Different types of Fat Cat Motorsports bump stops (Manufactured by Speedthane)

#bumpstops #FCMElite #Speedthane #howbumpstopswork
Want to learn How Bump Stops Work? Then WATCH THIS UPDATED VIDEO for a better description!
• How Bump Stops Work - ...
A BUMP STOP (also called a 'jounce bumper' and sometimes a 'bump rubber') is a compressible suspension component with 2 main functions:
1. It prevents metal on metal contact and damage to the suspension components when moved (either gradually or suddenly) to the full compression position, such as after hitting a sharp bump or going into a deep pothole.
2. It changes the handling behavior in medium to harder cornering (whether intentionally hard driving or unexpected emergency situations) to add additional roll stiffness and control the chassis.
Usually bump stops are designed to increase the understeer of a vehicle at the cornering limit which manufacturers feels is the safest response for the average driver.
On many vehicles, the bump stop is located somewhere along the shock shaft as in this example. Many OE suspensions also attach the dust boot to the bump stop via a ring. On some vehicles (and usually on the rear suspension), the primary bump stop is located on the suspension arm and not the shock. Also, there can be a secondary bump rubber (usually literally made of rubber) located on the suspension arm to provide additional protection at full compression. The Mazda 6 rear suspension is an example of this separate primary bump stop with secondary bump rubber.
Bump stops usually sit over a shock or strut shaft but may also be used externally to the shock/strut such as on a control arm or axle. Trucks and other heavy-duty vehicles may have secondary hard rubber bump stops in addition to softer foam or poly-urethane stops on the shock shaft or co-axial to a suspension spring.
Additionally, bump stops can be used to change vehicle handling characteristics, especially in moderate to hard cornering.
Original equipment manufacturers typically use a much firmer front bump stop than rear to add additional front roll stiffness in harder cornering. We utilize 3 different densities to perform our bump stop tuning 'magic!' Red is approx 100 lb/in, White approx 200 lb/in and Blue approx 330 lb/in. We adjust lengths from 25 to 76mm long and sometimes use two densities depending upon the application.
===
A bump stop is a compressible suspension component designed to prevent metal on metal contact (and subsequent damage or unsafe driving characteristics) as the suspension undergoes extreme compression, such as after hitting a bump or going into a dip / pothole. Additionally, bump stops can be used to change vehicle handling characteristics, especially in moderate to hard cornering. Bump stops usually sit over a shock or strut shaft but may also be used externally to the shock/strut. Trucks and other heavy-duty vehicles may have secondary hard rubber bump stops in addition to softer foam or poly-urethane stops on the shock shaft or co-axial to a suspension spring.
Some components of a shock/spring/shock mount assembly are shown and various types of bump stops available for different cars, applications and customer needs.

[@SuspensionTruth]

For a more FUNCTIONAL explanation of how a bump stop works, watch this newer video 'An Analogy to Walking': kzbin.info/www/bejne/fpa9pHiolMxld7M

[@3jbeezy]

love your intro!

[@nanbil]

I have a set of Koni sport struts with the OEM mazda speed springs on my 2003 Miata, your application guide lists the Koni strt struts but not the Koni Sports. Curious as to which bump stops I should use?

[@SuspensionTruth]

They'd be equivalent.

[@MaximoMotor]

You talk about shape, material, types, location and how important it is but you never said what's the actual function of it or am I missing something?

[@SuspensionTruth]

A bump stop has several functions, including protecting the suspension from damage under a full compression event, and modifying the vehicle's handing (usually to keep more weight transfer across the front axle during cornering). I've added additional comments via annotations. Please also watch the additional videos in the series.

[@SuspensionTruth]

A newer, more functional video on how bump stops work in practice: kzbin.info/www/bejne/fpa9pHiolMxld7M

[@SpicyGuac28]

My driver side bump stop is torn almost in half. Could that be the reason for a clunking/bumping sound when I go over speed bumps? Also, steering wheel makes a slight clicking sound when I turn it-was wondering if that was also because of the bump stop tear?

[@SuspensionTruth]

For the source of the steering wheel clicking, it does seem likely to be from the damaged / worn bump stop. But yes, a nearly-torn-in-half bump stop isn't going to protect your suspension at full compression or heavy compressive loads. I'd get that sorted out quickly. You can buy a high-quality stop from 5xracing.com (Speedthane brand) in a similar length to what you have. If it's a strut we only have one length - 47mm and ~19mm ID shaft. For shocks there are a variety of lengths and densities to choose from.

[@Touphguy123]

Will removing numb stops stiffen up your suspension or soften it?

