by Alan Dixon | 2004-06-26 03:00:00-06
The GoLite Jam received the highest overall score and was the second highest rated pack for load carrying capacity, at 30 pounds (13.6 kg), in Backpacking Light’s 2004 Frameless Pack Review. The key to the Jam’s load carrying performance is not any one feature but a combination of many things done well. It has wide side fins on the hipbelt that contour around the hips to prevent slippage. There are five compression straps to compact the pack contents into the virtual frame. The Jam has an internal foam backpad which supplements the rigidity of a ground pad that is rolled in the pack and a narrower/taller pack profile that forms the pack contents into a stable, vertical cylinder conducive to forming a virtual frame.
The GoLite Jam had one of the best balances of load carrying capacity, pack weight (21 oz size L), and features of the packs we tested. With three external pockets, including a large fabric rear pocket, the GoLite Jam provides quick access to your most needed items during the day. With some care (e.g. if you’re not planning on dragging it across granite) the Jam is one of the lightest packs suitable for aggressive off-trail-travel, winter ski trips and mountaineering or climbing. Climbers and skiers will appreciate the Jam’s taller, narrower pack profile for good balance and arm swing clearance. The pack’s climbing features include: the ability to carry two tools (including shaft holders), a climbing rope, and/or skis and poles. The Jam’s major weaknesses are under-padded shoulder straps that dug into our shoulders at higher pack weights, and while the Jam’s Dyneema® Gridstop fabric is plenty durable for trail use, a lack of fabric reinforcements in high wear areas may present a problem for abusive off-trail-travel and climbing.
Numerical ratings follow a scale of 1 to 5 (1 = poor, 5 = excellent).
The GoLite Jam uses a 1.5-inch webbing hipbelt in conjunction with wide, triangular side fins that contour well around the hips and waist to prevent belt slippage. The main pack bag has four side compression straps and one top compression strap. These combined with a ground pad rolled as a cylinder inside the packbag create a relatively rigid virtual frame to comfortably transfer pack loads of up to 30 pounds to the hipbelt. Without the rolled up pad, the Jam’s load carrying capacity is lower but the pack’s internal backpad and compression straps still make a virtual frame capable of carrying up to 15, possibly 20 pounds. The taller and narrower profile of the Jam helps to form a virtual frame. This shape forms the pack contents into a stable vertical cylinder more conducive to forming a virtual frame than wider packs which do not control loads well. Finally, at 38 liters un-extended capacity, the GoLite Jam is a good volume for most lightweight backpacking loads (neither too large nor too small). That is, once you put an ‘average’ set of lightweight backpacking gear in the pack, the main pack bag will do much of the load control, leaving the compression system to do the final touches on the virtual frame. Our major gripe with the Jam’s suspension is that the padding in the shoulder straps is poorly resilient to load compression. With heavy loads, the straps dug into our shoulders on 16 to 20 plus mile trail days. We’d like to see more substantial shoulder straps similar to the thermo-molded Brock™ foam ones used in GoLite’s new Unlimited Series packs.
While the Jam is a bit heavier than the lightest packs in its capacity range, it is also more versatile. The Jam’s design and features make it suitable for all of the following activities: short overnights, mid to long distance backpacking trips, winter ski trips, and climbing. There is enough exterior pocket storage that one should not have to delve into the main pack bag much during the day. The pack loads easily and, using the compression straps, it is not difficult to create a decent virtual frame with varying load volumes. Some of the Jam’s main features are:
With five compression straps, the Jam has one of the better compression systems among lightweight frameless packs. This compression system was a contributor to the pack’s high ratings for load carrying capacity. In addition, the compression system kept low volume loads under control. The Jam has four compression straps on the sides of the main body, two about mid pack just above the side pockets, two at the top of the side panels, and finally one compression strap on the top of the pack that doubles as the closure for the roll top/extension collar.
