How Shocks Work - Tuning your suspension with 'packers' or bump stop spacers

Update: To purchase 'packers' or bump stop spacers, go to 5XRacing.com. They are an authorized distributor of Fat Cat Motorsports bump stop hardware and complete kits
Did you know there's a very simple yet effective way to adjust your car's handling? It's called a 'packer' and functions by causing a bump stop to come into play sooner. Certain forms of motorsports use these very frequently. Whether you drive aggressively or actively race your car, having a few of these in your toolbox are a quick way to change to from understeer to oversteer or vice versa.
Typically, we use a 1/8" or 3mm packer that can be slipped over the shock shaft by hand or with needle-nose pliers. In most cases you need to jack your car up and then can install the packer. The springs usually do NOT need to be removed - that is what makes these so powerful!
Usually stacking 2 to 4 packers is ample to make a big change in the cornering dynamics. If you also have too much suspension travel and need to prevent rubbing of your wheel or tire on the body work then a packer is effective in this. However, I don't believe in using bandaids if you have a structural issue with your car. IMO, it's not correct to compromise a suspension's operation in favor of a poorly chosen tire diameter, wheel offset, or body kit. But, this is a tool that's available.
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[@roundabout136]

I'll definitely be keeping this technique in mind. If suspension travel wasn't a concern, why tune out/in OS and US with packers rather than other methods like tire pressures, anti roll bars and such if you assume all are readily adjustable? -Adam

[@JoseMorales-vw4qf]

Thank you for passing your info.

[@SuspensionTruth]

You're welcome, thanks for your comment.

[@SuspensionTruth]

If it's not leaking or clanking then you are probably okay. To be safe I'd take the shock out and cycle it by hand. Got to use the right components to keep the bump stop in place and doing its job!

[@blotmaster1]

This is a very well done video. Thumbs up

[@SuspensionTruth]

Thank you, I appreciate that!

[@SuspensionTruth]

Hey Adam, Good question. Vs. sways, I use packers more because they allow rapid and finer range of adjustment vs. changing sway bar arm position. Bars usually have 2 or 3 holes at most and the change is more dramatic than a single 3mm packer adds, especially to prevent preload from a new end link length. Blade type bars, in my understanding, allow fine adjustment but most people don't have them. Changing tire pressures may take you out of an optimal grip zone so I almost never use that option.

[@dianat.2804]

Handsome and knowledgeable.

[@SuspensionTruth]

Thank you for the second - the first is my parents' fault.

[@Racecarbuilder22]

I am interested i want to your website i find it hard to navigate to find where to buy it

[@SuspensionTruth]

For small parts go to 5XRacing.com. My focus is in on building uniquely-optimized suspensions, a high-end service.

[@abh1945]

I don’t need to install this black ring on my Mini Cooper s right? And I also ordered bilstein B4 (the black shock or strut) and I didn’t get this black ring with it!

[@SuspensionTruth]

most dampers don't come with a packer. Each vendor is different.

[@yo_ez1590]

So packers don’t effect ride height correct? For example if I put 2 16mm packers on each strut, I won’t raise the front of my car? Correct?

[@SuspensionTruth]

If the packer is tall enough makes the bump stop engage at static height then yes, it can raise your car. If you actually mean using (2) 16mm tall packers on each strut (32mm total packer thickness!) that seems excessive - why are you doing that? Even if it doesn't raise the height, if you cut down on the available bump travel too much your ride will get rougher and handling less predictable. Usually I work in 3mm thickness / height increments, potentially going up to 4 packers if there's room (YMMV). More than 12mm of stacked packers suggest you might consider a stiffer bump stop, or a spring / sway bar change.

[@suchattrakulyingyong1515]

i have never seen this bump stop and dust boot type.

[@SuspensionTruth]

And now you have.

[@pinktacoetr]

Great info..I just installed koni fsd and Eibach pro kit springs on my 335i and have been trying different bump stops since the E36 M3 they recommended bottomed out easily and had too much understeer finally got it much better with Speedthane bump stops hard,it still needs some fine tuning will try some packers.

[@SuspensionTruth]

Good to hear you're experimenting. Though from what I understand, the Koni FSD design requires sufficient bump travel to prevent the inertial valve from engaging too often (which causes the compression to be very stiff). So, by lowering the car and also using packers you might make the situation worse. Just keep that in mind...

[@SuspensionTruth]

The idealist in me says I ought to gather enough data to have a nearly ideal setup for any given surface I run on regularly. Going to a new track, I'd rather note any change in behavior then add a packer making a note of how the setup needs to be adjusted the next time I'm at that location. Time is usually at a premium in racing situations. In other situations I've kept a light alum racing jack, jack stands and packers in the car with me for (ahem) road evaluations. Quick change and off I go!

[@lifenz1]

is it normal that your bump stop is always active! and what cause the packers to affect the car's reaction into corners ?

