Taimar rear suspension weight vs Jag IRS
Discussion
Some while back I was thinking of using an IRS setup in my Taimar to be sure to handle the 302 up front. I backed off that and went with a Turbo spec rear end as the output I plan for my 302 is similar to the Essex Turbo.
At the time, one reason I was given not to go for the IRS was that the received wisdom was that it's weight was significantly greater. At the time I didn't have all the parts to hand to compare them, as my IRS was still in it's Jaguar cage.
I just snuck the bathroom scales out to the garage and weighed the key components (I presumed springs and shocks would be the same, and brake pads were insignificant).
The data surprised me, so I thought I would share in case anyone was curious. These are for one side only.
I added the ARB to the IRS weight as I see kit car IRS typically uses a 45deg triangulation to the chassis forward of the diff.
I am sure there might be some additional wrinkles to consider, but the overall weight of what I believe the key components to be is remarkably similar.
In addition, I think the unsprung IRS weight is a fair degree less than the Taimar standard setup.
Discuss / Flame On / etc
cheers
Nick
At the time, one reason I was given not to go for the IRS was that the received wisdom was that it's weight was significantly greater. At the time I didn't have all the parts to hand to compare them, as my IRS was still in it's Jaguar cage.
I just snuck the bathroom scales out to the garage and weighed the key components (I presumed springs and shocks would be the same, and brake pads were insignificant).
The data surprised me, so I thought I would share in case anyone was curious. These are for one side only.
TVR IRS
Hub 5.9kg Hub + Driveshaft 8.0kg (didn't take them apart)
Driveshaft 10.7kg
Drum +cylinder 4.8kg Disc+caliper 8.5kg
Wishbones 6.0kg Wishbone 7.3kg
TVR Front ARB 2.9kg (guestimate for IRS triangulation rod)
------- -------
27.4kg 26.7kg
I added the ARB to the IRS weight as I see kit car IRS typically uses a 45deg triangulation to the chassis forward of the diff.
I am sure there might be some additional wrinkles to consider, but the overall weight of what I believe the key components to be is remarkably similar.
In addition, I think the unsprung IRS weight is a fair degree less than the Taimar standard setup.
Discuss / Flame On / etc
cheers
Nick
I'm using a 3.07 LSD with the Turbo setup so I'd worked on a net zero difference.
I did omit to include the fulcrum shafts and mount, and all the TVR bolts and stuff, but I suspect that's a 1-2kg variance between the two setups. My surprise was how similar the two setups were, rather than the x2 factor I was somehow expecting the IRS to be.
The suspension components seem to be ~50% of the back end bolt-on weight, with the LSD being iirc 50-60kg ballpark (I'll try to weigh it when it comes back from it's refurbishment and adjustments, and add the data here)
cheers
Nick
I did omit to include the fulcrum shafts and mount, and all the TVR bolts and stuff, but I suspect that's a 1-2kg variance between the two setups. My surprise was how similar the two setups were, rather than the x2 factor I was somehow expecting the IRS to be.
The suspension components seem to be ~50% of the back end bolt-on weight, with the LSD being iirc 50-60kg ballpark (I'll try to weigh it when it comes back from it's refurbishment and adjustments, and add the data here)
cheers
Nick
The 307 will dull the performance out of the blocks.. 3.54 probably best but a 3.31 will be in the middle.
On short tracks I am finding that my 3.31 is still a little tall but this is with a V8 and a C/R Super T10 box, your ratios in the gearbox may make the differences less apparent.
N.
On short tracks I am finding that my 3.31 is still a little tall but this is with a V8 and a C/R Super T10 box, your ratios in the gearbox may make the differences less apparent.
N.
It depends on the comparison point and ultimate use case, but I agree with you
When I was deciding on what diff ratio to go for, I was incorporating two different inputs.
a/ Mustang daily drive. My '88 Mustang had a 2.73:1 back end, which with T5 O/D of 0.68 was great for distance driving. T5 1st gear is 3.35:1 and performance was decent enough so moving that engine and gearbox to a Taimar weighing only 65% of the old car would give performance boost. I added in a slight ratio change in the axle as well, but I didn't want to lose all of the top end cruising capability.
b/ 5000M hill climb toy. Electron's 5000M has, from memory, a 3.54:1 plus 302 and T5 (not sure of ratios), and I found it lit up it's tyres at the slightest opportunity off the line. He found the same, and experimented with starting in 2nd at Gurston. I felt, for the car/engine/gearbox combination, that 3.54.1 was too much.
