TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Independant rear suspension (IRS) for TR7V8
Hello everyone,
I'm in the process of researching turning my TR7 into a TR7V8 and as part of the project I've decided on converting to IRS. I've read a few articles here and there and then came to this amazing forum and saw IRSs in MG and a really cool Standard. Can anyone elaborate or point me in the direction of a TR7V8/TR8 build details or "How-to"? Can anyone share any insight and specifics like which IRS units, cradle measurements and axle shaft lenghts, etc? Thank you for anything you may share with me. Trip Edited 2 time(s). Last edit at 08/20/2009 04:12PM by TRip. |
Moderator Curtis Jacobson Portland Oregon (4577 posts) Registered: 10/12/2007 02:16AM Main British Car: 71 MGBGT, Buick 215 |
Re: Independant rear suspension (IRS) for TR7V8
Welcome to the forum! Sounds like you'll fit in perfectly here.
I don't know much about IRS, so I'll leave that for someone else. (Jim?) I'm kinda curious though... what are you hoping to accomplish with IRS? Do you want IRS because it's a really cool fabrication project and a chance to learn a lot about vehicle dynamics? Or are you mainly interested in ride quality? Or maybe you're building this car for scrambling over boulders? Most of the projects around here aren't all that "practical". Nothing wrong with that! But it might help if we knew more about your vision for what you want to have when you're all done. Also, you might want to post your question in the suspension/handling forum section to reach a broader cross-section of people. |
TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Re: Independant rear suspension (IRS) for TR7V8
Hello Curtis, thank you for welcoming me.
I really do have a feeling that I'll fit right in here! IRS for all the reasons you mentioned except "scrambling over boulders". I know it's not practical especially when a moded LSD solid axle will "work". But, I happen to think practical = Boring! It's a challenge, it's a chance to learn new things, skills, communicate with like minded enthusiasts and it's different from most TR7/8s. I also would like to install a Rover V8 with 300hp (maybe not so reasonable goal) and have a rear end that'll hold up and add to the performance at the same time. I'm just now starting out and in the research phase. It'll be some time till knowledge and savings meet, though. LOL BTW: The suspension dynamics angle (no pun intended) is also fascinating... And, from what I've seen here, the folks on this forum are fantastically knowledgeable and insightful. Thanks for the suspension/handling forum posting suggestion. I don't know how to transfer over though(?) Thanks for the welcome, Curtis. Trip |
BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6470 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Independant rear suspension (IRS) for TR7V8
Trip, welcome. I don't know what's been done with the TR, but maybe Dan B. has seen something. He's a dyed in the wool TR guy and lots of TR's were IRS so he might have seen something that would help you get started. He's also anticipating an engine swap when his TR7 needs it, so we've been looking at engine choices. I just bought Edith a TR7 with a Buick V6. Lots of potential there but I'd look real close at the 2010 Camaro driveline. 3.6L V6 with direct injection and active cam timing control on intake and exhaust independently (dohc) on a 60* engine with about 305hp and over 30mpg. Lots to like about that one.
The Jag is probably overkill a little bit. But we have a couple of threads on IRS conversions. Spend a little time wandering through the old posts. There's lots of good comparison info there. Jim |
Dan B Dan Blackwood South Charleston, WV (1007 posts) Registered: 11/06/2007 01:55PM Main British Car: 1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl |
Re: Independant rear suspension (IRS) for TR7V8
An X type might be worth looking at.
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WedgeWorks1 Mike Perkins Ellicott City, Maryland (460 posts) Registered: 07/06/2008 08:07AM Main British Car: 1980 Triumph TR8 3.5 Litre Rover V8 |
Re: Independant rear suspension (IRS) for TR7V8
Trip-
The TR7 body is really not set up for IRS. The frame rails would need a lot of work moving them inward and possibly removal to for an IRS unit. You would also have to get the IRS load back to the floors since originally designed the four link suspension put all the stress into the floors and rear bulk head. with just springs and shocks connecting to the rear rails. In my opinion it is way too much work and expense. It is so much easier to get a Ford or a Dana LSD rear axle and have it shortend and the original mounting brakets welded on and be a bolt in. If you plan on 300+ horse those rear ends will easily handle that power and more with a huge range of gears to choose from. Be sure to reinforce the control arm mounting areas on the outside and inside of the car. They cannot handle a lot of torque and will eventually tear apart. Good luck! |
TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Re: Independent rear suspension (IRS) for TR7V8
Thank you Jim.... Isn't a Buick V6 basically a 3500 minus 2 cylinders? I hear it's super strong too!
The 2010 Camaro driveline is really nice. Wouldn't it cost far more than piecing together good rebuilt Rover bits, though(??) Plus, there really is something to be said for that V8 rumble. Dan, I'll check out what I can on X types. Thanks Mike, You've made very strong points regarding "frame rails" and getting "the IRS load back to the floors since originally designed the four link suspension". I wonder if a carrier can be fabricated to tie everything together and address the frame rail and load issues? I'm very glad to have insights from all of you. Trip Edited 1 time(s). Last edit at 08/22/2009 02:18AM by TRip. |
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WedgeWorks1 Mike Perkins Ellicott City, Maryland (460 posts) Registered: 07/06/2008 08:07AM Main British Car: 1980 Triumph TR8 3.5 Litre Rover V8 |
Re: Independant rear suspension (IRS) for TR7V8
Trip-
You would need to consider the dimensions of the IRS assembly, wheel travel & angles and from there how much rear frame rail and inner wheel arch modifications will be required. You could bring braces to the floors to get the stresses back up front. It still seems like a ton of work....... |
BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6470 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Independant rear suspension (IRS) for TR7V8
Trip, check out what we did on the MGB-Roadmaster thread and the 340 upgrade thread in the MG forum. Also look at Calvin's work on upgrading his TR6 to a hybrid Nissan/TR IRS. We modified a Jag IRS to bolt into the regular MGB solid axle mount points with no modifications to the body. I would assume a similar approach should work for the TR7, although Mike is right, any stiffening you would need for a solid axle would also probably be needed for the IRS for a given power level.