[@SuspensionTruth]

Normal for a production car? In almost all cases, yes. Should you feel it engage harshly? NO! A modern bump stop is a very sophisticated device, more so than the primary (steel) spring. Adding a packer or bump stop spacer is effectively lengthening the bump stop. You can also think of it as lengthening the shock body - making the shock 'taller' - so the secondary spring rate of the bump stop begins to affect the cornering behavior earlier in the cornering process.

[@bilaltariq7819]

@@SuspensionTruth Hi any chance you could elaborate on it the "bump stop is always active" bit? Do you mean there is so much movement of the damper shaft up and down that the bumpstop is lightly engaged a lot?

[@safecarsforyou]

Can a Toyota etios bump stop be reused after changing the shocks its quite different from the one you showed on the video, infact mine is broken at the level of the folds much below the nut you use to dismantle the shock

[@SuspensionTruth]

If a bump stop is broken, I would recommend replacing it with a new one.

[@safecarsforyou]

@@SuspensionTruth thanks for your prompt reply

[@maneki9neko]

So, if I have this right, if the car is understeering you want to stiffen up the rear by engaging the rear bump stop sooner. And if the car is over steering I stiffen up the front by engaging the front bump stop sooner. And 1/4" of packers is adequate to achieve a noticeable difference on a double wish bone suspension.

[@SuspensionTruth]

Yes, that's been my experience. 1/4" is 6mm which would certainly create a noticeable change in handling PROVIDED the bump stops are nearly or already engaging.

[@maneki9neko]

I have a stack of slotted nylon 2.5 mm washers, and I am going to give this a try. Thank you for the guidance.

[@es1777]

Hi, I have a question, Im not trying to change the ride performance but more comfort. I had kyb struts and new honda springs installed on my 01 integra. Same old bump stops. The ride feels goods, but on ny roads, which are very rough filled with potholes, when theres a hard bump, it feels horrible. I suspect the bump stops are bad, maybe the bushings? You think the bump stops make a big difference in absorbing those really harsh bumps? and do you think the oem bump stops would make it soft? I want a soft smooth nice ride. Thanks!

[@SuspensionTruth]

By now I trust you've done something to make the ride better. New OE bump stops should certainly help, but a higher quality replacement like our FCM bump stops, made by Speedthane, will almost certainly last longer.

[@TheZeroLatitud]

I'm looking to replace shocks on my car (NB Miata) for the 1st time ever and I feel so lost. Didn't know there were other parts to consider besides just the shock and the spring. Thanks for this video.

[@cussyjnbaptiste9856]

Where can i get the spacer?

[@SuspensionTruth]

Search for 3mm shock spacer on 5xracing.com.

[@SuspensionTruth]

Thank you! I love making them. Your suggestions are welcome :)

[@christopher23.]

I have eibach coils on my 14 RAV4. My shocks bottom out Over speed bumps. What can I do ?

[@SuspensionTruth]

Lowering springs generally suck. I don't see a rebuildable Bilstein for your '14 RAV4. If someone else makes one you could try to get them tuned for more 'rally-style' behavior. No other easy solution than to go back to stock springs to regain travel.

[@alyousuf]

obviously this only applies if you're rolling onto your bumpstops to begin with

[@SuspensionTruth]

Yes, obviously. If you have a non-modified production car, then you certainly are. If you're lowered your car without paying attention to spring rate and suspension travel, then you're using the bump stop even more so. Porsches, BMW, Mazda, Nissan, Honda and many more all actively use the bump stops in roll as well as ride.

[@christopher23.]

What if my struts bottom out over speed bumps??will these help????will these fix that?

[@SuspensionTruth]

Did you cut the bump stops? Why is it bottoming to begin with? Important questions. 'Fix' is a big promise. As part of overall suspension tuning, packers can be helpful but they're not a solution to poor overall suspension behavior.

[@joshssauce]

My bumpstop hit my upper washer ( the washer wasn't large enough and the bumpstop went around it ) and my shock bottomed out. Do you think my shocks okay? Miata bilstein sport shocks and it was the front

[@SuspensionTruth]

Bilsteins are really durable so it's likely the damper is fine as long as there was some bump stop present. If you see leaking, the damper doesn't move smoothly under compression, or you can hear air pockets inside the damper then there was internal damage and the Bilstein should be repaired or replaced.

[@cristianmartinez-vj1vs]

Hello do you recommend getting a spacer lift on a 2019 Tacoma I don’t want suspension issues in the future ? thanks for the videos !

[@SuspensionTruth]

I suggest you communicate your goals with an off-road / 4x4 specialist. Every change has pros and cons and deviating ride height far from stock in particular certainly does.

[@boro92]

i'm sure this has been tested. However, wouldn't a slotted packer spread under load and have reduced if not nil-effectivness?