[@SuspensionTruth]

You mean 'bump' stops. That's an extremely general question making it really impossible to answer except in generalities. The specific answer for your vehicle depends on how much suspension travel you have, the spring rates, the roads you drive, and the stiffness / length of the bump stops. Without a bump stop, your suspension may initially feel softer, but if you hit a big enough bump you could bottom the shock which will feel VERY harsh, compared to having a bump stop in place that would soften that harshness. I would NEVER recommend running NO bump stop as you could cause damage or a serious problem during an unexpected bottoming-out event.

[@mickeyp1291]

Worst explanation ever. I still don't know what a bump stop is

[@SuspensionTruth]

It wasn't very functional - this newer video is better: kzbin.info/www/bejne/fpa9pHiolMxld7M

[@chantelnind7929]

what is the purpose of bump stop rubbers?

[@SuspensionTruth]

+Chantel nind If you mean a 'bump rubber' as in the short kind, those are used typically on stiffly-sprung racing setups to protect a shock at full compression so it doesn't bottom out with metal-on-metal. The "bump rubber" is only designed to be a safety device, not an active part of the suspension like a "bump stop" is.

[@SuspensionTruth]

+Chantel nind If you mean a 'bump rubber' as in the short kind, those are used typically on stiffly-sprung racing setups to protect a shock at full compression so it doesn't bottom out with metal-on-metal. The "bump rubber" is only designed to be a safety device, not an active part of the suspension like a "bump stop" is.

[@shaunskii]

For my BMW with the sport package, should I stick with OEM BMW bumpstops so it doesn't change anything? There are cheaper options from Rein, Febi, etc. But will these possibly differ from the OEM and possibly give me a different ride?

[@SuspensionTruth]

I think you've answered your own question - don't change anything if you don't want the ride to be different. However, I was able to reduce understeer by removing some of the upper section of the front OE bump stop on my E46 330i's sport suspension. I found that an improvement.

[@shaunskii]

@@SuspensionTruth awesome thanks 👍

[@Badboyzfitness]

So what are the symptoms of your bump stops going out what will happen to your truck?

[@SuspensionTruth]

You would notice very harsh impact and 'bottoming out' events, potentially even hear metal contact. It's a good idea to check your dampers and struts every 30,000 miles for wear, or as your owner's manual recommends.

[@gixxerboy555]

Hi,my Hyundai i30 allway's give a hard punch in my back when I ride over a bigger roadbump..is the bumpstopmaterial too hard or is it maybe too long?I allready thought to change the shockabsorbers but now I saw this video..any help would be nice..(the problem is only in the rear-axle..in front it's perfect..thanx

[@SuspensionTruth]

It could be the bump stop engagement or the rear damper is jacking down causing you to pull harder into the bump stop. You might want to get some zipties or take some suspension travel measurements. See my videos on the 2016 Mazda Miata for info on how to make bump travel measurements. Good luck.

[@ayeitme6773]

I wonder what I could use in my current coilovers with 14&10k spring rates on my is300... wagon version aka sportcross in USA and where I could buy some I honestly just do spirit driving on the canyons

[@SuspensionTruth]

Ideally, you'd need to know what is there now (dimensions and approximate stiffness), plus much additional travel is available. That's why I or the owner do suspension travel measurements on all new builds whenever possible. But, if you're willing to pay for my time and give me more information via the consult form, I could make some recommendations on a bump stop package to start with: www.fatcatmotorsports.com/fcm_elite_consult_form.htm#fee Having some packers on-hand to adjust travel (in case you need to reduce the bump travel) is always helpful.

[@ayeitme6773]

@@SuspensionTruth thanks I'll get more info on my setup .. hehe never thought about those details

[@SuspensionTruth]

👊🏽 I recommend watching the set of videos I did on making bounce frequency measurements and suspension measurements on a 2016 Mazda Miata.

[@frankfitzpatrick5300]

Hi , I have a 95 miata , completely stock standard suspension , getting ready to go pluss one on tire & wheels ...15×7 Advanti storm s1 stock offset & 195-50-r15 hp or extreme performance tires ...I want use your bump stops , daily driver , perhaps a little on ramp , off ramp mischief & the occasional canyon runs ..shhh. don't tell anyone (CLASSIFIED) ...I will inspect shocks , which were recently replaced , dont see any seal leakage , and car handles excellent as is ...what woud you recommend for the stock Showas I believe ..I would also consider Bilstien shocks...

[@SuspensionTruth]

Frank Fitzpatrick For (CLASSIFIED) aggressive street fun use, I'd suggest 36/46 - the firmer front will induce a little understeer which lets you push the car without sudden oversteer. You can also use packers in the rear to encourage more rotation. Different way to play this but packers will probably be a really helpful fine-tuning aid. You can buy our kits now from 5X Racing.

