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Steeda Mustang 'Stop the Hop' Street Starter Kit (2015-2021)

18 Review(s)
$50.00 (9%)
Steeda's easy to install S550 Ford Mustang "Stop the Hop Starter Kit" eliminates wheel hop, squares the subframe to the chassis, & will not increase NVH. Kit includes American made chromoly subframe support braces, CNC machined aluminum bushing support sy
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Part Number: 555 4455
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Our Sales Experts take calls all the time from enthusiasts that want to eliminate wheel hop while also staying on a tight budget. This is where the Stop the Hop Starter Kit comes in. Our team of engineers got together and came up with the best 3 parts for eliminating unwanted wheel hop in the new S550 Mustang. A kit that gives you the fundamental foundation for ultimate traction and suspension compliance. As we have explained before, the factory IRS subframe, (often inaccurately referred to as a cradle), mounts to the S550 chassis with 4 mounting locations utilizing 4 soft rubber bushings with plenty of voids, even in the bolt holes. The kit we put together addresses these issues and more.

Which "Stop the Hop" Kit is for you?

First is our Alignment dowel kit. This fills the factory bolt hole voids with CNC machined delrin inserts that will square up the rear subframe to the chassis. By filling these voids we are also limiting the side to side and front to back movement of the subframe that is present under hard acceleration and braking.

Second is our tried and true IRS Subframe Bushing Support System. This 8 piece kit was a first of it's kind in the performance aftermarket and so innovative and popular we patented it's design! Made in house from billet 6061 aluminum and featuring stainless steel hardware, this kit fills all the factory voids in the IRS subframe mounting locations. It's job is to prevent up and down movements of the subframe.

The 3rd and final piece to this kit is the strongest support brace for the S550 IRS on the market!! Made in house from chrome moly steel, this brace is designed to support the factory subframe by directly tying it into the chassis at key mounting locations. Using factory mounting locations on the factory frame, this 5 point brace supports the front factory mount and the lower control arm mount as well. A simple bolt in design this brace ties the subframe to the chassis in the best possible way.

The best part about this kit, is the price. These 3 parts were the first of their kind for the S550 Mustang and nothing will prevent unwanted subframe movement or wheel hop better than this kit.

NOTE: Steeda IRS Subframe support braces will not fit convertible

Kit Includes:

  • 555-5754 - Steeda IRS Subframe Support Braces
  • 555-4437 - Steeda IRS Subframe Bushing Support System
  • 555-4438 - Steeda IRS Subframe Alignment Kit

Product Benefits:

  • Eliminate wheel hop while not increasing NVH
  • Eliminate subframe movement
  • Simple install
  • Squares subframe to the chassis
  • No permanent modifications

Notice how composed our Q500 is throughout this turn at Palm Beach International Raceway.

Steeda S550 Stop The Hop InfographicFind out which Stop The Hop Kit is best for you!

CA Residents: Cancer and Reproductive Harm WARNING

Hey guys this is John from Steeda. I want to get you guys a little more info today on our "stop the hop kit" we've got three available now including our new stop the hop enthusiast package. Let me go from one division we're gonna start with our stop the hop starter kit. Now this kit includes our steel subframe braces, which are these right here. They help eliminate lateral movement in the subframe itself and they leave it to the chassis more effectively. We've also got our Steeda subframe alignment Kit. Now these dowels right here they fill the voids between the stock bolts and subframe a little bit different size they can have up to a quarter inch of movement in most cases in any direction. This helps keep the rear end center every time under the car. And to close out the starter kit we've got the subframe bushing support system. but what these do is they fill the voids in the stock bushings and that helps to control the deflection and the oscillation of the bushings under a hard launch. It gives more consistency in less wheel hop. Now if you want to turn the starter kit into an enthusiast kit, move in and move towards our Steeda lower control arm spherical bushings. We found it up two degrees of movement is found in the bushing under a hard launch and this doesn't allow it. So it's going to lead again to more consistent launches and less wheel hop. And we found our Steeda "stop the hop ultimate kit" what this is, is it builds on the starter kit and includes our newest Steeda toe links and these help control the toe on the car they're a lot stronger than a factory piece, they don't have as much movement or flex to them. And we got our CNC machined Steeda vertical links. These are one piece CNC designed very large bushings. We offer it with urethane or delrin, Depending on how stiff you want them. And what that means is it helps to stop binding which we found in a stock, which is what Ford calls it, and not binding actually creates an artificial spring rate which changes as the increased movement on the rear axles and that leads to a lot of wheel hop issues inconsistency. These are going to eliminate that problem and if you want to add it the spherical bushings to this kit we've got a drop-down our website. Just let our experts know. You can also add our Steeda differential bushing insert system to any of these kits and you really get the ultimate control of the rear end on your drag car. Now if you've got any questions about your project, need some tech advice, we go by the motto of speed matters. It matters to us, it matters to you. We want to help you guys get on the track have fun, turn some great results. It's what we've been doing for 30 years. Give our performance experts a call. We'll be more than happy to help you out. Thanks for watching. I'll see you guys soon.