Jim |
TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Re: Independant rear suspension (IRS) for TR7V8
Thank you Mike and Jim.
It's really very nice to have honest and straight insights. It's grounding and keeps me from unrealistic goals. Although this IRS idea is now becoming a little daunting. I'm still enthusiastic about it as a learning project. Jim, I'll search for the projects you mentioned. Thanks again for your knowledge. Trip |
turbospitfire Max Brewster (49 posts) Registered: 04/25/2008 01:05PM Main British Car: 1979 Triumph Spitfire Ford 2.3 Liter Turbo |
Re: Independant rear suspension (IRS) for TR7V8
You might consider an early '89 - '97 Mercury Cougar & Ford T-Bird IRS. The Monster Miata conversion kits use this setup. One advantage is that they are cheap at a junk yard and offer a variety of gear ratios. You may have to deal with narrowing the axles. I found that if you can find a CV joint re-builder they may find shorter axles with same spline. This avoids welding axles. See below for an example of what it looks like in a fabricated frame.
[www.factoryfive.com] Cheers, Max Brewster 1979 Triumph Spitfire 2.3 Ford Turbo |
TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Re: Independant rear suspension (IRS) for TR7V8
Thank you for the lead, Max,
I'll check out your link. BTW, wouldn't the control arms have to be shortened too and new geometry calculated for the TR7? Cheers, Trip Edited 1 time(s). Last edit at 09/02/2009 10:51PM by TRip. |
Dan B Dan Blackwood South Charleston, WV (1007 posts) Registered: 11/06/2007 01:55PM Main British Car: 1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl |
Re: Independant rear suspension (IRS) for TR7V8
Hey Trip,
I just ran across this on the TriumphTr7.com forum: [www.triumphroverspares.com.au] Obviously it is being done in Australia. Dan |
TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Re: Independant rear suspension (IRS) for TR7V8
Hello Dan,
I emailed them. Phil at TRS replied by saying that they are no longer available. I think their price was really high when they were selling it. I recall around $5500. Thank you for the lead. Trip |
turbospitfire Max Brewster (49 posts) Registered: 04/25/2008 01:05PM Main British Car: 1979 Triumph Spitfire Ford 2.3 Liter Turbo |
Re: Independant rear suspension (IRS) for TR7V8
Hi Trip, yes all the suspension needs reworking. I went through this with my conversion since I removed the transverse leaf and built an unequal a-arm coil over suspension. It was challenging. One more option would be the rear suspension subframe, including control arms, hubs etc, from a second generation RX7. It may be close in width to the TR7. However, I would not use the RX7 differential because you are limited in available gear ratios. Monster Miata sells a kit to use the T-bird differential and they provide axles and wheel flanges. It may cost more but it is another possibility.
Cheers, Max |
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turbospitfire Max Brewster (49 posts) Registered: 04/25/2008 01:05PM Main British Car: 1979 Triumph Spitfire Ford 2.3 Liter Turbo |
Re: Independant rear suspension (IRS) for TR7V8
Trip, I should clarify. You may have to call Monster Miata to see if they would sell the parts separately for the differential swap.
Max |
TRip Trip Anthony (162 posts) Registered: 08/18/2009 01:16AM Main British Car: 1980 TR7 performance 4 cyl |
Re: Independant rear suspension (IRS) for TR7V8
Hi Max.
RE: your conversion - "It was challenging". I can see how it would have been a challenge. The cool part is that you overcame the issues. RX7... that's an interesting option. I'll take a look at the Miata kit and also look into some sort of swap possibility. Thanks Max, Trip Edited 1 time(s). Last edit at 09/04/2009 03:01PM by TRip. |
Re: Independant rear suspension (IRS) for TR7V8
I grabbed an independent 8.8 out of a Thunderbird, and also grabbed an aluminum case from a Lincoln. Some day I will shorten the axles and build a carrier to put it in my LS3 powered TR8. For now the stick 8.8 from an Explorer will have to do. The Thunderbird 8.8 is the way to go. It has carriers that point the control arms 90* straight back at the center section. Makes fabrication easy. Thats why its the rear end of choice for the Miata V8 conversions, and for Cobra kit cars. There is so much demand for these units, that Ford Motorsports has begun making and selling just the carriers again. You can snag an independent center section from an 98 onward Explorer, or later Lincolns, and then fabricate the control arms, axles, and carrier. I messed around with the independent that came in my donor 2010 Camaro SS. Proved unusable. Minimum wheel size would have been 18" to clear the carrier, and the control arms pointed at weird angles. Supposedly those angles and control arm lengths were decided on by a computer modeling program to minimize castor camber changes during wheel travel. Not at all duplicatable in a small Brit sports car. Shame really, because it was a very nice unit. Center section was aluminum and had a limited slip from the factory. Sold it for more than I paid for the Thunderbid unit and its rebuild parts, so I guess I made out.
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Dan B Dan Blackwood South Charleston, WV (1007 posts) Registered: 11/06/2007 01:55PM Main British Car: 1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl |
Re: Independant rear suspension (IRS) for TR7V8
I saw some information on another board a few years ago about using a Merkur or Scorpion IRS. It sounded promising, except they are rare.
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