Wedge TR7 Jag IRS conversion

[TR7/8 TPI]

Just an update for those who are curious.

The Jag IRS sub frame is going together quite well. All the measurements look really good. I will have plenty of clearance for the gas tank and the exhaust will have plenty of room to go through the sub frame and above the stub axles. Also the brake pads will be easy to change. I could'nt have planned it any better, even if I had planned it! heh

If you wanna see latest pics of progress, check my site.

 

[Mark Beiser]

Man, just thinking about how much sprung weight that adds makes me cringe, lol.

But again, with the lump your putting in the front, it should ballance out nicely, and the IRS should be a fantastic thing to have.

Hopefully you won't have to go through to many different sets of springs before you find what works best, looks like more "fun" than I want to get involved with though.

Can't hardly wait to see the finished product.

 

[tony barnhill]

WOW! Quite a projsct...but, I'm with Mark: how much overaall weight you adding to the little car? Are you changing the front-to-rear weight distribution ratio?

 

[TR7/8 TPI]

I know the original Jag IRS assembly weighs about 300lbs. The sub frame i'm building will add about 40lbs to that. I'm thinking the original TR diff, hardware, springs and shocks had to of been about 200-250lbs so overall added weight to the rear will be about 100-150lbs.

As for the front, the V8 with turbos should add roughly an extra 200lbs or so. The front/rear weight ratio should be close.

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by tony barnhill:
WOW! Quite a projsct...but, I'm with Mark: how much overaall weight you adding to the little car? Are you changing the front-to-rear weight distribution ratio?<hr></blockquote>

 

[tony barnhill]

&, with the added power over a TR8 engine (had you opted that conversion), you should have a real scooter there! I marked your site to revisit from time-to-time to see how you're progressing...

 

[Mark Beiser]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by TR7/8 TPI:
I know the original Jag IRS assembly weighs about 300lbs. The sub frame i'm building will add about 40lbs to that. I'm thinking the original TR diff, hardware, springs and shocks had to of been about 200-250lbs so overall added weight to the rear will be about 100-150lbs.

As for the front, the V8 with turbos should add roughly an extra 200lbs or so. The front/rear weight ratio should be close.

<hr></blockquote>


The thing to remember though is that the entire wight of the origonal rear end was unsprung wight. You may be adding only 100-150 lbs of rolling wight with the Jag IRS, but you are adding more than 300lbs of sprung weight.

Again, thats probably fine for your application since you are adding a good chunk of wight to the front end, so it will maintain decent weight distribution.

I'm curious though, have you considdered going to power steering? That car will be pushing 3000 lbs when your finished with it, you may find the steering really heavy with the stock TR7 rack.

 

[TR7/8 TPI]

Mark

I put a 305HO V8 in my TR7 in high school and the steering was great except when parking where it would get a bit heavy. On this one though, I am going to be putting in a power rack. I have purchased a used rack from a Miata that looks like it should work well.

As for sprung weight, I am totally ok with that. What this will do is reduce un-sprung weight(weight out at the wheel), especially because of the inboard brakes. The weight of the suspension that is out at the wheel will be considerably less than the original differential.


<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Mark Beiser:



The thing to remember though is that the entire wight of the origonal rear end was unsprung wight. You may be adding only 100-150 lbs of rolling wight with the Jag IRS, but you are adding more than 300lbs of sprung weight.

Again, thats probably fine for your application since you are adding a good chunk of wight to the front end, so it will maintain decent weight distribution.

I'm curious though, have you considdered going to power steering? That car will be pushing 3000 lbs when your finished with it, you may find the steering really heavy with the stock TR7 rack.<hr></blockquote>

 

[tony barnhill]

Think we're getting 'sprung' & 'unsprung' weight mixed up...& its 'unsprung' weight that you want to keep to minimum first & then 'sprung' weight....anything below/outside the springs is 'unsprung'...anything above the springs or that's attached to body is 'sprung'...Mark's correct: you're adding lots of 'sprung' weight (i.e., the brakes that were originally 'unsprung' become 'sprung' with your Jag setup)

 

[Mark Beiser]

Hey, on the bright side, you pulled a little over 30 lbs of sound deadening material out and replaced it with maybe 5 lbs of Dynamat, so you saved some weight there!

 

[78Z]

very impressive!