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Discussion Starter · #1 ·
I know titanium springs are always a big weight saver, but doesn't titanium wear out a lot faster than steel? Any one got the real low down on the possible benefits and drawbacks of a Ti spring? I'm looking into buying the CCDB but I'm not sure whether I would want the Ti or steel spring option.
 

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RobsterCraw said:
I know titanium springs are always a big weight saver, but doesn't titanium wear out a lot faster than steel? Any one got the real low down on the possible benefits and drawbacks of a Ti spring? I'm looking into buying the CCDB but I'm not sure whether I would want the Ti or steel spring option.
Ti also offers better small bump sensitivity.
 

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XSL_WiLL said:
Ti also offers better small bump sensitivity.
Oh BS, who told you that?

Any difference in vibration damping between a titanium and steel spring is so minor that you'd need some extremely expensive equipment to measure it. It is also magnitudes smaller than the damping you are getting from your hydraulic shock.

A 450lb/in spring is a 450 lb/in spring no matter what material it is made from.

As for longevity, it is very hard to call unless you have two specific springs and all the measurements handy.
You can then work out what stress range they work through and work out a rough idea of the fatigue life.

But in general, all springs are highly stressed and will eventually die. Whether your spring will get worked that much depends on many other factors.
 

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This does not answer your question all the way but if it can be tested on a car for 3 years cant be that weak compaired to steel :).
http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/04-5891-1/$FILE/04-5891-1F.pdf?OpenElement
[PDF] Processing and Properties of Allvac Ti-38-644 for Titanium ...File Format: PDF/Adobe Acrobat - View as HTML
suspension springs and reported that Ti-38-644 springs had been used successfully ... The spring and mono-shock assembly that is depicted is currently being ...
doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/04-5891-1/$FILE/04-5891-1F.pdf?OpenElement - <nobr> Similar pages</nobr>
 

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Dougal said:
Oh BS, who told you that?

Any difference in vibration damping between a titanium and steel spring is so minor that you'd need some extremely expensive equipment to measure it. It is also magnitudes smaller than the damping you are getting from your hydraulic shock.

A 450lb/in spring is a 450 lb/in spring no matter what material it is made from.

As for longevity, it is very hard to call unless you have two specific springs and all the measurements handy.
You can then work out what stress range they work through and work out a rough idea of the fatigue life.

But in general, all springs are highly stressed and will eventually die. Whether your spring will get worked that much depends on many other factors.
I was told that since Ti is a more pliable material, it would be more sensitive. Also it takes less coils. But I guess your reasoning makes sense.
 

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Research people!

Dougal is talking out his backside mate.

Titanium is by far the best material for a coiled compression spring currently available. It has a much higher ability than even the best spring steels. Where a bicycle spring is pushing towards the limits of spring design squeezing a lot of travel into a small space with very high spring rates. Titanium is capable of reaching the spring rates we need with less material and less coils, less material and less coils equal more safe travel. Add to this the substantial weight reduction and performance increase with Ti - lighter coils affect the compression-ability and the lighter frequency oscillations within the spring in use are easier for the rebound and compression to control.

Add to this the fact they last longer than steel you are onto a winner!

Dougal,

Please do a bit more research into what you are talking about before you post you comments which can influence peoples spending and possible wastage of money or blocking them from improving their enjoyment of the sport
 

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Jonnyboy said:
Dougal is talking out his backside mate.

Add to this the fact they last longer than steel you are onto a winner!

Dougal,

Please do a bit more research into what you are talking about before you post you comments which can influence peoples spending and possible wastage of money or blocking them from improving their enjoyment of the sport
From your post I can deduce two things.

1. You are involved in selling titanium coil springs.
2. You don't know much (if anything) about metallurgy.

My earlier comments still stand.
 

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Dougal said:
From your post I can deduce two things.

1. You are involved in selling titanium coil springs.
2. You don't know much (if anything) about metallurgy.

My earlier comments still stand.
Although he is correct about the reduced mass moving in the suspension, which could "theoreticaly" make the suspension more active. I will buy that, but not to say it's much of a noticable difference.

