Long Term Review : Pete’s YT Jeffsy Core 4.

As the weeks turned into months, how has YT Industries’ excellent do-it-all machine, the Jeffsy Core 4 stood up as a daily driver?

The YT Industries Jeffsy Core 4 proved to be every bit the fantastic ride as well as a cracker in terms of value. Pete weighs in with his long term review.

Photos by Pete Scullion.

Key features:

  • Rockshox Lyrik Ultimate 150mm fork
  • Rockshox Super Deluxe shock
  • SRAM GX AXS T-type 12-speed drive
  • SRAM Code RSC brakes
  • Crankbrothers Synthesis Enduro alloy wheels
  • YT Postman dropper
  • £4,999.00 RRP
  • YT-Industries.com


The Jeffsy is available in S, M, L, XL and XXL sizes.

Reach on the M, seen here, is 455mm with a seat tube of 410mm. Head angle is 65 degrees with a seat tube angle of 77.5 degrees with the flip chip in Low. Chainstays are 437mm on the smaller of the three sizes with the wheelbase on the M of 1214mm.

The last few months with the Jeffsy has been pretty ideal, the 145mm 29er doing everything I’ve asked of it and only coming unstuck when I have asked the faster rubber to cut through some slop or grease that they’re simply not designed to do.

Mechanicals have been all of zero. The rear brake has gone a tiny bit notchy when cold but soon smooths out when there’s a bit of heat in the system. The EXO+ casings have been well used, shrugging off the attentions of some of the toughest of Wester Ross’ water bars and sandstone at speed without a grumble.

There is, in fact, only three things I would change on the Jeffsy. One is minor and requires two bolts, the other would need some change to the carbon mould. Grips… On long rides, the flared ends of the ODI grips start to wear away at the hands which can get a little unpleasant, but you’re talking six hours in the saddle and beyond.

The second is rear dropouts. There is no slot for the rear axle to sit into and therefore allow the axle to just slot through. I had to go back to the classic keep giving it a shove and a spin until the threads found their mark. It certainly wouldn’t put me off buying one but it can be frustrating when you just want your back wheel to be attached to your bike.

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Third is the chainring. It does its job of chain retention as you’d expect but stock, the gears feel a little long with a 32t and SRAM only offer rings on the new T-type cranks down to 30t. Whilst 28 might be a little short, it’s that easy spinning on technical climbs that isn’t quite there with a 32t. I’d certainly go smaller personally.

Once you do have all the wheels attached, the Jeffsy is a great companion to some serious mileage in some serious terrain. A recent jaunt into Torridon’s mighty hills proved this. The Lyrik, once a little firm off the top started to sing the same tune as the excellent Super Deluxe shock and the speed rose once again.

As the ground pitches upward again, the Jeffsy makes the most of your power and the grip is always on tap. The seat tube angle keeps you front and centre to help balance the traction out and the bike is by no means a porker which helps keep the forward momentum going.

Testament to the Jeffsy’s abilities is that the bike remains stock. Grips, chainrings and dropouts are minor complaints and for five grand you’re getting an awful lot of bike that, should you wish to upgrade it, is the ideal platform for it.

High grip requirements might lead you to spec some stickier rubber, but that will be at the expense of rolling, so in all, I think YT have made a decent compromise with the faster rubber. On the rock of Torridon, they never skipped a beat, in the slick of Stirlingshire they could be found wanting.

In general though, the YT Jeffsy Core 4 is ready to take you wherever you want to go, at speed and with a confidence-inspiring feel that just keeps coming. It’s upped my riding game and put in a solid shift in a world of different scenarios.

A strong contender for my own money.

You can check out the YT Industries Jeffsy Core 4 over on their website here.