We need to pay attention to...
We need to pay attention to our racing shocks and evaluate them on a periodic basis. Here, a student at Patrick Henry Community College in Martinsville, Virginia, runs a shock on one of the school's dynamometers.
The shocks on your car need attention from time to time in order for them to work at their optimum level. Several times over the past few seasons, teams I have helped experienced shock failures. So it is in our best interest to check our shocks often and have them tested and/or rebuilt on a periodic schedule.
We talked to several of our shock experts on the topic of shock maintenance, and they offered some great advice. The shock companies are very involved with the racers and usually have their technicians in attendance at many major racing events. So they see and hear a lot about the pitfalls that can affect a racing shock's performance.
We developed a set of questions about shocks and presented them to our experts. Here is what they had to say.
1. Are there maintenance differences between twin-tube and monotube shocks?
Not really. "The two main things you worry about are seals and breakdown of the oil," says Jeff Sandt with Pro Shocks.
Nate Thiesse from QA1 Racing Shocks offers, "All of our racer revalveable/rebuildable shocks have a similar year-end maintenance schedule, regardless of twin-tube or monotube designs."
"Maintenance for both types of shocks are very similar. If possible, gas shocks should be checked for pressure on a regular basis," says Mark Bush, Afco's shock guru.
Curtis Henquinet of hlins Shocks says the only difference between each kind of shock is in the gas reservoir.
"Maintenance for both monotube and twin-tube shocks is basically the same. A regular maintenance schedule for freshen ups should be provided from the manufacturer," offers Scott Keyser, who designs and supports Integra shocks.
2. Can shock pressure cause premature wear and/or failure?
"The more pressure you run, naturally, will cause greater stress on seals and other components," says Sandt.
"Gas pressure settings in a monotube shock are very important to the performance of the shock valving and consistency," Keyser says. "If the proper amount of gas pressure is not run, the oil will foam and the shock will begin cavitating. Then the shock will fade easily and also lose its valving characteristics. Run with the manufacturer's recommended settings to eliminate any complications or premature failures."
"The gas pressure will not cause any premature wear or failure unless extreme pressures are used," Henquinet says.
"Radical valving, such as 11, 12, and 13 valves, that some racers utilize today create huge pressures resulting in forces that generate much higher shock temperatures. I usually recommend a much more frequent freshening of those shocks than I would a standard straight four-valve," says Thiesse.
"Excessive, extreme pressures could cause mechanical problems within the shocks in addition to having negative effects on handling. Users should follow the manufacturer's recommendations on pressure," according to Bush.
This cutaway shows the inner...
This cutaway shows the inner workings of a monotube shock. The chamber to the left contains pressurized gas and is separated from the shock oil by a piston. The shock piston holding the valves is shown in the main body of the shock at the end of the shock rod. Twin-tube shocks have a gas bag that compresses when the shaft moves into the shock body and displaces the shock fluid to control cavitation.
3. Are your shocks user rebuildable?
"Yes, Afco shocks are rebuildable provided the user understands the internal workings of the shocks and has access to a quality shock dyno," says Bush.
"QA1 shocks are revalveable and it's not uncommon for a racer at the track to be revalving a shock in the race trailer," says Thiesse.
"Yes," says Keyser, "Integra Shocks are completely user repairable, revalveable, and serviceable. Revalving kits, tools, and instruction manuals are available to the racer."
"Pro Shocks are not user rebuildable. We incorporate a different design to flow the oil, and we feel our shocks are best serviced by us," declares Sandt.
Henquinet says hlins shocks are completely owner rebuildable and revalvable.
4. Can a user send shocks to you for repair and/or to rebuild?
For those of you who plan to travel next year, Thiesse says that QA1 has a network of authorized service centers that range from California to New Hampshire and from Minnesota down to Texas, as well as international service centers in New Zealand and Australia.
Keyser with Integra says, "Customers can call us and send their shocks in to be rebuilt or repaired."
As we learned in Question 3, Pro Shocks does all the repair and retuning of their shocks.
Bush offers, "Afco shocks can be sent directly to our factory or to one of our authorized rebuild centers located throughout the USA and abroad."
