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Suspension Modifications
What to do about coilovers?
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<blockquote data-quote="Bingo13" data-source="post: 14489247" data-attributes="member: 4923"><p>Wheel Rates for the '03~'04 Cobra with IRS -</p><p>Front:</p><p>The front wheel rate is 25% of the stock location spring's rate. For example, the 600lb/in stock location spring has a wheel rate of 150 lb/in. For a coil-over suspension, the wheel rate is approximately 90% of the coil-over spring's rate. Therefore, a front coil-over spring rated at 375 lb/in would result in a wheel rate of about 337.5 lb/in. Your wheel rate will increase by 225%. </p><p></p><p>Rear:</p><p>The wheel rate for the rear of our Cobra with IRS is approximately 33% of the spring rate in the stock location. For example, the 600 lb/in stock location spring has a wheel rate of 198 lb/in. For a coil-over suspension, the wheel rate is approximately 50% of the coil-over spring rate so a matching 575 lb/in would result in a wheel rate of about 287.5 lb/in. Your wheel rate will increase by 145%.</p><p></p><p>As for the OP question about rates and what to do. I have been using coilovers on this platform since 2002. The archives have a significant amount of information on what a lot of us went through after the car came out and we started open tracking or autocrossing the car. Just a recap based on what I have discovered over the years.</p><p></p><p>Street Setup - Firm yet very good for daily driving, light to medium HPDE/AutoX events and hooks well for spirited starts. Items 1 to 6 are required, the balance are highly recommended (pick and choose based on component age) to get this platform corrected.</p><p>1. Full Length Subframe connectors - MM XL, Global West, KB, Griggs, Stifflers. I would actually do the Global West COMP, KB Extreme Matrix or Stifflers FIT system if you do not have FLSC installed already. </p><p>2. MM 4-point K-Member Brace (much more important than the upper strut tower brace) </p><p>3. MM CC Plates</p><p>4. MM Sport Dampers (do not re-valve to be honest, start with a set designed for coilovers)</p><p>5. MM 375/575 Coilover spring kit (this is a perfect compromise for what you want)</p><p>6. FTBR FT5001 IRS Kit (this will transform the handling of your car more than you can believe)</p><p>7. FTBR FT1350M Differential Housing (do it now if you plan on any racing activities)</p><p>8. FTBR M4204T31H Torsen T2-R Differential Unit (do it now if you plan on any racing activities)</p><p>9. FTBR FT1860 Toe Link Kit </p><p>10. FTBR FT1900 Rear Sway Bar End Link Kit</p><p>11. MM non-offset front control arms with Urethane - MMFCA-7</p><p>12. MM front tapered bumpsteer kit - MMTR-4</p><p>13. MM steering shaft assembly mmst-14</p><p>14. MM solid steering rack bushings -MMST-7</p><p>15. Upgraded front sway bar endlinks</p><p>16. Upgraded urethane front and rear swaybar bushings</p><p>17. Check and replace front inner tie rods, hub assemblies, bearings, etc while the front end is apart.</p><p>18. Check and replace the rear hub assemblies, halfshafts, boots, etc. Based on mileage I found it much easier and cheaper to replace the entire rear knuckle assembly (FTBR FT6800P) with the IRS out. The halfshafts were fine but needed new boots and do not forget new IRS halfshaft retaining nuts, front hub nuts, and IRS camber adjusting bolt plus low profile IRS subframe bolts.</p><p>19. While everything is out I would install front/rear SS brake lines. </p><p>20. Mathis Bracket, KB Rear Shock Tower brace with additional seam welding on the shock towers, and a MM or KB front strut tower brace would round it out. </p><p>21. Upgrade the braking system, FTBR FT9490HD and FT7000A kits plus appropriate pads, front duct cooling and fluids. At the minimum I would do the M-2300-X Cobra R front system and FT7000A rear. But if you get serious do not waste your money on the Cobra R and just go straight to the FTBR FT9490HD fronts.</p><p></p><p></p><p></p><p>Balanced HPDE/AutoX Setup - Very firm yet streetable for the most part, but beware potholes. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink ;)" loading="lazy" data-shortname=";)" /> Also, this setup for serious track work but not all out track capabilities.