If I'd have seen a 3.31:1 I might have gone that route, but the 3.07:1 came up for a good price so that's what I went with.
cheers
Nick
When I was deciding on what diff ratio to go for, I was incorporating two different inputs.
a/ Mustang daily drive. My '88 Mustang had a 2.73:1 back end, which with T5 O/D of 0.68 was great for distance driving. T5 1st gear is 3.35:1 and performance was decent enough so moving that engine and gearbox to a Taimar weighing only 65% of the old car would give performance boost. I added in a slight ratio change in the axle as well, but I didn't want to lose all of the top end cruising capability.
b/ 5000M hill climb toy. Electron's 5000M has, from memory, a 3.54:1 plus 302 and T5 (not sure of ratios), and I found it lit up it's tyres at the slightest opportunity off the line. He found the same, and experimented with starting in 2nd at Gurston. I felt, for the car/engine/gearbox combination, that 3.54.1 was too much.
If I'd have seen a 3.31:1 I might have gone that route, but the 3.07:1 came up for a good price so that's what I went with.
cheers
Nick
status said:
It depends on the comparison point and ultimate use case, but I agree with you
When I was deciding on what diff ratio to go for, I was incorporating two different inputs.
a/ Mustang daily drive. My '88 Mustang had a 2.73:1 back end, which with T5 O/D of 0.68 was great for distance driving. T5 1st gear is 3.35:1 and performance was decent enough so moving that engine and gearbox to a Taimar weighing only 65% of the old car would give performance boost. I added in a slight ratio change in the axle as well, but I didn't want to lose all of the top end cruising capability.
b/ 5000M hill climb toy. Electron's 5000M has, from memory, a 3.54:1 plus 302 and T5 (not sure of ratios), and I found it lit up it's tyres at the slightest opportunity off the line. He found the same, and experimented with starting in 2nd at Gurston. I felt, for the car/engine/gearbox combination, that 3.54.1 was too much.
If I'd have seen a 3.31:1 I might have gone that route, but the 3.07:1 came up for a good price so that's what I went with.
cheers
Nick
The original griff was a 3.07. I have a 3.31 which for a road car would be perfect. I am finding that I am getting frustrated waiting for her to find her legs out of tight hairpins and I am only just getting into top after the pit exit on crofts main straight..This is with a 4 sp so If you have a 5 sp then I would definitely be changing to a 3.31..When I was deciding on what diff ratio to go for, I was incorporating two different inputs.
a/ Mustang daily drive. My '88 Mustang had a 2.73:1 back end, which with T5 O/D of 0.68 was great for distance driving. T5 1st gear is 3.35:1 and performance was decent enough so moving that engine and gearbox to a Taimar weighing only 65% of the old car would give performance boost. I added in a slight ratio change in the axle as well, but I didn't want to lose all of the top end cruising capability.
b/ 5000M hill climb toy. Electron's 5000M has, from memory, a 3.54:1 plus 302 and T5 (not sure of ratios), and I found it lit up it's tyres at the slightest opportunity off the line. He found the same, and experimented with starting in 2nd at Gurston. I felt, for the car/engine/gearbox combination, that 3.54.1 was too much.
If I'd have seen a 3.31:1 I might have gone that route, but the 3.07:1 came up for a good price so that's what I went with.
cheers
Nick
I know other people who are currently building Road going 400hp M series cars who have done some calcs and they have come to the conclusion that a 3.54 gives best all round in gear performance, 3.31 slightly dulled but longer legged and a 3.07 will be frustrating unless you are building a car for an outright speed record at Bonneville.
I am assuming you are using a european spec T5 rather than a Mustang T5, hence the lower first gear.
N
Dollyman1850 said:
I am assuming you are using a european spec T5 rather than a Mustang T5, hence the lower first gear.
N
No, this is both engine and gearbox being lifted straight from my '88 5.0 Mustang. Ford changed the Mustang 5.0 1st gear in around 1985, from 2.95 to 3.31. N
cheers
Nick
My M run with a 3.0 V6 and Getrag 5 speed (4.23-2.52-1.665-1.22-1.00) and a 2.93 BMW LSD. Rear tyres 265/40-16.
Before did I use a 3.15 diff, but 1'th was way too low to get any traction on the line. With the 2.93 (total ratio 12.4) do it launch better, and 1'th goes to 50 mph in 1'th @8100 rpm. 2'nd bites perfect and run's to 80 mph.
