fox reinforces the forks optimised for e-bikes with slightly more material, at least for the 34 and 36. The chassis of the Fox 38 and the Fox 38 for e-bikes is again identical.
Adrian Kaether
Editor