"The racer can either send their shocks to us for repair or to one of our various dealers," says Henquinet of hlins Racing Shocks.
5. What maintenance schedule should the racer be on to help eliminate failures?
"The best maintenance is to check for bent parts, leaks, and basic shock function. All of this can be checked by the user. They only need to push the shock in and make sure it does not bind or leak. We also recommend changing the oil at least once a season," explains Henquinet.
Stuck end bearings and binding...
Stuck end bearings and binding where the shock body contacts part of the chassis are more common problems that can have a negative effect on shock life.
Thiesse, too, recommends changing the oil and freshening the shocks every 20 to 25 races, for a normal season, depending on the conditions and environment to which the shocks are exposed. "If you run on tracks where higher shaft speeds and temperatures are generated, we recommend you change the oil and check the shock more frequently," says Thiesse.
Keyser tells us that it is a good practice to remove all the shocks from the car and visually inspect them to ensure that no damage occurred either from track conditions or a wreck.
He further states: "The shock bearings should be cleaned, checked for binds, and then sprayed with penetrating fluid to keep them free from binding. Shock shafts should be spun to check for bends and visually inspected for imperfections or 'pits' that may cause seal damage or oil leaks."
Bush says, "Shocks should be inspected visually on an event basis for obvious problems such as leaks, dents, binds, and so on. Gas shocks should be monitored for pressure prior to race day if possible. All shocks should be thoroughly checked after crashes, after running on extremely rough racetracks, or if the race car went airborne at any wheel."
"We like to advise our competitors that use our single or double-adjustable shocks to freshen them up every 500-600 laps," says Sandt. "Non-adjustable shocks need rebuilding at the end of every season. You should check or dyno the shocks after every race."
6. What is the best way for the user to check their shocks?
"The best way is to have the shocks checked on a quality dyno by a competent technician. Users can make basic checks for bent shafts by completely extending a shock then compressing it while twisting the shaft back and forth all the time checking for tight spots," Bush says.
If your shocks have remote...
If your shocks have remote canisters like this one, the connector must be kept free from dirt. Clean these often and spray with a lubricating oil that will prevent corrosion.
Sandt tells us: "The best way to check our shocks without a dyno is to stroke them by fully extending the shaft, putting it on the floor, and giving it a good push down. If you feel a spot with no resistance, the shock has air in it and should be sent back to us for maintenance." Henquinet gave us a very similar answer.
Both Thiesse and Keyser gave almost the identical answer-the best way for the racer to check his or her shocks is by using a shock dyno. Both agreed that most racers don't have that luxury, although there are several affordable dynos on the market today that are designed for the local racer. If no dyno is available, then "hand stroke" to check for any dead spots. But be warned that hand stroking cannot tell you if a shock's valving has gone bad because a person cannot bring the shock up to enough speed to check for valving tolerances.
7. Can shocks be mismatched to a particular type of racing?
"Yes, I cringe when I see a weight-conscious Street Stock racer put a small body shock on the front of his 3,200-pound car. It takes a fair amount of dampening to control a big car like that," Thiesse says.
Sandt thinks that some valvings work on some race cars, but not on others. An example of that theory is an asphalt car with a conventional setup versus a car with a Big Bar and Soft Spring setup.
Bush says, "Yes, it is very important to use not only shocks with proper valving, but also the correct type of shocks for the track conditions and type of race car."
Integra's Keyser insists that they "do not recommend the mismatching of twin-tube and monotube shocks on different corners of the car."
8. In both dirt and asphalt racing, the shock can experience extreme limits of travel and force. Which corner for each type of racing gets the most abuse, and why?
"The left rear on a Sprint Car is very important, while on an asphalt Late Model it's the left front. Like the Sprint Car, the left rear on a dirt Late Model and an IMCA-type Modified is the key to a good setup" says Sandt.
"It really all depends on the type of racetrack," says Henquinet. "However, in asphalt racing the right front usually is the most abused, while in dirt racing it is the right rear. These shocks generate the most heat, but the real abuse comes when the car hits something."
