Shop Talk | One Day Suspension Hop-Up

How To

OEM suspensions generally work fairly well, however, they are designed (and priced) to perform within certain parameters, and once you exceed those parameters, as we all do from time to time, handling and comfort can get a little wonky. They are also subject to normal wear and tear, so in time, springs sag, shocks lose their damping and before too long your formerly fine-handling cruiser has become the world’s fastest mattress. Fortunately, most suspension issues, whether caused by design or deterioration, can be resolved without bottoming out your wallet or your weekend.

Choosing the right components

Selecting the right springs and shocks is the first order of business, and the choices can be daunting. Fortunately, every suspension manufacturer has a catalogue that provides specific recommendations along with the available options and prices.

Prices vary greatly, and for many of us that’s a prime consideration. For example, shocks for the Triumph Bonneville range from Hagon’s no-frills Classics at $199, to the high-tech Öhlins Type 36PL at $899.95. What’s the difference? The Hagons are a basic spring preload-adjustable shock; they work very well, are solidly made, and will noticeably improve the handling of your motorcycle, but they’re not fancy. The Öhlins have all the bells and whistles, including an adjustable ride height provision and adjustable rebound and compression damping, as well as being re-buildable. They also look expensive, which is a consideration to some. That being said, I’ve used the Hagon Classics on everything from the bike in this article to my vintage dirt trackers with excellent results. The bottom line here is that even “affordable” shocks offer a substantial improvement over the OEM versions, so there’s no need to bust the bank.

Cost aside, what criteria should you use? As someone famous once said, “If you want to know what works, look at what the guys on the podium are using.” In this instance, you might want to check out internet forums and see what shocks and springs are most popular for your brand of bike. If everyone riding a Yamaguchi swears by Sag-No-More shocks, it’s a safe bet they’re the hot setup for your Yamaguchi ThunderThigh 1200.

I’d also recommend contacting the manufacturer’s tech line. In fact, some manufacturers won’t ship the shock until you do. They’ll help you select the correct spring rate and shock length and answer any technical questions you might have, greatly short-cutting the selection process.

Installing fork springs

Everyone’s spring kit is slightly different. Some include any new pre-load spacers you may need but some don’t, so read through the installation instructions before opening your toolbox. It’s one thing if new spacers aren’t required and another if you have to run out halfway through the job to buy a hunk of PVC pipe to fabricate them. Likewise, check the fork oil specs; you’ll need at least a quart and possibly more, so make sure you’ve got the right stuff before you disable the bike.

The basic procedure requires draining the fork, removing the old spring(s), installing the new one(s) and refilling the forks with oil. If you’re riding an older bike with fork drain screws you’re way ahead of the game, and you’ll be able to do the job in an hour or two without removing the forks. Most of us won’t be that lucky, and will have to remove the forks to drain them.

Your service manual will detail the fork leg removal process. Typically, you’ll have to remove the front wheel, fender and calipers, as well as the fork legs. I have two hard-learned pieces of advice: First, loosen, but don’t remove all the hardware you can before jacking the bike up. It’s a lot easier to loosen tight fasteners when both wheels are on the ground than it is to wrestle with them while the bike teeters on a jack. Secondly—and more importantly—back off the top clamp’s pinch bolts before attempting to loosen the fork caps, but don’t loosen the lower triple clamp pinch bolts until you’re ready to remove the fork tubes. The top pinch bolts slightly distort the fork tubes; this pinches the threads, which prevents the caps from loosening under normal use. Trying to remove the caps while they’re under tension is difficult and can damage the threads of the caps and forks. Leaving the lower pinch bolts tight will prevent the legs from turning while you break the caps loose, and prevent the tubes from dropping out of the forks before you’re ready.

Once everything’s loose, you can proceed to remove the wheel, caliper(s) and fender. Note the fork leg’s height relative to the top clamp, then loosen one of the fork’s lower pinch bolts—and only one—and slide that leg out of the clamp, leaving the other one in place.

Brace the lower leg against a protective surface before carefully removing the fork cap. Most caps are under spring tension so maintain a slight downward pressure as you unscrew it. Next is the messy part. Remove the preload spacers, followed by the spring, then invert the tube over your drain bucket, and pump it a dozen or so strokes to expel the old oil. That’s it; the disassembly is done.

Reassembly starts with fresh oil. The simple way is to pour in a measured amount and let it go at that, which works just fine, but there’s a better way.

