Steeda Mustang 'Stop The Hop' Handling Ultimate Kit (2015-2021)

3 Review(s)
$52.00 (5%)
Steeda's easy to install S550 Ford Mustang "Stop the Hop Handling Ultimate Kit" eliminates wheel hop, squares the subframe to the chassis, & will give your more control so you can take corners faster.

Part Number: 555 2129 H
Write a Review

Suggested Mods


Our Sales Experts take calls all the time from enthusiasts that want to eliminate wheel hop and improve the handling of their Mustang. This is where the Stop the Hop Handling Ultimate Kit comes in. Our team of engineers got together and came up with the best parts for eliminating unwanted wheel hop and bushing deflection in the new S550 Mustang to help you take corners faster and get tack sharp handling. 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.

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 its kind in the performance aftermarket and so innovative and popular we patented its 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. Its job is to prevent up and down movements of the subframe.

The 3rd component of 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.

Steeda's Rear Toe Links are the 4th item in the kit. They help you improve your launch and allows you to control the toe of your Mustang during launches. Improve your 60-foot times and get down track faster with this upgrade from Steeda. 

5th in the kit, the Steeda Billet Vertical Links with Urethane Bushings reduce deflection and tighten the rear of your S550. This CNC machined 6061 billet aluminum piece is a great step up over the stamped factory piece. Reducing bushing deflection will help you put more power to the ground and improve control, while also preventing unwanted movement and wheel hop. Bushing deflection from the stock rubber bushings can cause sloppy or soft handling and will hold your Ford back from reaching its full potential. 

The 6th piece is Steeda's Adjustable Differential Bushing Insert System. These polyurethane bushings replace the soft rubber factory bushings that result in pinion changes, differential movement, and wheel hop. This will improve handling by helping to keep the rear of your S550 connected. You can expect some increase in NVH and may experience increased transfer of gear whine noise problematic to some Super 8.8 IRS differentials.  

NOTE: Steeda IRS Subframe support braces will not fit convertible. Due to changes in the OE subframe bushings, the bushing inserts will not fit 2021 GT500's or 2022 Mustang's.

Kit Includes:

  • 555-5754 - Steeda IRS Subframe Support Braces
  • 555-4443 - Steeda Adjustable Differential Bushing Insert System
  • 555-4438 - Steeda IRS Subframe Alignment Kit
  • 555-4437 - Steeda IRS Subframe Bushing Support System
  • 555-4129 - Steeda Billet Aluminum Vertical Links with Urethane Bushings
  • 555-4120 - Steeda Adjustable Rear Toe Links

Product Benefits:

  • Eliminate wheel hop 
  • May increase NVH (gear noise)
  • Eliminate subframe movement
  • Minimizes differential movement
  • Simple install
  • Squares subframe to the chassis
  • No permanent modifications
  • More predictable handling
  • Greater control and stability

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

CA Residents: Cancer and Reproductive Harm WARNING

Fitment & Features


Manufacturer: Steeda Autosports
Made in USA: Yes

Installation Information:

Level of Difficulty: Tech Recommended
Install Time: About 6 Hours
Tools Required: Basic Shop Tools

Vehicle Fitment:

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

Customer Reviews

Rating Snapshot

Select a row below to filter reviews.

Average Customer Ratings


2021 Mustang GT Premium
Another big WOW for Steeda! This takes all of the "squirm" out of the IRS - and dials in traction and enhanced handling! All shifts 1-2 bring about their respective amounts of wheelspin, with NO wheel hop! I did notice a *slight* gear whine (highway speeds, no radio, windows up), but it is also to be expected based on the product description - it is MINIMAL! Handling, when combined with the G-trac Brace and Strut Tower brace, is insanely better, even with the stock (non-PP) suspension! No more tramlining from the front end, it just goes where it is pointed, with no drama whatsoever. Taking this all to the track in 2023!
Did you find this helpful?  1 of 1 Found Helpful
Reading is fundamental
This review is in response to another reviewer that may not have understood the product description, but also to leave my own personal review of this product. From the description - "You can expect some increase in NVH and may experience increased transfer of gear whine noise problematic to some Super 8.8 IRS differentials. " For the other reviewer, NVH means "Noise, Vibration, and Harshness" ie: more noise from the diff... I understand if that extra gear whine bugs some people, and that's fine, but before leaving a review stating that the company should have included that in their description of the product, perhaps you should actually read the product description; don't you think? As for my own review, I could not be any happier with this kit. My 21 GT PP1 feels like it's anchored to the tarmac when I launch now. I haven't had an opportunity to go to the track with it yet, but I'll be back out there in the Spring! A+ job Steeda!
Did you find this helpful?  12 of 12 Found Helpful
Roush RS3
I bought this kit & everything worked out well I ended up removing (Differential Bushing Insert System - Urethane) & going back stock. Added a lot of gear noise. Steeda should state that..
Did you find this helpful?  0 of 14 Found Helpful
There are no reviews for this product!

Related Items

123123 - 1
Back to TOP
0 Items