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Fitment & Features


Manufacturer: Steeda Autosports
Made in USA: Yes

Installation Information:

Level of Difficulty: Medium
Install Time: About 3 Hours
Tools Required: Basic Shop Tools

Vehicle Fitment:

Fits Model Year: 2015, 2016, 2017, 2018, 2019, 2020, 2021

Customer Reviews

Rating Snapshot

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Average Customer Ratings


Yes, you 100% need this!
In short, just buy it, don't hesitate, buy it! If you own an S550,..BUY IT! Any praise I give this kit cannot fully describe all of the things this corrected on my 17 gt. (which is daily driven 365/year in Michigan.) Took longer to drop the full stock exhaust than to drop subframe and install all 3 components in the kit (btw it got Steeda H-pipe 2 months later) It really feels like it took a lot of the drive line slop out, throttle to drive line engagement seems more responsive, especially if you just blip the throttle. Oddly enough it also seems to have calmed the ratchety synchro feedback when shifting from 1st to 2nd and 2nd to 3rd that has been there from day 1(redline fluid and decent clutch helped but did far less in stopping it than this kit) This makes sense mechanically for a car like mine that was put together off center, though was still an unexpected bonus.
Did you find this helpful?  2 of 2 Found Helpful
Verified Buyer  
Does what it says
My Bullitt (with low restriction air filter and Steeda tune) puts out even more horsepower and torque than stock. Even so, with the addition of this kit the rear end stays planted under hard acceleration. The traction control may light up depending upon grip, temperature, and road conditions but the rubber stays in constant contact without the rear wheel bounce you experience under the stock suspension setup. Very satisfying results for a smoother, more connected launch.
Did you find this helpful?  3 of 3 Found Helpful
Great Improvement
I ordered this kit and had it installed, It stopped alot of my wheel hop and the car handles much butter all around. I would recommend this kit to anyone looking to improve their cars handling.
Did you find this helpful?  1 of 2 Found Helpful
Makes air suspension feel so much more planted
Upgraded my S550 with airlift suspension kit. Surprise surprise the car felt a little floaty at times and launches felt a bit loose. The kit made the car feel so much better in all aspects. Use a crowbar when putting on the top bushings. Forget trying to use a screwdriver just bust out the big guns from the start. Trust me it will make life much more easy. I tried a screwdriver for about an hour, busted out the trusty crowbar and had it done in 3 minutes, not exaggerating.
Did you find this helpful?  2 of 2 Found Helpful
Good other then one part
Great parts, only had one problem with fitment with one of the Alignment insert was slightly to big only a few thousandths of a inch, took it to work had the machine shop take .030in off fit right in and no problems. Other 3 fit fine Overall great products
Did you find this helpful?  1 of 1 Found Helpful
Great Improvement
I put this stop the hop kit on my 2016 GT. I was skeptical about how much this STH kit would help keep the rear planted. Now after installing it and taking some sharp corners and doing some digs; I am a believer. The handling is matching the power. I feel more comfortable maneuvering through corners than I did before the install. I truly recommend this kit. The guys at Steeda in Pompano were a great help.
Did you find this helpful?  3 of 3 Found Helpful
Supercharger is fun again
I installed this kit on my supercharged 2015 Mustang GT with manual transmission and 3.55 gears. The car had Ford Track Handling suspension, but still had issues with the rear wheels connecting. It took away from the fun because second grade was difficult to really punch the gas. After adding this kit, I'm able to floor it in 2nd gear and just enjoy the power. Install is simple enough. Thanks, Steeda, for making my car fun again. The ONLY issue was that I didn't realize it is a bit of a wait did to the braces because everyone is ordering them and it takes a couple weeks to ship due to this. Steeda will ship the parts separately if requested though. I'm a fan of Steeda now and I view the rest of their competition as imitation. Oh, and not that it matters, but there's zero added NVH. Too bad that this kit did so much for me, I don't really need anymore parts (a common statement from me). I'll likely buy more just because it's fun to tinker.
Did you find this helpful?  5 of 5 Found Helpful
Fixes the float
When test driving my 2016 Mustang the car felt strong and handled the road nicely. I didn't really push the car hard during the test drive and the car seemed to be a lot of fun to drive. Well after purchasing the car and exploring the limits of machine and man, I realized that the body of the car felt like it was floating over the rear end. I was very unsettling and it felt like the car was over rotating. I installed the Stop The Hop Starter kit in my garage using jack stands and hand tools. It took a bit longer than expected, mostly due to the install of the lower split spacer. The one on the left side took forever to get in place. Otherwise the kit fit perfect. I suggest keeping all hardware loose until everything is installed and then torque to spec. Well the kit keeps the body centered and tied together. The floating feeling is GONE and I can feel the outer rear wheel biting into the corners during spirited driving. I have a lot more confidence in the handling of the car after installing this kit. Nice job STEEDA!
