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The Trek Domane SLR generation 4 takes Trek’s Roubaix-bashing endurance platform and lightens the load for 2023 – this frameset saves 300g over its outgoing sibling.
The IsoSpeed vibration system is still in attendance, but Trek has seen for fit to remove it from the front, reverting to rear IsoSpeed only, just like the original Domane bikes. The resulting bike has an incredibly plush ride, with the IsoSpeed making a tangible contribution.
Yet with clearance for up to 38mm tyres, and here built with 32m tyres, there’s a case to say the bike already has road-damping enough.
It’s been a while, and if I’m honest with myself, I knew this was coming. It’s every bike journalist’s biggest nightmare: trying to explain how Trek’s IsoSpeed damping works. So here goes:
Get a cheap biro. Hold it horizontally, one end in your hand. Now bend the other end and see it arch its back in the middle. Now imagine you are sitting on the biro and it has wheels.
Clik here to view.
This is IsoSpeed, sort of, in that the seatpost is fixed to one end of the biro, and the biro is really a carbon strut housed inside the top tube, bolted at one end of the top tube and allowed to pivot (and so bend) at its middle.
It’s like an internal leaf spring, and it is different here than in the previous Domane as it is no longer adjustable in its bendiness and uses the top tube area to flex, not the seat tube.
This, Trek says, makes IsoSpeed consistent across sizes, as before smaller size frames that had shorter seat tubes would flex less. No fun for lighter riders. But this bike is much more than its damping.
Read all about it
The headlines for the Domane gen 4: rear IsoSpeed is retained while front IsoSpeed is gone; frame loses 300g and retains 38mm tyre clearance and mudguard mounts; the maximum chainring sizes are 52t for a 2x and 50t for a 1x (to allow for said tyre clearance); cables are now better integrated; the whole thing has been given the truncated aero tube treatment.
Clik here to view.
Less obvious is that bars and stem are a traditional – and so adjustible and easily packable – setup, and there is a little hatch under the bottle cage that opens a storage compartment in the down tube for spares, which sit in the supplied neoprene sleeve. It’s neat and clean, and it’s also smart as it places heavy things lower in the frame for greater stability.
But who cares about where you’re putting your inner tubes? What about IsoSpeed? Does it work?
Yes, undoubtedly, to the point where I hope I will be forgiven for deliberately slamming the Domane over potholes to see just how well it works. You can really feel it. But do you need it?
Trek says it ditched the front IsoSpeed from the gen 3 as road tyres can be so wide now that they compensate for the lost damping. I’d agree; these 32mm-wide Bontragers (which come set up tubeless, bravo Trek) make the front of the bike feel ever so plush when run at around my chosen 50psi. But the problem – if you can call it such – is that this also extends to the rear to the point where IsoSpeed starts feeling like overkill.
Clik here to view.
It works for big hits, but on most UK surfaces I ride, which are crappy but not Roubaix-crappy, it’s high-frequency buzz that is the problem – a problem that wide, low pressure tyres solve. Given this, I’m led to question the necessity of IsoSpeed unless you live up a berg in Belgium.
For the places I ride I just feel it adds little ride quality but dramatically increases weight and complicates what is otherwise a simple frame.
Quite how much more weight Trek doesn’t say, but it does claim an SLR frameset weighs 1,700g. Contrast this with a more ‘traditional’ endurance bike such as a Canyon Endurace CF, which weighs around 1,300g, and you get a clue. But this is more than a bike with a novel system.
Clever tweaks
Let’s not get too hung up on IsoSpeed. As a paid-up race bike, the Domane delivers in spades. Despite the wide tyres, the bike picks up fairly well, but then to its immense credit carries speed wonderfully, testament to the aero tube shapes and the bike’s satisfying glide. But the Domane really shows its genius in its geometry.
The BB is incredibly low, with an 80mm drop (most bikes are barely 70mm), and this affords a terrific feeling of being planted ‘in’ the bike, by helping to offset the fact that wider tyres are taller, so make the bike’s centre of gravity that much higher. This small but clever tweak helps to keep centre of gravity low, and that in turn adds to the Domane’s cornering ability.
Clik here to view.
Then there’s the long 61mm trail, which didn’t make handling nearly as slow as I expected, but rather only added to the Domane’s assuredness on descents. The more upright riding position was a bonus too – tall, here, is comfy.
In fact whichever way you cut it, the Domane is a joy to ride. Which brings me back to IsoSpeed, because the only thing holding this bike back is weight. It’s a near-ten grand bike that is arguably carrying an extra kilo, and there are times – on climbs or accelerating – when I could really feel it.
It’s not a dealbreaker, but I’m left wondering just how much I’d love a Domane that had wide tyres and a light-as-Trek-could-get-it frame.
Image may be NSFW.
Clik here to view.
Trek Domane SLR spec
| Brand | Trek |
| Price | £9,500 |
| Frame | Domane SLR 7 eTap |
| Fork | Domane SLR carbon |
| Weight | 8.2kg (56cm) |
| Sizes available | 47, 50, 52, 54, 56, 58, 60, 62 |
| Brakes | SRAM CenterLine X 160mm disc |
| Rear derailleur | SRAM Force eTap AXS 12-speed |
| Front derailleur | SRAM Force eTap AXS |
| Crankset | SRAM Force AXS Power Meter |
| Bottom bracket | SRAM DUB |
| Cassette | SRAM Force XG-1270, 12-33t |
| Chain | SRAM Force |
| Wheels | Bontrager Aeolus Pro 37 carbon tubeless |
| Tyres | Bontrager Rs Hard-Case Lite Tubeless Ready 32mm |
| Bars | Bontrager Pro IsoCore VR-SF |
| Stem | Bontrager RCS Pro |
| Seatpost | Domane carbon |
| Saddle | Bontrager P3 Elite |
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Pick of the kit
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Udog Cima shoes, €250 (£220), udog.cc
Udog is new to the foot game, but it’s doing a few things right. First, this is its most expensive shoe and it’s still just over £200. Yes, that’s loads of money, but in the context of high-end bike shoes is quite reasonable (and the very similar Tensione shoe is £130).
Second, the upper is made to wrap around and under the foot, those Vs on the sides spreading tension under the arches as well as over the top of the foot. The sensation is almost sock-like, and given a pair of 44s weighs just over 500g, the overall feeling is one of airy, light weight. Just try them first, as sizes come up big.
Trek Madone SLR alternatives
Trek Madone RSL
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The RSL (£4,500, available as frameset only) sheds a claimed 100g in weight by losing the cubby hole and mudguard bosses, but gains racier geometry with a 548mm stack and 51mm trail (size 56cm).
Trek Madone SL
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The Domane SL is the same shape and geometry but is made from lower-grade carbon. Thus weight is around 800g more, but prices are lower – this near-identical version to the SLR tested costs £7,250.