Other than that, you are correct. 450lb/in = 450lb/in
 

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you obviously don't know what you are talking about

Well I am not involved in selling ti springs and I have a degree in mechanical and material engineering, so unlike you I am basing my argument on some solid scientific evidence and not just what i think.

You obviously have no concept of how springs work and how the material involved has an effect on that. Let me explain more of the facts.

What is a spring rate?

Spring Rate is defined as the amount of force required to deflect a spring a certain distance. It is typically expressed in lbs/inch. Thus a spring rate of 320 lbs/inch describes a spring that will deflect one inch when 320 lbs of force is applied. Other common units are N/mm and Kg/mm. N(ewton) being the proper metric representation of force and Kg the common but technically incorrect metric units. Rates are converted as 1Kg/mm = 56 lb/in. and 1Kg/mm = 9.86 N/mm.

Do Titanium springs ride differently?

Yes. A titanium spring is more responsive then a steel spring and helps the suspension keep the tires on the ground for better traction and handling. Titanium springs have less mass and thus less inertia. As springs are rapidly compressed the material mass is displaced and generates momentum or inertia based on the product of the velocity and mass involved. In demanding applications this can cause spring surge where the spring coils are moving in the opposite direction of the shock travel. This can disrupt the performance of the suspension system and lower the ability of the suspension to follow the terrain and keep the wheel on the ground. The less mass in the spring, the better performing the suspension will be.

Lower mass systems generate less inertia and accelerate faster allowing better "responsiveness". This allows the suspension to keep the wheel in contact with the ground more resulting in better traction and handling.

What about spring memory?

Many people refer to spring "memory", in fact the proper terminology is "resistance to set." When springs are said to lose their memory or "sack out" the spring has taken a permanent set.

Deflecting a spring results in stresses within the material. The amount of stress is proportional to the deflection imposed. As long as the imposed stress is lower than the yield strength of the material the spring will fully recover its initial length when the load is removed. If the stresses imposed exceed the yield strength of the material the spring will "take set" and will not fully recover its original free length when the load is removed.

It is important to understand that the spring rate is never affected by use. Even when springs take set their rate does not change. To compensate for set, the spring perches must be adjusted or spacers added to replace this lost length. Additionally the available travel of the spring is reduced by any set that it takes.

Properly designed titanium springs utilize the superior material properties to minimize or eliminate set entirely.

What about fatigue life?

The life of the spring to failure, discounting set, is affected by the magnitude and number of deflections that the spring is subjected to in relation to the material properties of tensile strength, ductility and toughness. Remember that steel springs for performance applications are designed "at the limit" to keep weight and size down. With titanium, replacements can be designed where the stresses are "backed-off" just slightly so that typically we can design for twice the life of the steel spring we are replacing. Experience is required of the spring designer to know what levels of stress can be sustained for each type of material used in springs.

If you still don't believe me and are still declaring my statements as witch craft, then go back to basics and compare the two materials:

Titanium

* Tensile Strength:
200,000 psi
(1.27 GPa)
* Density:
.174 lbs/in³
(4.82 g/mm³)
* Elastic Modulus:
5,350,000 psi (36.9 GPa)

Steel

* Tensile
Strength:
250,000 psi
(1.72 GPa)
* Density:
.285 lbs/in³
(7.90 g/mm³)
* Elastic Modulus:
11,500,000 psi
(79.3 GPa)
 

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Jonnyboy said:
Well I am not involved in selling ti springs and I have a degree in mechanical and material engineering, so unlike you I am basing my argument on some solid scientific evidence and not just what i think.

You obviously have no concept of how springs work and how the material involved has an effect on that. Let me explain more of the facts.

What is a spring rate?