So launcing is perfect, only problem is that I miss a gear between 2'nd and 3'th, narrow corners/roundabouts etc. is fine in 2'nd, but on open corners then 3'th to be too high and 2'nd too low. Eg. a 60 mph corner is 6100 in 2'nd and 4000 in 3'th. But this problem seems to be the same in all street box'es, that often spread +400% from 1'th to 5'th. The getrag box drops 40%-34%-27%-18% between the gears, total drop 423% 1'th/5'th
So a close ratio 5 speed to get a high ratio 1'th and close 2-3-4 and then an overdrive 5'th would be perfect. It seems that the T5 can be build with that kind of setup.
And torque based LSD, is super (but keep both hands on the wheel)
btw, weight on the M3 188mm LSD is 45 kg, the 210mm LSD (M3-3.2 and M5) is 52kg
Before did I use a 3.15 diff, but 1'th was way too low to get any traction on the line. With the 2.93 (total ratio 12.4) do it launch better, and 1'th goes to 50 mph in 1'th @8100 rpm. 2'nd bites perfect and run's to 80 mph.
So launcing is perfect, only problem is that I miss a gear between 2'nd and 3'th, narrow corners/roundabouts etc. is fine in 2'nd, but on open corners then 3'th to be too high and 2'nd too low. Eg. a 60 mph corner is 6100 in 2'nd and 4000 in 3'th. But this problem seems to be the same in all street box'es, that often spread +400% from 1'th to 5'th. The getrag box drops 40%-34%-27%-18% between the gears, total drop 423% 1'th/5'th
So a close ratio 5 speed to get a high ratio 1'th and close 2-3-4 and then an overdrive 5'th would be perfect. It seems that the T5 can be build with that kind of setup.
And torque based LSD, is super (but keep both hands on the wheel)
btw, weight on the M3 188mm LSD is 45 kg, the 210mm LSD (M3-3.2 and M5) is 52kg
Edited by madsvlund on Sunday 8th March 18:48
Dollyman1850 said:
status said:
It depends on the comparison point and ultimate use case, but I agree with you
When I was deciding on what diff ratio to go for, I was incorporating two different inputs.
a/ Mustang daily drive. My '88 Mustang had a 2.73:1 back end, which with T5 O/D of 0.68 was great for distance driving. T5 1st gear is 3.35:1 and performance was decent enough so moving that engine and gearbox to a Taimar weighing only 65% of the old car would give performance boost. I added in a slight ratio change in the axle as well, but I didn't want to lose all of the top end cruising capability.
b/ 5000M hill climb toy. Electron's 5000M has, from memory, a 3.54:1 plus 302 and T5 (not sure of ratios), and I found it lit up it's tyres at the slightest opportunity off the line. He found the same, and experimented with starting in 2nd at Gurston. I felt, for the car/engine/gearbox combination, that 3.54.1 was too much.
If I'd have seen a 3.31:1 I might have gone that route, but the 3.07:1 came up for a good price so that's what I went with.
cheers
Nick
The original griff was a 3.07. I have a 3.31 which for a road car would be perfect. I am finding that I am getting frustrated waiting for her to find her legs out of tight hairpins and I am only just getting into top after the pit exit on crofts main straight..This is with a 4 sp so If you have a 5 sp then I would definitely be changing to a 3.31..When I was deciding on what diff ratio to go for, I was incorporating two different inputs.
a/ Mustang daily drive. My '88 Mustang had a 2.73:1 back end, which with T5 O/D of 0.68 was great for distance driving. T5 1st gear is 3.35:1 and performance was decent enough so moving that engine and gearbox to a Taimar weighing only 65% of the old car would give performance boost. I added in a slight ratio change in the axle as well, but I didn't want to lose all of the top end cruising capability.
b/ 5000M hill climb toy. Electron's 5000M has, from memory, a 3.54:1 plus 302 and T5 (not sure of ratios), and I found it lit up it's tyres at the slightest opportunity off the line. He found the same, and experimented with starting in 2nd at Gurston. I felt, for the car/engine/gearbox combination, that 3.54.1 was too much.
If I'd have seen a 3.31:1 I might have gone that route, but the 3.07:1 came up for a good price so that's what I went with.
cheers
Nick
I know other people who are currently building Road going 400hp M series cars who have done some calcs and they have come to the conclusion that a 3.54 gives best all round in gear performance, 3.31 slightly dulled but longer legged and a 3.07 will be frustrating unless you are building a car for an outright speed record at Bonneville.
I am assuming you are using a european spec T5 rather than a Mustang T5, hence the lower first gear.
N
What flywheel are you using?
Best regards,
Bernard.
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