Fork tubes always contain a volume of trapped air between the surface of the oil and the fork cap. The air acts in concert with the spring to provide some support, and because the air becomes “stiffer” as it’s compressed, has an effect on the overall spring rate. When forks are drained—as opposed to being dismantled and wiped perfectly clean—there’s always some amount of oil left behind, so if we add a measured amount and call it good, the two fork legs may, and probably will, hold two slightly different amounts of oil. Since the volume of air in the leg depends on the volume of oil, the leg with the most oil will in effect have a stiffer spring than its partner, which will affect fork action. If we adjust the fork oil level by measuring its height, we ensure that both contain the same volume of oil (and air) as well as providing an accurate reference point for any future adjustment.

The air gap setting will be found on the spring kit’s spec sheet, and in most cases will differ from the OEM setting. To set it, collapse the fork, pour in enough oil to cover the damper, and then pump the forks at least twenty times to expel any trapped air.

Next, measure from the upper edge of the fork tube to the surface of the oil, then add or remove oil accordingly. If you’re cheap and patient you can use a flashlight and tape measure to set the oil height, but that becomes tedious. And while it’s easy to add oil, it’s a headache to remove it, so do yourself a favor and purchase a fork oil-adjusting tool from Motion Pro ($21.95).

With the air gap set, install the fork spring. If it’s a progressively wound spring, the tight coils go up, followed by the spacers. Coat the threads of the fork cap with anti-seize before threading it into the fork tube. You may have to bear down against the spring to thread the cap in, which takes some effort, so it’s sometimes easier to set the tube on the floor, engage the cap, and have a helper slowly rotate the fork tube, till the cap is engaged. Snug it up but don’t fully tighten it just yet.

Lubricate the fork tube with WD-40 or silicone spray, and slide it through the clamps to the proper height. Lightly tighten the lower clamp bolt, and try sliding the axle through the replaced leg into the one you haven’t removed. It should slide smoothly. If it binds, adjust the height of the replaced leg until the axle glides through the legs without binding. This should eliminate most alignment problems and help reduce stiction.

Tighten the lower clamp bolt and service the second fork leg, repeating the alignment process after it’s finished. Reinstall all of the removed parts using Loctite and a torque wrench on the appropriate fasteners, and lightly grease the axle before inserting it through the wheel and securing the lock nut. Torque the lower clamp’s pinch bolts first, followed by the fork caps, and lastly the upper clamp’s pinch bolts.

Installing the rear shocks

Rear shock mounts vary according to manufacturer and type of suspension. Traditional twin shocks normally slide over a stud on the frame and are held in place with a securing bolt or bolted into a mounting bracket, as are the single shocks found on linkage type suspensions. “Soft tail” type suspensions may use eyelets, or shaft mounts. Your service manual will provide the specifics, so what follows are a few generic tips.

Unless you’re changing the length of the shocks, it’ll be easier to replace them one at a time, and shocks are always easier to replace if there’s no load on them, so unless got a big strong friend standing by, jack up the rear of the bike until all weight is off the rear wheel before removing anything.

Unbolt the first shock and remove it from the mounts. It should slide right off, but corrosion can create problems. If that’s the case, a little penetrating oil, along with some elbow grease and creative profanity should do the trick. Clean the mounting stud or bracket to remove any loose paint or corrosion. If the shock eye uses a steel bushing, lightly lubricate the mounting stud or bolt with anti-seize or grease. If the shock eye uses a rubber bushing, use only dielectric silicone grease or silicone spray to lubricate it; petroleum-based grease may cause the bushing to soften and swell. Apply Loctite and torque the mounting bolts before replacing the opposite shock.

If the shock didn’t quite fit as easily as it should have or you’re installing a different length shock, jack the bike up until the rear wheel is just clear of the ground, and remove both shocks. Follow the above procedure, using the jack to adjust the bike’s height until the new shocks slip easily into place. Lastly, check the shock’s spring preload before the road test. Shocks are normally shipped with the preload set to the softest setting. But it never hurts to double-check.

Overall, suspension work isn’t particularly difficult, and even a rank novice should be able to perform the work outlined here in 4 to 6 hours. That being said, you are removing and installing components that are vital to your safety, so as always work carefully, follow the shop manual’s procedures, and double-check all your work before proceeding to the next step.

Resources

Required items
• Common hand tools
• 3⁄8 or 1⁄2 in. drive torque wrench
• Load-appropriate jack or lift
• Drain pan/rags • Graduated cylinder or fork oil tool
• Fork oil

Suspension manufacturers

Hagon Shocks LLC
www.hagonshocksusa.com

Öhlins USA
www.ohlinsusa.com

Progressive Suspension
www.progressivesuspension.com

Race Tech Suspension
www.racetech.com

Works Performance Products
www.worksperformance.com

Suspension tools