Spring Rate is defined as the amount of force required to deflect a spring a certain distance. It is typically expressed in lbs/inch. Thus a spring rate of 320 lbs/inch describes a spring that will deflect one inch when 320 lbs of force is applied. Other common units are N/mm and Kg/mm. N(ewton) being the proper metric representation of force and Kg the common but technically incorrect metric units. Rates are converted as 1Kg/mm = 56 lb/in. and 1Kg/mm = 9.86 N/mm.

Do Titanium springs ride differently?

Yes. A titanium spring is more responsive then a steel spring and helps the suspension keep the tires on the ground for better traction and handling. Titanium springs have less mass and thus less inertia. As springs are rapidly compressed the material mass is displaced and generates momentum or inertia based on the product of the velocity and mass involved. In demanding applications this can cause spring surge where the spring coils are moving in the opposite direction of the shock travel. This can disrupt the performance of the suspension system and lower the ability of the suspension to follow the terrain and keep the wheel on the ground. The less mass in the spring, the better performing the suspension will be.

Lower mass systems generate less inertia and accelerate faster allowing better "responsiveness". This allows the suspension to keep the wheel in contact with the ground more resulting in better traction and handling.

What about spring memory?

Many people refer to spring "memory", in fact the proper terminology is "resistance to set." When springs are said to lose their memory or "sack out" the spring has taken a permanent set.

Deflecting a spring results in stresses within the material. The amount of stress is proportional to the deflection imposed. As long as the imposed stress is lower than the yield strength of the material the spring will fully recover its initial length when the load is removed. If the stresses imposed exceed the yield strength of the material the spring will "take set" and will not fully recover its original free length when the load is removed.

It is important to understand that the spring rate is never affected by use. Even when springs take set their rate does not change. To compensate for set, the spring perches must be adjusted or spacers added to replace this lost length. Additionally the available travel of the spring is reduced by any set that it takes.

Properly designed titanium springs utilize the superior material properties to minimize or eliminate set entirely.

What about fatigue life?

The life of the spring to failure, discounting set, is affected by the magnitude and number of deflections that the spring is subjected to in relation to the material properties of tensile strength, ductility and toughness. Remember that steel springs for performance applications are designed "at the limit" to keep weight and size down. With titanium, replacements can be designed where the stresses are "backed-off" just slightly so that typically we can design for twice the life of the steel spring we are replacing. Experience is required of the spring designer to know what levels of stress can be sustained for each type of material used in springs.

If you still don't believe me and are still declaring my statements as witch craft, then go back to basics and compare the two materials:

Titanium

* Tensile Strength:
200,000 psi
(1.27 GPa)
* Density:
.174 lbs/in³
(4.82 g/mm³)
* Elastic Modulus:
5,350,000 psi (36.9 GPa)

Steel

* Tensile
Strength:
250,000 psi
(1.72 GPa)
* Density:
.285 lbs/in³
(7.90 g/mm³)
* Elastic Modulus:
11,500,000 psi
(79.3 GPa)
Despite all that proof, there still remains one fact. In a high leverage ratio 3:1 system the added mass in the spring sector doesn't make much of a difference. Hardly noticable at best. Reducing mass in the wheel would be many times more effective.

I think what people feel the most out of Ti springs is the reduction in bike weight. That usually has a profound effect on suspension behavior.
 

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IMHO the only advantage of Titanium springs is their weight. Ti might have a slightly greater resistance to fatigue but how many people actually wear out their springs, very few would be my guess. Assuming the same spring rate and design there shouldn't be any difference in small bump compliance.
 

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Jonnyboy said:
Well I am not involved in selling ti springs and I have a degree in mechanical and material engineering, so unlike you I am basing my argument on some solid scientific evidence and not just what i think.

You obviously have no concept of how springs work and how the material involved has an effect on that. Let me explain more of the facts.

What is a spring rate?

Spring Rate is defined as the amount of force required to deflect a spring a certain distance. It is typically expressed in lbs/inch. Thus a spring rate of 320 lbs/inch describes a spring that will deflect one inch when 320 lbs of force is applied. Other common units are N/mm and Kg/mm. N(ewton) being the proper metric representation of force and Kg the common but technically incorrect metric units. Rates are converted as 1Kg/mm = 56 lb/in. and 1Kg/mm = 9.86 N/mm.

