How far did the butt drop? From early Mk3.0 to Mk4 ?

[CNIdog]

I'm looking to mod my early MK3.0 rear end frame for a different gas tank setup and was thinking it would be a good opportunity to drop the butt.

How far did it drop? Looking at all the pics I could find, it looks close to 2.5 to 3 inches.

Anyone know for sure?

Ted

[Jim Schenck]

Ted,

If you line up the upper quickjack hole in the body with the lower hole in the frame you will be right where you want to be. Aluminum trunk walls need to be trimmed to fit and if you already have fit your doors they may now be a little short on the top at the back. Also the roll bar holes, particularly around the rear leg will move as well.

[canuck1]

Here's a pic of what Jim's talking about:

121051

This is a MKIV body on my 2005 era MK III chassis (needed to do the 'drop butt' chassis mod to make it look right). I'm pretty sure locating the rear of the body on the chassis is the same for a MK III body. The MKIV body required cutting down some of the 3/4" tubing on the trunk sides and modifying the trunk hood support, as well as aluminum trimming. Jim knows what he's talking about. I bet you'll only have to trim the aluminum trunk walls when dropping the butt on a MKIII combination. It's helpful to take photos both before and after to see where you started and if the changes you make are giving you the profile you are looking for. The body can distort in areas you hadn't anticipated. A side view photo can be really helpful in showing lines that are difficult to measure.

Sean

[CNIdog]

Thanks Sean! That makes it easy to visualize. I have a few things in mind with the aft cockpit frame behind the seats as well as a new gas tank setup. I'm discarding the old Mustang tank for a new plastic tank that fits between the bumper bolts leaving me room to add a rear exhaust muffler setup. I'm working up a bigger volume trunk frame design that will allow for a spare tire or at least some larger luggage. -Ted

[CNIdog]

Thanks Jim! I have no roll bar holes so that makes it a bit easier.

[DadofThree]

2.25" is the distance between the (2) 1/2" rear mounting holes, and will be how far I drop mine (when I get smaller rear tires). I did the modification to the frame (as you can see in this video (https://youtu.be/NjmfQKL2AhQ)), but my tires sidewalls are too tall on my rears to be able to drop the body right now. But the work is done for when I want to drop the body. I'm too have heard that the door alignment may change when you do the drop, so I'm saving my body work until I have everything in its final place. Good Luck.

[canuck1]

...I did the modification to the frame (as you can see in this video (https://youtu.be/NjmfQKL2AhQ)), but my tires sidewalls are too tall on my rears to be able to drop the body right now. But the work is done for when I want to drop the body. I'm too have heard that the door alignment may change when you do the drop, so I'm saving my body work until I have everything in its final place. Good Luck.

CNIdog,

I'm sure there are differences that make my experience different from others, but I am confident you WILL have to re-fit the doors if you carry out frame mods like DadofThree depicts. If you only need to trim the trunk side aluminum a little as Jim suggested, you may be able to compromise here and there to get the existing door alignment to work? I had to have similar frame mods done to get the MKIV body to look right on my MKIII chassis. Interestingly, you can actually drop the MKIV body on a MK III chassis as is, but it will continue to sit up in the rear, like a MK III. Doing the frame mods was required to get it to look more like a MK IV profile. This meant I had to have my doors re-fit (thankfully, while body work was still underway).

DadofThree,

Curious if your ride height is especially low? Mines about 4.5" in the rear, 4" up front and I fit 17" 315's and 15" 295's on the rear without any problem. I know my body is different from yours, but I always thought the MK III had a little more tire clearance than the MK IV?

Sean

[CNIdog]

I have possibly one of the longest drawn out builds. #4044 is one of the first MKIII into Canada when the version came out. Jumped on it earlier than I was prepared to work on it. The IRS option was going to be banned by Transport Canada so I ordered before that came down. Stored it for a few years then got working on it to the point of near go-cart, then stored it again as work and reno/flipping homes took all my time. Then we bought a place to winter in FL and it takes me away for the winter build season. Luckily, the doors aren't touched yet and I'm not using roll bars so hopefully the drop-butt operation will go easier than mods to a finished car. Locking myself in the garage when we get back to finish it before I die. ;-)

[DadofThree]

CNIdog,
DadofThree,
Curious if your ride height is especially low? Mines about 4.5" in the rear, 4" up front and I fit 17" 315's and 15" 295's on the rear without any problem. I know my body is different from yours, but I always thought the MK III had a little more tire clearance than the MK IV?
Sean

I haven't measured for a while, but I think I left my ride height in the rear around 4.5" to 5". I had tire rubber hitting the body when I first got it on the road and I did need to raise it a little. I did a comparison with John's (John4337) Cobra one day because he has the same width tire (275) on a 15" rim. Although his sidewall ratio is /50, mine is /60 and we saw a big difference in tire height. I really don't mind it because it fills up the wheel well very nicely. But when the time comes, I'll switch and drop the butt.

[GoDadGo]

How far did the butt drop?
From early Mk3.0 to Mk4?

Enough To Still Be Sexy!

.......Sorry Guys, But I Just had To!

[Gumball]

I dunno how much they dropped the rear, but get the angle of the pic right, and even the perky-butt Mk3 (this is a late 3.1 version) can look downright sexy.......

[canuck1]

Ted,,

I remember talking to you about your build on the other forum back in'05. The IRS option is nice. I guess 275/60 is quite tall (over 28 inches overall diameter). My 295/50's are less than 27 inches overall diameter.

Sean

[CNIdog]

Long time and 4 house renovations since then! If I could have waited, I could have bought a finished Roadster down here in FL. Oh well, the fun is in the building. I'm sure it's going on the road this summer. I'm using 245/45-17's F&R for mine, with a 1.25" spacer to clear the A-arms up front and the shocks I've moved outboard in the rear. I know guys who have done two already and moved on to other stuff. I remember some of the characters on the old forum "Meat" and "Rocket Scientist" I actually met with him in Colorado back then. Interesting story. Sad ending. :-)