Did you find this helpful?  8 of 8 Found Helpful
subframe braces - I'm disappointed
Passenger side IRS subframe brace fit poorly. I had to trim with a grinder and also elongate holes to get brace to fit. I emailed Steeda and nobody replied
Did you find this helpful?  12 of 15 Found Helpful
I've learned over the years of modifying Mustangs, there can be modifications done that are a compromise to other aspects of the cars performance (ride quality, increased NVH, etc), or they simply don't work that well. This kit is a pure handling improvement with no downside! Lots challenging twisty two lane roads in the area I live, and after the installation of this kit I now find driving some of my favorite roads the rear end feels much more planted and confidence inspiring, with no increased NVH. I highly recommend this kit.
Did you find this helpful?  8 of 8 Found Helpful
Verified Buyer  
Stop the hop starter kit
Installed Steedas stop the hop starter kit. Start to finish took me about 3 hours, on jacks with hand tools. The rear bottom spacer..... what a b1#€h!! Definitely hardest part of the install. Everything else was straight forward and fit perfectly. No nvh, car feels great. Got the parts on Steedas BlackFriday deal. Thanks Steeda. Making great cars even better.
Did you find this helpful?  7 of 7 Found Helpful
Bullitt Owner
Best improvement for the $ modification I've done for any vehicle ever. No NVH, eliminated the squirriliness in the rear end, improved launch. No other modifications, factory magneride suspension.
Did you find this helpful?  6 of 6 Found Helpful
Verified Buyer  
Stop the hop starter kit
This kit is a must have for S550 Owners! Installed in about 2 hours, taking my time, by myself and was not that difficult. High quality, as expected from Steeda. The difference it makes in the car is amazing. The car feels more solid and planted with no increase in NVH (noise, Vibration, Harshness). Not only does it launch better from a stop, it handles more confidently through the corners. Combining with the Progressive rate springs and jacking rails from Steeda, makes a huge difference in the cars overall feel, for the better.
Did you find this helpful?  10 of 10 Found Helpful
This is the best mod for the Mustang to resolve the constant motion of the rear end. The car feels so much more secure and provides improved confidence when cornering. Takes some time to install, I had my professionally done but the difference is night and day vs factory
Did you find this helpful?  5 of 5 Found Helpful
This should have been on the car from factory
With the new Mach1 arriving in 2021 Ford should be looking to Steeda to do the suspension set up. If you only do one mod to your S550 this is the one hands down you should do. You will immediately feel the difference in handling characteristics when in a turn under power or street line. The car just wants to hold the rear end center and it just goes. It's super hard to put into words. DoRice a car without then with and you'll be like WOW. The best way to describe it is the car feels confident.
Did you find this helpful?  7 of 7 Found Helpful
Verified Buyer  
2017 mustang gt premium with 725hp
This really should be called the stiffler package, nvh is very very minimal and you won't believe it's the same car as the performance and handling is leaps and bounds above the stock setup. I highly recommend that you add the spherical bearing on the lower control arm to complete this transformation along with the steeda driveshaft for the complete package. It's hard for me to describe each individual part as I did everything at once including diff bushings.
Did you find this helpful?  4 of 5 Found Helpful
Verified Buyer  
Medium Install with Great Results!
The installation for this kit is a medium in my opinion. I would 100% recommend watching every single tutorial on YouTube before attempting this. The instructions are okay, but there's nothing like watching someone else perform the install. The ride is much tighter in the back. The wheel hop is definitely reduced. It's amazing was the kit does. I really feel like the name Starter is a misnomer, it really should be Street , because this is everything you need for Daily/Street driving to be amazing! I would definitely recommend buying this product!
Did you find this helpful?  31 of 31 Found Helpful
Verified Buyer  
Mustang Owner
I put these components on my 2015 GT PP, along with an Extreme G-Trac brace and jacking rails. I've never come close to owning a car that handles as well as this Mustang. Things that seemed suicidal to me in the past are light work for this car. What a pleasure.
Did you find this helpful?  30 of 31 Found Helpful
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