Bars that have been bent in a crash need to be replaced immediately – they‘ll be weakened and will let you down when you least expect it. You may also be upgrading your bars for lighter or stronger ones – or for a new shape like a higher rise for more downhill control or a flatter bar to keep your weight over the front wheel when climbing.
Carbon bars are popular because they‘re stiff, light and strong. They need to be looked after though – a scratch on the surface will weaken them significantly. Take care when fitting and adjusting.
Next, remove the grips. Slide something underneath so that you can lift the grip up a little. It‘s tempting to use screwdrivers because they‘re the right size and handy, but it‘s all too easy to scratch the bars with them. Chopsticks, being made of wood, are much better. Use hairspray, spray degreaser or warm soapy water to lubricate the undergrips. Twist and pull to get the grip off.
Unbolt and remove the shifter and brake lever. Take care not to scratch the bars at all because cracks can grow from tiny scratches, especially on carbon bars. If the levers and shifters don‘t slide off easily, remove the fixing bolts altogether and open up the clamp very slightly with a screwdriver – just enough to slide off the levers. Don‘t bend the clamps, though!
You may find that cables or hydraulic hoses are too short to slide the levers off without kinking them. Don‘t wrestle with them: undo the bolts that hold the handlebars onto the stem and slide the handlebars along in the stem so the levers don‘t have to travel as far to slip off the end. Remove the handlebars.
Clean the face of the stem that the bars fit into – if dirt has worked its way in between the two parts, the bars won‘t clamp firmly onto the stem and will creak as you ride. Lubricate the central part of the new bars – grease for aluminium bars, carbon prep for carbon bars.
Ease the clamp open slightly to avoid scratching the bars
Next, clean and grease the bolts that fix the bars onto the stem. The threads in the stem are soft and will strip easily if treated badly – this is expensive neglect because once you‘ve stripped the threads, your only option is to replace the stem. So clean dirt out from the bolt threads and under the bolt head, then grease the threads and bolt head.
Fit the new bars loosely onto the stem, then slide the brake and gear levers onto the bars. If the cables or brake hoses are short, you may need to pass the bars from one side to the other through the stem to get the controls onto the bars without kinking the cables. Next, refit the grips. They need to be a tight fit so that they don‘t suddenly slide off the ends of the bars as you ride (this sounds like it would be a comic moment, but is actually disastrous and painful). You‘ll have to lubricate them to slide them on, but whatever you lubricate them with then needs to stick the grips to the bars. The ideal product is motorbike grip glue, but it‘s often hard to find. Alternatives include isopropyl alcohol, disc brake cleaner and artists‘ fixing spray. Don‘t use spray oil because it never dries properly. Set the bars in the centre of the stem, tighten the stem bolts enough to hold the bars in place, then sit on your bike to work out the most comfortable angle for the bars to sit at. If the bars are swept or curved back, a good starting place is pointing the sweep up and back towards your shoulder blades. Small rotations of the bar can make a big difference, so take a bit of time playing with the angle. Once you have the bar position, rotate brake levers and shifters to a comfortable angle. You need to be able to grab and operate them with as little effort as possible. Experiment with different brake-lever angles. Set the levers so that you don‘t have to lift your fingers too far up to get them over the lever blades.
Once you have everything in place ergonomically, go around and tighten all the fixing bolts. If your stem has a removable front face, be sure to tighten the bolts evenly so that there is an equal gap above and below the bars.
Bars are usually supplied wide, so that you can cut them down to suit your tastes. Check the manufacturer‘s recommendations for carbon bars before you start – if they tell you not to modify the length, follow their instructions.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
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