[@justinatkins3031]

Anything to worry about with a bump stop sliding freely along the shaft? My car seems to have a cap to keep the stop securely up top, but I've seen many (like in the first picture of this video) that simply let it drop down and move against to top of the damper. Would bump stop material/cap design come into play, or would it be fine either way? If they are supposed to be snug in the cap up top, are these designed to fit inside of a specific cap? In my case, on a 2011 RX-8 w/Koni Yellows.

[@SuspensionTruth]

I've seen most OE setups utilize a cap for the bump stop. That is probably ideal. However we've used bump stops that float on the shock for years. I can't identify that there's significantly more wear happening in that case. Perhaps with lower quality materials that would be the case. Our stops are used by NASCAR teams also where reliability is important. Just select the density / length you need and go with it. For the RX-8 I'd say 58 white front and 58 red rear assuming stock sways/springs. Contact me through the website for more details.

[@ElectricRides]

By law we need to have these in out cars in Aus, do most coilovers come with the bumpstop ?

[@SuspensionTruth]

I believe most do, but some tend to be very short and firm so contacting the bump stops can feel very abrupt. This also depends on how the damping is tuned; a very strong rebound-bias will make the bottoming out feel worse than a damper that has more neutral bias (where rebound and compression are more proportional to each other).

[@schizobipolarjoe]

how do you know if a coilover is hitting the bump every now and then I get a boom boom sound driving on ruff roads I don't know if I'm to low in the front or if it's my damper settings. I wish some one would make a video on what that sounds like.

[@SuspensionTruth]

You probably won't know if you're hitting the bump stop as that should be a pretty smooth behavior. But if you're hearing booming then you might NOT have bump stops any longer (they can and do degrade over time). Take a look under the dust boot or have a mechanic examine to see if the bump stops are gone or shredded and in need of replacement.

[@schizobipolarjoe]

Thanks will do. coils are around 2-3 years old around around 15,000 miles on them. would certain tires also play a roll on how the car sounds ? I'm trying to tune and build a 2012 subaru impreza to be a good daily and sts autocross car. right now it has feal 441 coilovers, stop tech pads, and uhp all season. I'm trying to learn about all this stuff so I'm just not throwing shiney parts at a car with out understanding it. I want to find stuff that I can go does it works for my needs, and does the prices fit my budget.

[@Twiggyay]

I know this video is HELLA OLD, but i'll still ask. Got myself a 2002 Mercedes W203, and at first only the rear right bump stop was worn out. Now i'm hearing signs of the left going as well. Is this something i can fix myself with a wrench and some elbow grease? No prior experience dealing with cars before, but i enjoy learning about them and i plan on changing all vital fluids and those bump stops in a few months when the snow clears because i have no clue if the prior owners did anything to help it live as long as it can.

[@SuspensionTruth]

Thanks for your question. Are you sure it's the bump stops and not a suspension bushing? You could push back the rear shock's' dust boot to see what condition the bump stops are in. To replace it, you'd need to pull the shock but that's probably fairly easy as I believe the damper and spring are separate on the W203 Mercedes. You ought to have a factory service manual if you're working on your own car but it's doable work on your own with basic tools and proper jack stands. You could get a replacement factory stop, or for a likely durability upgrade, find out what length the factory is and choose a 58mm red or 76mm red from the Speedthane / Fat Cat Motorsports line. Both 5x racing and summit racing carry the Speedthane stops which FCM sells. Good luck!

[@Twiggyay]

Suspension Truth thanks for answering! If it is a bushing, is there anything i should look for? What are tell-tale signs? It's the first car which is truly mine, and i intend to do everything myself. Learning is what it's all about.

[@SuspensionTruth]

@@Twiggyay If you get squeaking when going slowly over speed bumps that could be worn bushings. Get a relationship with either a good local shop or a freelance mechanic. Yes, learning as much as you can on your own is so important and having people to learn from is gold.

[@ericmorejon5290]

would these work on rear shocks on a motorcycle? sportster?

[@SuspensionTruth]

Yes, they would, and most likely you already have bump stops present, but you could do further tuning for driver / passenger weight, riding style, etc.

[@michaelosinowo226]

Is the bump stop a spring or a damper?

[@SuspensionTruth]

It primarily operates as a progressive spring but it does have some intrinsic damping.

[@michaelosinowo226]

Suspension Truth is there a way of modelling it mathematically because I am working on a quarter car suspension system and I am meant to include a bump stop to prevent damage in the suspension system and restrict the movement within a certain distance

[@SuspensionTruth]

I suggest leaving out the damping behavior and focus on the progressive spring rate. I've posted some characteristic curves you can do a curve fit to and get an exponential equation for. That's the best I can offer. Good luck!

[@rramos7488]

do you have a website i can purchase these bumpstops at?

[@SuspensionTruth]

You can purchase FCM (Fat Cat Motorsports) bump stops through 5XRacing.com.