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Triumph cutting coil springs??

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Willie_P

Willie_P

Jedi Hopeful
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Anyone here ever cut their stock springs?

I was reading an old Classic Motorsports article wherein the author purchased performance road springs from TSI for their project TR3 (if I recall correctly), with a free length of 10" and then cut them further to get the car lower.

I was observing my stock springs last night (TR4) and they have a current free length of 10", but have factory "flattened" ends on each end, which I am sure assist in centering the spring on the upper mounting cup and lower pan.

I am worried that by removing the flattened end and only having a raw "nub" the spring will rest crooked or have forces transferred into it at an odd angle.

I am certainly aware of all the controversy regarding cutting springs.

Any comments from the forum members?

I guess the bottom line question is: how do I lower my car 1.5" to 2" in the front. (I am also prepared to make all appropriate suspension changes to address bump steer, etc).

Thanks, willie
 
well if you cut the spring you could take a side grinder and grind the spring as to replicat how the flat end, as far as cutting and shortening a spring and what it does, I have no clue but I did it on a car back in college

Hondo
 
Cut the springs on my 73 Capri.
Years ago.
 
The problem with cutting springs is determining how much to cut. 1 inch may not translate to a 1 inch drop in ride height. Also your spring rate will increase resulting in a stiffer ride. How much stiffer is unknown.
Racers use MGB springs and a Google may find the correct year etc. I don't know the details.
If in Pittsburgh do you belong to the WPTA? If not you should as there is a wealth on knowledge at your disposal.
JVV
 
I lowered my TR3 race car front springs by putting blocks under the frame with an open space for the amount I wanted to lower the car, and then heated the last coil of the springs with a torch until the frame touched the blocks. I know there will be sharp intakes of breath over my doing it this way, but it worked and I raced that 3 for several years with no problems. Yes the spring rate was increased, but I was looking for that, too.
 
I shortened the springs of my Spitire that way. Warmed up the final coil with a torch while it was in the press. The final coil flattened down against the next one. Wrap the whole thing in fiberglass and let it cool slowly.

An abrasive cut off wheel will give you the nice flat end.
 
Now that's a neat solution but I wonder if the spring rate really changed? Same number of coils in my opinion relates to the same spring rate. The issue becomes spring binding however as at least some of the coils are closer together. There is a write up somewhere that says a spring can be compressed and heated to 450 degrees for a half hour and when cooled it will stay at the compressed length but not affect the spring rate because the number of coils are the same. Have not tried that but I am considering trying it as I'd like a lower overall ride height but the same rate. The write up cautions that spring binding could occur.
 
I would be worried about getting equal compression if I did it by heating the spring, also if done on the car I am pretty sure I would melt the spring pad, if off the car even more concerned about getting the sides equal, but I have been contemplating cutting or otherwise doing something to lower my front end, I started to work on lowering the spring pads of the lower a-arm 3/4" or 1/2" inch or so with spacers (TR4A-250-6 front suspension), but ran into some issues and needed to get the car back on the road, so quit, but think I could do it, anybody else tried this (not sure if it would work on the earlier TR suspension).
 
I wasn't so much concerned with the spring rate as getting the nose back down where it belonged.
 
The preffered method is called "bulldozing" to lower a car. A spring shop puts the spring on a huge press and smashes it down so the resting height is lower to start, which lowers the ride height. That way the rate stays the same.

Cuttting a coil works, but as mentioned, it stiffens the ride. That could be a good or bad thing, depending on what your goal is. Sometimes the extra stiffness is needed since you have less travel after cutting the coil. It helps keep from having the suspension bottom out.

Heat treating springs is pretty envolved. The springs we have are coiled and then heat treated. Finally they shot peen them for fatigue resistence. Any heat you put on it to make it glow will ruin both the heat treating and shot peening affects...and unfortunately, a torch will ruin the heat treatment in a localized and unpredictable way.

John
 
Hi Willie,

What about having the front spring spacers machined down to lower/level the ride height?

Cheers,
M. Pied Lourd
 
Hey @JerryVV:

FYI...this is the TR4 I bought from you and ED W. about 6-7 years ago. I was over Ed's on Sunday looking for a 5/8 reamer for the new suspension bushings up front.

as an update, my goal is to have a fully restored rolling chassis by PVGP time.

-wes
 
It's not rocket science. Figuring out the new spring rate is simple coil spring math. Figuring out how far the car will lower as a result of cutting X amount is also simple math.

Done it a number of times myself over the years. No big deal.

Trying to flatten the end, that's a pain. It's usually not successful and not necessary anyhow. Don't waste your time on it.
 
@foxtrapper:

I am terrible at math (kidding aside), if I wanted to lower the car 2" in front, how much would I have to cut out of an uncompressed spring?

I am well aware of the spring rate issue and have no problems with that given that I am pairing this with 20% uprated shocks.

thanks for the help, I do respect all opinions and advice offered here.

wes
 
2"" . Yikes ,that's a lot. Is this a race car??
 
If you've got a jack, you can avoid all the math.

Measure the length of the spring with the car sitting on its wheels. Now jack the car an inch and measure the spring again. That's the amount the spring changes for 1 inch ride height change. Double that and it's the amount for a 2 inch ride height change. That also means it's the amount you want to shorten the spring to lower ride height by 2 inches.

This is rough and crude, and yes changing angles make a difference, but it's pretty small. You'll be in the pretty close ballpark.

Lets say it's exactly 1" spring length change to 2" of car height change. This would mean you would shorten the spring 1" to drop the car 2".

So where do you actually cut?

With the car sitting on its tires, you pick an end of the coil spring, and look to see where the bottom of the wire just starts to come off the perch (you see light on both sides of the wire). That's where the spring action is actually starting. It's known as a free coil.

Follow the coil around until it rises 1". That section is what you want to remove. It will shorten the spring 1", and lower the car 2" in this example.

Caviat #1. You can always cut more, you cannot put a coil back in. So work your way up to the full cut.

Caviat #2. I did not include the amount of the newly cut spring that will sit flat against the coil, not being free. This is generally between 1/2 to 1/1 of a coil wrap. Take that into account, especially with caviat #1.
 
@foxtrapper:

that is very kind of you and extremely helpful. however, you forgot caveat #3: my car is completely disassembled and all I have are free springs.
 
foxtrapper said:
Caviat #1. You can always cut more, you cannot put a coil back in. So work your way up to the full cut.
Click to expand...
That's quite true, but you can add back a bit of ride height, by adding a spacer under the spring.

Also as already mentioned, don't forget that the original travel was pretty limited. Unless you also modify the bump stop and so on, lowering by 2" will have your suspension almost sitting on the stop.

I only machined 1/4" out of the spacer (to lower by about 1/2 - 3/4") and I hit the stop a lot more often than I did before making the change.

Another option is to turn the A-arms over. I haven't measured, but I think that should lower by 1" or more without affecting travel. Of course there are a few other modifications required.
 
alternative thought:

My car came with the aluminum spacers (I think the manual refers to them as "packing"); what if I did not cut the springs at all and instead just did not run the alloy spacers?

thought being that I'd find out about ride height and bumpstop issues, but have the ability to return to stock height if not satisfied (simply by replacing the alloy spacers).

anyone see any problem with this?
 
I would vote spacers...I'm like the others, in that I don't think you'll be happy after taking 2" out of the ride height...


...or, you could always lower the profile of your tires to keep the suspension travel the same. (but then the discussion will turn to your speedometer!?!)

John
 
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