For even better load control we’d like to see another pair of compression straps in the lower portion of the pack. To compensate for the lack of compression straps in the lower portion of the pack we put our sleeping bag, extra food and extra clothing into the lower portion of the pack (or anything you don’t need immediate access to that combined has enough volume to reasonably fill the lower section) and locked it down with the mid-pack compression straps. This better maintained the pack’s virtual frame and provided a solid structure to transfer load to the hipbelt fins.
In the field, with a well-packed and compressed main bag, the Jam did well carrying loads of up to 30 pounds. The data collected on the Jam in our “Frameless Backpacks: Engineering Analysis of the Load Carrying Performance of Selected Lightweight Packs” article supports this performance. To achieve this level of performance we used a ¾ length Ridge Rest pad rolled up as cylinder inside the pack. We then placed the rest of the pack contents inside this cylinder and correctly tightened all five compressions straps. We liked the taller and thinner profile of the Jam. This profile is more resilient to collapsing and creates a better virtual frame. The narrow profile also gave the pack good balance for off-trail scrambling and climbing and free arm swing for both trekking poles and climbing tools.
At 25 to 30 pounds the pack’s virtual frame begins to collapse and the torso length shortens. When this happens, more weight transfers to the pack’s shoulder straps. As noted earlier, the air mesh shoulder straps are under-padded, have little structure, and do not distribute loads comfortably. At 30 plus pounds they dug into our shoulders on 16 to 20 plus mile days when we were carrying substantial amounts of water on a long, dry stretch of trail. One shoulder strap edge even caused a small abrasion. Stiffer and more padded shoulder straps would distribute weight more evenly and smoother strap edges would prevent abrasions. For those who like to carry a bit of weight on their shoulders, more comfortable shoulder straps would increase the comfortable load carrying capacity of the Jam.
The Jam’s 4.13 ounce per square yard, 215 denier, Dyneema® Gridstop nylon suffered no serious damage (other than some scuffs) from the trail backpacking, off-trail travel and scrambling we subjected it to. The Jam is designed with features that clearly appeal to climbers and rigorous off-trail travelers (e.g. dual tool holders). In our estimation, the Dyneema® Gridstop will not handle a back slide down a scree slope, or heavy duty bushwhacks. (In the past, we ripped a large hole in the bottom of another pack that used a similar weight of Spectra Gridstop fabric.) Climbers and serious cross-country travelers will need to exercise care to not overly abuse the Jam in their more aggressive pursuits.
The Jam may be the most feature rich $89 pack on the market. It can carry up to 30 pounds (13.6 kg), weighs only 21 ounces (590 g), has good volume compression, plenty of pockets and external storage options, and climbing amenities. If abrasion is not a major concern, it is one of the lightest packs suitable for aggressive off-trail-travel, winter ski trips, and light and fast mountaineering or climbing.
The Jam’s shoulder straps are under padded, have little structure and do not distribute load well to the shoulders. We’d like to see more padded and firmer shoulder straps similar to the thermo-molded Brock™ foam straps used in GoLite’s new Unlimited Series packs or possibly the shoulder straps used on the Breeze or Gust packs. Since the Jam has all the features to make a great off-trail and climbing pack, it’s a pity that it doesn’t have fabric reinforcements. We’d like to see some x-Pac™ or Cordura fabric to reinforce the bottom of the pack and the rear pocket. Also, a pair of lower compression straps would improve the pack’s virtual frame and content control with low volume loads. Finally, we’re not fans of internal hydration pockets. They are okay when you first load up the pack in the morning. But re-filling internal hydration bladders during the hiking day is a pain as you have to unload and reload most of the main pack bag to put the re-filled bladder back in. We would rather have seen the hydration pocket located on the outside of the pack, or a pack design that does not include such a specifically designed pocket.
"GoLite Jam Backpack REVIEW," by Alan Dixon. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/golite_jam_review.html, 2004-06-26 03:00:00-06.