</p><p>1. Subframe connector kit - Global West COMP, KB Extreme Matrix or Stifflers FIT system</p><p>2. MM K-Member with oil filter relocation kit (OC-7, required with K-Member)</p><p>3. MM CC Plates</p><p>4. MM Race Spec MM2 Dampers </p><p>5. MM 425/650 Coilover spring kit (this is a perfect compromise for serious track/street)</p><p>6. FTBR FT5001 IRS Kit (this will transform the handling of your car more than you can believe)</p><p>7. FTBR FT1350M Differential Housing (do it now if you plan on any racing activities)</p><p>8. FTBR M4204T31H Torsen T2-R Differential Unit (do it now if you plan on any racing activities)</p><p>9. FTBR FT1860 Toe Link Kit </p><p>10. FTBR FT1900 Rear Sway Bar End Link Kit</p><p>11. MM K-Member non-offset front control arms with Delrin - MMFCA-8, still need the MMFSB-51 kit also</p><p>12. MM front bolt through bumpsteer kit - MMTR-3, required for MM K-Member</p><p>13. MM steering shaft assembly- mmst-14</p><p>14. MM solid steering rack bushings - MMST-6, required for MM K-member</p><p>15. Upgraded front sway bar endlinks</p><p>16. Upgraded urethane front and rear swaybar bushings</p><p>17. Check and replace front inner tie rods, hub assemblies, bearings, etc while the front end is apart.</p><p>18. Check and replace the rear hub assemblies, halfshafts, boots, etc. Based on mileage I found it much easier and cheaper to replace the entire rear knuckle assembly (FTBR FT6800P) with the IRS out. The halfshafts were fine but needed new boots and do not forget new IRS halfshaft retaining nuts, front hub nuts, and IRS camber adjusting bolt plus low profile IRS subframe bolts.</p><p>19. Mathis Bracket, KB Rear Shock Tower brace with additional seam welding on the shock towers, and a MM or KB front strut tower brace. </p><p>20. While everything is out I would install front/rear SS brake lines. </p><p>21. Need to upgrade the braking system, FTBR FT9490HD and FT7000A kits plus appropriate pads, front duct cooling and fluids. </p><p>22. Some serious cooling mods will be required, especially for open tracking. </p><p></p><p>Obviously there are other options regarding suspension choices, tires/wheels, cooling and braking but if you are serious enough to switch to coilovers to improve handling I would go as far as you can based on your budget. Believe me, half assing it in some areas will just lead to frustration. :-D</p></blockquote><p></p>
[QUOTE="Bingo13, post: 14489247, member: 4923"] Wheel Rates for the '03~'04 Cobra with IRS - Front: The front wheel rate is 25% of the stock location spring's rate. For example, the 600lb/in stock location spring has a wheel rate of 150 lb/in. For a coil-over suspension, the wheel rate is approximately 90% of the coil-over spring's rate. Therefore, a front coil-over spring rated at 375 lb/in would result in a wheel rate of about 337.5 lb/in. Your wheel rate will increase by 225%. Rear: The wheel rate for the rear of our Cobra with IRS is approximately 33% of the spring rate in the stock location. For example, the 600 lb/in stock location spring has a wheel rate of 198 lb/in. For a coil-over suspension, the wheel rate is approximately 50% of the coil-over spring rate so a matching 575 lb/in would result in a wheel rate of about 287.5 lb/in. Your wheel rate will increase by 145%. As for the OP question about rates and what to do. I have been using coilovers on this platform since 2002. The archives have a significant amount of information on what a lot of us went through after the car came out and we started open tracking or autocrossing the car. Just a recap based on what I have discovered over the years. Street Setup - Firm yet very good for daily driving, light to medium HPDE/AutoX events and hooks well for spirited starts. Items 1 to 6 are required, the balance are highly recommended (pick and choose based on component age) to get this platform corrected. 1. Full Length Subframe connectors - MM XL, Global West, KB, Griggs, Stifflers. I would actually do the Global West COMP, KB Extreme Matrix or Stifflers FIT system if you do not have FLSC installed already. 