GT Zum S1 review

Solid urban mountain bike

Our rating 
3.5 out of 5 star rating 3.5
GBP £499.00 RRP

Our review

Not the quickest, but a good solid ride for urban thrashing
Skip to view product specifications

GT’s renowned Zaskar takes ably to the streets in this urban incarnation, but it would be nippier with lighter wheels and tyres.


The GT Zaskar has been around for over 20 years, and the longevity of the frame means there are still plenty of Nineties examples around, many of which have been pressed into service as road machines.

Today’s Zaskar mountain bikes are slinky carbon beasts, but the aluminium frame lives on: in the beautiful limited edition 20th anniversary re-issue, for starters, but more appositely in the ZUM (Zaskar Urban Machine) range, which takes the Zaskar frame to the streets full time.

Ride & handling: lively & agile for quick commutes

The ZUM’s fairly tight mountain bike-derived geometry gives the ride a lively feel.

The bike feels quite agile in traffic and it’s more fun on a short blast than a longer commute. For the long haul, more stretched-out 700c urban steeds tend to perform better.

Frame/Chassis: classic mountain bike layout

That there are so many aluminium Zaskars still around indicates the long-term quality of GT’s design. The ZUM has the trademark triple triangle frame shape in butted aluminium.

The shortish back end of the ZUM has its drawbacks – we couldn’t fit a child seat because there wasn’t enough heel clearance.

Equipment: decent urban selection

The 2007 range was a hotch potch of suspension forks and slick tyres, but the latest models are firmly planted on tarmac.

The ZUM S1 sticks with 26-inch mountain bike wheels but gets a carbon road fork, Truvativ Elita compact double chainset and Deore 9-speed running gear with a Shimano Deore XT rear mech.

Tektro Auriga hydraulic discs take care of the stopping, and there’s a decent mix of GT and branded finishing kit, including alloy platform pedals and an SDG Bel-Air saddle.

Wheels: some scope to trim fat

If there’s one criticism of urban bikes at this price point that we make more than any other, it’s that the wheels let the bike down. They often bear the brunt of the economising, and we feel that’s the case here.

The WTB Speed Disc rims that are fitted are certainly decent quality hoops, but they’re probably overkill for the streets, and they’re laced to pretty bulky and cheapish hubs.

Add to that the fact that although the Maxxis 1.5-inch slicks are good for ride comfort, and fantastic for dry cornering, they’re not light either.

The wheel package definitely takes the edge off the performance of the bike as a whole, and the all-in bike weight is average rather than good.

On the plus side, however, they fit with what is a very, very solid machine.

Verdict: solid & dependable

The overall spec for this is good for the money and all the drivetrain components are dependable, while the brakes are truly excellent and set the bike up to take some real abuse from the potholes, kerbs and D-locks you’re likely to encounter.


This is one to look at if you need solidity and dependability over performance.

Product Specifications


Name Zum S1
Brand GT

Brakes Auriga Comp
Cranks Elita compact chainset with GXP bottom bracket
Fork Lightweight Carbon Fibre Fork
Frame Material GT Butted Aluminium
Front Derailleur Deore
Rear Derailleur Deore
Rims Speed Disc
Saddle Bel Air RL Saddle
Shifters Deore
Available Colours Black
Available Sizes 18 Inches 20 Inches
Front Tyre Size 26x1.5
Rear Tyre Size 26x1.5
Wheelset SpeedDisc All Mtn
Year 2008