Bicycles/Maintenance and Repair/Shifters/SRAM Gripshift 3.0 'comp' Cable Replacement
The SRAM Gripshift 3.0 'comp' shifter is in wide use for straight handlebar bicycles, and other bikes that are known generally as mountain bikes (MTB). It is used in three-speed versions for front derailleur (FD) shifting, and exists in seven, eight and nine-speed units for rear derailleur (RD) shifting. At the time of writing the shifters are available as new spare parts with the cable pre-wired, but the cable itself can be replaced as often as necessary by the user. This page explains how to install a new cable for the shifter.
The rear shifter is supplied for two cable-pull families, the straight 1:1 family version and the Shimano-compatible 2:1 version. The Shimano-compatible version exists as three models, marked on the item as 'MRX' (7/8-speed), 'MRX Pro' (7/8/9-speed), or as 'Centera' (8/9-speed). Items without these 'MRX' or 'Centera' markings in their descriptions belong to the straight, native SRAM 1:1 family. This description applies to both families. The length of cable pulled for these two differ; a seven-speed SRAM 1:1 GripShift pulls 4.5mm of cable (for RD shift ratio of 1.1), while the Shimano-compatible MRX 7-speed version pulls just 2.9mm of cable (for RD shift ratio of 1.7). There are also low-normal (rapid-rise) versions for the Shimano-compatible rear GripShifts, where the labeling of the shifter's index numbers is reversed, compared to the conventional high-normal style. The exact cable pull of Shimano's front shifters is unclear, but since SRAM advertise their front shifters as being suitable for Shimano front shifting also, they probably belong to the 1:1 shift family, with a shift ratio of about 1.1 (one point one).
There is little maintenance associated with such twist shifters and not much goes wrong with them, though it is true to say that they are not true indexed shifters. That is to say, it is fairly free, but not entirely free of the cleanness of shifting on the part of the rider. They use click-stops inside the shifter, but it is still possible to twist the grip too far, so that they lack a true all-or-nothing response. They are capable of a clean shift provided that the rider concentrates a little on doing so.
The SRAM GripShift 3.0 'comp' shifter is so-called because it is supplied complete with its shift cable already connected, and it is perhaps just as well, for many have difficulty in threading a new cable and resort to buying new units instead. Whereas some shifters take a new cable as easily as a brake lever, with a simple alignment of barrel slots, this shifter is undoubtedly more awkward, and many have remarked that they have difficulty in feeding a cable through the aperture in the outer grip, using the manufacturer's procedure.
This page explains how to fit a new cable by opening the unit, as this method always gives good results.
The Preferred Re-cabling Method
Individual bikes differ in their handlebar equipment so whereas some can leave the shifter on the bar, others may find it best to remove it entirely from the handlebar for cable threading. In this event, once the cable is free of the derailleur and the handlebar grip removed, the entire shifter can be removed by unscrewing the small hex-screw that locks it onto the handlebar. Refer to the two photographs of a typical unit on the right as you read the preferred method.
Open the shifter
- Make sure that the old cable is disconnected from the derailleur's clamp. Note exactly how the cable was attached to the clamp, since it must be replaced in that way, paying attention to its exact direction of approach and the angle at which it is clamped.
- Pull the cable through the housings without entirely removing it from the shifter. This point is useful in allowing the user to learn the cable routing within the shifter when it is opened.
- Remove the bike's handlebar grip, partially or entirely, and any washer, in preparation for sliding the grip section along the handlebar.
- If the shifter is for a REAR DERAILLEUR then first set it to the index number that corresponds to the slackest cable. This is often the highest index but not always. If for a FRONT DERAILLEUR then the slackest is often the smallest index number. The matter is not critical since the parts are to be removed, but this makes it easier to see the routing when inside.
- The grip section is not screwed to the shifter's body but is a firm press-on-fit. Carefully ease off the shifter's rubber grip section outwards along the handlebar to access the internal parts. It can be removed altogether by sliding it all the way, and by depressing the plastic prongs that hold it captive. The cable will be seen to run through a hole in cable ring. It also acts as a cable stop for the cable end. Refer to figures 2 and 3.
- Party withdraw the cable ring, (it also will slide along the shaft), to reveal the cable channel that runs into the barrel adjuster. By this point the intended cable route should be obvious. Only when the old cable's routing is clearly understood, should the the old cable be removed.
Feed the New Cable
It is important not to cut the welded end of the cable until the cable runs are complete and the dérailleur and shifter have been properly tested. Also, make sure that there is enough spare housing at the front handlebars to allow the handlebars to turn fully to each side and in addition, to allow about four more inches of length for any future rework.
Be sure to use only a cable that is sold and marked clearly as intended for gear shifting.
- The cable need not be fed though the outer grip but instead it should be fed through the hole in the cable stop of the cable wheel. See figure 2.
- First remove the adjustable part of the barrel adjuster by unscrewing it completely; this makes the cable easier to feed. Then bend the last centimeter or so of the cable in a gentle curve to help it negotiate the turn, and feed the end down the cable channel that leads into the barrel adjuster. When doing so arrange the direction of the pre-bent end so that it best feeds through the barrel transition. When the cable is through the barrel then pull up the slack, and remember to thread the adjustable part of the barrel adjuster onto the cable.
- Replace the cable wheel so that the top-V of the spring is adjacent to the slackest index number, and draw up any slack so that the cable end is in the cable stop and the cable runs in the channel. See figure 3.
- Replace the outer grip with its pointer at the slackest index number, being careful to maintain the position of the cable wheel as it is done, and make sure that the cable stays in its channel as the grip is closed.
- Test the shifter for smooth operation in both directions before feeding the cable through the housings for reconnection to the dérailleur. Refer to Set the Cable Tension for notes on tensioning the cable and adjusting the derailleur.
Note that when the housings are in place, the ferrule that terminates the shift housing must not bind in the end of the barrel-adjuster when it is turned to make adjustments; it is intended to be a loose fit, so choose any new ferrules with this in mind. In the event that new housings are to be run at the same time the page Cables and Housings might be of some help.
- Whereas it would seem possible to use the old cable to pull through a new cable, attaching the two cables well enough to do so has proved difficult. Perhaps somebody will devise such a method in the future.
- Some fine day, a manufacturer will design such a shifter that is programmable. That is, one that allows the cable-pull for any single shift to be chosen with a dial. In this way, the shifter could be used to match any cog-set to any derailleur provided that the number of gears was the same. Alas, I do not know of such a thing.