[@SuspensionTruth]

Good question. This is how I see it - any potential for a packer to spread under load depends on: a) the compression strength of the packer material, b) how much load is present, c) the proportion of total load that becomes a lateral force vector (which would stress the packer along the slot and induce it to spread) vs. proportion of total load that becomes a longitudinal force vector (which pushes the packer into the damper top cap/rod guide, or the upper shock/strut mount). The packers we use are made from Delrin and are quite strong in compression. The load that goes lateral to spread the packer seems to be rather small, especially in proportion to the much greater load pushing the packer into the damper. Of course, you also want to make sure the slot in the packer isn't excessively wide, otherwise any lateral load present could push it off the damper's shaft. I've never heard or seen myself a packer popping off a shaft, and from testing I've done and my customers have, the presence or absence of a single packer is DEFINITELY noticeable in the car's handling. You could use a material that's too soft, or a packer that's too wide, and in either case get a ineffective packer, but as a first-order glance I don't see that being the case with our methods.

[@hope4824]

Does the bump stop affect the height of the car? That's if the car is lowered?

[@SuspensionTruth]

If you try and lower the car but end up lowering onto the bump stop then yes, the bump stop will end up raising it some. More importantly is lowering with too-soft a spring will make the suspension harsh and bottom out more. This is why I hate the typical aftermarket lowering spring that gives you 'stance' but is too soft and has you run into the bump stop(s) much more often.

[@alfs8]

This is a very good video. I'm curious about what if I wanna use the packer on an inverted shock? The Bump stop is hiding inside of the tube, how could I do it without tears apart the shock?

[@SuspensionTruth]

Great question! Yes, that's one challenge with tuning via packers on an inverted strut. Assuming that's only on the front (the Pontiac Fiero comes to mind as a rare exception with a front shock and rear strut); I typically use a soft-enough front stop to not induce understeer and leave the front alone. Then, I do the packer tuning on the rear which would be more easily accessible. This is how I tune my E46 BMW (front inverted strut, rear standard mounted shock with accessible shaft) and its very effective.

[@alfs8]

@@SuspensionTruth Thx mate, I'll just leave it there LOL, Too difficult for me to finish it in one piece.

[@roborob23]

I have a rx8, can I change the bump stop from inside the truck?

[@SuspensionTruth]

No, you have to take the damper assembly out first, requiring a spring compressor.

[@taylorvance6254]

It seems to me that if you are driving on the bumpstops, it would cause an abrupt if not instantaneous increase in spring rate which would cause sudden changes in understeer or oversteer which would be really difficult at the track.

[@SuspensionTruth]

If you're using a rubber or (hard) polyurethane bump stop, your observation would almost certainly be correct. However, a modern MCU (micro-cellular polyurethane) bump stop is designed to be very soft on initial engagement due to how they shape the nose of the bump stop, plus the ridges and sections placed along its length. You're not likely to feel anything abrupt unless the bump stop has degraded and is not functioning properly. I'm not the only one who has used bump stops effectively to make handling adjustments while ensuring the vehicle remains predictable. Sounds like you need a ride in one of our Elite setups to see it first hand! Please also check out the other How Bump Stops Work videos I have on bump stop Force vs. Deflection curves so you can see how forgiving and friendly a quality bump stop is. For example, can skip a couple minutes in: kzbin.info/www/bejne/sH7LfGZuZrqCbpI

[@taylorvance6254]

Makes sense. Got the FatCat bump stop kit for my spec miata but need to corner weight / align. Thanks for your help.

[@ayeitme6773]

2k19 .... dang ... good info ... definitely gonna do a proper setup on my next coilovers Just realize how uneducated we're about suspension Thanks for the great content

[@SuspensionTruth]

Thanks for being curious. Please share this channel with your car community - the more people thinking, learning, and sharing the better-off we all are.

[@ayeitme6773]

@@SuspensionTruth will definitely do man .. thanks for taking time to do all this videos and reply . Great customer service hehe jk

[@SuspensionTruth]

Thanks, Mauricio!

[@roundabout136]

Great video Shaikh, keep them up!

[@EM1Nate]

Very informative video Great Job!!!!!!

[@SuspensionTruth]

Thank you!

[@mig360m]

what size bump stop and packers to use on my mazda protégé??

[@SuspensionTruth]

+Mig Ram I can't say definitively without looking at the OE bump stops and knowing how much lower you may be, but my guess would be to use a 47mm strut-style front bump stop and 58mm red rear bump stop. That's essentially our 'Mini Cooper' bump stop kit available through 5xracing.com

[@mig360m]

sorry. I have B&G springs 2 inch lower with KYB shock. thanks for any info

[@SuspensionTruth]

Take a measurement of the front strut and rear shock shaft outside diameter, select a bump stop that's wide enough inside diameter and go from there. My recommendations are in the first comment. DIY man!

[@mig360m]

ok thanks