Shocks on the open wheel Sprint...
Shocks on the open wheel Sprint Cars are subject to damage not only from racing incidents, but also from mud and water. They need special attention after each race.
Another view is voiced by Thiesse: "In dirt racing, the left-rear shock in a Modified or Late Model seems to become the droop limiter, although we don't recommend the shock to be used in such a manner. In asphalt racing the huge rebound forces on the front [usually more on the left front] of the car can create high internal pressures and heat. These conditions tend to stress the O-rings and seals and may require a higher maintenance program."
"In pavement cars, we find that the most abuse is put onto the front shocks," Keyser says. "Most pavement cars are running a big sway bar along with very soft front springs that are run close to or totally coil bound. This type of setup puts a lot of the load of the chassis on the shocks themselves.
"In order to get the cars to pin the nose to the ground for optimum handling and aerodynamic reasons, the front shocks are often built with six times the amount of rebound found in a typical dirt car shock. That adds stress to the valving system and oil in the shocks, and header heat from a pavement car's exhaust has a huge wear factor on the front shocks," explains Keyser.
"Hiked up dirt chassis tend to top out the left-rear shock and bottom out the right-front shock. Asphalt race cars that use soft front springs can bottom out the front shocks during braking. Severe shock bottoming out can be very detrimental to the life of the shock. Shock bumpers can help prolong the life of shocks that tend to bottom," Bush suggests.
9. What typically causes premature failure of a racing shock?
"All of what we have talked about above!" exclaims Bush. "Hiked up dirt race cars tend to bind the shocks [top and bottom], which can damage shafts, seals, and rod guide bushings."
"The most damage that occurs to shocks are from track conditions, wrecks or poor maintenance," Keyser says. "All shocks need to be maintained weekly and put on some type of rebuild schedule. Dirt shocks are more likely to develop imperfections in the shafts because of the track surface and rocks or debris that they may encounter."
This coilover spring and shock...
This coilover spring and shock combination is popular with all forms of racing. The racer needs to be sure the spring does not contact the shock body in high load situations, where the spring will compress excessively.
"A shock is a mechanical device with many components such as seals and O-rings that can fail at any time due to dirt and grit, heat and binding," Sandt adds. "Spring collapse will also create rubbing on the shock, which will wear it out. However, crashes still seem to get more shocks than anything else."
From Henquinet's experience, "Premature failure usually is the result of crashes. The other main cause is bottoming out or spring contact."
QA1's Thiesse agrees: "Anytime a shock is bottomed or topped out it can cause premature failure. One of the biggest issues with today's dirt Modifieds or dirt Late Models is the extreme indexing of the birdcages. If your shock is attached to this birdcage, it could travel the bearings past its full misalignment range and bind the shock. The bind will cause a side load to the piston rod and will prematurely wear the O-ring and bushing in the closure nut and ultimately cause the shock to leak."
10. Is there a preferred mounting height for shocks (piston position in the tube) in relation to the amount and direction of travel each shock will experience?
"The rule of thumb used to be 60 percent of the travel was allowed for the compression stroke. Today, there is no right or wrong answer, as long as the shock can function without topping or bottoming out," Thiesse offers.
Henquinet tells us, "Generally, you want the shock to be mounted so it is as close to the middle during the actual use on the track. However, you have to make sure it does not bottom out or top out. Where the main piston is located within the shock body has an effect on the efficiency of the shock, but it is very slight."
Bush offers a different view: "Ideally, the piston should operate as deeply in the shock body as possible. This arrangement provides the most stability for the shaft and piston assembly and enhances seal, bushing, and shaft life."
"Integra recommends that the shocks be mounted in a manner which is bind-free, with about 50 percent of the shaft showing with the chassis at ride height," according to Keyser. "This mounting procedure will aid in the prevention of the shock bottoming or topping out, both of which may cause damage to the shock."
The bottom line is that racers need to help their shocks by installing them properly to eliminate binding, checking them often, and having them rebuilt periodically. Think about how you use your shocks and what they go through. Then you will be able to avoid the pitfalls that go with shock problems.