IRS Bushing kit experiences

[Burninrock24]

I am currently deciding between the Maximum Motorsports kit and the Full Tilt Boogie Racing kit (FT 5000).

https://www.maximummotorsports.com/IRS-Rear-Grip-Package-Street-1999-04-Cobra-P1345.aspx

http://fulltiltboogieracing.com/1999-2004_Cobra_Suspension_Parts_and_Tools.htm

The MM kit is a bit more expensive but as I understand it, FTBR doesn't have a front support bushing for 12mm bolts, only 14mm for the 99-04.

Anybody have any experience with any bushing kit upgrades/installs for their 1994-1998?

 

[lwarrior1016]

Honestly, just get the Delrin ftbr kit and drill the front mounting holes to 9/16”. If I can give some advice, get his entire kit with the diff shims and rear diff lowering mount and do EVERYTHING at once. I’ve had my irs down a few times for bushings and whatnot and it sucks to remove and install a bunch of times.

 

[Warhorse Racing]

I've used most of the FTBR parts on my 2004 V6 and my 2000 GT autocross cars. I chose to go with poly bushings in the rear upper and lower control arms to save some money. On my (roughly) 220 hp V6, wheel hop isn't a major issue. My 300 hp GT has more wheel hop, but not enough to hamper performance on an autocross course.

I would suggest going with the FTBR lowering rear diff mount and the improved Ford Racing diff cover. As other people will tell you, taking the IRS out to swap parts requires a lot of time and effort. It's best to improve everything all at once.

I used the standard Delrin rear diff mount on my 2000 GT; it requires some grinding of the bushing, and depending on other mods, grinding of the metal bushing housing to avoid hitting the sway bar.

These videos might help you make a decision. They cover the parts I used, some install tips, and a review of how the parts performed. The V6 in this video won a local CAM Class autocross championship in 2019. If you have any questions, please ask here or in the comments on YouTube.

 

[Burninrock24]

Honestly, just get the Delrin ftbr kit and drill the front mounting holes to 9/16”. If I can give some advice, get his entire kit with the diff shims and rear diff lowering mount and do EVERYTHING at once. I’ve had my irs down a few times for bushings and whatnot and it sucks to remove and install a bunch of times.

Yeah I'm definitely taking a buy-once-cry once approach to the swap because I dread getting my car up on jack stands. I've read a bit on the rear diff lowering mount but didn't really think I was a candidate for its use-case scenarios. What benefit did you see it give you? I'm on the fence of coilovers too while I've got it on a pallet on the floor.

I've used most of the FTBR parts on my 2004 V6 and my 2000 GT autocross cars. I chose to go with poly bushings in the rear upper and lower control arms to save some money. On my (roughly) 220 hp V6, wheel hop isn't a major issue. My 300 hp GT has more wheel hop, but not enough to hamper performance on an autocross course.

I would suggest going with the FTBR lowering rear diff mount and the improved Ford Racing diff cover. As other people will tell you, taking the IRS out to swap parts requires a lot of time and effort. It's best to improve everything all at once.

I used the standard Delrin rear diff mount on my 2000 GT; it requires some grinding of the bushing, and depending on other mods, grinding of the metal bushing housing to avoid hitting the sway bar.

These videos might help you make a decision. They cover the parts I used, some install tips, and a review of how the parts performed. The V6 in this video won a local CAM Class autocross championship in 2019. If you have any questions, please ask here or in the comments on YouTube.

I'm actually subscribed to your YouTube channel! Right now it would probably feel just fine with the stock bushings and my NPI 4.6 haha. I do plan on Coyote swapping this car next year though so I am trying to prepare the suspension for that ultimately.

 

[lwarrior1016]

Yeah I'm definitely taking a buy-once-cry once approach to the swap because I dread getting my car up on jack stands. I've read a bit on the rear diff lowering mount but didn't really think I was a candidate for its use-case scenarios. What benefit did you see it give you? I'm on the fence of coilovers too while I've got it on a pallet on the floor.



I'm actually subscribed to your YouTube channel! Right now it would probably feel just fine with the stock bushings and my NPI 4.6 haha. I do plan on Coyote swapping this car next year though so I am trying to prepare the suspension for that ultimately.

You can’t get much pinion angle out of it with a stock height rear mount. When you use the lowering mount, then you have more room to fine tune the pinion angle and get it just right.

 

[Warhorse Racing]

Thank you for subscribing! I hope the videos help. I've purchased 3 IRS assemblies over the years. When I replaced the subframe bushings, I drilled into the OEM bushings and they just crumbled, even though they looked fine. The diff bushings were also pretty torn up. Having driven stock IRS cars for students at autocross events, I can tell you there's a huge difference between an upgraded IRS and a stock one. I think your plan to build it up in preparation for more power is the right way to go.

 

[CobraEd]

I installed the complete FTBR treatment on my 03 Cobra which had MM coil overs with Bilsteins when I bought it but it still had rubber stock rubber bushings in the IRS. With the rubber bushings wheel hop was a big problem. Additionally, it had a bumpsteer problem where the rear end would kick out unexpectedly in turns that even my Prius would easily handle. Installation of the completer FTBR treatment & bumpsteering the IRS gave it precision, immediate response to steering inputs, & complete predictability. A complete transformation.

Especially since you are planning on Coyote swapping next year, I would strongly recommend that you go with FTBR Delrin kit including the bumpsteer toe links. You will benefit greatly from the precise control that Delrin & mimimizing bumpsteer offers. Note: You need to measure bumpsteer with a bumpsteer gauge, not just eyeball tie rod and control arm angles, in order to know if you have the bumpsteer curve optimized.

 

[Makoto]

the mm kit was good and doing bushings always sucks. i've done 3 cars now. 240sx, sc300, and now an irs mustang. it sudiddlyux alwaaaaaaaaaaays but the mm delrin kit is DOPE.