Do Titanium springs ride differently?

Yes. A titanium spring is more responsive then a steel spring and helps the suspension keep the tires on the ground for better traction and handling. Titanium springs have less mass and thus less inertia. As springs are rapidly compressed the material mass is displaced and generates momentum or inertia based on the product of the velocity and mass involved. In demanding applications this can cause spring surge where the spring coils are moving in the opposite direction of the shock travel. This can disrupt the performance of the suspension system and lower the ability of the suspension to follow the terrain and keep the wheel on the ground. The less mass in the spring, the better performing the suspension will be.

Lower mass systems generate less inertia and accelerate faster allowing better "responsiveness". This allows the suspension to keep the wheel in contact with the ground more resulting in better traction and handling.

What about spring memory?

Many people refer to spring "memory", in fact the proper terminology is "resistance to set." When springs are said to lose their memory or "sack out" the spring has taken a permanent set.

Deflecting a spring results in stresses within the material. The amount of stress is proportional to the deflection imposed. As long as the imposed stress is lower than the yield strength of the material the spring will fully recover its initial length when the load is removed. If the stresses imposed exceed the yield strength of the material the spring will "take set" and will not fully recover its original free length when the load is removed.

It is important to understand that the spring rate is never affected by use. Even when springs take set their rate does not change. To compensate for set, the spring perches must be adjusted or spacers added to replace this lost length. Additionally the available travel of the spring is reduced by any set that it takes.

Properly designed titanium springs utilize the superior material properties to minimize or eliminate set entirely.

What about fatigue life?

The life of the spring to failure, discounting set, is affected by the magnitude and number of deflections that the spring is subjected to in relation to the material properties of tensile strength, ductility and toughness. Remember that steel springs for performance applications are designed "at the limit" to keep weight and size down. With titanium, replacements can be designed where the stresses are "backed-off" just slightly so that typically we can design for twice the life of the steel spring we are replacing. Experience is required of the spring designer to know what levels of stress can be sustained for each type of material used in springs.

If you still don't believe me and are still declaring my statements as witch craft, then go back to basics and compare the two materials:

Titanium

* Tensile Strength:
200,000 psi
(1.27 GPa)
* Density:
.174 lbs/in³
(4.82 g/mm³)
* Elastic Modulus:
5,350,000 psi (36.9 GPa)

Steel

* Tensile
Strength:
250,000 psi
(1.72 GPa)
* Density:
.285 lbs/in³
(7.90 g/mm³)
* Elastic Modulus:
11,500,000 psi
(79.3 GPa)
I also have an honours degree in mechanical engineering, with as much emphasis on materials and metallurgy as I could pack into it.

There is no "proof" in your comments above. You have simply stated that a titanium spring is more responsive and have no supporting evidence.

The maximum frequency response you get from a suspension system (limited by the systems natural frequency) is magnitudes below the maximum frequency response (again limited by the natural frequency) you get from an unloaded spring.
Hence the natural frequency of an unloaded spring is completely irrelevant (unless you're selling them and need some BS for your marketing department).

Titanium springs have been proven to be the best way to lighten your wallet.
They also have a role to play in lightening a bike, but this pales in comparison to the wallet weight saving mentioned above.

The only fork spring I have ever broken was titanium.

The low modulus of titanium means a larger diameter wire is necessary. This results in rather high surface strain which means any defect on the surface will rapidly cause a fatigue failure.
 

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Those of you claiming Ti is performing better by feel vs steel...your ass-sensitivity level must be legendary! I run Ti because I run Avy shocks (one of the biggest shock bodies out there) and there's a noticeable weight difference when the two springs are off the shock body. But I may need to go back to steel since the coils of a 450# is HUGE and barely fits into my frame. But all in all, when I'm plowing my bike down a hillside, I can't tell if it's made of Ti, steel, or bacon...even that noticeable amount of weight!
 
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