2. MM 4-point K-Member Brace (much more important than the upper strut tower brace) 3. MM CC Plates 4. MM Sport Dampers (do not re-valve to be honest, start with a set designed for coilovers) 5. MM 375/575 Coilover spring kit (this is a perfect compromise for what you want) 6. FTBR FT5001 IRS Kit (this will transform the handling of your car more than you can believe) 7. FTBR FT1350M Differential Housing (do it now if you plan on any racing activities) 8. FTBR M4204T31H Torsen T2-R Differential Unit (do it now if you plan on any racing activities) 9. FTBR FT1860 Toe Link Kit 10. FTBR FT1900 Rear Sway Bar End Link Kit 11. MM non-offset front control arms with Urethane - MMFCA-7 12. MM front tapered bumpsteer kit - MMTR-4 13. MM steering shaft assembly mmst-14 14. MM solid steering rack bushings -MMST-7 15. Upgraded front sway bar endlinks 16. Upgraded urethane front and rear swaybar bushings 17. Check and replace front inner tie rods, hub assemblies, bearings, etc while the front end is apart. 18. Check and replace the rear hub assemblies, halfshafts, boots, etc. Based on mileage I found it much easier and cheaper to replace the entire rear knuckle assembly (FTBR FT6800P) with the IRS out. The halfshafts were fine but needed new boots and do not forget new IRS halfshaft retaining nuts, front hub nuts, and IRS camber adjusting bolt plus low profile IRS subframe bolts. 19. While everything is out I would install front/rear SS brake lines. 20. Mathis Bracket, KB Rear Shock Tower brace with additional seam welding on the shock towers, and a MM or KB front strut tower brace would round it out. 21. Upgrade the braking system, FTBR FT9490HD and FT7000A kits plus appropriate pads, front duct cooling and fluids. At the minimum I would do the M-2300-X Cobra R front system and FT7000A rear. But if you get serious do not waste your money on the Cobra R and just go straight to the FTBR FT9490HD fronts. Balanced HPDE/AutoX Setup - Very firm yet streetable for the most part, but beware potholes. ;) Also, this setup for serious track work but not all out track capabilities. 1. Subframe connector kit - Global West COMP, KB Extreme Matrix or Stifflers FIT system 2. MM K-Member with oil filter relocation kit (OC-7, required with K-Member) 3. MM CC Plates 4. MM Race Spec MM2 Dampers 5. MM 425/650 Coilover spring kit (this is a perfect compromise for serious track/street) 6. FTBR FT5001 IRS Kit (this will transform the handling of your car more than you can believe) 7. FTBR FT1350M Differential Housing (do it now if you plan on any racing activities) 8. FTBR M4204T31H Torsen T2-R Differential Unit (do it now if you plan on any racing activities) 9. FTBR FT1860 Toe Link Kit 10. FTBR FT1900 Rear Sway Bar End Link Kit 11. MM K-Member non-offset front control arms with Delrin - MMFCA-8, still need the MMFSB-51 kit also 12. MM front bolt through bumpsteer kit - MMTR-3, required for MM K-Member 13. MM steering shaft assembly- mmst-14 14. MM solid steering rack bushings - MMST-6, required for MM K-member 15. Upgraded front sway bar endlinks 16. Upgraded urethane front and rear swaybar bushings 17. Check and replace front inner tie rods, hub assemblies, bearings, etc while the front end is apart. 18. Check and replace the rear hub assemblies, halfshafts, boots, etc. Based on mileage I found it much easier and cheaper to replace the entire rear knuckle assembly (FTBR FT6800P) with the IRS out. The halfshafts were fine but needed new boots and do not forget new IRS halfshaft retaining nuts, front hub nuts, and IRS camber adjusting bolt plus low profile IRS subframe bolts. 19. Mathis Bracket, KB Rear Shock Tower brace with additional seam welding on the shock towers, and a MM or KB front strut tower brace. 20. While everything is out I would install front/rear SS brake lines. 21. Need to upgrade the braking system, FTBR FT9490HD and FT7000A kits plus appropriate pads, front duct cooling and fluids. 22. Some serious cooling mods will be required, especially for open tracking. Obviously there are other options regarding suspension choices, tires/wheels, cooling and braking but if you are serious enough to switch to coilovers to improve handling I would go as far as you can based on your budget. Believe me, half assing it in some areas will just lead to frustration. :-D [/QUOTE]
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